JP2011190131A - Method for manufacturing aluminum nitride single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a large-sized, good-crystallization aluminum nitride single crystal. <P>SOLUTION: In the manufacturing method of an aluminum nitride single crystal, a nitrogen gas is circulated in the presence of a raw material gas-generating substrate to generate aluminum gas or an aluminum oxide gas, carbon molded articles, and seed crystals for depositing aluminum nitride single crystals; and when the aluminum nitride single crystals are grown in a heating environment, the carbon molded articles are arranged spaced with intervals nearly parallel to the nitrogen gas circulating direction on the raw material-generating substrate, the raw material gas-generating substrate is arranged on the upstream side in the nitrogen gas circulating direction, and the seed crystals for depositing aluminum nitride single crystals are arranged on the downstream side to make the aluminum nitride single crystals grow on the seed crystals. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a novel method for producing an aluminum nitride single crystal having good crystallinity.

  Aluminum nitride is used as a filler, a substrate for electronic / electrical parts, and a heat dissipation member because it is a material with high mechanical strength and excellent heat dissipation performance. In particular, an AlN single crystal constitutes a light emitting device such as a light emitting diode (LED) or a laser diode (LD) that emits short-wavelength light in the blue visible region to the ultraviolet region from the viewpoint of lattice matching and ultraviolet light transmittance. It is attracting attention as a substrate material.

  Currently, aluminum nitride single crystals are thin films by vapor phase growth methods such as metal organic vapor phase epitaxy (MOVPE), hydride vapor phase epitaxy (HVPE), chemical transport, flux, sublimation recrystallization, etc. Single crystals and bulk single crystals are manufactured. In particular, the chemical transport method and the sublimation recrystallization method have yielded various investigations because single crystals having different shapes such as plate crystals and needle crystals can be obtained.

  Specifically, by using alumina and other metal oxides as raw materials and heating them in a nitrogen atmosphere in the presence of carbon at a temperature of 1650 ° C. or higher and 2200 ° C. or lower, needle-shaped and plate-shaped aluminum nitride single crystals are obtained. A manufacturing method (see JP 2005-132699 A: Patent Document 1) has been proposed. However, in the method described in Patent Document 1, since a metal oxide other than alumina is used in combination, there is room for improvement in that the resulting aluminum nitride single crystal may contain impurities. In addition, it is difficult to control the deposition location of aluminum nitride, and it is difficult to selectively deposit aluminum nitride only in a necessary portion. Furthermore, in the method of Patent Document 1, a raw material such as alumina is housed in a carbon crucible and heated in a nitrogen atmosphere with the lid covered. Since the flow of nitrogen is hindered by the lid, the production efficiency of aluminum nitride is considered insufficient.

  Patent Documents 2 to 4 propose improved techniques related to a method for producing an aluminum nitride single crystal by a sublimation method. According to the sublimation method, although it is possible to produce a high-quality aluminum nitride single crystal, a high-purity aluminum nitride powder or a polycrystal is produced and further heated to a sublimation temperature to grow a single crystal. Production efficiency is low.

JP 2005-132699 A JP 2006-27988 A JP 2007-214547 A JP 2008-13390 A

  The present invention has been made in view of the prior art as described above, and an object of the present invention is to provide a method for efficiently and simply producing an aluminum nitride single crystal having good crystallinity.

  The aluminum nitride polycrystalline powder that is currently widely used as aluminum nitride is obtained by heating alumina powder and carbon powder in a nitrogen atmosphere. In this case, since the raw material gas generated from alumina is immediately reduced and nitrided by the reducing gas generated from the adjacent carbon powder, it is considered that a large single crystal cannot be obtained and a polycrystalline powder is generated. From this consideration, the present inventors have found that the aluminum nitride single crystal may be precipitated by bringing the raw material gas generated from alumina or the like into contact with the reducing gas after maintaining the floating state to some extent. However, when the raw material gas flow becomes turbulent, the frequency of contact with the carbon source increases, and the possibility that aluminum nitride single crystals precipitate in the form of particles or needles in the vicinity of the carbon source increases, and a film-like single crystal is obtained. It is not easy.

  Therefore, as a result of further investigation, the flow environment of the raw material gas and the reducing gas is kept constant, the floating state of the raw material gas and the reducing gas is maintained, and the gas is transferred to the desired precipitation portion, so that the desired precipitation portion is obtained. The inventors have found that aluminum nitride is efficiently and uniformly deposited and a single crystal having good properties can be obtained. The present invention completed based on the above idea includes the following matters as a gist.

