US20100221895A1

US20100221895A1 - Surface treatment apparatus and surface treatment method

Info

Publication number: US20100221895A1
Application number: US12/764,242
Authority: US
Inventors: Takuya Seino; Manabu Ikemoto; Kimiko Mashimo
Original assignee: Canon Anelva Corp
Current assignee: Canon Anelva Corp
Priority date: 2007-11-02
Filing date: 2010-04-21
Publication date: 2010-09-02
Also published as: US10083830B2; KR20100033328A; US20160343565A1; JP5006938B2; CN101919030A; WO2009057223A1; CN101971298A; US20100255667A1; JPWO2009057223A1; WO2009057395A1; KR101503412B1; CN101919030B

Abstract

HF-originated radicals generated in a plasma-forming chamber are fed to a treatment chamber via feed holes, while HF gas molecules as the treatment gas are supplied to the treatment chamber from near the radical feed holes to suppress the excitation energy, thereby increasing the selectivity to Si to remove a native oxide film. Even with the dry-treatment, the surface treatment provides good surface flatness equivalent to that obtained by the wet-cleaning which requires high-temperature treatment, and further attains growth of Si single crystal film on the substrate after the surface treatment. The surface of formed Si single crystal film has small quantity of impurities of oxygen, carbon, and the like. After sputtering Hf and the like onto the surface of the grown Si single crystal film, oxidation and nitrification are applied thereto to form a dielectric insulation film such as HfO thereon, thus forming a metal electrode film. All through the above steps, the substrate is not exposed to atmospheric air, thereby suppressing the adsorption of impurities onto the interface, and thus obtaining a C-V curve with small hysteresis. As a result, good device characteristics are obtained in MOS-FET.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of International Application No. PCT/JP2007/071393, filed on Nov. 2, 2007, the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an apparatus and a method of manufacturing a semiconductor device, including the treatment of surface of group IV semiconductor.
2. Related Background Art
Conventionally semiconductor Si substrate is subjected to wet-cleaning. The wet-cleaning has, however, problems of failing to completely remove water-marks in dry state, failing to control etching of very thin oxide film, requiring large apparatus, and the like. Furthermore, when the semiconductor substrate is exposed to atmospheric air for a long time after the wet-cleaning, there arise problems of forming native oxide film on the surface thereof and adsorbing carbon atoms thereon to inhibit film-forming of Si single crystal, generating irregular profile of film, generating impurity level at the interface of gate insulation film, and the like.
Therefore, surface oxide film was removed by applying UHV vacuum heating to 750° C. or higher or by applying heating to 800° C. or higher in an H₂atmosphere before film formation. However, as miniaturization of device progresses and dielectric insulation film/metal electrode is used, the device needs to be manufactured at lower temperatures. Thus the device manufacturing needs to be done at 650° C. or lower temperature. As a result, the wet-cleaning has its limits, and there arises a need of dry-cleaning method which conducts treatment of semiconductor substrate in a vacuum before film-forming. The reverse sputtering method using argon plasma is one example of the method (Japanese Patent Laid-Open No. 10-147877). The disclosed method, however, presumably cuts also the Si—Si bond on the surface of the semiconductor substrate. In that case, problems arise such that oxide film is immediately formed on the Si-absent portion, that contaminants likely adhere to the dangling bond of Si, and that the sputtered oxide and contaminants adhere again to the side wall of the substrate. These problems adversely affect the succeeding step, (such as inhibition of epitaxial growth and formation of highly resistant portion on the silicide interface). Furthermore, damages on the device are also the problem.
Japanese Patent Laid-Open No. 2004-63521 describes that, after removing the silicon oxide film from the surface of the substrate using a plasmatized F₂gas, the hydrogen radicals are irradiated to remove the F component adhered to the surface of the substrate. Japanese Patent Laid-Open No. 04-96226 describes that, after removing the Si native oxide film from the surface of the substrate using F₂gas, the radicalized hydrogen is irradiated to the substrate to terminate the bonding operation by the hydrogen. Since, however, the plasmatized F₂gas contains not only the radicalized fluorine gas but also ionized fluorine gas, there arises a problem of irregular surface on removing the silicon oxide film from the surface of the substrate. In addition, there may occur also the removal of a portion of substrate not only the removal of silicon oxide film on the surface thereof.
Japanese Patent Laid-Open No. 2001-102311 describes that a cleaning gas such as fluorine is supplied to a plasma-forming part having a plasma-forming chamber which is separated by a plate having feed holes for a film-forming chamber where the substrate is placed, thus generating radicals by generating plasma in the plasma-forming part, and the fluorine radicals are fed to a film-forming space containing the substrate via the feed holes, thereby irradiating the radicals to the substrate to clean the substrate. Since, however, the surface of the semiconductor substrate cannot be exposed to the atmosphere where the excitation energy of radicals is suppressed, highly selective Si etching cannot be performed, which raises a problem of failing to remove the native oxide film without deteriorating the surface roughness.
Furthermore, since the semiconductor substrate is exposed to plasma, Si—Si bond is also cut off. In this state, there arise problems such that oxide film is immediately formed on the Si-absent portion, that contaminants likely adhere to the dangling bond of Si, and that the sputtered oxide and contaminants adhere again to the side wall of the substrate. These problems adversely affect the succeeding stage, (such as inhibition of epitaxial growth and formation of highly resistant portion on the silicide interface). Furthermore, damages on a device are also the problem. According to the disclosure, gas is decomposed positively by plasma to generate hydrogen radicals and hydrogen ions. When fluorine residue on the surface of the substrate is removed by the hydrogen radicals and the hydrogen ions, there arise problems of contamination by metal coming from the chamber, of excess etching because of large etching rate on the base Si, and the like. Furthermore, since HF as the reaction product likely adheres again to the surface of the substrate, sufficient F-removal effect is not attained. Japanese Patent Laid-Open No. 2002-217169 discloses an apparatus for conducting entire cleaning step in a vacuum to remove foreign matter applying simultaneously a physical action of friction stress generated by a high velocity gas flow. According to the disclosure, adsorption of impurities and generation of native oxide during vacuum transfer are suppressed, thus improving the production efficiency. Even if the foreign matter can be removed, however, the native oxide film and the surface roughness remain on the surface at an order of atomic layer thickness. That is, to attain the effect of device characteristic improvement by the continuous transfer in vacuum, there are required the cleaning technology to control the highly selective etching of Si and native oxide film at an order of atomic layer thickness, and the transfer of substrate and the film-forming thereon without exposing the substrate to atmospheric air. That kind of control technology and vacuum operation should provide good device characteristics of low interface state at the joint between semiconductor and dielectric insulation film, and of small fixed charge in the film.

