Method for producing group iii nitride crystals

Abstract

The present invention provides a method for producing a Group III nitride crystal, which controls unevenness of the Group III nitride crystal, suppresses generation of cracks and fractures, and reduces variation in off-angle distribution. The method for producing a Group III nitride crystal includes: a preparation step for preparing a seed substrate; a heating step for heating the seed substrate disposed in a growth chamber; and a growth step for supplying, to the growth chamber via the connecting tube, a Group III element oxide gas and a nitrogen element-containing gas, which have been generated in a raw material chamber connected to the growth chamber by a connecting tube, and growing a Group III nitride crystal on the seed substrate in the growth chamber. In the growth step, the partial pressure PO2 (atm) of oxygen gas supplied to the growth chamber satisfies relational expressions (1), (2), (3), and (4) using the partial pressure PH2 (atm) of hydrogen gas in the growth chamber, the temperature X (°C) of the seed substrate, a function F(PH2) (atm) of the partial pressure PH2 (atm) of hydrogen gas, and constants C and D, where (1): PO2 ≤ 7.45000E-6 * X + F(PH2); (2): F(PH2) = C * PH2 + D; (3): C = 1.22500E-3; and (4): D = -8.34825E-3 (atm).

Description

Method for producing group III nitride crystals

[0001] The present disclosure relates to methods for producing Group III-nitride crystals.

[0002] Vertical GaN power devices require GaN substrates with low resistivity and low dislocation density. For example, when fabricating n-type low resistivity GaN substrates, pits have been formed during growth to improve carrier concentration and reduce dislocation density (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-50107

[0004] However, with the manufacturing method described in Patent Document 1, it was difficult to control the warpage of the group III nitride crystal grown on the seed substrate. This caused cracks and fractures, as well as variations in the off-angle distribution. The occurrence of cracks and fractures made it difficult to use the wafer as a wafer. Furthermore, large variations in the off-angle distribution resulted in a large in-plane distribution of the impurity concentration in the device layer formed on the wafer. This resulted in variations in device characteristics. In particular, if the obtained group III nitride crystal had a concave shape on the group III element plane, it was not possible to control the crystal to approach a flat shape during the processing process, and the off-angle distribution could not be reduced.

[0005] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide a method for manufacturing a Group III nitride crystal, which controls the irregularities in the Group III nitride crystal to produce a Group III nitride crystal having a convex shape on the Group III element plane.

[0006] The method for producing a Group III nitride crystal according to the present disclosure includes a preparation step of preparing a seed substrate, and a growth step of supplying a Group III element oxide gas and a nitrogen-containing gas, generated in a source chamber connected to the growth chamber by a connection pipe, to the growth chamber via the connection pipe, and growing a Group III nitride crystal on the seed substrate in the growth chamber, wherein in the growth step, an oxygen gas partial pressure P Ｏ２ (atm) is the hydrogen gas partial pressure P Ｈ２ (atm), the temperature of the seed substrate X (°C), and the hydrogen gas partial pressure P Ｈ２(atm) function F(P Ｈ２ ) (atm) and constants C and D, the following relational expressions (1), (2), (3), and (4) are satisfied. Ｏ２ ≦7.45000E-6*X+F(P Ｈ２ ) (1) F (P Ｈ２ ) = C*P Ｈ２ +D (2) C=1.22500E-3 (3) D=-8.34825E-3 (atm) (4)

[0007] According to the method for producing a Group III nitride crystal according to the present disclosure, it is possible to control the uneven shape of the Group III nitride crystal.

[0008] 1 is a schematic cross-sectional view of a Group III nitride crystal manufacturing apparatus according to a first embodiment of the present disclosure; FIG. 2 is a schematic cross-sectional view of a Group III nitride crystal manufacturing apparatus according to a first embodiment of the present disclosure, showing a convex shape on the Group III element plane of a Group III nitride crystal grown on a seed substrate; FIG. 3 is a schematic cross-sectional view of a Group III nitride crystal grown on a seed substrate, showing a flat Group III nitride crystal; FIG. 4 is a schematic cross-sectional view of a Group III nitride crystal grown on a seed substrate, showing a concave shape on the Group III element plane of a Group III nitride crystal; FIG. 5 is a graph showing the relationship between the temperature (°C) of the seed substrate and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, negative values ​​indicate a concave shape); and FIG. 6 is a graph showing the relationship between the temperature (°C) of the seed substrate and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, and negative values ​​indicate a concave shape). Ｏ２ 1 is a graph showing the relationship between the hydrogen gas partial pressure P (atm) in the growth chamber and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, and negative values ​​indicate a concave shape). Ｈ２ 1 is a graph showing the relationship between the pressure (atm) and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, and negative values ​​indicate a concave shape). FIG. 2 is a schematic cross-sectional view showing a Group III nitride crystal grown on a seed substrate. FIG. 3 is a schematic cross-sectional view showing the state of a grown Group III nitride crystal sliced. FIG. 4 is a schematic cross-sectional view showing the state of the front and back surfaces of a sliced ​​Group III nitride crystal. FIG. 5 is Table 1 listing the manufacturing conditions, and the radius of curvature and shape of the Ga plane for Examples 1 to 4 and Comparative Examples 1 to 3.

