JP2012006772A - Method for growing group iii nitride crystal and group iii nitride crystal substrate - Google Patents

Abstract

There is provided a group III nitride crystal growth method for growing a large group III nitride crystal using a plurality of seed crystal substrates without generating pits on the surface.
The group III nitride crystal growth method includes arranging a plurality of seed crystal substrates 1 such that their main surfaces 1m are parallel to each other and their side surfaces 1s are adjacent to each other, and their seeds are arranged. A first crystal growth step for growing a first group III nitride crystal 10 on the main surface 1m of the crystal substrate 1 by a liquid phase growth method, and a main surface of the first group III nitride crystal 10 And a second crystal growth step for growing the second group III nitride crystal 20 by a hydride vapor phase growth method.
[Selection] Figure 1

Description

  The present invention relates to a method for growing a group III nitride crystal on a main surface of a plurality of seed crystal substrates and a group III nitride crystal substrate obtained by processing a group III nitride crystal obtained by such a growth method.

  From the viewpoint of reducing the cost, Group III nitride crystals suitably used for semiconductor devices such as light-emitting devices and electronic devices are required to be large.

  Here, since there is no large group III nitride crystal in nature, it is necessary to grow the group III nitride crystal using a substrate having a chemical formula other than the group III nitride crystal as the base substrate. For example, Japanese Patent Laid-Open No. 2000-349338 (hereinafter referred to as Patent Document 1) discloses a thick III nitride (without warping or cracking) on a substrate having a chemical formula other than a group III nitride crystal as a base substrate ( A method of growing a (GaN) crystal film is disclosed.

  However, in the growth method disclosed in Patent Document 1, when the area of the main surface of the base substrate is increased, the crystal lattice mismatch between the group III nitride crystal and the base substrate causes the inside of the group III nitride crystal. Therefore, it is difficult to grow a large group III nitride crystal.

  In view of this, Japanese Patent Application Laid-Open No. 2008-133151 (hereinafter referred to as Patent Document 2) discloses an arrangement step in which a plurality of seed substrates are arranged shifted to the side of the seed substrate, and an HVPE method (hydride vapor phase epitaxy method, hereinafter the same). And a growth step of growing a group III nitride crystal on each surface of the plurality of seed substrates, so that the crystals grown on the surfaces of the plurality of seed substrates are integrated in the growth step. We propose a crystal growth method to grow the crystal.

JP 2000-349338 A JP 2008-133151 A

  However, in the crystal growth method proposed in Patent Document 2, since the group III nitride crystal obtained by integration generates pits on the surface, the yield of the obtained group III nitride crystal substrate is reduced. There was a problem.

  In order to solve the above problems, the present invention provides a method for growing a group III nitride crystal, in which a large group III nitride crystal is grown using a plurality of seed crystal substrates without generating pits on the surface. Objective. From a large group III nitride crystal free from such pits, a large group III nitride crystal substrate can be obtained with good yield.

  A method for growing a group III nitride crystal according to the present invention includes a step of preparing a plurality of seed crystal substrates having a main surface having a predetermined plane orientation and a plurality of side surfaces, A step of arranging the first group III nitride crystals by a liquid phase growth method on the main surfaces of the plurality of seed crystal substrates that are arranged in parallel with each other such that their side surfaces are adjacent to each other; And a second crystal growth step of growing a second group III nitride crystal on the main surface of the first group III nitride crystal by a hydride vapor phase growth method. Here, the first group III nitride crystal is grown so that each partial crystal grown on the main surface of each seed crystal substrate is integrated, and the second group III nitride crystal is the first group III nitride crystal. Growing so as to be integrated with the group nitride crystal.

  In the group III nitride crystal growth method according to the present invention, the seed crystal substrate can be a GaN seed crystal substrate, and the liquid phase growth method can be a flux method.

  A group III nitride crystal substrate according to the present invention is obtained by processing a group III nitride crystal obtained by integrating the first group III nitride crystal and the second group III nitride crystal obtained by the above growth method. can get.

  ADVANTAGE OF THE INVENTION According to this invention, the growth method of the group III nitride crystal which grows a large group III nitride crystal without generating a pit on the surface using a several seed crystal substrate is provided. In addition, a large group III nitride crystal substrate obtained by the above-described group III nitride crystal growth method with high yield is provided.

It is a schematic sectional drawing which shows an example of the growth method of the group III nitride crystal concerning this invention. Here, (A) shows preparation steps and arrangement steps of a plurality of seed crystal substrates, (B) shows a first crystal growth step, (C) shows a second crystal growth step, and (D) Indicates a crystal substrate forming step. It is a schematic sectional drawing which shows an example of the growth method of the conventional group III nitride crystal. Here, (A) shows a preparation step and a placement step of a plurality of seed crystal substrates, (B) shows a crystal growth step, and (C) shows a crystal substrate formation step. It is a schematic plan view which shows the example of arrangement | positioning of a some seed crystal substrate. Here, (A) shows an example, and (B) shows another example. It is a schematic sectional drawing which shows an example of the 1st crystal growth process in the growth method of the group III nitride crystal concerning this invention. It is a schematic sectional drawing which shows an example of the 2nd crystal growth process in the growth method of the group III nitride crystal concerning this invention.