SUMMARY OF INVENTION

Problems to be Solved by the Invention

According to the surface treatment in the related art to remove native oxide film and organic matter from the substrate surface, the transfer in atmospheric air is required before the substrate arrives at the next film-forming step. During the transfer of the substrate in atmospheric air, substances in air adsorb onto the surface of the substrate, and native oxide film and impurities such as carbon atoms are left behind on the interface, which raises a problem of deterioration of device characteristics. When the substrate treatment is conducted in a vacuum not to leave the native oxide film and the impurities such as carbon atoms on the interface, the flatness of the substrate surface is deteriorated, though the native oxide film and the impurities such as organic matter and carbon on the substrate surface can be removed. Furthermore, poor flatness of the substrate surface raises a problem of deteriorating the characteristics of manufactured device.

Means to Solve the Problems

The present invention is made to solve the above problems. According to the investigations of the inventors of the present invention, radicals generated by plasma are fed to the treatment chamber via a plurality of holes formed on a partition plate which separates the plasma-forming chamber from the treatment chamber, the radicals are mixed with a treatment gas which is separately fed to the treatment chamber, thus suppressing the excitation energy of the radicals to thereby enable the substrate surface treatment at high Si-selectivity, and thus it is found out that the surface treatment becomes available which removes native oxide film and organic matter without deteriorating the flatness of the substrate surface.
The present invention provides a method of cleaning a substrate comprising the steps of: placing a substrate in a treatment chamber; turning a plasma-forming gas; feeding a radical in the plasma to the treatment chamber via a radical-passing hole of a plasma-confinement electrode plate for plasma separation; feeding a treatment gas to the treatment chamber to mix it with the radical in the treatment chamber; and cleaning the surface of the substrate by the mixed atmosphere of the radical and the treatment gas.
The present invention provides a method of cleaning a substrate, wherein the surface of the substrate is a group IV semiconductor material, and the plasma-forming gas and the treatment gas contain HF, respectively.
The present invention provides a method of cleaning a substrate, wherein the plasma-confinement electrode plate for plasma separation has a plurality of radical feed holes for feeding the radical in the plasma to the treatment chamber and a plurality of treatment gas feed holes for feeding the treatment gas into the treatment chamber, and thus the radical and the treatment gas are discharged toward the surface of the substrate in the treatment chamber via the respective feed holes.
The present invention provides a method of manufacturing a semiconductor device comprising the steps of: cleaning the surface of a group IV semiconductor substrate in a cleaning chamber in accordance with the above method; transferring the cleaned substrate from the cleaning chamber to an epitaxial chamber via a transfer chamber without exposing the substrate to atmospheric air; and epitaxially growing an epitaxial single crystal layer on the surface of the substrate in the epitaxial chamber.
The present invention provides a method of manufacturing a semiconductor device comprising the steps of: transferring a substrate having an epitaxial layer manufactured in accordance with the above method from the epitaxial chamber to a sputtering chamber via a transfer chamber without exposing the substrate to atmospheric air; sputtering a dielectric film onto the epitaxial layer in the sputtering chamber; transferring the substrate having the dielectric film thereon from the sputtering chamber to an oxidation-nitrification chamber via a transfer chamber without exposing the substrate to atmospheric air; and conducting oxidation, nitrification, or oxynitrification of the dielectric film in the oxidation-nitrification chamber.
The present invention provides a method of manufacturing a semiconductor device according to above method, wherein the dielectric film is made of the one selected from the group consisting of Hf, La, Ta, Al, W, Ti, Si, and Ge, or an alloy thereof.
The present invention provides a method of cleaning a substrate according to above method, wherein turning the plasma-forming gas into plasma is done by applying a high frequency power thereto, and the density of the high frequency power is in a range from 0.001 to 0.25 W/cm², preferably from 0.001 to 0.125 W/cm², and more preferably from 0.001 to 0.025 W/cm².
The present invention provides a substrate treatment apparatus of plasma-separation type generating a radical by forming plasma from a plasma-forming gas in a vacuum chamber, and conducting substrate treatment by the radical and a treatment gas, the substrate treatment apparatus comprising: a plasma-forming chamber for turning the plasma-forming gas fed therein into plasma; a treatment chamber containing a substrate holder on which a substrate to be treated is placed; and a plasma-confinement electrode plate for plasma separation having a plurality of radical-passing holes formed between the plasma-forming chamber and the treatment chamber, the plasma-confinement electrode plate of a hollow structure having a plurality of treatment gas feed holes opened toward the treatment chamber formed, and having a gas-feed pipe for supplying the treatment gas disposed, wherein: a plasma-forming space inside the plasma-forming chamber contains a high-frequency applying electrode for generating plasma by a power supplied from a high-frequency power source; the high-frequency applying electrode has a plurality of through-holes penetrating therethrough; the high-frequency applying electrode further contains a plasma-forming gas feed shower plate for feeding the plasma-forming gas to the plasma-forming chamber; and the plasma-forming gas feed shower plate has a plurality of gas-discharge ports for feeding the plasma-forming gas onto the electrode extending along the plasma-confinement electrode plate for plasma separation provided with the plurality of radical-passing holes.
The present invention provides a substrate treatment apparatus according to above apparatus, wherein, in the substrate treatment chamber, the volume ratio V2/V1 is in a range from 0.01 to 0.8, where V2 is the total volume of the plurality of through-holes of the electrode, and V1 is the total volume of the electrode including the through-holes.
The present invention provides a substrate treatment apparatus according to above apparatus, wherein the density of the high frequency power applied to the high frequency-applying electrode is in a range from 0.001 to 0.25 W/cm², preferably from 0.001 to 0.125 W/cm², and more preferably from 0.001 to 0.025 W/cm².
The present invention provides a substrate treatment apparatus according to above substrate, wherein the plasma-forming gas fed to the plasma-forming chamber is a gas containing HF, and the gas fed to the treatment chamber is a gas containing HF.
The present invention provides an apparatus of manufacturing semiconductor device comprising: a substrate cleaning chamber including the above substrate treatment apparatus; an epitaxial growth chamber forming an epitaxial layer on the substrate; and a transfer chamber transferring the substrate coming from the substrate cleaning chamber to the epitaxial growth chamber without exposing the substrate to atmospheric air.
The present invention provides an apparatus of manufacturing a semiconductor device according to above apparatus, further comprising a sputtering chamber forming a dielectric film, thus allowing transferring the substrate coming from the cleaning chamber or the epitaxial growth chamber to the sputtering chamber via the transfer chamber without exposing the substrate to atmospheric air.
The present invention provides an apparatus of manufacturing a semiconductor device according to above apparatus, further comprising an oxidation-nitrification chamber for oxidation, nitrification, or oxynitrification of the dielectric film, thus allowing transferring the substrate coming from the cleaning chamber, the epitaxial growth chamber, or the sputtering chamber to the oxidation-nitrification chamber via the transfer chamber without exposing the substrate to atmospheric air.

