US20050003743A1

US20050003743A1 - Slurry for CMP, polishing method and method of manufacturing semiconductor device

Info

Publication number: US20050003743A1
Application number: US10/844,441
Authority: US
Inventors: Gaku Minamihaba; Yukiteru Matsui; Hiroyuki Yano
Original assignee: Individual
Current assignee: Toshiba Corp
Priority date: 2003-05-14
Filing date: 2004-05-13
Publication date: 2005-01-06
Also published as: CN1551304A; JP2004342751A; CN1295758C; TW200509184A; TWI252506B

Abstract

There is disclosed a CMP slurry comprising composite type particles composed of a resin component and an inorganic component, which are complexed with each other, and resin particles, the CMP slurry having a viscosity of less than 10 mPas.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-136014, filed May 14, 2003, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a slurry to be used for CMP (Chemical Mechanical Polishing), a polishing method using the slurry, and a method of manufacturing a semiconductor device.
2. Description of the Related Art
It is expected that the integration of semiconductor elements in high performance LSIs of the next generation will inevitably be further enhanced. For example, the design rule of damascene wirings to be formed by CMP is expected to become so severe that the line width of wirings is confined within the range of 0.07 to 30 μm and the film thickness of wirings is confined to 100 nm or less.
When formation of damascene wirings having a film thickness of 100 nm is attempted by the conventional CMP, abrasive grains detached from a polishing pad during polishing become free particles which are subsequently thrusted into a surface to be polished (which may be referred hereinafter to “a polishing surface”), which generates a dishing having a depth of about 80 nm. If such is the case, most of the wiring material (Cu, Al, W, etc.) buried inside a trench is undesirably removed from the trench. If the dishing becomes excessive, the electric resistance of the wirings increase, thereby deteriorating the performance of a semiconductor device. Additionally, there is also a possibility of generating the disconnection of wirings during the operation of the LSI, thereby deteriorating the reliability of the semiconductor device. Therefore, it is required to control the size of the dishing to 20 nm or less.
It has been conventionally considered that the aforementioned requirement can be coped with by minimizing the ratio of released the free particles during the polishing, and hence, it has been conventionally proposed to employ a method to employ a fixed abrasive grain type CMP pad (for example, a fixed abrasive type CMP pad which is available from 3M Co., Ltd.) where the generation of free particles can be minimized. Although it may be possible to control the size of the dishing to 20 nm or less by using such a CMP pad, there are still left remained problems such as working efficiency, manufacturing cost, the quality of a worked surface and the stability of products.
There is also proposed a method which enhance the interaction between abrasive grains and a polishing pad. For example, it is proposed to employ a slurry comprising composite particles as polishing grains, and an organic compound such as a surfactant or an organic acid. However, the employment of this slurry is impractical due to poor polishing efficiency thereof.

