JP2018538436A - CVD-SiC film manufacturing method and CVD-SiC film manufactured by the method - Google Patents

Abstract

Disclosed are a dense CVD-SiC film having few pores and a composite material, and a production method for efficiently producing such a CVD-SiC film. A CVD-SiC film manufacturing method using a CVD method in which a source gas is supplied and deposited on a substrate in a CVD furnace, and the CVD method is a photo-CVD method for irradiating a substrate with light. And the film-forming temperature (t [K]) and the total pressure (p [kPa]) satisfy | fill following formula (1), The manufacturing method of the CVD-SiC film | membrane characterized by the above-mentioned. p ≧ −0.04t + 72 (1) [Selection] FIG.

Description

  The present invention relates to a method for producing a CVD-SiC film and a CVD-SiC film produced by the method.

  Since SiC is a material having heat resistance, mechanical strength, and corrosion resistance, it is used in various fields. Examples thereof include a susceptor, a liner tube, a process tube, a wafer boat, and a single crystal pulling device member that are heat treatment members in semiconductor manufacturing.

  In addition, since a CVD-SiC material obtained by forming SiC by a CVD method is dense and has no pores and a high-purity material can be obtained, a composite material coated on a base material such as graphite or SiC, or CVD- The SiC film may be separated from the base material and used alone.

  In Patent Document 1, a SiC coating is firmly attached to the surface of a graphite substrate by a CVD method, and has excellent thermal shock resistance against thermal shock such as rapid heating and rapid cooling, and also has corrosion resistance. An excellent SiC coated graphite member is described. Specifically, as a SiC-coated graphite member suitably used as a heat treatment member in semiconductor manufacturing, etc., a graphite member having a graphite substrate surface coated with a SiC film deposited by a CVD method. It has a porosity of 0.4 to 3 μm and a maximum pore size of 10 to 100 μm, and the occupancy ratio of SiC in the surface layer portion of the graphite substrate 150 μm deep from the surface of the graphite substrate is 15 to 50%. This is a SiC-coated graphite member having an average crystal grain size of 1 to 3 μm.

  In Patent Document 1, the crystallinity of the SiC film has a strong orientation to the SiC (111) plane, and the intensity of the diffraction peak of the SiC (111) plane by X-ray diffraction is the intensity of the entire crystal plane SiC (hkl). It is described that it is preferably highly oriented to 80% or more, and it is described that excellent corrosion resistance is imparted by the SiC film highly oriented on the SiC (111) plane.

Japanese Patent Laid-Open No. 2002-3285

  However, since the above described invention has an average crystal grain size of 1 to 3 μm and crystals oriented in directions other than 111 coexist, it is easy to form gaps between the crystal grains and easily form pores. It is difficult to obtain a highly dense CVD film.

  Further, a CVD-SiC film oriented in the 111 direction is a film obtained at a low film-forming temperature. However, when the film-forming temperature is low, a sufficient decomposition rate cannot be obtained, and it is long for obtaining a thick CVD-SiC film. It takes time and it is difficult to obtain a CVD-SiC film efficiently.

  An object of the present invention is to provide a dense CVD-SiC film having few pores and a composite material, and a manufacturing method for efficiently producing such a CVD-SiC film.

The method for producing the CVD-SiC film of the present invention is as follows.
(1) A method for producing a CVD-SiC film by a photo-CVD method that deposits on a substrate in a CVD furnace while supplying a source gas,
In the photo-CVD method, the film forming temperature (t [K]) and the total pressure (p [kPa]) satisfy the following formula (1).

  According to the method for producing a CVD-SiC film of the present invention, since the film is formed at a high pressure satisfying the formula (1), the source gas is efficiently supplied to the substrate, and the CVD-SiC film is formed at a high film-forming speed. Can be formed. In addition, since the film is formed by the photo-CVD method in which light is irradiated while heating the substrate at a predetermined film-forming temperature, the source gas can be easily decomposed in the vicinity of the substrate by the interaction between heat and light. it can. For this reason, the deposition of SiC in the air is prevented by suppressing decomposition of the raw material gas in the air, and the CVD-SiC film having a dense and aligned crystal direction is efficiently produced by the decomposition of the raw material gas on the surface of the substrate. It can be obtained at a high film forming speed.

(2) The total pressure p is 6 to 10 kPa.

  When the total pressure in the CVD furnace at the time of film formation is 6 kPa or more, the source gas can be sufficiently supplied to the substrate, so that a dense CVD-SiC film with a uniform crystal orientation can be efficiently formed. it can. Further, if the total pressure in the CVD furnace at the time of film formation is 10 kPa or less, the absorption of the light beam by the source gas can be suppressed, so that the decomposition of the source gas until the light beam reaches the substrate is suppressed. Decomposition of the raw material gas can be suppressed, and a dense CVD-SiC film having a uniform crystal direction can be obtained efficiently at a high film formation rate.

(3) The film forming temperature t is 1600 to 1700K.

  When the film forming temperature t is 1600K or more, the energy of light necessary for film formation can be reduced. For this reason, decomposition | disassembly of raw material gas can be suppressed in the optical path before reaching the surface of a base material, and a raw material can be decomposed | disassembled efficiently on the surface of a base material. Further, when the film forming temperature is 1700 K or less, the CVD-SiC film cannot be sufficiently formed only by the action of thermal CVD, and the formation of the CVD-SiC film on the surface of the substrate in combination with the action of light rays. Can be promoted. For this reason, by suppressing the decomposition of the source gas in the air, disordered deposition of SiC can be prevented and the formation of a CVD-SiC film on the surface of the substrate can be promoted. Further, a CVD-SiC film can be obtained efficiently and at a high film forming speed.