[Growth of group III nitride crystals]
Referring to FIG. 1 and FIG. 3, a group III nitride crystal growth method according to an embodiment of the present invention includes a plurality of seed crystal substrates 1 each having a main surface 1m having a predetermined plane orientation and a plurality of side surfaces 1s. A step of preparing (FIG. 1 (A)), a step of arranging a plurality of seed crystal substrates 1 such that their main surfaces 1m are parallel to each other and their side surfaces 1s are adjacent to each other (FIG. 1 (A) and 3A and 3B) and a first crystal for growing a first group III nitride crystal 10 on a main surface 1m of a plurality of seed crystal substrates 1 arranged by liquid phase growth method. A growth step (FIG. 1C) and a second group III nitride crystal 20 for growing a second group III nitride crystal 20 on the main surface 10m of the first group III nitride crystal 10 by HVPE (hydride vapor phase epitaxy). A crystal growth step (FIG. 1D).

  In the present embodiment, the first group III nitride crystal 10 is grown so that the partial crystals 10u grown on the main surface 1m of the seed crystal substrate 1 are integrated, and the second group III nitride is grown. The crystal 20 is grown so as to be integrated with the first group III nitride crystal 10.

  According to the method for growing a group III nitride crystal of the present embodiment, the first group III nitride crystal in which no pits are generated on the main surface 10 m on the main surface 1 m of the plurality of seed crystal substrates 1 by the liquid phase growth method. Therefore, when the second group III nitride crystal 20 is grown on the main surface 10 m of the first group III nitride crystal 10 by the HVPE method, the first group III nitride crystal 10 is integrated with the second group III nitride crystal 20 to obtain a group III nitride crystal 30 having no pits on the main surface 30m. Since such a group III nitride crystal 30 does not generate pits on its main surface 30m, the group III nitride crystal substrates 30x, 30y, and 30z can be obtained with high yield.

  By the way, referring to FIG. 2, a conventional group III nitride crystal growth method is a step of preparing a plurality of seed crystal substrates 1 having a main surface 1m having a predetermined plane orientation and a plurality of side surfaces 1s (FIG. 2 ( A)) and a step of arranging a plurality of seed crystal substrates 1 such that their main surfaces 1m are parallel to each other and their side surfaces 1s are adjacent to each other (FIG. 2A, FIG. 3A and FIG. B)) and a crystal growth step (FIG. 2B) for growing a group III nitride crystal 40 by HVPE on the main surface 1m of the plurality of seed crystal substrates 1 arranged.

  Referring to FIG. 2B, in the above-described crystal growth step, each of the partial crystals 40u grown on each seed crystal substrate 1 is joined and integrated with each other at a joint 40g to form a group III nitride crystal. 40 grows. However, since pits 40p are generated on the main surface 40m of the group III nitride crystal 40, as shown in FIG. 2C, the group III nitride crystal substrates 40x, 40y, obtained from the group III nitride crystal 40 are formed. The yield of 40z is lowered.

  A cross section of group III nitride crystal 40 grown on a plurality of seed crystal substrates 1 is observed as an emission intensity distribution image by an optical method such as a CL (cathode luminescence) method, a PL (photo luminescence) method, or a fluorescence microscope. As shown in FIG. 2B, a main surface 40m of a group III nitride crystal 40 substantially parallel to the main surface 1m is formed on the center of the main surface 1m of each seed crystal substrate 1 as a crystal growth surface. The main surface growth crystal region 40um grown as a facet growth crystal is formed on the periphery of the main surface 1m of each seed crystal substrate 1 with a facet 40f that is not substantially parallel to the main surface 1m as a crystal growth surface. A region 40uf is formed, and a pit 40p formed by the facet 40f is generated above the joint 40g of the partial crystal 40u. It was found. Further, it was found that the joint portions 40g of the respective partial crystals 40u are located on the extended surfaces above the side surfaces 1s of the seed crystal substrates 1 adjacent to each other.

  As will be described later, in the HVPE method of the group III nitride crystal 40, the pit generation rate could be reduced by increasing the crystal growth temperature, but it was not possible to prevent the generation of pits. .

  On the other hand, referring to FIG. 1, in the method for growing a group III nitride crystal of the present embodiment, first, a liquid phase growth method is used on a main surface 1m of a plurality of seed crystal substrates 1 arranged. The first group III nitride crystal 10 is grown, and then the second group III nitride crystal 20 is grown on the main surface 10m of the first group III nitride crystal 10 by the HVPE method. By integrating the group III nitride crystal 10 with the second group III nitride crystal 20, the group III nitride crystal 30 having no pit generation on the main surface 30m is obtained. A method for growing a group III nitride crystal of this embodiment will be described in detail below with reference to FIGS. 1 and 3 to 5.

