Patent Application
20180094361
The present invention relates to a method for producing a Group III nitride crystal, a semiconductor apparatus, and an apparatus for producing a Group III nitride crystal.
A Group III nitride semiconductor (also called a Group III nitride compound semiconductor or a GaN semiconductor) such as gallium nitride (GaN) is used widely as materials for various semiconductor devices such as a laser diode (LD) and a light-emitting diode (LED). For example, the laser diode (LD) that emits blue light is applied to a high-density optical disc or a display, and a light-emitting diode (LED) that emits blue light is applied to a display or illumination. Moreover, an ultraviolet LD is expected to be applied to biotechnology and the like, and an ultraviolet LED is expected as an ultraviolet source of a fluorescent lamp.
As a common method for producing a Group III nitride (e.g., GaN) crystal substrate, there is vapor phase epitaxy such as hydride vapor phase epitaxy (HVPE) (Patent Document 1) and metalorganic chemical vapor deposition (MOCVD), for example. On the other hand, as a method that can produce a Group III nitride single crystal of higher quality, there is also liquid phase epitaxy. This liquid phase epitaxy had a problem in that the method was required to be performed under high temperature and high pressure. However, with recent improvements, the method can be performed under relatively low temperature and relatively low pressure and is suitable for mass production (for example, Patent Documents 2 and 3). Furthermore, there is a method that uses liquid phase epitaxy and vapor phase epitaxy in combination (Patent Document 4).
With recent increase in size and performance of semiconductor apparatuses, there is a demand for producing a Group III nitride crystal of high quality with few defects (e.g., crack, dislocation, etc.).
The liquid phase epitaxy allows a Group III nitride crystal with few defects to be produced easily, however, it requires a long period of time for crystal growth.
On the other hand, the vapor phase epitaxy achieves a high crystal growth speed, however, it is difficult to produce a Group III nitride crystal of high quality with few defects.
Hence, the present invention is intended to provide a method for producing a Group III nitride crystal that produces a Group III nitride crystal of high quality with few defects by vapor phase epitaxy. Furthermore, the present invention provides a semiconductor apparatus produced by the method for producing a Group III nitride crystal and an apparatus for producing a Group III nitride crystal for use in the method for producing a Group III nitride crystal.
In order to achieve the above object, the present invention provides a method for producing a Group III nitride crystal (hereinafter, it may be simply referred to as the “production method according to the present invention”), including a step of: causing Group III element-containing gas to react with nitrogen-containing gas to generate a Group III nitride crystal, wherein in the Group III nitride crystal generation step, the reaction is performed in the presence of a carbon-containing substance.
The present invention also provides a method for producing a semiconductor apparatus including a Group III nitride crystal, including a step of: producing a Group III nitride crystal by the production method according to the present invention, wherein the Group III nitride crystal is a semiconductor.
The present invention also provides an apparatus for producing a Group III nitride crystal for use in the production method according to the present invention, including: a Group III nitride crystal generation unit configured to perform the Group III nitride crystal generation step.
According to the production method of the present invention, a Group III nitride crystal of high quality with few defects can be produced by vapor phase epitaxy. Furthermore, the present invention provides a semiconductor apparatus that can be produced by the production method according to the present invention and a Group III nitride crystal production apparatus that can be used in the production method according to the present invention.
The present invention is described below with reference to examples. The present invention, however, is not limited by the following description.
In the method for producing a Group III nitride crystal of the present invention, for example, the carbon-containing substance may be at least one selected from the group consisting of elementary carbon, solid elementary carbon, graphite, carbon nanotube, fullerene, a carbon compound, a solid carbon compound, carbon-containing gas, carbon monoxide (CO) gas, and hydrocarbon gas.
In the method for producing a Group III nitride crystal of the present invention, the nitrogen-containing gas may be at least one selected from the group consisting of N2, NH3, hydrazine gas, and alkylamine gas, for example.