BRIEF SUMMARY OF THE INVENTION

A CMP slurry according to one aspect of the present invention comprises composite type particles comprising a resin component and an inorganic component, which are complexed with each other; and resin particles, the CMP slurry having a viscosity of less than 10 mPas.
A polishing method according to another aspect of the present invention comprises contacting a polishing surface of the semiconductor substrate with a polishing pad attached to a turntable; and dropping a CMP slurry onto the polishing pad to polish the polishing surface of the semiconductor substrate, the CMP slurry having a viscosity of less than 10 mPas and comprising composite type particles composed of a resin component and an inorganic component, which are complexed with each other, and resin particles.
A method of manufacturing a semiconductor device according to a further aspect of the present invention comprises forming an insulating film above a semiconductor substrate; forming a recessed portion in the insulating film; depositing a conductive material inside the recessed portion and on the insulating film to form a conductive layer; and removing the conductive material deposited on the insulating film by CMP using a CMP slurry to expose the surface of the insulating film while selectively leaving the conductive material in the recessed portion, the CMP slurry having a viscosity of less than 10 mPas and comprising composite type particles composed of a resin component and an inorganic component, which are complexed with each other, and resin particles.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram schematically illustrating a state of the cross-section of composite type particles and resin particles;
FIGS. 2A and 2B are cross-sectional views respectively illustrating a top ring;
FIGS. 3A and 3B are cross-sectional views each illustrating, in stepwise, the method of manufacturing a semiconductor device according to one embodiment of the present invention;
FIG. 4 is a perspective view schematically illustrating a state of CMP;
FIG. 5 is a graph illustrating the relationship between the polishing rate of W film and the mixing ratio of resin particles in slurry;
FIGS. 6A to 6C are cross-sectional views each illustrating, in stepwise, the method of manufacturing a semiconductor device according to another embodiment of the present invention; and
FIGS. 7A and 7B are cross-sectional views each illustrating, stepwise, the method of manufacturing a semiconductor device according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Next, the embodiments of the present invention will be explained with reference to drawings.
It has been discovered by the present inventors that, to minimize the dishing or erosion of the polishing surface of a semiconductor substrate in the polishing process thereof where a slurry that has been supplied to a polishing pad is employed for effectively applying it to the polishing surface, it is effective to employ mixed particles comprising composite type particles and resin particles, and to confine the viscosity of the slurry to less than 10 mPaS.
FIG. 1 is a diagram schematically illustrating the composite type particles and the resin particles. The composite type particles 10 are composed of polymer particles constituting a resin component 11, and
an inorganic component 12 which is complexed with the polymer particles. By the term “complexation”, it indicates a chemical bonding or non-chemical bonding. The inorganic component 12 may be, for example, a silicon compound moiety or a metal compound moiety. The inorganic component 12 may be bonded to the surface of the resin component 11 as shown in FIG. 1 or entrapped in the resin component 11. On the other hand, the resin particles 13 should preferably be provided, on the surface thereof, with a functional group such as COOH.
As for the composite type particles 10, it is possible to employ those described in U.S. Pat. No. 6,454,819 for instance. Generally, the composite type particles 10 can be synthesized by the following process. Namely, first of all, a silane coupling agent is linked to the particles of divinylbenzene polymer constituting the resin component 11, and the resultant material is allowed to react with a specific kind of silane alkoxide or with colloidal silica. In this manner, a silicon compound moiety having a polysilane structure is formed, as the inorganic component 12, inside the polymer particles as well as on the surface of the polymer particles. The silicon compound moiety may be formed without necessitating the employment of the silane coupling agent. The inorganic component should preferably be linked, directly or through a silane coupling agent, to the polymer particles. Further, it is also possible to employ metals such as aluminum, titanium or zirconium for constituting the inorganic component 12 to obtain the composite type particles 10 having the same structure as described above.
Next, details of polymer particles as the resin component 11 in the composite type particles 10 will be explained as follows.
The polymer particles are formed of particles consisting of a polymer that can be obtained through the polymerization of various monomers. As for the monomers, it is possible to employ unsaturated aromatic compounds such as styrene, α-methyl styrene, styrene halide and divinylbenzene; unsaturated esters such as vinyl acetate and vinyl propionate; and unsaturated nitriles such as acrylonitrile. It is also possible to employ as the monomers, acrylic esters or methacrylic esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, glycidyl acrylate, glycidyl methacrylate, 2-hydroxy ethylacrylate, acrylacrylate and acrylmethacrylate.
It is also possible to employ, as the monomers, butadiene, isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methyrol acrylamide and N-methyrol methacrylamide. These monomers can be employed singly or in combination of two or more.
The polymer particles can be obtained through the polymerization of these monomers using various methods including emulsion polymerization, suspension polymerization and dispersion polymerization. It is possible, through suitable controlling of polymerization conditions, to optionally adjust the particle diameter of the polymer particles. Further, it is also possible to obtain polymer particles of desired particle size through the pulverization of bulky polymer particles. In particular, if it is desired to obtain polymer particles which are excellent in mechanical strength and in heat resistance, is a polyfunctional monomer may be co-used in the manufacture of the polymer particles to introduce a crosslinked structure into the molecule of polymer particles. The crosslinked structure may be introduced into the molecule of polymer particles by chemical crosslinking or electron radiation crosslinking during or after the manufacture of polymer particles.
Although there is no particular limitation with respect to the configuration of polymer particles, the configuration of polymer particles should preferably be as spherical as possible. As for the average particle diameter of the polymer particles when they are assumed as being spherical, it is preferable to confine it to the range of 0.03 to 100 μm, more preferably the range of 0.05 to 20 μm, most preferably the range of 0.05 to 1.0 μm. If this average particle diameter is less than 0.03 μm, it would become difficult to secure a sufficient polishing performance due to an insufficient particle size of the polymer particles. On the other hand, if this average particle diameter exceeds over 100 μm, the dispersibility of the composite type particles would be deteriorated, thereby greatly deteriorating the storage stability of the composite type particles.
It is preferable to introduce a functional group such as hydroxyl group, epoxy group, carboxyl group, etc. into the polymer particles obtained in this manner. In that case, an inorganic component can be directly linked to the polymer particles without necessitating the intervention of a coupling compound such as a silane coupling agent, etc. When a silane coupling agent having a functional group which is capable of reacting with a functional group that has been introduced into the polymer particles is co-used, the linkage between the inorganic component and the polymer particles would be further promoted, thus making it possible to obtain a composite type particles which is capable of exhibiting more excellent performance.
As for the polymer particles, it is possible to employ particles consisting of various polymers such as polyamide, polyester, polycarbonate, polyolefin, etc. In the same manner as described above, even in the case of these polymer particles, functional groups as described above can be introduced into the polymer particles and at the same time, a crosslinked structure can be also introduced into the polymer particles.
As described above, although it is possible to employ various polymers, the employment of polymethylmethacrylate (PMMA) and polystyrene (PST) is especially preferable as these compounds are easily available in the industries concerned.
Next, the silicon compound moiety and the metal compound moiety, both constituting the inorganic component 12, will be explained in detail as follows. In this composite type particles, the inorganic component is at least partially linked directly or indirectly to the polymer particles. However, the inorganic component should preferably be linked chemically to the polymer particles in order to obviate the generation of the problem that the inorganic component is easily detached from the polymer particles during the polishing step and remains on the polishing surface of substrate. As for the chemical linkage, it may be of any kind, including ionic bond and coordinate bond, but preferably a covalent bond, in view of achieving a stronger bond between the inorganic component and the polymer particles. Alternatively, the inorganic component 12 may be linked to the polymer particles through a non-chemical bonding such as a hydrogen bond, surface charge bond, interlocking bond and anchor effect bond.
In order to enable the inorganic component to bond onto the surface of the resin component 11 as shown in FIG. 1, the inorganic component is required to be smaller in particle size than that of the polymer particles. It has been determined through calculation that as long as the longest diameter of the inorganic component is not larger than about ¼ of the particle diameter of the polymer particles, the inorganic component is possible to link uniformly to the surface of the resin component 11. However, in order to secure desirable polishing power of the inorganic component, the longest diameter of the inorganic component should preferably be 10 nm or more.
The silicon compound moiety constituting the inorganic component may be constituted by at least either one of the siloxane bond-containing portion and the silica particle portion. Further, the metal compound moiety can be constituted by at least one selected from the group consisting of metalloxane bond-containing portion, alumina particle portion, titania particle portion and zirconia particle portion.
These inorganic components may exist in the inside as well as on the entire surface of the polymer particles. Alternatively, these inorganic components may exist partially in the inside and on the surface of the polymer particles. The siloxane bond-containing portion and the silica particle portion may be constituted by a monomolecule, but should preferably be constituted by a chain structure comprising two or more molecules. This chain structure may be formed of a linear structure, but should preferably be formed of a three-dimensional structure.
The inorganic component may be linked directly or via a coupling compound such as a silane coupling agent to the polymer particles. As for specific examples of the coupling compound, it is possible to employ a silane coupling agent, an aluminum-based coupling agent, a titanium-based coupling agent and a zirconium-based coupling agent. Among them, the silane coupling agent is most preferable. As for specific examples of the silane coupling agent, they include the following groups of compounds (a), (b) and (c).
