Method for manufacturing group-III nitride crystal and group-III nitride crystal

Abstract

To provide a method for producing a group III nitride crystal that can reduce a material loss generated in producing a group III nitride crystal and produce a high-quality group III nitride crystal.SOLUTION: A method for producing a group III nitride crystal includes the steps of: providing a seed substrate; forming surface roughness of the seed substrate; and growing a group III nitride crystal on the seed substrate by supplying a group III element oxide gas and a nitrogen element-containing gas to the substrate.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a group III nitride crystal and a group III nitride crystal manufactured by this manufacturing method.

Background Art

[0002] Group III nitride crystals such as GaN are expected to be applied to next-generation optical devices such as high-power LEDs (light-emitting diodes) and LDs (laser diodes), and next-generation electronic devices such as high-power power transistors mounted on EVs (electric vehicles) and PHVs (plug-in hybrid vehicles). As a method for manufacturing a group III nitride crystal, an Oxide Vapor Phase Epitaxy (OVPE) method using a group III oxide as a raw material is used (see, for example, Patent Document 1). An example of the reaction system in the OVPE method is as follows. Ga is heated, and in this state, H 2 2O gas is introduced. The introduced H 2 2O gas reacts with Ga to generate Ga 2 2O gas (see the following formula (I)). Then, NH 3 3 gas is introduced and reacted with the generated Ga 2 2O gas to generate a GaN crystal on a seed substrate (see the following formula (II)). 2Ga(l)+H 2 2O(g)→Ga 2 2O(g)+H 2 (g)···(I) Ga 2 2O(g)+2NH 3 (g)→2GaN(s)+H 2 2O(g)+2H 2 (g)···(II)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the manufacturing method described in Patent Document 1, hexagonal or dodecagonal inverted pyramid-shaped pits with {10-1n} or {11-2m} as the main planes are generated from the regions starting from dislocation defects, but pits from other regions are less likely to occur. Therefore, when using a high-quality seed substrate with a low dislocation density, since there are few dislocation defects, the number of pits generated in the regions starting from dislocation defects decreases, and the density of pits generated in the growth layer of the group III nitride crystal becomes small.

[0005] When the pit density is small, the unevenness on the surface of the grown group III nitride crystal tends to be large. That is, the size of each pit tends to be large. For this reason, when growing a group III nitride crystal on a seed substrate having the lattice plane (0001) as the main plane, the orientation of the tilt component may decrease. The orientation of the tilt component is, for example, the strain of the (0001) plane in the case of a crystal having the lattice plane (0001) as the main plane. A conceptual diagram of the orientation of the tilt component in the case of a small and a large pit density caused by dislocation defects is shown in FIG. 1. FIG. 1(a) is a cross-sectional conceptual diagram showing the relationship between the dislocation defects of the grown crystal on the low dislocation density substrate and the strain of the lattice plane. FIG. 1(b) is a cross-sectional conceptual diagram showing the relationship between the dislocation defects of the grown crystal on the high dislocation density substrate and the strain of the lattice plane. As shown in FIGS. 1(a) and (b), the grown crystal on the low dislocation density substrate tends to have a large strain of the lattice plane and a low orientation of the tilt component.

[0006] In addition, when manufacturing a group-III nitride substrate from a grown group-III nitride crystal and fabricating a device on the group-III nitride substrate, a device layer of a group-III nitride crystal is formed on the group-III nitride substrate. This device layer of the group-III nitride crystal is affected by the orientation of the group-III nitride substrate. Therefore, when the orientation of the tilt component of the group-III nitride substrate is low, the orientation of the device layer of the group-III nitride crystal also becomes low. When the orientation of the tilt component of the device layer is low, when the device is driven, the performance of the device may not be fully exhibited. That is, in order to obtain a high-quality group-III nitride crystal, it is necessary to increase the orientation of the tilt component.

