Group iii nitride crystal, group iii nitride substrate, and method for producing group iii nitride crystal

Abstract

This invention provides a group III nitride crystal, a group III nitride substrate, and a method for manufacturing the group III nitride crystal. It provides a group III nitride crystal with excellent conductivity and low light absorption coefficient. The group III nitride crystal is doped with an N-type dopant and hydrogen, with the N-type dopant concentration being 1 × 10⁻⁶. 20 cm ‑3 The concentration of hydrogen is 1 × 10⁴. 19 cm ‑3 above.

Description

TECHNICAL FIELD

[0001] The present application relates to a Group III nitride crystal, a Group III nitride substrate, and a manufacturing apparatus for a Group III nitride crystal. BACKGROUND

[0002] A semiconductor having a Group III nitride substrate is used in the fields of optical devices such as semiconductor lasers and light emitting diodes, and electronic devices of high frequency or high output power. Such a semiconductor is expected to reduce switching loss at power conversion as compared with a silicon-based device, and thus has been particularly focused on in recent years. In order to produce an electronic device of high frequency or high output power, it is necessary to produce the device on a high-quality Group III nitride substrate capable of suppressing crystal defects generated in a device layer. Such a Group III nitride substrate is sometimes manufactured by cutting a plurality of pieces from a Group III nitride crystal.

[0003] Methods for manufacturing a Group III nitride crystal include, for example, a hydride vapor phase epitaxy method (hereinafter, also referred to as an HVPE method), an ammonia thermal method, a sodium flux method, and an oxide vapor phase epitaxy method (hereinafter, also referred to as an OVPE method).

[0004] In the HVPE method, a hydrogen halide gas is introduced to a Group III raw material in an elemental state to generate a halide gas, and the generated Group III element halide gas is used as a raw material gas for crystal growth. For example, in the case of growing a gallium nitride crystal, a gallium chloride (for example, GaCl) gas is manufactured by introducing an HC1 gas to a Ga metal, and a gas containing the gallium chloride is used as a Group III source, whereby high-speed growth of 1 mm / h or more is performed (for example, refer to Non-Patent Literature 1). In the HVPE method, it is known that a Group III nitride crystal having N-type conductivity can be obtained mainly by adding a silicon element, a germanium element, an oxygen element, or the like to the Group III nitride crystal. For example, by adding an oxygen element to the crystal by the HVPE method, a gallium nitride crystal having N-type conductivity is manufactured (for example, refer to Patent Literature 1). In addition, in the HVPE method, by reducing the impurity concentration added to the gallium nitride crystal, an optical absorption coefficient with respect to light of an energy lower than 3.39 eV, which is a band gap of gallium nitride, is 1 cm -1 The following transparent crystal (for example, refer to Non-Patent Literature 2).

[0005] In the ammonia thermal method, in order to manufacture a gallium nitride crystal, a polycrystalline gallium nitride is used as a raw material in supercritical ammonia to manufacture a single-crystal gallium nitride (for example, refer to Patent Literature 2). In this method, an impurity can be added to the manufactured crystal at a high concentration, but at this time, the crystal is sometimes colored yellow, brown, or black (for example, refer to Non-Patent Literature 3).

[0006] In the OVPE method, by using an oxide source gas, oxygen elements are added to the Group III nitride crystal at a high concentration, thereby manufacturing a crystal (for example, refer to Patent Literature 3). In this method, a Group III oxide gas is reacted with a nitrogen element-containing gas, and a Group III nitride crystal is manufactured.

[0007] The Group III nitride crystal manufactured by the method described above is processed, and a Group III nitride substrate can be obtained. From the viewpoint of manufacturing cost, it is desirable to manufacture a substrate by cutting a plurality of pieces from the Group III nitride crystal, and it is desirable to reduce material loss at the time of processing. As a processing method of the Group III nitride substrate, for example, a non-contact processing method using laser such as a laser dicing method and a stealth dicing method is sometimes used. In such a non-contact processing method, compared to mechanical processing such as a wire saw method, material loss at the time of substrate manufacturing can be greatly suppressed.

[0008] Prior Art Documents

[0009] Patent Literature

[0010] Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2000-44400

[0011] Patent Literature 2: Japanese Patent Application Laid-Open (JP-A) No. 2003-277182

[0012] Patent Literature 3: WO2015 / 053341A1

[0013] Non-Patent Literature

[0014] Non-Patent Literature 1: Yoshida et al., Physics Status Solidi C No. 8, No. 7-8, 2110-2112 (2011)

[0015] Non-Patent Literature 2: S. Pimputkar et al., J. Cryst. Growth 432 (2015) 49-53

[0016] Non-Patent Literature 3: R. Kucharski et al., Crystals 2017, 7, 187 SUMMARY

[0017] PROBLEMS TO BE SOLVED BY THE INVENTION

[0018] However, in any one of the HVPE method, the ammonia thermal method, the sodium flux method, and the OVPE method, if a N-type dopant is added to the Group III nitride crystal to increase the carrier concentration, and the conductivity of the Group III nitride crystal is improved, there is a problem that the crystal is colored and the light absorption coefficient increases.

[0019] Therefore, when manufacturing group III nitride substrates by cutting from group III nitride crystals with high concentrations of N-type dopant to improve conductivity, light is absorbed at or near the surface of the crystal during photoprocessing, making it difficult to process the interior. To prevent crystal discoloration, the concentration of N-type dopant has been adjusted to maintain a low absorption coefficient over a wide wavelength range.

[0020] However, in this case, it is difficult to sufficiently improve conductivity. That is, it is not easy to obtain a group III nitride crystal that combines low absorption coefficient and high conductivity.

[0021] The present invention was made in view of the above circumstances, and its object is to provide a group III nitride crystal with excellent conductivity and low light absorption coefficient.

[0022] Methods for solving problems

[0023] The group III nitride crystal of this invention is doped with an N-type dopant and hydrogen.

