JP2010053380A - Method of depositing amorphous silicon carbide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently and inexpensively depositing an amorphous silicon carbide (a-SiC<SB>x</SB>:H) film having the hardness necessary for a coating material of a cutting tool or the like by a simple process. <P>SOLUTION: When depositing an amorphous silicon carbide film on a substrate by using raw material gas containing silicon compounds by a microwave plasma CVD (Chemical Vapor Deposition) method, negative high frequency bias voltage (-V<SB>RF</SB>) is continuously applied to the substrate. Preferably, the output of the microwave is 50-120 W, and the negative high frequency bias voltage (-V<SB>RF</SB>) satisfies inequalities 60 V<-V<SB>RF</SB><120 V. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to amorphous silicon carbide (a-SiC _x : H) which is one of hard thin film materials used for cutting tools, dies, wear-resistant parts, protective films for storage media such as optical disks and magnetic disks, and the like. The present invention relates to a film forming method.

Currently, a hard carbon material called diamond-like carbon (DLC) is widely used as a coating material for cutting tools and the like. However, as a reverse of the fact that the DLC film is hard, the internal stress of the film is high, the adhesion to the base material is low, the film is easily peeled off, and a uniform film having the required film thickness is formed. There is a problem that it is difficult.

In order to solve such problems, various laminated materials in which a DLC film is formed after an intermediate layer such as a silicon carbide film is formed on the surface of a substrate have been proposed. (For example, see Patent Documents 1 and 2)
JP 2001-214269 A JP 2000-176705 A

However, in order to produce such a laminated material, it is necessary to employ a complicated process, and there is a drawback that the manufacturing cost increases.
On the other hand, a hard film made of crystalline or amorphous silicon carbide is also known, but its hardness is about 10-30 GPa, which is insufficient for use as a coating material for cutting tools and the like.

In view of such a current situation, the present invention provides a method for efficiently and inexpensively forming an amorphous silicon carbide (a-SiC _x : H) film having a hardness required as a coating material for a cutting tool or the like by a simple process. The purpose is to provide.

In this invention, in order to solve the said subject, the structure of the following 1-7 is employ | adopted.
1. When an amorphous silicon carbide film is formed on a substrate using a source gas containing a silicon compound by a microwave plasma CVD method, a negative high-frequency bias voltage (−V _RF ) is continuously applied to the substrate. A method for forming an amorphous silicon carbide film.
2. 2. The method of forming an amorphous silicon carbide film according to 1, wherein the microwave output is 50 to 120 W and the negative high-frequency bias voltage (−V _RF ) is 60 V <−V _RF <120 V.
3. 3. The method for forming an amorphous silicon carbide film according to 1 or 2, wherein a gas containing tetramethylsilane and argon at a ratio of tetramethylsilane / argon = 0.001 to 0.1 is used as a source gas.
4). 4. The method for forming an amorphous silicon carbide film according to any one of 1 to 3, wherein a raw material gas that has been dehydrated in advance is used as the raw material gas.
5). The method for forming an amorphous silicon carbide film according to any one of 1 to 4, wherein the amorphous silicon carbide film has a hardness of 30 to 70 GPa.
6). The method for forming a hard carbon nitride film according to any one of 1 to 5, wherein the atomic ratio [C] / [Si] of carbon to silicon of the amorphous silicon carbide film is 1.1 to 1.8.
7). The method for forming an amorphous silicon carbide film according to claim 1, wherein the substrate has a surface selected from silicon, silicon carbide, and silicon nitride.

  According to the present invention, an amorphous silicon carbide film having a hardness sufficient as a coating material for a cutting tool or the like, which has been extremely difficult to form with the prior art, can be efficiently produced at a low cost using a simple apparatus. Can be formed. The present invention makes it possible to efficiently form an amorphous silicon carbide film having a high hardness, a smooth surface and a uniform surface on a substrate without requiring large-scale and expensive equipment, and has practical value. It is extremely expensive.

In the present invention, when an amorphous silicon carbide film is formed on a substrate using a source gas containing a silicon compound by a microwave plasma CVD method, a negative high-frequency bias voltage (−V _RF ) is continuously applied to the substrate. Thus, an amorphous silicon carbide film is formed in one step.
The microwave frequency is preferably 2.45 GHz, for example, and the output is preferably about 50-120 W. The negative high-frequency bias voltage (−V _RF ) applied to the substrate is preferably about 60V <−V _RF <120V.