(a) Vinyl trichlorsilane, vinyl tris(β-methoxy) silane, vinyl triethoxy silane, vinyl trimethoxy silane, γ-methacryloxy propyltrimethoxy silane, γ-mercaptopropyl trimethoxy silane, and γ-chloropropyl trimethoxy silane.
(b) γ-glycidoxypropyl trimethoxy silane, and γ-glycidoxypropyl methyldiethoxy silane.
(c) N-β(aminoethyl) γ-aminopropyltrimethoxy silane, N-β(aminoethyl) γ-aminopropylmethyl dimethoxy silane, and γ-aminoropropyl trimethoxy silane.
As for specific examples of the silane coupling agent, it is preferable to employ those having a functional group which is capable of easily reacting with the functional group that will be introduced into the polymer particles. For example, in the case of the polymer particles having carboxyl group introduced into the surface thereof, it is preferable to employ silane coupling agents of the aforementioned groups (b) and (c) having epoxy group or amino group. Among them, γ-glycidoxypropyl trimethoxy silane and N-β(aminoethyl) γ-aminopropyltrimethoxy silane are most preferable.
As for specific examples of the aluminum-based coupling agent, they include acetalkoxy aluminium diisopropylate, etc. As for specific examples of the titanium-based coupling agent, they include isopropyl triisostearoyl titanate, isopropyl tridecylbenzene sulfonyl titanate, etc. These various coupling agents may be used singly or in combination of two or more. Further, it is also possible to employ different coupling agents other than those mentioned above.
The mixing ratio of the coupling agents should preferably be confined to 0.1 to 50 moles per mole of functional group to be introduced into the polymer particles. More preferably, this mixing ratio should be confined to 0.5 to 30 moles, most preferably 1.0 to 20 moles per mole of the functional group. If the mixing ratio of the coupling agents is less than 0.1 mole, it would be impossible to bond the inorganic component sufficiently strongly to the polymer particles, thereby the inorganic component falls easily from the polymer particles during the polishing step. On the other hand, if the mixing ratio of the coupling agents exceeds over 50 moles, the condensation reaction of the molecules of coupling agent would proceed, thus generating undesirable polymers. If such is the case, the linkage of the inorganic component to the polymer particles would be obstructed.
On the occasion of chemically bonding a coupling agent to the polymer particles, the chemical reaction can be promoted by using a catalyst such as acids or bases. Further, the chemical reaction can be also promoted by increasing the temperature of reaction system.
The compounds represented by the following general formula (1) can be employed as a raw material for the inorganic component.
R_nM(OR′)_Z−n (1)
In this formula (1), R, R′, M, z and n are defined as follows.
Namely, R is a monovalent organic group having 1 to 8 carbon atoms such as alkyl group including methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl and n-pentyl, phenyl group, vinyl group, and glycidepropyl group; and R′ is alkyl group having 1 to carbon atoms, acyl group having 2 to 6 carbon atoms, or aryl group having 6 to 9 carbon atoms. Specific examples thereof include methyl, ethyl, n-propyl, iso-propyl, acetyl group, propionyl group, butyryl group, valeryl group, caproyl group, phenyl group, and tolyl group.
If the number of each of R and R′ is 2 or more, each of Rs and R′s may be the same with or different from each other in kind.
M is selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Sn, Sb, Ta, W, Pb and Ce. Among them, Al, Si, Ti and Zn are more preferable.
z is the valence number of M; and n is an integer ranging from 0 to (z−1).
Next, the compounds containing Al, Si, Ti or Zn as the aforementioned M will be further explained. As for specific examples of the compounds where Si is included as this M, they include tetramethoxy silane, tetraethoxy silane (TEOS), tetra-iso-propoxy silane, tetra-tert-butoxy silane, methyltrimethoxy silane and methyltriethoxy silane. The silicon compound moiety representing the inorganic component can be constituted by these compounds. Further, as for specific examples of the compounds where Al is included as this M, aluminum ethoxide, etc. may be mentioned; as for specific examples of the compounds where Ti is included as this M, titanium(IV) ethoxide, etc. may be mentioned; and as for specific examples of the compounds where Zn is included as this M, zirconium-tert-butoxide, etc. may be mentioned. By using these compounds, metalloxane bond-containing portion, alumina particle portion, titania particle portion and zirconia particle portion, each representing the inorganic component, can be formed.
The aforementioned compounds may be employed singly or in combination of two or more. Further, compounds where the aforementioned M is constituted by Al, Si, Ti or Zn can be co-used. The compounds represented by the aforementioned general formula (1) where (z−n) is 2 or more are more preferable since they are capable of forming siloxane bond-containing portion or metalloxane bond-containing portion, both of which are more excellent in denseness.
In addition to the compounds represented by the aforementioned general formula (1), it is also possible to employ at least either one of the hydrolyzates and partial condensates thereof may be used. The compounds represented by the aforementioned general formula (1) are capable of undergoing hydrolysis or partial condensation without necessitating any special procedure. However, if required, a predetermined ratio of the compounds may be subjected in advance to hydrolysis or partial condensation.
The mixing ratio of these compounds (calculated as SiO₂, Al₂O₃, TiO₂or ZrO₂) should preferably be confined to the range of 0.001 to 100, more preferably 0.005 to 50, most preferably 0.01 to 10 based on the weight of the polymer particles. If this weight ratio is less than 0.001, it would become impossible to sufficiently create the inorganic component in the inside as well as on the surface of the polymer particles, thereby deteriorating the polishing performance of CMP slurry. On the other hand, even if this weight ratio is increased over 100, it would be difficult to expect a remarkable enhancement of the polishing performance.
Further, at least one inorganic material selected from the group consisting of colloidal silica, colloidal alumina, colloidal titania and colloidal zirconium may be employed as a raw material for the inorganic component. These colloidal components can be prepared by dispersing silica, alumina, titania or zirconia fine particles having an average particle diameter ranging from 5 to 500 nm in a dispersion medium such as water. These fine particles can be prepared by a method where particles grow in an alkali aqueous solution or by a vapor-phase method.
These fine particles may be bonded via the aforementioned siloxane bond-containing portion or metalloxane bond-containing portion to the polymer particles. Alternatively, by using a hydroxyl group that has been introduced into these fine particles, these fine particles can be bonded to the polymer particles, siloxane bond-containing portion or metalloxane bond-containing portion, thus constructing each of the particle portions.
The mixing ratio of these colloids (calculated as SiO₂, Al₂O₃, TiO₂or ZrO₂) should preferably be confined to the range of 0.001 to 100, more preferably 0.01 to 50, most preferably 0.01 to 10 based on the weight of the polymer particles. If this weight ratio is less than 0.001, it would become impossible to sufficiently form the inorganic component. On the other hand, even if this weight ratio is increased over 100, it would be impossible to expect any further enhancement of the polishing performance.
In the process of causing the aforementioned components to react with the polymer particles, the process can be performed in a dispersion system where water or various organic solvent such as alcohol are employed as a dispersion medium. These dispersion mediums may be employed singly or in combination of two or more. When a dispersion medium containing water is employed, it is preferable to introduce in advance a hydrophilic functional group such as hydroxyl group, epoxy group and carboxylic group into the polymer particles, thereby enabling the polymer particles to stably and uniformly disperse in the dispersion system. It becomes possible, through the introduction of these functional groups, to enable the aforementioned inorganic component to more easily bond to the polymer particles.
As for specific examples of the alcohols that can be employed as a dispersion medium, they include lower saturated aliphatic alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, etc. These alcohols may be employed singly or in combination of two or more. As for specific examples of organic solvents other than alcohols, they include for example methylethyl ketone and dimethyl formamide. These organic solvents, water and alcohols can be used as a mixture by mixing them at a predetermined ratio.
On the occasion of effecting the reaction between the organic component and the polymer particles, the content of the polymer particles in the dispersion medium should preferably be confined within the range of 0.001 to 70% by weight, more preferably 0.01 to 50% by weight, most preferably 0.1 to 25% by weight. If the content of the polymer particles is less than 0.001% by weight, it would become difficult to obtain composite type particles at a sufficient yield. On the other hand, if the content of the polymer particles exceeds over 70% by weight, the dispersion stability of the polymer particles would be deteriorated, thus raising the problem that gel is liable to generate in the step of forming the composite.
The reaction to bond the inorganic component to the polymer particles can be promoted by heating or by the addition of a catalyst. If the reaction is to be promoted by heating, the temperature of the reaction system should preferably be confined within the range of 40 to 100° C. As for the catalysts to be employed in this case, it is possible to employ acids, bases, aluminum compounds and tin compounds. Among them, the employment of acid catalysts and aluminum catalysts is more preferable in view of their prominent reaction promoting effects.
Further, it is also possible to employ composite type particles which can be produced through the heat adhesion to be effected by a mechanofusion phenomenone. These composite type particles are described for example in U.S. Pat. No. 6,576,554 B2 (incorporated herein by reference).
In the embodiment of the present invention, various composite type particles as described above can be employed.
On the other hand, as for the resin particles 13, it is possible to employ those described in JP Laid-open Patent Publication (Kokai) No.2000-204275. More specifically, the resin particles 13 can be constituted by the same materials as those employed for the resin component of the aforementioned composite type particles, the configuration of the resin particles 13 being preferably spherical. “Spherical” in this case means “approximately spherical” in configuration which is free from any acute angle and hence, the resin particles 13 is not necessarily completely spherical.
The resin particles should preferably be comprising a cross-linking structure, which can be synthesized for example through a copolymerization between a cross-linking monomer and other monomers. In this copolymerization, the mixing ratio of the cross-linking monomer should preferably be confined within the range of 5 to 80% by weight, more preferably 5 to 60% by weight, most preferably 7 to 60% by weight. If the mixing ratio of the cross-linking monomer is less than 5% by weight, it would become difficult to obtain resin particles having a sufficient hardness. On the other hand, if the mixing ratio of the cross-linking monomer exceeds over 80% by weight, the resultant resin particles would become fragile even though the hardness thereof can be increased. It is possible, through the creation of the aforementioned cross-linking structure, to enhance not only the hardness but also the mechanical strength of the resin particles.