[0007] In addition, when the density of pits is small, as shown in FIG. 1(a) above, the surface unevenness of the grown group-III nitride crystal tends to be large. When cutting out a wafer from the grown group-III nitride crystal, generally, since it is necessary to remove this surface unevenness, if the surface unevenness is large, there is a possibility that the portion to be removed from the grown group-III nitride crystal will increase. That is, there is a problem that the lower the dislocation density of the seed substrate, the greater the material loss when manufacturing a group-III nitride substrate from a group-III nitride crystal. On the other hand, as shown in FIG. 1(b), when using a seed substrate with a high dislocation density, the surface unevenness becomes small and the portion to be removed becomes small, but in this case, since it has a high dislocation density, it becomes low quality. Thus, it is not easy to reduce the material loss when manufacturing a group-III nitride substrate and to manufacture a high-quality group-III nitride crystal.

[0008] The present disclosure has been made in view of the above problems, and an object thereof is to provide a manufacturing method and a group-III nitride substrate capable of reducing the material loss when manufacturing a group-III nitride substrate and obtaining a high-quality group-III nitride crystal.

Means for Solving the Problems

[0009] The method for manufacturing a group III nitride crystal of the present disclosure includes a step of preparing a seed substrate, a step of forming surface roughness on the surface of the seed substrate, and a step of supplying a group III element oxide gas and a nitrogen element-containing gas to grow a group III nitride crystal on the seed substrate.

[0010] The group III nitride crystal of the present disclosure has a plurality of petal-shaped light-emitting regions and a plurality of dislocation defects on a smooth surface after surface polishing. The number of these petal-shaped light-emitting regions is larger than the number of dislocation defects.

Advantages of the Invention

[0011] According to the method for manufacturing a group III nitride crystal according to the present disclosure, it is possible to reduce material loss when manufacturing a group III nitride substrate and to manufacture a high-quality group III nitride crystal.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0013] The method for manufacturing a group III nitride crystal according to the first aspect includes a step of preparing a seed substrate, a step of forming surface roughness on the seed substrate, and a step of supplying a group III element oxide gas and a nitrogen element-containing gas to grow a group III nitride crystal on the seed substrate.

[0014] The method for manufacturing a group III nitride crystal according to the second aspect may be implemented in the temperature rising process of 900°C or higher and less than 1500°C before growing the group III nitride crystal in the step of forming surface roughness on the seed substrate in the first aspect.

[0015] The group III nitride crystal according to the third aspect is a group III nitride crystal having, on a smooth surface after surface polishing, a plurality of petal-shaped light-emitting regions and a plurality of dislocation defects, and the number of petal-shaped light-emitting regions is larger than the number of dislocation defects.

[0016] The group III nitride crystal according to the fourth aspect may be such that in the third aspect, the petal-shaped light-emitting regions can be confirmed by photoluminescence, and the dislocation defects can be confirmed by a surface optical microscope image after alkaline melt etching.

[0017] Hereinafter, the method for manufacturing a group III nitride crystal and the group III nitride crystal according to the embodiments will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

[0018] (Embodiment 1) Outline of the Manufacturing Apparatus for Group III Nitride Crystal First, an overview of the apparatus for manufacturing a group-III nitride crystal used in the method for manufacturing a group-III nitride crystal according to Embodiment 1 will be described with reference to FIG. 3. FIG. 3 is a schematic cross-sectional view showing the cross-sectional configuration of the apparatus 10 for manufacturing a group-III nitride crystal. In FIG. 3, the sizes, ratios, etc. of the respective constituent members may be different from the actual ones. The apparatus 10 for manufacturing a group-III nitride crystal includes a raw material chamber 100 and a growth chamber 110. Inside the raw material chamber 100, a raw material reaction chamber 101 is disposed, and a raw material boat 104 on which a starting group-III element source 105 is placed is disposed inside the raw material reaction chamber 101. A reactive gas supply pipe 103 for supplying a gas that reacts with the starting group-III element source 105 is connected to the raw material reaction chamber 101. The raw material reaction chamber 101 has a group-III element oxide gas discharge port 107 for discharging the generated group-III element oxide gas. When the starting group-III source is an oxide, a reducing gas is used as the reactive gas. When the starting group-III source is a metal, an oxidizing gas is used as the reactive gas.

