JP4404703B2 - Light-impermeable SiC molded body and method for producing the same - Google Patents

Description

  The present invention has high purity, excellent heat resistance and strength characteristics, and particularly high light impermeability. For example, a heat treatment device shield for a semiconductor manufacturing apparatus, various heat resistant members such as a soaking ring, or a semiconductor manufacturing apparatus. The present invention relates to a light-impermeable SiC molded body that can be suitably used as various members such as a dummy wafer and a susceptor used in a diffusion furnace apparatus, an etching apparatus, a CVD apparatus, and the like, and a method for manufacturing the same.

  SiC is excellent in material properties such as heat resistance, corrosion resistance and strength properties, and is useful as various industrial members. In particular, an SiC molded body (CVD-SiC molded body) produced by using a CVD method (chemical vapor deposition method) is dense and highly pure, so high purity is required including various members for semiconductor manufacturing. It is suitably used in certain application fields.

  This CVD-SiC molded body is obtained by causing a raw material gas to undergo a gas phase reaction to deposit SiC crystal grains on the surface of the base material, forming a film by growing the crystal grains, and then removing the base material. It is known that the material is dense, high purity, and the homogeneity of the structure is high. Generally, the higher the purity, the higher the light transmittance.

  Thus, since the SiC molded body by CVD method has high purity and high light transmittance, when used as various members such as a semiconductor manufacturing apparatus and a heat treatment apparatus, the physical properties of SiC become a problem depending on the application field. Sometimes. For example, a semiconductor manufacturing process includes a rapid thermal process called a rapid thermal process (RTP), and in Patent Document 1, a wafer substrate is used as a shield so that it exhibits excellent in-plane uniformity even by high-speed heating. It has been proposed to be composed of SiC, and a material property that is opaque to radiant heat is required.

  In addition, this RTP requires precise temperature control of the wafer substrate, but when measuring with a pyrometer, the wafer substrate is supported when forming a black body cavity on the surface opposite to the processing surface of the wafer substrate. If there is light transmission through a member or the like, there is a problem that it becomes disturbance light and accurate temperature management becomes difficult. Therefore, Patent Document 2 proposes that the support ring for supporting the wafer substrate is made of silicon or silicon oxide, and the cylinder for holding the support ring is made of quartz coated with silicon so as to be opaque in the range of the pyrometer frequency. ing.

  Further, a dummy wafer used for stabilizing the etching conditions of the wafer in the plasma etching process and a dummy wafer used for stabilizing the conditions of the wafer in the CVD process are required to have low light transmittance. Wafers are mounted on a support boat by a transfer robot. However, since wafer recognition is performed by irradiating laser light, the robot can accurately recognize the position of the wafer if the wafer is highly transparent. Therefore, it becomes difficult to mount the wafer at a predetermined position in the reaction apparatus. Further, since the dummy wafer is irradiated with light and the reflected light is detected to detect the state of particle adhesion to the wafer, it is necessary to obtain sufficient reflected light without transmitting light.

  Therefore, in Patent Document 3, each of the metal elements contained is a CVD-SiC plate having a high purity of 0.3 ppm or less and a thickness of 0.1 to 1 mm, and an infrared ray having a wavelength of 2.5 to 20 μm. A high-purity CVD-SiC semiconductor heat-treating member having a maximum infrared transmittance of 5% or less in the region has been proposed. Further, Patent Document 4 proposes a multilayer SiC wafer formed by laminating a plurality of SiC layers by a CVD method, and laminating a plurality of SiC layers having different light transmittances, and having a small light transmittance. It is disclosed that a SiC layer having a high light transmittance is disposed on both sides of the SiC layer.

  Further, the present applicant is also a CVD-SiC molded body obtained by the CVD method as a SiC molded body having excellent light impermeability, and has at least one SiC layer having different particle properties on the surface or inside thereof. A SiC molded article having a light transmittance in a wavelength region of 300 to 2500 nm of 0.4% or less and a light transmittance of 2.5% or less in a wavelength region exceeding 2500 nm and a method for producing the same (Patent Document) 5) was proposed.