The method for producing a Group III nitride crystal of the present invention may further include a step of generating the Group III element-containing gas, for example. The Group III element-containing gas generation step may be a step of causing Group III element metal to react with an oxidizing agent to generate the Group III element-containing gas, for example. Hereinafter, such a method for producing a Group III nitride crystal of the present invention may also be referred to as a “Group III nitride crystal production method (A)”. In the Group III nitride crystal production method (A), the Group III element-containing gas generated in the Group III element-containing gas generation step is, for example, gas produced by oxidation of Group III element metal (hereinafter, also referred to as Group III element metal oxidation product gas). Hereinafter, the Group III element-containing gas generation step of causing Group III element metal to react with an oxidizing agent to generate Group III element metal oxidation product gas (Group III element-containing gas) may also be referred to as a “Group III element metal oxidation product gas generation step”.
As described above, the method for producing a Group III nitride crystal of the present invention may further include a step of generating the Group III element-containing gas. The Group III element-containing gas generation step may be a step of causing Group III element oxide to react with reducing gas to generate the Group III element-containing gas, for example. Hereinafter, such a method for producing a Group III nitride crystal of the present invention may also be referred to as a “Group III nitride crystal production method (B)”. In the Group III nitride crystal production method (B), the Group III element-containing gas generated in the Group III element-containing gas generation step is, for example, reduced product gas of the Group III element oxide. Hereinafter, the Group III element-containing gas generation step of causing Group III element oxide to react with reducing gas to generate reduced product gas of Group III element oxide (Group III element-containing gas) may also be referred to as “a reduced product gas generation step”.
In the Group III nitride crystal production method (A) in the production method according to the present invention, the Group III element metal is preferably at least one selected from the group consisting of gallium, indium and aluminum, and is particularly preferably gallium.
In the Group III element metal oxidation product gas generation step, preferably, the Group III element metal is caused to react with the oxidizing agent in a heated state. Furthermore, more preferably, the Group III element metal oxidation product gas is Group III element metal oxide gas. In this case, still more preferably, the Group III element metal is gallium and the Group III element metal oxide gas is Ga2O gas.
In the Group III nitride crystal production method (A), preferably, the oxidizing agent is an oxygen-containing compound. Also, in the Group III nitride crystal production method (A), preferably, the oxidizing agent is oxidizing gas.
In the Group III nitride crystal production method (A), the oxidizing gas is preferably at least one selected from the group consisting of H2O gas, O2 gas, CO2 gas, and CO gas, and is particularly preferably H2O gas.
In the Group III nitride crystal production method (A), the nitrogen-containing gas is preferably at least one selected from the group consisting of N2, NH3, hydrazine gas, and alkylamine gas.
In the method for producing a Group III nitride crystal, the volume of the oxidizing gas is not particularly limited, and the volume relative to the total volume of the oxidizing gas and the nitrogen-containing gas is, for example, more than 0% and less than 100%, preferably 0.001% or more and less than 100%, and more preferably in the range from 0.01% to 95%, still more preferably in the range from 0.1% to 80%, and still more preferably in the range from 0.1% to 60%.
In the Group III nitride crystal production method (A), preferably, the reaction takes place in the presence of reducing gas in a reaction system. More preferably, the reducing gas is hydrogen-containing gas. Still more preferably, the reducing gas is at least one selected from the group consisting of H2 gas, carbon monoxide (CO) gas, hydrocarbon gas, H2S gas, SO2 gas, and NH3 gas. In the method for producing a Group III nitride crystal, still more preferably, the oxidizing agent is the oxidizing gas and the reaction is performed after being mixed with the reducing gas in the oxidizing gas.
In the method for producing a Group III nitride crystal, more preferably, the reaction in the presence of the reducing gas is performed at a temperature of 650° C. or higher.
