JP2019119612A - Pyrolytic boron nitride, method for manufacturing the same, and crystal growth apparatus using pyrolytic boron nitride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pyrolytic boron nitride and a method for producing the pyrolytic boron nitride, which can suppress the adhesion of foreign substances to the crystal surface during crystal growth and suppress the formation of polycrystalline grains. A pyrolytic boron nitride produced by a thermal decomposition CVD method, wherein the ratio of the area of a portion having a peak at Raman shift 2800 to 3000 cm-1 to the total surface area of the pyrolytic boron nitride is 0.01 or less. Pyrolytic Boron Nitride is provided. Such pyrolytic boron nitride can be produced by contacting the surface of pyrolytic boron nitride by a thermal decomposition CVD method with a mixed solution of sulfuric acid and hydrogen peroxide solution. [Selection diagram] None

Description

  The present invention relates to novel pyrolytic boron nitride and a method of making pyrolytic boron nitride. More specifically, the present invention relates to a method of manufacturing pyrolytic boron nitride and pyrolytic boron nitride applicable to members in a crystal growth apparatus in which adhesion of foreign matter to crystals is small even if crystal growth is repeated.

  Generally, pyrolytic boron nitride (hereinafter, also referred to as "pBN") is produced by a thermal decomposition CVD method using boron halide such as boron chloride or boron fluoride and ammonia as raw materials. Since pyrolytic boron nitride material has high thermal stability and chemical stability, and can be formed into various shapes by the above method, it is a material widely used as a member in a reaction vessel of a crystal growth apparatus It is.

  As a crystal growth apparatus, vapor phase growth such as hydride vapor phase epitaxy (HVPE) method, metal organic chemical vapor deposition (MOCVD) method, physical vapor transport (PVT) method, etc. An apparatus, a liquid phase growth apparatus such as a liquid encapsulated pull (LEC: Liquid Encapsulated Czochralski) method, a horizontal Bridgman (HB: Horizontal Bridgman) method, and the like can be mentioned. Moreover, as a crystal grown by this apparatus, a single crystal of a Group III-V compound such as aluminum nitride, gallium nitride and gallium arsenide, and a single crystal of a Group II-VI compound such as zinc oxide and zinc selenide can be mentioned. As described above, pyrolytic boron nitride is used in various compounds and members in the reaction vessel of the crystal growth apparatus in various growth methods.

  As a problem at the time of crystal production using the above-mentioned crystal growth apparatus, there is adhesion of foreign matter to a crystal growth surface. If crystal growth is performed in the state where foreign matter adheres to the crystal surface, it may cause generation of crystal defects due to crystal growth abnormality around the adhered foreign matter, and polycrystal grains may be formed.

  Here, due to adhesion of foreign matter to the crystal growth surface, elements and compounds of the device member are released into the atmosphere and adhere to the base substrate due to heating and deterioration of the device member due to contact with the atmosphere gas such as source gas. In some cases, it is considered that crystal particles and the like that are generated as a secondary reaction during crystal growth may adhere to the base substrate, and various methods for performing crystal growth while preventing the adhesion of these foreign substances have been proposed. There is. For example, as suppression of deterioration of pBN members, pBN members with controlled surface peeling thickness (Patent Document 1) and pBN members with suppressed cracking during heating and cooling (Patent Document 2) have been proposed. . Moreover, as suppression of the adhesion of foreign substances due to secondary reactions during crystal growth, the particles produced by the gas phase reaction are prevented from adhering to the crystal growth surface by adjusting the flow of gas in the reactor, Methods for producing high-quality single crystals (Patent Document 3) and suppression of side reactions by supply of halogen-based gas (Patent Document 4) have been proposed.