[0019] Further, a first carrier gas supply port 102 for supplying a first carrier gas is connected to the raw material chamber 100. The first carrier gas supplied from the first carrier gas supply port 102 and the group-III element oxide gas discharged from the group-III element oxide gas discharge port 107 flow from the gas discharge port 108 through the connection pipe 109 to the growth chamber 111. The first carrier gas and the group-III element oxide gas are supplied into the growth chamber 111 from a gas supply port 118 connected to the growth chamber 111.

[0020] The growth chamber 111 has a gas supply port 118, a third carrier gas supply port 112, a nitrogen element-containing gas supply port 113, a second carrier gas supply port 114, and an exhaust port 119. The growth chamber 111 includes a substrate susceptor 117 on which a seed substrate 116 is placed.

[0021] <Overview of the method for manufacturing a group-III nitride crystal> The outline of the method for manufacturing a group-III nitride crystal according to Embodiment 1 will be described with reference to the flowchart of FIG. 2 and FIG. 3. FIG. 2(a) shows a time-series flowchart of the manufacturing method. FIG. 2(b) shows each functional unit from the upstream to the downstream in the manufacturing apparatus used in this manufacturing method as steps. This method for manufacturing a group-III nitride crystal includes a step of preparing a seed substrate, a step of forming surface roughness on the seed substrate, and a step of supplying a group-III element oxide gas and a nitrogen element-containing gas to grow a group-III nitride crystal on the seed substrate.

[0022] Each step will be described below in order along the time series. (0) In the seed substrate preparation step of preparing the seed substrate 116, the seed substrate 116 is placed on the substrate susceptor 117. (1) In Embodiment 1, the method for manufacturing a group-III nitride crystal has a temperature-raising step. In the temperature-raising step, the growth chamber 111 is heated to 100°C or higher and lower than 500°C in an inert gas atmosphere. (2) In Embodiment 1, the method for manufacturing a group-III nitride crystal has a decomposition protection temperature-raising step. In the decomposition protection temperature-raising step, the growth chamber 111 is heated to 500°C or higher and lower than 1000°C in an NH 3 gas atmosphere.

[0023] (3) In the surface roughness formation step of forming surface roughness on the seed substrate 116, the growth chamber 111 is heated to 900°C or higher and lower than 1500°C in an NH 3 gas atmosphere.

[0024] (4) In the growth step of growing a group-III nitride crystal on the seed substrate 116, a group-III element oxide gas is generated in the raw material chamber 100 and supplied to the growth chamber 111, and a nitrogen element-containing gas is supplied to the growth chamber 111 to generate a group-III nitride crystal on the seed substrate 116.

[0025] As shown in Fig. 2(b), this growth process includes a reactive gas supply step, a group III element oxide gas generation step, a group III element oxide gas supply step, a nitrogen element-containing gas supply step, a group III nitride crystal generation step, and a residual gas discharge step. Each step included in the growth process may be performed simultaneously in the apparatus for manufacturing a group III nitride crystal. (4-1) In the reactive gas supply step, a reactive gas is supplied to the raw material reaction chamber. (4-2) In the group III element oxide gas generation step, a starting group III element source is reacted with a reactive gas (a reducing gas when the starting group III element source is an oxide, and an oxidizing gas when it is a metal) to generate a group III element oxide gas. (4-3) In the group III element oxide gas supply step, the group III element oxide gas produced in the group III element oxide gas generation step is supplied to the growth chamber. (4-4) In the nitrogen element-containing gas supply step, a nitrogen element-containing gas is supplied to the growth chamber. (4-5) In the group III nitride crystal generation step, the group III element oxide gas supplied into the growth chamber in the group III element oxide gas supply step is reacted with the nitrogen element-containing gas supplied into the growth chamber in the nitrogen element-containing gas supply step, and a group III nitride crystal is grown on the seed substrate. (4-6) In the residual gas discharge step, unreacted gas that does not contribute to the production of the group III nitride crystal is discharged outside the chamber.