EFFECT OF THE INVENTION

The present invention performs substrate treatment which can decrease the native oxide film and organic impurities on the surface of semiconductor substrate compared with the wet-cleaning in the related art, and can remove the native oxide film and organic matter without deteriorating the flatness of the substrate surface.
According to the present invention, to remove the native oxide film and contamination of organic impurities from the surface of semiconductor substrate, HF gas or a mixed gas containing at least HF is used as the plasma-forming gas and the treatment gas, and radicals are fed from the plasma-forming chamber to the treatment chamber, while feeding simultaneously gas molecules containing HF as the structural element thereto, thus exposing the surface of semiconductor substrate to the above atmosphere which suppresses the excitation energy of the radicals, to thereby remove the native oxide film and organic matter without deteriorating the flatness of the substrate surface. There generates no metal contamination and plasma damage on the semiconductor substrate. Although the wet-cleaning in the related art needs more than one step for the substrate treatment applying also succeeding steps such as annealing treatment, the present invention performs the substrate treatment in only one step, which attains desired effect efficiently, reduces cost, and significantly improves the treatment speed. Furthermore, use of a shower plate to the plasma-forming gas allows uniform feeding of the product gas, use of through-holes on the electrode part allows discharge even at a low power, and use of a plasma-confinement electrode plate for plasma separation provided with a plurality of radical-passing holes allows radicals in the produced plasma to be fed uniformly to the treatment chamber. Actualizing the surface treatment to give fine surface roughness at an order of atomic layer thickness allows forming single crystal Si and SiGe films on the surface.
By the first step of conducting substrate surface treatment, and the second step of transferring the substrate without exposing the single crystal film to atmospheric air, the amount of impurities at the interface is smaller than that appears in the atmospheric transfer, and thus good device characteristics are attained.
By conducting the first step of conducting substrate surface treatment, the second step of forming single crystal film, the third step of sputtering the dielectric material to form a film, the fourth step of conducting oxidation, nitrification, or oxynitrification, and the fifth step of transferring the metallic material and the sputtered film in a vacuum without exposing thereof to atmospheric air, the amount of impurities on the joint interface between the semiconductor and the insulation film becomes smaller than that in atmospheric transfer, which provides the interface state density and the fixed charge density in film equivalent to those of oxide film attained in the related art, gives a C-V curve with small hysteresis, gives a small leak current, and thereby attains good device characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a configuration example of a film-forming apparatus used in the present invention.

FIG. 2 is a schematic diagram of a controller installed in the apparatus used in the present invention.

FIG. 3 is a schematic diagram of a configuration example of a surface treatment apparatus used in the present invention.

FIG. 4 is a schematic diagram of a configuration example of a high-frequency applying electrode part of the surface treatment apparatus used in the present invention.

FIG. 5 is a schematic diagram of a configuration example of a plasma-confinement electrode plate part of the surface treatment apparatus used in the present invention.

FIG. 6 is a graph showing a native oxide film/Si with varied high-frequency power density, obtained in an example of the present invention.

FIG. 7 is a schematic diagram of a configuration example of a UV, X-ray and microwave excited radical surface treatment apparatus used in the present invention.

FIG. 8 is a schematic diagram of a configuration example of a catalytic-chemical excited radical surface treatment apparatus used in the present invention.

FIG. 9 is a schematic diagram of a surface treatment method used in the present invention.

FIG. 10 is a flowchart of a transfer controller program used in the present invention.

FIG. 11 is a flowchart of a film-forming controller program used in the present invention.

FIG. 12 gives a graph showing the surface roughness (Ra) after treatment of the substrate, and SEM images on the surface, obtained by an example of the present invention.

FIG. 13 is a graph showing the surface roughness (Ra) relative to the fraction of treatment chamber gas with varied fraction of the plasma-forming gas, obtained by an example of the present invention.

FIG. 14 gives SEM images on the surface after the growth of Si and SiGe, obtained by an example of the present invention.

FIG. 15 is a graph showing the atom density of oxygen and carbon at an interface, obtained by an example of the present invention.

FIG. 16 is a C-V curve obtained by an example of the present invention.

FIG. 17 shows a comparison of the interface state density and the fixed charge density, between those obtained by an example of the present invention and those of oxide film in the related art.

FIG. 18 is a graph showing the relation between the equivalent oxide film thickness (EOT) and the leak current, obtained by an example of the present invention.

FIG. 19 is a diagram illustrating a MOS-FET manufactured by the treatment of the present invention.

FIG. 20 is a diagram of the substrate intraplane distribution of the etching rate of the silicon oxide film, showing the effect of the gas-feeding shower plate for the plasma-forming gas to the plasma chamber of the present invention.