(4) The light beam has a wavelength of 1500 nm or less.

  If the wavelength of the light beam is 1500 nm or less, the source gas is decomposed and has sufficient photon energy to obtain a CVD-SiC film. Therefore, a dense CVD-SiC film with uniform crystal grains can be efficiently produced. It can be obtained at a high film forming speed.

(5) The CVD-SiC film of the present invention is manufactured by the above manufacturing method.

  Since the CVD-SiC film of the present invention is manufactured by the above-described manufacturing method, a dense CVD-SiC film with uniform crystal particles can be obtained efficiently at a high film-forming speed.

The CVD-SiC film of the present invention for solving the above problems is
(6) It extends in the direction of the film thickness, and the upper end portion includes crystal grains having regular hexagonal pyramids, and F ₁₁₁ in the film thickness direction (Lotting Factor in the 111 direction) is 0.8 to 1.0.

  In the CVD-SiC film of the present invention, crystal grains are formed that extend in the direction of the film thickness and whose upper end has a regular hexagonal pyramid shape. That is, the crystal grains extend in a direction perpendicular to the surface of the base material on which the CVD-SiC film is grown (a plane perpendicular to the thickness direction of the CVD-SiC film), and a large number of crystal grains are arranged. . Therefore, the gap between the crystal particles can be reduced without the crystal particles being randomly stacked. For this reason, a dense CVD-SiC film with few pores can be obtained.

  The upper end portion of the crystal particle has a regular hexagonal pyramid shape. The regular hexagon overlaps with the original figure every time it is rotated by 60 °, and three times the inner angle becomes 360 °, so that the columnar crystal grains can be arranged so as to reduce the gap between them. For this reason, it is considered that crystal grains with disordered crystal directions are not easily formed in the gaps, and a dense CVD-SiC film with few gaps can be obtained.

  In addition, since the upper end of the crystal particle has a regular hexagonal pyramid shape and the tip is sharp, there is no flat surface for reflecting light toward the front. That is, since the surface of the CVD-SiC film is constituted only by the slope, the incident light is scattered, and the regular reflectance can be made less affected by the ratio of the flat surface to the slope. For this reason, the influence which it has on reflection by the way of growth of crystal grains can be reduced.

  Lottering factor is an index for judging the degree of orientation of crystals obtained by X-ray diffraction by eliminating the influence of the half width of the peak. In the case of a fully oriented sample, the numerical value is 1, which is randomly oriented. In the case of a sample, it is 0.

In the CVD-SiC film of the present invention, F ₁₁₁ in the film thickness direction of the CVD-SiC film is 0.8 to 1.0. Since the CVD-SiC film is strongly oriented in the 111 direction ([111] direction perpendicular to the 111 plane) with respect to the film thickness direction (direction perpendicular to the surface of the substrate), there is little disorder in the arrangement of crystal grains. A denser CVD-SiC film with fewer pores can be obtained.

  Furthermore, the CVD-SiC film of the present invention is preferably in the following manner.

(7) wherein _{F 111} is 0.9 to 1.00.

According to the CVD-SiC film of the present invention, F ₁₁₁ in the film thickness direction is 0.9 to 1.0. Since this is a CVD-SiC film in which the 111 direction is more strongly oriented with respect to the film thickness direction, it is possible to obtain a CVD-SiC film with less disorder in the arrangement of crystal grains, and more dense and less pores.

(8) The maximum value of the diameter of the crystal particles is 50 to 300 μm.

  The maximum value of the diameter of the crystal particle is the diameter of the largest crystal particle among the many scattered crystal particles.

  In general, in a CVD-SiC film, crystal grains gradually grow from the start to the end of film formation in a CVD furnace. The size of the crystal particles is the largest that has grown continuously from the start to the end of film formation, the one that stopped growing in the middle of film formation, the one that started growth from the middle of film formation, It becomes smaller than that. For this reason, the largest crystal particle observed on the surface of the CVD-SiC film has grown from the start of film formation, and in the distribution of the diameter of the crystal particle, crystal particles of almost the same size are “large” “Small crystal particles” that form a group of “crystal particles” and that start growing in the middle of film formation fill the gap. For this reason, specifically large crystal grains do not exist. In addition, since a large number of crystal grains grow at the start of film formation, they grow into “large crystal grains”, so that the surface of the CVD-SiC film is “large crystal grains” in the distribution of the diameters of the crystal grains. The group occupies most of the area.

  Since the maximum value of the diameter of the crystal particle of the present invention is 300 μm or less, there is no coarse crystal particle, and thermal characteristics such as heat conduction and emissivity can be made uniform, which is suitable for applications such as semiconductors. Can be used.

  In addition, since the maximum value of the diameter of the crystal particles of the present invention is 50 μm or more, a group of “large crystal particles” that occupies most of the surface area of the CVD-SiC film includes gaps between particles formed on the surface. Thus, a dense CVD-SiC film can be formed.

Moreover, the composite material for solving the above-mentioned problem is
(9) It consists of a base material and the CVD-SiC film described above.

  The CVD-SiC film is a dense material with high purity and few pores because high-purity source gas is a raw material.