(1) a source gas generating substrate that generates aluminum gas or aluminum oxide gas;
At least two carbon compacts;
A method for producing an aluminum nitride single crystal in which nitrogen gas is circulated in the presence of a seed crystal for precipitation of an aluminum nitride single crystal to grow the aluminum nitride single crystal in a heating environment,
On the substrate for generating the source gas, the carbon molded body is arranged with an interval substantially parallel to the nitrogen gas flow direction,
A source gas generating substrate is disposed on the upstream side with respect to the nitrogen gas flow direction, a seed crystal for aluminum nitride single crystal precipitation is disposed on the downstream side, and an aluminum nitride single crystal is grown on the seed crystal. Crystal production method.

(2) A seed crystal for aluminum nitride single crystal precipitation is placed on a non-carbon substrate,
(1) The production method according to (1), wherein the non-carbon substrate is disposed so that an end face on the upstream side with respect to a nitrogen gas flow direction is positioned below the source gas generating substrate.

(3) The manufacturing method as described in (1) which arrange | positions a carbon molded object on the raw material gas generation | occurrence | production board | substrate so that the space | interval of a carbon molded object may be 0.5-10 mm.

(4) The production method according to (1), wherein a seed crystal for depositing an aluminum nitride single crystal is disposed in a range of 1 to 50 mm from an end face on the downstream side with respect to a nitrogen gas flow direction of the carbon molded body.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing an aluminum nitride single crystal with favorable crystallinity efficiently and simply is provided. In particular, according to the method of the present invention, since aluminum nitride precipitates uniformly, a seed crystal is grown, and a large grain aluminum nitride single crystal is obtained.

FIG. 2 is a schematic cross-sectional view showing an example of a single crystal production apparatus that can be suitably used in a method for producing an aluminum nitride single crystal, and a positional relationship between a source gas generating substrate, a carbon molded body, and a seed crystal for aluminum nitride single crystal precipitation. . It is a schematic plan view which shows an example of the positional relationship of the raw material gas generation | occurrence | production board | substrate, a carbon molded object, and the seed crystal for aluminum nitride single crystal precipitation.

  Hereinafter, the present invention, including its best mode, will be described in more detail with reference to the drawings.

  In the method for producing an aluminum nitride single crystal according to the present invention, first, a raw material gas generating substrate 5 for generating aluminum gas or aluminum oxide gas, at least two carbon molded bodies 6 and nitriding are provided in the single crystal production apparatus 1. The seed crystal 7 for aluminum single crystal precipitation is arranged so as to satisfy a predetermined positional relationship.

(Aluminum nitride single crystal manufacturing equipment)
FIG. 1 shows an example of a schematic cross-sectional view of a single crystal production apparatus that can be suitably used in the method for producing an aluminum nitride single crystal of the present invention. Hereinafter, the present invention will be described in detail with reference to FIG. 1, but the present invention is not limited to the following embodiments.

  The single crystal production apparatus 1 includes a reaction vessel 4 having a nitrogen gas supply port 2 for supplying nitrogen gas on the upstream side and a discharge port 3 for discharging gas in the system on the downstream side. In the reaction vessel 4, a source gas generating substrate 5, a carbon molded body 6, and a seed crystal 7 for depositing an aluminum nitride single crystal are disposed so as to satisfy a predetermined positional relationship. The reaction vessel 4 can be heated by the heater 9.

  In the single crystal manufacturing apparatus, each member, for example, the reaction vessel 4, the nitrogen gas supply port 2, and the discharge port 3 can naturally withstand the temperature at which the aluminum nitride single crystal is grown. It shall be composed of materials.

  In the present invention, an aluminum nitride single crystal can be grown using the single crystal manufacturing apparatus as described above, and the method will be described in more detail below.

(Reaction vessel)
In the present invention, as described above, the reaction vessel 4 used is composed of a material that can sufficiently withstand the temperature at which an aluminum nitride single crystal is grown, specifically, a temperature of 1500 ° C. or higher and 2400 ° C. or lower. . Specific examples of the material include aluminum nitride, boron nitride sintered body, and carbon. Among these, in consideration of the purity of the aluminum nitride single crystal to be produced, the reaction vessel 4 is preferably made of an aluminum nitride sintered body. Moreover, it is preferable to use what does not contain a sintering auxiliary agent among aluminum nitride sintered compacts.

