DE4410787A1 - Polishing method and polishing device - Google Patents

Abstract

The invention provides a polishing method which comprises the steps of forming a film to be polished on a substrate which has a recessed section in its surface, in order thus to fill at least the recssed section, and the selective leaving of the film to be polished in the recessed section by polishing the film with the use of a polishing agent which contains polishing particles and a solvent and has a pH value of 7.5 or more. The invention furthermore provides a polishing device which has a polishing-agent storage container (87) for storing a polishing agent, a turntable (84) for polishing an object to be polished, a polishing-agent supply tube (89) for supplying the polishing agent from the polishing-agent storage container (87) onto the turntable (84), a polishing-object clamping device (81) for holding the object to be polished, so that that surface of the object which is to be polished lies opposite the turntable (84), and a polishing-agent supply-tube temperature-setting unit (92) which is connected to the polishing-agent supply tube (89), in order to set the temperature of the polishing agent. <IMAGE>

Description

The present invention relates to a polishing method as Semiconductor manufacturing technique and apparatus for Implementation of the method, and in particular concerns a Polishing method and a polishing apparatus for conductor films.

For some time, many have become large-scale integrated circuits (LSIs) by integrating a large number of transistors for example and Resistors are formed on a single chip in the Main parts of computers and communication systems used. Because of this, the performance depends on one Overall system of this kind is significantly different from the performance of one individual LSI. With increased packing density of the LSIs were developed different micro-pattern method. The minimum Processing size of samples was reduced year by year and currently has the order of magnitude in the submicrometer range reached. A CMP process (Chemical Mechanical Polishing: Chemical-mechanical polishing) represents one of the methods that have been developed to meet these stringent requirements regarding miniaturization. This method  is essential in the implementation of for example the Leveling of insulating intermediate layers, the formation of Plugs, the formation of buried metal Connecting lines, or isolating buried elements in semiconductor device manufacturing operations.

Figs. 1 to 1G are sectional views showing an example of forming buried metal interconnections using a conventional polishing method. In these drawings, only metallic connecting lines are shown, and all other structures such as elements below an insulating film 2 are omitted. First, as shown in FIG. 1A, the insulating film 2 is formed on a semiconductor substrate 1 such as a silicon substrate, and then the surface of the film 2 is flattened. Thereafter, as shown in Fig. 1B, trenches for intermediate connection lines or openings for connection lines are formed in the insulating film 2 using conventional photolithographic and etching processes. Then, as shown in FIG. 1C, an interconnection metal film 3 having a thickness larger than the depth of the trenches provided in the insulating film 2 is formed. In this case, in order to prevent mutual fusion or reaction between the insulating film 2 and the interconnector metal film 3 , a metal barrier film may also be provided between these parts.

Then, in order to leave the intermediate connection metal film 3 only in the trenches or the openings, polishing is performed on the film 3 , using alumina particles or the like as the polishing particles. In this case, a film consisting of a substance having a high polishing speed selectivity with respect to the interconnect metal film may be formed as a polish-resistant film either above or below the film 3 .

Thereafter, as described in the methods invented by Wada et al (Japanese Patent Application Nos. 4-065781, 4-212380, 4-269202, and 5-67410), a heat treatment is carried out continuously in a vacuum, starting from state shown in Fig. 1C, (where no gap is formed) by using an Al film whereby a single crystal Al is formed in the trenches as an intermediate compound metal film, and at the same time selectively the Al film on projecting portions on the insulating film 2 remains as shown in Fig. 1. Thereafter, as shown in Fig. 1, the remaining Al film is removed by polishing.

As is apparent from Fig. 1E, the ideal shape after polishing is such that the interconnect metal film 3 is left only in the trenches, metal interconnects (interconnect lines) are formed on the surface without defects, and the interconnect metal film 3 is formed at all is not present on the projecting portions, and the surface of the insulating film 2 is at the same level as the surface of the inter-connecting metal film 3 .

However, in actual polishing operations, the surface of the interconnect metal film 3 to be polished is damaged and roughened by a mechanical action between the surface of the metal film and polishing particles, or between the surface and a pad for holding a polishing agent, or polishing particles in the intermediate Connection metal film 3 buried or left on this back. In addition, as shown in Fig. 1F, a phenomenon called dishing occurs, in which the thickness of a central portion decreases, particularly in a wide range of the interconnect metal film 3 buried in the trenches or openings. This tendency becomes particularly remarkable when a metal of low hardness and high ductility, for example, Al or Cu, is used as the material for the interconnection metal film 3 . The occurrence of defects or inward curvature, or remnants of polishing particles on the surface of an interconnect metal film, increase the resistance of the resulting interconnect lines or cause disruptions, leading to a reduction in reliability or product yield.

An example of a polishing method which can prevent the occurrence of defects or inward curvatures on the surface of an interconnect metal film is when a film to be polished is an Al film in a treatment using a slurry obtained by dispersing alumina particles in an aqueous acidic solution having a pH of 3 or less (Beyer et al, U.S. Patent No. 4,944,836). However, in this type of polishing, the polishing rate ratio (SiO ₂ / Al) of SiO ₂ to Al can not be satisfactorily reduced. Therefore, when this polishing method is employed in the fabrication of buried interconnecting lines, the SiO ₂ film (insulating film 2 ) is also polished at the same time when the Al film (interconnect metal film 3 ) is polished. This reduces the depth of trenches formed in the SiO ₂ film, resulting in reduced dimensions of interconnects. In addition, this polishing method involves another problem, namely, the corrosion of a polishing apparatus due to the use of the aqueous acidic solution.

On the other hand, a method using no polishing particles has been reported (International Electron Devices Meeting Technical Digest 1992, p. 976, Y. Hayashi et al.) In which aluminum plugs are prepared by polishing using a mixed solution of an amine and hydrogen peroxide water. Since no polishing particles are used, polishing is almost chemical in this method, and hardly any defects or roughness occur in aluminum. However, there is a significant inward curvature since the ratio (polishing rate / dissolution rate) of the polishing rate of aluminum to the dissolution rate of aluminum with respect to the solution mixture is low. For example, when this polishing method is performed on a sample in the state shown in Fig. 1D, the Al film (interconnect metal film 3 ) formed in the trenches disappears to serve as interconnections before the Al film is removed which remains on the projecting portions as shown in Fig. 1D.

The present invention has been made in consideration of developed situations described above, and her The aim is to provide a polishing process and a polishing apparatus, which is a polishing process but the occurrence of errors (Roughness) and inward curvatures on the surface of a Suppress interconnection to such an extent can, that in practice no difficulties occur.

The present invention provides a polishing method Available, which has the following steps: training  a film to be polished on a substrate, which in its surface has a recessed portion to so at least to fill the gutted section, and selectively leaving the film to be polished in the recessed section by polishing the film below Using a polishing solution, which polishing particles and a Contains solvent, and a pH of 7.5 or more having.

In addition, the present invention ceases Polishing method available with the following steps: Forming a film to be polished on a substrate, which in one of its surfaces a recessed Section to at least the recessed section to fill; and selectively leaving the object to be polished Films in the recessed section by polishing the film using a polishing agent, which is a solution to the Etching of the film to be polished contains a Corrosion prevention agent for the film to be polished, as well as polishing particles.

The present invention further provides a Polishing device available, which is a polish- Storage container for storing a polishing agent, a turntable for polishing an object to be polished, a polishing agent supply pipe for supplying the polishing agent from the polish storage container to the turntable, a polishing object jig for holding one polishing object in such a way that the to be polished Surface of the object facing the turntable, and a polishing agent supply tube temperature adjuster, which is connected to the polishing agent supply pipe to the Adjust the temperature of the polishing agent.  

The invention will be described below with reference to the drawing illustrated embodiments explained in more detail, from which further benefits and features emerge. The goals and advantages of the invention can be achieved by the measures and combinations, particularly in the attached claims are given.

The accompanying drawings, which are incorporated in the description are included and form part of the description, illustrate currently preferred embodiments of the Invention, and serve to explain the basics of Invention, together with the foregoing, general Description and detailed description of the preferred embodiments. It shows:

Figs. 1A to 1G are sectional views for explaining the conventional polishing;

FIG. 2 is a schematic view of an example of a polishing apparatus used in a polishing method according to Embodiments 1 to 3; FIG.

Fig. 3 is a sectional view for explaining an example of the polishing method of Embodiment 1;

Fig. 4 is a graph showing the relationship between the particle size of polishing particles and the maximum surface roughness of an Al film;

Fig. 5 is a graph showing the relationship between the pH of a polishing solution and the maximum surface roughness;

Fig. 6 is a view for explaining the definition of a specific resistance;

Fig. 7 is a graph showing the relationship between the resistivity and the maximum surface roughness for different line widths;

8A to 8C are sectional views showing a diagram for states polished surfaces at different pH values of a polishing solution.

Fig. 9 is a graph showing the relationship between the dissolution rate and the pH for different average particle sizes of polishing particles;

10 is a graph with a representation of the relationship between the polishing rate and the pH for different average particle sizes of polishing.

Fig. 11 is a graph showing the relationship between the polishing speed and the average particle size of polishing particles for Al, TiN, SiO ₂ and C;

12A and 12B are sectional views for explaining another example of the polishing method according to Embodiment 1; Fig.

Fig. 13 is a sectional view for explaining an example of a polishing method of Embodiment 2;

Figs. 14 to 17C are sectional views for explaining other examples of the polishing method of Embodiment 2;

Figs. 18A and 18B are sectional views for explaining the lower limit of the ratio of the average particle size of polishing particles to the thickness of a polishing-resistant film;

Fig. 19 is a sectional view showing an example of an object to be polished with the polishing method of Embodiment 3;

Figs. 20A to 20C are sectional views for explaining manufacturing steps in the polishing method of the embodiment 3;

Fig. 21 is a graph showing the relationship between the ratio of the average particle size of polishing particles to the thickness of a polishing-resistant film and the number of remaining polishing particles;

Figure 22, 26 and 28 are sectional views with a presentation of further examples of the object to be polished with the polishing method according to Embodiment 3; FIG.

Fig. 23 is a sectional view for explaining the extent of an inward curvature;

Fig. 24 is a graph showing the relationship between the amount of inward curvature and the polishing time;

Fig. 25 is a graph showing the relationship between the degree of inward curvature and the average particle size of polishing particles;

Figs. 27A to 27C and 29A to 29C are sectional views for explaining other examples of the polishing method of Embodiment 3;

FIG. 30 is a schematic view showing an example of a polishing apparatus according to Embodiment 4; FIG.

Fig. 31 is a sectional view showing an example of an object to be polished used in carrying out polishing by using the polishing apparatus of Fig. 4;

Figs. 32, 35, 38 and 40 are graphs each showing the relationship between the amount of inward curvature and the polishing surface temperature;

Figs. 33, 36, 39 and 41 are graphs each showing the relationship between the maximum surface roughness and the polishing surface temperature;

Fig. 34 is a sectional view showing another example of the object to be polished which is used in carrying out polishing using the polishing apparatus according to the third embodiment of the present invention; and

Fig. 37 is a schematic view showing another example of the polishing apparatus according to Embodiment 4.

The inventors pay attention to the relationships between the average particle size of polishing particles and the Occurrence of errors or inward curvatures on one too polishing object, and on the relationship between the pH Value of a polishing solution and the occurrence of errors or Directed inward curvatures, and found that polishing a polishing object performed can be, without errors and inward curvatures by the mean particle size of Polierteilchen and the pH of a polishing solution within respective predetermined areas.

The embodiments of the present invention will be with reference to the accompanying drawings explained.

Embodiment 1

Fig. 2 is a schematic view showing an example of a polishing apparatus used in a polishing method according to the present invention. This polishing apparatus has a rotary polishing table 14 , a polishing pad 13 fixed to the polishing table 14 , a rotatable sample holder 11 disposed above the polishing table 14 , and a polishing solution supply tube 15 connected to a polishing solution container. The inlet opening of the tube 15 extends to a portion close to the polishing pad 13 . An object to be polished 12 is clamped by means of vacuum on the sample holder 11 so that its surface to be polished is opposite the polishing pad 13 . A polishing solution 16 is supplied to the polishing pad 13 through the polishing solution supply pipe 15 . The supplied amount of solution 16 can be controlled to a predetermined value.

