Group III nitride crystal, Group III nitride substrate, and method for manufacturing Group III nitride crystal

Abstract

To provide a manufacturing method of a group III nitride crystal having excellent conductivity, and a low extinction coefficient.SOLUTION: A manufacturing method of a group III nitride crystal has the steps of: introducing a group III element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas; and producing and growing the group III nitride crystal on a seed substrate by reacting the group III element-containing gas, the nitrogen element-containing gas, the N-type dopant-containing gas, and the hydrogen element-containing gas that have been introduced. The group III nitride crystal has the N-type dopant doped and the hydrogen element doped, a concentration of the N-type dopant is 1×1020 cm-3 or more, and a concentration of the hydrogen element is 1×1019 cm-3 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a Group III nitride crystal, a Group III nitride substrate, and a manufacturing apparatus for a Group III nitride crystal. [Background technology]

[0002] Semiconductors having group III nitride substrates are used in fields such as optical devices such as semiconductor lasers and light-emitting diodes, as well as high-frequency or high-power electronic devices. These semiconductors have attracted particular attention in recent years because they are expected to reduce switching losses during power conversion compared to silicon-based devices. To fabricate high-frequency or high-power electronic devices, it is necessary to fabricate the devices on high-quality group III nitride substrates that can suppress crystal defects that occur in the device layer. Such group III nitride substrates are sometimes manufactured by cutting multiple slices from a group III nitride crystal.

[0003] Methods for producing Group III nitride crystals include, for example, hydride vapor phase epitaxy (hereinafter also referred to as HVPE), ammonothermal, sodium flux, and oxide vapor phase epitaxy (hereinafter also referred to as OVPE).

[0004] In the HVPE method, hydrogen halide gas is introduced onto a single Group III source material to generate a halide gas, and the generated Group III element halide gas is used as a source gas for crystal growth. For example, when growing gallium nitride crystals, HCl gas is introduced into Ga metal to produce gallium chloride (e.g., GaCl) gas, and the gallium chloride-containing gas is used as a Group III source, thereby achieving high-speed growth at 1 mm / h or more (see, for example, Non-Patent Document 1). In the HVPE method, it is known that Group III nitride crystals with N-type conductivity can be obtained by adding mainly silicon, germanium, oxygen, etc. to Group III nitride crystals. For example, gallium nitride crystals with N-type conductivity are produced by adding oxygen to the crystals using the HVPE method (see, for example, Patent Document 1). Furthermore, in the HVPE method, by reducing the concentration of impurities added to the gallium nitride crystals, the absorption coefficient for light with energy less than 3.39 eV, which is the band gap of gallium nitride, can be reduced to 1 cm. -1 Transparent crystals as shown below have been obtained (see, for example, Non-Patent Document 2).

[0005] In the ammonothermal method, single-crystal gallium nitride is produced from polycrystalline gallium nitride in supercritical ammonia to produce gallium nitride crystals (see, for example, Patent Document 2). This method makes it possible to add high concentrations of impurities to the produced crystals, but this can result in the crystals being colored yellow, brown, or black (see, for example, Non-Patent Document 3).

[0006] In the OVPE method, a high concentration of oxygen element is added to a Group III nitride crystal by using an oxide source gas to produce the crystal (see, for example, Patent Document 3). In this method, a Group III oxide gas is reacted with a nitrogen-containing gas to produce a Group III nitride crystal.

[0007] Group III nitride crystals produced by the above-described methods can be processed to obtain Group III nitride substrates. From the viewpoint of production costs, it is desirable to produce substrates by cutting multiple slices from the Group III nitride crystal, and it is desirable to reduce material loss during processing. As a method for processing Group III nitride substrates, for example, non-contact processing methods using lasers, such as laser slicing and stealth dicing, are sometimes used. With such non-contact processing methods, it is possible to significantly reduce material loss during substrate production compared to mechanical processing such as wire slicing. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-44400 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-277182 [Patent Document 3] WO2015 / 053341A1 [Non-patent literature]

[0009] [Non-Patent Document 1] Yoshida et al., Physics Status Solidi C No.8, No. 7-8, 2110―2112 (2011) [Non-patent document 2] S.Pimputkar et al., J. Cryst. Growth 432 (2015) 49-53 [Non-patent document 3] R. Kucharski et al., Crystals 2017, 7, 187, Summary of the Invention [Problem to be solved by the invention]

[0010] However, in all of the HVPE, ammonothermal, sodium flux, and OVPE methods, when an N-type dopant is added to a Group III nitride crystal to increase the carrier concentration and thereby enhance the conductivity of the Group III nitride crystal, the crystal becomes colored and the absorption coefficient increases, which is a problem. For this reason, when cutting out and manufacturing a Group III nitride substrate from a Group III nitride crystal that has high conductivity due to the inclusion of a high concentration of N-type dopant, light is absorbed on or near the surface of the crystal using a processing method that uses light, making it difficult to process the interior. In order to prevent the crystal from becoming discolored, the concentration of the N-type dopant element has traditionally been adjusted, which has kept the absorption coefficient low over a wide wavelength range. However, in this case, it has been difficult to sufficiently improve the electrical conductivity, i.e., it is not easy to obtain a group III nitride crystal that combines a low absorption coefficient with high electrical conductivity.

[0011] The present invention has been made in view of the above circumstances, and has an object to provide a group III nitride crystal having excellent electrical conductivity and a low absorption coefficient. [Means for solving the problem]

[0012] The Group III nitride crystal according to the present invention is doped with an N-type dopant and hydrogen element, The concentration of the N-type dopant is 1×10 20 cm -3 That's all, The concentration of the hydrogen element is 1×10 19 cm -3 That's all.

[0013] A Group III nitride substrate according to the present invention comprises the Group III nitride crystal.