Patent No. 4144847 Unexamined-Japanese-Patent 2016-113338 International Publication WO 2014/031119 JP 2015-017030

  By the above-mentioned method, suppression of adhesion of foreign matter is achieved to some extent, and high-quality crystals in which the formation of polycrystal grains is suppressed to a certain extent can be produced, but the above measures have been taken It has been found that, even if taken, the formation of polycrystalline grains can not be completely suppressed. In particular, when crystal growth is repeated using the same crystal growth apparatus, the formation of polycrystalline grains on the crystal surface increases as the number of repetitions increases, and the polycrystalline grains are the inner wall surface of the crystal growth apparatus It has been found that the foreign matter adhering to C. is caused by flying and adhering to the crystal surface before or during crystal growth.

  Usually, when performing crystal growth repeatedly using the same crystal growth apparatus, a carrier gas such as hydrogen gas or nitrogen gas, or hydrogen chloride gas or chlorine gas or the like is used to remove foreign substances and the like in the crystal growth apparatus. Although crystal growth is performed after heat treatment with an acid gas or the like, foreign matter in the crystal growth apparatus can not be completely removed even by such heat treatment, and polycrystal formation due to adhesion of foreign matter to the crystal is It turned out that it can not control. That is, an object of the present invention is to provide pyrolytic boron nitride capable of suppressing adhesion of foreign matter to the crystal surface at the time of crystal growth and suppressing formation of polycrystalline grains, and a method for producing the pyrolytic boron nitride.

  The present inventors diligently studied to solve the above problems. First, when the surface of a general pyrolytic boron nitride member used in a crystal growth apparatus was observed, the surface formed a generally smooth and uniform surface, but some of the other regions It was found that there are sites exhibiting different surface morphology. Such a region often has a convex shape with respect to other regions, and further, the region contains a larger amount of oxygen than other regions according to the result of elemental analysis, and a high wave number region in the Raman spectrum It also turned out to have a peak in Then, for example, an aluminum nitride single crystal is grown using a crystal growth apparatus using such pyrolytic boron nitride, and after the growth, elemental analysis of the surface of the used pyrolytic boron nitride member is carried out, and it is said that It has been found that a large amount of foreign substances containing aluminum and chlorine tend to be present at sites showing different surface morphologies. Furthermore, after performing the heat processing using chlorine gas as said heat processing, as a result of conducting an elemental analysis of the surface of the pyrolytic boron nitride member after a process, it also turned out that chlorine exists in the said site | part.

Therefore, as a result of reducing the site showing the different surface morphology on the surface of pyrolytic boron nitride and further studying the method of homogenizing the surface of pyrolytic boron nitride, the surface of pyrolytic boron nitride is made of sulfuric acid and hydrogen peroxide solution. The above-mentioned portion disappears by contacting with the mixed liquid, and as a result of repeated crystal growth using the crystal growth apparatus using pyrolytic boron nitride which has been subjected to such treatment, adhesion of foreign matter is suppressed. It has been found that crystals in which the formation of polycrystalline grains is suppressed can be stably produced, and the present invention has been completed. That is, the first aspect of the present invention is pyrolytic boron nitride produced by a thermal decomposition CVD method, wherein the ratio of the area of a site having a peak at a Raman shift of 2800 to 3000 cm ⁻¹ with respect to the total surface area of the pyrolytic boron nitride Is a number less than 0.01. It is. Second, the present invention is a method for producing pyrolytic boron nitride, characterized in that the surface of a pyrolytic boron nitride member produced by a thermal decomposition CVD method is brought into contact with a mixed solution of sulfuric acid and hydrogen peroxide water. is there. A third aspect of the present invention is a crystal growth apparatus comprising the pyrolytic boron nitride according to the first aspect of the present invention.

  The pyrolytic boron nitride of the present invention is pyrolytic boron nitride having a uniform surface.

  By performing crystal growth using such a crystal growth apparatus using pyrolytic boron nitride of the present invention, it is possible to suppress the flight and adhesion of foreign matter to the crystal during growth. For this reason, a crystal with very few polycrystalline grains can be manufactured. In particular, even when the crystal growth is repeated using the same crystal growth apparatus, even if the number of times of growth is repeated, adhesion of foreign matter to the crystal surface can be stably prevented, so crystals with very few polycrystalline grains in a stable manner. Can be manufactured. Therefore, since the obtained crystal does not form pits (dents) or through holes at the time of polishing, it is possible to uniformly stack the semiconductor element layer on the crystal, and it is possible to When a wafer on which a layer is formed is manufactured and then the wafer is cut into chips, the yield of the chips can be improved.

