JP2007145679A - Apparatus for and method of producing aluminum nitride single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing an aluminum nitride single crystal using a sublimation method, capable of preventing occurrence of defects in the single crystal and of efficiently producing the crystal with good quality and large diameter. <P>SOLUTION: The graphite crucible 4 which is disposed on the lower part in a heating furnace body 2 has on its inner face, a coated film 5 comprising the nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium and osmium. Since such a coated film 5 is stable even at high temperatures of ≥2,000°C and also chemically stable to sublimation gases (Al, N<SB>2</SB>), the aluminum nitride single crystal grown by using the gas generated from the graphite crucible can be prevented from occurrence of defects, thus efficiently producing the single crystal with good quality and large diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for producing an aluminum nitride single crystal and a method for producing the same, and more particularly to a technique for producing an aluminum nitride single crystal with few defects by a sublimation method.

  Of the nitrides of Group III elements, aluminum nitride is expected as a material for a substrate for a GaN-based semiconductor device because of its high thermal conductivity and high lattice matching with gallium nitride. Conventionally, several methods are known as a method for producing this type of nitride single crystal, and the sublimation method is particularly promising (see, for example, Patent Document 1 and Patent Document 2).

  FIG. 2 shows a conventional heating furnace (manufacturing apparatus) 100 for manufacturing a nitride single crystal using a sublimation method. The heating furnace 100 includes a heating furnace main body 101 and an induction heating coil 102 that surrounds the heating furnace main body 101.

  A container-like graphite crucible 103 is disposed in the lower part of the heating furnace main body 101. In the graphite crucible 103, a raw material 104 such as a nitride powder or a sintered body is disposed.

  A plate-shaped susceptor 105 is arranged on the upper wall portion in the heating furnace main body 101 so as to face the graphite crucible 103. The susceptor 105 is made of graphite. A seed crystal 106 is attached to the lower surface of the susceptor 105. The lower surface of the susceptor 105 and the surface (lower surface) of the seed crystal 106 are set to be horizontal.

  Further, an atmospheric gas inlet 107 is formed at the bottom of the heating furnace main body 101, and an atmospheric gas outlet 108 is formed at the upper wall of the heating furnace main body 101.

  A method for producing an aluminum nitride single crystal using such a heating furnace 100 will be described. First, a raw material 104 such as aluminum nitride powder or sintered body is placed in a graphite crucible 103. Next, after the inside of the heating furnace body 101 is evacuated, an atmosphere gas such as nitrogen is introduced from the atmosphere gas inlet 107 at the bottom. Then, the induction heating coil 102 is operated to heat the raw material 104, the susceptor 105, and the seed crystal 106 in the graphite crucible 103. Further, the atmospheric gas is exhausted from the exhaust port 108 formed in the upper wall portion of the heating furnace main body 101.

  By this heating, the raw material 104 in the graphite crucible 103 is melted and sublimated, and the sublimation gas adheres to the surface of the seed crystal 106 and grows. At this time, in order to control the crystallization speed of crystal growth in the seed crystal 106, the temperature of the susceptor 105 and the sublimation speed of the sublimation gas sublimated from the raw material 104 are respectively optimized.

Further, as a prior art relating to a method for producing a nitride single crystal such as aluminum nitride, those described in Non-Patent Document 1 and Non-Patent Document 2 as described below are known.
Japanese Patent Laid-Open No. 10-53495 JP 2004-284869 A Glen A. Slack and TF Mcnelly, J. Cryst. Growth, 34 (1976) 263-279 R. Schlesser and Z. Sitar, J. Cryst. Growth, 234 (2002) 349

  However, in the conventional method for producing an aluminum nitride single crystal, when supplying the raw material gas to the surface of the seed crystal, carbon that is a component of the graphite crucible is mixed into the single crystal simultaneously with the generation of the raw material gas, and the origin of the defect And there are problems such as contamination.