In the present embodiment, materials having different hardnesses (Shore hardnesses of 66 to 88) and composed of different substances (polyurethane foam, plush polyurethane foam, non-woven fabric, and resin-impregnated non-woven fabric) were used to form the polishing pad 13 , Each resultant polishing pad was used to polish an object to be polished (Al film), and the occurrence of defects on the object was checked. As a result, when plush polyurethane foam was used as the material, no defects of 5 nm or more in depth appeared on the surface of the object to be polished, regardless of the hardness. Therefore, the plush polyurethane foam turned out to be the best material for the polishing pad. Therefore, in the present embodiment, this material was used as the polishing pad 13 .

The polishing agent used was a colloidal solution prepared by dispersing SiO ₂ particles in a dilute solution of piperazine (C ₄ H ₁₀ N ₂ ). In the present embodiment, various polishing solutions were prepared by changing the average particle size of the SiO ₂ particles as polishing particles in the polishing solution by changing the ratio of the SiO ₂ particles within the range of 50% by weight or less. The pH of each polishing solution was adjusted by controlling the amine concentration.

Fig. 3 is a sectional view showing the object to be polished used in the present embodiment. In Fig. 3, reference numeral 21 denotes a silicon substrate. On this silicon substrate 21 , a SiO ₂ film 22 is produced. In the SiO ₂ film 22 trenches are formed, each having a width of 0.5 to 10 microns and a depth of 0.4 microns to form interconnections. On the entire surface of the SiO ₂ film 22 provided with these trenches, a 50 nm-thick carbon film 23 as a polishing-resistant film is produced by using a DC magnetron sputtering process. On the carbon film 23 , a polycrystalline Al film 24 is formed by DC magnetron sputtering. After being prepared in a vacuum without heating, this polycrystalline Al film 24 is continuously heat-treated in a vacuum. Therefore, the polycrystalline aluminum flocculates (coagulates) and is buried in the trenches to form a single crystal of aluminum. In this case, a polycrystalline Al film 24a as part of the Al film is not buried in the trenches even after flocculation, but remains in the form of a single crystal in a wide range except for the trenches.

On the resulting object to be polished, a polishing process (CMP) was performed to remove the Al film 24 a remaining on the areas other than the trenches. Fig. 4 is a graph showing the relationship between the particle size of the polishing particles and the maximum surface roughness R _{max of} the Al film 24 in this polishing process. In Fig. 4, the particle size on the abscissa means the maximum diameter of the polishing particles contained in the polishing agent. Fig. 5 is a graph showing the relationship between the pH of the polishing solution and the maximum surface roughness R _max . It should be noted that the results shown in Figs. 4 and 5 were obtained by carrying out the polishing operation by setting the polishing pressure at 300 g / cm ² and the rotational speeds of the sample holder 11 and the polishing table 14 at 100 revolutions per minute ,

In Fig. 4, the maximum surface roughness R _{max is} 20 nm when the particle size is 100 nm and the pH is 7.5, and when the particle size is 150 nm and the pH is 14. It can be seen from FIG. 4 that as the particle size of the polishing particles decreases, so does the maximum surface roughness R _max . This is because voids on the surface of aluminum are generated by a mechanical action between the aluminum and the polishing particles. Further, Fig. 4 shows that the slopes of the curves are reduced as the particle size of the polishing particles decreases. In particular, when the pH of the polishing solution is 7.5 or higher, the maximum surface roughness R _{max is} almost constant when the particle size of the polishing particles is about 10 nm. The reason for this is considered to be that the polishing particles easily flocculate as the particle size of the polishing particles decreases. It is therefore believed that even if the particle sizes of individual polishing particles are small, these small polishing particles are flocculated to form large particles, and these large particles are involved in the actual polishing process.

On the other hand, Fig. 5 shows that the maximum surface roughness R _max decreases as the pH of the polishing solution increases. The maximum surface roughness R _max abruptly decreases, in particular, when the pH of the polishing solution is between 7 and 7.5. It is believed that the reason for this is the following. Aluminum generally has the property of forming a passivation film such as an oxide film on its surface when it is in an aqueous solution. This passive film is stable in a pH range between 4 and 7.5 and may well serve as a barrier to protecting aluminum in this pH range. However, in a solution of greater than pH 7.5, a sudden deterioration of the performance of the passive film as a barrier occurs, resulting in a solution of aluminum. Taking into account these properties of aluminum, it may be considered that the maximum surface roughness _Rmax undergoes a sudden change around pH 7.5, since a chemical action with respect to aluminum abruptly nears a pH of 7.5 increases.

Further, it has been found that, with a value of the polishing pressure of 300 g / cm ² or more, the maximum surface roughness R _{max increased} almost in proportion to the increase of the polishing pressure. When the polishing pressure was lower than 300 g / cm ² , almost a saturation value for the maximum surface roughness R _{max was found} . For example, when the polishing pressure had a value of 30 g / cm ² , the value of the maximum surface roughness R _{max was} about 90 to 100% of the value when the polishing pressure was 300 g / cm ² . No significant change occurred in the maximum surface roughness R _max when the rotational speeds of the sample holder 11 and the polishing table 14 were in the range of 50 to 500 revolutions per minute.

It is apparent from Figs. 4 and 5 that when polishing the Al film 24 at least under the conditions that the particle size of the polishing particles is 100 nm or less and the pH of the polishing solution is 7.5 or more, the maximum Surface roughness R _max can be reduced to 20 nm or less, with no problems in practice. It should be noted that even if these conditions are not satisfied, the maximum surface roughness R _max can be reduced to 20 nm or less, provided that the pH of the polishing solution is 7.5 or higher. Further, from FIGS. 4 and 5 show that R _max is 20 nm, when the pH value of 7.0 and the particle size is 5 nm, and when the pH is 7.5, and the particle size 100 This shows that when the pH of the polishing solution is in a range of 7.0 to 7.5, the maximum surface roughness can be reduced to 20 nm or less when the particle size of the polishing particles is reduced accordingly. Therefore, the polishing is preferably carried out with a particle size resulting on and below a line smoothly connecting a point at which the pH of the polishing solution is 7.5 and the particle size is 5 nm to a point at which the pH 7.5 and the particle size is 10 nm, in Fig. 4. However, when the problem of inward curvature is considered, a particle size of 100 nm or less and a pH of the polishing solution of 7.5 or more are Polishing conditions rather prefer.

In the practice of manufacturing LSI interconnects, it is very important that the maximum surface roughness R _{max be} 20 nm or less. Fig. 7 shows curves of the relationship between the maximum surface roughness _Rmax and the specific resistance ρ for line widths of 0.2, 0.4 and 1.0 μm. This specific resistance differs from a conventionally defined constant, which is determined by the nature and structure of a substance. The definition of resistivity used in the present case will be explained below with reference to FIG . As is apparent from Fig. 6, the specific resistance of an Al interconnect 25 (solid line) on the polished surface on which a defect is formed is calculated by assuming that this Al interconnect 25 has the same sectional area as one Al interconnect 25 a (dashed line), which has no errors. In general, the resistivity ρ is represented by ρ = R · S / L, assuming that the length of an interconnect is L, its sectional area S, and its resistance R. In the graph shown in FIG a certain line width is plotted on the basis of the measured value of the resistance R with respect to the maximum surface roughness R _max , while S and L have fixed values. As is apparent from Fig. 7, the resistivity ρ for a sub-micron line width abruptly increases from a maximum surface roughness R _max of 20 nm. The rate of increase increases as the line width decreases. When an interconnection having a line width of, for example, 0.2 μm is to be manufactured in a practical LSI interconnection, an error having a depth of 20 nm or more substantially increases the resistivity, resulting in a substantial reduction in the performance and reliability of the device leads. The reduction of the maximum surface roughness R _max to 20 nm or less is therefore extremely important in the practice of fabricating LSI interconnects.

Figs. 8A to 8C are sectional views showing the surface states of the object to be polished shown in Fig. 3 when the pH of the polishing solution is changed between 7 and 13. Specifically, Figs. 8A to 8C each show the surface of the polished object under the above-described conditions observed using an optical microscope and a scanning electron microscope (SEM). It should be noted that the polishing pressure, the revolution speed and the polishing time were kept constant for all the pH values. As shown in Fig. 8A, when the pH of the polishing solution was 7, a large number of defects were observed on the surface of the Al film 24 . It is believed that this is because there was virtually no chemical reaction. When the pH of the polishing solution 10 was high, as shown in Fig. 8B, no voids were formed on the surface of the Al film 24 , and no reduction in the film thickness was found. When the pH of the polishing solution 13 was as shown in Fig. 8C, no defects were observed on the surface of the Al film 24 . However, in this case, the film thickness decreased significantly due to a strong inward curvature. Therefore, when the pH of the polishing solution was increased to increase the chemical action, the effect of the inward curvature became more pronounced.

In order to suppress the inward curvature that occurs significantly as the pH of the polishing solution is increased, it is necessary to increase the ratio (V _P / V _E ) of the polishing speed V _{P of} the aluminum to the dissolution rate V _E of aluminum with respect to the polishing agent to increase. In general, projecting portions on the surface of aluminum to be polished are easily influenced by the mechanical action of the polishing particles caught by the polishing pad attached to the polishing table 14 , and are also liable to be affected by the chemical action since every moment new surfaces are exposed to the polishing agent. The projecting sections therefore have both mechanical and chemical effects. In contrast, recessed portions are hardly affected by the mechanical action, and are only isotropically etched by the chemical component of the polishing agent. It can therefore be assumed that the recessed sections are subject to only a chemical action. Therefore, to reduce the inward curvature, it is particularly desirable that the dissolution rate V _E of aluminum with respect to the polishing agent be 0 nm / min in the recessed portions.

Fig. 9 is a graph showing the relationship between the pH of the polishing solution and the dissolution rate. In Fig. 9, a solid line indicates an aqueous amine polishing solution containing no polishing particles (SiO ₂ ), and each dashed line indicates a polishing solution prepared by dispersing polishing particles in an aqueous amine solution. Fig. 10 is a graph showing the relationship between the pH of the polishing solution and the polishing speed V _P. As shown in Fig. 9, when the polishing particles are dispersed in the aqueous amine solution, the dissolution rate V _E abruptly decreases. In particular, when the particle size Φ of the polishing particles is 100 nm or less, the dissolution rate V _{E is} stable at 2 nm / min or less. In addition, as shown in Fig. 10, the polishing speed V _P increases in proportion to the particle size Φ and the pH value. However, when the particle size Φ becomes 100 nm or larger, the increase in the polishing speed with respect to the increase in the particle size Φ becomes small.

In polishing the object to be polished shown in Fig. 3, for practical considerations, the value of V _P / V _{E must be} 90 or more. This is because the height of the Al film 24a as a protruding portion is generally between 1 and 1.8 μm, whereas an allowable inward curvature amount of the Al film 24 as an interconnector must be 20 nm or less to increase the resistance or to prevent a decrease in reliability (for example, an electromigration resistance). Considering this aspect, the range for the particle size of the polishing particles and the pH range of the polishing solution in which a maximum surface roughness R _max of 20 nm or can be obtained less, and a value of V _P / V _E of 90 or more.