It is the schematic of an example of the horizontal-type crystal growth apparatus using pyrolytic boron nitride of this invention.

(Pyrolytic boron nitride)
The pyrolytic boron nitride of the present invention is characterized by having a uniform surface having an area ratio of a site having a peak at a Raman shift of 2800 to 3000 cm ⁻¹ with respect to the surface area of the pyrolytic boron nitride of 0.01 or less. As described above, pyrolytic boron nitride is produced by a thermal decomposition CVD method, but it may have a part having a surface morphology different from that of another region. Such a portion has a width of several micrometers to several hundreds of micrometers (mostly a width of several tens of micrometers), and often has a convex shape with respect to other regions. The sites are scattered on the surface of pyrolytic boron nitride produced by the usual thermal decomposition CVD method, and the area (area ratio 0.05 to 0.15) of the surface area of the member is about 5 to 15%. Occupy Although the reason why foreign substances are likely to exist in such a site after crystal growth is unknown in detail, the present inventors speculate as follows. That is, at the site of the different surface morphology, it has a peak in the high wave number region, and from the result of elemental analysis it contains more oxygen compared to other regions, the compound containing oxygen at the site Is considered to be formed, and the reaction stability is considered to be low compared to other regions. When a reactive gas flows through the surface of the site during crystal growth, it is presumed that the reactive gas reacts with the site and the reactive gas adheres or adsorbs on the surface as a compound. And, at the time of crystal growth, since the reaction is carried out at a high temperature, the above-mentioned attached matter is detached by being exposed to a high temperature, and it is assumed that it flies to the crystal surface and adheres to adversely affect the crystal growth.

  On the other hand, when the pyrolytic boron nitride according to the present invention is used as a member in a crystal growth apparatus, since foreign matter is less likely to be attached, it is possible to suppress the arrival and adhesion of foreign matter to crystals during growth. it can. For this reason, a crystal with very few polycrystalline grains can be manufactured. In particular, even when the crystal growth is repeated using the same crystal growth apparatus, even if the number of times of growth is repeated, adhesion of foreign matter can be prevented stably, so that crystals with very few polycrystalline grains can be stably manufactured. Can.

In the pyrolytic boron nitride of the present invention, the smaller the proportion of the site having a peak at the Raman shift of 2800 to 3000 cm ⁻¹ , the more the adhesion of foreign matter is suppressed, so the area concerned is the area ratio to the area of the surface of the pyrolytic boron nitride Is more preferably 0.005 or less.

(Method of producing pyrolytic boron nitride)
The pyrolytic boron nitride of the present invention can be produced by contacting pyrolytic boron nitride produced using a known technique with a mixed solution of sulfuric acid and hydrogen peroxide solution. Examples of known techniques include a technique of depositing ammonia and boron halide as raw materials on a graphite substrate by a thermal decomposition CVD method. Boron chloride or boron fluoride is used as the boron halide. As described in Patent Document 1 and Patent Document 2, it is also possible to supply a gas containing carbon and a gas containing oxygen during pBN growth. In addition, the pBN member may be in a state in which the graphite substrate is coated with pBN without being separated from the graphite substrate, or may be a member formed only from pBN after being separated from the graphite substrate. good. However, in the present invention, since the process of contacting with an aqueous solution is included, it is preferable that the member is made of only pBN released from a graphite member that is easily gasified when heated while absorbing water.

  The pyrolytic boron nitride of the present invention can be produced by bringing the surface of the boron nitride member produced by the thermal decomposition CVD method into contact with a mixed solution of sulfuric acid and hydrogen peroxide solution. The composition of the mixture, the contact temperature with the pBN member and the contact time are not particularly limited as long as the above-mentioned site is removed, but the composition of the mixture is about 98% concentrated sulfuric acid and about 30% excess. Hydrogen oxide water is preferably in the range of 1: 1 to 100: 1, and more preferably in the range of 2: 1 to 10: 1. The contact temperature is preferably 50 ° C to 200 ° C, more preferably 70 ° C to 180 ° C, and still more preferably 90 ° C to 130 ° C. The contact time is preferably in the range of 1 minute to 120 minutes, and more preferably 5 minutes to 30 minutes.