[0024] The concentration of the above-mentioned N-type dopant is 1×10⁻⁶. 20 cm -3 above,

[0025] The concentration of hydrogen in the above-mentioned element is 1×10⁻⁶. 19 cm -3 above.

[0026] The group III nitride substrate of the present invention comprises the above-described group III nitride crystal.

[0027] The method for manufacturing group III nitride crystals of the present invention includes:

[0028] The process of introducing gases containing Group III elements, nitrogen, N-type dopants, and hydrogen; and

[0029] The process of reacting the introduced gas containing group III elements, the gas containing nitrogen atoms, the gas containing N-type dopant, and the gas containing hydrogen elements to generate group III nitride crystals on a seed substrate.

[0030] The effects of the invention

[0031] According to the present invention, it is possible to obtain group III nitride crystals with excellent electrical conductivity and low light absorption coefficient. Attached Figure Description

[0032] Figure 1 This is a cross-sectional view schematically illustrating an example of the apparatus used in the method for manufacturing group III nitride crystals according to Embodiment 1.

[0033] Figure 2This is a graph showing the absorption coefficients of the group III nitride crystals manufactured in the examples and comparative examples.

[0034] Explanation of reference numerals in the attached figures

[0035] 101: Reaction Vessel

[0036] 102: Hydrogen-containing gas inlet tube

[0037] 103: Gas inlet tube containing N-type dopant

[0038] 104: Nitrogen-containing gas inlet tube

[0039] 105: Gas inlet tube containing Group III elements

[0040] 106: Gas generation section containing Group III elements

[0041] 107: Materials containing Group III elements

[0042] 108: Gas inlet pipe for generating gas containing Group III elements

[0043] 109: Gas exhaust pipe

[0044] 111: Reactor Heater

[0045] 112: Hydrogen-containing gas inlet pipe heater

[0046] 113: Gas inlet tube heater containing N-type dopant

[0047] 114: Nitrogen-containing gas inlet pipe heater

[0048] 115: Heater for generating gases containing Group III elements

[0049] 201: Seed substrate

[0050] 202: Substrate tray Detailed Implementation

[0051] The first scheme uses a group III nitride crystal doped with an N-type dopant and hydrogen.

[0052] The concentration of the above-mentioned N-type dopant is 1×10⁻⁶. 20 cm -3 above,

[0053] The concentration of hydrogen in the above-mentioned element is 1×10⁻⁶. 19 cm -3 above.

[0054] Regarding the second scheme of group III nitride crystals, based on the first scheme described above, the concentration of the N-type dopant can be 7 × 10⁻⁶. 20 cm-3 Above and 5×10 21 cm -3 the following.

[0055] Regarding the group III nitride crystal of the third scheme, based on the first or second scheme described above, the N-type dopant may contain at least one element selected from silicon, germanium, and oxygen.

[0056] Regarding the fourth scheme of group III nitride crystals, based on the third scheme mentioned above, the N-type dopant can contain oxygen.

[0057] Regarding the fifth scheme of group III nitride crystals, based on any of the first to fourth schemes mentioned above, within a range lower than the band gap energy value of the aforementioned group III nitride crystals, an absorption coefficient of 60 cm⁻¹ is possible. -1 The following energy of light.

[0058] Regarding the group III nitride crystal of the sixth scheme, based on any of the first to fourth schemes mentioned above, the absorption coefficient of the group III nitride crystal becomes 60 cm⁻¹. -1 Light with the following energies can exist in the range below 3.39 eV.

[0059] Regarding the group III nitride crystal of the seventh scheme, based on any of the first to sixth schemes mentioned above, the resistivity can be below 1 mΩ·cm.

[0060] The group III nitride substrate of the eighth embodiment has the group III nitride crystal of any one of the first to seventh embodiments described above.

[0061] Regarding the group III nitride substrate of the ninth scheme, based on the eighth scheme mentioned above, the thickness can be 100 μm or more.

[0062] The method for manufacturing group III nitride crystals according to scheme 10 includes:

[0063] The process of introducing gases containing Group III elements, nitrogen, N-type dopants, and hydrogen; and

[0064] The process of reacting the introduced gas containing group III elements, the gas containing nitrogen atoms, the gas containing N-type dopant, and the gas containing hydrogen elements to generate group III nitride crystals on a seed substrate.

[0065] Regarding the method for manufacturing group III nitride crystals in the eleventh scheme, based on the tenth scheme, the N-type dopant gas may contain at least one selected from silicon-containing gas, germanium-containing gas, and oxygen-containing gas.

[0066] Regarding the manufacturing method of the group III nitride crystal in the twelfth scheme, based on the eleventh scheme, the gas containing the N-type dopant may include the gas containing the oxygen element.

[0067] Regarding the method for manufacturing group III nitride crystals according to scheme thirteen, based on any of schemes ten to twelfth mentioned above, the hydrogen-containing gas may contain at least one selected from NH bonds, CH bonds, and OH bonds in its molecule.

[0068] Regarding the method for manufacturing group III nitride crystals in the fourteenth scheme, based on any of the tenth to thirteenth schemes mentioned above, the hydrogen-containing gas may include at least one selected from ammonia, hydrazine, methylamine, ethylamine, methane, ethane, propane, butane, ethylene, acetylene, water vapor, hydrogen peroxide, methanol, and ethanol.

[0069] Regarding the method for manufacturing group III nitride crystals in scheme 15, based on any of schemes 10 to 14 above, the nitrogen-containing gas may include at least one selected from ammonia, hydrazine, and dimethylhydrazine.

[0070] Regarding the method for manufacturing group III nitride crystals in the sixteenth scheme, based on any of the tenth to fifteenth schemes mentioned above, the group III element-containing gas may contain at least one of group III element oxides and group III element halides.