(Seed crystal substrate preparation process)
Referring to FIG. 1A, in the method for growing a group III nitride crystal of this embodiment, first, a plurality of seed crystal substrates 1 having a main surface 1m having a predetermined plane orientation and a plurality of side surfaces 1s are prepared. A process is provided.

  The step of preparing a plurality of seed crystal substrates 1 is not particularly limited. For example, a wafer is formed by cutting a seed crystal in a plane parallel to a predetermined plane orientation so that the main surface of the wafer becomes a polygon. The seed crystal substrate 1 can be formed by cutting, and the main surface 1m and the plurality of side surfaces 1s of the seed crystal substrate 1 can be ground and / or polished. Here, the method of cutting out the seed crystal and the wafer is not particularly limited, and examples thereof include an inner peripheral blade, an outer peripheral blade, and a wire saw.

  The seed crystal substrate 1 is not particularly limited. From the viewpoint of growing the following first and second group III nitride crystals with good crystallinity, the seed crystal substrate has high lattice constant matching with the group III nitride crystal. Is preferred. From this point of view, the seed crystal substrate 1 is preferably a sapphire seed crystal substrate, a SiC (silicon carbide) seed crystal substrate, or a group III nitride seed crystal substrate, and among the group III nitride seed crystal substrates, the seed crystal substrate 1 is grown on those seed crystal substrates. A group III nitride seed crystal substrate having the same chemical formula as the group III nitride crystal is particularly preferred. Of the group III nitride seed crystal substrates, a GaN seed crystal substrate is particularly preferable from the viewpoint of easy availability.

  The shape of the main surface 1m of the seed crystal substrate 1 is not particularly limited as long as the main surfaces 1m can be arranged so that the main surfaces 1m are parallel to each other and the side surfaces 1s are adjacent to each other. Examples include triangles such as isosceles triangles and right triangles, squares such as squares, rectangles, rhombuses, and parallelograms, and hexagons such as regular hexagons and parallelograms. From the viewpoint of high workability for cutting out from the seed crystal, a right-angled quadrangle such as a square or a rectangle is preferable.

  The area of the main surface 1m of the seed crystal substrate 1 is not particularly limited, but from the viewpoint of ease of handling, when the main surface is the above polygon, the length of the shortest side is 5.0 mm or more and the longest side is The length is preferably 100 mm or less.

  The predetermined plane orientation of the main surface 1m of the seed crystal substrate 1 is not particularly limited, but the first group III nitride crystal having no pits on the main surface can be stably grown on the main surface 1m by the liquid phase growth method. From the viewpoint, when the seed crystal substrate 1 is hexagonal, the inclination angle from the (0001) plane is preferably 5 ° or less, more preferably 1 ° or less, and 0.2 ° or less. More preferably it is. Here, the plane orientation of the main surface 1m of the seed crystal substrate 1 is measured by an X-ray diffraction method.

  The average roughness Ra of the main surface 1m of the seed crystal substrate 1 is preferably 10,000 nm or less, and more preferably 100 nm or less, from the viewpoint of preventing abnormal growth at the very initial stage of crystal growth. Here, the average roughness Ra refers to the arithmetic average roughness Ra defined in JIS B0601: 2001. Specifically, the standard roughness Ra is extracted from the roughness curve in the direction of the average line, and this extracted portion The distance from the average line to the roughness curve (absolute value of deviation) is summed and averaged over the standard length. The average roughness Ra is measured by an AFM (atomic force microscope).

  The predetermined plane orientation of the plurality of side surfaces 1s of the seed crystal substrate 1 is not particularly limited. However, the plurality of seed crystal substrates 1 are arranged such that their main surfaces 1m are parallel and their side surfaces 1s are adjacent to each other. From the viewpoint of arranging them close to each other (filled in a plane), the inclination angle from the (0001) plane is preferably 85 ° or more and 95 ° or less, more preferably 89 ° or more and 91 ° or less, 89 More preferably, the angle is 8 ° or more and 90.2 ° or less. Further, from the viewpoint of suppressing the generation of voids in the joint portion, at least one of the surface orientations of the plurality of side surfaces 1s is inclined from any one of the {10-10} plane and the {11-20} plane. The angle is preferably 5 ° or less, more preferably 1 ° or less, and further preferably 0.2 ° or less. Here, the plane orientation of the side surface 1s of the seed crystal substrate 1 is measured by an X-ray diffraction method.

  The average roughness Ra of the plurality of side surfaces 1s of the seed crystal substrate 1 is preferably 10,000 nm or less, and more preferably 100 nm or less from the viewpoint of reducing the gap between the seed crystal substrates.

(Seed crystal substrate placement process)
Referring to FIG. 1 (A) and FIGS. 3 (A) and 3 (B), in the method for growing a group III nitride crystal of the present embodiment, next, a plurality of seed crystal substrates 1 have their main surfaces 1m A step of arranging the side surfaces 1s so as to be parallel to each other and adjacent to each other. By the seed crystal substrate arranging step, the first group III nitride crystal 10 in which the partial crystals 10u grown on the main surface 1m of the seed crystal substrate 1 of the plurality of seed crystal substrates 1 are integrated is grown. Can be made.