[0014] A method for producing a Group III nitride crystal according to the present invention includes the steps of introducing a Group III element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas; a step of reacting the introduced Group III element-containing gas, nitrogen atom-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas to generate Group III nitride crystals on the seed substrate; It has. [Effects of the Invention]

[0015] According to the present invention, a group III nitride crystal having excellent electrical conductivity and a low absorption coefficient can be obtained. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view that schematically shows an example of an apparatus used in a method for producing a group III nitride crystal according to a first embodiment. [Figure 2] 1 is a graph showing the absorption coefficients of Group III nitride crystals produced in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0017] The Group III nitride crystal according to the first aspect is a Group III nitride crystal, doped with N-type dopants and hydrogen elements; The concentration of the N-type dopant is 1×10 20 cm -3 That's all, The concentration of the hydrogen element is 1×10 19 cm -3 That's all.

[0018] The Group III nitride crystal according to the second aspect is the same as that of the first aspect, wherein the concentration of the N-type dopant is 7×10 20 cm -3 5x10 or more 21 cm -3 It may be the following:

[0019] In the Group III nitride crystal according to a third aspect, in the first or second aspect, the N-type dopant may include at least one selected from the group consisting of silicon element, germanium element, and oxygen element.

[0020] In the Group III nitride crystal according to a fourth aspect, in the third aspect, the N-type dopant may include oxygen element.

[0021] A Group III nitride crystal according to a fifth aspect is the Group III nitride crystal of any one of the first to fourth aspects, wherein the absorption coefficient is 60 cm within a range less than the band gap energy value of the Group III nitride crystal. -1 There may be light with energies as follows:

[0022] A sixth aspect of the Group III nitride crystal is the Group III nitride crystal of any one of the first to fourth aspects, wherein the absorption coefficient of the Group III nitride crystal is 60 cm -1 Light with energies below 3.39 eV may be present in the range below.

[0023] The Group III nitride crystal according to a seventh aspect may be any one of the first to sixth aspects, and have an electrical resistivity of 1 mΩ·cm or less.

[0024] A Group III nitride substrate according to an eighth aspect comprises the Group III nitride crystal of any one of the first to seventh aspects.

[0025] A Group III nitride substrate according to a ninth aspect may be the same as that of the eighth aspect, but with a thickness of 100 μm or more.

[0026] A method for producing a Group III nitride crystal according to a tenth aspect includes the steps of introducing a Group III element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas; a step of reacting the introduced Group III element-containing gas, nitrogen atom-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas to generate Group III nitride crystals on the seed substrate; It has.

[0027] A method for producing a Group III nitride crystal according to an eleventh aspect may be the method for producing a Group III nitride crystal according to the tenth aspect, wherein the N-type dopant-containing gas includes at least one gas selected from the group consisting of a silicon-element-containing gas, a germanium-element-containing gas, and an oxygen-element-containing gas.

[0028] A method for producing a Group III nitride crystal according to a twelfth aspect is the method of the eleventh aspect, wherein the N-type dopant-containing gas may include the oxygen-element-containing gas.

[0029] A thirteenth aspect of the method for producing a Group III nitride crystal is any one of the tenth to twelfth aspects, wherein the hydrogen-element-containing gas may contain at least one bond selected from the group consisting of an N-H bond, a C-H bond, and an O-H bond in its molecule.

[0030] A Group III nitride crystal manufacturing method according to a fourteenth aspect is any one of the tenth to thirteenth aspects, wherein the hydrogen-element-containing gas may contain at least one selected from the group consisting of ammonia gas, hydrazine gas, methylamine gas, ethylamine gas, methane gas, ethane gas, propane gas, butane gas, ethylene gas, acetylene gas, water vapor, hydrogen peroxide, methanol, and ethanol.

[0031] A Group III nitride crystal manufacturing method according to a fifteenth aspect is any one of the tenth to fourteenth aspects, wherein the nitrogen-element-containing gas may contain at least one selected from the group consisting of ammonia gas, hydrazine gas, and dimethylhydrazine gas.

[0032] A method for producing a Group III nitride crystal according to a sixteenth aspect is any one of the tenth to fifteenth aspects, wherein the Group III element-containing gas may contain at least one of an oxide of a Group III element and a halide of a Group III element.

[0033] A method for producing a Group III nitride crystal according to a seventeenth aspect is any one of the tenth to sixteenth aspects, wherein the Group III element-containing gas may contain at least one of Ga2O and GaCl.

[0034] <Background to the Invention> First, the circumstances by which the inventors arrived at the present invention will be explained. The present inventors discovered that Group III nitride crystals with the same N-type dopant concentration and carrier concentration can have significantly different absorption coefficients, and believed that the N-type dopant was not the direct cause of the decrease in absorption coefficient, and pursued the underlying principle.

[0035] The present inventors analyzed the light energy dependence of the absorption coefficient of group III nitride crystals containing a high concentration of N-type dopants. As a result, they found that the absorption coefficient has a tail that exponentially decreases from the band edge of the group III nitride crystals to the low energy side, and therefore found that the increase in the absorption coefficient over a wide wavelength range when a group III nitride crystal contains a high concentration of N-type dopants may be due to a phenomenon known as the Urbach tail.

[0036] The Urbach tail phenomenon is also observed in GaAs, a compound semiconductor. In GaAs, the more the concentration of P-type dopants is increased, the stronger the Urbach tail becomes, which increases the absorption coefficient over a wide wavelength range.

[0037] Next, the inventors discovered that the Urbach tail is proportional to the square of the ionic valence in the crystal of the point defects (including substitutions by impurities) that contribute to the occurrence of the phenomenon, and to the density of those point defects.