Preferable silicon compounds used as the source gas include, for example, tetramethylsilane (TMS), trimethylsilane, dimethylsilane, and the like. The silicon compound is mixed with an inert gas such as argon, helium, nitrogen, etc., and used as a raw material gas. The mixing ratio of the silicon compound and the inert gas is silicon compound / inert gas = 0.001 to 0.001 by volume ratio. It is preferably about 0.1.
As a particularly preferable raw material gas, a gas containing tetramethylsilane and argon in a ratio of tetramethylsilane / argon = 0.001 to 0.1 can be given.

  The raw material gas is preferably dehydrated with a dehydrating agent such as phosphorus pentoxide before being introduced into the reactor. By using the raw material gas subjected to dehydration treatment, it is possible to obtain amorphous silicon carbide having higher hardness.

  Although there is no restriction | limiting in particular as a board | substrate which forms an amorphous silicon carbide film by this invention, It is preferable to use what has the surface selected from silicon, silicon carbide, and silicon nitride. As these substrates, not only a substrate composed of a single material composed of the above materials but also a composite material having a coating composed of the above materials on the surface of another base material can be used.

  According to the present invention, the hardness of an amorphous silicon carbide film is 30-70 GPa, and a hard amorphous silicon carbide film that cannot be realized with a conventional hard film composed of crystalline or amorphous silicon carbide is obtained. Can do. The atomic ratio [C] / [Si] of carbon to silicon of the amorphous silicon carbide film obtained by the present invention is considered to be about 1.1-1.8.

Next, examples of the present invention will be described with reference to the drawings. However, the following specific examples do not limit the present invention.
FIG. 1 is a schematic view showing an example of an apparatus used in the method for forming an amorphous silicon carbide film of the present invention. This apparatus comprises a stainless steel vacuum vessel 1 and pipes 2 and 3 associated therewith, a vacuum pump (not shown), microwave discharge portions 4, 5 and 6, and high frequency bias applying portions 7, 8, 9 and 10. Is done.

The vacuum reaction vessel 1 is connected in series by a mechanical booster pump (pumping speed 110 m ³ / h) and an oil rotary vacuum pump (pumping speed 600 l / min), and the ultimate vacuum is 1 mTorr (0.13 Pa) or less. A discharge tube 2 made of Pyrex (registered trademark) glass is attached to the upper part of the vacuum reaction vessel 1. A stainless steel nozzle (inner diameter 1 mmφ) 13 is installed on the side wall of the reaction vessel via a Pyrex (registered trademark) glass joint. The distance between the tip of the discharge tube 2 and the tip of the nozzle 13 was 4 mm. Further, the substrate stage 11 was installed 11 mm downstream of the nozzle tip 13. The substrate stage 11 is supported by a partition plate 18 having an exhaust hole. The substrate stage 11 is electrically insulated from the vacuum reaction vessel 1 so that a high frequency voltage can be applied thereto via a 13.56 MHz high frequency power source 7 and a matching box 8. When a high frequency voltage is applied, a negative self-bias −V _RF is generated in the substrate stage 11. The direct current component was read by the digital multimeter 10 through the filter circuit 9 to obtain −V _RF .

Argon gas was allowed to flow through the discharge tube 2, and microwave discharge was performed with a discharge device in which the power source 4, the magnetron 5, and the waveguide 6 were combined. The frequency of the microwave was 2.45 GHz, and the output was 100 W. The pressure of Ar gas in the vacuum vessel 1 was 0.1 Torr (13 Pa). Through the nozzle 13, a vapor of tetramethylsilane (hereinafter abbreviated as TMS), about 1/20 (volume ratio) of Ar gas, was introduced. Since the pressure of TMS vapor is much lower than that of Ar, accurate measurement in the vacuum reaction vessel 1 was impossible, but it was 5 mTorr (0.6 Pa) or less. Both Ar gas and TMS adjusted the pressure using a needle valve (not shown). Further, in order to prevent moisture adsorbed in the pipes (14 and 3 respectively) for introducing Ar and TMS from entering the reaction region, Ar and TMS are dehydrating agents (P ₂ O ₅ ) installed in the middle of the pipes. ) Was passed through the glass cells 15 and 16. A single crystal Si substrate 12 cut out to a size of 10 mm × 10 mm was placed on the substrate stage 11 to form a thin film. By appropriately setting the output of the high-frequency power source 7, -V _RF was changed from 0 to 120V. Cooling water was circulated through the pipe 17 inside the substrate stage 11. The deposition time was 30 minutes and the film thickness was in the range of 1-5 μm.