Further, the present applicant is a CVD-SiC molded body made of a β-type crystal obtained by a CVD method, and has at least one visible light-impermeable CVD-SiC layer having a thickness of 2 to 20 μm on the surface or inside thereof. As a result, an SiC molded body characterized in that the light transmittance in a wavelength region of 300 to 2500 nm is 0.4% or less and a manufacturing method thereof (Patent Document 6) have been developed and proposed.
JP 09-237789 A JP 08-255800 A JP 10-012563 A JP-A-11-121315 Japanese Patent Laid-Open No. 11-228233 JP 2000-1119064 A

  The inventors have continued research on the development of a low-light-transmitting CVD-SiC molded body, and that there is a layer that scatters and reflects light by controlling the light transmission direction as the material structure of the SiC molded body. It was confirmed that the light transmittance was further reduced.

  That is, the object of the present invention is a light with high purity and excellent heat resistance and strength characteristics that can be suitably used as various members for semiconductor production such as a shield or a dummy wafer, or various heat resistant members for a heat treatment apparatus. An object of the present invention is to provide an impermeable CVD-SiC molded body and a method for producing the same.

  The light-opaque SiC molded body according to the present invention for achieving the above object is a CVD-SiC molded body made of a β-type crystal obtained by a CVD method, and has an average particle diameter of 2 μm or less and a thickness of 15 to 30 μm. Light-impermeable layer 4, intermediate layers 3 and 5 having a thickness of 5 to 15 μm in which the intensity of the X-ray diffraction peak of the SiC (111) plane is oriented to 5000 cps or more on both upper and lower sides thereof, and an average particle diameter of 8 on the outer side thereof A structural feature is that the light transmission layers 2 and 6 have a multilayer structure of ˜30 μm and a thickness of 100 μm or more.

  Moreover, the manufacturing method sets the CVD reaction conditions in the process of forming the SiC film in the manufacturing method of the CVD-SiC molded body in which the SiC base film is removed after forming the SiC film on the graphite base surface by the CVD method. A structural feature is that it includes a SiC film forming process in which the light transmission layer 2, the intermediate layer 3, the light non-transmission layer 4, the intermediate layer 5, and the light transmission layer 6 are sequentially formed.

  Furthermore, as another production method, a CVD-SiC molded body obtained by forming a SiC film having an average particle diameter of 8 to 30 μm and a thickness of 100 μm or more on the surface of the graphite substrate by CVD and removing the graphite substrate is obtained. As the light transmissive layer 2, the CVD reaction conditions are changed in the course of forming a SiC film on the surface of the light transmissive layer 2, and the intermediate layer 3, the light non-transmissive layer 4, the intermediate layer 5, and the light transmissive layer 6 are changed. A structural feature is that an SiC film forming process is sequentially performed.

  According to the light-impermeable SiC molded body of the present invention, the light-transmitting layer 2, the intermediate layer 3, the light-impermeable layer 4, the intermediate layer 5, and the light-transmitting layer 6 are formed in a multilayer structure in order, Consists of SiC compacts that specify the particle properties, orientation degree of (111) crystal plane, and thickness thereof, and in particular, transmits light through an intermediate layer having high orientation degree of SiC (111) crystal face. By controlling mainly in the vertical direction, the reflection of light at the interface between layers can be further increased, so that the light transmittance can be effectively reduced. Furthermore, when this multilayer structure is provided in a plurality of layers, the light transmittance can be further reduced. Moreover, when depositing SiC particles on the substrate surface, the light-impermeable SiC molded article of the present invention can be produced by controlling the CVD reaction conditions.

  Therefore, the present invention provides various heat-resistant members such as shields for heat treatment devices of semiconductor manufacturing devices, soaking rings, or dummy wafers and susceptors used in diffusion furnace devices, etching devices, CVD devices, etc. of semiconductor manufacturing devices. It is highly useful as a light-impermeable SiC molded article suitable as various members and a method for producing the same.

