JP2006077302A - Method for producing silicon carbide member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silicon carbide member with excellent productivity where, as a base material for CVD (Chemical Vapor Deposition)-SiC, a repeatedly usable base material which is easily removable from the CVD-SiC, and does not generate cracks, fractures and impurity contamination on the CVD-SiC is adopted. <P>SOLUTION: The method for producing a silicon carbide member is characterized in that, after the formation of an intermediate layer dissolvable with a chemical on a base material, a silicon carbide film is deposited on the surface of the intermediate layer by a CVD process, so as to be a silicon carbide body, subsequently, the intermediate layer is dissolved away with a chemical, and the silicon carbide body is separated from the base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a silicon carbide member by a CVD method.

  Silicon carbide body (CVD-SiC) manufactured by CVD (chemical vapor deposition) is a dense body, excellent in corrosion resistance, etc., and high in purity, so it is suitable for use as various parts and jigs for semiconductor manufacturing. Has been.

  As a method for producing CVD-SiC, a method is known in which SiC is deposited on a substrate by CVD and then the substrate is burned off. For example, there is a method in which graphite is used as a base material and the graphite base material is burned off after CVD (Patent Document 1). However, this method generally does not allow repeated use of the base material, and it is difficult to completely burn out the graphite base material with a long member such as a tubular body, particularly a tubular body with one end closed. There was a problem such as need. Moreover, cracks and cracks may occur in CVD-SiC due to the difference in thermal expansion coefficient between graphite and SiC.

  As a method for producing CVD-SiC of a tubular body, a method of performing CVD treatment by connecting a plurality of cylindrical base materials in series in a reaction chamber using a graphite cylindrical base material has been proposed (Patent Document 2). There is no specific proposal for a method for removing the graphite substrate.

As a method other than burning out the base material, a method is proposed in which Al ₂ O ₃ having a coefficient of thermal expansion significantly different from that of SiC is used for the base material, and the base material is simply separated by a temperature drop without burning the base material. However, it is difficult to produce a high-purity Al ₂ O ₃ base material and there are problems such as impurity contamination to CVD-SiC. From the same point of view, a method has been proposed in which pyrolytic boron nitride (pBN), which has a thermal expansion coefficient significantly different from that of SiC, is used for the base material, and the base material is simply separated by a temperature drop without burning the base material. However, although pBN can be highly purified, it takes time and cost to form a structure like a base material, and thus there are problems in terms of productivity and cost.

  As a method for dissolving and removing the base material, a method of dissolving and removing it with an acid or alkali using a metal such as Al or Ni as a base material, or a method of dissolving and removing it with an organic solvent using a synthetic resin as a base material has been proposed ( Patent Document 5), in the case of the metal, there is a problem that cracks and cracks occur in CVD-SiC because of the large difference in thermal expansion coefficient from SiC. In the case of the synthetic resin, the temperature exceeds 1000 ° C. In reality, there is nothing that can maintain the shape without softening and burning up to a high temperature.

Japanese Examined Patent Publication No. 62-43333 (Claims) JP 2001-240966 A (Claims) JP-A-5-124863 (Claims) JP-A-5-124864 (Claims) JP-A-1-290520 (Means for Solving the Problems, page 2)

  The present invention employs a base material that can be repeatedly used as a base material for producing CVD-SiC, can be easily separated from CVD-SiC, and does not generate cracks, cracks, or impurity contamination in CVD-SiC. An object of the present invention is to provide a method for producing a silicon carbide member having excellent productivity.

  In the present invention, an intermediate layer that can be dissolved with a chemical solution is formed on a substrate, a silicon carbide film is formed on the surface of the intermediate layer by a CVD method to form a silicon carbide body, and then the intermediate layer is dissolved with a chemical solution. And removing the silicon carbide body from the substrate to provide a method for producing a silicon carbide member.

  The present invention is a manufacturing method in which an intermediate layer that can be dissolved with a chemical solution is formed on a substrate, and after the end of CVD, the intermediate layer is removed with a chemical solution to obtain CVD-SiC. Therefore, the substrate can be used repeatedly. . Moreover, since there is no burning process of the base material, the base material can be easily separated even in a long product such as a tubular body, which is excellent in terms of productivity and cost.

  Further, when the intermediate layer is formed of an amorphous Si film or a poly-Si film, it is highly pure, so that impurity contamination to CVD-SiC can be prevented, and the difference in thermal expansion coefficient between SiC and Si is small, so that CVD- Does not cause defects such as cracks and cracks in SiC.

  The method for producing a silicon carbide member of the present invention (hereinafter referred to as the present production method) is a substrate in which an intermediate layer (hereinafter referred to as a dissolvable intermediate layer) that can be dissolved with a chemical solution is formed on the surface when producing CVD-SiC Is used.