  In the step of arranging the plurality of seed crystal substrates 1, the plurality of seed crystal substrates 1 are arranged such that their main surfaces 1m are parallel to each other and their side surfaces 1s are adjacent to each other. Those main surfaces 1m need only be parallel to each other and do not necessarily have to be on the same plane. However, from the viewpoint of growing the first group III nitride crystal having high crystallinity in which the partial crystals 10u are integrated, The difference in height between the main surfaces 1 m is preferably 10000 nm or less, more preferably 1000 nm or less, and the main surfaces are more preferably on the same plane.

  Also, referring to FIGS. 3A and 3B, the side surfaces 1s are adjacent to each other, and the first group III nitride crystal having high crystallinity in which the partial crystals 10u are integrated is grown. In view of this, the distance ΔD between the adjacent side surfaces 1s is preferably 200 μm or less, more preferably 100 μm or less, and more preferably the adjacent side surfaces 1s are in contact with each other.

(First crystal growth step)
Referring to FIG. 1B, the group III nitride crystal growth method of the present embodiment is next performed on a main surface 1m of a plurality of seed crystal substrates 1 arranged by liquid phase growth method. A first crystal growth step for growing one group III nitride crystal 10. By such a first crystal growth step, the respective partial crystals 10u grown on the main surface 1m of the respective seed crystal substrates 1 are integrated by joining at the joint portion 10g so that no large pits are generated on the main surface 10m. Thus, the first group III nitride crystal 10 is obtained.

  Here, in the first crystal growth step, since the first group III nitride crystal is grown by the liquid phase growth method, the crystal growth proceeds under conditions closer to the equilibrium condition than the vapor phase growth method. Therefore, it is considered that no pits are generated on the crystal growth surface.

  The liquid phase growth method used in the first crystal growth step can grow the first group III nitride crystal 10 integrated on the main surface 1m of the plurality of seed crystal substrates 1, and the main surface 10m. The method is not particularly limited as long as it does not generate pits, but a high nitrogen pressure solution method, a flux method and the like are preferable from the viewpoint of growing a group III nitride crystal having high crystallinity. The first crystal growth step can also be performed by an ammothermal method similar to the liquid phase growth method.

  Here, the high nitrogen pressure solution method uses a group III element raw material and a nitrogen raw material gas to grow a crystal under conditions of a crystal growth temperature of about 1400 ° C. to 1700 ° C. and a nitrogen raw material gas pressure of about 1200 MPa to 2000 MPa. On the other hand, the flux method uses a flux raw material in addition to a group III element raw material and a nitrogen raw material gas, under conditions of a crystal growth temperature of about 600 ° C. to 1400 ° C. and a nitrogen raw material gas pressure of about 0.1 MPa to 10 MPa. Crystal growth. For this reason, from the viewpoint of reducing the crystal growth temperature and the crystal growth pressure, the flux method is more preferable than the high nitrogen pressure solution method.

  The group III element raw material refers to a group III element that constitutes a group III nitride crystal to be grown, and includes group III elements and their contents. Nitrogen source gas refers to a gas that is a source of nitrogen constituting the group III nitride crystal to be grown, and includes nitrogen gas and nitrogen-containing gas. The flux raw material refers to a raw material of a flux that serves as a solvent for the group III element in the group III element raw material, and includes a flux and its contents. The flux is not particularly limited, but is preferably at least one metal element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and transition metal elements. For example, when the group III element is Ga, alkali metal elements such as Na and Li, and alkaline earth metal elements such as Ca are preferably used. When the group III element is Al, transition metal elements such as Cu, Ti, Fe, Mn, and Cr are preferably used.

  Here, with reference to FIG. 4, the growth method of the 1st group III nitride crystal 10 by the flux method is demonstrated. As shown in FIG. 4, in the flux method crystal growth apparatus 100, a crystal growth container 110 is disposed in a crystal growth chamber 120 having a gas supply port 120 e, and the crystal growth chamber 120 is disposed around the crystal growth chamber 120. In addition, a heater 130 for heating the crystal growth vessel 110 is provided.

  First, the plurality of seed crystal substrates 1 are arranged in the crystal growth vessel 110 such that their main surfaces 1m are parallel to each other and their side surfaces 1s are adjacent to each other. Next, a group III element raw material and a flux raw material are placed in the crystal growth vessel 110. Next, the nitrogen source gas 65 is supplied from the gas supply port 120e of the crystal growth chamber 120 to the crystal growth vessel 110 in the crystal growth chamber 120, and the crystal growth vessel 110 is heated by the heater 130, whereby the group III element source and the flux are supplied. The raw material is melted to form a melt 63 containing a group III element and a flux, and the nitrogen raw material gas 65 is dissolved in the melt 63. Thus, the first group III nitride crystal 10 grows on the main surface 1 m by bringing the solution 67 in which the nitrogen source gas 65 is dissolved in the melt 63 into contact with the main surfaces 1 m of the plurality of seed crystal substrates 1. .