  The shape and size of the reaction vessel 4 are not particularly limited as long as they can be industrially manufactured. Among these, the cylindrical shape is preferable because the reaction vessel 4 is easy to manufacture and the nitrogen gas supplied when growing the aluminum nitride single crystal is easily supplied uniformly into the reaction vessel 4.

(Substrate for generating source gas)
The source gas generating substrate 5 is made of a material that generates source aluminum gas that reacts with nitrogen to generate aluminum nitride. The raw material aluminum gas in the present invention is an aluminum gas or an aluminum oxide gas. Metal aluminum is used to generate the aluminum gas, or aluminum oxide (alumina, sapphire) is used to generate the aluminum oxide gas. ) Is used.

  The aluminum oxide is not particularly limited as long as aluminum is oxidized, and commercially available aluminum oxide, sapphire, and aluminum nitride oxidized can be used. About what oxidized aluminum nitride, what was oxidized beforehand outside the reaction container can be used, and what oxidized aluminum nitride inside the reaction container can be used.

Among such aluminum oxides, in order to further simplify the process and increase the yield of the obtained aluminum nitride single crystal, the aluminum nitride is not oxidized, but normal aluminum oxide or sapphire (hereinafter referred to as nitride) It is preferable to use this normal aluminum oxide, or sapphire may be Al ₂ O ₃ ) instead of oxidized aluminum.

In the present invention, when aluminum oxide (Al ₂ O ₃ ) is used, it is not particularly limited, but in view of the purity of the obtained aluminum nitride single crystal, it is preferable to use a high-purity one. . However it is not intended to exclude impurities inevitably mixed in the production of commercially available aluminum oxide (Al 2 _{O 3),} as the purity of the aluminum oxide (Al 2 _{O 3),} is 99% or more It is preferable that it is 99.9% or more.

  The shape of the source gas generating substrate is not particularly limited, but it is particularly preferable to use an aluminum oxide molded body, specifically, an alumina plate.

  Aluminum oxides satisfying such conditions are commercially available. As an example, aluminum oxide Wako special grades manufactured by Wako Pure Chemical Industries, Ltd., aluminum oxides ALO01PB, ALO02PB manufactured by Kojundo Chemical Laboratory Co., Ltd. , ALO03PB, ALO16PB, ALO13PB, ALO14PB, ALO11PB, ALO12PB can be used. Further, alumina A-479, A-480, A601 manufactured by Kyocera Corporation, and single crystal sapphire manufactured by Kyocera can also be used. In addition, as the metal aluminum, for example, a commercially available AlE series plate-like or foil-like product having a purity of 99% or more manufactured by Kojundo Chemical Laboratory Co., Ltd. can be used.

(Carbon molded body)
In the present invention, the carbon molded body 6 is used as a reducing agent when reducing and nitriding the source gas. The form of the carbon molded body 6 is not particularly limited as long as it is tangible, but is preferably columnar or block-shaped. Therefore, preferable carbon molded bodies include, for example, columnar bodies and block bodies obtained by molding carbon powder such as carbon black with a small amount of binder resin, and columnar bodies and block bodies formed by cutting out graphite or the like.

  When carbon powder is used as a reducing agent in the production method of the present invention, carbon gasification and reductive nitridation reactions occur rapidly, and carbon disappears from the reaction system before the reaction sufficiently proceeds, or aluminum nitride is generated. It becomes rapid and a good single crystal cannot be obtained.

However, when a carbon molded body is used as the reducing agent, carbon gasification is limited to the surface of the molded body, so that rapid gasification of carbon is suppressed. As a result, it is considered that the amount of reducing gas (carbon monoxide gas or the like) generated from the carbon molded body becomes appropriate, the reductive nitridation reaction is moderately suppressed, and a good single crystal can be obtained. To suppress rapid gasification of such carbon, carbon molded body used in the present invention preferably has effective surface area per its weight is less than 0.5 m 2 / ^g, further 0.25 m ² / g or less is preferable, and 0.025 m ² / g or less is particularly preferable. In addition, even if the carbon molded body is too large, there is a possibility of causing problems such as non-precipitation of aluminum nitride due to an increase in reducing power. Therefore, the effective surface area of the carbon molded body is 1.7 × 10 ⁻⁴ m ² / g. Preferably, it is preferably 2.0 × 10 ⁻⁴ m ² / g or more, more preferably 2.7 × 10 ⁻⁴ m ² / g or more. Here, the effective surface area is a surface area that does not consider pores and the like. For example, in the case of a rectangular parallelepiped, it means the area per unit weight of the upper and lower surfaces and the four side surface portions.