[0071] Regarding the method for manufacturing group III nitride crystals in scheme seventeen, based on any of schemes ten to sixteen above, the aforementioned group III element-containing gas may include at least one of Ga2O and GaCl.

[0072] <The Process of Completing This Invention>

[0073] First, the inventors will explain the process of completing the present invention.

[0074] The inventors discovered that in group III nitride crystals with the same concentration of N-type dopant and the same carrier concentration, the absorption coefficients sometimes differ significantly. They believed that the direct cause of the decrease in absorption coefficient was not the N-type dopant and explored the underlying principle.

[0075] The inventors analyzed the light energy dependence of the absorption coefficient of a group III nitride crystal containing a high concentration of N-type dopant. The results showed that the absorption coefficient tails exponentially from the band edge of the group III nitride crystal towards the lower energy side. Therefore, the increase in the absorption coefficient over a wide wavelength region when a high concentration of N-type dopant is added to a group III nitride crystal may be caused by a phenomenon known as the Urbach tail.

[0076] The phenomenon known as the Urbach band tail is also visible in GaAs, a compound semiconductor. In GaAs, the more the concentration of p-type dopant is added, the stronger the Urbach band tail is observed, thereby increasing the absorption coefficient in a wide wavelength region.

[0077] Next, the inventors discovered that the Urbach belt tail is proportional to the square of the ion valence of the point defects (including substitution by impurities) in the crystal that contribute to this phenomenon, as well as the density of the point defects.

[0078] However, it is known that vacancy defects in group III elements function as trivalent p-type dopants in group III nitride crystals. In contrast, silicon, germanium, and oxygen, which are typically N-type dopants, function as monovalent N-type dopants in group III nitride crystals. Since p-type and N-type dopants differ, a simple comparison is not possible. However, based on ion valence, it is inferred that vacancy defects in group III elements significantly improve the absorption coefficient compared to N-type dopants.

[0079] Furthermore, the inventors focused on the fact that a high concentration of N-type dopant can increase the density of vacancy defects in group III elements within group III nitride crystals. They then established the hypothesis that the increase in the absorption coefficient is not directly caused by the N-type dopant, but rather by the increased density of vacancy defects in group III elements resulting from the high concentration of N-type dopant added to group III nitride crystals.

[0080] Therefore, considering the presence of both high concentrations of N-type dopant and high concentrations of hydrogen, hydrogen atoms are added to the group III element vacancy defects in the group III nitride crystal. It is believed that by adding hydrogen atoms, even with high concentrations of N-type dopant, the absorption coefficient of the group III element nitride crystal can be reduced, thus achieving a balance between low absorption coefficient and high conductivity.

[0081] Next, a method for attaching hydrogen atoms to vacancy defects of group III elements in group III nitride crystals will be described. The following description focuses on the production of group III nitride crystals using gases; however, even in the case of growth in solution or melt, it can be readily assumed that hydrogen atoms can be attached if the same approach is taken.

[0082] In order to attach hydrogen atoms to vacancy defects in group III elements, when manufacturing group III nitride crystals using hydrogen-containing gases, it is necessary to bond the vacancy defects in group III elements with hydrogen atoms. Therefore, it is necessary to form an atomic structure in which hydrogen atoms are bonded to nitrogen atoms near the vacancy defects in group III elements or to atoms that have substituted nitrogen atoms.

[0083] For example, gallium nitride has a structure formed by Ga vacancy defects bonded to hydrogen atoms (V). Ga The magnesium-hydrogen bond (Mg-H structure) has a bond energy of 3.25 eV. On the other hand, the magnesium-hydrogen bond (Mg-H structure) is known to decompose upon thermal annealing at 1000℃–1200℃ (the hydrogen bonds break). The bond energy of this magnesium-hydrogen bond (Mg-H structure) is 1.6 eV. Therefore, compared to the Mg-H structure, V... Ga The -H structure decomposes at around 2200°C, approximately twice the absolute zero temperature. Therefore, when manufacturing at temperatures below 2200°C, due to V... Ga The -H structure is not decomposed, so V can be fully formed. Ga -H structure. Furthermore, when used as a substrate for devices, the manufacturing temperature of group III nitride semiconductor devices is typically below 1200°C. Therefore, during device manufacturing, this V... Ga The -H structure is less likely to be decomposed, and the likelihood of the attached hydrogen atoms being removed and causing adverse effects in the device manufacturing process is also low.

[0084] In addition, hydrogen is usually used as a carrier gas in the manufacture of group III nitride crystals, which means that the manufacturing is carried out in an environment with a high concentration of hydrogen. However, the intake of hydrogen into the crystal is usually below the detection limit in secondary ion mass spectrometry (SIMS) analysis, suggesting that hydrogen does not enter the crystal.

[0085] The reasons are as follows: A hydrogen molecule is a structure composed of two hydrogen atoms bonded together. To add a hydrogen atom to a vacancy in a group III element, it is necessary to break the bonds between the hydrogen atoms. However, since the bond energy between hydrogen atoms in a hydrogen molecule is as strong as the commonly known 4.48 eV, and highly reactive molecules are lacking in the manufacturing environment of group III nitride crystals, it is considered difficult to break the bonds between hydrogen atoms in a hydrogen molecule and add a hydrogen atom to a vacancy in a group III element under the conditions of group III nitride crystal manufacturing.

[0086] That is, it is hypothesized that if only hydrogen is supplied, it would be difficult to add a high concentration of hydrogen to group III nitride crystals.

[0087] Here, if we focus on the structure formed by the bonding of vacancy defects of group III elements with hydrogen atoms (V... III The -H structure results in a structure where a hydrogen atom is bonded to a nitrogen atom or an impurity atom that has substituted for a nitrogen atom. Therefore, it is considered effective to supply molecules with a structure consisting of a nitrogen atom or an impurity atom that has substituted for a nitrogen atom in a group III nitride crystal, bonded to a hydrogen atom.