EXAMPLES

The examples of the present invention will be described below.
The embodiments of the present invention will be described below referring to the drawings.
The examples deal with the cases of applying the present invention to a film-forming apparatus 1 illustrated in FIG. 1, focusing on the process of removing native oxide film and organic matter formed on a Si substrate by the first step using a surface treatment apparatus 100 illustrated in FIG. 3.
A substrate 5 which is adopted as the sample is a Si single crystal substrate (with 300 mm in diameter) which is allowed to stand in a clean air to form a native oxide film thereon. The substrate 5 is transferred to a load-lock chamber 50 by a substrate transfer mechanism (not shown) to be placed therein. Then, the load-lock chamber 50 is evacuated by an evacuation system (not shown). After evacuating to a desired pressure, or 1 Pa or below, a gate valve (not shown) between the load-lock chamber and the transfer chamber is opened, and a transfer mechanism (not shown) in the transfer chamber transfers the substrate 5 to the surface treatment apparatus 100 via the transfer chamber 60, and places the substrate 5 on a substrate holder 114.
FIG. 3 illustrates the surface treatment apparatus 100 of the present invention.
The surface treatment apparatus 100 is composed of a treatment chamber 113 equipped with the substrate holder 114 on which the substrate 5 can be placed, and a plasma-forming chamber 108. The treatment chamber 113 and the plasma-forming chamber 108 are separated from each other by a plasma-confinement electrode plate 110 for plasma separation provided with a plurality of radical-passing holes 111.
The plasma-forming gas is fed from a plasma-forming gas supply system 101 to pass through a plasma-forming gas supply pipe 102, and enters a plasma-forming space 109 in the plasma-forming chamber 108 via plasma-forming gas feed holes 106 opened on a plasma-forming gas feed shower plate 107. With this arrangement, the plasma-forming gas can enter uniformly the plasma-forming space 109 in the plasma-forming chamber 108.
FIG. 20 illustrates the effect of plasma-forming gas feed shower plate 107 in the examples. The etching rate of the silicon oxide film on the substrate placed in the treatment chamber was determined using HF gas as the plasma-forming gas at a flow rate of 100 sccm, 0.01 W/cm²of high-frequency power density, and 50 Pa of treatment chamber pressure. In FIG. 20, the horizontal axis is a wafer position in the substrate plane, and the vertical axis is the etching rate of the silicon oxide film normalized by the etching rate at the center position. As shown in FIG. 20, when the case 901 which applied the plasma-forming gas feed shower plate is compared with the case 902 which did not apply the plasma-forming gas feed shower plate and applied lateral directional feed, as the feed method of the related art, the case 901 of feeding through the shower plate gave better uniformity in the in-plane etching rate. Presumable cause of the result is that the uniform gas feed to the plasma-forming space 109 secured uniform concentration distribution of active species in the plasma-forming space 109, and the phenomenon contributed to the result. Consequently, together with the effect of uniform plasma-forming owing to through-holes 105 of a high-frequency applying electrode 104 described below, there was confirmed further uniform radical supply to the treatment chamber.
The high-frequency applying electrode 104 extends along the plasma-forming gas feed shower plate 107 at above thereof or along the plasma-confinement electrode plate 110 for plasma separation at below thereof so as to divide the plasma-forming chamber 108 into two segments, upper one and lower one. The high-frequency applying electrode 104 is provided with through-holes 105. By applying high frequency power from a high frequency power source 103 to the high-frequency applying electrode 104, plasma is generated.
The plasma-confinement electrode plate 110 for plasma separation has a function of plasma-confinement electrode plate for plasma separation to partition the plasma-forming chamber 108 from the treatment chamber 113. The plasma-confinement electrode plate 110 is provided with the radical-feed holes 111 which allow radicals to pass therethrough to the treatment chamber 113, while rejecting the ions in the plasma in the plasma chamber.
The plasma-confinement electrode plate 110 for plasma separation has a hollow structure, and is provided with a plurality of treatment gas feed holes opened toward the treatment chamber. By supplying the treatment gas to the hollow structure, the treatment gas can be uniformly supplied to the treatment chamber via the plurality of treatment gas feed holes 112 opened toward the treatment chamber. The treatment gas feed holes 112 open in the vicinity of the respective radical feed holes 111. The treatment gas passes through a treatment gas supply pipe 115 from a treatment gas supply system 116, and enters the treatment chamber via the plurality of treatment gas feed holes 112 opened toward the treatment chamber. The radicals, originated from the plasma-forming gas, fed from the radical feed holes 111 and the molecules of treatment gas fed from the treatment gas feed holes 112 are mixed together in the treatment chamber 113 for the first time, and the mixture is then supplied to the surface of the substrate 5.
As described above, the radicals originated from the plasma-forming gas are fed to the treatment chamber 113 via the radical feed holes 111 formed on the plasma-confinement electrode plate 110 which partitions the treatment chamber 113 from the plasma-forming chamber 108. Only the molecules and atoms which are electrically neutral, such as radicals, are allowed to pass through the radical feed holes 111 opened on the plasma-confinement electrode plate 110 from the plasma-forming chamber 108 to enter the treatment chamber 113, and very few ions in plasma are allowed to enter the treatment chamber 113. In the plasma-forming chamber 108, when the ion density is about 1×10¹⁰count/cm³, the ion density in the treatment chamber becomes about 5×10²count/cm³, thus the ion density is decreased to less than one to ten million, which can be said that substantially very few ions enter the treatment chamber. In contrast, regarding the radicals, about several percentages to several tens of percentages of the generated ones, depending on the life, in the plasma-forming chamber are transferred to the treatment chamber.
The through-holes 105 in the high-frequency applying electrode 104 adopted the shape illustrated in FIG. 4. Since the electrode through-holes 105 allow the electrode to further uniformly discharge even at a low power of 0.25 W/cm²or less, the radicals are fed uniformly to the treatment chamber. The volume ratio of the total volume of a plurality of through-holes of the electrode V2 to the total volume of the high-frequency applying electrode including the through-holes V1, V2/V1, is preferably in a range from 0.01 to 0.8. When V2/V1<0.01, the deterioration of radical distribution appeared. When V2/V1>0.8, discharge failed.
The method of manufacturing a semiconductor device using the film-forming apparatus 1 illustrated in FIG. 1 of the present invention will be described below.
The description begins with the substrate treatment step as the first step, and with the condition of the step. The apparatus used in the first step is the substrate treatment apparatus 100 illustrated in FIG. 3.
As the plasma-forming gas, HF at 100 sccm of the flow rate was supplied to the plasma-forming chamber 108, thus generated plasma in the plasma-forming part. The radicals in the generated plasma were supplied to the treatment chamber 113 via the radical feed holes (radical passing holes) 111 formed in the plasma-confinement electrode plate 110 for plasma separation. To suppress the excitation energy of the radicals, HF as the treatment gas was supplied to the treatment chamber 113 via the treatment gas feed holes 112 at a flow rate of 100 sccm. The high frequency power density for plasma generation was 0.01 W.cm², the pressure was 50 Pa, the treatment time was 5 min, and the temperature of the substrate 5 was 25° C.