As shown in Fig. 9, the dissolution rate is V _E 2 (pH = 7.5) to 2.4 (pH = 14) when the particle size is 100 nm and the pH is 7.5 to 14. In addition As shown in Fig. 10, the polishing speed V _P is 180 (pH = 7.5) to 220 (pH = 14) when the particle size is 100 nm and the pH is 7.5 to 14. Therefore, the value for V _P / V _E 90 or more when the particle size is 100 nm and the pH is 7.5 to 14. It is known that the rate of increase of the rate of dissolution V _E with respect to the particle size is higher than that of the polishing rate V _P (ΔV _E <ΔV _P ) at any value in the pH range of 7.5 to 14. Therefore, if the particle size is larger than 100 nm, the value of V _P / V _E becomes within the pH range from 7.5 to 14 lower than 90, so that proper polishing can not be performed. Therefore, in order to reduce the maximum surface roughness R _max to 20 nm or less and increase the value of V _P / V _E to 90 or more, it is preferable to set the particle size of the polishing particles to 100 nm or less, and to adjust the pH of the polishing particles. Value of the polishing solution to 7.5 or more. Among the currently available polishing agents, those with the greatest particle size accuracy have a ± 5% variation for a particle size of, for example, 100 nm. Therefore, although the particle size is set to be 100 nm or less, an error (95 to 105 nm) for the particle size must be taken into account as a true value. Further, Figs. 9 and 10 show the results obtained when the weight ratio of the polishing particles with respect to the entire polishing agent was 5%. If the weight ratio is higher than 5%, for example, 10 to 30% as in actual polishing, the number of polishing particles per unit area increases, so that even inward curvature is suppressed.

The inventors performed polishing operations in the same manner as described above using an object to be polished which was produced by omitting the carbon film 23 from the arrangement shown in Fig. 3, and found the following. There was no problem although the polishing process was slightly transferred to the underlying SiO ₂ film 22 due to the absence of the carbon film 23 . In this case, however, the polishing amounts for both Al and SiO _{2 must be set} to certain appropriate values since the polishing speed for the SiO ₂ film is higher than that for the polishing-resistant film made of carbon, for example. This can be done even if the object to be polished does not have a polishing-resistant film, but in this case, the polishing conditions must be strictly determined. In fact, when the polishing rates of Al, carbon and SiO ₂ were compared at a pH of 11, as shown in Fig. 11, it was found that carbon as a material for the polishing-resistant film is better than SiO ₂ . However, if a polishing solution having KHO or NaOH as a pH adjusting agent is used, the polishing rate of SiO _{2 increases} to 100 nm / min or more, and this further reduces the selectivity of Al to SiO ₂ . Therefore, a polishing-resistant film such as the carbon film 23 is required. It is also possible to use, instead of the carbon film 23, a film consisting of TiN, ZrN, HfN, TaN, VN, NbN or TiW as a polishing resistance film against polishing of aluminum.

FIGS. 12A and 12B are sectional views for explaining the manufacturing steps in another embodiment of the polishing method according to Embodiment 1 . First, a SiO ₂ film 32 was formed on a silicon substrate 31 , as shown in Fig. 12A. Then, a 50 nm-thick carbon film 34 was produced on the entire surface of the SiO ₂ film 32 by DC magnetron sputtering. Thereafter, trenches for forming interconnections were prepared by a normal photolithographic process. Thereafter, an Al film 33 was formed on the entire surface by DC magnetron sputtering. This Al film 33 was made to have a thickness of 450 nm, which was more than the thickness of the steps of the SiO ₂ film 32 . Then, as shown in Fig. 12B, polishing of the Al film 33 was performed so that the Al film 33 was left only in the trenches. As described above, this polishing was carried out so that the particle size of the polishing particles was set to 100 nm or less, and the pH of a polishing solution to 7.5 or more. In addition, the polishing solution and the polishing apparatus were the same as the above solution.

When the polished surface was observed after polishing using an optical microscope and an SEM, it was found that the Al film 33 was completely removed in an area other than the trenches. In addition, neither flaws nor surface roughness caused by the polishing process appeared on the surface of the Al film 33 remaining in the trenches. Further, it was found by the sectional observation with SEM that practically no reduction in the film thickness of the Al film 33 in the trenches was caused, so that no inward curvature occurred. In the above embodiment, a polishing solution composed of colloidal silica prepared by dispersing SiO ₂ particles as polishing particles in an aqueous piperazine solution was used. However, it was found that, particularly for silica particles, the abrupt decrease in Al dissolution rate which occurred when the polishing particles were added to an aqueous alkaline solution was conspicuous. Furthermore, it was found that, although the dissolution rate in practice decreased by a certain level, no such abrupt change occurred for particles of, for example, cerium oxide, titanium oxide and alumina as in the case of silica particles. Therefore, particles of these substances are also usable.

The mechanism for these phenomena can be considered as follows. When silica particles are dispersed in an aqueous alkaline solution as in the present embodiment, the surface of each silica particle is negatively charged. Therefore, the silica particles are attracted to the surface of the aluminum by a local anode, thereby forming an electric double layer. This therefore reduces the dissolution of aluminum. Silica ions such as SiO ₄ ^4- ions or (SiO ₃ ) _n ^m- (m, n: integers), for example, (SiO ₃ ^2- ) n ions are formed as negative ions by reaction of the silica particles with the aqueous alkaline solution , The dissolution of aluminum is suppressed by absorbing the negative ions at a local anode in an aluminum surface. Therefore, the silica particles serve as a corrosion preventing agent for aluminum. For this reason, the alkaline silica dispersion of the present invention can polish Al without causing voids and inward curvatures. For example, when Al was polished with a polishing agent prepared by dispersing alumina particles (50 nm particle size) in an aqueous piperazine solution (pH 11), R _{max was} within 20 nm, but buried alumina was difficult to obtain. Make interconnections, as a strong inward curvature occurred.

When particles of, for example, ceria, titania and Aluminum oxide, other than silica, in one aqueous alkaline solution are dispersed, so is the Reduction of Al dissolution rate not so clear as when silica particles are used, as explained above. However, one adds this aqueous Solution to a predetermined amount of silica particles, so can the ratio of the dissolution rate to Al polishing rate can be sufficiently reduced. In In this case, the effect of the present invention be achieved by particles of ceria, titanium oxide or alumina having a particle size of 100 nm or less in an aqueous solution having a pH of more are dispersed as 7.5, and silica particles with a Particle size of 100 nm or less of the resulting Solution be added.

Hereinafter, an embodiment in which Al is polished by using a mixture of alumina particles and silica particles will be described. A polishing solution was prepared by dispersing 10% by weight of aluminum particles having a particle size of 50 nm and 1% by weight of silica particles having a particle size of 50 nm in an aqueous piperazine solution having a pH of 11.0. The polishing apparatus and the object to be polished used were those shown in Figs. 2 and 12A, respectively. As a result of the polishing operation, as in the previous embodiment, neither flaws nor inward curvatures appeared on the Al surface, and the cross-sectional shape shown in Fig. 12B was obtained. The value of _Rmax on the Al surface was 9 to 10 nm. Similar experiments were conducted using particles of titanium oxide and ceria having a particle size of 50 nm instead of the alumina particles. As a result, it was possible to obtain identical effects as described above. Further, it was confirmed that in addition to the particles of alumina, titania and ceria, particles of diamond, silicon carbide and zirconia were also effective when used in the form of a mixture with silica particles.

As a substance for adjusting the pH, it is possible to use, for example, amines such as triethylamine, choline, and TMAH and ammonia instead of piperazine. In addition, even if particles of a substance other than silica are used, the Al dissolution rate can be extremely reduced by adding a substance commonly known as a corrosion inhibitor for Al. Although the corrosion inhibiting agent for Al which can be used varies depending on whether the solution is acidic or alkaline, known examples are silicates, chromates, amines, glucose, gum tragacanth, and agar. The inventors have made extensive experiments and found that when the polishing solution was alkaline, it was possible to obtain good properties, that is, a reduction in Al dissolution rate, at least with silica particles, silicates, glucose and agar. When these corrosion inhibitors were added to a polishing agent prepared by dispersing alumina particles (particle size 50 nm) in an aqueous solution of piperazine (pH 11), and polishing Al using each resultant polishing agent, it was further confirmed that R _{max was} within 20 nm, and at the same time an inward curvature was suppressed.

The above embodiment has been described with a Al film as an example of the object to be polished. Indeed it is also possible, for example, to Alloy film, the Al as the main ingredient and small Contains proportions of Cu or Si, as an object to be polished use. If a material is used which Mix in a polish, from polishing particles, one Corrosion preventing agent for suppression of Dissolution of a metal, and a chemical component is made to dissolve a metal, so can In addition, a film made of Cu or a Cu alloy or consists of Ag or an Ag alloy, as to be used polishing object. In addition, you can excluded in the present invention sections have different widths in different places. In addition to such modifications can be Various other modifications of the present invention without departing from the essence of the invention.  

Embodiment 2

In a polishing process, the remaining of Polishing particles after polishing (CMP) are a big problem because the remaining polishing particles are defects of Cause semiconductor devices. It is therefore necessary after the CMP to remove the polishing particles perfectly.

Conventional methods for removing the polishing particles after the CMP are pure water washing, scrubbing using a sponge scrubber or a brush scrubber, ultrasonic cleaning, and chemical cleaning using a mixed solution of sulfuric acid and hydrogen peroxide water. However, none of these cleaning methods can completely remove the polishing particles. The inventors performed CMP on a SiO ₂ film formed on a Si wafer of 6 inches (15 cm) using a polishing agent prepared by dispersing cerium oxide particles as polishing particles in pure water, and then gave a Scrubbing (cleaning 1) using a brush scrubber or a cleaning (cleaning 2), which was a combination of scrubbing and a chemical cleaning using a mixture solution of sulfuric acid and hydrogen peroxide water. Table 1 below shows the measurement results for the number of remaining particles at different particle sizes.

Table 1

As can be seen from Table 1, the number is left over Polishing particles after the CMP larger than before the CMP, regardless of the particle size. The minimum Machining dimension of an LSI already has the Submicron generation achieved, so that the requirements for the dust level has become stricter. Be this Taken into account, it becomes clear that itself Remaining particles with a particle size of 0.3 microns or less a significant effect on the Product yield. Therefore, no conventional Polishing method, which conventional polishing particles used the requirements for the production of LSIs meet next generation.

Therefore, in the present embodiment, a method described which can polish without one Inward curvature and the like, by Minimizing the amount of remaining polishing particles after the polishing process, causing a leveling of films and an embodiment of buried metal interconnects is carried out.  

The inventors have made extensive attempts to solve the problem above problems existing in the prior art performed, and found out that the amount Remaining polishing particles after polishing thereby can be minimized that as polishing particles particles used, which consists of an organic polymer compound do not exist in conventional polishing operations was used, or particles containing at least carbon as Main constituent and this makes it possible Perform polishing operations, without inward curvatures and to cause the like.

This embodiment therefore provides a polishing method Available, which is the step of polishing one polishing film using particles comprising consist of an organic polymer compound, or of Particles containing at least carbon as the main constituent contained as polishing particles. In this embodiment Preferably, the method comprises the step of removing the polishing particles by their ashing after the Polishing process on.

Examples of the organic polymer compound are Methacryluharz such as PMMA, a phenolic resin with a hardness similar to methacrylic resin, a urethane resin Melamine resin, a polystyrene resin, a polyacetal resin, and a Polycarbonate resin. Examples of the material which at least carbon as the main constituent are amorphous carbon, corundum, and carbon black, in which Graphite structural units, each or more layers have statistically combined.

The polishing particles described above are preferably spherical. This spherical shape comprises an im  essential spherical shape, no sharp, pointed Has sections. The spherical shape can be a mechanical one Suppressing effect during polishing, and thereby prevent the surface of a film being polished damaged or roughened. The mean particle size the polishing particle is preferably 0.01 to 0.1 μm. This because, then, when the mean particle size of the Polierteilchen smaller than 0.01 microns, the particles easily flocculate so that they increase the surface roughness and lead to instability of the polishing speed. is the mean particle size is larger than 0.1 μm, so does the Surface roughness to, and beyond that increases Inward curvature amount proportional to the particle size.

As a method for ashing the polishing particles after Polishing is possible, a plasma ashing treatment to use in which an oxygen plasma is used, or oxygen radicals are fed downstream, as well a high temperature treatment in an oxygen atmosphere. By these methods, the polishing particles can be easy be removed.

Examples of the film to be polished are a pure Al Film, a film consisting of an alloy whose Main component Al is, for example, an AlSiCu alloy and an AlCu alloy, a silicon oxide film Silicon nitride film, an amorphous silicon film, a polycrystalline silicon film, and a single crystal Silicon film.

