JP2000169298A - Silicon carbide molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a SiC molded article low in light transmission and suitably used as one of various kinds of heat-resistant members including various members for producing semiconductors, such as shielding members and dummy wafers. SOLUTION: This SiC molded article comprises as a matrix a CVD-SiC molded article which is produced by CVD(chemical vapor deposition) method and has a crystal property that the strength ratio of diffraction peaks on the crystal surfaces (111), (200), (220) and (311) by a X-ray diffraction method is 100:45 to 55:15 to 25:35 to 45, and at least one CVD-SiC layer which is formed on or in the matrix and has a crystal property that the strength ratio of diffraction peaks on the crystal surfaces (111), (200), (220) and (311) by a X-ray diffraction method is 100:1 to 10:1 to 5:1 to 6. The thickness of the CVD-SiC layer is 10-50% based on that of the CVD-SiC molded article.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various heat-resistant members such as shields for heat treatment equipment of semiconductor manufacturing equipment, heat equalizing rings, etc. Also, the present invention relates to a SiC molded body that can be suitably used as various members such as a dummy wafer and a susceptor used in a diffusion furnace device, an etching device, a CVD device, and the like of a semiconductor manufacturing device.

[0002]

2. Description of the Related Art SiC has excellent material properties such as heat resistance, corrosion resistance and strength properties, and is useful as various industrial members. In particular, a SiC molded body (CVD-SiC molded body) manufactured using a CVD method (chemical vapor deposition method).
Because of its high density and high purity, it is suitably used in various application fields requiring high purity, including various members for semiconductor production. The SiC molded body by the CVD method causes a gas phase reaction of the raw material gas to precipitate crystal grains of SiC on the substrate surface,
It is produced by forming a film by growing crystal grains and then removing the substrate, and is characterized by a dense material, high purity, and high tissue homogeneity.

[0003] It is known that the higher the purity of this CVD-SiC molded body, the higher the light transmittance thereof. It can be a problem. For example, rapid thermal annealing (ra
pid thermal annealing), rapid thermal cleaning (rapidt)
hermal cleaning), rapid thermal chemical vapor deposition (rapid therm)
al chemical vapor deposition), rapid thermal oxidation (rapid th
ermal oxidation, rapid thermalnitrida
), etc. (referred to as RTP).

[0004] In this RTP, accurate temperature control of the wafer substrate is required. However, when measuring the temperature with a pyrometer, the wafer substrate is removed when a black body cavity is formed on the surface opposite to the processing surface of the wafer substrate. If light from the supporting member is transmitted, there is a problem that disturbance light is generated and accurate temperature control becomes difficult. For this reason, in Japanese Patent Application Laid-Open No. Hei 6-341905, in order to prevent light leaking from the heating element from entering the reflection cavity, a guard ring for supporting the partition wall and the wafer is arranged along the wafer, and the heating element is prevented from coming out of the heating element. It has been proposed that this guard ring be made of silicon, which has a black or gray color that absorbs leaked light. Japanese Patent Application Laid-Open No. 8-255800 discloses that a support ring for supporting a wafer substrate is made of silicon or silicon oxide. It has been proposed that the cylinder holding the support ring be made of quartz coated with silicon so as to be opaque in the frequency range of the pyrometer.

[0005] However, those coated with silicon or silicon disclosed in JP-A-6-341905 and JP-A-8-255800 are inferior in corrosion resistance to acid washing for repeated use. However, there is a problem that the light opacity is reduced due to a gradual decrease in the thickness of the film.

Further, a dummy wafer used for stabilizing the etching condition of the wafer in the plasma etching process and a dummy wafer used for stabilizing the condition of the wafer in the CVD process are required to have low light transmittance. In other words, the wafer is mounted on the support boat by the transfer robot, but the recognition of the wafer is performed by irradiating the laser beam, so if the light transmittance of the wafer is high, the robot can accurately recognize the position of the wafer. Therefore, there is a problem that it is difficult to mount a wafer at a predetermined position in the reaction apparatus.