[0009] The method for producing a Group III nitride crystal according to the first aspect includes a preparation step of preparing a seed substrate, a heating step of raising the temperature of the seed substrate placed in a growth chamber, and a growth step of supplying a Group III element oxide gas and a nitrogen-containing gas, generated in a source chamber connected to the growth chamber by a connecting pipe, to the growth chamber via the connecting pipe, to grow a Group III nitride crystal on the seed substrate in the growth chamber, wherein in the growth step, an oxygen gas partial pressure P Ｏ２ (atm) is the hydrogen gas partial pressure P Ｈ２ (atm), the temperature of the seed substrate X (°C), and the hydrogen gas partial pressure P Ｈ２ (atm) function F(P Ｈ２ ) (atm) and constants C and D, satisfying the following relational expressions (1), (2), (3), and (4): Ｏ２ ≦7.45000E-6*X+F(P Ｈ２ ) (1) F (P Ｈ２ ) = C*P Ｈ２ +D (2) C=1.22500E-3 (3) D=-8.34825E-3 (atm) (4).

[0010] A method for producing a Group III nitride crystal according to a second aspect may be the same as that of the first aspect, wherein the substrate temperature in the growth step is 1123° C. or higher.

[0011] A method for producing a Group III nitride crystal according to a third aspect is the method according to the first or second aspect described above, wherein the growing step is carried out by adding hydrogen H ２ Partial pressure (P Ｈ２ ) may be carried out at 0.824 atm or higher.

[0012] A method for producing a Group III nitride crystal according to a fourth aspect is the method of any one of the first to third aspects, wherein the growing step is carried out by adding oxygen O ２ Partial pressure (P Ｏ２ ) may be carried out at 0.00136 atm or less.

[0013] The method for producing a Group III nitride crystal according to the fifth aspect is any one of the first to fourth aspects described above, and may further include a slicing step of separating the Group III nitride crystal obtained in the growth step from the seed substrate and slicing it into Group III nitride crystals of a predetermined thickness, and a chemical mechanical polishing step of chemically mechanically polishing both surfaces of the Group III nitride crystals of the predetermined thickness.

[0014] The group III nitride crystal according to the sixth aspect has a convex shape on the group III element plane side, and the radius of curvature of the group III element plane is 10 m or more.

[0015] Hereinafter, a method for manufacturing a group III nitride crystal according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0016] (Embodiment 1) <Outline of Method for Manufacturing Group III Nitride Crystal> An outline of a method for manufacturing a Group III nitride crystal according to this embodiment 1 will be described with reference to the flowchart in Fig. 1 and Fig. 2. Fig. 1(a) shows a chronological flowchart of the manufacturing method. Fig. 1(b) shows, as steps, each functional unit from upstream to downstream within a manufacturing apparatus used in this manufacturing method.

[0017] In the seed substrate preparation step of preparing a seed substrate 116, the seed substrate 116 is placed on a substrate susceptor 117. In the first embodiment, the method for producing a Group III nitride crystal also includes 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. In the first embodiment, the method for producing a Group III nitride crystal also includes a decomposition protection temperature-raising step 1. In the decomposition protection temperature-raising step 1, NH ３ The temperature of the growth chamber 111 is increased to 500° C. or higher and lower than 1100° C. in a gas atmosphere.

[0018] In the first embodiment, the method for producing a group III nitride crystal includes a decomposition protection temperature increase step 2. In the decomposition protection temperature increase step 2, NH ３ Gas and Ga ２ The growth chamber 111 is heated to a temperature of 1100° C. or higher and lower than 1500° C. in an O gas atmosphere.

[0019] 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 source chamber 100 and supplied to the growth chamber 111, and a nitrogen-containing gas is also supplied to the growth chamber 111, thereby growing a Group III nitride crystal on the seed substrate 116.

[0020] The growth step further includes a reactive gas supply step, a Group III element oxide gas generation step, a Group III element oxide gas supply step, a nitrogen-containing gas supply step, a Group III nitride crystal generation step, and a residual gas exhaust step. Note that each step included in the growth step may be carried out simultaneously within the Group III nitride crystal manufacturing apparatus.