The resin particles should preferably be constructed such that a hydrophilic group is disposed as a functional group on the surface thereof. By the provision of hydrophilic group as mentioned above, the polarity of ζ-potential of the surface of resin particles can be controlled and at the same time, various properties such as antistatic property, heat resistance and discoloration resistance of the resin particles can be enhanced in addition to the enhancement of the hardness and mechanical strength thereof. Moreover, the resin particles having a hydrophilic group on their surfaces are also excellent in compatibility with the compounds having a polar group.
The resin particles having a hydrophilic group on their surfaces can be manufactured by introducing not less than 0.1 millimol, more preferably 1 to 100 millimoles, based on 100 g of the resin particles, of a hydrophilic group such as hydroxyl group, carboxyl group or salts thereof, acid anhydride group, sulfonic acid group or salts thereof, phosphoric acid group or salts thereof, and amino group or salts thereof.
It is also possible to separately incorporate a surfactant having a predetermined hydrophilic group into the slurry so as to enable the hydrophilic group to bond onto the surface of the resin particles. As for specific examples of the surfactant, it is possible to employ a cationic surfactant, an anionic surfactant or nonionic surfactant. As for specific examples of the cationic surfactant, they include, for example, aliphatic amine salts and aliphatic ammonium salts. As for specific examples of the anionic surfactant, they include, for example, fatty acid soap; carboxylate such as alkylether carboxylate; sulfonate such as alkylbenzene sulfonate, alkylnaphthalene sulfonate and α-olefin sulfonate; sulfate ester such as higher alcohol sulfate ester, alkylether sulfate and polyoxyethylene alkylphenyl ether; and phosphate ester such as alkylphosphate ester. As for specific examples of the nonionic surfactant, they include, for example, ether type surfactant such as polyoxyethylene alkylether; ether ester type surfactant such as polyoxyethylene ether of glycerin ester; and ester type surfactant such as polyethylene glycol fatty acid ester, glycerate and sorbitan ester.
The slurry according to one embodiment of the present invention can be prepared by selecting the aforementioned composite type particles and the aforementioned resin particles such that polarities of these particles are combined in predetermined manner, and by dispersing these particles in water. More specifically, the composite type particles and the resin particles are combined with each other such that the surfaces of these particles become the same in polarity with each other.
The aforementioned ζ-potential can be measured by using a laser Doppler type ζ-potential measuring apparatus (BROOKHAVEN INSTRUMENTS Co., Ltd.; product name “Zeta Plus”). In the measurement of the ζ-potential, a dispersion of predetermined pH is prepared in advance by dispersing the inorganic component in water. The ζ-potential of the inorganic component at any pH value can be determined by measuring this dispersion by using the aforementioned zeta-potential measuring apparatus. The measurement of the ζ-potential of a functional group can be performed as follows. Namely, the functional group aimed at is bonded onto the surface of the resin particles and the resultant resin particles are dispersed in water for instance to obtain a solution of a predetermined pH. Subsequently, the solution is measured in the same manner as described above.
The polarity of the composite type particles is dependent on the kind of the inorganic component. For example, the ζ-potential of silica is zero (isoelectric point) at pH=1.4, but becomes minus at a pH exceeding 1.4. The ζ-potential of alumina is zero at pH=7, but becomes plus at a pH of less than 7.
On the other hand, with respect to the resin particles, the ζ-potential thereof can be determined depending on the functional group existing on the surfaces of the resin particles. For example, in the case of carboxylic group (COOH), there is no isoelectric point and the ζ-potential thereof is minus at every pH regions (0.5 to 14). The ζ-potential of amino group (NH₂) is plus at every pH region.
Alternatively, either one of the composite type particles and the resin particles may be of isoelectric point. The isoelectric point in this case means that the value of ζ-potential as measured by using the aforementioned zeta-potential measuring apparatus is confined within the range of 0±5 mV. When the value of pH where the ζ-potential becomes zero is taken as a basis, even if pH is fluctuated by the range of ±1, the electric potential of the surface of the particles becomes unstable. Accordingly, this range can be dealt with as an isoelectric point. For example, the ζ-potential of polystyrene particles having a sulfonic acid group (SO₃H) as a functional group is approximately zero in the vicinity of pH=2. Namely, the composite type particles and the resin particles are employed in such a combination that the surfaces thereof would not become opposite in polarity from each other.
When the slurry contains, as abrasive grains,
a mixture comprising the composite type particles and the resin particles both being opposite in polarity from each other, these two kinds of particles are electrically strongly attracted to each other, thereby generating flocculation, thus greatly increasing the viscosity of the slurry up to more than 10 mPaS. The slurry having such a high viscosity is incapable of dropping it on a polishing pad to carry out the CMP of a polishing surface. Namely, the slurry supply system currently employed is a liquid circulation type using a pump, so that if a slurry of high viscosity is employed, the clogging of slurry would be caused. Furthermore, since a slurry of high viscosity is poor in storage stability, the slurry would be easily sedimented and, once sedimented, cannot be redispersed.
In order to restrict the viscosity of the slurry to less than 10 mPaS, the composite type particles and the resin particles having the same polarity with each other should be selected. Even if either one of the composite type particles and the resin particles is adjusted to isoelectric point, the viscosity of the slurry should be limited to less than 10 mPaS.
Irrespective of the combination of the composite type particles and the resin particles, the particle diameter of the resin particles should preferably be larger than the longest diameter of the inorganic component of the composite type particles.
More specifically, the particle diameter of the resin particles should preferably be not less than twice as large as the longest diameter of the inorganic component. As explained above, with respect to the composite type particles, the particle diameter of the inorganic component thereof should preferably be not larger than ¼ of that of the resin component. Further, the particle diameter of the composite type particles should preferably be not less than twice as large as the particle diameter of the resin particles. In order to enable the resin particles to become the substituent particles for the resin component of the composite type particles when the composite type particles are deformed or destroyed during the process of CMP, the size of the resin particles should preferably be at least larger than that of the inorganic component. If these factors are taken into consideration, the particle diameter of the resin particles should preferably be not less than twice as large as the inorganic component of the composite type particles. However, in order to secure a satisfactory polishing power, the longest diameter of the inorganic component should preferably be 100 nm or more. Further, when the interaction of the resin particles with the polishing pad is taken into consideration, it is especially preferable that the particle diameter of the resin particles be confined at most to about 300 nm.
In order to secure a higher polishing rate, the ratio of particle diameters (d₁/d₂) between an average particle diameter d₁of the composite type particles and an particle diameter d₂of the resin particles should preferably be 2 or more. It is possible, through the control of the ratio of particle diameters, to achieve a desired polishing rate. However, in order to sufficiently secure the effect of mixing the particles, the upper limit of the ratio of particle diameters is confined to about 10. The reason for this is that if the particle diameter of the resin particles is too small as compared with that of the composite type particles, it may conceivably become close to the situation where a surfactant of small volume is incorporated in the slurry.
An average particle diameter of the resin particles should preferably be confined within the range of 0.05 to 1 μm. If an average particle diameter of the resin particles is less than 0.05 μm, it may become difficult to obtain a spherical body. On the other hand, if an average particle diameter of the resin particles exceeds 1 μm, an average diameter of the composite type particles would exceed 2 μm as the aforementioned ratio of particle diameters (d₁/d₂) is set to 2 or more. In this case, the polishing power may become insufficient due to the decrease of the surface area of the particles. Incidentally, an average particle diameter of the resin particles should more preferably be confined to the range of 0.1 to 0.5 μm, most preferably 0.1 to 0.3 μm. These average diameters of the composite type particles and the resin particles can be determined through the observation by TEM.
Further, the content of the resin particles in the mixture comprising the composite type particles and the resin particles should preferably be confined within the range of 10 wt % to 90 wt %. It is possible, with the employment of the mixture containing the resin particles at this range of ratio, to achieve an especially high polishing rate. For example, in the case of a W (tungsten) film, it is possible to secure a high polishing rate of 100 nm/min. or more.
The concentration of total particles of the mixture comprising the composite type particles and the resin particles in the slurry should preferably be confined within the range of 0.1 wt % to 40 wt %. If this concentration of particles is less than 0.1 wt %, it may become difficult to obtain a sufficient polishing effect. On the other hand, if this concentration of particles exceeds 40 wt %, the particles may be flocculated. More preferably, the concentration of total particles of the mixture in the slurry should be confined within the range of 0.5 wt % to 30 wt %.
When required, various additives such as an oxidant, a pH regulator, etc. can be added to the slurry to prepare the slurry according to one embodiment of the present invention.
Since a mixture comprising the composite type particles and the resin particles is included as abrasive grains in the slurry according to this embodiment of the present invention, these particles are capable of forming the closest-packed structure on the surface of polishing pad during the polishing step. As a result, a suitable clogging generates, thereby making it possible to fix the particles onto the surface of the polishing pad and to minimize the generation of free particles. As a result, it is now possible to suppress the generation of dishing and to perform the polishing at a sufficiently high polishing rate. Moreover, since the surfaces of the composite type particles and the resin particles have the same polarity with each other, or since either one of the composite type particles and the resin particles have an isoelectric point, the viscosity of the slurry can be sufficiently reduced.
Even if the inorganic component of the composite type particles is subjected to polishing stress, the inorganic component is prevented from falling from the polymer particles constituting the resin component and keeps the strong bonding thereof to the polymer particles. The resin component on the other hand deforms or destructs as the resin component is subjected to polishing stress. As a result, during the polishing, the inorganic component which is capable of exhibiting polishing power bonds to the surface of the resin component that has been destroyed, thereby forming composite type particles having a reduced diameter. These miniaturized composite type particles are uniformly mixed with the resin particles.