When X-ray diffraction was performed on each of the obtained thin films, no clear diffraction was shown in any of the thin films, so that it was determined to be amorphous.
Further, as a result of elemental analysis by X-ray photoelectron spectroscopy (XPS) using JPS-9010 manufactured by JEOL Ltd., signals of Si2p and C1s appeared at 153 eV and 285 eV, respectively. The XPS spectrum of thin film formed by -V _RF = 0V is shown in FIG.
Table 1 shows the results of XPS measurement for thin films formed at −V _RF = 0V and 100V.

In this measurement, by operating an Ar etching apparatus attached to the apparatus, the surface of the thin film is etched by Ar ⁺ ions, and the composition of the thin film changes. Therefore, Table 1 shows the measured values before and after etching with Ar ⁺ ions. Note that −V _RF = 0V is a control example in which a negative high-frequency bias voltage is not applied to the substrate.
As a result of elemental analysis, the value of x in the amorphous silicon carbide (a-SiC _x : H) film was in the range of 1.06-1.73. The value of x -V _RF = 100 V is resulted slightly larger than the value of _{-V RF} = 0V. X tended to decrease before and after etching with Ar ions, but the magnitude of the decrease was 0.26 when −V _RF = 0V, whereas 0.47 when −V _RF = 100V. And showed a large value. From this, it was suggested that a layer having a higher C atom ratio was formed near the film surface at −V _RF = 100 V than at −V _RF = 0V.

FIG. 3 shows the results of measuring the hardness of the thin film formed at −V _RF = 0V, 50V and 100V using an ultra-fine indentation hardness measuring instrument (Fisher H-100). In this measurement, the film hardness was determined from the maximum indentation depth using a Berkovitch indenter and applying a maximum load of 7 mN.
In FIG. 3, (a), (b), and (c) correspond to −V _RF = 0, 50, and 100 V, respectively. □ corresponds to when the load is increased (load curve), ◇ corresponds to when the load is decreased (unloading curve). The maximum indentation depth was (a) 409 nm, (b) 112 nm, and (c) 62 nm. When these values were converted into film hardness, they were (a) 1.6 GPa, (b) 21 GPa, and (c) 69 GPa. Since the hardness of the single crystal SiC is 20-25 GPa, the hardness obtained in (c) of the present invention is much higher than this. The cause of this is under investigation, but considering the results of elemental analysis and the like, the a-SiC _x : H thin film prepared under the condition of applying a high-frequency bias does not show crystallinity in the vicinity of the surface, but C atoms It is presumed that a layer containing a large amount of Si was formed and the hardness was higher than that of the original SiC.

FIG. 4 shows the relationship between applied negative high-frequency bias voltage and film hardness for a-SiC _x : H thin films formed at −V _RF = 0V, 20V, 40V, 60V, 80V, 100V and 120V. The horizontal axis of FIG. 4 indicates −V _RF value (V), and the vertical axis indicates film hardness (GPa). According to FIG. 4, when -V _RF is 60 V or less, the maximum hardness is about the same as that of crystalline SiC. However, when -V _RF exceeds 80 V, the variation in hardness increases, and the value of the maximum hardness is extremely large. A bigger result was obtained. Furthermore, the hardness value decreased at −V _RF = 120V.
Therefore, when the present invention is applied as a coating technique, the negative high-frequency bias voltage (−V _RF ) applied to the substrate is preferably about 60 V <−V _RF <120 V, and −V _RF = 100 V It is particularly preferable to set the degree.

FIG. 5 shows a measurement example of the infrared absorption spectrum of the thin film obtained in the present invention. In FIG. 5, (a), (b), and (c) are thin film spectra corresponding to −V _RF = 0, 50, and 100 V, respectively.
In each spectrum, Si-C stretching vibration 670-760cm ^-1, CH deformation vibration derived from Si-CH ₃ and Si- _{(CH 2)} n structure -Si around 1000 cm ^-1, around 1250 cm ^-1 Si-CH ₃ target bending vibration, Si-H stretching vibration 2100 cm ^-1, CH stretching vibration was observed at 2700-3000cm ^-1. -V As _RF is _{increased, Si-CH 3, Si- (} CH 2) n oscillation modes -Si, Si-H and CH, the intensity decreased. This suggests that when a high-frequency bias voltage is applied, a negative direct current component (-V _RF ) appears on the substrate stage, and Ar ⁺ ions are attracted and ion bombards the film surface, thereby desorbing hydrogen atoms. is doing. This triggers the modification of the bond, which is considered to induce hardening of the film. Further, since the infrared spectrum was not observed stretching vibration of OH groups (3500 cm _^-1), it was confirmed that the dehydration by P 2 _{O 5} is working effectively.