[0021] In the reactive gas supply step, a reactive gas is supplied to the raw material reaction chamber, and in the Group III element oxide gas generation step, the starting Group III element source is reacted with the reactive gas (a reducing gas if the starting Group III element source is an oxide, and an oxidizing gas if the starting Group III element source is a metal) to generate a Group III element oxide gas.

[0022] In the Group III element oxide gas supplying step, the Group III element oxide gas produced in the Group III element oxide gas producing step is supplied to the growth chamber.

[0023] In the nitrogen-containing gas supplying step, a nitrogen-containing gas is supplied to the growth chamber, and in the Group III nitride crystal generating step, the Group III element oxide gas supplied into the growth chamber in the Group III element oxide gas supplying step and the nitrogen-containing gas supplied into the growth chamber in the nitrogen-containing gas supplying step are reacted with each other to grow a Group III nitride crystal on the seed substrate.

[0024] In the residual gas exhaust step, unreacted gases that do not contribute to the formation of group III nitride crystals are exhausted to the outside of the chamber.

[0025] In the first embodiment, the method for manufacturing a group III nitride crystal includes a decomposition protection temperature-lowering step. In the decomposition protection temperature-lowering step, in order to suppress the decomposition of the group III nitride crystal grown on the seed substrate 116, NH ３ While supplying the gas, the temperatures of the source chamber 100 and the growth chamber 111 are lowered to 500°C.

[0026] In the first embodiment, the method for producing a group III nitride crystal includes a temperature-lowering step in which the temperatures of the source chamber 100 and the growth chamber 111 are lowered to below 100° C. in an inert gas atmosphere.

[0027] In the first embodiment, the method for producing a group III nitride crystal includes an unloading step in which seed substrate 116 on which group III nitride crystal has been grown is unloaded from growth chamber 111.

[0028] <Outline of III-nitride crystal manufacturing apparatus> An outline of the manufacturing apparatus used in the method for manufacturing III-nitride crystal according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic cross-sectional view of the III-nitride crystal manufacturing apparatus according to the first embodiment.

[0029] 2, the size, ratio, etc. of each component may differ from the actual one. The III-nitride crystal manufacturing apparatus has a raw material reaction chamber 101 disposed within a raw material chamber 100, and a raw material boat 104 carrying a starting Group III element source 105 disposed within the raw material reaction chamber 101. A reactive gas supply pipe 103 is connected to the raw material reaction chamber 101, which supplies a gas that reacts with the starting Group III element source 105. The raw material reaction chamber 101 has a Group III element oxide gas outlet 107, which discharges 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. A first carrier gas supply port 102 for supplying a first carrier gas is connected to the source chamber 100, and 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 a connecting pipe 109 to the growth chamber 111, and are supplied into the growth chamber 111 from a gas supply port 118 connected to the growth chamber 111. The growth chamber 111 has a gas supply port 118, a third carrier gas supply port 112, a nitrogen-containing gas supply port 113, a second carrier gas supply port 114, and an exhaust port 119. The growth chamber 111 is equipped with a substrate susceptor 117 on which a seed substrate 116 is placed.

[0030] <Details of Manufacturing Method and Manufacturing Apparatus> A method for manufacturing a Group III nitride crystal according to the first embodiment will be described in detail with reference to Figures 1 and 2. In the first embodiment, metal Ga is used as the starting Group III element source 105, but this is not limiting and, for example, Al or In may also be used. First, a seed substrate 116 is prepared. Examples of the seed substrate 116 include gallium nitride, gallium arsenide, silicon, sapphire, silicon carbide, zinc oxide, gallium oxide, and ScAlMgO. ４ In the first embodiment, gallium nitride is used as the seed substrate 116 .

[0031] The temperature increase step is explained based on Fig. 1(a). In the temperature increase step, the temperature of the growth chamber is increased in an inert gas atmosphere to a temperature at which decomposition of the seed substrate 116 does not occur. In the production of Group III nitride crystals by the OVPE method, the temperature is increased to approximately 500°C in an inert gas (e.g., N ２ Heating is carried out in a gas atmosphere.

[0032] In the decomposition protection temperature increase step 1, the temperature is increased in a nitrogen-element-containing gas atmosphere while suppressing the decomposition of the seed substrate 116. In the production of Group III nitride crystals by the OVPE method, the temperature is increased in a nitrogen-element-containing gas atmosphere up to 500°C or higher but lower than 1100°C by using an inert gas and a nitrogen-element-containing gas NH ３ Heating is carried out in a state where the gas is mixed with NH ３ The reason for mixing H is to prevent the seed substrate 116 from being decomposed due to the detachment of N atoms. ２ Heating may be carried out in a state where the gas is further mixed.