[0038] Incidentally, it is known that vacancy defects of Group III elements behave as trivalent P-type dopants in Group III nitride crystals. In contrast, silicon, germanium, and oxygen, which are common N-type dopants, act as monovalent N-type dopants in Group III nitride crystals. Although a simple comparison cannot be made between P-type and N-type dopants because they are different, estimating from the ionic valence, vacancy defects of Group III elements are much more effective in increasing the absorption coefficient than N-type dopants.

[0039] The inventors also noticed that a high concentration of N-type dopant can increase the density of vacancy defects of Group III elements in Group III nitride crystals, and hypothesized that the increase in the absorption coefficient is not directly caused by the N-type dopant, but rather by the increase in the density of vacancy defects of Group III elements that occurs when a high concentration of N-type dopant is added to a Group III nitride crystal.

[0040] Therefore, we considered adding hydrogen atoms to the vacancies of Group III elements in Group III nitride crystals by simultaneously adding a high concentration of hydrogen elements when adding a high concentration of N-type dopants.We thought that adding hydrogen atoms would be able to reduce the absorption coefficient of Group III element nitride crystals even when a high concentration of N-type dopants is added, which means that it would be possible to achieve both a low absorption coefficient and high conductivity.

[0041] Next, we will discuss a method for adding hydrogen atoms to vacancy defects of Group III elements in Group III nitride crystals. While the following describes the case where Group III nitride crystals are produced using gas, it can be easily assumed that hydrogen atoms can be added even when grown in a solution or melt by examining the same method.

[0042] When producing a Group III nitride crystal using a hydrogen-containing gas in order to add hydrogen atoms to vacancy defects in the Group III element, it is necessary to bond the vacancy defects in the Group III element with hydrogen atoms, and therefore it is necessary to form an atomic structure in which a hydrogen atom is bonded to a nitrogen atom near the vacancy defect in the Group III element or to an atom substituted for a nitrogen atom.

[0043] For example, gallium nitride has a structure in which Ga vacancies are bonded to hydrogen atoms (V Ga The bond energy of this structure is 3.25 eV. On the other hand, it is known that the structure of magnesium and hydrogen atoms bonded together (Mg-H structure) is decomposed (the bonds of hydrogen atoms are broken) by thermal annealing at 1000°C to 1200°C. The bond energy of this structure of magnesium and hydrogen atoms bonded together (Mg-H structure) is 1.6 eV. From this, V Ga The Mg-H structure is thought to decompose at about 2200°C, which is twice the absolute temperature of the Mg-H structure. Therefore, when manufacturing at temperatures below 2200°C, Ga The -H structure is not decomposed, so V Ga In addition, when used as a device substrate, the manufacturing temperature of a Group III element nitride semiconductor device is generally 1200°C or less, so this V Ga There is little risk of the -H structure being decomposed, and the added hydrogen atoms being released and causing adverse effects in the device process are low.

[0044] Furthermore, when producing Group III nitride crystals, hydrogen gas is generally used as a carrier gas, meaning that production takes place in an environment where hydrogen elements are supplied at high concentrations. However, the incorporation of hydrogen elements into the crystals is generally below the detection limit in Secondary Ion Mass Sectrometry (SIMS) analysis, and it is presumed that hydrogen elements do not enter the crystals.

[0045] The reason for this is thought to be as follows: A hydrogen molecule has a structure in which two hydrogen atoms are bonded together, and in order for a hydrogen atom to be added to a vacancy defect in a Group III element, the bond between the hydrogen atoms must be broken. However, the bond energy between hydrogen atoms in a hydrogen molecule is generally known to be strong, at 4.48 eV, and molecular species highly reactive with hydrogen molecules are scarce in the manufacturing environment of Group III nitride crystals. Therefore, in the manufacturing environment of Group III nitride crystals, it is thought to be difficult to break the bond between hydrogen atoms in a hydrogen molecule and add a hydrogen atom to a vacancy defect in a Group III element.

[0046] That is, it is presumed that it is difficult to add a high concentration of hydrogen element to a group III nitride crystal by simply supplying hydrogen gas.

[0047] Here, the structure in which a vacancy defect of a group III element and a hydrogen atom are bonded (V III -H structure), the structure is one in which a hydrogen atom is bonded to a nitrogen atom or to an atom of an impurity that has substituted for a nitrogen atom. Therefore, it is considered effective to supply molecules having a structure in which a hydrogen atom is bonded to a nitrogen atom or to an impurity atom that substitutes for a nitrogen atom in a Group III nitride crystal.

[0048] Examples of structures in which a nitrogen atom or an impurity atom that substitutes for a nitrogen atom in a Group III nitride crystal is bonded to a hydrogen atom include NH, CH, and OH, but other bonding structures that perform an equivalent role may also be used.

[0049] From the above, it is believed that if a hydrogen-containing gas having any of the above-mentioned bonding structures is supplied, it will be possible to incorporate a high concentration of hydrogen into the group III nitride crystal.

[0050] Although the measurement of point defects of group III elements in group III nitride crystals can be performed by the positron annihilation method, this method involves risks because it uses positrons generated from radioactive isotopes, making it difficult to easily carry out the measurement. In addition, in order to quantify the defect density, it is necessary to compare with group III nitride crystals having a very low defect density, but it is difficult to obtain crystals with a very low defect density, so it is difficult to measure the point defects of group III elements. Due to these circumstances, it is difficult to specify the mechanism by which the absorption coefficient of group III nitride crystals can be reduced by the addition of the above-mentioned hydrogen element, and it is only based on the speculation of the inventors.

[0051] Hereinafter, the group III nitride crystal, the manufacturing method of the group III nitride crystal, and the manufacturing apparatus of the group III nitride crystal according to the embodiments in the present disclosure will be described in detail.