[0026] (5) In the first embodiment, the method for manufacturing a group III nitride crystal includes a decomposition protection temperature reduction step. In the decomposition protection temperature reduction step, in order to suppress the decomposition of the group III nitride crystal grown on the seed substrate 116, the temperature of the raw material chamber 100 and the growth chamber 111 is reduced to 500 °C while supplying NH 3 gas. (6) In the first embodiment, the method for manufacturing a group III nitride crystal includes a temperature reduction step. In the temperature reduction step, the temperature of the raw material chamber 100 and the growth chamber 111 is reduced to less than 100 °C in an inert gas atmosphere. (7)In the first embodiment, the method for manufacturing a group III nitride crystal includes a take-out step. In the take-out step, the seed substrate 116 on which the group III nitride crystal has grown is taken out from the growth chamber 111.

[0027] <Details of the method for manufacturing a group III nitride crystal and the manufacturing apparatus> Referring to FIGS. 2 and 3, the method for manufacturing a group III nitride crystal according to the first embodiment will be described in detail. In the first embodiment, metallic Ga is used as the starting group III element source 105, but it is not limited thereto. For example, Al or In may be used. (0) First, a seed substrate 116 is prepared. As the seed substrate 116, for example, gallium nitride, gallium arsenide, silicon, sapphire, silicon carbide, zinc oxide, gallium oxide, ScAlMgO 4 can be used. In the first embodiment, gallium nitride is used as the seed substrate 116. (1) In the temperature-raising step, the temperature of the growth chamber is raised to a temperature at which the seed substrate 116 does not decompose in an inert gas atmosphere. In the production of group III nitride crystals by the OVPE method, heating is performed in an inert gas (for example, N 2 gas) atmosphere up to about 500°C. (2) In the decomposition-protected temperature-raising step, the temperature is raised while suppressing the decomposition of the seed substrate 116 in a nitrogen element-containing gas atmosphere. In the production of group III nitride crystals by the OVPE method, from 500°C to less than 900°C, heating is performed in a state where an inert gas and a nitrogen element-containing gas NH 3 gas are mixed. The reason for mixing NH 3 is to prevent the seed substrate 116 from decomposing due to the desorption of N atoms.

[0028] (3) In the surface roughening step of forming the surface roughness of the seed substrate 116, the surface roughness is formed on the seed substrate 116 in order to increase the density of pits generated on the surface of the group III nitride crystal to be grown and to reduce the size of each pit. When gallium nitride having a lattice plane (0001) as the main surface is used for the seed substrate, pits are generated on the surface of the group III nitride crystal grown by the OVPE method starting from the dislocation defects of the seed substrate. A pit is a hammer-shaped depression covered by a surface having an angle inclined from the (0001) plane, and is composed of surfaces inclined from a-plane or m-plane such as {10-11} and {11-22}. Therefore, when gallium nitride with a low dislocation density is used as the seed substrate, the pit density is low, and the surface unevenness is likely to increase. For this reason, when cutting out a group III nitride substrate from a group III nitride crystal to form a wafer, the unevenness to be removed becomes large, and there is a risk that the material loss increases.

[0029] FIG. 4(a) is a cross-sectional conceptual diagram showing the relationship with the surface unevenness when there is no surface roughening step in the method for manufacturing a group III nitride crystal. FIG. 4(b) is a cross-sectional conceptual diagram showing the relationship with the surface unevenness when there is a surface roughening step in the method for manufacturing a group III nitride crystal. As shown in FIG. 4(a), when the surface roughness is not formed, when using a seed substrate with a low dislocation density, for example, a seed substrate with a dislocation density of 1×10 4 / cm 2 , pits 2 are generated at intervals of one per 100 μm square. That is, pits 2 with a diameter of 100 μm are generated. Considering the case where the oblique facet is formed by {10-11}, the depth of the pit 2 is 94 μm, and even when grown to a standard thickness of 400 μm during wafering, approximately 1 / 4 of that thickness becomes a region that cannot be used as a wafer. On the other hand, as shown in Fig. 4(b), before growing the group-III nitride crystal, by forming surface roughness on the seed substrate 116, it is possible to generate pits 2 in regions other than the dislocation defects 4. When surface roughness 6 is formed on the seed substrate 116, pits 2 can be generated even in regions without dislocation defects 4, so the overall number of pits 2 increases and the pit density becomes higher. Therefore, when the group-III nitride crystal is grown, the unevenness on its surface becomes smaller, and the waste area when cutting out the wafer can be reduced.