  According to the composite material of the present invention, since it is covered with a dense CVD-SiC film, the gas flow between the substrate and the outside of the CVD-SiC film can be blocked, and the substrate is corrosive to the outside. While protecting from gas, discharge | release of impurity gas from a base material can be prevented. Therefore, it is possible to provide a composite material that is strong against corrosive gas and has little emission of impurity gas.

(10) The base material is graphite.

In general, graphite has high heat resistance, high strength, and good workability, so it can be processed into various shapes. On the other hand, graphite is easy to oxidize and has a disadvantage that it is quickly consumed in a high-temperature oxidizing atmosphere.
The composite material of the present invention can prevent the base material from being oxidized by coating with the CVD-SiC film. Further, by covering with a CVD-SiC film, it is possible to make it difficult to release gas or the like adsorbed by porous graphite to the outside of the CVD-SiC film. Therefore, it is possible to provide a composite material that is excellent in heat resistance, has high strength, and can cope with various shapes.

  According to the method for producing a CVD-SiC film of the present invention, since the film is formed at a high pressure, the source gas is efficiently supplied to the base material, and the CVD-SiC film can be formed at a high film formation rate. Moreover, since it forms into a film by the photo-CVD method which irradiates a light beam, heating a base material, it can make it easy to decompose | disassemble source gas in the base-material vicinity by interaction with a heat | fever and a light beam. For this reason, the deposition of SiC in the air is prevented by suppressing decomposition of the raw material gas in the air, and the CVD-SiC film having a dense and aligned crystal direction is efficiently produced by the decomposition of the raw material gas on the surface of the substrate. It can be obtained at a high film forming speed.

  In the CVD-SiC film of the present invention, since the crystal grains having regular hexagonal pyramids at the upper end are arranged, the gap between the crystal grains can be reduced without the crystal grains being randomly stacked. For this reason, a dense CVD-SiC film with few pores can be obtained.

  Since the composite material of the present invention is covered with a dense CVD-SiC film, the flow of gas between the base material and the outside of the CVD-SiC film can be blocked, and the base material can be prevented from an external corrosive gas. While protecting, the discharge | release of the impurity gas from a base material can be prevented. Therefore, it is possible to provide a composite material that is strong against corrosive gas and has little emission of impurity gas.

It is an example of the CVD apparatus for obtaining the CVD-SiC film | membrane of embodiment of this invention. It is a table | surface which shows the test conditions and the result of a1-h5 and comparative example i1-i4 in the confirmation test of the Example of this invention. It is a schematic diagram which shows the orientation direction analyzed from the peak obtained by analyzing the CVD-SiC film obtained by the test of a1-h5 in the confirmation test of the Example of this invention by the X ray diffraction method. FIG. 4 is a partially enlarged view of the schematic diagram of FIG. 3, in which the range of 4 to 10 kPa is enlarged and the vertical axis is expressed as a real axis, and is divided into the orientation directions of the CVD-SiC film. It is explanatory drawing which shows the film-forming speed | rate in the test of a1-h5 in the confirmation test of the Example of this invention. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of a1 whose total pressure in the confirmation test of the Example of this invention is 2 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of a2 whose total pressure in the confirmation test of the Example of this invention is 2 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of a3 whose total pressure in the confirmation test of the Example of this invention is 2 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of a4 whose total pressure in the confirmation test of the Example of this invention is 2 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of a5 whose total pressure in the confirmation test of the Example of this invention is 2 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of b1 whose total pressure in the confirmation test of the Example of this invention is 4 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of b2 whose total pressure in the confirmation test of the Example of this invention is 4 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of b3 whose total pressure in the confirmation test of the Example of this invention is 4 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of b4 whose total pressure in the confirmation test of the Example of this invention is 4 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of b5 whose total pressure in the confirmation test of the Example of this invention is 4 kPa. It is a SEM photograph of the CVD-SiC film obtained with the sample of c1 whose total pressure in the confirmation test of the Example of this invention is 5 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of c2 whose total pressure in the confirmation test of the Example of this invention is 5 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of c3 whose total pressure in the confirmation test of the Example of this invention is 5 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of c4 whose total pressure in the confirmation test of the Example of this invention is 5 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of c5 whose total pressure in the confirmation test of the Example of this invention is 5 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of d1 whose total pressure in the confirmation test of the Example of this invention is 6 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of d2 whose total pressure in the confirmation test of the Example of this invention is 6 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of d3 whose total pressure in the confirmation test of the Example of this invention is 6 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of d4 whose total pressure in the confirmation test of the Example of this invention is 6 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of d5 whose total pressure in the confirmation test of the Example of this invention is 6 kPa. It is a SEM photograph of the CVD-SiC film obtained with the sample of e1 whose total pressure in the confirmation test of the Example of this invention is 8 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of e2 whose total pressure in the confirmation test of the Example of this invention is 8 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of e3 whose total pressure in the confirmation test of the Example of this invention is 8 kPa. It is a SEM photograph of the CVD-SiC film obtained with the sample of e4 whose total pressure in the confirmation test of the example of the present invention is 8 kPa. It is a SEM photograph of the CVD-SiC film obtained with the sample of e5 whose total pressure in the confirmation test of the example of the present invention is 8 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of f1 whose total pressure in the confirmation test of the Example of this invention is 10 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of f2 whose total pressure in the confirmation test of the Example of this invention is 10 kPa. It is the SEM photograph of the CVD-SiC film | membrane obtained with the sample of f3 whose total pressure in the confirmation test of the Example of this invention is 10 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of f4 whose total pressure in the confirmation test of the Example of this invention is 10 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of f5 whose total pressure in the confirmation test of the Example of this invention is 10 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of g1 whose total pressure in the confirmation test of the Example of this invention is 20 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of g2 whose total pressure in the confirmation test of the Example of this invention is 20 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of g3 whose total pressure in the confirmation test of the Example of this invention is 20 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of g4 whose total pressure in the confirmation test of the Example of this invention is 20 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of g5 whose total pressure in the confirmation test of the Example of this invention is 20 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of h1 whose total pressure in the confirmation test of the Example of this invention is 40 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of h2 whose total pressure in the confirmation test of the Example of this invention is 40 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of h3 whose total pressure in the confirmation test of the Example of this invention is 40 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of h4 whose total pressure in the confirmation test of the Example of this invention is 40 kPa. It is a SEM photograph of the CVD-SiC film | membrane obtained with the sample of h5 whose total pressure in the confirmation test of the Example of this invention is 40 kPa. It is a SEM photograph of the CVD-SiC film | membrane of the sample of i1 obtained by the film-forming test by the thermal CVD method which is a comparative example of this invention. It is a SEM photograph of the CVD-SiC film | membrane of the sample of i2 obtained by the film-forming test by the thermal CVD method which is a comparative example of this invention. It is a SEM photograph of the CVD-SiC film | membrane of the sample of i3 obtained by the film-forming test by the thermal CVD method which is a comparative example of this invention. It is a SEM photograph of the CVD-SiC film of the sample of i4 obtained by the film-forming test by the thermal CVD method which is a comparative example of the present invention.