[0052] (Embodiment 1) <Group III Nitride Crystal> The group III nitride crystal according to the first embodiment (hereinafter, may be referred to as crystal X) is doped with an N-type dopant and hydrogen element. The concentration of the N-type dopant in crystal X is 1×10 20 cm -3 or more. Also, the concentration of the hydrogen element in crystal X is 1×10 19 cm -3 or more.

[0053] Crystal X has excellent conductivity by being doped with an N-type dopant at a concentration of 1×10 20 cm -3 or more. Therefore, the group III nitride substrate formed using crystal X is useful for high-frequency or high-output electronic devices and the like. In crystal X, in addition to the N-type dopant, the hydrogen element is doped at a concentration of 1×10 19 cm -3 or more. As a result, crystal X can have a low absorption coefficient despite containing the N-type dopant at a concentration of 1×10 20 cm -3 or more. That is, crystal X is 1×1020 cm -3 Despite containing an N-type dopant at the above concentration, it is difficult to discolor. Laser processing requires sufficient light to penetrate the processing area of ​​the workpiece. Therefore, the processing area of ​​the workpiece must have a sufficiently low absorption coefficient in the light wavelength range used for processing. For example, when a group-III nitride substrate is produced from crystal X by laser processing, if crystal X has a low absorption coefficient, the laser light is less likely to be absorbed by crystal X, allowing crystal X to be processed well.

[0054] The N-type dopant preferably contains at least one selected from the group consisting of silicon, germanium, and oxygen, which can satisfactorily enhance the conductivity of the crystal X. The N-type dopant preferably contains oxygen element, which allows the oxygen element to be effectively added to the crystal X, particularly when the crystal X is produced by OVPE. The concentration of the N-type dopant is 7×10 20 cm -3 5x10 or more 21 cm -3 In this case, the electrical conductivity of the crystal X can be further increased.

[0055] The concentration of hydrogen element is 1×10 19 cm -3 More than 1×10 20 cm -3 In this case, the crystal X has a better electrical conductivity and a lower absorption coefficient, which can better prevent the crystal X from being colored.

[0056] The extinction coefficient of crystal X is 60cm -1It is preferable that light with an energy equal to or less than the band gap energy value of crystal X is in a range less than the band gap energy value of crystal X. When processing a semiconductor material, light with an energy equal to or greater than the band gap energy value of the semiconductor material is easily absorbed near the surface of the semiconductor material. Therefore, when processing crystal X, it is preferable to process using a laser that outputs light with an energy less than the band gap energy value of crystal X. In particular, -1 By performing processing using light with an energy of 60 cm or less, the light for processing is less likely to be absorbed by the crystal X. Therefore, the crystal X can be processed particularly well, and material loss can be reduced when manufacturing a group III nitride substrate from the crystal X. In addition, when the absorption coefficient is 60 cm or less, -1 By performing processing using light with the following energy, even when a group III nitride substrate having a thickness of, for example, 100 μm or more is manufactured from crystal X, the light used for processing can easily reach from the surface to the deep part of crystal X. Therefore, processing can be performed satisfactorily.

[0057] The value of the band gap energy varies depending on the composition of crystal X. For example, when processing gallium nitride, using a laser that outputs light with an energy less than the band gap of 3.39 eV allows for good processing. Furthermore, when processing aluminum nitride, using a laser that outputs light with an energy less than the band gap of 6.2 eV allows for good processing. The lower limit of the energy value of the light used for processing is not particularly limited, but may be, for example, 1 eV. By using light of 1 eV or more for processing, the laser light is less likely to be absorbed by the high concentration of free carriers present in crystal X, which has a high concentration of N-type dopant, making it easier for the laser light to penetrate into the crystal. In this case, when the absorption coefficient of crystal X is 60 cm -1 The light having the energy below may be present in the range of 1 eV or more and less than the band gap energy value of the crystal X.

[0058] The extinction coefficient of crystal X is 60cm -1It is preferable that light having energy below is present within a range of less than 3.39 eV. When crystal X is gallium nitride, the absorption coefficient is 60 cm within a range of 1 eV or more and less than 3.39 eV -1 Using light having energy below, crystal X can be processed particularly well. The absorption coefficient of crystal X is 60 cm -1 It is preferable that light having energy below is present within a range of 1 eV or more and less than 3.39 eV.

[0059] The resistivity of crystal X is preferably 1 mΩ·cm or less. In this case, the group III nitride substrate produced using crystal X can have excellent conductivity. The resistivity of crystal X is more preferably 0.7 mΩ·cm or less.

[0060] By processing crystal X, a group III nitride substrate can be obtained. That is, the group III nitride substrate according to the present disclosure contains crystal X. The thickness of the group III nitride substrate is preferably 100 μm or more. In this case, the group III nitride substrate has higher strength.

[0061] <Method for manufacturing group III nitride crystal> Next, a method for manufacturing crystal X (group III nitride crystal) will be described with reference to FIG. 1. In the following description, an example of manufacturing using a gas will be described, but crystal X of the present disclosure can also be obtained when manufacturing in a solution or melt. The method for manufacturing crystal X includes a step of introducing a source gas and a step of generating and growing crystal X. In the step of introducing the source gas, a group III element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas are introduced. In the step of generating and growing crystal X, the introduced group III element-containing gas, nitrogen atom-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas are reacted to generate and grow crystal X on the seed substrate 201 placed on the substrate tray 202.

[0062] It should be noted that four different types of gases may be used as the source gas, or three or less types of gases may be used. That is, the group III element-containing gas, nitrogen element-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas may be different from one another or may be the same. For example, the same gas may be used as the nitrogen element-containing gas and the hydrogen element-containing gas. Also, the same gas may be used as the group III element-containing gas and the N-type dopant-containing gas.