The film to be polished, the polishing particles, and the solution to disperse the polishing particles must be properly be selected, and that adapted to each other, under Consideration of hardness or chemical etching. For example, in situations in which the solution to  Dispersing the polishing particles is preferably alkaline, becomes a film made of pure Al, an AlSiCu alloy, or an AlCu alloy, as the film to be polished used as polishing particles are particles from a organic polymer compound or particles Carbon black used. In such cases, in which the Solution is preferably acidic, becomes a film to be polished uses a film containing Cu as a main component, and As polishing particles become particles from an organic Polymer compound used.

The polishing method in this embodiment is remarkable in that the step of polishing one polishing film using spherical particles is provided, which consists of an organic polymer compound exist, or of particles, which at least carbon as Main ingredient included, as polishing particles. Because the Polierteilchen are spherical, is the resulting low mechanical impact. This prevents the Surface of the film to be polished during the CMP damaged or curved inwards. In addition, the Polierteilchen of the film to be polished completely Ashing will be removed, which causes that at Semiconductor components no defects occur, for example a reduction of the reliability or the Product yield resulting from the remaining of Polierteilchen could result. The combination of polishing apparatus described above and a Ashing device can be used in a case in which the polishing and the ashing using the carried out above polishing particles become.  

example 1

First, as shown in Fig. 13, an SiO ₂ film 42 was formed on a silicon substrate 41 , and 0.4 to 10 μm wide, 0.4 μm deep trenches 43 were formed by ordinary photolithographic and etching processes to form interconnections. Then, a 4500 Å thick Al film 44 was prepared on the entire surface without heating in an Ar atmosphere at a pressure of 10 ^-4 Torr using a DC magnetron sputtering method. In this way, a sample was fabricated. The number of residual polymer particles on the surface of the sample was measured using a dust counter. The results are shown in Table 2 below.

Then, by using the apparatus shown in Fig. 2, CMP was performed for this sample. It should be noted that a polishing pad made of polyurethane foam was used as the polishing pad 13 . In this CMP, a slurry prepared by dispersing 10.0% by weight of PMMA particles (polymethyl methacrylate) having an average particle size of 1000 Å in an aqueous alkaline solution having a pH of about 10 was used as a polishing agent , Ammonium polycarboxylate was used as the dispersant. The polishing pressure was 300 g / cm ² , and the rotational speeds of a turntable and a sample holder were 100 revolutions per minute. As a result, it was possible to leave Al almost completely in the trenches 43 shown in FIG . In addition, there were virtually no defects on the surface of the Al interconnect. It should be noted that the polishing speed for Al, V _Al = 150 A / min. The number of remaining polishing particles on the surface of the sample after the CMP was measured in the same manner as mentioned above. The result is also shown in Table 2 below.

Subsequently, the sample which was treated with CMP, washed with pure water using a sponge, and dried. At the same time the number remained Polierteilchen measured on the surface of the sample. The Result is given in Table 2 below. Then it became an ashing treatment with the sample at a Plasma output power of 500 W and one Oxygen partial pressure of 0.9 Torr performed, causing the remaining polishing particles were removed. The number of Polierteilchen, which remained on the sample surface, was measured in the same manner as explained above. This result is also shown in Table 2 below listed. All values given in Table 2 are Average values per wafer.

Table 2

As shown in Table 2, it was possible to almost completely remove the remaining polishing particles from the surface of the sample when incineration was performed on the sample. Most of the particles counted on the surface of the sample after ashing are believed to be dust particles or protrusions and recesses on the sample surface, rather than polishing particles. When CMP was carried out by using a slurry prepared by dispersing PMMA particles in pure water having a pH of 7, Al was not polished at all. The Al polishing rate of the polishing agent prepared by dispersing PMMA particles in pure water, that is, V _Al was therefore 0 A / min at a polishing pressure of 10 to 1000 g / cm ² . This result shows that when using PMMA particles in polishing Al, the solution of the polishing agent must be made either acidic or alkaline, so that a chemical etching occurs. By adding the chemical etching effect, a polishing rate can be obtained in practice. In order to increase the polishing rate by adding the chemical etching effect while preventing the damage of the Al surface, it is particularly desirable that the dispersion solution be alkaline.

In this embodiment, the sample having the structure shown in Fig. 13 is used. However, a sample having a structure shown in FIG. 14 can also be used. This arrangement was made as follows. First, a SiO ₂ film 42 was formed on a silicon substrate 41 , and a 500 Å-thick carbon film 45 as a polishing resistor film in an argon atmosphere was formed on the film 42 at a pressure of 10 ^-4 Torr by a DC magnetron sputtering process. Thereafter, trenches 43 were formed to form interconnects of similar dimensions to the trenches shown in FIG. 13 by conventional photolithographic and etching processes. While the resulting sample was heated to 500 ° C, a 4000 Å thick Al film 44 was then fabricated in an Ar atmosphere at a pressure of 10 ^-4 Torr by DC magnetron sputtering. It was found that in the sample having this structure, identical effects as described above could be obtained. With the method according to the present invention, therefore, it is possible to almost completely remove the polishing particles regardless of the presence or absence of the polishing resistor film, and regardless of the surface shape of the film to be polished. It should be noted that the carbon film 45 can be removed at the same time when the polishing particles are removed by the ashing treatment using an oxygen plasma in the same manner as Embodiment 1 , resulting in a reduced number of manufacturing steps.

Example 2

As shown in Fig. 15, a SiO ₂ film 42 was formed on a silicon substrate 41 , and trenches 43 were fabricated to form interconnections of the same dimensions as the trenches shown in Fig. 13 by conventional photolithographic and etching processes. Thereafter, a 500 Å thick Nb film 46 was formed on the entire surface in an Ar atmosphere at a pressure of 10 ^-4 Torr using a DC magnetron sputtering process. On the entire surface of the film 46 , a CuO _x film 47 (x = 0 to 0.5) having about 4000 Å thickness was prepared in an Ar-O ₂ gas mixture atmosphere at a pressure of 10 ^-4 Torr using a reactive ion sputtering process. In this way, a sample was prepared.

With the resulting sample, CMP was carried out under identical polishing conditions as in Example 1. It should be noted that the polishing agent used was a material prepared by dispersing 10.0% by weight of PMMA particles having an average particle size of 1000 Å in an aqueous acidic solution having a pH of about 3 , This resulted when the rotational speeds of a turntable and a sample holder were 100 revolutions per minute, and the polishing pressure was 300 g / cm ² , the polishing rate of the CuO _x film 47 was 200 to 250 A / min, slightly higher than for Al , After the CMP, the sample was cleaned using a sponge, and was subjected to an ashing treatment conducted under the same conditions as in Practical Example 1 , using an oxygen plasma. As a result, the polishing particles remaining on the sample surface were perfectly removed.

This example shows that when a CuO _x film is to be polished using PMMA particles as a polishing agent, a solution for dispersing the PMMA particles is preferably an aqueous acidic solution having a pH of about 3, which is a Ammonium salt, or a solution containing an ion which forms a complex ion or a chelate compound with copper to increase the polishing rate by additional chemical etching.

Example 3

As shown in Fig. 16, on a silicon substrate 41, an SiO ₂ film 42 having a thickness of 5000 Å was prepared. On this SiO ₂ film 42 , a 4000 Å thick Al film 44 and a 500 Å thick carbon film 45 were formed in this order. Thereafter, normal photolithographic and etching processes were carried out to form Al intermediates so that the carbon film 45 remained only on the upper surface. Then, another SiO ₂ film 42 was prepared, with a thickness of 4500 Å, by a plasma CVD method. In this way, a sample was prepared which had such a structure that the Al interconnects were embedded in the SiO ₂ film. CMP was performed on this sample under polishing conditions similar to those in Example 1. It should be noted that as a polishing agent, a material prepared by dispersing 1.0 wt% of amorphous carbon particles having an average particle size of 0.5 μm in pure water was used. In this preparation of the polishing agent, ammonium polycarboxylate was used as the dispersing agent. It was found that it was possible to leave the SiO ₂ film 42 behind the Al interconnects and completely remove the SiO ₂ film 42 from the carbon film 45 . It should be noted that the polishing rate of the SiO ₂ film 42 was approximately 2000 A / min when the rotational speeds of a turntable and a sample holder were 100 revolutions per minute and the polishing pressure was 300 g / cm ² .

After the CMP, the resulting sample was cleaned using a sponge and subjected to an ashing treatment using an oxygen plasma. In this way, the remaining polishing particles on the surface of the sample were completely removed. It should be noted that the plasma output was 500 W and the O ₂ partial pressure was 0.9 Torr. In this ashing treatment using an oxygen plasma, the carbon film on the Al interconnects 44 can be simultaneously removed, resulting in a reduced number of manufacturing steps.

From this example, it is found that when polishing an SiO ₂ film using amorphous carbon particles having an average particle size of 0.5 μm as a polishing agent, a dispersion solution is preferably an aqueous alkali hydroxide solution to increase the polishing rate by an additional chemical etching.

Example 4

In this example, the method of the present invention is applied to the buried element isolation step. First, as shown in Fig. 17A, buried element isolation trenches 48 having a depth of 0.8 μm and a width of 0.35 μm were formed in a silicon substrate 41 by means of normal photolithographic and etching processes. Thereafter, a 0.8 μm-thick SiO ₂ film 42 was prepared to bury the trenches 48 by a CVD method using TEOS gas and O ₂ gas. In this way, a sample was prepared. Then, as shown in Fig. 17B, CMP was performed on the sample by the same procedure as in Example 3. Then, as shown in Fig. 17C, heat treatment of the sample was performed in an oxygen atmosphere, at atmospheric pressure and at a temperature of 1000 ° C for 30 minutes, whereby Polierteilchen 49 were completely removed.

Example 5

In this example, particles of an organic polymer compound and particles of another substance are used together as polishing particles. As a sample, the arrangement shown in Fig. 14 was used and the sample was subjected to CMP. A polishing agent was prepared by dispersing silica particles having an average particle size of 350 Å in an aqueous alkaline solution having a pH of 11. When rotational speeds of a turntable and a sample holder were set at 100 rpm, and when the polishing pressure was 300 g / cm ² , the Al polishing rate V _{Al of} the polishing agent was 900 A / min.

Then, for the purpose of polishing the sample and simultaneously removing the remaining silica particles from the sample surface, polishing was performed on a turntable other than the above-mentioned polishing table, at a polishing pressure of 100 g / cm ² , with rotary speeds of the turntable and the sample holder of 100 revolutions per minute, with a polishing time of one minute, using a polishing agent prepared by dispersing PMMA particles having an average particle size of 1000 A in an aqueous alkaline solution having a pH of 3.

Then, an ashing treatment using an oxygen plasma under the same conditions as in Example 1 was performed on the sample. It was therefore possible to prepare Al intermediates on which neither the silica particles nor the PMMA particles remained. It should be noted that in the ashing treatment using an oxygen plasma, the carbon film 45 can also be removed. Therefore, even if a normal polishing agent is used, it is possible to obtain a practical polishing speed and easily remove the remaining polishing particles.

Comparative Example 1

CMP was carried out by the same procedure as in Example 3, except that the abrasive particles used were diamond particles having an average particle size of 0.5 μm. Therefore, it was possible to remove the polishing particles by sponge cleaning and a heat treatment performed after the CMP in an oxygen atmosphere. However, a large number of voids formed on the surface of an SiO ₂ film of the sample, and the surface roughness Ra took a value of about 2600 Å, indicating an extreme roughening of the surface. It may be considered that the reason is that the corrected Mohs hardness of the diamond particles is 15, which is more than the corrected Mohs hardness of 8 for the SiO ₂ film, and that the particle shape is irregular and non-spherical.

From this comparative example it follows that Diamond particles with respect to the surface roughness and the occurrence of defects on the surface are unsuitable.

As explained above, the polishing method according to FIG This embodiment, a film to be polished below Use of spherical particles consisting of an organic Polymer compound, or of particles that at least Contain carbon as the main constituent, as Polishing. Therefore, it is possible the amount remaining polishing particles after polishing minimize and polish without one  To cause inward curvature of the like. this makes possible it, leveling films and training buried Metal interconnections with high reliability and high yield.