[0033] In the decomposition protection temperature increase step 2, the temperature is increased in an atmosphere of a group III oxide gas and a nitrogen element-containing gas while suppressing the decomposition of the seed substrate 116. In the production of group III nitride crystals by the OVPE method, the temperature is increased to 1100°C or higher but lower than 1500°C by H ２ gas, inert gas, Group III element oxide gas, and nitrogen element-containing gas NH ３ Heating is performed in a state where the gas is mixed with a group III element oxide gas. The reason for mixing a group III element oxide gas is that decomposition cannot be suppressed with a nitrogen-containing gas alone. By providing a driving force for the growth of group III nitride crystals, it becomes possible to suppress decomposition.

[0034] In the growth step, a Group III element oxide gas is generated in the source chamber 100 and supplied to the growth chamber 111, and a nitrogen-containing gas is also supplied to the growth chamber 111 to grow a Group III nitride crystal on the seed substrate 116. Specifically, the growth step includes a reactive gas supply step, a Group III element oxide gas generation step, a Group III element oxide gas supply step, a nitrogen-containing gas supply step, a Group III nitride crystal growth step, and a residual gas exhaust step.

[0035] Next, a description will be given based on Fig. 1(b). In the reactive gas supply step, a 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, the reactive gas may be a reducing gas or an oxidizing gas, as required. In the first embodiment, metal Ga is used as the group III element source 105, and therefore H is used as the reactive gas. ２ O gas is used.

[0036] In the Group III element oxide gas generation step, the reactive gas supplied to the raw material reaction chamber 101 in the reactive gas supply step reacts with Ga, which is the starting Group III element source 105, to produce Ga, which is the Group III element oxide gas. ２ O gas is generated. Ga ２ The O gas is discharged from the source reaction chamber 101 to the source chamber 100 via the Group III element oxide gas discharge port 107. ２ The O gas is mixed with the first carrier gas supplied from the first carrier gas supply port 102 to the source chamber, and is supplied to the gas exhaust port 108. In the first embodiment, the source chamber 100 is heated by the first heater 106. When the source chamber 100 is heated, the temperature of the source chamber 100 is controlled by the Ga ２From the viewpoint of the boiling point of O gas, the temperature is preferably 800°C or higher. The temperature of the source chamber 100 is preferably lower than that of the growth chamber 111. When the growth chamber is heated by a second heater 115 as described below, the temperature of the source chamber 100 is preferably lower than 1800°C, for example. The starting Group III element source 105 is placed in a source boat 104 disposed in the source reaction chamber 101. The source 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, the source boat 104 preferably has a multi-tiered dish shape to prevent the starting Group III element source 105 and the reactive gas from passing through the source reaction chamber 101 without contacting each other.

[0037] Methods for generating a Group III element oxide gas are roughly classified into a method for reducing the starting Group III element source 105 and a method for oxidizing the starting Group III element source 105. For example, in the reduction method, an oxide (e.g., Ga ２ O ３ ), a reducing gas (e.g., H ２ Gas, CO gas, CH ４ Gas, C ２ H ６ Gas, H ２ S gas, SO ２ On the other hand, in the oxidation method, a non-oxide (e.g., liquid Ga) is used as the starting group III element source 105, and an oxidizing gas (e.g., H ２ O gas, O ２ Gas, CO gas, CO ２ Gas, NO gas, N ２ O gas, NO ２ In addition to the starting group III element source 106, an In source or an Al source can be used as the starting group III element. As the first carrier gas, an inert gas, H ２ Gas or the like can be used.

[0038] In the Group III element oxide gas supply step, Ga generated in the Group III element oxide gas generation step is ２O 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 source chamber 100 and the growth chamber 111 drops below the temperature of the source chamber 100, a reverse reaction of the reaction for producing the Group III element oxide gas occurs, and the starting Ga source 105 precipitates in the connecting pipe 109. Therefore, it is preferable that the connecting pipe 109 be heated by the third heater 110 to a temperature higher than that of the first heater 106 so that the temperature does not drop below that of the source chamber 100.

[0039] In the nitrogen-containing gas supply step, a nitrogen-containing gas is supplied to the growth chamber 111 from a nitrogen-containing gas supply port 113. An example of the nitrogen-containing gas is NH ３ Gas, NO Gas, NO ２ Gas, N ２ O gas, N ２ H ２ Gas, N ２ H ４ Includes gas.