In the Group III nitride crystal production method (A), the Group III nitride crystal may be generated in a condition under pressure, in a condition under reduced pressure, or in conditions other than these conditions.
In the reduced product gas generation step of the Group III nitride crystal production method (B) according to the present invention, preferably, the Group III element oxide is caused to react with the reducing gas in a heated state.
In the Group III nitride crystal production method (B), preferably, the Group III element oxide is Ga2O3, the reduced product gas is Ga2O gas, and the Group III nitride crystal is a GaN crystal.
In the Group III nitride crystal production method (B), preferably, the reduced product gas generation step is performed in an atmosphere of mixed gas of the reducing gas and inert gas. More preferably, the proportion of the reducing gas relative to the total amount of the mixed gas is 0.1 vol. % or more and less than 100 vol. % and the proportion of the inert gas relative to the total amount of the mixed gas is more than 0 vol. % and 99.9 vol. % or less. Still more preferably, the inert gas contains nitrogen gas.
In the Group III nitride crystal production method (B), preferably, the nitrogen-containing gas contains ammonia gas.
The crystal generation step of the Group III nitride crystal production method (B) may be performed, for example, in a condition under pressure. The present invention, however, is not limited thereto and the crystal generation step may be performed in a condition under reduced pressure or in conditions other than these conditions.
Preferably, the production method according to the present invention further includes a slicing step of slicing the Group III nitride crystal to provide at least one Group III nitride crystal substrate.
Furthermore, preferably, the production method according to the present invention further includes a step of polishing the surface of the substrate. In the method for producing a Group III nitride crystal, preferably, the Group III nitride crystal is produced by vapor phase epitaxy on the surface of the substrate polished in the polishing step.
In the production method according to the present invention, the Group III nitride crystal is preferably a Group III nitride crystal represented by AlxGayIn1-x-yN (0≦x≦1, 0≦y≦1, x+y≦1) and particularly preferably GaN.
In the production method according to the present invention, preferably, the produced Group III nitride crystal has a major axis of 15 cm or more, although it is not particularly limited. Furthermore, preferably, the produced Group III nitride crystal has a dislocation density of 1.0×107 cm−2 or less, although it is not particularly limited. Moreover, in the produced Group III nitride crystal, preferably, a half width of each of a symmetric reflection component (002) and an asymmetric reflection component (102) by an X-ray rocking curve method (XRC) is 300 seconds or less, although it is not particularly limited. The concentration of the oxygen contained in the Group III nitride crystal produced may be 1×1020 cm−3 or less. The present invention, however, is not limited thereto and the concentration of the oxygen contained in the produced Group III nitride crystal may be more than 1×1020 cm−3. The method for measuring the half width and the dislocation density by the XRC is not limited to particular methods, and the methods described in Examples below can be adopted.
More specifically, the production method according to the present invention can be performed, for example, as follows.
First, prior to the Group III nitride crystal generation step, a substrate for crystal growth is prepared. On the surface of the substrate, a Group III nitride crystal can be generated and grown.
The substrate is not limited to particular substrates and may be, for example, the same as or similar to a substrate for use in common vapor phase epitaxy. The substrate can be selected appropriately according to the form or the like of a Group III nitride crystal to be generated thereon. Examples of the material for the substrate include sapphire, Group III nitride (e.g., AlxGa1-xN (0<x≦1)), gallium arsenide (GaAs), silicon (Si), silicon carbide (SiC), magnesium oxide (MgO), zinc oxide (ZnO), gallium phosphide (GaP), zirconium diboride (ZrB2), lithium dioxogallate (LiGaO2), BP, MoS2, LaAlO3, NbN, MnFe2O4, ZnFe2O4, ZrN, TiN, MgAl2O4, NdGaO3, LiAlO2, ScAlMgO4, and Ca8La2(PO4)6O2. Among them, sapphire is particularly preferable from the viewpoint of costs and the like. In the present invention, “sapphire” denotes an aluminum oxide crystal or a crystal containing aluminum oxide as a main component, unless otherwise stated.
