JP2011153045A - Method for producing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a single crystal by which a high-quality single crystal can be obtained by suppressing cracks of a reactor in a hydride vapor phase growth method. <P>SOLUTION: The method for producing a single crystal is carried out by using a susceptor 1, which includes a through-hole 3 having a first opening 2a on a lower face opposing to a supply direction of a raw material gas 5, a second opening 2b on an upper face, wherein the second opening is smaller than the first opening 2a, and a slope face 2c for disposing a seed substrate 4 on an inner wall face, the through-hole 3 exhibiting a truncated cone shape that becomes narrower from the second opening 2b to the first opening 2a; and the method comprises supplying a raw material gas 5 to the susceptor 1 through the first opening 2a and discharging the raw material gas 5 passing through the seed substrate 4 to the outside of the susceptor 1 through the second opening 2b. Thus, the raw material gas 5 is inhibited from flowing into a reactor 7 disposed in the periphery of the susceptor 1, which reduces cracks of the reactor 7 and results in long-term growth of a single crystal, thereby a high-quality single crystal in a bulk state can be obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a single crystal by growing the single crystal by a vapor phase growth method.

Among single crystals, nitride single crystals such as GaN and AlGaN are light emitting elements such as light emitting diodes (LEDs) and semiconductor lasers (LDs), power devices such as transistors, and power FETs (Field Effect Transistors). In the future, the use is expected to expand.

However, Group 3 nitride single crystals such as GaN and AlGaN have a high melting point and a high equilibrium vapor pressure of N (nitrogen), which makes it difficult to produce bulk single crystals from the liquid phase. is there. Therefore, a thin film is grown on a seed substrate such as sapphire (Al ₂ O ₃ ) or silicon carbide (SiC), and the thin film is used for various devices.

  For example, Patent Document 1 describes a technique in which a single crystal body of gallium nitride is provided on a seed substrate by supplying a source gas of ammonia gas and gallium chloride gas using a hydride vapor phase growth method.

JP 2007-126320 A

  However, in the manufacturing method of Patent Document 1, the raw material gas that has passed through the seed substrate spreads around the susceptor and flows along a reactor provided outside the susceptor. For this reason, the unreacted gas in the raw material gas tends to react and adhere to the reactor. The reactor is made of, for example, quartz, and there has been a problem that when the reactor is cooled after a single crystal growth for a long time, the reactor is cracked by gallium nitride attached to the reactor.

  The present invention has been completed in view of the above-mentioned conventional problems, and suppresses cracking of the reactor, and provides a high-quality single crystal.

  A method for producing a single crystal according to an embodiment of the present invention includes a first opening on a lower surface facing a supply direction of a source gas, a second opening smaller than the first opening on an upper surface, and an inner wall surface. A susceptor having a through-hole having a frustum shape tapered from the second opening toward the first opening. Step 1 for installing a substrate on the installation surface, Step 2 for supplying the source gas to the seed substrate from the first opening, and the source gas passing through the seed substrate among the source gases, And moving to the second opening, and then releasing from the second opening to the outside of the susceptor.

  It is preferable that the through hole has a polygonal frustum shape.

The installation surface of the susceptor is a bottom of a recess, and step 1 is a step of installing the seed substrate in the recess so that the single crystal growth surface of the seed substrate and the slope of the through hole are flush with each other. Preferably there is.

  It is preferable that the method further includes a step of rotating the susceptor along a central axis of the frustum-shaped through hole.

  The vapor phase growth method is a hydride vapor phase growth method, and the single crystal to be grown is preferably composed of a nitride single crystal.

  According to the method for producing a single crystal of the present invention, by using a susceptor having a specific shape in a vapor phase growth method, it is possible to suppress the source gas that has passed through the seed substrate from spreading to the outer peripheral side of the susceptor. . Therefore, it is possible to suppress the flow of the raw material gas to the reactor provided on the outer periphery of the susceptor, reduce the cracking of the reactor, and as a result, the single crystal can be grown for a long time, resulting in a high quality in bulk form. Single crystal can be provided.

It is a cross-sectional schematic diagram which shows an example of the susceptor 1 used for the manufacturing method of the single crystal of this invention. FIG. 2 is a vertical sectional view of a vapor phase growth apparatus using the susceptor 1 of FIG. 1. It is a perspective view which shows the susceptor 1 of another aspect. FIG. 3 is an enlarged view of FIG. 2 in which the vicinity of the susceptor 1 in the vapor phase growth apparatus of FIG. 2 is enlarged.

  Hereinafter, an exemplary embodiment of the method for producing a single crystal of the present invention will be described.

  The method for producing a single crystal of the present invention uses a vapor phase growth method. Examples of the vapor phase growth method include a hydride vapor phase growth method (HVPE method), a metal organic vapor phase growth method (MOVPE method), and a sublimation method. Among them, the HVPE method is preferable because it has a high growth rate, good quality, and easy to produce a nitride body.