Embodiment 3

In CMP fine polishing particles, which in sections including fine intermediates in the Magnitude of sub-micron range or in small steps entering trenches, not sufficient by washing with Water and / or scrubbing be removed, as above explained. For this reason, stay on metal Intermediate compounds inevitable polishing particles left over. Around Flattening films and metal interconnects with high It is therefore quality and high reliability essential to reduce errors and inward curvatures, and on the surface of a film to be polished after the CMP remaining polishing particles.

Therefore, in this embodiment, a method described the leveling of films and the Training buried metal interconnects properly by sufficient removal after the CMP remaining polishing particles performs.

This embodiment provides a polishing method Available, which has the following steps: training a polishing resistant film made of a material with a polishing rate that is lower as those of the material of a film that is to be polished at least in projecting portions of a substrate, which the projecting sections and recessed ones Has sections, producing the film to be polished on the polish resistant film, and polishing the  polishing film using a polishing agent, which has polishing particles with a particle size which less than the thickness of the polishing resistant Film.

Under projecting and recessed sections are to understand such protrusions and sections that be formed when in a substrate trenches for Interconnections or openings for connecting lines Examples of polishing particles for use in this embodiment, silica particles, Ceria particles, zirconia particles, alumina particles, Titanium oxide particles, silicon carbide particles, diamond particles and graphite particles.

Examples of the material of the polish resistant film for use in this embodiment are carbon, Si, SiO ₂ , SiN, Ti, TiSi _x , W, Nb, WSi _x , and MoSi _x . It should be noted that the material for the polishing-resistant film is selected from materials each having a lower polishing speed than the material of the film to be polished with respect to polishing particles used in the polishing. Therefore, it is necessary to properly select the combination of the material of the polishing-resistant film, the material of the film to be polished, and the polishing particles to satisfy the above-mentioned conditions. An example is a combination of carbon as a material for the polishing-resistant film, Al as a material for the film to be polished, and silica particles as polishing particles.

The particle size of the polishing particles used in this embodiment is set smaller than the thickness of the polishing-resistant film, for the reason explained below. Since the film to be polished is polished more easily than the polishing-resistant film during polishing, polishing particles penetrate into the film to be polished under the influence of pressure. This causes the polishing process to be excessively severe. The degree of penetration of the polishing particles, that is the extent of the inward curvature, increases with increasing particle size. Therefore, the particle size is adjusted as explained above to reduce the amount of inward curvature to about the thickness of the polishing resistant film. Now, as shown in FIG. 18A, it is assumed that an interconnection metal 52 is buried in a recessed portion of an insulating film 51 , and a polishing-resistant film 53 is provided on a projecting portion of the insulating film 51 . In this case, if the particle size of the polishing particles 54 is extremely smaller than the thickness of the polishing resistant film 53 , during the polishing operation, those portions where the polishing particles 54 and the interconnection metal 52 are in contact with each other are difficult to polish. Is therefore, as shown in Fig. 18B, the intermediate metal 52 from the surface of the insulating film 51 from before, when removed after the polishing the polish resistant film 53. This is highly undesirable in terms of leveling. For this reason, the particle size of the polishing particles must be selected so as to satisfy the condition that the particle size / thickness of the polishing-resistant film is 0.3. It should be understood that particle size means an average particle size and that it is highly preferred that the polishing particles have a particle size distribution at which the weight of particles having particle sizes is twice or less than the average particle size of 80%. or more of the weight of all the polishing particles.

The polishing method according to this embodiment draws characterized in that a polishing-resistant film, the made of a material with a lower Polishing speed than that of a film to be polished exists, at least on projecting sections of a Substrate is formed, which the projecting Sections and excluded sections, and to Polishing film on the polish resistant film is formed, and using a polishing agent is polished, which polishing particles with a particle size contains less than the thickness of the polish resistant film.

The polishing particles with a smaller particle size than the Thickness of the polishing resistor film polish the to be polished Film with a thickness corresponding to the particle size. There but hardly any pressure is applied to the polishing particles, due to the presence of the polish resistant Films, the particles do not polish the film to be polished continue. Therefore, it is prevented that the film to be polished until to a position below the position of the lower one Surface of the polishing resistant film is polished. This allows the occurrence of errors and one To prevent roughness on the surface, as well as that Occurrence of inward curvatures, and the embedding of Polierteilchen, so those problems that occur when a polished film to be polished, made of a material low hardness. In addition, all lie Polierteilchen, not by a cleaning after the CMP be removed, free on the surface when the polish resistant film is removed. Therefore, you can these remaining particles easily through a be removed subsequent cleaning process.  

Example 6

First, as shown in FIG. 19, an SiO ₂ film 62 was formed on a silicon substrate 61 , and interconnection formation trenches 63 each having a width of 0.4 to 10 μm and a depth of. Were prepared by conventional photolithographic and etching processes 0.4 μm. Subsequently, a 500 Å thick carbon film 64 was produced on the entire surface by DC magnetron sputtering. On the entire surface of this carbon film 64 , a 4000 Å thick Al film 65 was formed without heating in an Ar atmosphere at a pressure of 10 ^-4 Torr using DC magnetron sputtering. Thereafter, a heat treatment of the Al film 65 was performed in a vacuum (for example, at a pressure of 10 ^-4 Torr), whereby the Al film 65 was flocculated and buried while suppressing the formation of a natural oxide film on the surface of the Al film 65 , The temperature in the heat treatment was, for example, 600 ° C. As a result, Al was changed to a single crystal, and the Al film 65 was buried in the trenches 63 and remained on projecting portions in the form of islands. In this way, a sample was prepared.

Using the apparatus shown in Fig. 2, a CMP was then performed on the resulting sample. It should be noted that a polyurethane foam polishing pad having a plush or velor surface was used as the polishing pad 13 . The polishing agent used in this CMP was prepared by treating silica particles having a particle size of 500 Å at a ratio of 10% by weight relative to the total weight in a dilute aqueous solution of piperazine (C ₄ H ₁₀ N ₂ ) having a pH of Value of 11 were dispersed. This has been because, as polishing particles suitable for CMP for forming metal buried interconnections, those having a particle size of 1000 Å or less are less preferable in leveling. The polishing conditions were a polishing pressure of 50 to 300 g / cm ² ₁ of a turntable rotational speed of 50 to 500 rpm, and a polishing agent supply amount of 300 cm ³ / min.

In this CMP, the polishing speed V _{Al of} the Al film and the polishing speed of the Vc of the carbon film were 830 A / min and 0 A / min, respectively. This indicates that the carbon film worked almost perfectly as a polishing resistance film. Therefore, when the entire surface of the carbon film 64 was exposed, the polishing process on the projecting portions 66 did not proceed. However, in the trenches 63 in which the upper surface of the Al film 65 was exposed, the polishing continued because the polishing rate for Al was higher than that for carbon. Since the carbon film 64 was present on the protruding portions 66 , the pressure from the polishing pad 13 was hard to be transferred to polishing particles 67 at the time when polishing was performed from the upper surface of the carbon film 64 to a depth corresponding to approximately the outer diameter of the outer diameter Polierteilchen progressed. Therefore, the polishing process stopped. At this time, the surface of the Al film 65 buried in the trenches 63 was almost at the same level as the lower surface of the carbon film 64 as a polishing resistance film.

After the CMP, the sample was washed with pure water, scrubbed using a PVA fabric (polyvinyl alcohol), and ultrasonic cleaning (first cleaning). The section of the resulting sample is shown in Fig. 20A. The presence or absence of polishing particles remaining on the sample was checked by using a dust checking device and a SEM (Scanning Electron Microscope). As shown in Fig. 20A, it was found that no polishing particles 67 were present on the carbon film 64 on the protruding portions 66 , and a small amount of polishing particles 67 were present on the Al film 65 buried in the trenches 63 .

Subsequently, an ashing treatment using an oxygen plasma at an oxygen partial pressure of 0.9 Torr and a plasma output of 500 W was performed on the sample, thereby removing the carbon film 64 existing on the protruding portions 66 . The section through the ashed sample is shown in Fig. 20B. As shown in FIG. 20B, the surface of the exposed SiO ₂ film 62 was formed substantially in alignment with the surface of the Al film 65 . It may be considered that the reason for this is that the carbon film 64 was relatively easily etched when exposed to the oxygen plasma but not etched as it was protected by a natural oxide film formed on its surface.

The resulting sample was then washed with pure water, scrubbed using a PVA fabric, and ultrasonically cleaned (second cleaning), whereby the polishing particles 67 remaining on the Al film 65 were removed. The presence or absence of the remaining polishing particles on the sample in this state was checked by using the dust checking device and the SEM. As a result, as shown in Fig. 20C, the polishing particles 67 remaining on the Al film 65 were almost perfectly removed. It may be considered that the reason for this is that due to the fact that after the CMP, the carbon film 64 was removed from the protruding portions 66 , only the polishing particles 67 protruded from the substrate surface, and the removal of the particles by a mechanical Operation facilitated. In addition, neither flaws nor inward curvatures appeared on the surface of the Al film buried in the trenches 63 .

With the sample shown in Fig. 19, CMP and the ashing treatment were separately carried out by the same procedure as described above by changing the ratio of the polishing particle size and the polishing resistor film thickness by changing the particle size of the SiO ₂ particles as polishing particles to 200 to 750 Å The thickness of the carbon film 64 as a polishing resistor film was kept at 500 A, whereby the carbon film 64 was removed. Then the polishing particles were removed by cleaning. Using the dust counter, the number of polishing particles having a particle size of 0.2 μm or more remaining on the surface of each resulting sample after the second cleaning was measured. The result is shown in FIG. 21. It should be noted that the width of interconnection formation trenches of the sample was 0.4 μm. As is clear from Fig. 21, when the particle size of the polishing particles is smaller than the thickness of the polishing resistor film, that is, when the ratio of polishing particle size to polishing resistor film thickness is smaller than 1, the number of remaining polishing particles on the surface of the sample is very small. In this example, the number of remaining polishing particles averaged 10 or less per 6-inch (15 cm) wafer after the polishing resistor film was removed and cleaning was performed.

The above phenomenon was examined by making the particle size of the polishing particles smaller than the thickness of the polishing resistor film, and changing the particle size within the range of 100 to 1000 Å. As a result, the Al film 65 in the trenches 63 was polished from the upper surface of the polishing resistor film to a depth of about the particle size of the polishing particles in each case. Therefore, it has been found that by using polishing particles having a particle size smaller than the thickness of a polishing resistor film, the position of the formed upper surface of the Al film 65 becomes higher than or equal to the position of the lower surface of the polishing resistor film. Therefore, the polishing particles can be stably removed by performing washing with water, scrubbing, and ultrasonic cleaning in this state.

In this example, a PVA fabric was used in the Used scrubbing. However could appropriate Results using a sponge, one Nylon brush, a polyurethane foam fabric, and a non-woven fabric, instead with a PVA fabric.

Example 7

As shown in Fig. 22, a SiO ₂ film 62 was formed on a silicon substrate 61 , and a 500 Å-thick carbon film 64 was formed on the entire surface by DC magnetron sputtering. Thereafter, interconnection formation trenches 63 having the same dimensions as in Example 6 were prepared by ordinary photolithographic and etching processes. A 4000 Å thick Al film 65 was then formed over the entire surface of the resulting assembly, in an Ar atmosphere at a pressure of 10 ^-4 Torr using DC magnetron sputtering. In this case, as shown in Fig. 22, furrows were generated on the Al film when the temperature of the silicon substrate 61 was raised to, for example, 500 ° C. In this way, a sample was prepared.

With the resulting sample, CMP was carried out by the same procedure as in Example 6, whereby the Al film 65 was buried in the trenches 63 , and the excess Al film was removed from the protruding portions 66 . Then, the resulting sample was subjected to a first cleaning, an ashing, and a second cleaning, by the same procedure as in Example 1. As a result, most of the polishing particles remaining on the surface of the sample could be removed.