The results of Raman scattering spectra measured for these thin films are shown in FIG. In FIG. 6, (a), (b), and (c) are the thin film spectra corresponding to −V _RF = 0, 50, and 100 V, respectively.
In (a) where no negative high-frequency bias voltage was applied to the substrate, no signal due to Raman scattering was detected, and only a background derived from fluorescence was observed. This suggests that when a high-frequency bias voltage is applied and ion bombardment is not performed, the chemical structure of the film mainly forms a one-dimensional conjugated system and includes many hydrogen termination structures. On the other hand, in (b) and (c), the background derived from the conjugated system disappeared, and instead, a G band derived from the graphite structure was observed in the vicinity of 1450 cm ⁻¹ . Usually, since the wave number of the G band of the carbon material appears in the vicinity of 1550 cm ⁻¹ , the shift to the low wave number side of the Raman scattering signal observed in the present invention is that some of the carbon atoms in the graphite structure are replaced with Si atoms. It is estimated that this is because the converted mass has increased. The observed changes from (a) to (b) and (c) resulted in bond modification from a one-dimensional structure to a two-dimensional structure due to desorption of hydrogen atoms by ion bombardment on the film surface. This is consistent with the result of the infrared absorption spectrum of FIG.

  The above examples illustrate the method for forming an amorphous silicon carbide film of the present invention. Therefore, the size of the apparatus, the positional relationship of each member, the operating conditions, etc. can be changed as needed.

It is a schematic diagram which shows an example of the apparatus used for the formation method of the amorphous silicon carbide film | membrane of this invention. It is a figure which shows the XPS spectrum of an amorphous silicon carbide film. It is a figure which shows the result of having measured the hardness of the amorphous silicon carbide film | membrane obtained in the Example of this invention. It is a figure which shows the relationship between the applied negative high frequency bias voltage and film | membrane hardness about the amorphous silicon carbide film obtained in the Example of this invention. It is a figure which shows the infrared absorption spectrum of the amorphous silicon carbide film | membrane obtained in the Example of this invention. It is a figure which shows the Raman scattering spectrum of the amorphous silicon carbide film | membrane obtained in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum reaction vessel 2 Discharge tube 3,14,17 Piping 4 Power supply 5 Magnetron 6 Waveguide 7 High frequency power supply 8 Matching box 9 Filter circuit 10 Digital multimeter 11 Substrate stage 12 Substrate 13 Nozzle 15 and 16 Glass cell 18 Partition plate

Claims (7)

When an amorphous silicon carbide film is formed on a substrate using a source gas containing a silicon compound by a microwave plasma CVD method, a negative high-frequency bias voltage (−V _RF ) is continuously applied to the substrate. A method for forming an amorphous silicon carbide film. 2. The method of forming an amorphous silicon carbide film according to claim 1, wherein the microwave output is 50 to 120 W and the negative high-frequency bias voltage (−V _RF ) is 60 V <−V _RF <120 V. 3.   3. The method for forming an amorphous silicon carbide film according to claim 1, wherein a gas containing tetramethylsilane and argon at a ratio of tetramethylsilane / argon = 0.001 to 0.1 is used as a source gas. .   The method for forming an amorphous silicon carbide film according to claim 1, wherein a raw material gas that has been subjected to a dehydration process in advance is used as the raw material gas.   The method for forming an amorphous silicon carbide film according to claim 1, wherein the amorphous silicon carbide film has a hardness of 30 to 70 GPa.   6. The formation of a hard carbon nitride film according to claim 1, wherein the atomic ratio [C] / [Si] of carbon to silicon of the amorphous silicon carbide film is 1.1 to 1.8. Method. The method for forming an amorphous silicon carbide film according to claim 1, wherein the substrate has a surface selected from silicon, silicon carbide, and silicon nitride.

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