  As shown in the side sectional view illustrated in FIG. 1, the light-impermeable SiC molded body of the present invention has an intermediate layer 3, a light-impermeable layer 4, an intermediate layer 5, and a light-transmitting layer on the light-transmitting layer 2. The layer 6 is formed from a multilayer structure in which the layers 6 are sequentially stacked. In this case, the layer 6 is composed of a five-layer structure.

  Among these layers, the light-impermeable layer 4 is composed of SiC fine particles having an average particle diameter of 2 μm or less. When light is incident on the SiC particle layer, the light is reflected, refracted, scattered, etc. at the surface of the particle and the interface between the particles, and the transmitted light is reduced. Therefore, the smaller the particle diameter, the larger the surface of the particle and the interface between the particles, and the transmitted light decreases. In the present invention, the light-impermeable layer 4 is composed of fine particles having an average particle diameter of 2 μm or less. This is because when the average particle diameter exceeds 2 μm, the light transmittance is not sufficiently lowered. The light opaque layer 4 is formed to a thickness of 15 to 30 μm. If the thickness is less than 15 μm, the effect of light impermeability is not sufficient, and if the layer thickness exceeds 30 μm, the film formation rate is slow, so that productivity is lowered and thermal shock resistance is also lowered.

  On the upper and lower sides of the light-impermeable layer 4, intermediate layers 3 and 5 having a thickness of 5 to 15 μm are formed in which the intensity of the X-ray diffraction peak of the SiC (111) plane is 5000 cps or more. That is, the intermediate layers 3 and 5 are SiC layers in which the crystal plane of SiC (111) is highly developed, and the direction of transmitted light is controlled mainly by the intermediate layer. The light transmitted through the intermediate layer 3 is reflected more at the interface between the light-impermeable layer 4 and the interface between the light-impermeable layer 4 and the intermediate layer 5 made of fine particles having an average particle diameter of 2 μm or less. The light transmittance can be reduced.

  When the intensity of the X-ray diffraction peak is less than 5000 cps, since the degree of orientation of the SiC (111) plane is small and the control of light in the vertical direction is not sufficient, the effect of reducing transmitted light at the interface is also small. The thickness of the intermediate layers 3 and 5 is set to 5 to 15 μm. This is because when the thickness is less than 5 μm, the vertical component of the transmitted light is small so that the reflection of light at the interface with the light-impermeable layer 4 is insufficient. On the other hand, when the thickness exceeds 15 μm, the SiC (111) surface is reached. This is because the orientation is highly oriented, and mechanical strength is reduced and peeling due to thermal shock is likely to occur.

  The intensity of the X-ray diffraction peak was determined by using Cu Kα ray for X-ray, applied voltage: 40 KV, applied current: 20 mA, scanning speed: 4 ° / min, diverging slit; 1 ° incident slit; 1 °, scattering X-ray diffraction is performed under the conditions of slit: 0.3 mm, filter: Ni, and obtained from the diffraction peak value.

  Light transmission layers 2 and 6 having an average particle diameter of 8 to 30 μm and a thickness of 100 μm or more are formed outside the intermediate layers 3 and 5. This light-transmitting layer is formed to maintain the strength of the light-impermeable SiC molded body of the present invention and to maintain the production efficiency. The light-impermeable layer 4 and the intermediate layers 3, 5 and the like are particles thereof. The strength is low due to properties and the like, and the film formation conditions must be set so as to slow down the CVD reaction. Therefore, a SiC film deposited by CVD is sufficiently grown to form a SiC film, and an SiC film having an average particle diameter of 8 to 30 μm is formed to a thickness of 100 μm or more in order to maintain the strength and increase the film formation speed. A multilayer structure is provided in which the light-transmitting layers 2 and 6 are formed.