[0040] In the Group III nitride crystal growth process, the source gases supplied into the growth chamber through each supply process are reacted to grow a Group III nitride crystal on the seed substrate 116. The growth chamber 111 is preferably heated by the second heater 115 to a temperature at which the Group III element oxide gas and the nitrogen-containing gas react. At this time, the temperature of the growth chamber 111 is preferably controlled so that it does not fall below the temperature of the source chamber 100, in order to prevent a reverse reaction of the reaction that generates 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. In addition, the Ga generated in the source chamber 100 is preferably heated to a temperature at which the Ga ２ In order to suppress temperature fluctuations in the growth chamber 111 due to the O gas and the first carrier gas, it is desirable that the second heater 115 and the third heater 111 have the same temperature.

[0041] By mixing the Group III element oxide gas supplied to the growth chamber 111 via the Group III element oxide supply step and the nitrogen element-containing gas supplied to the growth chamber 111 via the nitrogen element-containing gas supply step upstream of the seed substrate 116, it is possible to grow a Group III nitride crystal on the seed substrate 116.

[0042] The reactive gas supplying step, the Group III element oxide gas generating step, the Group III element oxide gas supplying step, the nitrogen-containing gas supplying step, the Group III nitride crystal generating step, and the residual gas exhausting step, which are included in the growth step, may be performed simultaneously.

[0043] The second carrier gas may be an inert gas or H ２ In the residual gas exhaust step, the unreacted Group III element oxide gas and nitrogen-containing gas, as well as the first carrier gas, second carrier gas, and third carrier gas are exhausted from the exhaust port 119.

[0044] In the decomposition protection temperature-lowering step, the temperature is lowered in a nitrogen-containing gas atmosphere while suppressing decomposition of the Group III nitride crystal. ３ Cooling is performed while the mixture is mixed with gas.

[0045] In the temperature-lowering step, the temperature is lowered in an inert gas atmosphere to a temperature at which the Group III nitride crystal can be removed from the growth chamber.

[0046] In the first embodiment, seed substrate 116 on which Group III nitride crystal has grown is removed from growth chamber 111 after the temperature-lowering step.

[0047] <Group III Nitride Crystal> Fig. 3A is a schematic cross-sectional view showing a group III nitride crystal 20 grown on a seed substrate 10, with the group III element plane being convex. Fig. 3B is a schematic cross-sectional view showing a group III nitride crystal 20 grown on a seed substrate 10 that is flat. Fig. 3C is a schematic cross-sectional view showing a group III nitride crystal grown on a seed substrate that is concave on the group III element plane. The group III nitride crystal 20 obtained by the method for manufacturing a group III nitride crystal according to the first embodiment described above has a convex group III element plane (Ga plane), as shown in Fig. 3A. Specifically, the radius of curvature of the group III element plane (Ga plane) is 10 m or more.

[0048] <Regarding unevenness control in the method for manufacturing a Group III nitride crystal> Fig. 4 is a graph showing the relationship between the temperature (°C) of the seed substrate and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, and negative values ​​indicate a concave shape). Ｏ２ 6 is a graph showing the relationship between the hydrogen gas partial pressure P (atm) in the growth chamber and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, and negative values ​​indicate a concave shape). Ｈ２ 1 is a graph showing the relationship between the hydrogen gas partial pressure P (atm) and the radius of curvature of the grown crystal (positive values ​​indicate a convex shape, and negative values ​​indicate a concave shape). The present inventors have investigated the manufacturing conditions under which the Group III nitride crystal obtained by the manufacturing method for Group III nitride crystal has a convex shape on the Group III element plane. As a result, the present inventors have found that the radius of curvature of the Group III element plane of the Group III nitride crystal changes depending on the hydrogen gas partial pressure P Ｈ２ (atm), the temperature of the seed substrate X (°C), and the oxygen gas partial pressure P in the growth chamber. Ｏ２ The present inventors have found that the growth rate of the group III element changes depending on three parameters: the temperature of the seed substrate X (°C), the surface of the group III element, and the partial pressure of the oxygen gas in the growth chamber P (atm). Specifically, as shown in Fig. 4, when the temperature of the seed substrate X (°C) is high, the surface of the group III element tends to have a convex shape (positive radius of curvature), and when the temperature is low, the surface of the group III element tends to have a concave shape (negative radius of curvature). Furthermore, as shown in Fig. 5, when the temperature of the seed substrate X (°C) is low, the surface of the group III element tends to have a concave shape (negative radius of curvature). Ｏ２ When the hydrogen gas partial pressure P (atm) is low, the Group III element surface tends to have a convex shape (positive radius of curvature), and when it is high, the Group III element surface tends to have a concave shape (negative radius of curvature). Ｈ２If the pressure (atm) is high, the Group III element surface is likely to have a convex shape (positive radius of curvature), and if it is low, the Group III element surface is likely to have a concave shape (negative radius of curvature).