FIG. 12 shows the observed surface roughness after the first step of the present invention, with the comparison with the result of conventional dry-treatment and wet-treatment. As shown in FIG. 12, the surface roughness Ra obtained from the first step of the present invention was 0.18 nm, which is a good level almost equal to the surface roughness Ra of 0.17 nm obtained by the wet treatment (wet-cleaning) with a dilute hydrofluoric acid solution. For the case of not supplying the HF gas as the treatment gas, the surface roughness Ra became 2.0 nm, which is a rough level. Furthermore, even when the treatment time was extended to 10 min, the surface roughness Ra was confirmed to 0.19 nm, which is not a rough level. The improved surface flatness owes the selective removal of the surface native oxide film and organic matter in relation to Si. Presumable mechanism is that the high excitation energy HF generated from plasma is brought to collide with the unexcited HF separately fed as the treatment gas, thus forming HF having suppressed excitation energy, and the suppressed excitation energy HF selectively removes the surface native oxide film while not etching the Si atoms on the surface. The observed results confirmed that the use of the present invention can realize the surface flatness, equivalent to that of the wet-cleaning, by the dry-cleaning which does not need the high temperature pretreatment.
The condition to attain the surface flatness according to the present invention is only to form HF having suppressed excitation energy by mixing and colliding an HF having high excitation energy generated from the plasma with an HF of unexcited separately fed as the treatment gas. Consequently, the structure of the example is not limited if only the above condition is satisfied.
That is, according to this example, the radicals generated by the plasma are supplied to the substrate via the radical feed holes as the plurality of through-holes in the plasma-confinement electrode plate, while supplying the treatment gas via the plurality of treatment gas supply holes formed in the electrode plate. To obtain the flatness, however, the structure is not necessarily limited to the one given in this example, and the effect can be obtained by plasmatizing the gas containing HF gas, and by feeding solely the excited active species to the treatment chamber using an apparatus which allows only the neutral active species to pass therethrough while rejecting most of the ions, and further by feeding an unexcited HF gas from any part of the treatment chamber.
From the point of uniformity, however, and specifically when uniform treatment is required to a large diameter substrate, it is necessary to supply both the radicals and the unexcited treatment gas uniformly to the substrate. To this end, as in this example, it is preferable to adopt the structure which allows radicals to be shower-supplied from the electrode plate facing the substrate, and allows also the treatment gas to be shower-supplied at the same time.
Although the example conducts the radical generation by the plasma formation by the high frequency application, the radical generation may be done by the plasma formation by microwave and other methods. In detail, there can also be applied the radical generation through UV, X-ray, and microwave excitation given in FIG. 7, and the catalyst-chemical excitation given in FIG. 8. In FIG. 7, UV, X-ray, and microwaves are irradiated to the plasma gas from a feed chamber 203 to turn the plasma gas into plasma. In FIG. 7, reference numeral 5 signifies the substrate; 201, the plasma-forming gas supply system; 202, the plasma-forming gas supply pipe; 204, the plasma-confinement electrode plate for plasma separation provided with a plurality of radical-passing holes; 205, the radical feed hole; 207, the treatment chamber; 208, the substrate holder; 209, the treatment gas supply pipe; 210, the treatment gas supply system; and 211, the exhaust system. The treatment gas system has the same configuration as that of FIG. 3. FIG. 8 illustrates the configuration of turning the gas into plasma by a heating catalyst body 303. Reference numeral 5 signifies the substrate; 301, the plasma-forming gas supply system; 302, the plasma-forming gas supply pipe; 304, the plasma-confinement electrode plate for plasma separation provided with a plurality of radical-passing holes; 305, the radical feed hole; 306, the treatment gas feed hole; 307, the treatment chamber; 308, the substrate holder; 309, the treatment gas supply pipe; 310, the treatment gas supply system; and 311, the exhaust system. The treatment gas system has the same configuration as that of FIG. 3.
Regarding the plasma-forming gas fed to the plasma-forming chamber, the example used only HF. The plasma-forming gas is only required to contain at least HF, and specifically HF diluted with Ar may be used. By generating plasma, and by passing the plasma through the plasma-confinement electrode plate 110, the radicals enter the treatment chamber 113. For the treatment gas entering the treatment chamber 113, the example used only HF. The treatment gas is only required to contain at least HF, and specifically HF diluted with Ar may be used. By mixing the radicals which were fed to the treatment chamber 113 via the radical feed holes 111 opened on the plasma-confinement electrode plate 110 with the treatment gas fed from the treatment gas feed holes 112, there is created an atmosphere in which the excitation energy of radicals is suppressed. Then, the native oxide film and the organic matter on the surface of the substrate are selectively removed in relation to Si of the substrate material, thereby performing the substrate surface treatment while suppressing the surface roughening.
From the point of surface roughness after the substrate treatment, the fraction of HF flow rate to the total gas flow rate is preferably in a range from 0.2 to 1.0. The experimental result confirming the fraction range is described below.
FIG. 13 shows the dependency of the surface roughness on the HF mixing ratio in the case of using a mixed gas of HF with Ar as the plasma-forming gas and the treatment gas, respectively. As shown in FIG. 13, varying the mixing ratio of HF to Ar in the treatment gas varied the surface roughness after removing the native oxide film. Increase in the HF gas flow rate decreased the surface roughness. Even when the HF gas was used as the plasma-forming gas to be supplied to the plasma-forming chamber 108, and when the radicals were supplied via the radical feed holes 111 formed in the plasma-confinement electrode plate 110 for plasma separation, the case of supplying sole Ar as the treatment gas failed to remove the native oxide film on the substrate surface, and failed to attain the purpose of desired surface treatment. As for the case of supplying HF gas as the plasma-forming gas and of absence of the treatment gas, the surface roughness Ra became 2.5 nm, worsened compared with the case of using HF gas. The example used a Si substrate. However, the substrate surface treatment of the present invention does not limit to the surface treatment of Si substrate. In concrete terms, the request is only to structure the substrate surface with a group IV semiconductor such as Si and SiGe. More specifically, the substrate surface treatment can be applied to the one for removing native oxide film and organic contamination on the surface of group IV semiconductor such as thin Si layer which is adhered to or deposited on a glass substrate.
The high frequency power density applied onto the high-frequency applying electrode 104 is preferably in a range from 0.001 to 0.25 W/cm².
FIG. 6 shows the dependency of the native oxide film/Si, (etching rate ratio of native oxide film to Si), on the high frequency power density for the case of using HF gas as the plasma-forming gas and using HF as the treatment gas. Decrease in the high frequency power density suppresses the Si etching, and thus only the native oxide film is selectively etched. The value of the amount of etching the native oxide film divided by the amount of etching the Si is defined as “native oxide film/Si”. Decrease in the high frequency power density relatively decreases the amount of etching of Si so that the “native oxide film/Si” increases. On the other hand, increase in the high frequency power density significantly increases the etching of Si, thus decreasing the “native oxide film/Si”. Increase in the high frequency power density induces the etching of Si, which roughens the surface. To decrease the surface roughening, it is necessary to increase the “native oxide film/Si” and to decrease the high frequency power density. To this end, the high frequency power density is selected to above range of from 0.001 to 0.25 W/cm², preferably from 0.001 to 0.125 W/cm², and more preferably from 0.001 to 0.025 W/cm².