  When using the pBN member brought into contact with the mixed solution in a crystal growth apparatus, it is preferable to rinse with pure water or ultrapure water so that the mixed solution component does not remain on the pBN member surface, before crystal growth It is preferable to heat in the state which distribute | circulated carrier gas, such as hydrogen gas and nitrogen gas.

When crystal growth to be described later is repeated, a crack is generated in the surface of pyrolytic boron nitride due to collision of particles flying into the reaction tube, a chemical reaction on the surface, etc., and a Raman shift of 2800 to 3000 cm from the crack. ^The site having a peak at ^-1 may be exposed. In such a case, it is preferable to make the exposed surface uniform by bringing it into contact with the mixed solution of sulfuric acid and hydrogen peroxide solution again.

(Surface analysis of pBN members)
The surface shape of the pBN member can be made by an optical microscope. In particular, it is preferable to use a Nomarski differential interference microscope in which surface asperities can be easily observed. After focusing on a smooth area on the surface of the pBN member, focus on a portion that is uneven as compared to the area, and measure the stage working distance at that time to determine the depth or height of the unevenness. can get.

The pBN member has the above-mentioned convex-shaped portion and other smooth regions. Energy dispersive elemental analysis (EDS) or an electron beam microanalyzer (EPMA) can be used to determine the respective elemental compositions. In addition, a microscopic laser Raman spectrophotometer can be used to determine each Raman shift. It is known that in BN, a peak derived from E _2g is present near a Raman shift of 1367 cm ⁻¹ . Since it turned out that a peak appears in Raman shift 2800-3000 cm < ^-1 > in the site | part to which the said foreign material tends to adhere by this examination, the measurement wavenumber range of a Raman spectrum is at least 1000-3300 cm < ^-1 >. Moreover, in order to obtain the area ratio of a portion having a peak at the Raman shift of 2800 to 3000 cm ⁻¹ with respect to the surface of the pBN member, it is preferable to measure the entire surface of the member. It is sufficient to measure the inside of the area of about 0.5 mm square to 2 mm square at five places in a grid shape. The smaller the laser irradiation area and the measurement interval at the time of measurement, the better, but since the measurement time is longer, for example, the laser irradiation size may be 1 μm to 5 μm and the measurement interval may be 1 μm to 10 μm. Since the peak appearing at the Raman shift of 2800 to 3000 cm ⁻¹ is weaker than the peak at E _{2 g} , the exposure time may be appropriately measured in 10 seconds or more and 240 seconds or less.

(Crystal growth equipment using pyrolytic boron nitride)
As described above, by growing crystals using the crystal growth apparatus using pyrolytic boron nitride according to the present invention, it is possible to prevent the adhesion of foreign substances during single crystal growth.

  FIG. 1 is a schematic view of an example of a horizontal group-III nitride single crystal vapor deposition apparatus using pyrolytic boron nitride according to the present invention. The apparatus 100 shown in FIG. 1 is made of an integral reaction tube 10, and includes a raw material portion 30 for producing a group III source gas, a growth portion 31 for growing a group III nitride single crystal, a carrier gas and an unreacted gas. The exhaust unit 34 exhausts the air. In the raw material part, while the raw material part reaction tube 38 filled with the group III metal 40 is heated by the raw material part external heating means 35, a halogen-based gas is introduced from the raw material generating halogen based gas introduction pipe 39 Group halide gas is generated. The generated group III halide gas is mixed with the halogen-based gas supplied from the additional halogen-based gas introduction pipe 41 and supplied from the group III source gas supply nozzle 42 to the growth portion 31. The nitrogen source gas introduced from the nitrogen source gas introduction pipe 43 is mixed with the halogen gas introduced from the additional halogen gas (for nitrogen source gas) introduction pipe 44, and the nitrogen source gas supply nozzle 45 to the growth portion 31 Supplied. Also, in order to supply the source gases efficiently onto the base substrate 20, the pushing carrier gas is supplied from the pushing carrier gas introduction unit 33 to the growing unit. The group III source gas and the nitrogen source gas supplied to the growth portion react on the base substrate 20 placed on the susceptor 32 to grow a group III nitride single crystal. At this time, the susceptor 32 is heated by the local heating unit 37, and the members in the growth portion 31 are heated by the growth portion external heating unit 36.