[0049] By organizing the relationship between the above three parameters and the curvature of the III group element plane, when the radius of curvature of the III group element plane is 0, the oxygen gas partial pressure P Ｏ２ (atm), and the hydrogen gas partial pressure P Ｈ２ The temperature of the seed substrate X (°C) can be approximated by a linear equation (an equation representing a plane with a radius of curvature of 0) of three parameters: the oxygen gas partial pressure P (atm) and the seed substrate temperature X (°C). Ｏ２ (atm): 0.001210 atm, hydrogen gas partial pressure P Ｈ２ (atm): 0.90 atm, temperature X (°C): 1135°C), condition 2 (oxygen gas partial pressure P Ｏ２ (atm): 0.001359 atm, hydrogen gas partial pressure P Ｈ２ (atm): 0.90 atm, temperature X (°C): 1155°C), condition 3 (oxygen gas partial pressure P Ｏ２ (atm): 0.001560 atm, hydrogen gas partial pressure P Ｈ２ (atm): 0.76 atm, and temperature X (°C): 1205°C), the radius of curvature was found to be 0, and the following relational expressions (1) to (4) were obtained. Ｏ２ (atm), and the hydrogen gas partial pressure P Ｈ２ (atm), the temperature of the seed substrate X (°C), and the hydrogen gas partial pressure P Ｈ２ (atm) function F(P Ｈ２ ) (atm) and constants C and D. Specifically, when the following relational expressions (1), (2), (3), and (4) are satisfied in the growth process, the radius of curvature of the group III element plane is 0 or more, that is, a convex shape is obtained on the group III element plane. P Ｏ２ ≦7.45000E-6*X+F(P Ｈ２ ) (1) F (P Ｈ２ ) = C*P Ｈ２ +D (2) C=1.22500E-3 (3) D=-8.34825E-3 (atm) (4)

[0050] As described above, the hydrogen gas partial pressure P Ｈ２ (atm), the temperature of the seed substrate X (°C), and the oxygen gas partial pressure P in the growth chamber. Ｏ２ (atm), and (atm) so as to satisfy the above-mentioned relational expressions (1) to (4), the uneven shape of the grown crystal can be controlled. Furthermore, since cracks and fractures can be suppressed, the production yield when manufacturing Group III nitride crystals can be improved. Furthermore, high-quality Group III nitride crystals with a low off-angle distribution can be manufactured.

[0051] Below, a method for manufacturing a Group III nitride crystal will be explained using Examples 1 to 4 and Comparative Examples 1 to 3. Table 1 in Fig. 8 lists the manufacturing conditions for Examples 1 to 4 and Comparative Examples 1 to 3, as well as the radius of curvature and shape of the Ga plane.

[0052] Example 1 The growth conditions for the group III nitride crystal were a Ga source temperature of 1030° C. and a substrate temperature of 1150° C. ２ Gas was supplied at 0.5 L / min. ２ Gas at 27 L / min, O ２ Gas was supplied to the growth chamber at 0.16 L / min. ２ Gas at 20.4 L / min, H ２ Gas: 81.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２ O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.6167. E-01atm, H ２ is 8.3568. E-01atm, NH ３ is 3.1407. E-02atm, O ２ becomes 1.2377.E-03atm.

[0053] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 1.2430E-03 atm. ２ The partial pressure is O ２ The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 12 mm. The thickness of the grown crystal was estimated from the weight change before and after growth and found to be 1.2 mm.

[0054] Example 2 The growth conditions for the group III nitride crystal were a Ga source temperature of 1030° C. and a substrate temperature of 1200° C. ２ Gas was supplied at 0.5 L / min. ２ Gas at 27 L / min, O ２ Gas was supplied to the growth chamber at 0.16 L / min. ２ Gas at 20.4 L / min, H ２ Gas: 81.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２ O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.6167. E-01atm, H ２ is 8.3568. E-01atm, NH ３ is 3.1407. E-02atm, O ２ becomes 1.2377.E-03atm.

[0055] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 1.6155E-03 atm. ２ The partial pressure is O ２The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 10.5 m, with a convex shape. The thickness of the grown crystal was estimated from the change in weight before and after growth and was found to be 1.1 mm.

[0056] (Example 3) The growth conditions for the group III nitride crystal were a Ga source temperature of 1030°C and a substrate temperature of 1150°C. ２ Gas was supplied at 0.5 L / min. ２ Gas at 27 L / min, O ２ Gas was supplied to the growth chamber at 0.12 L / min. ２ Gas at 20.4 L / min, H ２ Gas: 81.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２ O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.6172. E-01atm, H ２ is 8.3593. E-01atm, NH ３ is 3.1416. E-02atm, O ２ becomes 9.2856.E-04 atm.