Then, the description is given to the Si and SiGe epitaxial single crystal growth step as the second step, and to the condition thereof.
The description is for the process in which the first step is conducted using the film-forming apparatus 1 given in FIG. 1 and using the surface treatment apparatus 100 given in FIG. 3 to remove the native oxide film formed on the Si substrate, then the substrate is transferred to a CVD apparatus 20 via the vacuum transfer chamber 60 to be subjected to the second step, which grows the Si and SiGe single crystal film on the treated surface of the substrate.
The substrate was treated on the surface thereof in the first step, and then was treated in the CVD apparatus 20 as the second step under the condition of: substrate temperature of 600° C., Si₂H₆supply at 36 sccm, pressure holding at 2E-3 Pa, for 3 minutes. After that, the substrate was treated therein under the condition of: substrate temperature of 600° C., Si₂H₆and GeH₄supply at 36 sccm, respectively, pressure holding at 4E-3 Pa, for 3 minutes. Thus treated substrate gave a surface roughness of the SiGe single crystal growth on the Si equivalent to the surface roughness of the substrate treated by wet cleaning using a diluted hydrofluoric acid, providing a good SiGe single crystal film, as shown in FIG. 14. As given in FIG. 15, compared with the case of wet cleaning followed by the above Si/SiGe growth, the case of this example gave smaller atom density of oxygen and carbon at the interface between the Si substrate and the grown Si. In concrete terms, the atom density of oxygen and carbon at the interface was 2×10²⁰atoms/cm³or less. The phenomenon owes to the suppress of adsorption of oxygen and carbon impurities onto the surface by the vacuum transfer of the substrate without exposing thereof to atmospheric air after cleaning. In the process of growth of Si and SiGe single crystal film in the CVD apparatus 20, there can be used: a hydrogenated gas such as Si₂H₆and GeH₄; a mixture of a hydrogenated gas with a doping material gas such as B₂H₆, PH₃, and AsH₃; or SiH₄instead of Si₂H₆.
The description is given to the dielectric film sputtering film-forming step as the third step, the oxidation-nitrification step of the formed dielectric film as the fourth step, and the electrode sputtering step as the fifth step.
Succeeding to the second step, the substrate is subjected to a process to manufacture the FET device. The process comprises: the third step of sputtering film-formation of the dielectric material in a sputtering apparatus 40 via the transfer chamber 60; the fourth step of transferring the substrate through the transfer chamber 60 to the oxidation-nitrification apparatus 30 to oxidize the dielectric material therein; and the fifth step of transferring the substrate through the transfer chamber 60 to the sputtering apparatus 40 to sputter the metal electrode material therein. The apparatus 10 through 50 are each controlled by the respective transfer or process controllers 70 through 74. The dielectric material film-forming in the third step may be done by CVD other than sputtering. Similarly, the film-forming of metal electrode material in the fifth step may be conducted by CVD other than sputtering.
With the surface treatment apparatus 100 illustrated in FIG. 3, the first step was conducted to remove the native oxide film, and the second step was conducted to grow the Si single crystal film. Then, the substrate 5 passed through the vacuum transfer chamber 60 to enter the dielectric-electrode sputtering apparatus 40 without exposing the substrate to atmospheric air, where the sputtering film-formation of Hf was conducted, and the substrate was transferred to the oxidation-nitrification apparatus 30 via the vacuum transfer chamber 60 to oxidize the formed dielectric material film without exposing the surface of the dielectric material to atmospheric air, thus conducted plasma and radical oxidation. Furthermore, the substrate 5 was transferred to the dielectric-electrode sputtering apparatus 40 via the vacuum transfer chamber 60 without exposing the substrate to atmospheric air, thus sputtered to form the film of TiN electrode. The characteristics of the obtained device were evaluated. The data are given in FIG. 16, FIG. 17, and FIG. 18.
FIG. 16 shows a C-V curve drawn by measuring the capacitance of a sample prepared by the present invention and by the related art (wet cleaning was applied instead of the first step), respectively, applying voltage to the electrode part. Compared with the sample of the related art which provided hysteresis of about 30 mV, the sample of the present invention attained good result of 10 mV of hysteresis.
FIG. 17 shows a comparison of the interface state density and the fixed charge density, between those obtained by the present invention and those obtained in the related art (wet cleaning was applied instead of the first step). Samples were prepared by the process of the present invention to determine the C-V curve, from which curve the interface state density and the fixed charge density were calculated. Both the interface state density and the fixed charge density were smaller than those in the related art because of the small quantity of oxygen and carbon impurities on the surface of Si film formed by the second step after the substrate cleaning in the first step, as shown in FIG. 15. The phenomenon is the effect of the continuous treatment in a vacuum after the dry-cleaning.
The film-forming apparatus 1 illustrated in FIG. 1 has a controller to conduct entire process in a vacuum, provided for each process apparatus and each transfer apparatus. That is, a transfer controller 70 receives the input signal generated from the apparatus concerned, at input part, runs the transfer program which was programmed so that the processor may operate according to the flowchart, and thus outputs the action command for transferring the substrate to each process apparatus via the vacuum transfer to the concerned apparatus. Process controllers A through D (71 through 74) receive the input signal from the process apparatus, run the program which was programmed so that the treatment is operated according to the flowchart, and thus output the action command to the apparatus concerned. The configuration of the controller 70 or controllers 71 to 74 is the one given in FIG. 2, composed of an input part 82, a memory part 83 having a program and data therein, a processor 84, and an output part 85. The configuration is basically a computer configuration, which controls the concerned apparatus.
FIG. 9 illustrates the control of the transfer controller 70 and the process controllers A to D (71 to 74). In Step 610, a Si substrate with native oxide film formed thereon is prepared. The transfer controller 70 conducts control so as to transfer the substrate using the load-lock apparatus 50, (Step 611). Further the transfer controller 70 generates the command to the surface treatment apparatus 100 to establish the vacuum of 1E-4 Pa or lower vacuum level, then moves the substrate 5 into the surface treatment apparatus 100 via the transfer chamber 60 to place the substrate on the substrate holder. The process controller A 71 controls the procedure of above-described first step of applying surface treatment to the substrate 5, (Step 613).
The transfer controller 70 controls the CVD film-forming apparatus 20 to evacuate to establish the vacuum of 1E-4 Pa or lower vacuum level, then moves the substrate 5 from the surface treatment apparatus 100 to the CVD film-forming apparatus 20 to place the substrate 5 therein via the transfer chamber 60.
The process controller B72 controls the above-described second step of treating single crystal growth in the CVD film-forming apparatus 20, (Step 615). Immediately after that, the process controller B72 moves the substrate into the dielectric-electrode sputtering apparatus 40 via the transfer chamber 60 to conduct the third step of dielectric-electrode sputtering film-forming, (Step 616).