Thereafter, the dependence of the extent of the inward curvature on the polishing time of this sample was checked. The degree of inward curvature, as shown in Fig. 23, represents a distance D from the position of the upper surface of the carbon film 64 to the position of a portion of the smallest thickness of the Al film 65. It should be noted that the particle size used Polishing particles 67 were set to 500 and 1000 A, the thickness of the carbon film 64 as a polishing resistance film to 500 A, and the width of the Al film 65 as a line width to 10 microns.

As shown in Fig. 24, when the particle size of the polishing particles is equal to the thickness (500 Å) of the polishing resistor film, the relationship between the extent of the inward curvature and the polishing time is such that the extent of the inward curvature is kept smaller than the film thickness. In addition, the amount of inward curvature was still smaller than the film thickness even when the polishing time was twice that required for completely polishing away the Al film 65 . As the particle size of the polishing particles increases, the polishing rate increases, and the degree of inward curvature also increases. Furthermore, the increase (slope) in the degree of inward curvature after removal of the excess Al film 65 is larger than when the particle size is 500 Å. When the extent of the inward curvature was checked by changing the width of the Al film 65 , the amount remained approximately the same for widths of 0.5 to 10 μm.

Fig. 25 shows the degree of inward curvature for a 10 μm Al film when the particle size of the polishing particles was changed while the thickness of a polishing-resistant film was held at 500A. As shown in Fig. 25, when the particle size of the polishing particles is as large as the thickness (500 Å) of the polishing resistor film, a turning point exists in the graph. For particle sizes below the inflection point, the degree of inward curvature changes moderately below the thickness of the polishing resistor film. For particle sizes above the inflection point, the rate of increase of the amount of inward curvature becomes nearly proportional to that of the particle size. From Figs. 24 and 25, it can be seen that a surprising effect of reducing the amount of inward curvature can be expected when the polishing is carried out using polishing particles whose particle size is smaller than the thickness of a polishing resistor film.

Example 8

According to Fi 48186 00070 552 001000280000000200012000285914807500040 0002004410787 00004 48067g. 26, a SiO ₂ film 62 was formed on a silicon substrate 61 , and interconnect formation trenches 62 each having a width of 0.4 to 10 μm and a depth of 0.4 μm were prepared by ordinary photolithographic and etching processes. Thereafter, a 500 Å thick polycrystalline silicon film 68 was formed on the entire surface by AC magnetron sputtering. Thereafter, a 4000 Å thick Cu film 69 was produced on the entire surface in an Ar atmosphere at a pressure of 10 ^-4 Torr using DC magnetron sputtering. In this case, 69 grooves were formed on the Cu film as shown in Fig. 26, when the temperature of the silicon substrate 61 was raised to, for example, 700 ° C. In this way, a sample was prepared. Thereafter, the sample was subjected to CMP by the same procedure as in Example 6, whereby the Cu film 69 was buried in the trenches 63 , and the excess Cu film was removed from the protruding portions 66 . It should be noted that the polishing agent used was prepared by dispersing silica particles in an aqueous piperazine solution and mixing an oxidizing agent into the resulting dispersion.

After CMP, the resulting sample was washed with pure water, scrubbed using a PVA fabric, and sonicated. The remaining polishing particles on the sample were checked using a dust checking device and an SEM. As a result, as shown in Fig. 27A, it was found that no polishing particles 67 were present on the polycrystalline silicon film 68 on the protruding portions 66 and a small amount of polishing particles 67 on the Cu film 68 buried in the trenches 63 is, was present. Then, the sample was subjected to plasma etching using a CF ₄ plasma to remove the polycrystalline silicon film 68 formed on the protruding portions 66 . Fig. 27B shows the section through the sample after plasma etching. As shown in FIG. 27B, the surface of the SiO ₂ film 62 was approximately at the same level as the surface of the Cu film 69 .

Thereafter, the resulting sample was subjected to a pure water washing, scrubbing using a PVA fabric, and ultrasonic cleaning, thereby removing the polishing particles 67 remaining on the Cu film 69 . In this state, the remaining polishing particles on the sample were checked using the dust checking device and the SEM. As shown in Fig. 27C, it was found that the remaining polishing particles 67 on the Cu film 69 were almost completely removed. Moreover, neither flaws nor inward curvature occurred on the surface of the Cu film 69 buried in the trenches 63 .

In each of the above-described Examples 6 to 8 The slurry used was the polish by the slurry Dispersing silica particles in an aqueous Piperazine solution having a pH of 11 was prepared. However, it is also possible to use amines such as Triethylamine, choline, and TMAH (tetramethylammonium hydroxide), Ammonia, or alkali hydroxide as the alkali solution to Adjust the pH value.  

Example 9

As shown in Fig. 28, a SiO ₂ film 62 was formed on a silicon substrate 61 , and a 4000 Å thick Al film 65 and a 500 Å thick carbon film 64 were formed in this order on the film 62 by DC magnetron sputtering , Then, a pattern having a line width of 0.04 to 10 μm was formed by usual photolithographic and etching processes. Then, a 10,000 Å thick SiO ₂ film 70 was formed on the entire surface by a plasma CVD method using organic silane gas. In this way, a sample was prepared. Thereafter, CMP was performed on the resulting sample by the same procedure as in Example 6, whereby the SiO ₂ film 70 was removed to the position of the upper surface of the Al film 65 . As the polishing agent, a slurry having a pH of 10.0, which was prepared by dispersing silica particles having a particle size of 500 Å in an aqueous potassium hydroxide solution, was used. The polishing speed V _{OX of} the SiO ₂ film and the polishing speed V _{C of} the carbon film were 1000 and 10 A / min, respectively, indicating sufficient polishing selectivity.

After the CMP, the resulting sample was subjected to a pure water washing, scrubbing using a PVA fabric, and ultrasonic cleaning. The polishing particles remaining on the sample were checked using a dust checking device and an SEM. As a result, as shown in Fig. 29A, a small amount of polishing particles 27 were observed on the SiO ₂ film 70 . Thereafter, ashing treatment with the sample was conducted by the same procedure as in Example 6, whereby the carbon film 64 formed on the Al film 65 was removed. Fig. 29B shows the portion of the sample after the ashing treatment. As shown in Fig. 29B, the surface of the exposed SiO ₂ film 62 was nearly level with the surface of the Al film 65 .

The resulting sample was then subjected to a pure water washing, scrubbing using a PVA fabric, and ultrasonic cleaning, thereby removing the polishing particles 67 remaining on the SiO ₂ film 70 . In this state, the remaining polishing particles on the sample were checked using the dust checking device and the SEM. As a result, as shown in Fig. 29C, the polishing particles 67 remaining on the SiO ₂ film 70 were almost completely removed. Furthermore, it was found that the amount of inward curvature was reduced within the thickness of the polishing resistor film. Therefore, it was confirmed that identical effects can be obtained even if the film to be polished is not a metal film.

In the above-described polishing method according to This embodiment is a polishing resistance film, the made of a material with a lower Polishing speed than that of one's material too polishing film, at least on a projecting Formed portion of a substrate, which the projecting section and a recessed section having. The film to be polished will be on this Polished resistor film formed and polished under Use of a polishing agent, which polishing particles with a particle size smaller than the thickness of the polishing resistor film. This allows the Reduce inward curvature and in more satisfactory  After polishing, remaining polishing particles remove. Therefore, a leveling of films and a Education of buried metal interconnects good carry out. Furthermore, this facilitates the removal of Polierteilchen, which on the surface of the to be polished Films remain after polishing.

Furthermore, the polishing amount can be controlled by the combination of the polishing resistor film and the polishing film is suitably selected, or the Combination of the thickness of the polishing resistor film and the Particle size of the polishing particles. This allows the Production of semiconductor devices with high Reliability.

Embodiment 4

For example, although SiO ₂ , Al, Cu and W can be used as a material of an object to be polished by CMP in a semiconductor manufacturing process, the polishing temperature under other polishing conditions regardless of the metal to be polished is of the utmost importance. A change in the temperature of the CMP leads to strong changes in the polishing rate and the polishing properties. Conventional polishing apparatuses use polishing temperature adjusting means for reducing changes in the polishing speed and the polishing properties caused by a change in the polishing temperature. For example, a cooling water circulation unit is connected to a container for storing a polishing agent to keep the temperature of the container constant, thereby preventing changes in the polishing characteristic caused by a temperature change. Alternatively, a cooling water circulation unit may be connected to a turntable for cooling thereof, whereby the flatness of the turntable is maintained, namely by preventing its twisting. An example of a polishing apparatus having devices of this type is Mecapol E2000 (product name, manufactured by PRESSI CORPORATION (France)). This polishing apparatus has means for cooling a turntable by spray-cooling water against the lower surface of the table.

The inventors have made extensive experiments and found that when performing CMP for the purpose the formation of buried interconnections that out a soft metal such as Al, Cu or Ag when a polish slurry at a low temperature of about 0 to 10 ° C is supplied to the resulting inward curvature of the metal is less than when the polish slurry is at room temperature is fed from 20 to 30 ° C. If, however, a Polish, which by dispersing polishing particles is produced at low temperatures in one Container is kept for storing the polishing agent, Flake the polishing particles easily and are precipitated. If a polish in which polishing particles flocculate and failures, so an inhomogeneous polish, for the Polishing is used, defects on the Surface formed of an object to be polished, or it changes the polishing speed or the Polishing properties. Conventional polishing devices use a stirrer in a container to flocculate and precipitation of contained in a polishing agent Prevent polishing particles. However, if the polish kept at low temperatures, flocculation may occur and precipitation of the polishing particles by the stirrer alone can not be sufficiently prevented. Therefore, it is impossible  the appearance of imperfections on the surface of a too to avoid polishing object, or the changes of Polishing speed and polishing properties.

Therefore, the present embodiment stops Polishing method for polishing an object to be polished Available while the temperature of a turntable is adjusted to be supplied to polishing agent, under Use of a polishing apparatus which has a Polishing agent storage container for storing the Polishing agent, the turntable for polishing the zu polishing object, a polishing agent supply pipe for supplying of the polishing agent from the polishing agent storage container the turntable, a polishing object jig for Holder of the object to be polished so that the to be polished Surface of the object opposite the turntable, and a polish supply tube temperature adjuster for adjusting the temperature of the polishing agent.

Example 9

Fig. 30 is a schematic view showing an example of a polishing apparatus according to Embodiment 4. In Fig. 30, reference numeral 81 denotes a sample holder. This sample holder 81 is connected to a drive mechanism (not shown) and can be vertically moved and rotated by the drive mechanism. An object 82 to be polished is clamped on the sample holder 81 by means of vacuum. A polishing table 84 is disposed below the sample holder 81 . A polishing pad 83 is attached to the upper surface of the polishing table 84 . The polishing table 84 and the polishing pad 83 form a turntable. This turntable can be rotated by a drive mechanism (not shown).

A pipe 85 is disposed in the polishing table 84 and connected to a table temperature setting unit 86 . A medium such as water circulates through the tube 85 . The table temperature adjusting unit 86 has a cooling device and a heater (both of which are not shown), and adjusts the temperature of the medium circulating through the pipe 85 . In this way, the temperature of the turntable is adjusted.

A polishing medium storage container 87 of 50 liters for storing a polishing agent is disposed at a location above the turntable. An impeller (propeller) 88 for stirring the polishing agent is disposed inside the container 87 . A polishing agent supply pipe 89 is connected to the sidewall of the polisher storage container 87 . A polishing agent temperature adjusting unit 92 is connected to the pipe 89 . This unit 92 has a cooling device (not shown). When a polishing agent 91 flows through the polishing agent supply pipe 89 , the temperature of the polishing agent 91 is adjusted before the agent is supplied to the polishing pad 83 . A pipe 93 is wound around the polishing agent storage container 87 and connected to a container temperature adjusting unit 94 . A medium such as water circulates through this tube 93 . The container temperature adjusting unit 94 has a cooling device and a heater (both not shown), and adjusts the temperature of the medium circulating through the tube 93 . In this way, the temperature of the polishing agent storage container 87 is adjusted. It should be noted that the polishing agent temperature setting unit 92 and the container temperature adjusting unit 94 may be controlled or regulated either independently or simultaneously. In this way, the polishing apparatus according to the present invention is constructed.