[0007]

As a result of a study on the relationship between the properties of the CVD-SiC compact and the optical characteristics in order to eliminate the above-mentioned problems, the applicant of the present invention has obtained a CVD-SiC compact having a low light transmittance. -SiC obtained by CVD method
A molded body having at least one SiC layer having different particle properties on its surface or inside, and having a thickness of 300 to 2500 nm.
A SiC molded body (Japanese Patent Application No. 10-42906) or a CVD method, wherein the light transmittance in the wavelength region of 0.4% or less and the light transmittance in the wavelength region exceeding 2500 nm is 2.5% or less.
A CVD-SiC compact comprising a β-type crystal obtained by the method, and having a thickness of 2 to 20 μm on its surface or inside.
Wherein at least one visible light-impermeable CVD-SiC layer is formed and the light transmittance in the wavelength range of 300 to 2500 nm is 0.4% or less (Japanese Patent Application No. 10-294959). No.) was developed and proposed.

The above invention is based on the finding that the presence of a layer that scatters and reflects light as a material structure of a CVD-SiC molded body can reduce the light transmittance. As a result of further research based on the above, it has been found that the formation of disorder in the crystal structure in the CVD-SiC molded body can effectively reduce the light transmittance. The present invention has been developed on the basis of this finding, and its object is to excel in light opacity, for example, various heat-resistant members such as heat treatment equipment shields for semiconductor manufacturing equipment, heat equalizing rings, and semiconductor manufacturing equipment. An object of the present invention is to provide a SiC molded body that can be suitably used as various members such as a dummy wafer and a susceptor used in a diffusion furnace device, an etching device, a CVD device, and the like of a device.

[0009]

In order to achieve the above object, a SiC molded body according to the present invention is produced by a CVD method, and has a X (X) of the (200), (220) and (311) planes with respect to the crystal plane (111). The intensity ratio of diffraction peaks by line diffraction is 100: 45 to 5
CVD with crystal properties of 5:15 to 25:35 to 45
-Using a SiC molded body as a base material, the intensity ratio of diffraction peaks by X-ray diffraction of (200), (220), and (311) planes with respect to the crystal plane (111) is 100: 1 to 10: 1
-5: At least one CVD-SiC layer having a crystalline property of 1-6 is formed, and the thickness of the CVD-SiC layer is 10-50% of the thickness of the CVD-SiC molded body. Features above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
SiC is deposited on the substrate surface by the method
The base material is a CVD-SiC molded body produced by removing the base material after forming a film of the base material, and the surface or inside of the base material has different crystal properties from the base material, that is, the crystal structure is disordered. It has a texture of at least one CVD-SiC layer.

The formation of the SiC film by the CVD method includes Si atoms and C atoms in one molecule, for example, CH ₃ SiCl
₃ , a method in which a halogenated organosilicon compound such as (CH ₃ ) ₃ SiCl or CH ₃ SiHCl _{2 is} heated together with a carrier gas such as hydrogen gas to undergo reductive pyrolysis, or
It is carried out by precipitating SiC on the surface of the base material by a method in which a silicon compound such as iCl ₄ and a carbon compound such as CH ₄ are heated and reacted.

In the process of forming a SiC film on the surface of a base material, the raw material gas precipitates SiC by a gas phase reaction to generate nuclei of SiC on the surface of the base material, and the SiC nuclei grow to form amorphous SiC. To finer polycrystalline SiC
The SiC film is formed by continuously growing into a columnar crystal structure through the grains. Therefore, CVD-Si
Properties such as the strength characteristics, thermal characteristics, and optical characteristics of the C-formed body differ depending on the crystal properties of the SiC coating formed by deposition on the substrate surface.

For example, in the structure of a CVD-SiC compact, layers having different crystal structures, that is, SiC having a disordered crystal structure,
When the layer is present, the light characteristics change at the interface where the crystal structure changes, and complicated phenomena such as refraction, scattering, and reflection of light occur, and a part of the light is confined. Light opacity is increased.