The process controller C73 controls the third step of film-forming treatment in the dielectric-electrode sputtering apparatus 40, (Step 617). The transfer controller 70 establishes the vacuum of 1E-4 Pa or lower vacuum level in the oxidation-nitrification apparatus 30, and moves the substrate 5 from the dielectric-electrode sputtering apparatus 40 into the oxidation-nitrification apparatus 30 via the transfer chamber 60, (Step 618). The process controller D74 conducts control to execute the fourth step in the oxidation-nitrification apparatus 30, (Step 619). Immediately after that, the process controller D74 moves the substrate 5 into the dielectric-electrode sputtering apparatus 40 via the transfer chamber 60 to conduct the fifth step of metal electrode sputtering film-forming, (Step 620). The process controller C73 conducts control to execute film-forming treatment of example 3 in the dielectric-electrode sputtering apparatus 40, (Step 621). Then, the transfer controller 70 opens the transfer chamber 60 to atmospheric air using the load-lock apparatus 50, (Step 622).
By the above-described treatment of the present invention, the MOS field effect transistor (FET) 90 illustrated in FIG. 19 was manufactured. An HfO film was adopted as a dielectric gate insulation film 95 below a gate electrode 94 between a source region 92 and a drain region 93 of a Si substrate 91. Other than HfO, preferable gate insulation film 95 includes a film of Hf, La, Ta, Al, W, Ti, Si, Ge, or an alloy thereof, and more specifically there are applicable HfN, HfON, HfLaO, HfLaN, HfLaON, HfAlLaO, HfAlLaN, HfAlLaON, LaAlO, LaAlN, LaAlON, LaO, LaN, LaON, HfSiO, and HfSiON. The relative permittivity thereof is in a range from 3.9 to 100, and the fixed charge density is in a range from 0 to 1×10¹¹cm⁻². The film thickness of the gate insulation layer is set to a range from 0.5 to 5.0 nm.
The term “fixed charge” is also referred to as “fixed oxide film charge”, meaning the charge existing in SiO₂film and being fixed therein, not migrating in electric field or the like. The fixed oxide film charge appears caused by a structural defect in the oxide film, and depends on the formed state of the oxide film or the heat treatment thereof. Normally there exists a positive fixed charge in the vicinity of Si—SiO₂interface originated from a dangling bond of Si in silicon. The fixed oxide film charge makes the C-V characteristic of MOS structure shift in parallel along the gate voltage axis. The fixed charge density is determined by the C-V method.
As the gate electrode 94 of MOS-FET in FIG. 19, there are applied: metal such as Ti, Al, TiN, TaN, and W; polysilicon (B(boron)-dope: p-Type or P(phosphorus)-dope: n-Type); and Ni-FUSI (fully silicide).
The semiconductor/insulation film joint, which was prepared by the method of the present invention, that is, by the method of treating the surface of a Si substrate having native oxide film formed thereon, growing the Si single crystal film without exposing thereof to atmospheric air, sputtering for forming a dielectric film such as Hf without exposing the substrate to atmospheric air, and oxidizing and nitrifying thereof, gives smaller fixed charge and lower interface state than those of the joint prepared in the atmospheric transfer. Therefore, the joint gives a C-V curve with small hysteresis as shown in FIG. 16, with small leak current, thereby providing good device characteristics. The term “interface state” signifies the energy level of electron being appeared on interface of joint of different kinds of semiconductors and on interface of joint between a semiconductor and a metal or an insulation material. Since the semiconductor face on the interface becomes a condition of breaking bond between atoms, there appears a non-bonding condition called the dangling bond, thus creating an energy level to allow entrapping the charge. Also impurity or defect on the interface creates an energy level allowing entrapping the charge, or an interface state. Generally the interface state shows a long response time and is instable, thus often adversely affects the device characteristics. Lower interface state means better interface. The interface state density is determined by the C-V method.
As illustrated in FIG. 1, the film-forming apparatus of the present invention uses the configuration having each one of: the surface treatment unit 100, the CVD film-forming unit 20, the dielectric-electrode sputtering unit 30, the oxidation-nitrification unit 40, the load-lock chamber 50, and the transfer chamber 60. However, the quantity of each of those units is not necessarily one, and more than one unit for there each can be applied depending on the throughput, the film structure, and the like. For example, to increase the throughput, the load-lock chamber may be substituted by a plurality of load-lock chambers allotting the functions of loading and unloading to each one. Furthermore, for example, the sputtering unit 30 may be substituted by two or more sputtering units allotting the functions of forming the dielectric film and forming the electrode to each one.
However, for effective use of the substrate treatment method which allows conducting the dry substrate surface treatment while keeping flat surface according to the present invention, it is preferable to have at least one unit for each of the surface treatment unit 100, the CVD film-forming unit 20, the load-lock chamber 50, and the transfer chamber 60. With this configuration, the presence of load-lock chamber makes the dry substrate surface treatment possible at high throughput in a stable evacuated atmosphere, and the film-forming by transferring the substrate to the CVD film-forming unit via the transfer chamber in a vacuum without exposing the substrate to atmospheric air allows keeping good condition of interface between the Si substrate surface and the CVD film-formed Si/SiGe layer.
In addition, to effectively use the substrate treatment method which allows treating the dry substrate surface while keeping flat surface according to the present invention, it is preferable to have at least one unit for each of the surface treatment unit 100, the dielectric-electrode sputtering unit 30, the load-lock chamber 50, and the transfer chamber 60. With this configuration, the presence of load-lock chamber makes the dry substrate surface treatment possible at high throughput in a stable evacuated atmosphere, and the film-forming by transferring the substrate to the dielectric-electrode sputtering unit 30 via the transfer chamber in a vacuum without exposing the substrate to atmospheric air allows keeping good condition of interface between the Si substrate surface and the dielectric film or conductive film as the base of the insulation film prepared by sputtering on the Si substrate surface.
Although the example does not give the detail of the CVD film-forming unit 20 in the drawing, any type of epitaxial film-forming unit is applicable if only the unit is provided with a chamber, a substrate-heating mechanism for heating both the substrate holder for holding the substrate and the substrate held thereto, a gas-feed mechanism for supplying a gas containing the raw material gas to conduct the CVD film-formation, and an exhaust means for discharging the chamber atmosphere.
Similarly the detail of the sputtering unit 30 is not given in the drawing. The sputtering unit 30 may be, however, any type if only the unit has a chamber, a substrate holder for holding the substrate, a mechanism for feeding the gas into the chamber, an exhaust means for discharging the chamber atmosphere, a sputtering cathode for mounting the target made of dielectric or conductive metal, and a high frequency power supply mechanism or a direct current power supply mechanism.
The quantity of the sputtering cathode for mounting the target made of dielectric or conductive metal, (not shown), in the sputtering unit 30 is not necessarily one, and a plurality of sputtering cathodes may be applied for forming a plurality of continuous or discontinuous films and for mounting a plurality of targets thereon. From the point of uniformity of the thickness distribution of the formed film, the substrate holder is preferably provided with a rotary mechanism to rotate the mounted substrate. For allowing film-forming by reactive sputtering, the gas-feed mechanism of the sputtering unit 30 preferably feeds not only inert gas such as Ar but also a reactive gas such as N₂and O₂, or a mixture of reactive gas with Ar gas.