(Second crystal growth step)
Referring to FIG. 1C, the III-nitride crystal growth method of the present embodiment is followed by the HVPE (hydride vapor phase epitaxy) method on the main surface 10 m of the first III-nitride crystal 10. A second crystal growth step of growing the second group III nitride crystal 20 by the above. By this second crystal growth method, a large second group III nitride crystal 20 joined and integrated at the main surface 10m of the first group III nitride crystal 10 is obtained. Here, since pits are not generated on the main surface 10m of the first group III nitride crystal 10, the first group III nitride crystal 10 and the second group III nitride crystal 20 are integrated. No pits are generated on the main surface 30 m of the group III nitride crystal 30.

  Here, with reference to FIG. 5, the growth method of the 2nd group III nitride crystal 20 by HVPE method is demonstrated. As shown in FIG. 5, the HVPE apparatus 200 includes a reaction chamber 210, a group III element source gas generation chamber 220, and heaters 231, 232, 233 for heating the reaction chamber 210 and the group III element source gas generation chamber 220. Prepare. The reaction chamber 210 and the group III element source gas generation chamber 220 are provided with an HCl gas introduction pipe 222 for introducing the HCl gas 71 into the group III element source gas generation chamber 220. In the group III element source gas generation chamber 220, a group III element source boat 221 for placing the group III element source 72 therein is disposed, and the generated group III element source gas 73 is introduced into the reaction chamber 210. A group III element source gas introduction pipe 223 is provided. The reaction chamber 210 is provided with a nitrogen source gas introduction pipe 213 for introducing the nitrogen source gas 75 into the reaction chamber 210 and a gas discharge pipe 215 for discharging the exhaust gas 79 from the reaction chamber 210. In the reaction chamber 210, a crystal holder 219 for arranging the first group III nitride crystal 10 for growing the second group III nitride crystal 20 is arranged. Although there is no restriction | limiting in particular in the reaction tube which forms the reaction chamber 210, From a viewpoint that a big reaction tube can be produced easily, a quartz reaction tube is used preferably.

  First, the HCl gas 71 is introduced into the group III element source gas generation chamber 220 through the HCl gas introduction pipe 222. In the group III element source gas generation chamber 220, a group III element source boat 221 containing a group III element source 72 is disposed. The group III element source boat 72 reacts with the HCl gas 71 to generate a group III element. A group III element chloride gas which is a source gas 73 is generated.

This group III element source gas 73 is introduced from the group III element source gas generation chamber 220 into the reaction chamber 210 through the group III element source gas introduction pipe 223. Further, NH ₃ gas which is nitrogen source gas 75 is introduced into reaction chamber 210 through nitrogen source gas introduction pipe 213. In the reaction chamber 210, the group III element source gas 73 reacts with the nitrogen source gas 75 to react with the second surface on the main surface 10 m of the first group III nitride crystal 10 disposed on the crystal holder 219 in the crystal growth portion. The group III nitride crystal 20 grows. Excess gas is discharged as exhaust gas 79 from the reaction chamber 210 through the gas discharge pipe 215. At this time, a carrier gas is used in combination to efficiently transport the group III element source gas and the nitrogen source gas or to adjust the partial pressure of each source gas. As the carrier gas, hydrogen gas (H ₂ gas), nitrogen gas (N ₂ gas), or the like is used.

  Here, from the viewpoint of efficiently growing the second group III nitride crystal 20 on the entire main surface 10m of the first group III nitride crystal 10, a source gas introduction unit (introducing HCl gas in the reaction chamber 210). The portion where the pipe 222, the group III element source gas generation chamber 220, the group III element source gas introduction pipe 223, and the nitrogen source gas introduction pipe 213 are arranged, and the vicinity thereof, which are mainly heated by the heaters 231 and 232. The atmospheric temperature is about 800 ° C. or more and 900 ° C. or less, and the crystal growth portion (the portion where the crystal holder 219 is disposed in the reaction chamber 210 and its vicinity) The atmospheric temperature of the portion heated by the heater 233 (the same applies hereinafter) is adjusted to about 1000 ° C. to 1300 ° C.

  Thus, the second group III nitride crystal 20 grows on the main surface 10 m of the first group III nitride crystal 10, and the first group III nitride crystal 10 and the second group III nitride crystal 20 are grown. And a large group III nitride crystal 30 with no generation of pits on the main surface 30 m is obtained.

[Formation of Group III Nitride Crystal Substrate]
Referring to FIGS. 1C and 1D, a group III nitride crystal substrate according to another embodiment of the present invention includes first group III nitride crystal 10 obtained by the above growth method and It is obtained by processing a group III nitride crystal 30 in which two group III nitride crystals 20 are integrated. Since the group III nitride crystal 30 is large and does not generate pits on the main surface 30m, it can be efficiently processed into a large group III nitride crystal substrate 30x, 30y, 30z with a high yield.