[0057] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 1.2433E-03 atm. ２ The partial pressure is O ２ The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 9.6 m, indicating a convex shape. The thickness of the grown crystal was estimated from the change in weight before and after growth and found to be 1.1 mm.

[0058] Example 4 The growth conditions for the group III nitride crystal were a Ga source temperature of 1030° C. and a substrate temperature of 1150° C. ２ Gas was supplied at 0.5 L / min. ２ Gas 35L / min, O ２ Gas was supplied to the growth chamber at 0.16 L / min. ２ Gas at 20.4 L / min, H ２ Gas: 81.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２ O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.5251. E-01atm, H ２ is 8.4669. E-01atm, NH ３ is 2.9627. E-02atm, O ２ becomes 1.1676.E-03atm.

[0059] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 1.2565E-03 atm. ２ The partial pressure is O ２ The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 10.3 m for a convex shape. The thickness of the grown crystal was estimated from the change in weight before and after growth and found to be 1.1 mm.

[0060] Comparative Example 1 The growth conditions for the group III nitride crystal were a Ga source temperature of 1030° C. and a substrate temperature of 1100° C. ２ Gas was supplied at 0.5 L / min. ２ Gas at 27 L / min, O ２ Gas was supplied to the growth chamber at 0.16 L / min. ２Gas at 20.4 L / min, H ２ Gas: 81.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２ O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.6167. E-01atm, H ２ is 8.3568. E-01atm, NH ３ is 3.1407. E-02atm, O ２ becomes 1.2377.E-03atm.

[0061] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 8.7046E-04 atm. ２ The partial pressure is O ２ The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 14 mm. The thickness of the grown crystal was estimated from the weight change before and after growth and found to be 1.3 mm.

[0062] Comparative Example 2 The growth conditions for the group III nitride crystal were a Ga source temperature of 1030° C. and a substrate temperature of 1150° C. ２ Gas was supplied at 0.5 L / min. ２ Gas at 27 L / min, O ２ Gas was supplied to the growth chamber at 0.20 L / min. ２ Gas at 20.4 L / min, H ２ Gas: 81.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.6163. E-01atm, H ２ is 8.3543. E-01atm, NH ３ is 3.1397. E-02atm, O ２ becomes 1.5467.E-03atm.

[0063] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 1.2427E-03 atm. ２ The partial pressure is O ２ The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 8.7 m. The thickness of the grown crystal was estimated from the weight change before and after growth and found to be 1.3 mm.

[0064] Comparative Example 3 The growth conditions for the group III nitride crystal were a Ga source temperature of 1030° C. and a substrate temperature of 1150° C. ２ Gas was supplied at 0.5 L / min. ２ Gas at 27 L / min, O ２ Gas was supplied to the growth chamber at 0.16 L / min. ２ Gas at 20.4 L / min, H ２ Gas: 61.03 L / min, NH ３ The gas was supplied at 4.06 L / min, and the gas supplied to the source chamber and the H generated in the source section were mixed. ２ O gas and Ga ２ O gas was supplied to the growth chamber via a connecting pipe. The growth time of the group III nitride crystal was set to 7 hours, and the total pressure in the growth chamber was controlled to 1.03 atm. A 2-inch diameter GaN substrate, which is a group III nitride crystal, was used as the seed substrate. When the above gases were used, the partial pressure of each gas in the growth chamber was N ２ is 1.9025. E-01atm, H２ is 8.0133. E-01atm, NH ３ is 3.6958. E-02atm, O ２ becomes 1.4565.E-03atm.

[0065] In this case, the convex shape calculated using the formulas (1) and (2) is O ２ The upper limit of the partial pressure is 1.2009E-03 atm. ２ The partial pressure is O ２ The radius of curvature of the grown crystal was measured by XRD (X-ray diffraction) and found to be 6.2 m. The thickness of the grown crystal was estimated from the weight change before and after growth and found to be 1.3 mm.

[0066] <Summary of Examples and Comparative Examples> Table 1 in FIG. 8 shows the growth conditions in the examples and comparative examples, including the substrate temperature, the flow rate of each gas supplied to the source chamber, the flow rate of each gas supplied to the growth chamber, and the O 2 supplied to the growth chamber. ２ Partial pressure and H ２ The partial pressure is shown. The radius of curvature and shape of the Ga face are also shown. In Example 1, Example 2, and Comparative Example 1, only the substrate temperature was changed. FIG. 4 shows the relationship between the substrate temperature and the radius of curvature of the grown crystal. As can be seen from this graph, in order to make the crystal shape convex with respect to the Ga face, the substrate temperature must be higher than 1123°C. In Example 1, Example 3, and Comparative Example 2, only the oxygen flow rate was changed. FIG. 5 shows the relationship between the oxygen partial pressure in the growth chamber and the radius of curvature of the grown crystal. As can be seen from this graph, in order to make the crystal shape convex with respect to the Ga face, the oxygen gas partial pressure in the growth chamber must be lower than 1.36E-3 atm. In Example 1, Example 4, and Comparative Example 3, only the hydrogen flow rate was changed. FIG. 6 shows the relationship between the hydrogen partial pressure in the growth chamber and the radius of curvature of the grown crystal. As can be seen from this graph, in order to make the crystal shape convex with respect to the Ga face, the hydrogen gas partial pressure in the growth chamber must be higher than 8.24E-1 atm.