[0063] In the method for producing a Group III nitride crystal according to the first embodiment, the Group III element-containing gas preferably contains at least one of an oxide of a Group III element and a halide of a Group III element. In this case, the gas concentration of the Group III element-containing gas can be maintained high. Furthermore, the growth rate of the crystal X can be increased. When producing gallium nitride, it is particularly preferable that the Group III element-containing gas contains at least one of GaO and GaCl.

[0064] In the manufacturing method of this embodiment, when a Group III element oxide gas or a Group III element halide gas is used as the Group III element-containing gas, it is preferable to further include a step of reacting a Group III element-containing material with the gas to generate the Group III element-containing gas. In this case, it is easy to prevent the gas from becoming unstable in an environment other than a high temperature, causing solid precipitation and making it difficult to control the gas supply. The step of generating the Group III element-containing gas preferably includes at least one of a step of reacting an oxidizing gas or a halide gas with a Group III element-containing material, and a step of reducing the solid Group III element oxide with hydrogen gas to generate the Group III element oxide gas.

[0065] The oxidizing gas preferably contains at least one of water vapor and oxygen gas, and the halide gas preferably contains HCl.

[0066] Examples of reactions between a Group III element-containing material and an oxidizing gas include, for example, 2Ga (liquid) + H2O (gas) ⇒ Ga2O (gas) + H2 (gas) It includes. Examples of the reaction between a group III element-containing material and a halide gas include, for example, 2Ga(liquid) + 2HCl(gas) ⇒ 2GaCl(gas) + H2(gas) It includes. Examples of the reaction between a solid of an oxide of a group III element and hydrogen gas include, for example, Ga2O3(solid) + 2H2(gas) ⇒ Ga2O(gas) + 2H2O(gas) It includes.

[0067] <Nitrogen element-containing gas> In the method for producing a group III nitride crystal according to this embodiment, the nitrogen element-containing gas preferably contains at least one selected from the group consisting of ammonia gas, hydrazine gas, and dimethylhydrazine gas. Ammonia gas, hydrazine gas, and dimethylhydrazine gas have a boiling point of 200°C or lower, so they can be more easily supplied into the reaction vessel in a gaseous state and have higher reactivity. Therefore, crystal X can be grown more favorably.

[0068] <N-type dopant-containing gas> In the method for producing a group III nitride crystal according to this embodiment, the N-type dopant-containing gas preferably contains at least one selected from the group consisting of a silicon element-containing gas, a germanium element-containing gas, and an oxygen element-containing gas. In this case, it can be easily supplied into the reaction vessel in a gaseous state at room temperature, and furthermore, since it has excellent reactivity, crystal X can be grown favorably. The N-type dopant-containing gas more preferably contains an oxygen element-containing gas.

[0069] <Silicon element-containing gas> The silicon element-containing gas preferably contains at least one selected from the group consisting of SiH4, SiH3Cl, and SiH2Cl2. In this case, the silicon element-containing gas in a gaseous state at room temperature can be easily supplied into the reaction vessel, and since it has high reactivity, crystal X can be grown favorably.

[0070] <Germanium element-containing gas> The germanium element-containing gas preferably contains at least one selected from the group consisting of GeH4, GeH3Cl, and GeH2Cl2. In this case, the germanium element-containing gas in a gaseous state at room temperature can be easily supplied into the reaction vessel, and due to its high reactivity, crystal X can be favorably grown.

[0071] <Oxygen element-containing gas> The oxygen element-containing gas preferably contains at least one selected from the group consisting of water vapor, oxygen gas, N2O gas, NO gas, NO2 gas, CO gas, and CO2 gas. In this case, the oxygen element-containing gas in a gaseous state at room temperature can be easily supplied into the reaction vessel, and due to its high reactivity, crystal X can be favorably grown.

[0072] The N-type dopant-containing gas particularly preferably contains at least one selected from the group consisting of GeO gas, Ga2O gas, and In2O gas. In this case, the N-type dopant-containing gas can be easily generated at a temperature close to the production temperature of crystal X, and due to its high reactivity, crystal X can be particularly favorably grown.

[0073] <Hydrogen element-containing gas> In the method for producing a group III nitride crystal according to the present embodiment, it preferably contains at least one selected from the group consisting of N-H bond, C-H bond, and O-H bond. In this case, the hydrogen element-containing gas in a gaseous state at room temperature can be easily supplied into the reaction vessel, and due to its excellent reactivity, crystal X can be favorably grown. Further, since the hydrogen element-containing gas contains at least one selected from the group consisting of N-H bond, C-H bond, and O-H bond, coloring of crystal X can be prevented and the absorption coefficient can be further reduced. This is presumably because hydrogen atoms can be favorably added to group III element vacancies in crystal X.

[0074] <Gas having an N-H bond> The gas having an N-H bond preferably contains at least one selected from the group consisting of ammonia gas, hydrazine gas, methylamine gas, and ethylamine gas. In this case, the N-H bond-containing gas in a gaseous state at normal temperature can be easily supplied into the reaction vessel, and crystal X can be grown particularly well due to excellent reactivity.

[0075] <Gas having a C-H bond> The gas having a C-H bond preferably contains at least one selected from the group consisting of methane gas, ethane gas, propane gas, butane gas, ethylene gas, acetylene gas, methylamine gas, and ethylamine gas. In this case, the C-H bond-containing gas in a gaseous state at normal temperature can be easily supplied into the reaction vessel, and crystal X can be grown particularly well due to excellent reactivity.

[0076] <Gas having an O-H bond> The gas having an O-H bond preferably contains at least one selected from the group consisting of water vapor, hydrogen peroxide, methanol, and ethanol. In this case, since the boiling point of the C-H bond-containing gas is 160°C or lower, the C-H bond-containing gas can be easily supplied into the reaction vessel, and crystal X can be grown particularly well due to excellent reactivity.