In addition, in the method for manufacturing a nitride single crystal described in Patent Document 2, a graphite product in which the surfaces of a crucible and a susceptor are coated with boron nitride (BN) or silicon nitride (SiN) is used. Like aluminum, since it is a group III element, a mixed crystal (Al _x B _1-x N) is produced, so that the quality of the produced single crystal is lowered. Silicon (Si) is a material used as a dopant to improve the field emission efficiency. It is well known that the conductivity and quality of the material greatly change due to the mixing of silicon, and it is not appropriate to cover the crucible with silicon nitride. In addition, in actual doping, since the influence on the doping concentration from the coating cannot be ignored, the doping amount may not be precisely controlled, which is inappropriate.

  Accordingly, an object of the present invention is to provide a method for manufacturing a nitride single crystal using a sublimation method and an apparatus for manufacturing the same, which can suppress the occurrence of defects in the single crystal and can efficiently manufacture a single crystal having a high quality and a large diameter. It is to provide.

  A first feature of the present invention is a nitriding comprising: a graphite crucible containing a raw material for an aluminum nitride single crystal; and a susceptor that supports a seed crystal on which aluminum nitride sublimated from the graphite crucible is attached to grow the single crystal. An apparatus for producing an aluminum single crystal, wherein the surface of a graphite crucible is coated with a nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium. Is the gist.

  A second feature of the present invention includes a graphite crucible containing a raw material for an aluminum nitride single crystal, and a susceptor that supports a seed crystal on which aluminum nitride sublimated from the graphite crucible is adhered to grow a single crystal. An apparatus for producing an aluminum nitride single crystal, wherein the surface of the portion in contact with the graphite crucible, the susceptor and the sublimation gas is at least selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, osmium. The gist is that it is coated with a nitride of one material.

  A third feature of the present invention is a method for producing an aluminum nitride single crystal, comprising hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, at least an inner surface of a graphite crucible containing a raw material for the aluminum nitride single crystal, After coating a nitride of at least one material selected from rhenium, iridium, ruthenium, and osmium, the raw material for the aluminum nitride single crystal is housed in the graphite crucible, and the graphite crucible is heated to produce the aluminum nitride single crystal The gist is to grow a single crystal of aluminum nitride by sublimating the raw material to generate a raw material gas and attaching the raw material gas.

  According to the present invention, the portion of the graphite crucible to be used that is in contact with the source gas is coated with a nitride of hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, osmium, and thereby the source gas When the aluminum nitride single crystal is produced by the sublimation method, carbon is not mixed therein, and the obtained single crystal is free from defects, and a high-quality, large-diameter single crystal can be produced efficiently.

  Hereinafter, an apparatus and a method for manufacturing an aluminum nitride single crystal according to an embodiment of the present invention will be described.

(First embodiment)
FIG. 1 shows a heating furnace 1 as an apparatus for producing an aluminum nitride single crystal according to a first embodiment of the present invention. The heating furnace 1 includes a heating furnace body 2 and an induction heating coil 3 that surrounds the heating furnace body 2.

As shown in FIG. 1, a container-like graphite crucible 4 is disposed in the lower part of the heating furnace main body (chamber) 2. A coating film 5 made of nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium is formed on the inner surface of the graphite crucible 4. Yes. The graphite crucible 4 is provided with a raw material 6 such as aluminum nitride powder or sintered body. In addition, the coating film 5 made of such a material is stable even at a high temperature of 2000 ° C. or higher, and chemically stable against a sublimation gas (Al, N ₂ ).

  A plate-shaped susceptor 7 is disposed on the upper wall portion in the heating furnace body 2 so as to face the graphite crucible 4. The susceptor 7 is made of graphite. A seed crystal 8 is attached to the lower surface of the susceptor 7. The lower surface of the susceptor 7 and the surface (lower surface) of the seed crystal 8 are set to be horizontal.

  Further, an atmosphere gas inlet 9 is formed at the bottom of the heating furnace body 2, and an atmosphere gas outlet 10 is formed at the upper wall of the heating furnace body 2.