Incidentally, the resin particles are hydrophobic and hence the surface of the polishing pad is also hydrophobic. Accordingly, the resin particles adsorb onto the surface of the polishing pad while entraining therein these miniaturized composite type particles. As a result, it is now possible to perform the polishing while minimizing the generation of free particles.
If the resin component and the inorganic component in the composite type particles according to one embodiment of the present invention are respectively employed as a separate component and are employed together with the resin particles, the aforementioned effects would not be achieved. In that case, the resin particles and the inorganic component are fixed in such a manner that these particles are buried in gaps between resin components. As a result, the inorganic component having polishing power is prevented from being exposed on the surface of polishing pad, resulting in retardation of polishing.
If the composite type particles are replaced by inorganic particles having the same particle diameter as that of the composite type particles, the particle diameter of the inorganic component having polishing power would become too large relative to that of the resin particles. When fine polishing is performed, the particle diameter of the inorganic component is required to be confined to 100 nm or less. In order to sufficiently suppress the generation of dishing, the particle diameter of the inorganic component should preferably be confined to 50 nm or less. If inorganic particles having almost the same particle diameter as that of the composite type particles are employed, it would become difficult to suppress the generation of dishing, thus making it impossible to achieve the objects.
By using the slurry according to the embodiments of the present invention, it is possible to solve all of the problems accompanied with the conventional fixed abrasive grain type pad such as working efficiency, cost, the quality of worked surface, and stability.
Incidentally, when the abrasive grains are effectively fixed to a polishing pad by suitably selecting the top ring for holding a semiconductor substrate, the effects of the slurry according to the embodiment of the present invention would be further enhanced.
FIGS. 2A and 2B are cross-sectional views respectively illustrating schematically the construction of one embodiment of the top ring that can be employed in the embodiment of the present invention.
The top ring 67 shown in FIG. 2A has a box 63 having an air supply pipe 64 attached thereto, a retainer ring 61, a chucking plate 65, and an air bag 66. The polishing surface of a semiconductor substrate 60 held by the top ring 67 constructed in this manner is made substantially flush with the end face of the retainer ring 61. The semiconductor substrate 60 may be sustained in such a manner that the polishing surface is positioned about 0.2 mm higher than the end face of the retainer ring 61.
Accordingly, the retainer ring 61 is pressed against the polishing pad 62 by almost the same magnitude of pressure as the semiconductor substrate 60 is. Depending on some circumstances, the retainer ring 61 is pressed against the polishing pad 62 by a higher pressure than the pressure the semiconductor substrate 60 is pressed. The slurry (not shown) that has been fed to the surface of the polishing pad 62 is at first introduced into the polishing pad 62 by the retainer ring 61 and the abrasive grains immobilize. Thereafter, the slurry is fed to the surface of the polishing surface of the semiconductor substrate 60, so that the polishing is carried out under the conditions where the generation of free particles is minimized.
Whereas when a top ring 68 as shown in FIG. 2B is employed, it is impossible to immobilize the abrasive gains on the surface of the polishing pad 62 prior to the polishing of the polishing surface. Namely, since the polishing surface of the semiconductor substrate 60 held through a backing film 69 by the top ring 68 is protruded higher than the end face of the retainer ring 61, the slurry (not shown) that has been fed onto the surface of the polishing pad 62 is directly fed to the polishing surface of the semiconductor substrate 60. As a result, the abrasive grains can be immobilized, by the semiconductor substrate 60, on the surface of the polishing pad 62, thereby enabling the immobilization of the abrasive grains to be effected concurrent with the polishing.
Since the slurry according to this embodiment of the present invention contains not only the composite type particles but also the resin particles, it is possible to minimize the generation of free particles even if the immobilization of the abrasive grains is effected concurrent with the polishing. However, in order to further enhance the effects to immobilize the particles, it is especially preferable to employ the slurry in combination with the top ring 67 having a structure shown in FIG. 2A.
(Embodiment 1)
First of all, 94 parts (hereinafter, “part(s)” means “part(s) by weight”) of methylmethacrylate, 1 part of methacrylic acid, 5 parts of hydroxymethylmethacrylate, 0.03 part of ammonium lauryl sulfate, 0.6 part of ammonium persulfate and 400 parts of ion-exchange water were placed in a 2 L flask. The resultant mixture was polymerized for 6 hours with stirring in a nitrogen gas atmosphere and at a temperature of 70° C. As a result, it was possible to obtain a stock solution of resin particles containing PMMA particles at a concentration of 20 wt %, the PMMA having an average particle diameter of 200 nm and carboxylic group on the surface thereof.
On the other hand, composite type particles were prepared by bonding silica particles employed as an inorganic component to the PMMA particles employed as a resin component. The PMMA particles employed herein was those that had been synthesized by the aforementioned procedures. The particle diameter of the silica particles was set to 15 nm, and the average particle diameter of the PMMA particles was varied to alter the average particle diameter (d₁) of the composite type particles as a whole. More specifically, five kinds of composite type particles varied in average particle diameter, i.e. 100 nm, 200 nm, 300 nm, 400 nm and 1000 nm, were prepared.
For the purpose of complexing, 100 parts of an aqueous dispersion containing 10% by weight of the PMMA particles was placed in a 2 L flask and then mixed with 1 part of methyltrimethoxy silane. The resultant mixture was stirred for 2 hours at a temperature of 40° C. Thereafter, nitric acid was added to the mixture and the pH of the resultant mixture was adjusted to 2 to obtain an aqueous dispersion of the resin component. On the other hand, colloidal silica (“Snow Tex 0” trademark; Nissan Kagaku Co., Ltd.) was dispersed in water at a concentration of 10% by weight to obtain a dispersion to which potassium hydroxide was added to adjust the pH thereof to 8, thereby obtaining an aqueous dispersion of the inorganic component. Subsequently, 50 parts of this aqueous dispersion of the inorganic component was gradually added to 100 parts of the aqueous dispersion of the resin component over 2 hours to obtain a mixture. This mixture was stirred for 2 hours to obtain an aqueous dispersion containing preliminary particles consisting of the PMMA particles employed as a resin component and silica particles adhered onto the PMMA particles. Then, to this aqueous dispersion was added 2 parts of vinyltriethoxy silane, and the resultant dispersion was stirred for one hour. Thereafter, to the resultant dispersion was added 1 part of TEOS and heated up to a temperature of 60° C. The resultant mixture was subsequently stirred for 3 hours and cooled to obtain a stock solution of composite type particles containing composite type particles at a concentration of 10% by weight.
The stock solution of composite type particles thus obtained was combined with the aforementioned stock solution of the resin particles to obtain five kinds of particle mixtures differing in ratio of particle diameters (composite type particles d₁/resin particles d₂=0.5, 1, 1.5, 2 and 5).
By using the particle mixtures comprising the composite type particles and the resin particles as polishing particles, the slurry according to this embodiment was prepared according to the following recipe.
First of all, the stock solution of aforementioned resin particles and the stock solution of the composite type particles were mixed together and diluted with water so as to obtain a solution containing abrasive grains. Further, ferric nitrate as an oxidant, and water as a solvent were mixed together to obtain a slurry. The slurry comprises abrasive grains at a concentration of 5% by weight, 5% by weight of ferric nitrate, and 90% by weight of water. Since the slurry contained ferric nitrate, the pH of the slurry became about 2.5, i.e. an acid region. Further, the mixing ratio of these two stock solutions was varied to vary the ratio between the resin particles and the composite type particles, thus preparing a plurality of slurries.
By using various slurries thus obtained, W-CMP was performed according to the following procedures and the polishing rate of W was investigated.
FIGS. 3A and 3B are cross-sectional views each illustrating the steps of W-CMP.
First of all, as shown in FIG. 3A, an insulating film 21 having a film thickness of 300 nm was deposited on a semiconductor substrate 20, and holes 22 (0.1 μm in diameter) were formed. Further, a W film 24 having a thickness of 200 nm was formed, via a TiN film 23 having a thickness of 10 nm, the entire surface of the semiconductor substrate 20.
The redundant portions of the TiN film 23 and the W film 24 were removed by CMP to expose the surface of the insulating film 21 as shown in FIG. 3B.
The polishing of the W film 24 was performed as follows by using IC1000 (trademark; RODEL NITTA Co., Ltd.) as a polishing pad and the aforementioned slurry. Namely, as shown in FIG. 4, while rotating a turntable 30 having a polishing pad 31 attached thereto at a speed of 100 rpm, a top ring 33 holding a semiconductor substrate 32 was allowed to contact with the turntable 30 at a polishing load of 300 gf/cm². The rotational speed of the top ring 33 was set to 102 rpm, and slurry 37 was fed onto the surface of the polishing pad 31 from a slurry supply nozzle 35 at a flow rate of 200 cc/min. Incidentally, FIG. 4 also shows a water supply nozzle 34 and a dresser 36.
The relationship between the polishing rate of the W film 24 and the ratio of the resin particles in the particle mixture of the slurry is shown in the graph of FIG. 5. In FIG. 5, curves “a”, “b”, “c”, “d” and “e” illustrate the results obtained using five slurries differing in ratio of particle diameters (i.e. d₁/d₂=0.5, 1, 1.5, 2 and 5, respectively) in the particle mixture.
As shown in the graph of FIG. 5, when the composite type particles and the resin particles were employed individually, the polishing rate of the W film was 10 nm/min. or less. Whereas, in the case of the slurries where the composite type particles and the resin particles were employed as a mixture, the polishing rate of the W film was inclined to increase irrespective of the ratio of particle diameters. The reason for this can be ascribed to the fact that the composite type particles and the resin particles were enabled to form the closest-packed structure on the surface of polishing pad, thereby causing a suitable clogging and making it possible to immobilize these particles on the surface of polishing pad.
In particular, as shown by the curves “d” and “e”, in the region where the ratio of particle diameters was 2 or more and the ratio of the resin particles was within the range of 10 to 90% by weight, it was possible to perform the polishing of the W film at a polishing rate of as high as 100 nm/min. or more.