In actually polishing an object to be polished by using the polishing apparatus having the above arrangement, the sample holder 81 and the turntable are rotated by their respective driving mechanisms. The sample holder 81 is then moved down to press the object 82 to be polished against the polishing pad 83 with a predetermined load. In this state, the polishing is performed while supplying the polishing agent 91 from an injection port 90 of the polishing agent supply pipe 89 onto the polishing pad 83 .

A method of producing buried Intermediates of Al on a semiconductor substrate using the above Polishing apparatus will be described below.

First, a SiO ₂ film was formed on a silicon substrate 100, and on the entire surface of the _SiO2 film 100, a 50 nm thick carbon film 100 was formed by magnetron sputtering. Then trenches (1, 3, 5 and 10 microns wide) for the formation of intermediate compounds were prepared by a normal photolithographic process. Thereafter, an Al film 102 was formed on the entire surface by DC magnetron sputtering. In this case, the Al film 102 was formed to have a thickness of 450 nm, which was more than the height of the trench stages. In this way, the object 82 to be polished was produced.

The resulting object 82 was placed on the sample holder 81 and treated with CMP. As the polishing pad 83 , a material prepared by attaching a foamed polyurethane layer to a non-woven fabric and having a total thickness of 1.5 mm and a Shore hardness of 66 to 88 was used. This polishing pad was selected because, when CMP was performed on soft metals, for example, Al and Cu, at a polishing pressure of 30 to 600 gf / cm ² using only water, no defects having a depth of 100 nm or more the polished surface were generated, regardless of the hardness and the polishing pressure. As the polishing agent 91 , a material prepared by dispersing 1% by weight of silica particles having an average particle size of 35 nm in pure water was used. The polishing conditions were set as indicated below. It should be noted that the turntable temperature was kept constant by the table temperature setting unit 86 .

Polishing pressure: 300 g / cm ² Turntable Temperature: 25 ° C (room temperature) Polishing table rotating speed: 100 revolutions per minute Rotational speed of the sample holder: 100 revolutions per minute.

Under the above polishing conditions was the temperature of the supplied polish under Changed conditions (1) and (2) below.

Condition (1)

The polishing agent 91 was supplied to the polish storage container 87 at 25 ° C (room temperature), and the temperature of the polisher storage container 87 was set to 25 ° C by the container temperature setting unit 94 . During adjustment, the polishing agent 91 stored in the polish storage container 87 was agitated by the propeller 88 . When the polishing agent 91 was supplied to the polishing pad 83 via the polishing agent supply pipe 89 , the temperature of the polishing agent 91 was varied between 1 and 80 ° C by the polishing agent temperature adjusting unit 92 .

Condition (2)

The polishing agent 91 was supplied to the polish storage container 87 at 25 ° C (room temperature), and the temperature of the polish storage container 87 was changed between 1 and 80 ° C by the container temperature adjusting unit 94 , while the polishing agent 91 stored in the polish storage container 87 was replaced by the polisher Propeller (impeller) 88 was stirred. When the temperature of the polishing agent 91 in the polishing agent storage container 87 had stabilized, the polishing agent 91 was supplied to the polishing pad 83 through the polishing agent supply tube 89 . At this time, the polishing agent temperature setting unit 92 was removed.

FIGS. 32 and 33 are graphs showing the relationship between the amount of inward curvature of the Al interconnect and the slurry temperature and the relationship between the maximum surface roughness R _max on the Al surface and the slurry temperature when shown in FIG , object to be polished under conditions (1) and (2) was polished. In this connection, it is noted that it was difficult to directly measure the temperature of the polishing agent supplied to the polishing pad 83 , so the temperature (polishing surface temperature) on the surface of the polishing pad 83 was measured instead of the polishing agent temperature.

As shown in Fig. 32, the values for the degree of inward curvature in the state (1), that is, when the temperature adjustment was performed using the polishing agent supply pipe 89 are almost the same as those in the state (2), that is, the temperature setting was performed using the polisher storage container 87 . More specifically, the degree of inward curvature decreases as the temperature of the slurry is lower. Therefore, the degree of inward curvature of the object to be polished can be reduced by lowering the temperature of the polishing agent. Further, as shown in FIG. 33, when the polishing agent temperature is low, the maximum surface roughness R _max on the Al surface after polishing is reduced by performing the temperature adjustment by the polishing agent supply pipe 89 .

In a material such as a polishing agent in which polishing particles are dispersed as fine particles in a solution, when the particles are sufficiently small, the dispersion state generally becomes due to Brownian motion or interparticle repulsions due to electric charges stored on the surfaces maintained. However, if the particles are large or the energy for Brownian motion (molecular motion) due to low temperature is insufficient, the particles will flocculate and precipitate. For this reason, when the polishing agent storage container 87 is cooled, the energy for Brownian molecular motion becomes insufficient even when it is stirred, so that the polishing particles are flocculated and precipitated. This causes the maximum surface roughness R _max on the Al surface after polishing to increase. On the other hand, when the polishing agent supply pipe 89 is cooled, the polishing agent 91 is kept dispersed in the polishing agent storage container 87 . Moreover, since the polishing agent is cooled immediately before being supplied to the polishing pad 83 , neither flocculation nor precipitation of the polishing particles takes place. Therefore, the maximum surface roughness R _max on the Al surface after polishing is small.

The following experiment was conducted to confirm the above assumption. First, the polishing agent 91 was supplied to the polish storage container 87 at 25 ° C (room temperature) and stirred by the propeller 88 . The setting temperature of the polishing agent temperature adjusting unit 92 was set to 5 ° C. In this state, the polishing agent 91 was supplied to the polishing pad 83 through the polishing agent supply pipe 89 . As a result, there was a constant polishing agent temperature at the injection port 90 of 5 ± 0.5 ° C. When the polishing agent 91 injected from the injection port 90 was examined, it was found that neither flocculation nor precipitation had occurred. Then, the polishing agent 91 was supplied to the polish storage container 87 at 25 ° C (room temperature), and stirred by the propeller 88 . The setting temperature of the container temperature adjusting unit 94 was set to 5 ° C. In this state, the polishing agent 91 was supplied to the polishing pad 83 through the polishing agent supply pipe 89 . This resulted in a polishing agent temperature at the injection port 90 of 5 ± 0.5 ° C at each time point as in the previous case. When the polishing agent 91 injected from the injection port 90 was inspected, however, a gel precipitate of silica was present in an amount of 1 cc per liter.

From the experiment described above, when the polishing agent 91 is adjusted to a low temperature in the polishing agent storage container 87 , it is not possible to completely achieve flocculation and precipitation of the polishing particles by the stirring action of the propeller 88 alone. That is, with a prolonged period in which the polishing agent 91 is kept at a low temperature, flocculation and precipitation of the polishing particles becomes more likely. The polishing particles with a large particle size flocculated in this way cause defects on the surface of the object to be polished. Therefore, in order to supply the polishing agent at a low temperature and in a stable, dispersed state, it is particularly preferable to maintain the polishing agent 91 at a temperature at which neither flocculation nor precipitation of the polishing particles in the polish storage container 87 occurs, and the polishing agent in the polish supply pipe 89 cooled immediately before delivery to the turntable. It should be noted that in order to cool the polishing agent 91 immediately before it is supplied to the turntable, it is possible to perform a process in which the polishing agent 91 held at a temperature at which neither flocculation nor precipitation of the polishing particles occurs, a cooled turntable is supplied. However, in this method, the polishing agent constantly flows during the polishing process, and the thermal conductivity of the polishing pad on the turntable is small. Therefore, this procedure is considered impractical if these facts are taken into account.

Although the Al film is used as the object to be polished in Example 9, this Al may contain a small proportion of an impurity. For example, even if the object to be polished is a film made of an Al alloy containing 1.0 wt% of Si or 1.0 wt% of Cu, the above-described effects can be obtained. In addition, in Example 9, as a polishing agent for Al, a material prepared by dispersing 1.0 wt% of silica particles having an average particle size of 35 nm in pure water is used. However, the effects described above can also be achieved by using other polishing agents. Moreover, it is also possible to obtain the above effects without using the polishing agent temperature setting unit or the container temperature adjusting unit of Fig. 30, provided that the polishing agent 91 can be cooled immediately before it is supplied to the polishing pad 83 .

Example 10

FIG. 34 is a sectional view showing another example of the object to be polished by CMP using the polishing apparatus shown in FIG. 30. FIG. First, a SiO ₂ film 100 was prepared on a silicon substrate, and trenches (having a width of 1, 3, 5 and 10 μm to form interconnections were formed on the SiO ₂ film 100 by a normal photolithographic process DC magnetron sputtering made a 50 nm thick titanium nitride film 103 on the whole surface, and then a Cu film 104 was formed on the entire surface using DC magnetron sputtering, in which case the Cu film 104 was formed. that its thickness was 450 nm, that is, more than the height of the trench steps, thus producing the object 82 to be polished.

The resulting object 82 was placed on the sample holder 81 and treated with CMP. As the polishing pad 83 , a material prepared by attaching a polyurethane foam layer on a nonwoven fabric and having a total thickness of 1.5 mm and a Shore hardness of 66 to 88 was used. As the polishing agent 91 , a material prepared by dispersing 10% by weight of silica particles having an average particle size of 35 nm in pure water was used.

The polishing conditions were set as indicated below. It should be noted that the turntable temperature was kept constant by the table temperature setting unit 86 .

Polishing pressure: 300 g / cm ² Turntable Temperature: 25 ° C (room temperature) Polishing table rotating speed: 100 revolutions per minute Sample holder rotation speed: 100 revolutions per minute.

Under the above polishing conditions, the temperature of the polishing agent to be supplied was changed in accordance with conditions (1) and (2) in Example 9. Figs. 35 and 36 are graphs showing the relationship between the degree of inward curvature of the Cu interconnection and the polishing agent temperature and the relationship between the maximum surface roughness R _max on the Cu surface and the polishing agent temperature, respectively.

As shown in Fig. 35, the values for the degree of inward curvature under the conditions (1) were approximately the same as those under the conditions (2). In particular, the degree of inward curvature decreases as the temperature of the polishing agent is lower. Therefore, the degree of inward curvature of the object to be polished can be reduced by lowering the temperature of the polishing agent. Further, as shown in FIG. 35, when the polishing agent temperature is low, the maximum surface roughness R _max on the Cu surface after polishing is reduced by performing the temperature adjustment using the polishing agent supply pipe 89 .

Although the Cu film is used as the object to be polished in Practical Example 10 , the above-described effects can be obtained even when this Cu has a small amount of impurity. In addition, in Example 10, as the polishing agent for Cu, the material prepared by dispersing 10 wt% of silica particles having an average particle size of 35 nm in pure water is used. However, the effects described above can be achieved even when using other polishing agents.

In Examples 9 and 10, as the polishing pad, the Material used by attaching a foamed polyurethane layer on a non-woven Textile product is formed. It is also possible the above effects by using a Polishing pad to achieve, which consists of a non-woven Textile product consists, for example, polyester or Polyether, a polishing pad, which by means of execution a resin impregnation treatment for the nonwoven Textile product of this type is formed, and one Polishing pad, which by attaching two or more different types of cushion formed is, as long as only the polishing pad has a hardness, which corresponds to that of the polishing pad used in the above examples was used.