(Seed crystal for aluminum nitride single crystal precipitation)
In the present invention, a seed crystal 7 for aluminum nitride single crystal precipitation is disposed downstream of the carbon molded body, and aluminum nitride is precipitated on the single crystal 7 to obtain an aluminum nitride single crystal. The seed crystal 7 has a structure in which an aluminum nitride single crystal can be precipitated, and is not particularly limited as long as the seed crystal 7 is a material having resistance under the aluminum nitride precipitation conditions. Preferably, aluminum nitride (AlN) single crystal, silicon carbide (SiC) single crystal, gallium nitride single crystal, sapphire, aluminum nitride polycrystal, silicon carbide polycrystal, alumina, or the like is used. Among these, an aluminum nitride single crystal is particularly preferably used. In the production method of the present invention, by using an aluminum nitride single crystal as a seed crystal, aluminum nitride is uniformly deposited on the seed crystal, and a large aluminum nitride single crystal is obtained. By cutting this large grain aluminum nitride single crystal into a desired size and shape, it is possible to obtain an aluminum nitride single crystal formed body applicable to various applications.

  When using industrially produced silicon carbide single crystal, gallium nitride single crystal, or sapphire as a seed crystal, a mirror-polished crystal substrate can be used, and the underlying mirror surface is maintained after aluminum nitride deposition. In this state, an aluminum nitride single crystal can be precipitated. However, when such a dissimilar material is used as a substrate (seed crystal), there is a difference in lattice constant and thermal expansion coefficient between the seed crystal and aluminum nitride deposited on the seed crystal. May occur.

(Non-carbon substrate)
The seed crystal 7 for aluminum nitride single crystal precipitation is not particularly limited as long as the seed crystal 7 is disposed on the downstream side of the carbon molded body 6, but is preferably placed on the non-carbon substrate 8, It arrange | positions in the downstream of the carbon molded object 6. FIG. As the non-carbon substrate 8, various substrates made of a material that does not generate a reducing gas in a heating environment and having heat resistance under aluminum nitride deposition conditions are used. As this substrate, for example, aluminum nitride polycrystal, silicon carbide single crystal, sapphire, aluminum nitride polycrystal, silicon carbide polycrystal, silicon nitride polycrystal, tungsten, molybdenum or the like is used.

  The shape of the non-carbon substrate 8 may be a plate shape, and the thickness thereof is preferably about the same as or less than that of the source gas generating substrate 5. Moreover, the surface of the non-carbon substrate 8 may be inclined as shown in FIG.

(Positional relationship between the source gas generating substrate 5, the carbon molded body 6 and the seed crystal 7)
In the present invention, aluminum nitride is generated in a state in which the source gas generating substrate 5, the carbon molded body 6, and the seed crystal 7 for aluminum nitride single crystal precipitation are arranged in the reaction vessel 4 so as to satisfy a predetermined positional relationship. Perform (see FIG. 1 and FIG. 2).

  Specifically, as shown in a cross-sectional view in FIG. 1 and a plan view in FIG. 2, the carbon molded body 6 is placed on the source gas generating substrate 5 with a space approximately parallel to the nitrogen gas flow direction. The raw material gas generating substrate 5 is arranged on the upstream side with respect to the nitrogen gas flow direction, and the seed crystal 7 for aluminum nitride single crystal precipitation is arranged on the downstream side.

  As described above, the nitrogen gas is supplied from the nitrogen gas supply port 2, flows through the reaction vessel 4, and is discharged from the discharge port 3. Therefore, in the reaction vessel 4, the nitrogen gas supply port 2 side is called “upstream” and the discharge port 3 side is called “downstream”. Nitrogen gas flows from the upstream side to the downstream side. Since the source gas generating substrate 5, the carbon molded body 6, and the single crystal 7 are disposed in the reaction vessel 4, the gas flow state in the vessel 4 is not necessarily uniform, The “gas flow direction” is defined by a straight line connecting the nitrogen gas supply port 2 and the discharge port 3 and is substantially parallel to the axis of the cylindrical reaction vessel 4.