The SiC molded body of the present invention has a CV
The crystal structure of the D-SiC compact was determined by the X-ray diffraction
The intensity ratio of the diffraction peaks of the (200), (220) and (311) planes with respect to (11) is 100: 45 to 55:15 to 25:35 to 45.
(200), (22) with respect to the crystal plane (111) by X-ray diffraction as CVD-SiC layers having different crystal structures.
0), the intensity ratio of the diffraction peaks on the (311) plane is 100: 1 to 1
By specifying the crystal properties of 0: 1 to 5: 1 to 6, light transmittance is reduced, that is, light impermeability is increased. The diffraction peak value obtained by X-ray diffraction is Cu
Is the value measured at Kα.

The light transmittance can be reduced by forming at least one layer of the CVD-SiC layer having different crystal properties on the surface or inside of the base material.
It is preferable to form the -SiC layer by dispersing it into two or three layers because the light transmittance can be further reduced. The thickness of the formed CVD-SiC layer is set in a range of 10 to 50% of the thickness of the SiC molded body. When the thickness of the CVD-SiC layer is in the range of 10 to 50%, refraction and scattering of light,
Since light characteristics such as reflection change more effectively, light transmittance can be reduced.

The SiC molded body has a CV on the removable substrate surface.
It is produced by depositing a SiC film by depositing SiC by a D reaction and then removing the base material. As the removable substrate, carbon-based materials, metal-based materials such as silicon, quartz, etc. are used, but the workability is good,
A carbon-based material, particularly a graphite material, which can be easily burned off by heat treatment in air, is suitably used. The graphite material preferably has a high purity with as little impurities as possible. Si
After forming the C film, the substrate can be removed by cutting, polishing, burning in air, or a combination of these methods.

In the CVD reaction, for example, a graphite substrate is placed in a reaction furnace.
Set, exhaust the air in the system, and then heat it to the specified
Temperature, and then feed in hydrogen gas to
After replacing the atmosphere, hydrogen gas is used as a carrier gas and C
H_ThreeSiCl_Three, (CH_Three) _ThreeSiCl, CH_ThreeSiH
Cl_TwoUsing halogenated organosilicon compounds such as
To reduce and thermally decompose, or SiCl_Four
And silicon compounds such as CH_FourAnd carbon compounds such as
Si on the graphite substrate surface
A C film is deposited. Graphite after forming SiC coating
CVD-SiC formation as base material by removing base material
A feature is created.

In the process of forming the SiC film,
CVD reaction conditions, for example, a mixture ratio of a halogenated organosilicon compound and hydrogen gas, or a silicon compound and a carbon compound,
At least one CVD-SiC layer having a different crystallinity is formed in the surface layer or inside of the base material by setting and controlling the feed amount, the reaction temperature, the reaction time, the pressure in the reaction furnace and the like to appropriate values.
Layers can be formed. For example, a CV for producing a base material
After reacting for a predetermined time under the D reaction condition,
After the formation of the iC film, the CVD reaction conditions are changed and the CVD reaction is performed for a predetermined time to obtain a C layer having a different crystalline property.
After forming a VD-SiC layer, and then returning to the CVD reaction conditions at the time of preparing the base material, forming a SiC coating for a predetermined time,
By removing the base material, a CVD-SiC molded body in which one CVD-SiC layer having different crystal properties is formed inside the base material can be obtained.