  Here, the pyrolytic boron nitride of the present invention can be suitably used as a part or all of the material in the raw material reaction tube 38 in the above apparatus. For example, in a growth apparatus of an aluminum nitride single crystal using aluminum chloride gas as a Group III source gas, if a commonly used quartz is used as a member in the growth apparatus, the quartz deteriorates when the susceptor is heated to a high temperature Since the quartz is deteriorated when the quartz and the aluminum monochloride gas come in contact with each other, the susceptor 32 and the members around the susceptor 32 which are high in temperature, and the raw material reaction tube 38 which easily contacts the aluminum monochloride gas are pyrolyzed. It is preferable to use lytic boron.

The above-mentioned crystal growth apparatus according to the present invention, as described above, has few sites to which foreign matter is likely to adhere, so that foreign matter can be prevented from flying and adhering to the crystal during growth, producing crystals with very few polycrystalline grains. can do. Therefore, the crystal growth apparatus of the present invention can be suitably used as a growth apparatus for various crystals. In particular, deposition of foreign matter tends to occur when vapor phase growth is performed under high temperature, so it is particularly suitable for crystal growth of aluminum-based Group III nitride single crystals including aluminum such as aluminum nitride single crystal and aluminum gallium nitride. It can be used.

  Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples. In addition, regarding the analysis of the pBN member surface, the 10 mm square pBN board | plate material manufactured by the method similar to the pBN member used in a crystallization apparatus was analyzed.

Morphology of the surface of pBN member, elemental composition, Raman spectrum, area ratio of site having peak at Raman shift 2800-3000 cm ^-1 to member surface area, and polycrystalline grain of aluminum nitride single crystal grown by crystal device using pBN member The number of was measured by the following method.

(Form of pBN member surface)
Nomarski differential interference microscope (Nikon LV150) was used. After focusing on a smooth region on the surface of the pBN member, the apex of the convex portion was focused, and the stage working distance at that time was taken as the height of the convex portion.

(Element composition of pBN member surface)
A scanning electron microscope (S-3400N manufactured by Hitachi High-Technologies Corporation) equipped with energy dispersive elemental analysis (EDS) was used. The analysis point was irradiated with an electron beam at an acceleration voltage of 15 kV and a probe current of 60 μA, and the collection of the energy dispersive element spectrum was performed for an integration time of 30 seconds.

(Raman spectrum of pBN member surface)
A microscopic laser Raman spectrophotometer (NRD-7100 manufactured by JASCO Corporation) was used. A laser with a wavelength of 532 nm was used as an excitation laser, and a slit with a diameter of 25 μm and a grating of 600 / mm were used. The excitation laser output was set to 10.8 mW, and a measurement spot was focused to a diameter of about 1 μm using a 100 × objective lens. The silicon substrate was irradiated with a laser with an exposure time of 0.5 seconds and integration number of 2 times, and the wave number was calibrated by Raman shift 520.5 cm ⁻¹ of the silicon substrate. Next, the measurement spot is set to be condensed to a diameter of about 4 μm using a 20 × objective lens, the exposure time is 30 seconds, and the number of integrations is two. It was measured. The measurement wave number range was 100 to 4000 cm ⁻¹ .