  As shown in FIG. 2, the plurality of carbon molded bodies 6 are arranged on the raw material gas generation substrate 5 at intervals substantially in parallel. Here, the number of the carbon molded bodies 6 should just be two or more, and it sets suitably considering the capacity | capacitance of the reaction container 4 and the space | interval of the carbon molded bodies 6 mentioned later. Further, “substantially parallel” means that the angle θ formed by the nitrogen gas flow direction (A-A line in the figure) and the central axis of the carbon molded body 6 is ± 25 ° or less, preferably ± 22 ° or less, More preferably, it means ± 18 ° or less. By arranging the carbon molded body 6 as described above, the flow of nitrogen gas, raw material gas and reducing gas is rectified, the disorderly generation of aluminum nitride is suppressed, and the aluminum nitride single crystal precipitation disposed downstream is performed. The aluminum nitride single crystal is uniformly deposited on the seed crystal 7 for use.

  In addition, in FIG. 2, although the carbon molded object 6 showed the example of a columnar body, you may arrange | position a some block-shaped carbon molded object in series along a nitrogen gas distribution direction.

  The interval between the carbon molded bodies 6 is preferably 0.5 to 10 mm, more preferably 0.5 to 8 mm, and particularly preferably 0.5 to 5 mm. If the interval between the carbon molded bodies 6 is too narrow, the flow of the source gas generated from the source gas generating substrate 5 may be hindered. If it is too wide, it is intermediate between adjacent carbon molded bodies. This is not preferable because precipitation of aluminum nitride occurs at the position and the source gas is not easily transported to the seed crystal. When the interval between the carbon molded bodies exceeds 10 mm, aluminum nitride is precipitated at the intermediate point, and the growth of the target seed crystal may be hindered. The cause of this is not necessarily clear, but when the distance between the carbon molded bodies is too wide, the amount of reducing gas generated from the carbon molded bodies decreases, and the reducing gas stays at an intermediate point between the carbon molded bodies. This is presumably because aluminum nitride is generated by the reductive nitridation reaction in this region.

  Moreover, the seed crystal 7 for aluminum nitride single crystal precipitation should just be arrange | positioned downstream. Preferably, the seed crystal is arranged on a downstream extension line of a straight line starting from a midpoint of a straight line connecting downstream end portions of adjacent carbon molded bodies and parallel to the nitrogen gas flow direction. Further, when the seed crystal 7 is placed on the non-carbon substrate 8 and disposed in the reaction vessel 4, the upstream end face 8 </ b> A of the non-carbon substrate 8 with respect to the nitrogen gas flow direction is provided. It is preferable to dispose the material gas generating substrate 5 so as to be positioned below the material gas generating substrate 5. That is, it is preferable to arrange the upstream end face 8 </ b> A of the non-carbon substrate 8 so as to be embedded in the lower part of the source gas generating substrate 5. By arranging in this way, the phenomenon that the aluminum nitride is irregularly deposited on the upstream end face 8A of the carbon substrate 8 can be prevented, the aluminum nitride can be uniformly deposited on the seed crystal 7, and the crystallinity is large and crystalline. A good aluminum nitride single crystal can be obtained.

  Although not theoretically limited at all, the reason why irregular precipitation of aluminum nitride can be prevented by taking the above arrangement is considered as follows.

  When the upstream end face 8A of the non-carbon substrate 8 is exposed away from the source gas generating substrate 5, the reducing gas generated from the source gas generating substrate 5 and the carbon molded body 6 is reduced. Gas and nitrogen gas may collide with the upstream end face 8A of the non-carbon substrate 8 and become turbulent. As a result, aluminum nitride is irregularly deposited in the vicinity of the upstream end face 8A of the non-carbon substrate 8, and it is difficult to obtain a good single crystal.

  On the other hand, as described above, the upstream end surface 8A of the non-carbon substrate 8 is arranged so as to be embedded in the lower portion of the source gas generating substrate 5, thereby smoothly flowing the source gas, nitrogen gas and reducing gas. Thus, it is considered that the aluminum nitride is suppressed from irregular precipitation, the aluminum nitride is uniformly deposited on the seed crystal, and a good single crystal is obtained.

  In addition, from the end face 6A on the downstream side with respect to the nitrogen gas flow direction of the carbon molded body 6, preferably 1 to 50 mm, more preferably 1 to 30 mm, and particularly preferably 1 to 20 mm, aluminum nitride single crystal precipitation It is preferable to arrange a seed crystal 7 for use. By setting the distance between the carbon molded body 6 and the seed crystal 7 as described above, the source gas and the reducing gas are uniformly deposited on the seed crystal 7 after maintaining a certain floating state. Crystals are easily obtained.