[0030] The process of forming this surface roughness is carried out using a manufacturing apparatus used for manufacturing group-III nitride crystals and can be introduced into a series of processes for growing group-III nitride crystals. In the manufacture of group-III nitride crystals by the OVPE method, in order to intentionally form surface roughness, a surface roughness formation process of heating in an atmosphere of only an inert gas and NH 3 gas at a state of 900 °C or higher and less than 1500 °C may be introduced. Thereby, the GaN crystal surface of the seed substrate 116 before starting the bulk growth of the group-III nitride crystal at a state of 1200 °C or higher can be made into a state where pits are generated even in regions other than dislocation defects. Incidentally, the surface roughness formation process may be carried out at the stage of preparing the seed substrate, or surface roughness may be formed by wet etching with an alkali or an acid. At this time, in order to suppress the decomposition of the nitrogen element-containing gas by the heat from the growth chamber 111, it is preferable to coat the outer walls of the nitrogen element-containing gas supply port 112 and the growth chamber 111 with a heat insulating material.

[0031] The second carrier gas may be supplied from the second carrier gas supply port 114 to the growth chamber 111 to control the concentrations of the group-III element oxide gas and the nitrogen element-containing gas. In this case, parasitic growth of the group-III nitride crystal on the furnace wall or the substrate susceptor 117 of the growth chamber 111 can be suppressed. Also, in order to suppress parasitic growth on the substrate susceptor 117, it is desirable that the material of the substrate susceptor 117 be an active metal. Furthermore, from the viewpoint of suppressing alloying with Ga, it is more desirable that the material of the substrate susceptor 117 be Mo or Pt. As the second carrier gas, an inert gas, or H 2 gas or the like can be used.

[0032] (4) In the growth process, a group III element oxide gas is generated in the raw material chamber 100 and supplied to the growth chamber 111, and a nitrogen element-containing gas is supplied to the growth chamber 111 to generate a group III nitride crystal on the seed substrate 116. Specifically, as shown in FIG. 2(b), the growth process includes a reactive gas supply process, a group III element oxide gas generation process, a group III element oxide gas supply process, a nitrogen element-containing gas supply process, a group III nitride crystal generation process, and a residual gas discharge process.

[0033] (4-1) In the reactive gas supply process, the reactive gas is supplied from the reactive gas supply pipe 103 to the raw material reaction chamber 101 in the raw material chamber 100. As described above, as the reactive gas, a reducing gas or an oxidizing gas can be used as necessary. In this embodiment, since metal Ga is used as the group III element source 105, H 2 O gas is used as the reactive gas. (4-2) In the group III element oxide gas generation process, the reactive gas supplied to the raw material reaction chamber 101 in the reactive gas supply process reacts with Ga which is the starting group III element source 105 to generate a group III element oxide gas, Ga 2 O gas. The generated Ga 2 O gas is discharged from the raw material reaction chamber 101 to the raw material chamber 100 via the group III element oxide gas discharge port 107. The discharged Ga 2 O gas is mixed with the first carrier gas supplied from the first carrier gas supply port 102 to the raw material chamber and supplied to the gas discharge port 108. In this embodiment, the raw material chamber 100 is heated by the first heater 106. When the raw material chamber 100 also serves as a rubbing part, the temperature of the raw material chamber 100 is set to Ga 2It is preferably 800 °C or higher from the viewpoint of the boiling point of the Group III oxide gas. Further, it is preferable that the temperature of the raw material chamber 100 is lower than that of the growth chamber 111. When heating the growth chamber with the second heater 115 as described later, it is preferable that the temperature of the raw material chamber 100 is, for example, less than 1800 °C. The starting Group III element source 105 is placed in a raw material boat 104 disposed in the raw material reaction chamber 101. The raw material boat 104 preferably has a shape that can increase the contact area between the reactive gas and the starting Group III element source. For example, in order to prevent the starting Group III element source 105 and the reactive gas from passing through the raw material reaction chamber 101 in a non-contact state, the raw material boat 104 is preferably in a multi-stage dish shape.