  A method for producing an aluminum nitride single crystal using such a heating furnace 1 will be described. First, a raw material 6 such as aluminum nitride powder or sintered body is placed in a graphite crucible 4. Next, after the inside of the heating furnace body 2 is evacuated, an atmosphere gas such as nitrogen is introduced from the atmosphere gas inlet 9 at the bottom. Then, the induction heating coil 3 is operated to heat the raw material 6, the susceptor 7 and the seed crystal 8 in the graphite crucible 4. Incidentally, the temperature in the graphite crucible 4 is controlled to 2000 to 2300 ° C., and the surface temperature of the seed crystal 8 is controlled to 1990 to 2050 ° C. Further, the atmospheric gas is exhausted from the exhaust port 10 formed in the upper wall portion of the heating furnace body 2.

  By this heating, the raw material 6 in the graphite crucible 4 is melted and sublimated, and the sublimation gas adheres to the surface of the seed crystal 8 and grows. During the crystal growth, in order to control the crystallization speed of the crystal growth on the surface of the seed crystal 8, the temperature of the seed crystal 8 and the sublimation speed of the sublimation gas sublimated from the raw material 6 (sublimation amount per unit time) Temperature control is performed to optimize each of these.

  Examples are shown below.

Table 1 below shows the presence / absence and type of coating material on the inner surface of the graphite crucible 4, the carbon content (ppm) and the X-ray rocking curve of the aluminum nitride single crystal produced in the heating furnace 1 using these graphite crucibles 4 The full width at half maximum (arcsec) is shown.

  As shown in Table 1, by coating the inner surface of the graphite crucible 4 with each nitride of hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium, Can be suppressed, and the carbon content in the aluminum nitride single crystal can be suppressed to 100 ppm or less. Therefore, it is possible to suppress the occurrence of defects due to carbon mixing into the aluminum nitride single crystal. On the other hand, when the coating film is not formed on the inner surface of the graphite crucible 4, the carbon content in the aluminum nitride single crystal is 1000 ppm, and the aluminum nitride single crystal is coated with boron nitride as the coating film. The carbon content in the aluminum nitride single crystal when the silicon nitride coating was 120 ppm and silicon nitride was coated as the coating film was 110 ppm. For this reason, according to this invention, the carbon content rate in an aluminum nitride single crystal can be made low, and it can suppress that a defect generate | occur | produces in a single crystal.

  Further, as shown in Table 1 above, the inner surface of the graphite crucible 4 is coated with each nitride of hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium to form an aluminum nitride single crystal. When manufactured, the half width of the X-ray rocking curve is 270 seconds or less, and it can be seen that the crystal has good crystallinity. On the other hand, when the coating film is not formed on the inner surface of the graphite crucible 4, the half width of the X-ray rocking curve of the aluminum nitride single crystal is 540 seconds, and boron nitride is coated as the coating film. The carbon content in the aluminum nitride single crystal was 120 ppm, and the carbon content in the aluminum nitride single crystal was 110 ppm when silicon nitride was coated as a coating film.

(Second Embodiment)
FIG. 2 shows a heating furnace 20 as an aluminum nitride single crystal manufacturing apparatus according to the second embodiment of the present invention. The heating furnace 20 includes a heating furnace body 21 and an induction heating coil (heating heater) 22 surrounding the heating furnace body 21.

As shown in FIG. 2, a container-like graphite crucible 23 is disposed in the heating furnace main body 21. A coating film 24 made of nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium is formed on the inner surface of the graphite crucible 23. Yes. The upper opening of the graphite crucible 23 is closed with a crucible lid 25 made of graphite. A coating film 24 similar to the graphite crucible 23 is formed on the lower surface of the crucible lid 25. The coating film 24 made of such a material is stable even at a high temperature of 2000 ° C. or higher, and chemically stable against sublimation gases (Al, N ₂ ). In the graphite crucible 23, a raw material 26 made of metal nitride powder such as polycrystalline aluminum nitride powder or sintered body is disposed.

  A seed crystal 27 is attached to the lower surface of the crucible lid 25. The lower surface of the crucible lid 25 and the surface (lower surface) of the seed crystal 27 are set to be horizontal.

  In the heating path 20 according to the present embodiment, the heating furnace body 21 is heated by the induction heating coil 22, the lower portion of the graphite crucible 23 becomes a sublimation portion (vaporization portion), and the lower surface side of the crucible lid 25 becomes a precipitation portion.