  The method for processing the group III nitride crystal substrate is not particularly limited, and as an example, the first group III nitride crystal 10 and the second group III formed on the main surface 1m of the plurality of seed crystal substrates 1 are used. There is a method in which a plurality of seed crystal substrates 1 are removed from a group III nitride crystal 30 integrated with a nitride crystal 20 to form a group III nitride crystal substrate 30x. The method for removing the seed crystal substrate 1 is not particularly limited, and examples thereof include grinding, dry etching, and wet etching. Further, the group III nitride crystal substrate 30y can be obtained by planarizing the main surface of the group III nitride crystal substrate 30x. The method for planarizing the main surface of the group III nitride crystal substrate 30x is not particularly limited, and examples thereof include grinding, polishing, dry etching, and wet etching.

  Referring to FIGS. 1D and 2C, group III nitride crystal 40 obtained by the conventional growth method has pits 40p on its main surface 40m, whereas in the above embodiment, The group III nitride crystal 30 obtained by growth does not generate pits on the main surface 30m. Therefore, the thickness of the group III nitride crystal substrate 30y obtained from the group III nitride crystal 30 can be increased with a high yield compared to the group III nitride crystal substrate 40y obtained from the group III nitride crystal 40.

  Further, as another example of the method of processing the group III nitride crystal substrate, the group III nitride crystal 30 is sliced by a plurality of surfaces 30v and 30w substantially parallel to the main surface 1m of the seed crystal substrate 1. A plurality of group III nitride crystal substrates 30z. Examples of the method for slicing the group III nitride crystal 30 include an inner peripheral blade, an outer peripheral blade, and a wire saw. Furthermore, the main surface of the obtained group III nitride crystal substrate 30z can be planarized. The method for planarizing the main surface of the substrate is not particularly limited, and examples thereof include polishing, dry etching, and wet etching.

  Referring to FIGS. 1D and 2C, as described above, group III nitride crystal 40 has pits 40p on its main surface 40m, while group III nitride crystal 30 has No pits are generated on the main surface 30m. For this reason, the yield of the group III nitride crystal substrate 30z obtained from the group III nitride crystal 30 is improved as compared with the group III nitride crystal substrate 40z obtained from the group III nitride crystal 40, and the number of the substrates can be increased.

Example 1
1. Preparation of Seed Crystal Substrate Referring to FIG. 1A, a GaN seed crystal is cut out with a wire saw in a plane parallel to the (0001) plane to form a plurality of wafers, and these wafers are oriented in the <1-100> direction. And by cutting with a wire saw in a two-dimensional direction of <11-20> direction, and polishing those cut surfaces by CMS (Chemical Mechanical Polishing), the plane orientation of the main surface 1m is inclined from the (0001) plane. The angle is 0.2 ° or less, the main surface 1 m is a square of 30 mm × 30 mm, and the plane orientation of the plurality of side surfaces is inclined from any one of {1-100} plane and {11-20} plane Nine GaN seed crystal substrates 1 having an angle of 0.2 ° or less and a thickness of 400 μm were prepared. Here, the plane orientations of the main surface and the plurality of side surfaces of each GaN seed crystal substrate were measured by X-ray diffraction. Further, the average roughness Ra of the main surface and the plurality of side surfaces of each GaN seed crystal substrate was 50 nm or less as measured by AFM.

2. Arrangement of Seed Crystal Substrate Referring to FIGS. 1A and 3, nine GaN seed crystal substrates 1 are adjacent to each other such that their main surfaces 1m are parallel to each other and their side surfaces 1s are in contact with each other. A total of nine sheets were arranged in the <1-100> direction and the <11-20> direction. Here, the nine GaN seed crystal substrates were arranged so that their <0001> direction, <1-100> direction, and <11-20> direction were substantially the same. The nine arranged GaN seed crystal substrates were fixed with an aluminum oxide jig.

3. First Crystal Growth Referring to FIGS. 1B and 4, the nine sheets fixed to the bottom surface of an aluminum oxide crucible which is a crystal growth vessel 110 of a flux method crystal growth apparatus 100 with an aluminum oxide jig. The GaN seed crystal substrates (seed crystal substrate 1) were arranged with their main surfaces 1m facing upward. Next, 200 g of metal Ga (group III element raw material) and 150 g of metal Na (flux raw material) are put in an aluminum oxide crucible (crystal growth vessel 110), and heated to 800 ° C., whereby a GaN seed crystal substrate is obtained. A Ga—Na melt (melt 63 containing a group III element and a flux) in contact with the main surface 1 m of (seed crystal substrate 1) was formed. Next, nitrogen gas (nitrogen raw material gas 65) was supplied to the Ga—Na melt (melt 63) in the aluminum oxide crucible (crystal growth vessel 110) to maintain the nitrogen gas pressure at 5 MPa for 200 hours. Thus, a solution 67 in which nitrogen gas (nitrogen raw material gas 65) is dissolved in a Ga—Na melt (melt 63) in contact with the main surface 1m of the GaN seed crystal substrate (seed crystal substrate 1) is formed, and the GaN seed crystal is formed. On the main surface 1m of the substrate (seed crystal substrate 1), a first GaN crystal (first group III nitride crystal 10) having an average thickness of 500 μm with no generation of pits on the main surface 10m was grown.