[0088] The structure formed by bonding hydrogen atoms to nitrogen atoms or impurity atoms that have replaced nitrogen atoms in group III nitride crystals can be mainly NH, CH, and OH, but it can also be other bonding structures that play an equivalent role.

[0089] In summary, it can be concluded that if a hydrogen-containing gas with any of the above-mentioned bonding structures is supplied, it is possible to make the group III nitride crystal contain a high concentration of hydrogen.

[0090] It should be noted that while point defects of group III elements in group III nitride crystals can be determined using positron-pair annihilation, this method is hazardous due to the use of positrons generated by radioactive isotopes, making it difficult to implement easily. Furthermore, quantifying the defect density requires comparison with group III nitride crystals exhibiting very low defect densities; however, crystals with extremely low defect densities are difficult to obtain, making point defect determination of group III elements challenging. Based on these factors, the mechanism by which the addition of hydrogen reduces the absorption coefficient of group III nitride crystals is difficult to determine and ultimately remains a conjecture by the inventors.

[0091] The following provides a detailed description of the group III nitride crystal, the method for manufacturing the group III nitride crystal, and the apparatus for manufacturing the group III nitride crystal according to embodiments of the present invention.

[0092] (Implementation Method 1)

[0093] <Group-III nitride crystal>

[0094] The Group-III nitride crystal of Embodiment 1 (hereinafter sometimes referred to as crystal X) is doped with an N-type dopant and hydrogen element. The concentration of the N-type dopant in the crystal is 1×10 20 cm -3 or more. In addition, the concentration of the hydrogen element in crystal X is 1×10 19 cm -3 or more.

[0095] Crystal X has excellent conductivity by doping 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 power electronic devices and the like. In crystal X, in addition to the N-type dopant, hydrogen element is doped at a concentration of 1×10 19 em -3 or more. Thus, although crystal X contains an N-type dopant at a concentration of 1×10 20 cm -3 or more, it can have a low absorption coefficient. That is, although crystal X contains an N-type dopant at a concentration of 1×10 20 cm -3 or more, it is not easily colored. In a processing method using a laser, it is necessary to allow light to sufficiently enter the processing part of the workpiece. Therefore, in the light wavelength region used for processing, it is necessary to make the absorption coefficient of the processing part of the workpiece sufficiently low. For example, in the case of fabricating a Group-III nitride substrate from crystal X by laser processing, since crystal X has a low absorption coefficient, the laser is not easily absorbed by crystal X, and crystal X can be processed well.

[0096] The N-type dopant preferably contains at least one selected from silicon element, germanium element, and oxygen element. In this case, the conductivity of crystal X can be improved well.

[0097] The N-type dopant preferably contains oxygen element. In this case, especially when crystal X is fabricated by the OVPE method, oxygen element can be added to crystal X well.

[0098] The concentration of the N-type dopant is preferably 7×10 20 cm -3 or more and 5×10 21 cm -3 or less. In this case, the conductivity of crystal X can be further improved.

[0099] The concentration of the hydrogen element is preferably 1×10 19 cm -3 or more and 1×1020 cm -3 In this case, crystal X has superior conductivity and a lower absorption coefficient, which further prevents coloration of crystal X.

[0100] The absorption coefficient of crystal X is 60 cm⁻¹. -1 Light with the following energy is preferably located in the range below the bandgap energy value of crystal X. When processing semiconductor materials, light with energy above the bandgap 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 use a laser that outputs light with energy below the bandgap energy value of crystal X. Furthermore, particularly by using an absorption coefficient of 60 cm⁻¹ -1 The light used for processing is light with the following energy, making it less susceptible to absorption by crystal X. Therefore, crystal X can be processed particularly well, reducing material loss during the fabrication of group III nitride substrates from crystal X. Furthermore, by using an absorption coefficient of 60 cm⁻¹... -1 Processing is performed using light of the following energy, so that even when a group III nitride substrate with a thickness of 100 μm or more is manufactured from crystal X, the light used for processing can easily reach deep into the substrate from the surface of crystal X. Therefore, processing can be performed well.

[0101] It should be noted that the bandgap energy varies depending on the composition of crystal X. For example, in gallium nitride processing, processing can be performed well using a laser with an output energy of 3.39 eV, which is below the bandgap. Similarly, in aluminum nitride processing, processing can be performed well using a laser with an output energy of 6.2 eV, which is below the bandgap. There is no particular limitation on the lower limit of the light energy used in processing; for example, it can be 1 eV. By using light above 1 eV for processing, the laser is less likely to be absorbed by the high concentration of free carriers present in crystal X with a high concentration of N-type dopant, making it easier for the laser to penetrate into the crystal. In this case, the absorption coefficient of crystal X becomes 60 cm⁻¹. -1 Light with the following energies can exist in the range of above 1 eV and below the band gap energy value of crystal X.

[0102] The absorption coefficient of crystal X is 60 cm⁻¹. -1 Light with the following energies is preferably found in the range below 3.39 eV. When crystal X is gallium nitride, the absorption coefficient is 60 cm⁻¹ in the range above 1 eV and below 3.39 eV. -1 Light with the following energy is particularly effective at processing crystal X. Crystal X has an absorption coefficient of 60 cm⁻¹. -1 Light with the following energies is preferably found in the range of 1 eV or higher and below 3.39 eV.

[0103] The resistivity of crystal X is preferably 1 mΩ·cm or less. In this case, the group-III nitride substrate made of crystal X can have excellent electrical conductivity. The resistivity of crystal X is more preferably 0.7 mΩ·cm or less.

[0104] By processing crystal X, a group-III nitride substrate can be obtained. That is, the group-III nitride substrate of the present invention 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.

[0105] <Manufacturing method of group-III nitride crystal>

[0106] Next, refer to Figure 1 The manufacturing method of crystal X (group-III nitride crystal) will be described. In the following description, an example of manufacturing using a gas is described, but even in the case of manufacturing in a solution or melt, the crystal X of the present invention can be obtained.