  Thus, the light-impermeable SiC molded body of the present invention increases the degree of reflection, refraction, and scattering of light by the fine particles by the light-impermeable layer 4 made of fine particles having an average particle diameter of 2 μm or less. Transmitted light can be significantly reduced. Furthermore, the light transmitted through the intermediate layer is mainly intermediate because of the intermediate layers 3 and 5 that are highly oriented with the intensity of the X-ray diffraction peak of the SiC (111) plane formed on the upper and lower sides of the light-impermeable layer 4 being 5000 cps or more. It becomes possible to further reduce the light transmittance by further increasing the degree of reflection, refraction, and scattering of the transmitted light at the interface of the light-impermeable layer 4 as a light component perpendicular to the layer. Become. Furthermore, it can be set as the self-supporting CVD-SiC molded object which has sufficient intensity | strength by the light transmissive layers 2 and 6 formed in average particle diameters 8-30 micrometers and thickness in 100 micrometers or more.

  Furthermore, as shown in FIG. 2, the light impermeability can be further improved by providing the multilayer structure shown in FIG. 1 in a plurality of repeated layers. 2 are the same as those in FIG.

  The light-opaque SiC molded body of the present invention, for example, the light-opaque SiC molded body shown in FIG. 1 is manufactured by applying a SiC film on the graphite substrate surface by CVD as shown in the process diagram of FIG. In the method for producing a CVD-SiC molded body in which the graphite substrate is removed after film formation, the CVD reaction conditions are changed in the course of forming the SiC film, and the light transmitting layer 2, the intermediate layer 3, and the light non-transmitting layer 4 are changed. In addition, the intermediate layer 5 and the light transmission layer 6 can be manufactured by a SiC film forming step for sequentially forming the intermediate layer 5 and the light transmission layer 6.

  In the process diagram of FIG. 3, the light-impermeable SiC molded body shown in FIG. 2 in which the multilayer structure of FIG. 1 is provided in a plurality of layers can be manufactured by repeating the process A.

  Alternatively, as shown in the process diagram of FIG. 4, it is obtained by forming a SiC film on the graphite substrate surface with an average particle diameter of 8 to 30 μm and a thickness of 100 μm or more by CVD, and then removing the graphite substrate. SiC film formation in which the intermediate layer 3, the light non-transparent layer 4, the intermediate layer 5, and the light transmissive layer 6 are sequentially formed by changing the CVD reaction conditions on the base material using the light transmissive layer 2 as a base material It can also be manufactured by applying a process.

  4, the light-impermeable SiC molded body shown in FIG. 2 in which the multilayer structure of FIG. 1 is provided in a plurality of layers can be manufactured by repeating the process B.

  For the formation of the SiC film by the CVD method, for example, a graphite substrate is set in a CVD reactor, the air in the system is evacuated, heated and held at a predetermined temperature, and then hydrogen gas is fed and atmospheric hydrogen gas is supplied. After substituting the atmosphere, hydrogen gas is used as a carrier gas, and halogenated organosilicon compounds such as trichloromethylsilane, trichlorophenylsilane, dichloromethylsilane, dichlorodimethylsilane, etc. are fed as source gases, and SiC is reduced by a reductive pyrolysis reaction A method in which a SiC film is deposited on the graphite substrate surface by vapor deposition, or a raw material gas of a silicon compound such as silicon tetrachloride and a carbon compound such as methane is fed and heated, and SiC is generated by a gas phase reaction. Is vapor-phase deposited to deposit a SiC coating on the graphite substrate surface.

  In the process of forming the SiC film, first, the raw material gas reacts in a gas phase to generate SiC nuclei on the substrate surface, and the SiC nuclei grow to become amorphous SiC, and further fine polycrystalline SiC grains. Then, the SiC film is formed by continuing the growth into a columnar crystal structure. Therefore, properties such as strength properties, thermal properties, and optical properties of the CVD-SiC molded body vary depending on the particle properties of the SiC coating formed by deposition on the substrate surface.

  In the film formation process for forming this SiC film, for example, the generation rate of SiC nuclei is greatly affected by the CVD reaction temperature, the raw material gas concentration, the raw material gas amount, etc., and the growth of SiC nuclei and the grains into the columnar crystal structure Growth is mainly influenced by the reaction temperature. And, the formation of the SiC film composed of fine particles is performed by setting the CVD reaction temperature in a low temperature region, and the formation of the SiC film composed of columnar large particles is performed by setting the CVD reaction temperature in a high temperature region. Can do.