(Growth method of aluminum nitride single crystal)
In the present invention, nitrogen gas is supplied from the nitrogen gas supply port 2 in a state in which the source gas generating substrate 5, the carbon molded body 6, and the seed crystal 7 for single crystal precipitation of aluminum nitride are arranged so as to satisfy a specific positional relationship. The aluminum nitride single crystal is grown under a heating environment.

  Nitrogen gas may be pure nitrogen, or may be diluted with an inert gas other than nitrogen and distributed. As the inert gas other than nitrogen, for example, an inert gas such as argon, helium, neon, krypton, or xenon is used. The flow rate of the nitrogen gas is not particularly limited as long as aluminum nitride is generated on the seed crystal 7, and varies depending on various thermodynamic conditions such as the heat treatment temperature. However, in order to efficiently produce an aluminum nitride single crystal without generating disordered turbulent flow in the reaction vessel, the amount is preferably 0.1 cc / min to 100 L / min, more preferably 1 cc / min in terms of 23 ° C. It is desirable to circulate nitrogen gas in an amount of ˜50 L / min, more preferably 30 cc / min to 30 L / min, particularly preferably 50 cc / min to 20 L / min.

  In the present invention, the temperature in the reaction vessel is not particularly limited as long as the source gas is generated from the source gas generating substrate and the source gas is reduced and nitrided to produce aluminum nitride on the seed crystal 7. Also, it depends on various thermodynamic conditions such as nitrogen partial pressure existing in the reaction system. The source gas generating substrate 5, the carbon molded body 6 and the seed crystal 7 are close to each other, and there is substantially no temperature difference among them.

  The temperature in the reaction vessel is preferably 1500 ° C. or higher and 2400 ° C. or lower. When the temperature is less than 1500 ° C., it is not preferable because the aluminum nitride single crystal is difficult to grow. On the other hand, when the temperature exceeds 2400 ° C., the temperature is too high, which is not suitable for industrial production. Considering the industrial production of the aluminum nitride single crystal, the temperature in the reaction vessel is preferably 1700 ° C. or higher and 2200 ° C. or lower, more preferably 1750 ° C. or higher and lower than 2150 ° C., particularly preferably 1750 ° C. or higher and 2100 ° C. or lower. .

  In the present invention, by controlling the temperature in the reaction vessel within the above temperature range, the crystallinity of the resulting aluminum nitride single crystal is improved as the temperature rises. Moreover, the expansion of crystal grains is observed. Furthermore, the yield is increased.

(Other conditions)
In the present invention, an aluminum nitride single crystal can be produced by depositing aluminum nitride on the seed crystal 7 for single crystal aluminum nitride precipitation under the above conditions and growing the single crystal.

  The reaction time (time for growing the aluminum nitride single crystal) is not particularly limited, and may be appropriately determined according to the desired shape and yield of the aluminum nitride single crystal. The longer the reaction time, the larger the aluminum nitride single crystal is obtained. However, considering industrial production, the reaction time is preferably 1 hour or more and 200 hours or less.

  In addition, this reaction time is time measured from the time when all the conditions were prepared. That is, it is the time after all the conditions of the temperature in the reaction vessel and the partial pressure of the nitrogen gas satisfy the set conditions. Therefore, when the temperature in the reaction vessel is set to the set temperature while supplying nitrogen gas into the reaction vessel, the time after reaching the set temperature is the reaction time. In addition, when the nitrogen gas is supplied to the reaction vessel after the inside of the reaction vessel is set to the set temperature, the time after the nitrogen gas is supplied becomes the reaction time.

  After the aluminum nitride single crystal is grown under such conditions, the temperature of the reaction vessel is lowered to near room temperature, and the produced aluminum nitride single crystal is taken out of the reaction vessel to produce the aluminum nitride single crystal. it can.

(Aluminum nitride single crystal)
According to the present invention, a large grain aluminum nitride single crystal can be produced. The obtained aluminum nitride single crystal is cut into an appropriate size as desired, and can be used in various applications, for example, as a base substrate of a light emitting element.

  Hereinafter, the present invention will be described in more detail in the following examples, but the present invention is not limited to the following examples.

[Evaluation methods]
<Evaluation of crystallinity>
The full width at half maximum of the rocking curve was calculated with an X-ray diffractometer (manufactured by Bruker AXS).