  Embodiments of the CVD-SiC film and the CVD-SiC film manufacturing method of the present invention will be described below. First, a CVD-SiC film manufacturing apparatus will be described.

  FIG. 1 is a schematic view of a CVD apparatus 100 which is a CVD-SiC film manufacturing apparatus. The CVD apparatus 100 includes a CVD furnace 10 as a casing, a radiation thermometer 21, an introduction pipe 22, a light source 23, a drive source 31, a support member 32, a table 33, a heating device 41, and a graphite heater. 42.

  The CVD furnace 10 is formed of stainless steel or the like, and a base material (graphite base material) S as a sample is disposed therein. The radiation thermometer 21, the introduction pipe 22, and the light source 23 are disposed on the upper surface of the CVD furnace 10. The radiation thermometer 21 can measure the temperature inside the CVD furnace 10 and thus the film forming temperature on the graphite substrate S from the radiant heat inside the CVD furnace 10. An introduction pipe 22 that is a raw material supply unit supplies a raw material gas into the CVD furnace 10. The light source 23 is composed of a semiconductor laser or the like, and irradiates the graphite base S with a laser beam L.

  A drive source 31 configured by a motor or the like drives the support member 32 and the table 33 in the X direction and the Y direction. The graphite substrate S is disposed on the table 33, and the table 33 connected to the drive source 31 by the support member 32 moves in the X direction and the Y direction, so that the irradiation position of the laser beam L on the graphite substrate S is reached. Also move in the X and Y directions.

  On the lower surface of the CVD furnace 10, a heating device 41 and a graphite heater 42 as a heating heater are provided. When the heating device 41 is driven, the graphite heater 42 generates heat and heats the inside of the CVD furnace 10.

  The CVD apparatus 100 is provided with other control devices, vacuum pumps, valves, and other members, but the specific configuration of the CVD apparatus 100 is not particularly limited.

  The source gas supplied to the CVD furnace 10 is not particularly limited. For example, a source gas such as methyltrichlorosilane (MTS) having a carbon source and a silicon source at the same time, a source gas in which a carbon source and a silicon source are mixed, and the like can be used. As the carbon source, for example, methane, ethane, propane and the like can be used. As the silicon source, for example, halogenated silane such as tetrachlorosilane can be used in addition to silane.

  Further, the CVD method of the present invention uses light and heat as excitation energy to decompose the raw material gas. For this reason, the CVD furnace has a heater (graphite heater 42) and a light source 23. The heater transmits heat to the base material (graphite base material S) in the form of radiant heat, and the light source 23 irradiates the surface of the base material with a light beam (laser beam L). The light source 23 is not particularly limited, but any light bulb, discharge lamp, laser, or the like can be used. The light source 23 is provided outside the CVD furnace in FIG. 1, but may be provided inside the CVD furnace. When provided outside the CVD furnace as shown in FIG. 1, the substrate can be irradiated with light rays through a transparent window provided in the CVD furnace 10.

  Here, in the CVD method, the film forming temperature (t [K]) of the graphite substrate S and the total pressure (p [kPa]) inside the CVD furnace 10 satisfy the following formula (1). That is, the base material inside the CVD furnace 10 in which the base material is disposed is irradiated with light rays, and a constant temperature and pressure relationship is maintained.

  According to the method for producing a CVD-SiC film of the present invention, a film is formed at a high pressure satisfying the formula (1) by using a photo-CVD method that irradiates a substrate with light among CVD methods. Therefore, it is considered that a large number of columnar crystal particles extending in the direction perpendicular to the surface of the substrate (the film thickness direction of the CVD-SiC film) can be obtained. This is the next mechanism.