The substrate may include an underlayer (substrate body) and a seed crystal disposed thereon. The form of the seed crystal is not limited to particular forms, and the seed crystal can be in the shape of a layer, a needle, a feather, or a plate, for example. The material for the underlayer (substrate body) is not limited to particular materials, and can be, for example, as described above. The material for the seed crystal is not limited to particular materials, and examples thereof include Group III nitride (e.g., AlxGa1-xN (0<x≦1)), oxide of the AlxGa1-xN (0<x≦1), diamond-like carbon, silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, aluminum oxynitride, silicon carbide, yttrium oxide, yttrium aluminum garnet (YAG), tantalum, rhenium, and tungsten.
The material for the substrate or the seed crystal may be, for example, the same as or different from the material for the Group III nitride crystal of the present invention to be grown thereon, and is preferably the same as the material for the Group III nitride crystal of the present invention to be grown thereon. For example, a sapphire substrate and a Group III nitride crystal are largely different in the lattice constant, the thermal expansion coefficient, and the like. Thus, when a Group III nitride crystal is directly grown on a sapphire substrate by vapor phase epitaxy, defects such as a distortion, a dislocation, warping, and the like may be caused in the Group III nitride crystal. In this regard, when a substrate of the same material as a Group III nitride crystal (e.g., GaN or the like) to be produced is used or a seed crystal having the same material as a Group III nitride crystal (e.g., GaN or the like) to be produced is formed on the substrate (e.g., sapphire or the like), the defects such as a distortion, a dislocation, warping, and the like can be inhibited or prevented. For example, by forming a crystal on an underlayer (substrate body) using the above-described material for seed crystal, the seed crystal can be disposed on the underlayer. Examples of such a method include the metalorganic vapor phase epitaxy (MOVPE method), the molecular beam epitaxy (MBE method), the halide vapor phase epitaxy (HVPE method), and the liquid phase epitaxy (LPE method). Among them, the liquid phase epitaxy is preferable from the viewpoint of obtaining a seed crystal of few defects such as a dislocation and the like. The liquid phase epitaxy can be, for example, a sodium flux method.
An apparatus (LPE apparatus) for use in the liquid phase epitaxy is not limited to particular apparatuses and may be the same as a common LPE apparatus, for example. Specifically, for example, the apparatus may be an LPE apparatus or the like described in Patent Document 3 (Japanese Patent No. 4588340).
Next, the Group III nitride crystal generation step of causing Group III element-containing gas to react with nitrogen-containing gas to generate a Group III nitride crystal is performed. According to the present invention, as described above, in the Group III nitride crystal generation step, the reaction is performed in the presence of a carbon-containing substance.
As described above, the method for producing a Group III nitride crystal of the present invention may include a Group III element-containing gas generation step of generating the Group III element-containing gas prior to the Group III nitride crystal generation step as described above.
In the method for producing a Group III nitride crystal of the present invention, as described above, the Group III element-containing gas generation step may be a step of causing Group III element metal to react with an oxidizing agent to generate the Group III element-containing gas (Group III nitride crystal production method (A)). Also, in the method for producing a Group III nitride crystal of the present invention, as described above, the Group III element-containing gas generation step may be a step of causing Group III element oxide to react with reducing gas to generate the Group III element-containing gas (Group III nitride crystal production method (B)). The Group III nitride crystal production methods (A) and (B) can be performed as described below, for example.
The shape of the first container is not limited to particular shapes. Examples of the shape of the first container include a cylinder, a quadratic prism, a triangular prism, and a shape created by combining these shapes. Examples of the material for forming the first container include quartz, alumina, aluminum titanate, mullite, tungsten, and molybdenum. A self-made first container or a commercially available first container may be used. The commercially available first container can be, for example, the “quartz reaction tube” (product name) produced by PHOENIX TECHNO.