  Next, the main surface 10m of the first GaN crystal (first group III nitride crystal 10) was polished by CMP to be mirror-finished.

4). Second Crystal Growth Referring to FIGS. 1C and 5, on the crystal holder 219 in the reaction chamber 210 of the HVPE apparatus 200, the first GaN crystal (first III) having the main surface 10 m mirrored. The group nitride crystal 10) is arranged, and the reaction chamber 210 is composed of HCl gas 71 having a flow rate of 100 ml / min and NH ₃ gas having a flow rate of 250 ml / min (nitrogen source gas 75) as a carrier gas, and using N ₂ gas as a total gas The flow rate is 4000 ml / min, the generation temperature of GaCl gas (Group III element source gas 73) is 850 ° C., the crystal growth temperature is 1120 ° C., and the first GaN crystal (first Group III nitride crystal 10) is formed. A second GaN crystal (second group III nitride crystal 20) was grown on the main surface 10 m for 5 hours (ie, to a thickness of 1000 μm) at a crystal growth rate of 200 μm / hr. Thus, a GaN crystal in which pits are not generated on the main surface 30m in which the first GaN crystal (first group III nitride crystal 10) and the second GaN crystal (first group III nitride crystal 20) are integrated. (Group III nitride crystal 30) was obtained.

  On the main surface 30m of the obtained GaN crystal (Group III nitride crystal 30), no facets and pits were observed when observed in detail with an optical microscope. Further, this GaN crystal (Group III nitride crystal 30) was observed in detail as a light emission intensity distribution image using a fluorescence microscope, but no facet growth crystal region was observed at all. That is, in the growth of the first GaN crystal by the flux method, the crystal growth using either the (1-100) plane or the (11-20) plane as the crystal growth plane, that is, the main surface 1m of the GaN seed crystal substrate. Crystal growth using the (0001) plane as the crystal growth surface after the partial crystals 10u grown on the main surface 1m of each GaN seed crystal substrate are joined and integrated at the joint 10g by crystal growth in parallel directions. That is, it is considered that the crystal growth has shifted to a direction perpendicular to the main surface 1 m of the GaN seed crystal substrate.

5. Formation of Crystal Substrate Referring to FIG. 1D, after the GaN crystal (Group III nitride crystal 30) is taken out from the reaction chamber of the HVPE apparatus, the GaN crystal is converted into a GaN seed crystal substrate (seed crystal substrate 1). Each of the surfaces 30v and 30w parallel to the main surface 1m was sliced with a wire saw, and the sliced surface was polished by CMP to obtain four GaN crystal substrates (GaN crystal substrate 30z) having a thickness of 200 μm.

(Comparative Example 1)
1. Preparation of Seed Crystal Substrate With reference to FIG. 2A, nine GaN seed crystal substrates 1 similar to those in Example 1 were prepared.

2. Arrangement of Seed Crystal Substrate With reference to FIGS. 2A and 3, nine GaN seed crystal substrates 1 were arranged in the same manner as in Example 1 and fixed with an aluminum oxide jig.

3. Crystal Growth Referring to FIG. 2B, the nine GaN seed crystal substrates (seed crystal substrate 1) fixed on the crystal holder 219 in the reaction chamber 210 of the HVPE apparatus 200 with a jig made of aluminum oxide. Were placed with their main surface 1 m facing up. Next, in the same manner as in Example 1, a GaN crystal (Group III nitride crystal 40) having a thickness of 1000 μm was grown.

The main surface 40 m of the obtained GaN crystal has a facet of (1-10 × ₁ ) plane (x ₁ = 1 or 2) above the joint 40 g of the partial crystal 40 u grown on each GaN seed crystal substrate 1. Pits 40p formed by 40f were generated at a rate of 25 / cm ² . Further, when the cross section of the GaN crystal was observed as a light emission intensity distribution image using a fluorescence microscope, (1-10 × ₁₎ is present in the vicinity of the junction 40g of the partial crystal 40u grown on the GaN seed crystal substrate _1. ) A facet-grown crystal region 40uf grown with the facet 40f of the plane (x ₁ = 1 or 2) as the crystal growth surface was observed.

4). Formation of Crystal Substrate Referring to FIG. 2C, after the GaN crystal (Group III nitride crystal 40) is taken out from the reaction chamber of the HVPE apparatus, the GaN crystal is converted into a GaN seed crystal substrate (seed crystal substrate 1). Two GaN crystal substrates (GaN crystal substrate 40z) having a thickness of 200 μm were obtained by slicing with a wire saw on planes 40v and 40w parallel to 1 m of the main surface and polishing the slice surface by CMP.

(Comparative Example 2)
1. Preparation of Seed Crystal Substrate With reference to FIG. 2A, nine GaN seed crystal substrates 1 similar to those in Example 1 were prepared.