[0019]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Example 1 A high-purity isotropic graphite material having a diameter of 202 mm and a thickness of 6 mm (ash content: 1
The graphite substrate was set in a chamber of a CVD reactor and heated. After purging the chamber with hydrogen gas, CH ₃ SiCl ₃ as the raw material gas, a hydrogen gas as a carrier gas, CH ₃ Si in the mixed gas
The concentration of Cl ₃ was set to 7.5 vol%, and the mixture was fed into the chamber at a flow rate of 190 l / min.
Time, then 2 hours at a temperature of 1300 ° C., again 1400
Perform CVD reaction at a temperature of 14 ° C. for 14 hours to apply S
An iC coating was applied. Next, after cutting in the transverse direction, the graphite base material was burned and removed by heating in air, and the surface was further polished to produce a SiC molded body having a diameter of 200 mm and a thickness of 0.5 mm. Thus, a CVD-SiC molded body in which one CVD-SiC layer having different crystal properties was formed inside was produced.

Examples 2 to 8 and Comparative Examples 4 to 5 The reaction temperature and time of the CVD reaction were changed except for the setting.
A SiC molded body was produced in the same manner as in Example 1.

Comparative Examples 1 to 3 SiC compacts were produced in the same manner as in Example 1 except that the reaction temperature of the CVD reaction was fixed and the reaction time was changed.

The C of the SiC molded body thus produced is
Table 1 compares the VD reaction conditions. Using a Shimadzu self-recording spectrophotometer, wavelengths of 0.5, 2 and 10 μm
Of the crystal planes (111), (200), (220), and (311) were measured by X-ray diffraction. In addition, X of the CVD-SiC layer formed inside
The line diffraction was measured by polishing the surface to expose the inner CVD-SiC layer. Table 2 shows the obtained results.

[0024]

[Table 1]

[0025]

[Table 2] (Note) * 1 Relative intensity of diffraction peaks by X-ray diffraction of crystal planes (200), (220), and (311) with respect to crystal plane (111)

From the results in Tables 1 and 2, the reaction temperature was 1400 ° C.
In Example 1, in which one CVD-SiC layer formed at a reaction temperature of 1300 ° C. was formed at the center of the base material of the CVD-SiC molded body formed in the above, and the thickness was 20% of the CVD-SiC molded body. The light transmittance shows a low value of 0.3% or less, and C
It can be seen that in Example 2 where the thickness of the VD-SiC layer was 50%, the light transmittance was further reduced. In addition, CVD-SiC
In Examples 3 and 4 in which the difference between the reaction temperature for forming the layer is 1350 ° C. and 1400 ° C. which is the temperature for forming the CVD-SiC molded body, the disorder of the crystal structure is slightly reduced. Therefore, the tendency for the decrease in light transmittance to decrease is recognized. In Examples 5 to 8 in which two CVD-SiC layers were formed, it was recognized that the light transmittance was further reduced. On the other hand, in Comparative Examples 1 to 3 in which the CVD-SiC layer was not formed, no decrease in the light transmittance was observed.
-It turns out that the light transmittance cannot be sufficiently reduced in Comparative Examples 4 and 5 in which the thickness of the SiC layer is small.

[0027]

As described above, according to the SiC molded article of the present invention, a CV having a specific crystallinity in which the crystal structure is disturbed on the surface or inside of the CVD-SiC molded article as the base material.
By forming at least one D-SiC layer and specifying its thickness, the light transmittance can be effectively reduced. Therefore, it is excellent in light opacity, and can be suitably used as various heat-resistant members for a heat treatment apparatus including various members for semiconductor production such as a shield and a dummy wafer.

Claims (1)

[Claims] 1. The method according to claim 1, wherein the crystal face (111) is produced by a CVD method.
The intensity ratio of the diffraction peaks of the (200), (220), and (311) planes by X-ray diffraction with respect to 100: 45 to 55:15 to 25:
A diffraction peak by X-ray diffraction of the (200), (220), and (311) planes with respect to the crystal plane (111) on the surface or inside of the base material is a CVD-SiC molded body having crystal properties of 35 to 45. At least one CVD-SiC layer having a crystallinity of 100: 1 to 10: 1 to 5: 1 to 6 is formed, and the CVD-SiC layer has a thickness of CVD-SiC.
S having a thickness of 10 to 50% of the thickness of the molded body
iC molded body.