The shape of the second container is not limited to particular shapes. Examples of the shape of the second container include those described for the first container. Examples of the material for forming the second container include quartz, tungsten, stainless, molybdenum, aluminum titanate, mullite, and alumina. A self-made second container or a commercially available second container may be used. The commercially available second container can be, for example, the “SUS316BA tube” (product name) produced by Mecc Technica Co.
Conventionally known heating units can be used as the first heating unit and the second heating unit. Examples of the heating unit include ceramic heaters, high frequency heaters, resistance heaters, and light collecting heaters. One type of the heating units may be used alone or two or more of them may be used in combination. Preferably, the first heating unit and the second heating unit are each independently controlled.
The configuration of the production apparatus for use in the method for producing a Group III nitride crystal is not limited to those shown in FIGS. 1, 4, and 6. For example, the heating units 109a, 109b, 200a, and 200b and the substrate support 103 can be omitted. However, from the viewpoint of reactivity and operability, the production apparatus is preferably provided with these components. Furthermore, the production apparatus for use in the production method of the present invention may be provided with other components in addition to the above-described components. Examples of other components include a unit configured to control the temperatures of the first heating unit and the second heating unit and a unit configured to adjust the pressure and the introduction amount of the gas used in each step.
The production apparatus for use in the Group III nitride crystal production method (A) can be produced by assembling the above-described components and other components as needed according to a conventionally known method, for example.
Next, steps, reaction conditions, materials to be used, and the like in the Group III nitride crystal production method (A) are described. The present invention, however, is not limited by the following description. A mode for carrying out the Group III nitride crystal production method (A) is described below with reference to the production apparatus shown in
First, as shown in
Next, as shown in
Furthermore, a ternary or higher nitride crystal produced using two or more kinds of Group III element metals can be, for example, a crystal represented by GaxIn1-xN (0<x<1). For generating a ternary or higher nitride crystal, it is preferable to generate reduced product gas of at least two kinds of Group III element oxides. In this case, it is preferable to use a production apparatus provided with at least two second containers.
Because of its relatively low melting point, a Group III element metal easily becomes liquid by heating. When the Group III element metal is liquid, it can be easily supplied into a reaction vessel (second container 301 in
Next, the Group III element metal 110 is heated using first heating units 109a and 109b and the substrate 202 is heated using second heating units 200a and 200b. In this state, oxidizing gas 201a (or 401a) is introduced from oxidizing gas introduction pipe 105, and nitrogen-containing gas 203a and 203b is introduced from the nitrogen-containing gas introduction pipes 107a and 107b. When the apparatus shown in
In the Group III element metal oxidation product gas generation step in the production method of the present invention, from the viewpoint of promoting the generation of the Group III element metal oxidation product gas, preferably, the Group III element metal is caused to react with the oxidizing gas in a heated state. In this case, the temperature of the Group III element oxide is not particularly limited, and is preferably in the range from 650° C. to 1500° C., more preferably in the range from 900° C. to 1300° C., and still more preferably in the range from 1000° C. to 1200° C.
In the Group III element metal oxidation product gas generation step, particularly preferably, the Group III element metal is gallium, the oxidizing gas is H2O gas, and the Group III element metal oxidation product gas is Ga2O. The reaction formula of this case can be represented by the following formula (I), for example. The reaction formula, however, is not limited thereto.