Claims

1.-22. (canceled)

23. A method of treating a surface of semiconductor substrate placed in a treatment chamber, comprising the steps of:

generating plasma by exciting a plasma-forming gas containing HF in a plasma-forming chamber;

selectively feeding a radical in the plasma from the plasma-forming chamber to the treatment chamber;

feeding a treatment gas containing unexcited HF into the treatment chamber; and

treating the surface of the semiconductor substrate by an atmosphere of a mixture of the radical and the treatment gas, fed into the treatment chamber.

24. A method of claim 23, wherein the treatment of gas contains at least HF by a fraction from 0.2 to 1.0 to the total amount of the treatment gas, and preferably the treatment gas is composed of substantially HF.

25. A method of claim 23, wherein the plasma-forming gas is composed of substantially HF.

26. A method of claim 23, wherein the selective feeding of the radical to the treatment chamber is conducted by feeding the radical from the plasma chamber to the treatment chamber, allowing the radical to pass through a radical-passing hole formed in a plasma-confinement electrode plate partitioning the plasma chamber from the treatment chamber, while rejecting ions in the plasma.

27. A method of claim 23, wherein the semiconductor substrate is a Si substrate, and the cleaning treatment of the Si substrate is conducted after removing native oxide film on the Si substrate by etching.

28. A method of forming a gate insulation film of MOS structure, comprising the steps of:

cleaning the surface of a Si substrate by the method of claim 27;

transferring the surface-cleaned Si substrate to an expitaxial chamber without exposing the Si substrate to atmospheric air, and forming an expitaxial layer on the surface-cleaned Si substrate;

transferring the Si substrate having the expitaxial layer formed thereon to a sputtering chamber without exposing the Si substrate to atmospheric air, and forming a dielectric film on the epitaxial layer by sputtering; and

transferring the Si substrate having the dielectric film formed thereon to an oxidation-nitrification chamber without exposing the Si substrate to atmospheric air, and oxidizing, nitrifying, or oxnitrifying the dielectric film to form the gate insulation film.

29. A method of claim 28, wherein the dielectric film is made of the one selected from the group consisting of Hf, La, Ta, Al, W, Ti, Si and Ge, or an alloy thereof.

30. An apparatus of treating a semiconductor substrate, including a treatment chamber for treating the surface of the semiconductor substrate, comprising:

a plasma-forming chamber generating plasma by exciting a plasma-forming gas containing HF;

means for selectively feeding a radical in the plasma from the plasma-forming chamber to the treatment chamber; and

means for feeding a treatment gas containing unexcited HF into the treatment chamber, and

thus treating the surface of the semiconductor substrate by an atmosphere of a mixture of the radical and the treatment gas, fed into the treatment chamber.

31. An apparatus of treating a semiconductor substrate of claim 30, wherein the means for selectively feeding the radical to the treatment chamber is a plasma-confinement electrode plate which partitions the plasma chamber from the treatment chamber, and the plasma-confinement electrode plate has a radical-passing hole formed which connects the plasma chamber with the treatment chamber, thus feeding the radical through the radical-passing hole from the plasma chamber to the treatment chamber, while rejecting ions in the plasma.