  That is, in the film formation process for forming the SiC film, the light transmission layers 2 and 6, the intermediate layers 3 and 5, and the light non-transmission layer 4 can be formed by changing the CVD reaction conditions.

  For example, the formation of the light transmission layers 2 and 6 having an average particle diameter of 8 to 30 μm and a thickness of 100 μm or more is performed by setting the reaction temperature range to 1350 while keeping the raw material gas concentration, the raw material gas amount, the pressure in the reaction furnace, and the like constant. By setting the temperature to ˜1450 ° C. and reacting for an appropriate time, a SiC film composed of SiC particles having a columnar structure can be formed.

  Further, the intermediate layers 3 and 5 having a thickness of 5 to 15 μm in which the intensity of the X-ray diffraction peak of the SiC (111) plane is oriented to 5000 cps or more are set at a reaction temperature range of 1200 to 1350 ° C. It can be formed by a method of reacting, or a method of reacting for an appropriate time by raising or lowering temperature within this temperature range.

  Further, the light-impermeable layer 4 having an average particle diameter of 2 μm or less and a thickness of 15 to 30 μm is set to a reaction temperature range of 1050 to 1200 ° C. and allowed to react for an appropriate period of time to thereby form columnar crystal particles of fine polycrystalline SiC particles. It can be formed by a method of stopping at the stage of preventing growth.

  Examples of the present invention will be specifically described below.

Example 1
Bulk density 1.8 g / cm ^3, thermal expansion coefficient of 4.3 × 10 ^-6 / K, ash 20 ppm or less isotropic graphite material with a diameter 202 mm, was processed to a thickness of 5mm to prepare a graphite substrate . After setting this graphite substrate in the quartz reaction tube of the CVD reactor and replacing the system with hydrogen gas, using trichloromethylsilane as the source gas and hydrogen gas as the carrier gas, trichloromethylsilane in the mixed gas The concentration was adjusted to 7.5 vol%, and the flow rate of the mixed gas was adjusted to 200 l / min. The CVD reaction temperature was kept at 1400 ° C. and the CVD reaction was carried out for 10 hours to form a 400 μm thick SiC film (light transmission layer 2).

  Next, the temperature in the reaction tube is lowered to 1250 ° C., and a CVD reaction is performed for 0.25 hours to form a SiC film (intermediate layer 3) having a thickness of 5 μm. Thereafter, the temperature in the reaction tube is lowered to 1100 ° C. A CVD reaction was carried out for 2 hours to form a SiC film (light opaque layer 4) having a thickness of 20 μm. Further, the temperature in the reaction tube was raised to 1250 ° C. and a CVD reaction was carried out for 0.25 hours to form a 5 μm thick SiC film (intermediate layer 5), and then the temperature in the reaction tube was raised to 1400 ° C. for 10 hours. A CVD reaction was carried out to form a 400 μm thick SiC film (light transmission layer 6). Next, the graphite base material was burned and removed, and then the surface was smoothed by polishing to produce a SiC molded body having a diameter of 200 mm and having the five-layer structure shown in FIG.

Example 2
In Example 1, all the same methods as in Example 1 except that the SiC reaction time for forming the SiC film to be the intermediate layer 3 and the intermediate layer 5 was 0.5 hour and the SiC film having a thickness of 10 μm was formed. Thus, a SiC molded body having a five-layer structure shown in FIG. 1 was produced.

Comparative Example 1
In Example 1, without forming the SiC film to be the intermediate layer 3 and the intermediate layer 5, that is, after forming the SiC film to be the light transmission layer 2, the SiC to be the light opaque layer 4 thereon A SiC molded body having a three-layer structure was manufactured by the same method as in Example 1 except that the film was formed and then the light transmission layer 6 was formed.

  Table 1 shows the properties of each SiC coating of the SiC molded body made of the SiC coating having the multilayer structure manufactured as described above.

  Next, these SiC molded bodies were subjected to light transmittance, chemical resistance, and thermal shock test by the following methods, and the results are shown in Table 2.