  In the present invention, the susceptor 1 provided with the through hole 3 is used. As shown in FIG. 1, in the susceptor 1, the through hole 3 is a first opening 2 a provided on the lower surface, a second opening 2 b provided on the upper surface, and a slope of the inner wall of the through hole 3. And an installation surface 2c on which 4 is installed. The through-hole 3 has a frustum shape that tapers from the first opening 2a toward the second opening 2b. In particular, the through-hole 3 preferably has a polygonal frustum shape, and particularly preferably a polygonal frustum having a small number of corners on the bottom surface, particularly a quadrangular pyramid shape. This is because the through hole 3 has a polygonal truncated pyramid shape with a small number of corners on the bottom surface, so that the area of the inclined surface, which is the installation surface 2c, is increased, so that a seed substrate having a large area can be installed.

  FIG. 2 shows a vapor phase growth apparatus using the susceptor 1 of FIG. The susceptor 1 is suspended in a cylindrical reactor 7 by a holding body 9 of the susceptor 1. A seed substrate 4 is provided on the inclined surface 2 c of the susceptor 1.

  The seed substrate 4 is preferably provided so as to face obliquely downward, so that impurities generated in the reactor 7 are less likely to adhere to the seed substrate 4.

In the vapor phase growth apparatus of FIG. 2, the etching gas 11 is caused to flow along the inner wall surface of the reactor 7. As this etching gas 11, a gas capable of etching a single crystal is selected. For example, when the single crystal is a group III nitride single crystal, examples of the etching gas 11 include hydrogen halides such as hydrogen chloride, hydrogen boride, hydrogen bromide, and hydrogen fluoride. In particular, when the single crystal is GaN, HCl is preferable because it has the best etching performance.

  However, when an ordinary susceptor is used, the etching gas hits the seed substrate and there is a problem that the grown single crystal is scraped. By using the susceptor 1 used in the present invention, the etching gas 11 is changed to that shown in FIG. As shown in FIG. 4, since the outer side of the susceptor 1 is passed, such a problem is solved.

  The seed substrate 4 in FIG. 2 has a flat inclined surface of the through hole 3, but as shown in FIG. 3, a recess 2d is provided on the inclined surface of the through hole 3 (see FIG. 3 (a)), and its bottom surface is formed. The seed substrate 4 is preferably provided in the recess 2d so as to be the installation surface 2c of the seed substrate 4 (see FIG. 3B). With this configuration, since the contact area between the seed substrate 4 and the susceptor 1 is increased, the adhesion between the seed substrate 4 and the susceptor 1 is improved. Moreover, as shown in FIG.3 (b), it is preferable to provide a stopper in the slope of the through-hole 3, and hold | maintain the seed substrate 4 by this.

  In the vapor phase growth apparatus shown in FIG. 2, the susceptor 1 on which the seed substrate 4 is installed as described above is rotated by the holding body 9. As shown in FIG. 4, the rotation axis A of the susceptor 1 is in the vertical direction. Here, the vertical direction indicates the direction of gravity, and deviation within a range of −5 ° to 5 ° is allowed. The rotation axis A of the susceptor 1 preferably coincides with the central axis of the frustum-shaped through hole 3. The rotation speed of the susceptor 1 can be selected from the range of about 2 rpm to 50 rpm, for example.

  In the vapor phase growth apparatus, a gas supply pipe 8 is provided below the susceptor 1, and the source gas 5 is supplied from the gas supply pipe 8 to the seed substrate 4.

  As the source gas 5, for example, when the single crystal to be grown is a group 3-5 single crystal such as gallium nitride, a group 3 element gas and a group 5 element gas are used. The group 3 element gas refers to a gas containing a group 13 element (eg, gallium, aluminum, indium, etc.) in the periodic table. Examples include gallium chloride, aluminum chloride, and indium chloride. The group 5 element gas means a gas containing a group 15 element (for example, nitrogen, arsenic, etc.) in the periodic table, and examples thereof include ammonia.

  The source gas 5 is supplied from the gas supply pipe 8 so as to be supplied to the surface (single crystal growth surface) of the seed substrate 4 (5a in FIG. 4). Then, the source gas 5 b that has passed through the seed substrate 4 such as a gas that has not been used for the reaction travels along the slope of the through hole 3 toward the second opening 2 b. Then, the source gas 5b is discharged out of the susceptor 1 from the second opening 2b. Since the through hole 3 has a frustum shape, the source gas 5b released from the second opening 2b is less likely to flow to the outer peripheral side of the susceptor 1, and as a result, the reactor provided on the outer peripheral side of the susceptor 1 7 and the source gas 5b can be prevented from contacting each other. In particular, as shown in FIG. 3, when the seed substrate 4 is installed in the recess 2d so that the single crystal growth surface of the seed substrate 4 and the inclined surface of the through hole are flush with each other, the source gas 5 is in a laminar state. It is preferable because it allows crystal growth.