[0034] Note that the methods for generating the Group III oxide gas are roughly classified into a method of reducing the starting Group III element source 105 and a method of oxidizing the starting Group III element source 105. For example, in the reduction method, an oxide (for example, Ga 2 O 3 ) is used as the starting Group III element source 105, and a reducing gas (for example, H 2 gas, CO gas, CH 4 gas, C 2 H 6 gas, H 2 S gas, SO 2 gas) is used as the reactive gas. On the other hand, in the oxidation method, a non-oxide (for example, liquid Ga) is used as the starting Group III element source 105, and an oxidizing gas (for example, H 2 O gas, O 2 gas, CO gas, CO 2 gas, NO gas, N 2 O gas, NO 2 gas) is used as the reactive gas. In addition to the starting Group III element source 106, an In source and an Al source can be adopted as the starting Group III elements. As the first carrier gas, an inert gas, H 2 gas, etc. can be used.

[0035] (4-3) In the Group III oxide gas supply step, the Ga 2Oxygen gas is supplied to the growth chamber 111 via the gas outlet 108, the connecting pipe 109, and the gas supply port 118. When the temperature of the connecting pipe 109 connecting the raw material chamber 100 and the growth chamber 111 drops below the temperature of the raw material chamber 100, the reverse reaction of the reaction to produce the group III element oxide gas occurs, and the starting Ga source 105 precipitates in the connecting pipe 109. Therefore, the connecting pipe 109 is preferably heated to a higher temperature than the first heater 106 by the third heater 110 so as not to drop below the temperature of the raw material chamber 100.

[0036] (4-4) In the nitrogen element-containing gas supply step, the nitrogen element-containing gas is supplied from the nitrogen element-containing gas supply port 113 to the growth chamber 111. Examples of the nitrogen element-containing gas include NH 3 gas, NO gas, NO 2 gas, N 2 O gas, N 2 H 2 gas, N 2 H 4 gas and the like. In the group III nitride crystal formation step, the raw material gas supplied into the growth chamber through each supply step is reacted to grow group III nitride crystals on the seed substrate 116. The growth chamber 111 is preferably heated to a high temperature by the second heater 115 to the temperature at which the group III element oxide gas and the nitrogen element-containing gas react. At this time, the temperature of the growth chamber 111 is preferably controlled so as not to drop below the temperature of the raw material chamber 100 in order to prevent the reverse reaction of the reaction to produce the group III element oxide gas. The temperature of the growth chamber 111 heated by the second heater 115 is preferably 1000 ° C or higher and 1800 ° C or lower. Further, due to the Ga 2 O gas and the temperature fluctuation of the growth chamber 111 by the first carrier gas, it is desirable that the temperatures of the second heater 115 and the third heater 111 be the same.

[0037] (4-5) Through the group III element oxide supply process, the group III element oxide gas supplied to the growth chamber 111 and the nitrogen element-containing gas supplied to the growth chamber 111 through the nitrogen element-containing gas supply process are mixed upstream of the seed substrate 116, whereby the growth of group III nitride crystals can be carried out on the seed substrate 116 (group III nitride crystal generation process). (4-6) In the residual gas discharge process, unreacted group III element oxide gas, nitrogen element-containing gas, and the first carrier gas, second carrier gas, and third carrier gas are discharged from the exhaust port 119. Note that the reactive gas supply process, group III element oxide gas generation process, group III element oxide gas supply process, nitrogen element-containing gas supply process, group III nitride crystal generation process, and residual gas discharge process included in the growth process may be carried out simultaneously.