[0107] The manufacturing method of crystal X has a step of introducing raw material gases and a step of generating and growing crystal X. In the step of introducing raw material gases, 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 element-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas are reacted, and crystal X is generated and grown on the seed substrate 201 provided on the substrate tray 202.

[0108] It should be noted that as the raw material gases, four different types of gases can be used, or three or less types of gases can be used. That is, the group-III element-containing gas, the nitrogen element-containing gas, the N-type dopant-containing gas, and the hydrogen element-containing gas can be different from each other or the same. For example, the same gas can be used as the nitrogen element-containing gas and the hydrogen element-containing gas. In addition, the same gas can be used as the group-III element-containing gas and the N-type dopant-containing gas.

[0109] In the manufacturing method of the group-III nitride crystal of the present Embodiment 1, 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 relatively high. In addition, the growth rate of crystal X can be increased. In the case of manufacturing gallium nitride, the group-III element-containing gas particularly preferably contains at least one of Ga2O or GaCl.

[0110] In the manufacturing method of this embodiment, when using Group III element oxide gas or Group III element halide gas 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 easier to prevent the gas from becoming unstable in environments other than high temperatures, 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 the steps of reacting a Group III element-containing material with an oxidizing gas or a halide gas and a step of reducing a Group III element oxide solid with hydrogen to generate a Group III element oxide gas.

[0111] The oxidizing gas preferably includes at least one of water vapor and oxygen. Additionally, the halide gas preferably includes HCl.

[0112] Examples of reactions between materials containing Group III elements and oxidizing gases include:

[0113]

[0114] Examples of reactions between materials containing Group III elements and halide gases include:

[0115]

[0116] Examples of reactions between solid oxides of Group III elements and hydrogen include, for example:

[0117]

[0118] <Nitrogen-containing gases>

[0119] In the method for manufacturing Group III nitride crystals according to this embodiment, the nitrogen-containing gas preferably includes at least one selected from ammonia, hydrazine, and dimethylhydrazine. Ammonia, hydrazine, and dimethylhydrazine have boiling points below 200°C, and therefore can be more easily supplied to the reaction vessel in a gaseous state, resulting in higher reactivity. Therefore, crystal X can be grown more effectively.

[0120] <Gas containing N-type dopants>

[0121] In the method for manufacturing a Group III nitride crystal according to this embodiment, the N-type dopant gas preferably comprises at least one selected from silicon-containing gas, germanium-containing gas, and oxygen-containing gas. In this case, it can be easily supplied to the reaction vessel in a gaseous state at room temperature, and furthermore, it exhibits excellent reactivity, thus enabling the crystal X to grow well. The N-type dopant gas more preferably comprises an oxygen-containing gas.

[0122] <Silicon-containing gas>

[0123] The silicon-containing gas preferably comprises at least one selected from SiH4, SiH3Cl, and SiH2Cl2. In this case, the silicon-containing gas, which is in a gaseous state at room temperature, can be easily supplied into the reaction vessel, and it has high reactivity, thus enabling crystal X to grow well.

[0124] <Germanium-containing gas>

[0125] The germanium-containing gas preferably comprises at least one selected from GeH4, GeH3Cl, and GeH2Cl2. In this case, the germanium-containing gas, which is in a gaseous state at room temperature, can be easily supplied into the reaction vessel, and it has high reactivity, thus enabling the crystal X to grow well.

[0126] <Oxygen-containing gases>

[0127] The oxygen-containing gas preferably comprises at least one selected from water vapor, oxygen, N2O gas, NO gas, NO2 gas, CO gas, and CO2 gas. In this case, the oxygen-containing gas, which is in a gaseous state at room temperature, can be easily supplied into the reaction vessel, and it has high reactivity, thus enabling crystal X to grow well.

[0128] The N-type dopant gas particularly preferably comprises at least one selected from GeO gas, Ga2O gas, and In2O gas. In this case, the N-type dopant gas can be readily generated at a temperature close to the manufacturing temperature of crystal X, and it has high reactivity, thus enabling crystal X to grow particularly well.

[0129] <Hydrogen-containing gas>

[0130] In the method for manufacturing Group III nitride crystals according to this embodiment, it is preferable to contain at least one selected from NH bonds, CH bonds, and OH bonds. In this case, hydrogen-containing gas, which is in a gaseous state at room temperature, can be easily supplied to the reaction vessel, and crystal X can be grown well due to its excellent reactivity. In addition, by containing at least one selected from NH bonds, CH bonds, and OH bonds in the hydrogen-containing gas, coloration of crystal X can be prevented, and the absorption coefficient can be further reduced. It is presumed that this is because hydrogen atoms can be well attached to the Group III element vacancy defects in crystal X.

[0131] <Gas with NH bonds>

[0132] The gas containing NH bonds preferably includes at least one selected from ammonia, hydrazine, methylamine, and ethylamine. In this case, the NH-bonded gas, which is in a gaseous state at room temperature, can be readily supplied into the reaction vessel, and due to its excellent reactivity, crystal X can grow particularly well.

[0133] <Gas with CH bonds>

[0134] The gas containing CH bonds preferably includes at least one selected from methane, ethane, propane, butane, ethylene, acetylene, methylamine, and ethylamine. In this case, the CH-bonded gas, which is in a gaseous state at room temperature, can be readily supplied into the reaction vessel, and due to its excellent reactivity, crystal X can grow particularly well.

[0135] <Gas with OH bonds>

[0136] The gas containing OH bonds preferably includes at least one selected from water vapor, hydrogen peroxide, methanol, and ethanol. In this case, since the boiling point of the gas containing CH bonds is below 160°C, the gas containing CH bonds can be easily supplied into the reaction vessel, and due to its excellent reactivity, crystal X can grow particularly well.