A single crystal obtained using such a susceptor 1 is a bulk single crystal having a thickness of 10 mm or more. Further, a high-quality single crystal having a low average dislocation density of 1 × 10 ⁹ cm ⁻² or less was obtained. In this manner, a plurality of single crystal substrates can be cut out from a single crystal body having a large thickness and having a small variation in crystal quality by dicing.

  In addition, the obtained single crystal is processed into a substrate shape by the following method, for example.

  First, the outer periphery of a single crystal grown using a diamond grindstone is ground to a predetermined outer diameter. Next, a single crystal body is fixed to a predetermined thickness by a wire saw in which diamond abrasive grains or the like are fixed, or a diamond or SiC abrasive grain is dripped onto a brass wire with a slurry, and the wire is reciprocated to cut the crystal. Cut into a wafer shape (for example, 0.6 mm).

  And after rough-polishing both surfaces of a single crystal wafer using a diamond abrasive grain or a SiC abrasive grain, the surface used in a device process is mirror-polished using colloidal silica, and a single crystal wafer substrate is obtained.

  Details of each configuration will be described below.

(Susceptor 1)
Graphite can be used for the susceptor 1, but when corrosive ammonia and hydrogen chloride are used as the raw material gas for the single crystal, the surface is coated with at least one selected from the group consisting of SiC, BN and TaC. It is preferable to keep it. Examples of the coating method include a CVD method and a sputtering method. Thereby, the corrosion resistance of the susceptor 1 is improved. PBN is preferable among BN. PBN is pyrogenic boron nitride (pyrolytic BN (p-BN)).

  The inclination angle of the frustum-shaped slope in the through-hole 3 of the susceptor 1 is preferably 30 to 70 ° with respect to the supply direction of the source gas 5.

(Seed board 4)
Specific examples of the seed substrate 4 include group III nitride single crystals such as GaN and AlGaN, sapphire, SiC, GaN single crystals, AlN single crystals, or mixed crystals of GaN single crystals and AlN single crystals. . The seed substrate 4 is preferably made of the same material as that of the single crystal to be grown, that is, one that is homoepitaxially grown, since the quality of the obtained single crystal is excellent. For example, when producing a GaN single crystal, the seed substrate 4 is preferably a GaN substrate. The thickness of the seed substrate 4 for growth is about 0.3 to 0.6 mm. Moreover, when the seed substrate 4 is disk shape, the diameter of the seed substrate 4 is 20 mm-60 mm.

(Reactor 7 and gas supply pipe 8)
The reactor 7 and the gas supply pipe 8 forming the vapor phase growth apparatus are made of quartz or the like, and those having a cylindrical shape such as a cylindrical shape or a rectangular tube shape are preferably used.

(Heater 6)
The heater 6 is provided around the outer periphery of the reactor 7. The heating performed in the production of the single crystal is 1000 to 1300 ° C. at the start of single crystal growth.

1: Susceptor 2a: 1st opening 2b: 2nd opening 2c: Installation surface 2d: Concavity 3: Through hole 4: Seed substrate 5: Source gas 5a: Supplied to the surface (single crystal growth surface) of seed substrate 4 Source gas 5b: Source gas that has passed through the seed substrate 4 6: Heater 7: Reactor 8: Gas supply pipe 9: Holding body of susceptor 1 10: Stopper 11: Etching gas A: Rotating shaft of susceptor 1

Claims (5)

A method for producing a single crystal by vapor deposition,
A first opening on the lower surface facing the supply direction of the source gas, a second opening smaller than the first opening on the upper surface, and an installation surface for installing the seed substrate on the inner wall surface, Step 1 of installing the seed substrate on the installation surface with respect to a susceptor having a through hole showing a frustum shape tapered from the second opening toward the first opening;
Step 2 of supplying the source gas to the seed substrate from the first opening;
The source gas that has passed through the seed substrate out of the source gas is moved to the second opening and then released from the second opening to the outside of the susceptor; and
A method for producing a single crystal comprising:   The method for producing a single crystal body according to claim 1, wherein the through hole has a polygonal frustum shape. The installation surface of the susceptor is a bottom of a recess;
3. The process for producing a single crystal according to claim 1, wherein step 1 is a step of installing the seed substrate in the recess so that the single crystal growth surface of the seed substrate and the slope of the through hole are flush with each other. Method.   The method for producing a single crystal body according to any one of claims 1 to 3, further comprising a step of rotating the susceptor along a central axis of the frustum-shaped through hole. The vapor deposition method is a hydride vapor deposition method,
The method for producing a single crystal according to claim 1, wherein the single crystal to be grown is composed of a nitride single crystal.

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