[0067] <Processing of Grown Crystal> Fig. 7A is a schematic cross-sectional view showing a group III nitride crystal 20 grown on a seed substrate 10. Fig. 7B is a schematic cross-sectional view showing the state of slicing the grown group III nitride crystal 20. Fig. 7C is a schematic cross-sectional view showing the state of the front and back surfaces of one sliced ​​group III nitride crystal 20b after chemical mechanical polishing. An example of a procedure for producing wafers 20a, 20b, and 20c from a grown convex-shaped group III nitride crystal 20 is described below. (1) For example, from the group III nitride crystal 20 grown on the seed substrate 10 shown in Fig. 7A, the grown group III nitride crystal 20 is sliced ​​as shown in Fig. 7B to cut out group III nitride wafers 20a, 20b, and 20c formed only of the growth layer. (2) Next, as shown in Fig. 7C, both surfaces of the cut group III nitride wafer 20b are chemically mechanically polished (CMP).

[0068] According to the method for manufacturing a Group III nitride crystal according to the present disclosure, it is possible to control the irregular shape of the Group III nitride crystal, and in particular to make the Group III element plane convex, thereby enabling the radius of curvature of the Group III element plane to be 10 m or more.

[0069] 10 seed substrate 20 Group III nitride crystal (growth layer) 20a, 20b, 20c Group III nitride wafer 100 source chamber 101 source reaction chamber 102 first carrier gas supply port 103 reactive gas supply pipe 104 source boat 105 starting Group III element source 106 first heater 107 Group III element oxide gas outlet 108 gas outlet 109 connecting pipe 110 third heater 111 growth chamber 112 third carrier gas supply port 113 nitrogen element-containing gas supply port 114 second carrier gas supply port 115 second heater 116 seed substrate 117 substrate susceptor 118 gas supply port 119 exhaust port

Claims

1. A method for growing a Group III nitride crystal on the seed substrate in the growth chamber, comprising: a preparation step of preparing a seed substrate; a heating step of heating the seed substrate placed in a growth chamber; and a growth step of supplying a Group III element oxide gas and a nitrogen-containing gas, which are generated in a source chamber connected to the growth chamber by a connecting pipe, to the growth chamber via the connecting pipe, and growing a Group III nitride crystal on the seed substrate in the growth chamber, wherein in the growth step, the partial pressure of oxygen gas P Ｏ２ (atm) is the hydrogen gas partial pressure P Ｈ２ (atm), the temperature X (°C) of the seed substrate, and the hydrogen gas partial pressure P Ｈ２ (atm) function F(P Ｈ２ ) (atm) and constants C and D, satisfying the following relational expressions (1), (2), (3), and (4): Ｏ２ ≦7.45000E-6*X+F(P Ｈ２ ) (1) F (P Ｈ２ ) = C*P Ｈ２ +D (2) C=1.22500E-3 (3) D=-8.34825E-3 (atm) (4) A method for producing a Group III nitride crystal.

2. The method for producing a Group III nitride crystal according to claim 1, wherein the substrate temperature in the growth step is 1123°C or higher.

3. The growth step is performed by adding hydrogen H ２ Partial pressure (P Ｈ２ 2. The method for producing a Group III nitride crystal according to claim 1 , wherein the heating is carried out at 0.824 atm or higher.

4. The growth step is performed by adding oxygen O ２ Partial pressure (P Ｏ２ 2. The method for producing a Group III nitride crystal according to claim 1, wherein the temperature is 0.00136 atm or less.

5. The method for producing a Group III nitride crystal according to claim 1, further comprising: a slicing step of separating the Group III nitride crystal obtained in the growth step from the seed substrate and slicing it into Group III nitride crystals of a predetermined thickness; and a chemical mechanical polishing step of chemically mechanically polishing both surfaces of the Group III nitride crystals of the predetermined thickness.

6. A Group III nitride crystal that is convex on the Group III element plane side, and the radius of curvature of the Group III element plane is 10 m or more.

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