  Further, an atmospheric gas inlet 28 is formed at the bottom of the heating furnace main body 21, and an atmospheric gas outlet 29 is formed at the upper wall of the heating furnace main body 21.

  A method for producing an aluminum nitride single crystal using such a heating furnace 20 will be described. First, a raw material 26 such as aluminum nitride powder or sintered body is placed in the graphite crucible 23. Next, after the inside of the heating furnace body 21 is evacuated, a predetermined amount of atmospheric gas such as nitrogen is introduced from the atmospheric gas inlet 28 at the bottom. And the induction heating coil 22 is operated and the raw material 26 is vaporized. The vaporized raw material is cooled by contacting the lower surface of the crucible lid 25, and a single crystal is deposited on the seed crystal 27.

  At this time, a portion of the graphite crucible 23 to be used that is in contact with the raw material gas is coated with a coating film 24 made of a nitride of hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, or osmium. As a result, carbon can be prevented from being mixed in the raw material gas, and when the aluminum nitride single crystal is produced by the sublimation method, the obtained single crystal is free from defects, and a high-quality, large-diameter single crystal can be produced efficiently. .

Table 2 below shows the presence / absence and type of coating material on the inner surface of the graphite crucible 23 and the lower surface of the crucible lid 25, and the carbon content of the manufactured aluminum nitride single crystal.

As described above, a material that is stable even at a high temperature of 2000 ° C. or more and that is chemically stable to the sublimation gas (Al, N ₂ ) is formed on the inner surface of the graphite crucible 23 and the lower surface of the crucible lid 25 in contact with the source gas. As a result, the obtained single crystal has no defects, and a high-quality, large-diameter single crystal can be produced efficiently.

  As described above, according to the nitride single crystal manufacturing apparatus and the manufacturing method thereof according to the present invention, it is possible to efficiently manufacture a single crystal nitride having a high quality and a large diameter.

  In the above-described embodiments and examples, description has been made by applying aluminum nitride as a nitride. However, it goes without saying that the present invention can be applied to the production of other nitride single crystals.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory cross-sectional view showing a nitride single crystal manufacturing apparatus according to a first embodiment of the present invention. It is a cross-sectional explanatory view showing a nitride single crystal manufacturing apparatus according to a second embodiment of the present invention. It is sectional explanatory drawing which shows the manufacturing apparatus of the conventional nitride single crystal.

Explanation of symbols

1,20 Heating furnace (manufacturing equipment)
2,21 Heating furnace body 3,22 Induction heating coil 4,23 Graphite crucible 5,24 Coating film 6,26 Raw material 7 Susceptor 8,26 Seed crystal 9,28 Inlet port 10, 29 Exhaust port 25 Crucible lid

Claims (3)

An apparatus for producing an aluminum nitride single crystal, comprising: a graphite crucible containing a raw material for an aluminum nitride single crystal; and a susceptor for supporting a seed crystal on which aluminum nitride sublimated from the graphite crucible is attached to grow the single crystal. And
The surface of the graphite crucible is coated with a nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium. Manufacturing equipment. An apparatus for producing an aluminum nitride single crystal, comprising: a graphite crucible containing a raw material for an aluminum nitride single crystal; and a susceptor for supporting a seed crystal on which aluminum nitride sublimated from the graphite crucible is attached to grow the single crystal. And
The surface of the portion where the graphite crucible, the susceptor and the sublimation gas contact is coated with a nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium. An apparatus for producing an aluminum nitride single crystal. At least the inner surface of the graphite crucible containing the raw material for aluminum nitride single crystal is coated with a nitride of at least one material selected from hafnium, niobium, zirconium, tungsten, vanadium, molybdenum, rhenium, iridium, ruthenium, and osmium. After
The raw material for the aluminum nitride single crystal is housed in the graphite crucible,
Heating the graphite crucible to sublimate the raw material for the aluminum nitride single crystal to generate a raw material gas;
A method for producing an aluminum nitride single crystal, comprising growing the aluminum nitride single crystal by attaching the source gas.

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