[0137] The hydrogen-containing gas particularly preferably includes at least one selected from ammonia, hydrazine, methylamine, ethylamine, methane, ethane, propane, butane, ethylene, acetylene, water vapor, hydrogen peroxide, methanol, and ethanol.

[0138] It should be noted that in the method for manufacturing group III nitride crystals according to this embodiment, different gases can be used as the group III element gas, the nitrogen-containing gas, the N-type dopant gas, the hydrogen-containing gas, and the carrier gas, or the same gas can be used. For example, Ga2O gas can be used as the group III element gas, and Ga2O can also be used as the N-type dopant gas. In this way, when using the same gas, the gas introduction path can sometimes be summarized, which can simplify the manufacturing equipment.

[0139] In the method for manufacturing group III nitride crystals according to this embodiment, in the growth step of growing crystal X, from the viewpoint of the reactivity of the gas used in the manufacturing process, the temperature at which the gas containing group III elements reacts with the gas containing nitrogen elements is preferably 700°C or higher and 1500°C or lower. From the viewpoint of ensuring crystal growth rate and improving crystal quality, it is more preferably 1000°C or higher and 1400°C or lower.

[0140] The method for manufacturing group III nitride crystals in this embodiment can, for example, be achieved by using... Figure 1 The apparatus shown is used to manufacture group III nitride crystals. It should be noted that... Figure 1 The apparatus shown for manufacturing group III nitride crystals is merely an example; any apparatus capable of manufacturing the crystal X of the present invention is not limited to this. Figure 1Manufacturing apparatus. In this figure, for ease of understanding, there are cases where the sizes and ratios of each part are different from the actual ones. In addition, sometimes materials that need to be pre - configured in the manufacturing apparatus when manufacturing crystal X are shown.

[0141] <Manufacturing Apparatus for Group - III Nitride Crystals>

[0142] This manufacturing apparatus for group - III nitride crystals is connected with a hydrogen - containing element gas introduction pipe 102, an N - type dopant gas introduction pipe 103, a nitrogen - containing element gas introduction pipe 104, a group - III element gas introduction pipe 105, and a gas exhaust pipe 109 on a reaction vessel 101. Inside the reaction vessel 101, a substrate tray 202 provided with a seed substrate 201 is arranged. It should be noted that the arrangements of the hydrogen - containing element gas introduction pipe 102, the N - type dopant gas introduction pipe 103, the nitrogen - containing element gas introduction pipe 104, and the group - III element gas introduction pipe 105 are not limited to Figure 1 the arrangements shown.

[0143] As described above, as raw material gases, four different types of gases can be used, or three or less types of gases can be used. Therefore, in Figure 1 the manufacturing apparatus shown, four introduction pipes, namely the hydrogen - containing element gas introduction pipe 102, the N - type dopant gas introduction pipe 103, the nitrogen - containing element gas introduction pipe 104, and the group - III element gas introduction pipe 105, are provided, but it is not limited to this. The manufacturing apparatus can have three or less introduction pipes.

[0144] The group - III element gas reacts with the nitrogen - containing element gas, and crystal X grows on the seed substrate 201. The unreacted gases and by - product gases are discharged from the gas exhaust pipe 109.

[0145] The group - III element gas is generated by reacting a group - III element material 107 with a group - III element gas - generating gas introduced from a group - III element gas - generating gas introduction pipe 108 in a group - III element gas generation part 106.

[0146] In addition, in the introduction pipes or reaction parts of each gas, heating can be performed through each heater to adjust so as to achieve the desired reaction state of the gas or the growth conditions of crystal X. For example, as Figure 1As shown, at least one of the following can be provided: a reaction vessel heater 111 adjacent to the reaction vessel 101, a hydrogen-containing gas inlet pipe heater 112 adjacent to the hydrogen-containing gas inlet pipe 102, an N-type dopant gas inlet pipe heater 113 adjacent to the N-type dopant gas inlet pipe 103, a nitrogen-containing gas inlet pipe heater 114 adjacent to the nitrogen-containing gas inlet pipe 104, and a group III element gas generating section heater 115 adjacent to the group III element gas generating section 106.

[0147] Materials containing Group III elements

[0148] The material 107 containing a group III element is a material containing at least one selected from aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). Furthermore, from an operational viewpoint, it is preferable to use a material that is solid or liquid at room temperature as the material 107 containing a group III element. Examples of group III element materials 107 that are solid at room temperature include Al₂O₃, Ga₂O₃, In₂O₃, Tl₂O₃, Al, In, and Tl. Examples of group III element materials 107 that are liquid at room temperature include Ga.

[0149] Examples of gases introduced into the Group III element gas generating section 106 for generating Group III element gases include hydrogen, water vapor, and hydrogen chloride. Furthermore, from the viewpoint of reaction control, the gas introduced into the Group III element gas generating section 106 is preferably mixed with a carrier gas before introduction.

[0150] <Carrier Gas>

[0151] There are no particular limitations on the carrier gas; examples include nitrogen, hydrogen, argon, and helium. A mixture of these gases can also be used as a carrier gas.

[0152] <Substrate>

[0153] The material of the seed substrate 201 is not particularly limited and can be appropriately selected according to the characteristics of the crystal X to be manufactured. For example, the seed substrate 201 is preferably a single crystal substrate having the same elemental composition ratio as the crystal X to be manufactured. Examples of materials for the seed substrate 201 include sapphire, ScAlMgO4, group III nitrides, LiAlO2, and ZnO.

[0154] It should be noted that the present invention is not limited to the embodiments described above. For example, the above-described constituent elements can be combined arbitrarily, or other embodiments implemented by removing some of the above-described constituent elements can be used as embodiments of the present invention.

[0155] (Example)

[0156] The methods for manufacturing group III nitride crystals of Examples 1-4 and Comparative Examples will be described.