[0077] The hydrogen element-containing gas particularly preferably contains at least one selected from the group consisting of ammonia gas, hydrazine gas, methylamine gas, ethylamine gas, methane gas, ethane gas, propane gas, butane gas, ethylene gas, acetylene gas, water vapor, hydrogen peroxide, methanol, and ethanol.

[0078] In the method for manufacturing a group III nitride crystal according to this embodiment, different gases or the same type of gas may be used as the group III element-containing gas, nitrogen element-containing gas, N-type dopant-containing gas, hydrogen element-containing gas, and carrier gas. For example, Ga2O gas may be used as the group III element-containing gas, and Ga2O may also be used as the N-type dopant-containing gas. In this way, when the same type of gas is used, the gas introduction paths can be combined, and the manufacturing equipment may be simplified in some cases.

[0079] In the manufacturing method of the group III nitride crystal according to this embodiment, in the growth step of growing crystal X, from the viewpoint of the reactivity of the gases used in the manufacturing, the temperature at which the group III element-containing gas and the nitrogen element-containing gas react is preferably 700 °C or higher and 1500 °C or lower. From the viewpoint of ensuring the crystal growth rate and improving the crystal quality, it is more preferably 1000 °C or higher and 1400 °C or lower.

[0080] The method for manufacturing a group III nitride crystal according to this embodiment can be implemented, for example, by using the manufacturing apparatus for a group III nitride crystal shown in FIG. 1. Note that the manufacturing apparatus for a group III nitride crystal shown in FIG. 1 is merely an example, and the apparatus is not limited to the manufacturing apparatus in FIG. 1 as long as it can manufacture crystal X of the present disclosure. In the figure, the sizes and ratios of each part may be different from the actual ones for clarity. Also, there may be cases where materials that need to be arranged in the manufacturing apparatus in advance during the manufacture of crystal X are shown.

[0081] <Manufacturing Apparatus for Group III Nitride Crystal> In this Group III nitride crystal manufacturing apparatus, a hydrogen element-containing gas inlet pipe 102, an N-type dopant-containing gas inlet pipe 103, a nitrogen element-containing gas inlet pipe 104, a Group III element-containing gas inlet pipe 105, and a gas exhaust pipe 109 are connected to a reaction vessel 101. A substrate tray 202 having a seed substrate 201 placed thereon is disposed inside the reaction vessel 101. Note that the arrangement of the hydrogen element-containing gas inlet pipe 102, the N-type dopant-containing gas inlet pipe 103, the nitrogen element-containing gas inlet pipe 104, and the Group III element-containing gas inlet pipe 105 is not limited to that shown in FIG.

[0082] As described above, four different types of gases may be used as source gases, or three or less types of gases may be used. Therefore, the manufacturing apparatus shown in Fig. 1 is provided with four inlet pipes, namely, the hydrogen element-containing gas inlet pipe 102, the N-type dopant-containing gas inlet pipe 103, the nitrogen element-containing gas inlet pipe 104, and the group III element-containing gas inlet pipe 105, but is not limited thereto, and the manufacturing apparatus may have three or less inlet pipes.

[0083] The group III element-containing gas and the nitrogen element-containing gas react with each other, and a crystal X grows on the seed substrate 201. Unreacted gas and by-product gases are exhausted from the gas exhaust pipe 109.

[0084] The group III element-containing gas is generated in the group III element-containing gas generating section 106 by reaction between a group III element-containing material 107 and a group III element-containing gas generating gas introduced from a group III element-containing gas generating gas inlet pipe 108.

[0085] Also, in the introduction pipe or reaction section of each gas, it may be heated by each heater and adjusted to the reaction state of the desired gas or the growth conditions of crystal X. For example, as shown in FIG. 1, at least one of a reaction vessel heater 111 adjacent to the reaction vessel 101, a hydrogen element-containing gas introduction pipe heater 112 adjacent to the hydrogen element-containing gas introduction pipe 102, an N-type dopant-containing gas introduction pipe heater 113 adjacent to the N-type dopant-containing gas introduction pipe 103, a nitrogen element-containing gas introduction pipe heater 114 adjacent to the nitrogen element-containing gas introduction pipe 104, and a group III element-containing gas generation section heater 115 adjacent to the group III element-containing gas generation section 106 may be provided.

[0086] <Group III element-containing material> The group III element-containing material 107 is a material containing at least one selected from the group consisting of aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). Also, from the viewpoint of handling during installation, it is preferable that a material that is solid or liquid at normal temperature is used as the group III element-containing material 107. For example, examples of the group III element-containing material 107 that is solid at normal temperature include Al2O3, Ga2O3, In2O3, Tl2O3, Al, In, and Tl. Examples of the group III element-containing material 107 that is liquid at normal temperature include Ga.

[0087] Examples of the gas introduced into the group III element-containing gas generation section 106 to generate the group III element-containing gas include hydrogen gas, water vapor gas, and hydrogen chloride gas. Also, from the viewpoint of reaction control, the gas introduced into the group III element-containing gas generation section 106 is preferably introduced after being mixed with a carrier gas.

[0088] <Carrier gas> The carrier gas is not particularly limited, and examples of the carrier gas include nitrogen gas, hydrogen gas, argon gas, and helium gas. A gas obtained by mixing these gases may be used as the carrier gas.

[0089] <Seed substrate> The material of the seed substrate 201 is not particularly limited and can be appropriately selected depending on the characteristics of the crystal X to be produced. For example, the seed substrate 201 is preferably a single crystal substrate having the same element composition ratio as the crystal X to be produced. Examples of materials for the seed substrate 201 include sapphire, ScAlMgO, group III nitrides, LiAlO, and ZnO.