  In the present production method, the substrate is not particularly limited as long as it can form the dissolvable intermediate layer on the surface thereof, but is preferably high-purity. Suitable base materials include graphite, glassy carbon, graphite converted to silicon carbide by chemical reaction, sintered silicon carbide, recrystallized silicon carbide, recrystallized silicon carbide impregnated with silicon, reaction sintered silicon carbide Examples include a reaction sintered body, a sintered body impregnated with silicon, a SiC film formed on the surface of these bulk bodies by a CVD method, CVD-SiC, and the like.

  In particular, if the base material is made of CVD-SiC, there is no difference in the thermal expansion coefficient between the base material and the product member, so cracks and cracks due to the difference in the thermal expansion coefficient can be prevented, and high purity. It is particularly preferable from the viewpoints that there is no impurity contamination on the product member, high strength, excellent handling properties, high corrosion resistance, and durability against CVD reaction gas.

The surface of the substrate is preferably flat and smooth because it becomes easier to separate the CVD-SiC from the substrate after removing the dissolvable intermediate layer formed on the surface. In this case, the surface roughness R _max of the substrate surface is preferably 20 μm or less, or _Ra is 2 μm or less.

In the present production method, the composition of the dissolvable intermediate layer is not particularly limited as long as it can be dissolved in a chemical solution, has a small difference in thermal expansion coefficient from the product member, has heat resistance, and has a high purity. Not. It is preferable that the dissolvable intermediate layer is soluble in acid or alkali because it can be easily removed with a chemical solution, and an Si-based semiconductor thin film such as an amorphous Si film, a poly-Si film, a doped Si film, or a single-crystal Si film, silicon Semiconductor thin films such as germanium films and germanium films, tungsten films, molybdenum films, Al films, MoSi ₂ films, W-Ti films, WSi ₂ films, metal films such as Cr films, SiO ₂ films, PSG (phosphorus glass) films Preferred examples include glass films such as BSG (boron glass) film, BPSG (boron / phosphor glass) film, oxide films such as Al ₂ O ₃ film, and nitride films such as Si ₃ N ₄ .

  It is particularly preferable that the dissolvable intermediate layer is a Si-based film in order to satisfy the above conditions. Preferred examples of the Si film include an amorphous Si film (hereinafter abbreviated as a-Si film) and a poly Si film (hereinafter abbreviated as p-Si film).

  The a-Si film can be manufactured by sputtering, vapor deposition, CVD, or the like. For example, a CVD method in which a source gas such as disilane is decomposed by heat or plasma to form a deposited film is an example. The CVD method may be referred to as a low pressure CVD method or an LPCVD method when performed under a reduced pressure of about 10 to 15000 Pa, or may be referred to as a plasma CVD method when the decomposition means is plasma.

  The p-Si film can be manufactured by crystallizing the a-Si film. As an example, there is a method in which an a-Si film formed by a CVD method is subjected to solid phase growth by thermal annealing at 600 ° C. or lower. Instead of heat treatment, it can also be produced by irradiating with an excimer laser and annealing to melt and recrystallize the a-Si film. In addition to these methods, it can also be produced by a liquid phase growth method, a vapor phase growth method such as a CVD method, or a solid phase growth method such as thermal annealing.

  In this production method, the thickness of the dissolvable intermediate layer is preferably 1 to 1000 μm. If the thickness of the dissolvable intermediate layer is less than 1 μm, even if the dissolvable intermediate layer is dissolved and removed with a chemical solution, such as CVD-SiC is directly formed on the substrate due to local non-uniform film thickness, May not be completely separated from CVD-SiC.

  On the other hand, if the thickness of the dissolvable intermediate layer exceeds 1000 μm, cracks and cracks may be generated due to the difference in thermal expansion coefficient between the dissolvable intermediate layer and the product CVD-SiC. Moreover, it takes time and money to form the dissolvable intermediate layer more than necessary, which is not preferable in terms of cost. The thickness of the dissolvable intermediate layer is more preferably 30 to 800 μm, and further preferably 50 to 600 μm.

  In this production method, when CVD-SiC is formed, depending on the shape of the obtained CVD-SiC, the dissolvable intermediate layer is covered with the obtained CVD-SiC, and is immersed in the chemical solution as it is. In this case, the dissolvable intermediate layer may not be substantially removed. In that case, it is desirable to delete a part of the obtained CVD-SiC by some means so that the dissolvable intermediate layer can directly contact the chemical solution. An example of such means is mechanical processing such as grinding or cutting. Note that instead of deleting a part of such CVD-SiC, some other alternative means such as masking the part may be adopted.