Example 11

Fig. 37 is a schematic view showing another example of the polishing apparatus according to Embodiment 4. The same reference numerals as in Fig. 30 denote corresponding parts in Fig. 37, and their repetition will be omitted. A liquid supply pump 111 is connected to a portion of a polishing agent supply pipe 89 between a polishing agent temperature adjusting unit 92 and a polishing agent storage container 87 . A pipe 110 for returning a polishing agent 91 to the polishing agent storage container 87 is connected to another portion of the polishing agent supply pipe 89 between the polishing agent temperature adjusting unit 92 and an injection port 90 . If a time period is long, ranging from a polishing process to the next, and during which no polishing is carried out, and the set temperature of Poliermitteltemperatureinstelleinheit 92 is low, the polishing agent can flocculate 91 and precipitate, which remains in the Poliermitteltemperatureinstelleinheit 92 of the polishing agent supply pipe 89 , Therefore, preferably, downstream of the polish temperature adjusting unit 92, there are provided valves V ₁ and V ₂ for performing switching by which the polishing agent 91 is either supplied to a polishing pad 83 or returned to the polish storage container 87 .

In actual polishing of an object to be polished in the polishing apparatus having the above arrangement, drive mechanisms rotate a sample holder 81 and a turntable. The sample holder 81 is moved down to press an object 82 to be polished against the polishing pad 83 with a predetermined load. In this state, the polishing is performed by supplying the polishing agent 91 from the injection port 90 of the polishing agent supply pipe 89 onto the polishing pad 83 . When polishing is not desired, in order to avoid variations in polishing properties caused by inhomogeneity of the polishing agent 91 or variations in the liquid supply rate, the liquid supply pump 111 is activated, and the valves V ₁ and V _{2 are} operated to apply the polishing agent 91 to the polishing agent 91 Polish storage container 87 to restore.

For forming buried interconnections of Al on a semiconductor substrate, the above-described polishing apparatus was used to perform CMP for the object to be polished, which is shown in FIG . Here, similar results as in Example 9 were obtained.

Example 12

The object to be polished shown in Fig. 31 was set on the sample holder 81 of the polishing apparatus shown in Fig. 30, and CMP was performed on the object. As the polishing pad 83 , a material prepared by attaching a polyurethane foam layer on a nonwoven fabric and having a total thickness of 1.5 mm and a Shore hardness of 66 to 88 was used. As the polishing agent 91 , a material prepared by dispersing 10% by weight of silica particles having an average particle size of 30 nm in an aqueous alkaline amine solution was used. The polishing conditions were set as indicated below. It should be noted that the turntable temperature was kept constant by the table temperature setting unit 86 .

Polishing pressure: 300 g / cm ² Turntable Temperature: 25 ° C (room temperature) Polishing table rotating speed: 100 revolutions per minute Sample holder rotation speed: 100 revolutions per minute.

Under the above polishing conditions, the temperature of the polishing agent to be supplied was changed as shown below. Here, the polishing agent 91 was supplied to the polish storage container 87 at 25 ° C (room temperature), and the temperature of the polisher storage container 87 was set to 25 ° C by the container temperature setting unit 94 . The polishing agent 91 stored in the polish storage container 87 was agitated by the propeller 88 . When the polishing agent 91 was supplied to the polishing pad 83 through the polishing agent supply pipe 89 , the temperature of the polishing agent 91 was changed between -1 and 80 ° C by the polishing agent temperature adjusting unit 92 .

FIGS. 38 and 39 are graphs showing the relationship between the degree of inward curvature of the Al interconnect and the polishing agent temperature and the relationship between the maximum surface roughness R _max on the Al surface and the slurry temperature, respectively, when shown in FIG , object to be polished was polished under the conditions mentioned above.

As shown in Fig. 38, the degree of inward curvature decreases as the temperature of the polishing agent is lower. Therefore, the degree of inward curvature of the object to be polished can be reduced by lowering the temperature of the polishing agent. This effect was remarkable when a polishing agent having the properties of a colloid was used. Such a colloidal fluid generally exhibits a property called dilatancy, the actual viscosity coefficient not obeying Newton's law of viscosity, but increasing with increasing shear force. It is believed that by this dilatancy, the polishing particles held by a liquid, which is actually in the form of a gel, mechanically remove the object to be polished in units of micro dimensions. Therefore, it can be considered that the strongest reason for the effect of suppressing the inward curvature by lowering the temperature of the polishing agent as in this embodiment is that the above-described polishing mechanism has a temperature dependency and this enhances the dilatancy at low temperatures.

In general, when considering an RC delay in interconnections of an LSI, a reduction in the sectional area of an interconnect caused by an inward curvature must be reduced to about 10%. For this reason, the temperature range of a suitable polishing agent changes according to the thickness or shape of an intermediate compound of interest. Therefore, in the formation of a buried interconnect having a thickness of 0.4 μm and a width of 0.4 to 10 μm using a 50 nm-thick polishing resistor film, for example, the degree of inward curvature needs to be about 130 nm or less. Therefore, it is clear from Fig. 38 that the temperature of the polishing agent must be lowered to 15 ° C or less. As shown in Fig. 38, moreover, the inward curvature can be further suppressed by setting the temperature of the polishing agent near the freezing point, that is, from -1 to 5 ° C.

Fig. 39 shows that by using the polishing agent of the above-mentioned kind, the maximum surface roughness _Rmax on the Al surface after polishing was kept at a value at which no difficulties in reliability of the interconnections occurred regardless of the temperature of the polishing agent ,

In Example 12, Al may contain a small proportion of an impurity. For example, the above-described effects can be obtained even when a film composed of an Al alloy containing 1.0 wt% of Si or 1.0 wt% of Cu is used as the object to be polished. Moreover, although the polishing agent containing only silica particles on polishing particles is used in Practical Example 12 , it is also possible to use a polishing agent containing silica particles and particles of substance other than polishing particles. In this case, preferably, the pH of the polishing agent is 7.5 or more, and the particle size of the polishing particles is 100 nm or less.

Example 13

The object to be polished shown in Fig. 34 was set on the sample holder 81 of the polishing apparatus shown in Fig. 30, and CMP was performed on the object. As the polishing pad 83 , a material prepared by attaching a polyurethane foam layer on a non-woven fabric and having a total thickness of 1.5 mm and a Shore hardness of 66 to 88 was used. As the polishing agent 91 , a material prepared by dispersing 20% by weight of silica particles having an average particle size of 30 nm in hydrogen peroxide water to which an oxidizing agent was added was used. The polishing conditions were set as indicated below. It should be noted that the turntable temperature was kept constant by a table temperature setting unit 86 .

Polishing pressure: 300 g / cm ² Turntable Temperature: 25 ° C (room temperature) Polishing table rotating speed: 100 revolutions per minute Sample holder rotation speed: 100 revolutions per minute.

Figs. 40 and 41 are graphs showing the relationship between the degree of inward curvature of the Cu interconnect and the slurry temperature and the relationship between the maximum surface roughness R _max on the Cu surface and the slurry temperature, respectively. As shown in Fig. 40, the degree of inward curvature decreases as the temperature of the polishing agent is lower. Therefore, the degree of inward curvature of the object to be polished can be reduced by lowering the temperature of the polishing agent. This effect occurs when the polishing agent has the properties of a colloid. In addition, Fig. 41, as in the above-described Example 12, shows that when the polishing agent of the above-described kind was used, the maximum surface roughness R _max on the Al surface after polishing was kept at a level with no difficulty with respect to the reliability of the intermediates, regardless of the temperature of the polish.

In Example 13, the Cu film becomes an object to be polished used. However, the above can be Effects also achieve when the Cu takes a small share having an impurity. In addition, in the Examples 12 and 13 uses a material as a polishing pad, which by attaching a foamed Polyurethane layer on a nonwoven fabric will be produced. It is also possible to use the above To achieve the effects described by a Polishing pad is used, which consists of a non-woven Textile product consists, for example, polyester or Polyether, or a polishing pad, which means  Conduction of a curative resin impregnation treatment for the Nonwoven fabric of this kind is manufactured, or a polishing pad, which by fastening two or made of several different types of pillows, as long as only the polishing pad has a hardness which that of the polishing pad that corresponds to the above examples was used.

It should be noted that the embodiments 1 to 4 of the present invention in the form of suitable combinations can be performed with each other. Both The above examples use polishing of Al or Cu as an object to be polished. However, the present invention is also then effective when polishing using Ag performed, which likewise a soft metal similar Al represents as an object to be polished. In addition, it is the present invention is effective even on a substrate on its surface trenches with different widths are provided. As the above-mentioned substrate can a substrate having trenches, the on a surface of an insulating film on one Semiconductor substrate are provided for burying a Wiring material, or a substrate (a Phase shift mask, an X-ray mask) which Has trenches on a transparent (insulating) Substrate are provided to a light-absorbing material (for a visible ray of light, ultraviolet light or X-rays), such as Cr, W, to bury. Other modifications of the present invention can be made also perform without departing from the spirit of the invention departing.

Experts in this field will have additional benefits and Changes easily noticeable. Therefore, the invention is in  their overall aspect is not limited to the specific details, representative devices, and illustrated examples limited, which have been shown and described here. Therefore Various modifications can be made without leaving Nature or scope of the general inventive concept deviate from the totality of the present Registration documents, in particular by the attached Claims and their equivalents.

Claims (20)

1. polishing method, characterized by the following steps:
Forming a film to be polished having Al as a main component on a substrate having a recessed portion in one of its surfaces so as to fill at least the recessed portion; and
selectively leaving the film to be polished in the recessed portion by polishing the film using a polishing agent having polishing particles and a solvent, and having a pH of not less than 7.5. 2. The method according to claim 1, characterized in that a Particle size of the polishing particles is not greater than 100 nm. 3. The method according to claim 1, characterized in that the Polierteilchen contain polishing particles, the Siliceous earth exist. 4. The method according to claim 1, characterized in that the Solvent contains at least one material which is selected from the group consisting of ammonia, a Amine, a sodium hydroxide and a potassium hydroxide consists.   5. The method according to claim 1, characterized in that the Polishing agent is cooled to not more than 15 ° C. 6. polishing method, characterized by the following steps:
Forming a film to be polished on a substrate, in the one surface of which a recessed portion is provided so as to fill at least the recessed portion; and
selectively leaving the film to be polished in the recessed portion by polishing the film by using a polishing agent containing a solution for etching the film to be polished, a corrosion preventing agent for the film to be polished, and polishing particles. 7. The method according to claim 6, characterized in that the polishing film contains at least one element which is selected from the group consisting of Al, Cu and Ag exists as a main component. 8. The method according to claim 6, characterized in that the Polishing film is a film which Al as Main component contains, and that the solution one pH of not less than 7.5. 9. The method according to claim 6, characterized in that the Polierteilchen silica particles with a Have particle size of not more than 100 nm.   10. The method according to claim 6, characterized in that the solution contains at least one material selected from the group selected from ammonia, an amine, a Sodium hydroxide, and a potassium hydroxide. 11. The method according to claim 6, characterized in that the Corrosion preventing at least one material the group consisting of silicate and chromate. 12. The method according to claim 6, characterized in that the Corrosion preventing agent is formed by that the solution reacts with the polishing particles. 13. The method according to claim 6, characterized in that the Polierteilchen contain silica particles, and that the Anticorrosive Silicate and Contains silica particles which are negatively charged. 14. The method according to claim 6, characterized in that the polishing agent is cooled to not more than 15 ° C. 15. Polishing device, characterized by:
a polishing agent storage container for storing a polishing agent;
a turntable for polishing an object to be polished;
a polishing agent supply pipe for supplying the polishing agent from the polishing agent storage container onto the turntable;
a polishing object jig for holding the object to be polished so that a surface of the object to be polished faces the turntable; and
a first temperature adjusting means for adjusting the temperature of the polishing agent in the polishing agent supply pipe. 16. The device according to claim 15, characterized in that the first Temperature adjustment a Temperature adjustment for lowering the Temperature of the polishing agent to a temperature below that of the polish in the Polish storage tank is. 17. The device according to claim 15, characterized in that above In addition, a second temperature adjustment is provided to the temperature of the polishing agent in to adjust the polish storage container. 18. Device according to claim 17, characterized in that the first Temperature adjustment and the second Temperature adjustment independently be controlled or regulated. 19. Device according to claim 15,  characterized in that further a third temperature adjusting device for Setting the temperature of the turntable provided is. 20. Device according to claim 15, characterized in that further means for recycling the polishing agent, which passes through the polishing agent supply pipe, to the Poliermittelspeicherbehälter is provided.