[0090] It should be noted that the present disclosure is not limited to the above-described embodiment. For example, the above-described components may be combined in any desired manner, or another embodiment realized by excluding some of the above-described components may be considered as an embodiment of the present disclosure.

[0091] (Example) The methods for producing Group III nitride crystals according to Examples 1 to 4 and Comparative Example will now be described. In Example 1, gallium nitride crystal was produced as Group III nitride crystal using gases. GaO gas was used as the Group III element-containing gas and N-type dopant-containing gas, ammonia gas was used as the nitrogen element-containing gas, and ammonia gas was used as the hydrogen element-containing gas. Ga was used as the Group III element-containing material, and oxygen gas was used as the Group III element-containing gas generating gas. Gallium nitride crystal was used as the seed substrate 201. First, Ga was placed in the group III element-containing gas generator 106, and GaO was generated using oxygen gas. The generated GaO was supplied to the reaction vessel 101 through the group III element-containing gas inlet pipe 105. Then, ammonia gas, as a nitrogen element-containing gas, was introduced into the reaction vessel 101 through the nitrogen element-containing gas inlet pipe 104. Furthermore, ammonia gas, as a hydrogen element-containing gas, was introduced into the reaction vessel 101 through the hydrogen element-containing gas inlet pipe 102, to produce a group III nitride crystal.

[0092] The manufacturing conditions for the Group III nitride crystal will be described in detail. First, the heaters (111, 112, 113, 114, 115) were heated. After the temperature of the Group III element-containing gas generator 106 reached 1100°C and the temperature of the reaction vessel reached 1200°C, oxygen gas was introduced into the Group III element-containing gas generator 106 at a flow rate of 20 sccm, and simultaneously, a mixed gas of nitrogen and hydrogen was introduced as a carrier gas at a flow rate of 5 slm. These were reacted on Ga installed in the Group III element-containing gas generator 106 to generate GaO gas, and the resulting GaO gas was introduced into the reaction vessel 101 as a Group III element-containing gas and an N-type dopant-containing gas. Furthermore, ammonia gas as a nitrogen element-containing gas was introduced at a flow rate of 0.5 slm, and ammonia gas as a hydrogen element-containing gas was introduced at a flow rate of 1 slm. Furthermore, a mixed gas of nitrogen and hydrogen as a carrier gas for these was introduced into the reaction vessel 101 at a flow rate of 40 slm. GaO gas and ammonia gas reacted in the reaction vessel 101, producing gallium nitride crystal on the seed substrate 201. The gallium nitride crystal production reaction was carried out for 6 hours. In this way, 300 μm thick gallium nitride crystal was produced as an epitaxial layer on the GaN substrate.

[0093] Gallium nitride crystal of Example 2 was produced in the same manner as in Example 1 above, except that the flow rate of ammonia gas as the hydrogen-element-containing gas was set to 1.5 slm. Gallium nitride crystal of Example 3 was produced in the same manner as in Example 1 above, except that methane gas was used as the hydrogen-containing gas. Gallium nitride crystal of Example 4 was produced in the same manner as in Example 1 above, except that water vapor was used as the hydrogen-containing gas and the flow rate of the water vapor was set to 10 sccm.

[0094] The gallium nitride crystal of the comparative example was produced in the same manner as in Example 1 above, except that no hydrogen-containing gas was used.

[0095] The crystals produced in Examples 1 to 4 were each polished to a thickness of 150 μm to produce a free-standing gallium nitride substrate consisting of only the crystal layer, and the crystal produced in Comparative Example was polished to a thickness of 200 μm to produce a free-standing gallium nitride substrate consisting of only the crystal layer.

[0096] The substrates of Examples 1 to 4 and Comparative Example obtained in this manner were used to evaluate the properties shown in Table 1. Regarding the light absorption coefficient, the minimum value of the light absorption coefficient for light with energy within the range of 3.39 eV or less, the band gap energy of gallium nitride, was measured.

[0097] [Table 1]

[0098] The impurity concentration of the gallium nitride crystal produced in Example 1 was analyzed by SIMS, and the concentration of oxygen element was found to be 7.2 × 10 20 atoms / cm 3 , the concentration of hydrogen element is 1.4×10 19 atoms / cm 3 The resistivity was 6.40×10 -4 The minimum absorption coefficient is 33 cm for light with an energy of 1.85 eV. -1 In Example 1, the concentrations of oxygen element and hydrogen element were high, the resistivity was low, and the absorption coefficient was also small.

[0099] The impurity concentration of the gallium nitride crystal produced in Example 2 was analyzed by SIMS, and the concentration of oxygen element was found to be 7.1 × 10 20 atoms / cm 3 , the concentration of hydrogen element is 1.8×10 19 atoms / cm 3 The resistivity was 5.76×10 -4 The minimum absorption coefficient is 26 cm for light with an energy of 1.92 eV. -1Compared to Example 1, by increasing the supply amount of ammonia gas as the hydrogen-containing gas, the hydrogen concentration in the crystal increased and the absorption coefficient decreased.