Next, various slurries were prepared in the same manner as described above except that the ratio of the resin particles was set to 10% by weight and at the same time, the materials for the composite type particles and the resin particles were altered. Then, the W film was subjected to polishing using these different slurries under the same conditions as described above to investigate the polishing speed of the W film. The results obtained are summarized in the following Table 1 together with the viscosity of each of slurries, the composition of the particle mixture and the polarity of the ζ-potential of each of the particles. Since the pH of these slurries was 2.5, the polarity of the ζ-potential of each of the particles shown herein was the result measured under the environments where pH was 2.5.

TABLE 1


Composite type particles	Resin particles	Polishing

Inorganic	ζ-	Resin	Resin	Functional	ζ-	rate of W	Viscosity
components	potential	components	materials	groups	potential	(nm/min)	(mPaS)

1	Silica	−	PST	PMMA	COOH	−	150	1
2	Silica	−	PST	PST	COOH	−	180	1
3	Silica	−	PST
			(cross-	PST	COOH	−	175	1
			linked)
4	Silica	−	PST	PST	COOH	−	170	1
5	Silica	−	PST
			(cross-	PST	COOH	−	155	1
			linked)
6	Alumina	+	PST	PST	COOH	−	CMP	12
							impossible
7	Alumina	+	PST	PST	NH₂	+	120	1
8	Silica	−	PST	PST	SO₃H	Zero	140	1
9	Silica	−	PMMA	PMMA	*	Zero	110	1
10	Silica	−	PMMA	PMMA	COOH	−	170	1

*Added with potassium dodecylbenzene sulfonate: 0.05 wt %

As shown in Table 1, in the samples where the ζ-potentials of the composite type particles and of the resin particles were both minus (Nos. 1-5 and No. 10) or both plus (No. 7), the viscosity of the slurries was all 1 mPaS. Likewise, in the case of the slurries where the ζ-potential of the resin particles was zero (Nos. 8 and 9), the viscosity thereof was as low as 1 mPaS. When these slurries were employed, it was possible to perform the polishing of the W film at a high polishing rate of 110 nm/min or more. Further, in either cases, the dishing of the surface after the polishing was confined to 10 nm or less.
Even in the cases where the kind of the functional groups of the surface of resin particles was altered or where a surfactant was incorporated into the slurry, it was possible to obtain an equally high polishing rate. The resin component of the composite type particles is not necessarily required to be the same as the material of the resin particles. That is, even if the resin component of the composite type particles is different from the material of the resin particles, it is possible to obtain the same effects as described above. Further, even if the composite type particles and the resin particles are respectively constituted by two or more kinds, it is possible to expect a high polishing rate.
The pH of the slurries of sample Nos. 1-10 was about 2.5, so that even if the pH thereof was as low as 2.5, the slurries according to the embodiments of the present invention are capable of achieving a sufficiently high polishing rate. On the contrary, even if the pH of the slurries was as high as 10 or more, it is possible to expect almost the same effects as those of the slurries according to the embodiments of the present invention.
In the cases of the conventional slurries where the resin particles or the composite type particles are individually included therein, only the particles having a narrow range of pH ranging from about 3 to 7 are considered useful as abrasive grains. The reason for this can be ascribed to the fact that a surfactant or an organic compound has been incorporated in the slurry for the purpose of enhancing the interaction between the abrasive grains and the polishing pad. Therefore, in the regions of strong acid or strong alkali, the aforementioned additives are caused to deactivate, thereby making it impossible to obtain the desired effects.
In the embodiments of the present invention, since the composite type particles and the resin particles are mixed together for use as abrasive grains, it is possible to achieve a sufficient interaction between the abrasive grains and the polishing pad. Accordingly, the slurries according to the present invention are capable of using them even under a wide pH range which the conventional slurries have been considered impossible.
As shown in Table 1, in the case of slurry (No. 6) where a particle mixture comprising the composite type particles whose ζ-potential was plus and the resin particles whose ζ-potential was minus was employed, the viscosity of the slurry was as very high as 12 mPaS. The slurry having such a high viscosity was not capable of dropping onto the polishing pad 31 from the slurry supply nozzle 37, and hence, it was impossible to execute the CMP.
(Embodiment 2)
On the occasion of performing the second polishing of Cu in the process of forming Cu damascene wirings, a film of different materials, such as TaN or SiO₂, is required to be made flat through polishing. In such a case, according to the prior art, nonselective polishing has been performed with the ratio of polishing rates thereof being set to about 1. However, in the case of an organic insulating film, due to physical effects such as hardness and the hydrophobicity of surface, strong erosion would be generated if the organic insulating film is polished under the aforementioned conditions.
When the slurries according to the embodiments of the present invention are employed, even if selective polishing is performed with the ratio of polishing rates thereof being set to 1 or more, it is possible to form Cu damascene wirings with low erosion. Moreover, it is possible to substantially prevent the generation of scratches on the surface of an organic insulating film or a Cu film after polishing.
FIGS. 6A to 6C are cross-sectional views illustrating Cu-CMP.
First of all, as shown in FIG. 6A, an insulating film 41 was deposited on a semiconductor substrate 40 having semiconductor element (not shown) formed thereon. Thereafter, a contact 42 was formed therein. On this insulating film 41, there were deposited, by CVD method, a film of LKD5109 (available from JSR) having 200 nm as a low dielectric constant film 43, and a film of Black Diamond (available from AMAT, hereinafter referred to BD) having 100 nm as a cap film 44.
Subsequent to the formation of a trench 45 in the low dielectric constant film 43 and the cap film 44 by RIE, a TaN film 46 (20 nm) and a Cu film 47 (500 nm) were deposited over the entire surface of a substrate by sputtering and plating.
Then, a redundant portion of the Cu film 47 was removed by CMP under the following conditions to expose the TaN film 46 as shown in FIG. 6B.