[0038] (5) In the decomposition protection temperature reduction process, the temperature is reduced while suppressing the decomposition of group III nitride crystals in a nitrogen element-containing gas atmosphere. In the production of group III nitride crystals by the OVPE method, cooling is carried out in a state where an inert gas and a nitrogen element-containing gas NH 3 gas are mixed until the temperature reaches 500 °C or lower. (6) In the temperature reduction process, the temperature is reduced to a temperature at which the group III nitride crystal can be taken out from the growth chamber in an inert gas atmosphere. (7) In the first embodiment, through the temperature reduction process, the seed substrate 116 on which group III nitride crystals have grown is taken out from the growth chamber 111 (taking-out process). As described above, high-quality group III nitride crystals with a high orientation of the tilt component can be obtained. In addition, material loss can be reduced when producing a group III nitride substrate from this group III nitride crystal.

[0039] (Overview of Examples and Comparative Examples) The growth of group III nitride crystals was carried out using the group III nitride crystal production apparatus which is the growth furnace shown in Fig. 3. Here, GaN was grown as the group III nitride crystal. As the starting group III element source, liquid Ga was used, and Ga was reacted with H 2 O gas which is a reactive gas, and the generated Ga2 O gas was used as the group III element oxide gas. NH 3 Gas is used, and H is used as the first carrier gas and the second carrier gas. 2 Gas and N 2 A mixture of gases was used. The growth time was 3 hours. The surface pit density was measured by observing the surface of the grown crystal with a scanning electron microscope (SEM) and counting the number of pits per unit area (pits / cm 2 The dislocation density of the seed substrate 116 was measured by counting the number of dislocations. 5 units / cm 2 The GaN substrate with the lattice plane (0001) as the main surface was used. In order to evaluate the crystal orientation of the tilt component, the X-ray rocking curve of the (0002) plane of the grown crystal was measured and evaluated from the half-width.

[0040] Example 1 The growth conditions were a substrate temperature of 1200°C and a source temperature of 1100°C. 2 O gas partial pressure was 0.00079 atm, H 2 O gas partial pressure was set to 0.00035 atm, and NH 3 Gas partial pressure: 0.15759 atm, H 2 Gas partial pressure: 0.71870atm, N 2 The gas partial pressure was set to 0.12257 atm. In addition, during the temperature rise process from 900°C to 1500°C, the Group III element oxide gas Ga 2 A surface roughening process without supplying O gas was introduced. As a result of GaN growth, the thickness of the growth layer was 189 μm. The pit density on the surface was 2.6 × 10 6 / cm 2 The average pit diameter was 6.2 μm and the pit depth was 5.8 μm. The half-width of the X-ray rocking curve of the (0002) plane was 51 arcsec.

[0041] Comparative Example 1 The growth conditions were the same as those in Example 1, but GaN crystal growth was performed during the temperature rise process from 900° C. to less than 1500° C., and the surface roughening process was not introduced. As a result of growing GaN, the thickness of the grown layer was 184 μm. The pit density on the surface was 1.1×10 5 / cm 2 . The average pit diameter was 30 μm, and the pit depth was 28.2 μm. Also, the full width at half maximum of the X-ray rocking curve for the (0002) plane was 79 arcsec.

[0042] (Summary of Examples and Comparative Examples) Fig. 5 shows the evaluation results of the surface pit density, pit depth, and X-ray rocking curve full width at half maximum for this Example and the Comparative Example. In Example 1, a surface roughening process for the seed substrate was introduced, while in Comparative Example 1, such introduction was not carried out. As can be seen from Fig. 5(a), in Example 1 where the surface roughening process was introduced, the pit density increased. Also, as shown in Fig. 5(b), the pit depth is smaller in Example 1 than in Comparative Example 1. From these results, it can be seen that by introducing the surface roughening process, the surface unevenness can be reduced. Therefore, when manufacturing a wafer of a group III nitride substrate from the group III nitride crystal obtained in Example 1, it was shown that the surface unevenness to be removed is less than that in Comparative Example 1, and the material loss can be reduced.