(Area ratio of the site having a peak at Raman shift 2800 to 3000 cm ^-1 to the surface area of the pBN member)
A range of 0.5 mm × 0.5 mm was measured in a grid shape at 4 μm intervals by the same method as the above-mentioned measurement method of Raman shift, and Raman spectra of all 15876 points were obtained. Furthermore, the same measurement was performed at any five points of the pBN member to obtain a total of 79380 Raman spectra. For all resulting Raman spectra to calculate the area of the _{E 2 g} peak of BN to 1220～1520Cm ^-1 as an end of the baseline (area 1), a 2750～3050Cm ^-1 as an end of the baseline The area (area 2) of the unique peak which exists in the Raman shift 2800-3000 cm < ^-1 > which the said site | part has was computed. The value of the ratio of area 2 to area 1 (area 2 / area 1) was calculated. Calculate the ratio of the number of measurement points whose ratio value is 0.03 or more to the number of all measurement points, and use this as the area ratio of the site having a peak at the Raman shift of 2800 to 3000 cm ^-1 to the surface area of the pBN member did.

(Number of polycrystalline grains of aluminum nitride single crystal)
A Nomarski differential interference microscope (Nikon LV150) was used. The aluminum nitride single crystal surface was observed at an observation magnification of 50 times to 1000 times. The number of indeterminate convex portions exposed on the surface of the single crystal was counted as the number of polycrystalline grains. In addition, it was confirmed by the following microscopic laser Raman spectroscopic analysis that the indeterminate convex portion is polycrystalline. The micro Raman spectroscopy was performed under the same conditions as the micro laser Raman spectroscopy of the surface of the pBN member. In the case of an aluminum nitride single crystal having a c-plane surface, a single peak derived from E ₂ ^H appears near a Raman shift of 657 cm ⁻¹ , but if it is polycrystalline, it is added to the peak near the above Raman shift 657 cm ⁻¹ , a peak of _E 1 (tO) from around 671cm ^-1, _a 1 (tO) peaks from around 611cm-1 is known to be expressed. From the fact that peaks were observed in the above-mentioned three Raman shifts when the laser was irradiated while focusing on the top of the indeterminate convex portion, it was found that the convex portion is polycrystalline.

Comparative Example 1
(Surface analysis of pBN members)
A 10 mm long, 10 mm wide, and 1 mm thick pBN sheet was produced by a known production method. When the surface morphology of the plate material was observed, there were sites that were convex compared to the other areas. The height of the site was 5 μm. The surface elemental composition of the site was B: 45.8 atom%, N: 50.5 atom%, O: 3.4 atom%. The other smooth regions were B: 46.5 atom% and N: 53.5 atom%. Moreover, the peak of this site was present at 1367 cm ⁻¹ and 2900 cm ⁻¹ . The other smooth region peak was present only at 1367 cm ⁻¹ . Among the measurement points, the maximum value of the ratio of the peak area of Raman shift 2800 to 3000 cm ^{−1 to} the peak area of E _{2 g} was 0.13. The area ratio of the site having a peak at a Raman shift of 2800 to 3000 cm ⁻¹ to the surface area of the pBN member was 0.092.

(Growth of aluminum nitride single crystal using a vapor phase growth apparatus using pBN members)
The raw material reaction tube 38 made of pBN used in the vapor phase growth apparatus 100 shown in FIG. 1 was manufactured by the same manufacturing method as that of the pBN plate material. A raw material portion reaction tube 38 filled with Al pellets (purity 99.9999%) as the group III metal 40 was attached to the reaction tube 10. In order to remove the moisture in the vapor phase growth apparatus 100, it was calcined by the following method. Electric power is applied to the resistance heating electric furnace which is the raw material part external heating means 35 so that the raw material part reaction pipe 38 becomes 400 ° C. while supplying the carrier gas from each gas supply pipe, while the growth part 31 side is local Power was applied to the high frequency heating coil as the heating means 37 to heat the susceptor 32 to 1500 ° C. After holding for 30 minutes while reaching the set temperature, it was cooled to room temperature.