- Slurry: CMS7303/7304 (JSR Co., Ltd.)
- Flow rate of slurry: 250 cc/min.
- Polishing pad: IC1000 (trademark; RODEL NITTA Co., Ltd.);
- Load: 300 gf/cm².

Rotational speed of carrier and turntable were both set to 100 rpm, and the polishing was performed for one minute. In this step, since the polishing was prevented from proceeding due to the presence of the TaN film 46, the hydrophobic cap film 44 was prevented from being exposed. Accordingly, it was possible to perform the polishing by using a slurry available on the market.
Thereafter, by a touch-up process, an redundant portion of the TaN film 46 was removed as shown in FIG. 6C. In this CMP, the slurry according to this embodiment of the present invention was employed.
In the preparation of the slurry, a particle mixture comprising the composite type particles having an average particle diameter (d₁) of 200 nm, and the resin particles having an average particle diameter (d₂) of 100 nm was prepared as abrasive grains. The ratio of particle diameters (d₁/d₂) between the composite type particles and the resin particles was 2. The composite type particles comprised PMMA particles having an average particle diameter of 150 nm as the resin component, and silica particles having an average particle diameter of 25 nm as the inorganic component. Namely, the resin particles were made of PMMA and accompanied on the surface thereof with COOH group as a functional group. The composite type particles and the resin particles were prepared respectively as a stock solution of the same concentration by the same procedures as described above.
A stock solution of the composite type particles and a stock solution of the resin particles mentioned above were mixed together and diluted with pure water so as to include the composite type particles at a concentration of 2.7 wt % and the resin particles at a concentration of 0.3 wt %. Further, to this resultant solution were added 0.1 wt % of an aqueous solution of hydrogen peroxide as an oxidant, 0.8 wt % of quinolinic acid as an oxidation inhibitor, and additives. Then, the pH of the resultant mixture was adjusted to 10 by using a pH regulator, i.e. KOH.
On the other hand, a slurry of comparative example was prepared by following the same procedures as described above except that two kinds of colloidal silica differing in average particle diameter were substituted for the aforementioned abrasive grains. More specifically, a mixture composed of 0.6 wt % of colloidal silica having an average particle diameter of 40 nm and 2.4 wt % of colloidal silica having an average particle diameter of 20 nm was employed as the abrasive grains.
The polishing of the substrate was performed for 2 minutes using each of the slurries under the same conditions as described above to investigate the polishing rate of each of the Cu film 47, the TaN film 46 and the cap film 44. The polishing time was adjusted to a period of time which required to abrade the BD (employed as the cap film 44) to a depth of 50 nm. As a result, it was found that when the slurries according to the embodiment of the present invention were employed, the polishing rates of the Cu film, the TaN film and the cap film were 100 nm/min., 45 nm/min. and 20 nm/min., respectively. Whereas, when the slurry of the comparative example was employed, the polishing rate of the Cu film was 70 nm/min., and the polishing rates of the TaN film and the cap film were both 60 nm/min.
As described above, when the slurry of the comparative example was employed, the polish-ing rate of the cap film 44 was as high as 60 nm/min., so that erosion was caused to generate, thereby came off the cap film 44 partially. The step portion between the Cu film 47 and the cap film 44 was configured such that the Cu film 47 was protruded higher than the cap film 44 with the erosion being 120 nm in depth. Since the cap film 44 was provided for the purpose of protecting the insulating film 43 from being damaged in the succeeding step, the destruction of the cap film 44 should be avoided as much as possible. Whereas, when the slurries according to the embodiments of the present invention were employed, the erosion of the cap film 44 was restricted to as small as 20 nm and the cap film 44 was prevented from being destroyed. Since the slurries according to the embodiments of the present invention contained resin particles made of an organic material, it was possible to generate a suitable interaction thereof with an organic film.
Further, the generation of dishing on the surface of the Cu film 47 after the polishing was suppressed to 20 nm or less. With respect to the generation of scratches per 1 cm²on the surfaces of the Cu film 47 and the cap film 44 after the polishing, while the number of scratches was about 10000 when the slurry of the comparative example was employed, the number of scratches was reduced to 100 or less when the slurries according to the embodiments of the present invention were employed. It is possible, through the optimization of the additive components, to further reduce the number of scratches.
(Embodiment 3)
The slurries according to the embodiments of the present invention were capable of applying them to the formation of STI (Shallow trench isolation). FIGS. 7A and 7B are cross-sectional views each illustrating the process of forming the STI.
First of all, as shown in FIG. 7A, a trench was formed on the surface of a semiconductor substrate 50 having a CMP stopper film 51, and then, an insulating film 52 was deposited thereon. In this case, SiN was employed as the CMP stopper film 51. As for the insulating film 52, it is possible to employ a coating-type insulating film such as an organic SOG.
Then, a redundant portion of the insulating film 52 was removed by CMP using the slurry according to one embodiment of the present invention to expose the surface of the CMP stopper film 51 as shown in FIG. 7B. The slurry was prepared by using, as abrasive grains, a particle mixture comprising the composite type particles having an average particle diameter (d₁) of 200 nm, and the resin particles having an average particle diameter (d₂) of 100 nm. The ratio of particle diameters (d₁/d₂) between the composite type particles and the resin particles was 2. The composite type particles comprised PST particles having an average particle diameter of 200 nm as the resin component, and silica particles having an average particle diameter of 40 nm as the inorganic component. The composite type particles were synthesized as follows. Namely, 92 parts of styrene, 4 parts of methacrylic acid, 4 parts of hydroxyethylacrylate, 0.1 part of ammonium lauryl sulfate, 0.5 part of ammonium persulfate and 400 parts of ion-exchange water were placed in a 2 L flask. Then, the resultant mixture was polymerized for 6 hours with stirring in a nitrogen gas atmosphere and at a temperature of 70° C. As a result, it was possible to obtain a stock solution of resin particles containing PST particles at a concentration of 20 wt %, the PST particles having carboxylic group attached to the surface thereof. In the synthesis of the PST particles, one part of divinyl benzene (purity: 55%) was used as a cross-linking agent. If it is desired to provide the resin particles with a functional group other than COOH, it is possible to employ pyridine ring compounds (amino group), sulfonates (sulfonic group), etc.
For the purpose of complexing, 100 parts of an aqueous dispersion containing 10% by weight of the PST particles was placed in a 2 L flask and then mixed with 1 part of methyltrimethoxy silane. The resultant mixture was stirred for 2 hours at a temperature of 40° C. Thereafter, nitric acid was added to the mixture and the pH of the resultant mixture was adjusted to 2 to obtain an aqueous dispersion of the resin component. On the other hand, colloidal silica (“Snow Tex 0” trademark; Nissan Kagaku Co., Ltd.) was dispersed in water at a concentration of 10% by weight to obtain a dispersion to which potassium hydroxide was added to adjust the pH thereof to 8, thereby obtaining an aqueous dispersion of the inorganic component. Subsequently, 50 parts of this aqueous dispersion of the inorganic component was gradually added to 100 parts of the aqueous dispersion of the resin component over 2 hours to obtain a mixture. This mixture was stirred for 2 hours to obtain an aqueous dispersion containing preliminary particles comprising the polymer particles and silica particles adhered onto the polymer particles. Then, to this aqueous dispersion was added 2 parts of vinyltriethoxy silane, and the resultant dispersion was stirred for one hour. Thereafter, to the resultant dispersion was added 1 part of TEOS and heated up to a temperature of 60° C. The resultant mixture was subsequently stirred for 3 hours and cooled to obtain a stock solution of composite type particles containing composite type particles at a concentration of 10% by weight.
A concentrated solution of the stock solution of the composite type particles and a stock solution of the resin particles mentioned above were mixed together and diluted with pure water so as to include the composite type particles at a concentration of 18 wt % and the resin particles at a concentration of 2 wt %. Incidentally, in this case, the aforementioned concentrated solution employed herein was prepared by removing a supernatant liquid of the stock solution of the composite type particles by particle sedimentation method to obtain a concentrated solution containing the composite type particles at a concentration of 20 wt %. The stock solution of the resin particles employed herein contained cross-linked PST particles at a concentration of 20 wt %. Then, the pH of the resultant mixture was adjusted to 11 by using a pH regulator, i.e. KOH.
Then, by using the slurry thus obtained, an insulating film 52 was polished under the following conditions.