2. Arrangement of Seed Crystal Substrate With reference to FIGS. 2A and 3, nine GaN seed crystal substrates 1 were arranged in the same manner as in Example 1 and fixed with an aluminum oxide jig.

3. Crystal Growth Referring to FIG. 2B, a 1000 μm-thick GaN crystal (Group III) is formed in the same manner as in Comparative Example 1 except that the crystal growth temperature is 1220 ° C. and the crystal growth rate is 120 μm / hr. Nitride crystals 40) were grown.

The main surface 40m of the obtained GaN crystal has a facet 40f of (1-10x ₂ ) plane (x ₂ = 1 or 2) on the joint 40g of the partial crystal 40u grown on each GaN seed crystal substrate 1. Pits 40p formed at a rate of 4 / cm ² . Further, when the cross section of the GaN crystal was observed as a light emission intensity distribution image using a fluorescence microscope, (1-10 × _{2) in} the vicinity of the junction 40g of the partial crystal 40u grown on the GaN seed crystal substrate 1. ) A facet-grown crystal region 40uf grown with the facet 40f of the plane (x ₂ = 1 or 2) as the crystal growth surface was observed.

4). Formation of Crystal Substrate Referring to FIG. 2C, after the GaN crystal (Group III nitride crystal 40) is taken out from the reaction chamber of the HVPE apparatus, GaN having a thickness of 200 μm is obtained in the same manner as in Comparative Example 1. Two crystal substrates (GaN crystal substrate 40z) were obtained.

  Referring to FIG. 1 and FIG. 2, when Example 1 is compared with Comparative Examples 1 and 2, the first group III nitridation is performed on the main surface 1m of the plurality of seed crystal substrates 1 arranged by the liquid phase growth method. After growing the crystal 10, the second group III nitride crystal 20 is grown on the main surface 10 m of the first group III nitride crystal 10 by the HVPE (hydride vapor phase epitaxy) method. It was found that a large group III nitride crystal 30 having no pits was obtained on the main surface 30 m where the group III nitride crystal 10 and the second group III nitride crystal 20 were integrated. In addition, since the group III nitride crystal 30 has no pits on its main surface 30m, it has been found that the group III nitride crystal substrates 30x, 30y, and 30z with high yield and high crystallinity can be obtained.

  On the other hand, with reference to FIG. 2, with reference to comparative example 1 and comparative example 2, group III nitride crystal 40 is formed on main surface 1m of a plurality of seed crystal substrates 1 arranged by HVPE. It can be seen that even if the crystal growth temperature is raised, the rate of generation of pits 40p generated on the main surface 40m of the growing group III nitride crystal 40 can be reduced, but the generation of pits cannot be eliminated. It was.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 seed crystal substrate, 1 m, 10 m, 30 m, 40 m main surface, 1 s side surface, 10 first group III nitride crystal, 10 g, 40 g junction, 10 u, 40 u partial crystal, 20 second group III nitride crystal 30, 40 group III nitride crystal, 30v, 30w, 40v, 40w plane, 30x, 30y, 30z, 40x, 40y, 40z group III nitride crystal substrate, 40f facet, 40p pit, 40uf facet growth crystal region, 40um Main surface crystal growth region, 63 melt, 65,75 nitrogen source gas, 67 solution, 71 HCl gas, 72 group III element source material, 73 group III element source gas, 79 exhaust gas, 100 flux method crystal growth apparatus, 110 crystal growth Container, 120 crystal growth chamber, 120e gas supply port, 130, 231, 232, 23 Heater, 200 HVPE apparatus, 210 reaction chamber, 213 nitrogen source gas introduction pipe, 215 gas discharge pipe, 219 crystal holder, 220 group III element source gas generation chamber, 221 group III element source boat, 222 HCl gas introduction pipe, 223 III Group element source gas introduction pipe.

Claims (3)

Preparing a plurality of seed crystal substrates having a main surface of a predetermined plane orientation and a plurality of side surfaces;
Arranging the plurality of seed crystal substrates such that their main surfaces are parallel to each other and their side surfaces are adjacent to each other;
A first crystal growth step of growing a first group III nitride crystal on a main surface of the plurality of seed crystal substrates arranged by a liquid phase growth method;
A second crystal growth step of growing a second group III nitride crystal on the main surface of the first group III nitride crystal by a hydride vapor phase growth method,
The first group III nitride crystal is grown so that each partial crystal grown on the main surface of each seed crystal substrate is integrated,
The method for growing a group III nitride crystal, wherein the second group III nitride crystal is grown so as to be integrated with the first group III nitride crystal.   The method for growing a group III nitride crystal according to claim 1, wherein the seed crystal substrate is a GaN seed crystal substrate, and the liquid phase growth method is a flux method.   A group III nitride crystal obtained by processing the group III nitride crystal obtained by integrating the first group III nitride crystal and the second group III nitride crystal obtained by the growth method according to claim 1 or 2. Group nitride crystal substrate.

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