Example 1
An experiment was conducted using the single crystal manufacturing apparatus 1 having the configuration shown in FIG. The reaction vessel 4 was a cylindrical one. An alumina plate (Al ₂ O ₃ ) (A479, purity 99%) 35 mm × 50 mm × 1 mm (t) manufactured by Kyocera Corporation was charged as an upstream side in the reaction vessel 4 (aluminum oxide 5). The charging position was directly below the nitrogen supply port 2. Three prismatic carbon molded bodies 6 cut into 5 mm (vertical) × 5 m (horizontal) × 50 mm (length) were placed on top of the aluminum oxide 5. The interval between the carbon molded bodies was set to 1 mm, and the end portions of the aluminum oxide and the end portions of the carbon molded body were aligned so that they were all parallel (θ = 0 °). Next, a 30 mm × 30 mm × 1 mm (t) aluminum nitride polycrystal 8 is placed as a non-carbon substrate at a location 1 mm away from the end of the aluminum oxide 5, and an aluminum nitride precipitation seed crystal 7 is formed on the top. The resulting aluminum nitride single crystal fragments were placed on the downstream extension of a straight line parallel to the nitrogen gas flow direction, starting from the midpoint of the straight line connecting the downstream ends of adjacent carbon molded bodies. One seed crystal (two in total) was placed on the downstream extension line from the midpoint of each of the three carbon molded bodies. The weight of one seed crystal was 0.02 g, and the weight of the other seed crystal was 0.03 g. The distance between the carbon molded body and the seed crystal was 10 mm.

  The temperatures of the aluminum oxide 5, the carbon molded body 6 and the seed crystal 7 were set to 1950 ° C.

  Nitrogen gas was supplied from the nitrogen supply port 2 in an amount of 2 L / min.

  The holding time (reaction time) was set to 30 hours to precipitate aluminum nitride single crystals. After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. And after completion | finish of reaction, when the weight of the seed crystal was measured, the weight of the 0.02g seed crystal increased to 0.025g, and the 0.03g seed crystal increased to 0.037g.

  The obtained aluminum nitride crystal was evaluated with an X-ray diffractometer (manufactured by Bruker AXS). The full width at half maximum of the AlN (002) peak was 38 arcsec, which was confirmed to be an aluminum nitride single crystal.

Example 2
In Example 1, the reaction was performed in the same manner as in Example 1 except that the interval between the carbon molded bodies 6 was changed to 5 mm.

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. And when the weight of the seed crystal was measured, the weight of the 0.02 g seed crystal increased to 0.027 g, and the 0.03 g seed crystal increased to 0.035 g. The full width at half maximum of the AlN (002) peak was 42 arcsec, confirming the aluminum nitride single crystal.

Example 3
In Example 1, the reaction was performed in the same manner as in Example 1 except that the interval between the carbon molded bodies 6 was 10 mm.

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. And after completion | finish of reaction, when the weight of the seed crystal was measured, the weight of the 0.02g seed crystal increased to 0.024g, and the 0.03g seed crystal increased to 0.034g. The full width at half maximum of the AlN (002) peak was 40 arcsec, and it was confirmed to be an aluminum nitride single crystal.

Example 4
In Example 1, the reaction was performed in the same manner as in Example 1 except that the installation method of the carbon molded body 6 was changed to a shape in which the two outsides were opened by 10 ° with respect to the center.

After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. And after completion | finish of reaction, when the weight of the seed crystal was measured, the weight of the 0.02g seed crystal increased to 0.025g, and the 0.03g seed crystal increased to 0.037g. The full width at half maximum of the AlN (002) peak was 39 arcsec, which was confirmed to be an aluminum nitride single crystal.

Example 5
In Example 1, the reaction was carried out in the same manner as in Example 1 except that the installation method of the carbon molded body 6 was changed to a shape in which the two outer sides with respect to the center were opened 5 ° downstream.

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. And after completion | finish of reaction, when the weight of the seed crystal was measured, the weight of the 0.02g seed crystal increased to 0.024g, and the 0.03g seed crystal increased to 0.036g. The full width at half maximum of the AlN (002) peak was 42 arcsec, confirming the aluminum nitride single crystal.

Example 6
In Example 1, the reaction was performed in the same manner as in Example 1 except that the distance between the carbon molded body 6 and the seed crystal was 25 mm.