  The chemical solution is not particularly limited as long as it can dissolve and remove the dissolvable intermediate layer, but preferred are acids and alkalis. For example, when the dissolvable intermediate layer is an a-Si film or a p-Si film, it is preferable to use hydrofluoric acid, nitric acid or hydrofluoric acid as a chemical solution because dissolution and removal can be easily performed. Although there is no restriction | limiting in particular about the density | concentration of these acids and alkalis, it is preferable in it being 10-70 mass%.

  In order to dissolve and remove the dissolvable intermediate layer, CVD-SiC is immersed in a tank containing the chemical solution (hereinafter also referred to as a chemical solution tank), but the chemical solution tank is agitated to shorten the immersion time. It is preferable to warm the chemical solution.

  In this production, a method for forming CVD-SiC as a product on the surface of the dissolvable intermediate layer is not particularly limited, such as a thermal CVD method, a plasma CVD method, and a photo CVD method. The thermal CVD method is preferable because the film formation rate can be increased and a thick film can be formed in a short time.

For example, silicon-containing compounds such as SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₃ Cl, and SiH ₄ and carbon such as CH ₄ , CH ₂ H ₆ , and C ₃ H _{8 at} a high temperature of 1000 ° C. or higher and reduced pressure Examples include a method of reacting a compound, or thermal decomposition of CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiCl ₂ , (CH ₃ ) ₃ SiCl, (CH ₃ ) ₄ SiCl, etc. containing carbon and silicon simultaneously. It is done.

  The film thickness of the CVD-SiC is preferably 50 to 5000 μm. If the film thickness of CVD-SiC is less than 50 μm, the strength of CVD-SiC is insufficient and the risk of breakage is increased, which is not preferable. On the other hand, if the film thickness of CVD-SiC exceeds 5000 μm, there is a risk that cracks may occur in the CVD-SiC due to the difference in thermal expansion coefficient between the CVD-SiC and the dissolvable intermediate layer. The film thickness of CVD-SiC is preferably 200 to 3000 μm, and the film thickness of CVD-SiC is particularly preferably 500 to 2000 μm.

  Hereinafter, this manufacturing method will be described with reference to FIG. FIG. 1 shows an embodiment of the production method as a series of flows. In the figure, 1 indicates a substrate, 2 indicates a dissolvable intermediate layer, 3 indicates a desired CVD-SiC, and so on. In addition, this manufacturing method is limited to FIG. 1, and is not interpreted.

  FIG. 1A shows a cross-sectional view of a base material when a dissolvable intermediate layer 2 is formed on the surface of the base material 1. Next, a cross-sectional view when CVD-SiC3 is formed on the dissolvable intermediate layer 2 by the CVD method is shown in FIG. Next, in order to separate the desired CVD-SiC3 from the substrate 1, a part of the CVD-SiC3 (right end portion) of (b) is removed by machining such as grinding or cutting to expose the dissolvable intermediate layer. A cross-sectional view of the case is shown in (c). Next, although not shown in the drawing, the desired CVD-SiC3 obtained is obtained after the whole is immersed in a bath of a chemical solution capable of dissolving the dissolvable intermediate layer such as hydrofluoric acid, the dissolvable intermediate layer 2 is removed and the base material 1 is recovered. (D) shows a cross-sectional view of.

[Example 1]
An example in which a straight tube of CVD-SiC with one end closed according to the method described in FIG. 1 will be described. As the substrate, φ4 × 1000 mm columnar CVD-SiC was used. An a-Si film having a thickness of 100 μm was formed on the surface of the substrate by plasma CVD. As the conditions for the plasma CVD method, SiH ₄ was used as a source gas, high frequency power of 13.56 MHz was applied, and the substrate was heated to 300 ° C. to form a film.

Further, a CVD-SiC film having a thickness of 1000 μm was formed on the surface by a thermal CVD method. As the conditions for the thermal CVD method, a film was formed at 1300 ° C. using CH ₃ SiCl ₃ as a source gas. One end of the obtained CVD-SiC was removed by machining to expose the a-Si film, and a hydrofluoric acid chemical bath (hydrofluoric acid having a concentration of 50 mass%: hydrofluoric acid nitric acid having a concentration of 70 mass% was massed) Mixed at a ratio of 1: 4) for one day.

  As a result, a CVD-SiC tubular body having one end with an outer diameter of φ6.2 and an inner diameter of φ4.2 × 1000 mm was obtained. When the appearance of the obtained tubular body was inspected, no cracks or cracks were observed. Moreover, in order to measure the impurity concentration of the obtained tubular body, it analyzed by GDMS (glow discharge mass spectrometry) method. As a result of analyzing impurities, the concentration of Al was 0.01 ppm, and the concentration of other metal elements was 0.01 ppm or less. Furthermore, after recovering the used φ4 × 1000 mm CVD-SiC substrate and inspecting its appearance, it was confirmed that it was reusable without deformation and defects.