2Ga+H2O→Ga2O+H2 (I)
In the production method of the present invention, from the viewpoint of controlling the partial pressure of the oxidizing gas, the Group III element metal oxidation product gas generation step may be performed in an atmosphere of mixed gas of the oxidizing gas and inert gas. There are no particular limitations on the proportions of the oxidizing gas and the inert gas relative to the total amount of the mixed gas. Preferably, the proportion of the oxidizing gas relative to the total amount of the mixed gas is 0.001 vol. % or more and less than 100 vol. % and the proportion of the inert gas relative to the total amount of the mixed gas is more than 0 vol. % and 99.999 vol. % or less. More preferably, the proportion of the oxidizing gas relative to the total amount of the mixed gas is 0.01 vol. % or more and 80 vol. % or less and the proportion of the inert gas relative to the total amount of the mixed gas is 20 vol. % or more and 99.99 vol. % or less. Still more preferably, the proportion of the oxidizing gas relative to the total amount of the mixed gas is 0.1 vol. % or more and 60 vol. % or less and the proportion of the inert gas relative to the total amount of the mixed gas is 40 vol. % or more and 99.9 vol. % or less. In the production method of the present invention, examples of the inert gas include nitrogen gas, helium gas, argon gas, and krypton gas. Among them, nitrogen gas is particularly preferable. Examples of the method for creating the mixed gas atmosphere include a method of introducing inert gas from an inert gas introduction pipe (not shown) provided in the second container separately from the oxidizing gas introduction pipe; and a method of preliminarily generating gas in which the hydrogen gas and the inert gas are mixed at predetermined proportions and introducing the thus obtained gas from the oxidizing gas introduction pipe. In the case of introducing the inert gas from the separately provided inert gas introduction pipe, the flow rate of the inert gas can be set appropriately according to the flow rate of the oxidizing gas and the like. The flow rate of the inert gas is, for example, in the range from 0.1 to 150 Pa·m3/s, preferably in the range from 0.2 to 30 Pa·m3/s, and more preferably in the range from 0.3 to 10 Pa·m3/s.
The generated Group III element metal oxidation product gas 111a is delivered to the outside of the second container 102 (or 301) through the Group III element metal oxidation product gas delivery pipe 106 (Group III element metal oxidation product gas 111b). Although the Group III element metal oxidation product gas 111b shown in
The generation of the Group III element metal oxidation product gas 111a (111b) may be performed in a condition under pressure, in a condition under reduced pressure, or in conditions other than these conditions, for example. The pressure in the condition under pressure is not particularly limited, and is preferably in the range from 1.0×105 to 1.50×107 Pa, more preferably in the range from 1.05×105 to 5.00×106 Pa, and more preferably in the range from 1.10×105 to 9.90×105 Pa. The method of applying pressure can be, for example, a method of applying pressure by the oxidizing gas, the first carrier gas, or the like. The pressure in the condition under reduced pressure is not particularly limited, and is preferably in the range from 1×101 to 1×105 Pa, more preferably in the range from 1×102 to 9×104 Pa, and still more preferably in the range from 5×103 to 7×104 Pa.
The Group III element metal oxidation product gas (e.g., Ga2O gas) 111b delivered to the outside of the second container 102 (or 301) through the Group III element metal oxidation product gas delivery pipe 106 is caused to react with nitrogen-containing gas 203c introduced into the first container 101, and a Group III nitride (e.g., GaN) crystal 204 is generated on the substrate 202 (Group III nitride crystal generation step). The reaction formula of this case can be represented, for example, by the following formula (II) in the case where the Group III element metal oxidation product gas is Ga2O gas and the nitrogen-containing gas is ammonia gas. The reaction formula, however, is not limited thereto. Note that excess remaining gas after reaction can be exhausted from the exhaust pipe 108 as exhaust gas 203d.
Ga2O+2NH3→2GaN+2H2O+2H2 (II)
In the production method of the present invention, examples of the nitrogen-containing gas include nitrogen gas (N2), ammonia gas (NH3), hydrazine gas (NH2NH2), and alkylamine gas (e.g., C2H8N2). The nitrogen-containing gas is particularly preferably NH3.