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. And after completion | finish of reaction, when the weight of the seed crystal was measured, the weight of the 0.02g seed crystal increased to 0.022g, and the 0.03g seed crystal increased to 0.033g. The full width at half maximum of the AlN (002) peak was 48 arcsec, which was confirmed to be an aluminum nitride single crystal.

Example 7
In Example 1, the reaction was performed in the same manner as in Example 1 except that the seed crystal was a silicon carbide single crystal wafer (φ1 inch, thickness 300 μm).

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. Furthermore, as a result of measuring the thickness of the film-like substance formed on the silicon carbide single crystal wafer using a scanning electron microscope, it was confirmed that the thickness was about 2 μm. X-ray diffraction measurement confirmed that the film-like substance was an aluminum nitride single crystal, and the full width at half maximum of the AlN (002) peak was 80 arcsec.

Example 8
In Example 1, the reaction was performed in the same manner as in Example 1 except that the seed crystal was a sapphire wafer (φ1 inch, thickness 300 μm).

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. Furthermore, as a result of measuring the thickness of the film-like substance formed on the sapphire wafer using a scanning electron microscope, it was confirmed that the thickness was about 1.7 μm. X-ray diffraction measurement confirmed that the film-like substance was a single crystal of aluminum nitride, and the full width at half maximum of the AlN (002) peak was 120 arcsec.

Comparative Example 1
In Example 1, the reaction was performed in the same manner as in Example 1 except that nitrogen was not supplied.

  After the reaction was completed, the inside of the reaction vessel was visually observed, and no precipitates were observed other than the seed crystals installed before the reaction. When the weight of the seed crystal was measured, no weight increase was observed in any of the seed crystals.

Comparative Example 2
In Example 1, the reaction was carried out in the same manner as in Example 1 except that the installation method of the carbon molded body 6 was changed to a shape in which the two outer sides with respect to the center were opened 60 ° downstream.

  After completion of the reaction, the inside of the reaction vessel was visually observed, and precipitates were observed at an intermediate position of the carbon molded body opened at 60 °. Further, when the weight of the seed crystal was measured, no weight increase was observed in any of the seed crystals.

Comparative Example 3
In Example 1, the reaction was performed in the same manner as in Example 1 except that the number of carbon molded bodies was changed to one.

  After completion of the reaction, the inside of the reaction vessel was visually observed, and precipitates were observed at points 12 mm away from each other in the vertical direction on both sides with respect to the length direction of the carbon molded body. Further, when the weight of the seed crystal was measured, no weight increase was observed in any of the seed crystals.

  From the above, it has been clarified that according to the production method of the present invention, an aluminum nitride single crystal having good crystallinity can be efficiently deposited on the seed crystal at the target precipitation part.

DESCRIPTION OF SYMBOLS 1 Single crystal manufacturing apparatus 2 Nitrogen supply port 3 Outlet 4 Reaction container 5 Substrate for source gas generation (aluminum oxide)
6 Carbon molded body 7 Seed crystal for aluminum nitride single crystal precipitation 8 Non-carbon substrate 9 Heater

Claims (4)

A source gas generating substrate for generating aluminum gas or aluminum oxide gas;
At least two carbon compacts;
A method for producing an aluminum nitride single crystal in which nitrogen gas is circulated in the presence of a seed crystal for precipitation of an aluminum nitride single crystal to grow the aluminum nitride single crystal in a heating environment,
On the substrate for generating the source gas, the carbon molded body is arranged with an interval substantially parallel to the nitrogen gas flow direction,
A source gas generating substrate is disposed on the upstream side with respect to the nitrogen gas flow direction, a seed crystal for aluminum nitride single crystal precipitation is disposed on the downstream side, and an aluminum nitride single crystal is grown on the seed crystal. Crystal production method. A seed crystal for precipitation of aluminum nitride single crystal is placed on a non-carbon substrate,
The manufacturing method according to claim 1, wherein the non-carbon substrate is disposed such that an upstream end surface with respect to a nitrogen gas flow direction is positioned below the source gas generating substrate.   The manufacturing method of Claim 1 which arrange | positions a carbon molded object on the raw material gas generation | occurrence | production board | substrate so that the space | interval of a carbon molded object may be 0.5-10 mm.   The manufacturing method of Claim 1 which arrange | positions the seed crystal for aluminum nitride single crystal precipitation in the range of 1-50 mm from the end surface of a carbon molded object downstream with respect to the nitrogen gas distribution direction.

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