  In general, a CVD-SiC film by thermal CVD is known to be easily oriented in the 111 direction at low temperatures (the direction perpendicular to the 111 plane and the [111] direction), and at high temperatures, it tends to be oriented in other directions. Yes. In JP1994-92761A (0012), which is a thermal CVD method, under the conditions of 1323-1473K and 1.3-13kPa, a 111 orientation with a high degree of orientation in the 111 direction is obtained, the temperature is high, and the pressure is low. As the degree of orientation increases, the degree of orientation in the other direction increases, making it difficult to obtain the 111 orientation. Under the conditions of 1473 to 1623K and 0.13 to 1.3 kPa, a 220 orientation having a high degree of orientation in the 220 direction is obtained. It is described. This is based on the difference in the growth rate of SiC crystal grains and is considered to be due to the high growth rate in the 111 direction. In the thermal CVD method at a low film forming temperature, in the process of growing the CVD-SiC film from the surface of the substrate, growth other than the 111 direction with a high growth rate is suppressed, and a CVD-SiC film oriented in the 111 direction is obtained. It becomes easy. In the thermal CVD method, by increasing the film-forming temperature, the source gas is decomposed in the air and the decomposition products are deposited. Therefore, the 111 direction with a high growth rate is laid down, and the CVD − oriented in the 111 direction. It is thought that it becomes difficult to obtain a SiC film.

  On the other hand, according to the method for producing a CVD-SiC film by the photo-CVD method of the present invention, the source gas is decomposed on the surface of the substrate by the interaction of light and heat. For this reason, since the growth rate on the surface of the substrate irradiated with light is relatively faster than the growth rate of the crystal particles in the air, the crystal particles are less likely to lie down in the 111 direction where the growth rate is fast. An oriented CVD-SiC film can be grown at a high rate.

  In addition, since the crystal grains oriented in the 111 direction are obtained with a pointed tip, the irradiated light repeatedly acts on decomposition of the source gas while repeating reflection. For this reason, it is considered that the source gas can be efficiently decomposed on the surface of the substrate, and a CVD-SiC film having a high degree of orientation in the 111 direction can be obtained efficiently. Furthermore, the irradiated light is absorbed between the sharp crystal grains while repeating reflection. For this reason, it is thought that the growth of the CVD-SiC film can be promoted even in the gap formed between the crystal grains, and a dense CVD-SiC film can be obtained.

  The total pressure p described above is preferably set in the range of 6 to 10 kPa. If the total pressure in the CVD furnace 10 during film formation is 6 kPa or more, the raw material gas can be sufficiently supplied to the graphite substrate S, so that a dense CVD-SiC film with a uniform crystal orientation can be formed efficiently. can do. Further, when the total pressure in the CVD furnace 10 at the time of film formation is 10 kPa or less, the absorption of the light beam by the source gas can be suppressed, so the decomposition of the source gas until the laser beam L reaches the graphite substrate S. And the decomposition of the source gas in the air can be suppressed, and a dense CVD-SiC film having a uniform crystal direction can be obtained efficiently at a high film formation rate.

  Moreover, it is preferable that the film-forming temperature t mentioned above is the range of 1600-1700K. When the film forming temperature t is 1600 K or more, the energy of the laser beam L required for film formation can be reduced. For this reason, the decomposition of the raw material gas can be suppressed in the optical path before reaching the surface of the graphite base material S, and the raw material can be efficiently decomposed on the surface of the graphite base material S. Further, if the film forming temperature is 1700 K or less, the CVD-SiC film cannot be sufficiently formed only by the action of thermal CVD, and the CVD- on the surface of the graphite substrate S in combination with the action of the laser beam L. Formation of the SiC film can be promoted. For this reason, it is possible to prevent disordered deposition of SiC by suppressing decomposition of the source gas in the air, and to promote formation of a CVD-SiC film on the surface of the graphite substrate S. It is possible to obtain a CVD-SiC film having a uniform thickness at a high film forming speed.

  Further, the laser beam L preferably has a wavelength of 1500 nm or less. If the wavelength of the laser beam L is 1500 nm or less, the source gas is decomposed and the photon energy is sufficient to obtain a CVD-SiC film. It can be obtained at a high film forming speed.

Next, the manufactured CVD-SiC film is described by an index called “Lotgering Factor” (also referred to as “Lotgering orientation degree”). Lugging factor is a method for evaluating the degree of crystal orientation by eliminating the influence of the half-width in X-ray diffraction, the performance of the analyzer, etc., and can be obtained by analyzing the diffraction pattern of X-ray diffraction. it can. In the case of a fully oriented sample, the numerical value is 1, and in the case of a randomly oriented sample, it is 0. In the present document, the lugging factor in the hkl direction is represented by the symbol F _hkl , for example, the lugging factor in the 111 direction is represented as F ₁₁₁ .

In the CVD-SiC film of the present invention, F ₁₁₁ in the direction of the film thickness of the CVD-SiC film (perpendicular to the surface of the base material) is 0.8 to 1.0, and the strongly oriented 111 direction is Since it is composed of a CVD-SiC film oriented in the direction of the film thickness, it is possible to obtain a denser CVD-SiC film with less disruption of crystal grain arrangement and more precise and less pores.

Hereinafter, a method for calculating the degree of Rotgering orientation F _hkl in the hkl direction will be described. First, the X-ray diffraction pattern of the target sample is measured, and the degree of orientation is evaluated by comparison with the X-ray diffraction pattern of the non-oriented sample.

The following equation (2) is a calculation equation for calculating F _hkl , and equation (3) is a calculation equation for calculating the value of P used in equation (2).