[Example 2]
In Example 1, it was carried out similarly to Example 1 except having used the CVD-SiC base material used in Example 1 again as a base material. As for the appearance of the obtained tubular body, as in Example 1, no cracks or cracks were observed. As a result of analyzing impurities by the GDMS method, the concentration of Al was 0.01 ppm, and the concentration of other metal elements was 0.01 ppm or less. Furthermore, when the collected CVD-SiC base material was externally inspected, it was in a reusable state without deformation or defects.

[Example 3 (comparative example)]
In Example 1, a φ4 × 1000 mm cylindrical high purity (purity 99.9 mass%) alumina sintered body base material was used, and an a-Si film was not formed. The procedure was the same as Example 1 except that the immersion was not performed. After the film formation, the alumina sintered body as the base material was separated from the CVD-SiC, but when the appearance was inspected, cracks were observed in both the obtained tubular body and the base material. Moreover, when the impurity concentration of the tubular body obtained by the GDMS method was measured, Al was 300 ppm, Fe was 50 ppm, Cu was 5 ppm, and otherwise, it was 0.01 ppm or less.

[Example 4 (comparative example)]
In Example 1, as a base material, a φ4 × 1000 mm graphite base material was used. Instead of forming an a-Si film and not immersing in a hydrofluoric acid chemical bath, the graphite base material was burned at 1200 ° C. in the atmosphere. In the same manner as in Example 1 except that the heat treatment was performed for 2 months. When the obtained CVD-SiC tubular body was observed, cracks were observed in its appearance, and it was confirmed that a part of the graphite base material remained without being burned out. The concentration of impurities in the tubular body obtained by the GDMS method was 0.01 ppm for Al, and 0.01 ppm or less for the others.

[Example 5 (comparative example)]
In Example 1, a cylindrical tungsten substrate having a diameter of 4 × 1000 mm was used as the substrate, and the same procedure as in Example 1 was performed except that an a-Si film was not formed and the film was not immersed in a hydrofluoric acid chemical bath. When the obtained CVD-SiC tubular body was observed, cracks were observed in its appearance. In addition, the tungsten base material did not remain inside the obtained tubular body, and was completely dissolved and removed with a hydrofluoric acid chemical solution. Moreover, when the impurity concentration of the tubular body obtained by the GDMS method was measured, Al was 0.01 ppm, and otherwise, it was 0.01 ppm or less.

  By this production method, CVD-SiC can be easily produced at a level free from defects such as cracks and cracks and with no problem in impurity concentration. Therefore, a CVD-SiC jig suitable for a semiconductor manufacturing apparatus can be provided.

  With this manufacturing method, even if the graphite substrate is difficult to burn out, for example, a shape that is longer than the outer diameter (long shape), CVD-SiC has no defects such as cracks and cracks, and the impurity concentration is a problem. It can be manufactured with high productivity at a level without any problems. Therefore, it can be manufactured with high productivity of a CVD-SiC jig for a semiconductor manufacturing apparatus having a long shape such as a thermocouple protection tube and a gas introduction tube.

The figure which shows the flow of one embodiment of this manufacturing method. (A) Sectional drawing after forming a meltable intermediate | middle layer on the surface of a base material. (B) Sectional drawing after forming SiC by CVD method on the meltable intermediate | middle layer formed by (a). (C) Sectional drawing after deleting a part of CVD-SiC formed in (b) in order to remove a dissolvable intermediate | middle layer with a chemical | medical solution. (D) Cross-sectional view of CVD-SiC after CVD-SiC from which a part has been deleted in (c) is immersed in a chemical solution to remove the dissolvable intermediate layer and recover the substrate.

Explanation of symbols

1: Base material 2: Dissolvable intermediate layer 3: CVD-SiC

Claims (7)

  After forming an intermediate layer that can be dissolved with a chemical solution on a substrate, a silicon carbide film is formed on the surface of the intermediate layer by a CVD method to form a silicon carbide body, and then the intermediate layer is dissolved and removed with a chemical solution. A method for producing a silicon carbide member, comprising separating the silicon carbide body from the substrate.   The method for producing a silicon carbide member according to claim 1, wherein the base material is graphite or SiC.   The method for producing a silicon carbide member according to claim 1, wherein the intermediate layer is a Si-based film.   4. The method for manufacturing a silicon carbide member according to claim 3, wherein the Si-based film is an amorphous Si film or a poly-Si film.   The method for producing a silicon carbide member according to claim 1, wherein the chemical solution is an acid or an alkali.   The method for producing a silicon carbide member according to claim 1, wherein the intermediate layer has a thickness of 1 to 1000 μm. The method for producing a silicon carbide member according to claim 1, wherein the silicon carbide body has a thickness of 50 to 5000 μm.

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