Light transmittance measurement:
The light transmittance was measured using a self-recording spectrophotometer manufactured by Shimadzu Corporation using a metal aluminum plate having a thickness of 5 mm as a standard sample, and calculated according to the following formula.
T = BA
Here, T: Light transmittance of the SiC molded body
A: Light transmittance measured value of metal aluminum plate
B: Light transmittance measured value of SiC molded body

Measurement of chemical resistance:
The SiC molded body was immersed in a mixed solution of hydrofluoric acid having a concentration of 49 wt% and nitric acid having a concentration of 62 wt% for 24 hours at room temperature, then washed with water and dried, and the appearance was visually observed and the rate of weight change was measured. In visual observation, color, deformation, peeling, etc. were observed, and the weight change rate was less than 0.01% with no change.

Thermal shock test:
The SiC molded body was placed in an electric furnace maintained at a temperature of 1200 ° C. in air, and held for 2 minutes from the time when the temperature of the SiC molded body reached 1200 ° C. Thereafter, the SiC molded body was taken out from the electric furnace and naturally cooled to 200 ° C. in the air. This heating and holding operation was repeated, and when repeated up to 300 times, the state of cracks and peeling occurring in the SiC molded body was observed.

1 is a side sectional view of a light-impermeable SiC molded body of the present invention having a multilayer structure in which a light-transmitting layer 2, an intermediate layer 3, a light-impermeable layer 4, an intermediate layer 5, and a light-transmitting layer 6 are sequentially laminated. FIG. 2 is a side sectional view illustrating a light-impermeable SiC molded body of the present invention in which the multilayer structure of FIG. 1 is provided in a plurality of layers. It is process drawing which illustrated the manufacturing method of the light-impermeable SiC molded object of this invention. It is process drawing which illustrated the other manufacturing method of the light-impermeable SiC molded object of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light impervious SiC molded object 2 Light transmissive layer 3 Intermediate layer 4 Light opacity layer 5 Intermediate layer 6 Light transmissive layer

Claims (6)

A CVD-SiC molded body made of β-type crystal obtained by a CVD method, having an average particle diameter of 2 μm or less and a thickness of 15 to 30 μm, a light-impermeable layer 4, and an X-ray diffraction of SiC (111) surfaces on both upper and lower surfaces It consists of a multilayer structure of 5 to 15 μm thick intermediate layers 3 and 5 whose peak intensity is oriented to 5000 cps or more, and light transmission layers 2 and 6 having an average particle diameter of 8 to 30 μm and a thickness of 100 μm or more on the outer side. A light-impermeable SiC molded article characterized by A light-impermeable SiC molded article in which a multilayer structure comprising the light-impermeable layer 4, the intermediate layers 3, 5 and the light-transmissive layers 2 and 6 according to claim 1 is provided in a plurality of layers. In the method of manufacturing a CVD-SiC molded body in which a graphite film is removed after forming a SiC film on the surface of the graphite substrate, the CVD reaction conditions are changed in the process of forming the SiC film, and the light transmission layer 2. The light-impermeable SiC molded body according to claim 1, comprising a SiC film forming step of sequentially forming an intermediate layer 3, a light-impermeable layer 4, an intermediate layer 5, and a light-transmissive layer 6. Production method. The method for producing a light-opaque SiC molded body according to claim 2, wherein the SiC film-forming step according to claim 3 is repeated a plurality of times. A CVD-SiC molded body obtained by forming a SiC film having an average particle diameter of 8 to 30 μm and a thickness of 100 μm or more on the surface of the graphite base material by CVD and removing the graphite base material is used as the light transmission layer 2. A SiC film forming process for sequentially forming the intermediate layer 3, the light non-transparent layer 4, the intermediate layer 5, and the light transmissive layer 6 by changing the CVD reaction conditions in the process of forming the SiC film on the surface of the transmissive layer 2. The method for producing a light-impermeable SiC molded body according to claim 1, wherein: The method for producing a light-impermeable SiC molded article according to claim 2, wherein the SiC film-forming step according to claim 5 is repeated a plurality of times.

Images