P _hkl is the sum of peaks related to the measured orientation with respect to the sum of peaks of the target sample. For example, in the case of ΣI ₍₁₁₁₎ , ΣI _(hkl) is the total sum of I ₍₁₁₁₎ , I ₍₂₂₂₎ ,..., I _(nnn) , which is an integral multiple of the (111) direction, and ΣI _{(002) ) Is} the total sum of I ₍₀₀₂₎ , I ₍₀₀₄₎ ,..., I _(00n) which is an integer multiple of the (002) direction. ΣI is the sum of all peaks of the target sample.

P ₀ is the sum of peaks related to the orientation to be measured with respect to the sum of peaks in the non-oriented sample. Calculate in the same manner as P.

As described above, the CVD-SiC film of the present invention has a 111-direction Lugging Factor, F ₁₁₁ of 0.8 to 1.0. The crystal grains extend in the film thickness direction, and the upper end portion has a regular hexagonal pyramid shape. That is, the crystal grains extend in a direction perpendicular to the surface of the base material on which the CVD-SiC film is grown (a plane perpendicular to the thickness direction of the CVD-SiC film), and a large number of crystal grains are arranged. . Therefore, the gap between the crystal particles can be reduced without the crystal particles being randomly stacked. For this reason, a dense CVD-SiC film with few pores can be obtained.

  The upper end portion of the crystal particle has a regular hexagonal pyramid shape. The regular hexagon overlaps with the original figure every time it is rotated by 60 °, and three times the inner angle becomes 360 °, so that the columnar crystal grains can be arranged so as to reduce the gap between them. For this reason, it is considered that crystal grains with disordered crystal directions are not easily formed in the gaps, and a dense CVD-SiC film with few gaps can be obtained.

  In addition, since the upper end of the crystal particle has a regular hexagonal pyramid shape and the tip is sharp, there is no flat surface for reflecting light toward the front. That is, since the surface of the CVD-SiC film is constituted only by the slope, the incident light is scattered, and the regular reflectance can be made less affected by the ratio of the flat surface to the slope. For this reason, the influence which it has on reflection by the way of growth of crystal grains can be reduced.

Further, F ₁₁₁ is more preferably 0.9 to 1.00. In this range, the CVD-SiC film is oriented more strongly in the 111 direction with respect to the film thickness direction, so that it is possible to obtain a dense CVD-SiC film with less disorder in the arrangement of crystal grains and with less porosity. .

  Moreover, it is preferable that the maximum value of the diameter of a crystal particle is 50-300 micrometers. Here, the maximum value of the diameter of the crystal grain is the diameter of the largest crystal grain among the many scattered crystal grains.

  In general, in a CVD-SiC film, crystal grains gradually grow from the start to the end of film formation in a CVD furnace. The size of the crystal particles is the largest that has grown continuously from the start to the end of film formation, the one that stopped growing in the middle of film formation, the one that started growth from the middle of film formation, It becomes smaller than that. For this reason, the largest crystal particle observed on the surface of the CVD-SiC film has grown from the start of film formation, and in the distribution of the diameter of the crystal particle, crystal particles of almost the same size are “large” “Small crystal particles” that form a group of “crystal particles” and that start growing in the middle of film formation fill the gap. For this reason, specifically large crystal grains do not exist. In addition, since a large number of crystal grains grow at the start of film formation, they grow into “large crystal grains”, so that the surface of the CVD-SiC film is “large crystal grains” in the distribution of the diameters of the crystal grains. The group occupies most of the area.

When the maximum value of the diameter of the crystal particle is 300 μm or less, there is no coarse crystal particle, and thermal characteristics such as heat conduction and emissivity can be made uniform. For example, it is suitably used in applications such as semiconductors. be able to.
Further, when the maximum value of the diameter of the crystal particles is 50 μm or more, the group of “large crystal particles” that occupies most of the surface area of the CVD-SiC film determines the number of gaps between the particles formed on the surface. And a dense CVD-SiC film can be formed.

Furthermore, a composite material is formed from the base material and the above-described CVD-SiC film.
The CVD-SiC film is a dense material with high purity and few pores because high-purity source gas is a raw material.
According to the composite material of the present invention, since it is covered with a dense CVD-SiC film, the gas flow between the substrate and the outside of the CVD-SiC film can be blocked, and the substrate is corrosive to the outside. While protecting from gas, discharge | release of impurity gas from a base material can be prevented. Therefore, it is possible to provide a composite material that is strong against corrosive gas and has little emission of impurity gas.

The base material is preferably graphite.
In general, graphite has high heat resistance, high strength, and good workability, so it can be processed into various shapes. On the other hand, graphite is easy to oxidize, and its disadvantage is that it is consumed quickly in a high-temperature oxidizing atmosphere.
The composite material of the present invention can prevent the base material from being oxidized by coating with the CVD-SiC film. Further, by covering with a CVD-SiC film, it is possible to make it difficult to release gas or the like adsorbed by porous graphite to the outside of the CVD-SiC film. Therefore, it is possible to provide a composite material that is excellent in heat resistance, has high strength, and can cope with various shapes.

  The method for producing a CVD-SiC film of the present invention will be specifically described with reference to FIG.

  First, the graphite base material S is put into the CVD furnace 10 of the CVD apparatus 100. Below the graphite substrate S, a graphite heater 42 is provided. An external heating device 41 can pass a current through the graphite heater 42 and generate heat due to resistance heat generation of the graphite heater 42. The heat generation method is not limited to this, and other methods such as induction heating and high-frequency overheating can be used and are not particularly limited.