  Thereafter, the aluminum nitride single crystal base substrate 20 is placed on the susceptor 32, and the raw material portion reaction tube 38 is heated to 400 ° C. with the susceptor 32 and the base in a state where carrier gas is circulated from each gas supply tube in the vapor phase growth apparatus 100. The substrate 20 was heated to 1500.degree. After reaching the set temperature, hydrogen chloride gas is supplied to the raw material reaction tube 38, and the hydrogen chloride gas supplied through the additional halogen-based gas introduction tube 41 is mixed with the aluminum chloride gas generated in the raw material reaction tube 38. A mixed gas of aluminum chloride gas and hydrogen chloride gas was supplied onto the base substrate 20 through the group III source gas supply nozzle 42. Furthermore, ammonia gas and hydrogen chloride gas were supplied through the nitrogen source gas supply nozzle 45 to start the growth of aluminum nitride single crystal on the base substrate 20. The growth rate was 55 μm / h at the center position of the base substrate for 6 hours to grow an aluminum nitride single crystal with a thickness of 330 μm. After a predetermined time elapsed, the supply of hydrogen chloride gas and ammonia gas was stopped, and the system was cooled to room temperature, and the aluminum nitride single crystal laminate was taken out. Since aluminum nitride was deposited on the members in the vicinity of the installation location of the base substrate 20 of the growth portion 31 due to the growth of the aluminum nitride single crystal, the members were replaced with members having no precipitate.

  Thereafter, the above-described blanking, growth, and member replacement of the growth portion were performed again, and a total of five growths of the aluminum nitride single crystal were performed.

(Analysis of aluminum nitride single crystal laminate)
The polycrystalline grains of the obtained five aluminum nitride single crystal laminates were calculated, and the number was 0, 3, 3, 4, 7 in the order of growth.

Example 1
A mixture of about 98% concentrated sulfuric acid and about 30% aqueous hydrogen peroxide mixed in a ratio of 4: 1 was heated to 100 ° C. The pBN plate produced in the same manner as in Comparative Example 1 was immersed in the mixture and held for 10 minutes. Thereafter, it was rinsed with ultrapure water for 5 minutes and dried at room temperature to produce a pBN plate material. When the surface of the plate was analyzed, no convex portion was observed. In the Raman analysis, the maximum value of the ratio of the peak area of the Raman shift 2800 to 3000 cm ^{−1 to} the peak area of E _2g was 0.031 out of all the measurement points. The area ratio of the site having a peak at a Raman shift of 2800 to 3000 cm ⁻¹ with respect to the surface area of the pBN member was 0.0008.

  The raw material reaction tube 38 made of pBN used in the vapor phase growth apparatus shown in FIG. 1 is manufactured by the same manufacturing method as the above pBN plate material, and the aluminum nitride single crystal laminate is manufactured by the same method as Comparative Example 1. Made a piece. The polycrystalline grains of the obtained five aluminum nitride single crystal laminates were calculated. As a result, they were 0, 0, 0, 1, 1 and 1 in the order of growth.

100: Vapor phase growth system (HVPE system)
10: reaction tube 20: base substrate 30: raw material part 31: growth part 32: susceptor 33: extrusion carrier gas introduction pipe 34: exhaust part 35: raw material part external heating means 36: growth part external heating means 37: local heating means 38 : Raw material part reaction tube 39: Halogen based gas introduction tube for raw material generation 40: Group III metal 41: Additional halogen based gas introduction tube 42: Group III source gas supply nozzle 43: Nitrogen source gas introduction tube 44: Additional halogen based gas ( Nitrogen source gas) Introduction pipe 45: Nitrogen source gas supply nozzle

Claims (3)

Pyrolytic boron nitride produced by a thermal decomposition CVD method, wherein
The pyrolytic boron nitride whose ratio of the area of the site | part which has a peak in the Raman shift 2800-3000 cm < ^-1 > with respect to the total surface area of said pyrolytic boron nitride is 0.01 or less.   2. The method for producing pyrolytic boron nitride according to claim 1, wherein the surface of boron nitride produced by the thermal decomposition CVD method is brought into contact with a mixed solution of sulfuric acid and hydrogen peroxide solution.   A crystal growth apparatus comprising pyrolytic boron nitride according to claim 1.

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