- Flow rate of slurry: 300 cc/min;
- Polishing pad: IC1000 (trademark; RODEL NITTA Co., Ltd.);
- Load: 300 gf/cm².

Rotational speed of the top ring and turntable were both set to 100 rpm, and the polishing was performed for 3 minutes.
C and SiN to be employed as a material for the CMP stopper film 51 are in most cases hydrophobic and the ζ-potential thereof is respectively of an isoelectric point. As a result, they present an environment where scratches are liable to generate.
By using the slurry according to this embodiment, the generation of scratches on the surface of wafer after polishing was suppressed to two and the erosion was suppressed to 30 nm or less. Thus, it was possible to confirm that the effects of the present invention could be achieved even on the occasion of performing the CMP of an insulating film formed on the surface of the CMP stopper film which was vulnerable to scratches.
As explained above, according to this embodiment, it is possible to provide a slurry which is capable of minimizing the dishing as well as the erosion and also capable of polishing the polishing surface at a practically acceptable polishing rate. According to another embodiment of the present invention, it is possible to provide a polishing method which is capable of minimizing the dishing as well as the erosion and also capable of polishing the polishing surface at a practically acceptable polishing rate. According to a further embodiment of the present invention, it is possible to provide a method of manufacturing a semiconductor device which is excellent in reliability.
According to the embodiment of the present invention, it is now possible to manufacture a semiconductor device of high-performance and high-processing speed and having fine wirings of 0.1 μm of less in design rule which is to be demanded in the wirings of the next generation. Therefore, the present invention would be very valuable from an industrial viewpoint.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims

1. A CMP slurry comprising:

composite type particles comprising a resin component and an inorganic component, which are complexed with each other; and

resin particles,

the CMP slurry having a viscosity of less than 10 mPas.

2. The CMP slurry according to claim 1, wherein the composite type particles and the resin particles are of the same polarity.

3. The CMP slurry according to claim 1, wherein either one of the composite type particles and the resin particles is maintained at an isoelectric point.

4. The CMP slurry according to claim 1, wherein a ratio in particle diameter (d₁/d₂) between an average particle diameter d₁of the composite type particles and an average particle diameter d₂of the resin particles is 2 or more.

5. The CMP slurry according to claim 1, wherein a content of the resin particles is within the range of 10 wt % to 90 wt % based on a total weight of the composite type particles and the resin particles.

6. The CMP slurry according to claim 1, wherein the resin component is selected from the group consisting of polymethyl methacrylate and polystyrene.

7. The CMP slurry according to claim 1, wherein the resin particles are provided on the surface thereof with a hydrophilic group.

8. A polishing method comprising:

contacting a polishing surface of the semiconductor substrate with a polishing pad attached to a turntable; and

dropping a CMP slurry onto the polishing pad to polish the polishing surface of the semiconductor substrate, the CMP slurry having a viscosity of less than 10 mPas and comprising composite type particles composed of a resin component and an inorganic component, which are complexed with each other, and resin particles.

9. The polishing method according to claim 8, wherein the composite type particles and the resin particles in the CMP slurry are of the same polarity.

10. The polishing method according to claim 8, wherein either one of the composite type particles and the resin particles in the CMP slurry is maintained at an isoelectric point.

11. The polishing method according to claim 8, wherein a ratio in particle diameter (dl/d₂) between an average particle diameter d₁of the composite type particles and an average particle diameter d₂of the resin particles in the CMP slurry is 2 or more.

12. The polishing method according to claim 8, wherein a content of the resin particles is within the range of 10 wt % to 90 wt % based on a total weight of the composite type particles and the resin particles in the CMP slurry.

13. The polishing method according to claim 8, wherein the semiconductor substrate is retained in a retainer ring, and the polishing surface is positioned over an end face of the retainer ring.

14. The polishing method according to claim 8, wherein the composite type particles and the resin particles are fixed to the polishing pad prior to the polishing of the polishing surface.

15. A method of manufacturing a semiconductor device comprising:

forming an insulating film above a semiconductor substrate;

forming a recessed portion in the insulating film;

depositing a conductive material inside the recessed portion and on the insulating film to form a conductive layer; and

removing the conductive material deposited on the insulating film by CMP using a CMP slurry to expose the surface of the insulating film while selectively leaving the conductive material in the recessed portion, the CMP slurry having a viscosity of less than 10 mPas and comprising composite type particles composed of a resin component and an inorganic component, which are complexed with each other, and resin particles.

16. The method according to claim 15, wherein the composite type particles and the resin particles in the CMP slurry are of the same polarity.

17. The method according to claim 15, wherein either one of the composite type particles and the resin particles in the CMP slurry is maintained at an isoelectric point.

18. The method according to claim 15, wherein a ratio in particle diameter (d₁/d₂) between an average particle diameter d₁of the composite type particles and an average particle diameter d₂of the resin particles in the CMP slurry is 2 or more.

19. The method according to claim 15, wherein a content of the resin particles is within the range of 10 wt % to 90 wt % based on a total weight of the composite type particles and the resin particles in the CMP slurry.

20. The method according to claim 15, wherein the conductive material includes a Cu film deposited through a TaN film.