  The upper part of the CVD furnace 10 is irradiated with a laser beam L from a light source 23 through, for example, a quartz glass window. Quartz glass has a small thermal expansion coefficient, has heat resistance, and has a high transmittance from the ultraviolet region to the infrared region, and thus can be suitably used as a material constituting the window. The laser beam has a high output, and an antireflection coating is applied to the incident surface of the quartz glass in accordance with the laser wavelength in order to prevent thermal damage and injury of the optical component due to reflection. For example, it is preferable to use a fluorine-based optical coating.

  As the light source 23, for example, a laser light source can be used. As the laser light source, a semiconductor laser, a gas laser, or the like can be used and is not particularly limited. The laser beam L is irradiated onto the graphite substrate S from the light source through the window. Moreover, the temperature of the surface of the graphite base material S can be measured using the radiation thermometer 21 through another window.

  For example, an upper portion of the CVD furnace 10 has a source gas introduction pipe 22. The source gas can be supplied into the CVD furnace 10 through the source gas introduction pipe 22.

  Prior to the deposition of the CVD-SiC film, the gas inside the CVD furnace 10 is exhausted by a vacuum pump, the pressure is reduced, and the interior of the furnace is heated to the deposition temperature. The pressure inside the CVD furnace (total pressure) and the film forming temperature are set to 8 kPa and 1623 K, respectively, for example. The film forming temperature is the temperature of the surface of the graphite substrate S. Heating and decompression may be performed simultaneously or in the reverse order, and the order is not particularly limited.

  Next, the surface of the graphite substrate S is irradiated with a laser beam L from the light source 23 through a quartz glass window. As the light source 23, for example, an AlGaAs semiconductor laser can be used.

  A CVD-SiC film is grown on the graphite substrate S using the drive source 31, the support member, and the table 33 while moving the graphite substrate S and thermally decomposing the source gas with the laser beam L. In the example of FIG. 1, the graphite substrate S is moved when forming the CVD-SiC film. However, the light source 23 may be driven and the laser beam L may be moved while the graphite substrate S is fixed.

  In this way, a CVD-SiC film can be formed on the surface of the graphite substrate S. The obtained CVD-SiC film may be used together with the graphite substrate S, or the graphite substrate S may be separated and used only as the CVD-SiC film. For example, when the substrate is graphite as in this example, the CVD-SiC film can be separated by cutting, oxidation in an oxidizing atmosphere, or mechanical peeling. When the CVD-SiC film is mechanically separated from the substrate, it is desirable to seal the pores on the surface of the substrate so that the CVD-SiC film does not enter the pores of the substrate. As a sealing method, the pores can be sealed by covering with glassy carbon, pyrolytic carbon or the like, and can be easily peeled off. In this way, the CVD-SiC film can be separated from the substrate.

(Example)
In order to confirm the range in which the CVD-SiC film of the present invention can be produced, a CVD-SiC film is formed by a photo-CVD method using a laser beam while heating the substrate, and the properties of the obtained CVD-SiC film are confirmed. did.

  The test level is 8 levels for pressure conditions and 5 levels for temperature conditions.

  The test conditions were distinguished by assigning symbols a1 to a5, b1 to b5, c1 to c5, d1 to d5, e1 to e5, f1 to f5, g1 to g5, and h1 to h5.

  The subscript alphabet indicates the total pressure in the CVD furnace, “a” is 2 kPa, “b” is 4 kPa, “c” is 5 kPa, “d” is 6 kPa, “e” is 8 kPa, and “f” is 10 kPa. , “G” is 20 kPa, and “h” is 40 kPa.

  The number of the subscript indicates the film forming temperature in the CVD furnace. “1” is 1473K, “2” is 1523K, “3” is 1573K, “4” is 1623K, and “5” is 1673K.

Common manufacturing conditions are shown below.
Vaporizer: Bubbling of liquid source CVD furnace: Horizontal furnace Light source: Semiconductor laser (AlGaAs)
Beam diameter: 10mm
Wavelength: 1064nm
Heating: Graphite heater Exhaust: Dry vacuum pump Exhaust treatment: Filter, cold trap, scrubber Control: Labview
Base material: Graphite base material (φ10 × 1mm)
Temperature measurement: Radiation thermometer Source gas: SiCl ₄ , CH ₄ , H ₂
Gas ratio:
SiCl ₄ : CH ₄ : H ₂ = 1: 0.5: 3.5

The graphite substrate was placed on a table in a CVD furnace, then the furnace was closed and evacuated. After sufficiently reducing the pressure with a vacuum pump, the inside of the furnace was heated with a graphite heater as an auxiliary heating source. After heating so that the temperature of a graphite base material might become 1273K over 60 minutes, after irradiating a laser beam and stabilizing the temperature of a graphite base material, source gas was flowed and the CVD-SiC film was grown.
After flowing a source gas for 30 minutes to form a CVD-SiC film, the source gas was stopped and the film formation was stopped.
The laser beam output is 350 W at the level of a1 to h1 where the film forming temperature is 1473 K, 400 W at the level of a2 to h2 where the film forming temperature is 1523 K, and 450 W at the level of a3 to h3 where the film forming temperature is 1573 K. The film forming temperature was set to 500 W at the level of a4 to h4 where the film forming temperature was 1623 K, and 550 W at the level of a5 to h5 where the film forming temperature was 1673 K, and the temperature was finely adjusted by heating with laser light.

  The total pressure in the CVD furnace is adjusted by adjusting the opening of the exhaust valve. An exhaust valve is provided between the vacuum pump and the CVD furnace.