[0043] Furthermore, as shown in the evaluation result of the X-ray rocking curve full width at half maximum in Fig. 5(c), in Example 1, since the pit density was increased and the surface unevenness was reduced, it was confirmed that the orientation of the tilt component was improved. From this result, it was shown that when the surface roughening process was introduced, the crystal quality was improved.

[0044] Furthermore, when analyzing the grown crystal on which the surface roughening process has been performed, a history of pit generation is confirmed even in regions that do not contain dislocation defects. Fig. 6 shows the surface optical microscope image and the photoluminescence (PL) image of the same location after etching the grown crystal after smooth polishing with a mixed melt of sodium hydroxide and potassium hydroxide. By etching with the mixed melt, hexagonal pyramid-shaped etch pits are formed in the regions where dislocation defects exist as shown in Fig. 6(a). On the other hand, when confirming the PL image in Fig. 6(b), petal-shaped luminescence is confirmed even in the regions where dislocation defects do not exist, that is, in the regions where etch pits have not occurred. This petal-shaped luminescence reflects the history of the pits that occurred during crystal growth. Therefore, it is understood that by introducing the surface roughening process, pits can be generated even in regions where dislocation defects do not exist, that is, in regions where etch pits do not occur. In the obtained group-III nitride crystal, on the smooth surface after surface polishing, the number of petal-shaped luminescence regions, that is, the number of pits, is larger than the number of dislocation defects. As described above, according to the method for manufacturing a group-III nitride crystal according to Embodiment 1 and Example 1, pits can be generated without increasing dislocation defects to grow the group-III nitride crystal, and the surface unevenness can be reduced. Therefore, it is possible to suppress the material loss when cutting out the group-III nitride substrate and manufacture a high-quality group-III nitride crystal.

[0045] In the present disclosure, it includes appropriately combining any of the various embodiments and / or examples described above, and the effects possessed by each embodiment and / or example can be achieved.

Industrial Applicability

[0046] According to the method for manufacturing a group-III nitride crystal according to the present invention, it is possible to reduce the material loss when manufacturing a group-III nitride substrate and manufacture a high-quality group-III nitride crystal.

Explanation of Signs

[0047] 1 Lattice surface 2 Pit 4 Dislocation defect 6 Surface roughness 8 Cut-out wafer 10 Apparatus for manufacturing group III nitride crystal 100 Raw material chamber 101 Raw material reaction chamber 102 First transfer gas supply port 103 Reactive gas supply pipe 104 Raw material boat 105 Starting group III element source 106 First heater 107 Group III element oxide gas discharge port 108 Gas discharge port 109 Connecting pipe 110 Third heater 111 Growth chamber 112 Third transfer gas supply port 113 Nitrogen element-containing gas supply port 114 Second transfer gas supply port 115 Second heater 116 Seed substrate 117 Substrate susceptor 118 Gas supply port 119 Exhaust port

Claims

1. A step of preparing a seed substrate; A step of forming surface roughness on the seed substrate; After the step of forming the surface roughness, a step of supplying a group III element oxide gas and a nitrogen element-containing gas to grow a group III nitride crystal on the seed substrate; comprising; The step of forming the surface roughness of the seed substrate is carried out in an atmosphere in which only an inert gas and NH 3 gas are supplied in a temperature rising process of 900 ° C or higher and less than 1500 ° C before growing the group III nitride crystal. A method for manufacturing a group III nitride crystal.

2. A group III nitride crystal, On a smooth surface after surface polishing, having a plurality of petal-shaped light-emitting regions and a plurality of dislocation defects, The number of the petal-shaped light-emitting regions is larger than the number of the dislocation defects, The petal-shaped light-emitting region can be confirmed by photoluminescence, and the dislocation defect can be confirmed by a surface optical microscope image after alkali melt etching. A group III nitride crystal.

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