[0157] In Example 1, gallium nitride crystal, a group III nitride crystal, was manufactured using gases. Ga₂O gas was used as the group III element-containing gas and the N-type dopant-containing gas; ammonia gas was used as the nitrogen-containing gas; and ammonia gas was used as the hydrogen-containing gas. Ga was used as the group III element-containing material, and oxygen was used as the gas for generating the group III element-containing gas. Gallium nitride crystal was used as the seed substrate 201.

[0158] First, Ga is placed in the group III element gas generation section 106, and Ga₂O is generated using oxygen. The generated Ga₂O is supplied to the reaction vessel 101 from the group III element gas inlet pipe 105. Furthermore, ammonia gas, as a nitrogen-containing gas, is introduced into the reaction vessel 101 from the nitrogen-containing gas inlet pipe 104. Additionally, ammonia gas, as a hydrogen-containing gas, is introduced into the reaction vessel 101 from the hydrogen-containing gas inlet pipe 102, thereby producing group III nitride crystals.

[0159] The manufacturing conditions for Group III nitride crystals are described in detail. First, each heater (111, 112, 113, 114, 115) is heated. After the temperature of the Group III element gas generation section 106 reaches 1100°C and the temperature of the reaction vessel reaches 1200°C, oxygen is introduced into the Group III element gas generation section 106 at a flow rate of 20 sccm, and a mixture of nitrogen and hydrogen is introduced as a carrier gas at a flow rate of 5 slm. This mixture reacts on Ga placed in the Group III element gas generation section 106 to generate Ga₂O gas. The resulting Ga₂O gas is then introduced into the reaction vessel 101 as a Group III element gas and an N-type dopant gas. Furthermore, the flow rate of ammonia gas (as a nitrogen-containing gas) is set to 0.5 slm, and the flow rate of ammonia gas (as a hydrogen-containing gas) is set to 1 slm. A mixture of nitrogen and hydrogen gas (as their carrier gases) is introduced into the reaction vessel 101 at a flow rate of 40 slm. Inside reaction vessel 101, Ga₂O gas reacts with ammonia gas to generate gallium nitride crystals on seed substrate 201. The gallium nitride crystal generation reaction is carried out for 6 hours. In this way, a gallium nitride crystal with a thickness of 300 μm is fabricated as an epitaxial layer on a GaN substrate.

[0160] For the gallium nitride crystal of Example 2, the flow rate of ammonia gas, which is a hydrogen-containing gas, was set to 1.5 slm, and otherwise the manufacturing process was carried out in the same manner as in Example 1.

[0161] For the gallium nitride crystal of Example 3, methane gas was used as the hydrogen-containing gas, and otherwise the manufacturing process was the same as that of Example 1 above.

[0162] For the gallium nitride crystal of Example 4, water vapor was used as the hydrogen-containing gas, and the flow rate of the water vapor was set to 10 sccm. Otherwise, it was manufactured in the same manner as in Example 1.

[0163] The gallium nitride crystal of the comparative example was manufactured in the same manner as in Example 1 above, except that it did not use hydrogen-containing gas.

[0164] The crystals manufactured in Examples 1-4 were ground to a thickness of 150 μm to create a self-supporting gallium nitride substrate consisting only of a crystal layer. In the Comparative Example, the crystals manufactured were ground to a thickness of 200 μm to create a self-supporting gallium nitride substrate consisting only of a crystal layer.

[0165] The substrates of Examples 1-4 and the Comparative Examples obtained in this way were used to evaluate the properties shown in Table 1. It should be noted that, regarding the absorption coefficient, the minimum value of the absorption coefficient was measured among the absorption coefficients of light with energies in the range of energy below 3.39 eV for the bandgap energy of gallium nitride.

[0166] Table 1

[0167]

[0168] The concentration of impurities in the gallium nitride crystal fabricated in Example 1 was analyzed by SIMS, and the oxygen concentration was found to be 7.2 × 10⁻⁶. 20 atoms / cm 3 The concentration of hydrogen is 1.4 × 10⁻⁶. 19 atoms / cm 3 Additionally, the resistivity is 6.40 × 10⁻⁶. -4 The minimum absorption coefficient is 33 cm⁻¹ relative to light with an energy of 1.85 eV. -1 The absorption coefficient is [not specified]. In Example 1, the concentrations of oxygen and hydrogen are high, the resistivity is low, and the absorption coefficient is also small.

[0169] The concentration of impurities in the gallium nitride crystal fabricated in Example 2 was analyzed by SIMS, and the oxygen concentration was found to be 7.1 × 10⁻⁶. 20 atoms / cm 3 The concentration of hydrogen is 1.8 × 10⁻⁶. 19 atoms / cm 3 Additionally, the resistivity is 5.76 × 10⁻⁶. -4 The minimum absorption coefficient is Ω·cm, which is 26 cm⁻¹ relative to light with an energy of 1.92 eV. -1 The absorption coefficient was [not specified]. Compared to Example 1, by increasing the supply of ammonia gas containing hydrogen, the hydrogen concentration in the crystal increased, and the absorption coefficient decreased.

[0170] The concentration of impurities in the gallium nitride crystal fabricated in Example 3 was analyzed by SIMS, and the oxygen concentration was found to be 9.4 × 10⁻⁶. 20 atoms / cm 3 The concentration of hydrogen is 7.2 × 10⁻⁶. 19 atoms / cm 3 Additionally, the resistivity is 5.93 × 10⁻⁶. -4 The minimum absorption coefficient is Ω·cm, which is 18cm for light with an energy of 1.94 eV. -1 The absorption coefficient.

[0171] The concentration of impurities in the gallium nitride crystal fabricated in Example 4 was analyzed by SIMS, and the oxygen concentration was found to be 1.9 × 10⁻⁶. 21 atoms / cm 3 The concentration of hydrogen is 6.5 × 10⁻⁶. 19 atoms / cm 3 Additionally, the resistivity is 5.65 × 10⁻⁶. -4 The minimum absorption coefficient is Ω·cm, and it is 28cm² relative to light with an energy of 1.92 eV. -1 The absorption coefficient.