  In order to compare the total pressure [kPa] and the value of “−0.04t + 72” calculated from the film forming temperature [K], the value of the following formula (4) was calculated. If the obtained value is “positive” or “0”, the condition of the expression (1) is satisfied, and if it is “negative”, the condition of the expression (1) is not satisfied.

  Next, a sample of the obtained CVD-SiC film was analyzed by an X-ray diffraction method, the obtained chart was analyzed, the orientation direction was confirmed, and a 111-direction Lottery Factor was obtained. Further, the film forming speed was calculated from the thickness of the obtained SiC film and the film forming time.

  FIG. 2 is a table showing the test conditions and the results obtained. FIG. 3 is a schematic diagram showing the orientation direction analyzed from the obtained peak by analyzing the CVD-SiC film obtained in the tests a1 to h5 in the confirmation test of the example by the X-ray diffraction method. FIG. 4 is a partially enlarged view of the schematic diagram of FIG. 3, in which the range of 4 to 10 kPa is enlarged and the vertical axis is expressed as a real axis, divided into the orientation directions of the CVD-SiC film. doing. FIG. 5 is an explanatory diagram showing the film forming speed in the tests a1 to h5 in the confirmation test of the example of the present invention. Further, the obtained CVD-SiC film was photographed by SEM. SEM photographs obtained by photographing are shown in FIGS.

The “total pressure” is the pressure in the CVD furnace [kPa], the film forming temperature is the surface temperature [K] of the substrate, the film forming speed is the film forming speed [μm / h] of the obtained CVD-SiC film, “P − (− 0.04t + 72)” is an expression for determining the expression (1) corresponding to the expression (4), and is “positive” or “0”. F ₁₁₁ is a calculated 111-direction logger factor. In addition, the presence or absence of the formation of “crystal particles having a regular hexagonal pyramid whose upper end extending in the direction perpendicular to the surface of the substrate” was determined from the SEM photograph. Furthermore, “the maximum value of the diameter of the crystal particles” was measured from the SEM photograph at a level where “the crystal particles having a regular hexagonal pyramid at the upper end extending in the direction perpendicular to the surface of the substrate” were formed.

In the samples of d5, e4, e5, f3, f4, f5, g1 to g5, and h1 to h5 in which the value of “p − (− 0.04t + 72)” is positive, a high film forming speed is obtained. The F- ₁₁₁ value of the obtained CVD-SiC film was in the range of 0.8 to 1.0, and it was confirmed that the film was strongly oriented in the 111 direction. Further, in the samples of d5, e4, e5, f3, f4, and f5 having a pressure of 10 kPa or less, “crystal particles having a regular hexagonal pyramid with an upper end extending in a direction perpendicular to the surface of the substrate” are obtained. It was confirmed that the “maximum value of the diameter of the particles” was 50 to 300 μm.

<Comparative example>
FIG. 14 shows an SEM photograph of a CVD-SiC film formed by a thermal CVD method heated only by an auxiliary heating source without irradiating a laser beam. Since these manufacturing methods are not photo CVD methods, they do not correspond to the manufacturing method of the CVD-SiC film of the present invention. In the i1 sample (FIG. 14A) having a low film forming temperature of 1473K, a 111-oriented CVD-SiC film is obtained, but the film forming speed is slow. The i1 sample (FIG. 14D) having a high film forming temperature of 1773 K had a high film forming speed, but had 110 orientation and 111 orientation could not be obtained. In these intermediate 1573K i2 (FIG. 14B) and 1673K i3 (FIG. 14C) samples, a 111-oriented and 110-oriented CVD-SiC film is obtained, and a 111-oriented CVD-SiC film is obtained. There wasn't. That is, in the thermal CVD method, it was confirmed that the 111 orientation could be obtained at a low temperature but the film forming speed was low, and the film forming speed was high at a high temperature but the 111 orientation could not be obtained.

10 CVD furnace (housing)
21 Radiation thermometer 22 Introduction pipe (raw material supply part)
23 light source 31 drive source 32 support member 33 table 41 heating device 42 graphite heater (heating heater)
100 CVD equipment S Graphite base material (base material)

Claims (10)

A method for producing a CVD-SiC film by a CVD method in which a source gas is supplied and deposited on a substrate in a CVD furnace,
The CVD method is a photo-CVD method in which a substrate is irradiated with light, and a film forming temperature (t [K]) and a total pressure (p [kPa]) satisfy the following formula (1). A method for producing a CVD-SiC film.
  The method for producing a CVD-SiC film according to claim 1, wherein the total pressure p is 6 to 10 kPa.   The method for producing a CVD-SiC film according to claim 1 or 2, wherein the film-forming temperature t is 1600 to 1700K.   The method for producing a CVD-SiC film according to claim 1, wherein the light beam has a wavelength of 1500 nm or less.   The CVD-SiC film manufactured with the manufacturing method as described in any one of Claims 1-4. Extends in the direction of the film thickness, the upper end includes crystal grains of regular hexagonal pyramids,
A CVD-SiC film, wherein F ₁₁₁ in the film thickness direction (Lotting Factor in the 111 direction) is 0.8 to 1.0. The CVD-SiC film according to claim 6, wherein the F ₁₁₁ is 0.9 to 1.0.   The CVD-SiC film according to claim 6 or 7, wherein the CVD-SiC film has a maximum diameter of the crystal grains of 50 to 300 µm.   The composite material which consists of a base material and the CVD-SiC film as described in any one of Claims 6-8. The composite material according to claim 9, wherein the base material is graphite.