[0100] The impurity concentration of the gallium nitride crystal produced in Example 3 was analyzed by SIMS, and the concentration of oxygen element was 9.4 × 10 20 atoms / cm 3 , the concentration of hydrogen element is 7.2 × 10 19 atoms / cm 3 The resistivity was 5.93×10 -4 The minimum absorption coefficient is 18 cm for light with an energy of 1.94 eV. -1 The extinction coefficient was

[0101] The impurity concentration of the gallium nitride crystal produced in Example 4 was analyzed by SIMS, and the concentration of oxygen element was found to be 1.9 × 10 21 atoms / cm 3 , the concentration of hydrogen element is 6.5×10 19 atoms / cm 3 The resistivity was 5.65×10 -4 The minimum absorption coefficient is 28 cm for light with an energy of 1.92 eV. -1 The extinction coefficient was

[0102] The impurity concentration of the gallium nitride crystal produced in the comparative example was analyzed by SIMS, and the concentration of oxygen was 4.3 × 10 20 atoms / cm 3 , and for hydrogen element, the detection limit is 1.2 × 10 17 atoms / cm 3 The resistivity was 7.67×10 -4 The minimum absorption coefficient is 74 cm for light with an energy of 1.33 eV. -1 The extinction coefficient was

[0103] As shown in Table 1, the Group III nitride crystals produced in Examples 1 to 4 and Comparative Example all had an oxygen element concentration of 1×10 20 atoms / cm 3Because the concentration is as high as 1×10, the resistivity is as low as 1 mΩ cm or less. 19 atoms / cm 3 The crystals of Examples 1 to 4 have an absorption coefficient of 60 cm within a range less than the band gap energy value. -1 On the other hand, in the comparative example, within the range below the band gap energy value, the minimum value of the absorption coefficient is 74 cm -1 This shows that the extinction coefficient of the crystals of the examples is significantly smaller than that of the crystals of the comparative examples.

[0104] The absorption coefficients of the group III nitride crystals produced in Examples 1 to 4 and the Comparative Example are shown in the graph of Figure 2. Figure 2 shows the relationship between the energy value of light and the absorption coefficient for that light. As shown in Figure 2, in Examples 1 to 4, in which the concentration of hydrogen element in the crystal is higher by two orders of magnitude or more than the Comparative Example, the absorption coefficients were low over a wide range in the energy region below the band edge energy of 3.39 eV. Note that in Figure 2, the absorption coefficient of the crystal produced in the Comparative Example was too high in the energy region above 2.19 eV, so measurement was not satisfactory.

[0105] From the above results, in the Group III nitride crystal of the present disclosure, even when the concentration of N-type dopant in the crystal is increased to reduce the electrical resistivity, the absorption coefficient can be reduced over a wide energy range by incorporating hydrogen element at a specific concentration or higher in the crystal, which makes it possible to process the inside of the crystal using a laser.

[0106] In addition, the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example. [Industrial Applicability]

[0107] As described above, the Group III nitride crystals, the manufacturing method for Group III nitride crystals, and the manufacturing apparatus for Group III nitride crystals according to the present invention make it possible to fabricate Group III nitride semiconductor substrates by processing highly conductive Group III element nitride crystals with little material loss, which is expected to lead to higher performance and lower costs for high frequency or high output electronic devices. [Explanation of symbols]

[0108] 101 Reaction vessel 102 Hydrogen-containing gas introduction tube 103 N-type dopant containing gas inlet tube 104 Nitrogen-containing gas introduction tube 105 III-group element-containing gas introduction tube 106 Group III element-containing gas generator 107 Group III element-containing materials 108 Group III element-containing gas generator gas introduction tube 109 Gas Exhaust Pipe 111 Reaction vessel heater 112 Hydrogen-containing gas introduction tube heater 113 N-type dopant-containing gas introduction tube heater 114 Nitrogen-containing gas introduction tube heater 115 Group III element-containing gas generator heater 201 species substrate 202 PCB tray

Claims

1. introducing a group III element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas; reacting the introduced Group III element-containing gas, nitrogen element-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas to generate and grow a Group III nitride crystal on a seed substrate; A method for producing a Group III nitride crystal having the following structure: The Group III nitride crystal formed by the above-described manufacturing method is The N-type dopant and the hydrogen element are doped, The concentration of the hydrogen element is 1×10 １９ cm －３ That is all, The concentration of the N-type dopant is 7×10 ２０ cm －３ 5x10 or more ２１ cm －３ A method for producing a Group III nitride crystal, comprising:

2. introducing a group III element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas; reacting the introduced Group III element-containing gas, nitrogen element-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas to generate and grow a Group III nitride crystal on a seed substrate; A method for producing a Group III nitride crystal having the following structure: the group III element-containing gas contains at least one of an oxide of a group III element and a halide of a group III element; The Group III nitride crystal formed by the above-described manufacturing method is doped with N-type dopants and hydrogen elements; The concentration of the N-type dopant is 1×10 ２０ cm －３ That's all, The concentration of the hydrogen element is 1×10 １９ cm －３ That is all, The electrical resistivity is 1 mΩ cm or less. A method for producing a group III nitride crystal.

3. 3. The method for producing a Group III nitride crystal according to claim 1, wherein the N-type dopant-containing gas includes at least one gas selected from the group consisting of a silicon-element-containing gas, a germanium-element-containing gas, and an oxygen-element-containing gas.

4. The method for producing a Group III nitride crystal according to claim 3 , wherein the N-type dopant-containing gas includes the oxygen-element-containing gas.

5. 5. The method for producing a Group III nitride crystal according to claim 1, wherein the hydrogen-element-containing gas contains, in its molecules, at least one bond selected from the group consisting of an N—H bond, a C—H bond, and an O—H bond.

6. 6. The method for producing a Group III nitride crystal according to claim 1, wherein the hydrogen-element-containing gas comprises at least one gas selected from the group consisting of ammonia gas, hydrazine gas, methylamine gas, ethylamine gas, methane gas, ethane gas, propane gas, butane gas, ethylene gas, acetylene gas, water vapor, hydrogen peroxide, methanol, and ethanol.

7. 7. The method for producing a Group III nitride crystal according to claim 1, wherein the nitrogen-containing gas includes at least one gas selected from the group consisting of ammonia gas, hydrazine gas, and dimethylhydrazine gas.

8. The group III element-containing gas is Ga ２ The method for producing a Group III nitride crystal according to any one of claims 1 to 7, wherein the crystal contains at least one of O and GaCl.

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