[0172] The concentration of impurities in the gallium nitride crystals fabricated in the comparative example was analyzed using SIMS, and the oxygen content was found to be 4.3 × 10⁻⁶. 20 atoms / cm 3 The hydrogen level was below the detection limit of 1.2 × 10⁻⁶. 17 atoms / cm 3 Additionally, the resistivity is 7.67 × 10⁻⁶. -4 The minimum absorption coefficient is 74 cm⁻¹ relative to light with an energy of 1.33 eV. -1 The absorption coefficient.

[0173] As shown in Table 1, the oxygen concentration of any group III nitride crystals produced in Examples 1-4 and the Comparative Examples is 1 × 10⁻⁶. 20 atoms / cm 3 The high concentration results in a low resistivity of less than 1 mΩ·cm. Furthermore, the concentration of hydrogen is 1 × 10⁻⁶. 19 atoms / cm 3 The crystals of Examples 1 to 4 above exhibit an absorption coefficient of 60 cm⁻¹ in the range below the band gap energy value. -1 Light with the following energy. On the other hand, in the comparative example, the minimum absorption coefficient in the range below the band gap energy value is 74 cm⁻¹. -1 Therefore, it can be seen that the absorption coefficient of the crystal in the embodiment is significantly smaller compared to the crystal in the comparative example.

[0174] The absorption coefficients of the group III nitride crystals manufactured in Examples 1-4 and the Comparative Examples are shown in the figure. Figure 2 In the chart. Figure 2 This indicates the relationship between the energy value of light and the absorption coefficient for that light. For example... Figure 2 As shown, in Examples 1-4, where the hydrogen concentration in the crystal is more than two orders of magnitude higher than the comparative examples, the absorption coefficient is low over a wide range in the energy region below the bandgap energy of 3.39 eV. It should be noted that... Figure 2 In the comparative example, the absorption coefficient of the crystal was too high in the energy region above 2.19 eV, so the measurement could not be performed satisfactorily.

[0175] Based on the above results, in the group III nitride crystal of the present invention, even when the concentration of N-type dopant in the crystal is increased to reduce resistivity, the absorption coefficient in a wide energy region can be reduced by containing a specific concentration or higher of hydrogen in the crystal. Therefore, laser-based internal processing of the crystal is possible.

[0176] It should be noted that, in this invention, there is a possibility of appropriately combining any of the above-described various implementation methods and / or embodiments, which can achieve the effects of each implementation method and / or embodiment.

[0177] Industrial availability

[0178] As described above, the group III nitride crystal, the method for manufacturing group III nitride crystal, and the apparatus for manufacturing group III nitride crystal according to the present invention can process group III element nitride crystals with high conductivity in a manner with low material loss, and fabricate group III nitride semiconductor substrates, which can be expected to improve the performance and reduce the cost of high-frequency or high-output power electronic devices.

Claims

1. A group III nitride crystal, wherein, doped with an N-type dopant and hydrogen, The concentration of the N-type dopant is 7 x 10 20 cm -3 above and 5 x 10 21 cm -3 below. The concentration of the hydrogen element is 1 x 10 19 cm -3 Above.

2. The Group III nitride crystal of claim 1, wherein, the N-type dopant includes at least one selected from a silicon element, a germanium element, and an oxygen element.

3. The Group III nitride crystal of claim 2, wherein, the N-type dopant includes an oxygen element.

4. The Group III nitride crystal of claim 1, wherein, The light absorption coefficient becomes 60 cm -1 light having the following energy.

5. The Group III nitride crystal of claim 1, wherein, The light absorption coefficient of the Group III nitride crystal becomes 60 cm -1 The following energy light exists in a range lower than 3.39 eV.

6. A Group III nitride crystal, wherein, doped with an N-type dopant and hydrogen, The concentration of the N-type dopant is 1 x 10 20 cm -3 The above, The concentration of the hydrogen element is 1 x 10 19 cm -3 The above, the III-nitride crystal has a resistivity of 1 mΩ-cm or less.

7. A III-nitride substrate provided with the III-nitride crystal according to any one of claims 1 to 6.

8. The Ill-nitride substrate of claim 7, wherein, a thickness of 100 μm or more.

9. A method for producing the III-nitride crystal according to claim 1 or 6, comprising: a step of introducing a III-group element-containing gas, a nitrogen element-containing gas, an N-type dopant-containing gas, and a hydrogen element-containing gas; and a step of causing the introduced III-group element-containing gas, nitrogen element-containing gas, N-type dopant-containing gas, and hydrogen element-containing gas to react, and causing a III-nitride crystal to be generated and grown on a seed substrate.

10. The method of producing Group III nitride crystals according to claim 9, wherein the N-type dopant-containing gas includes at least one selected from a silicon element-containing gas, a germanium element-containing gas, and an oxygen element-containing gas.

11. The method of producing Group III nitride crystals according to claim 10, wherein the N-type dopant-containing gas includes the oxygen element-containing gas.

12. The method of producing Group III nitride crystals according to claim 9, wherein the hydrogen element-containing gas contains at least one selected from an N-H bond, a C-H bond, and an O-H bond in a molecule.

13. The method of producing Group III nitride crystals according to claim 9, wherein the hydrogen element-containing gas includes at least one selected from 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.

14. The method of producing Group III nitride crystals according to claim 9, wherein the nitrogen element-containing gas includes at least one selected from ammonia gas, hydrazine gas, and dimethylhydrazine gas.

15. The method of producing Group III nitride crystals according to claim 9, wherein the III-group element-containing gas includes at least one of an oxide of a III-group element and a halide of a III-group element.

16. The method of producing Group III nitride crystals according to claim 9, wherein the III-group element-containing gas includes at least one of Ga2O and GaCl.

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