The present invention is, as described above, characterized in that the reaction is performed in the presence of a carbon-containing substance in the Group III nitride crystal generation step. The form of the carbon-containing substance is not particularly limited and may be, for example, solid, liquid, or gas at room temperature. In the case where the carbon-containing substance is gas at room temperature, for example, since the reaction can be performed while appropriately adjusting the introduction amount (flow rate) of the carbon-containing substance in the Group III nitride crystal production apparatus, it is easy to control the reaction. The carbon-containing substance is not limited to particular substances, and examples thereof include elementary carbon, a carbon compound, carbon-containing gas, carbon monoxide (CO) gas, and hydrocarbon gas. The elementary carbon may be, for example, solid elementary carbon. The solid elementary carbon is not particularly limited, and examples thereof include graphite, carbon nanotube, and fullerene. The carbon compound can be, for example, a solid carbon compound. As described above, the carbon compound may be in the form of liquid or gas. Examples of the carbon-containing gas include the hydrocarbon gas, an aliphatic oxygen compound, an aromatic oxygen compound, a nitrogen compound, and a sulfur compound. In the case where the carbon-containing substance is hydrocarbon, the hydrocarbon may be, for example, saturated hydrocarbon or unsaturated hydrocarbon, and the examples thereof include chain hydrocarbon (alkane, alkene, alkyne, etc.), alicyclic hydrocarbon, and aromatic hydrocarbon. The chain hydrocarbon may be saturated chain hydrocarbon or unsaturated chain hydrocarbon and may be straight chain hydrocarbon or branched chain hydrocarbon. The number of carbons in the chain hydrocarbon is not particularly limited, and may be, for example, 1 C to 100 C or more. The hydrocarbon is not limited to the chain hydrocarbon, and is preferably in the form of gas at the reaction temperature (for example about 1,200° C. although it is not limited) in the Group III nitride crystal generation step, for example. The boiling point of 100 C straight chain alkane(hectane) is about 721° C. at normal pressure (1 atm). Examples of the chain hydrocarbon include methane, ethane, propane, butane, 2-methylpropane, ethylene, acetylene(ethyne), propylene, 1,3-butadiene, and 1,2-butadiene. The alicyclic hydrocarbon may be saturated hydrocarbon or unsaturated hydrocarbon, may be monoring hydrocarbon or fused ring hydrocarbon, having 3 C to 100 C, for example, and may have or may not have a side chain. Examples of the alicyclic hydrocarbon include cyclopentane, cyclohexane, cycloheptane, methyl cyclohexane, and cyclohexene. The aliphatic oxygen compound or the aromatic oxygen compound is not limited to particular compounds, and examples thereof include alcohol, ether, and ketone, and specific examples thereof include ethyl acetate, diethyl ether, phenol, and diphenyl ether. The nitrogen compound is not limited to particular compounds, and examples thereof include alkyl amines and aniline. The sulfur compound is not limited to particular compounds, and can be, for example, sulfoxide, and can specifically be, for example, dimethylsulfoxide (DMSO) and the like.
In the present invention, a Group III nitride crystal of high quality with few defects can be produced by performing the reaction in the presence of a carbon-containing substance in the Group III nitride crystal generation step. The reason (mechanism) therefor can be assumed, for example, as follows although it is unknown. That is, it is assumed that, when oxide (e.g., H2O gas) contained in the Group III element-containing gas as impurity is reduced by the carbon-containing substance and removed, the impurity in the Group III nitride crystal to be generated is reduced and the defects such as a dislocation, a crack, and the like in a crystal are reduced. The binding energy of C—O single bond is 1076 kJ/mol and the binding energy of H—O single bond of a H2O molecule is 497 kJ/mol, which means that the C—O single bond is more stable. Thus, commonly, it is assumed that the carbon-containing substance is a substance having higher reducing power than H2O. These assumptions, however, do not limit the present invention by any means.
The usage of the carbon-containing substance is not limited to particular usages. For example, carbon-containing gas (methane gas, etc.) may be used as the carbon-containing substance and the carbon-containing gas may be introduced after being mixed with the nitrogen-containing gas 203a and 203b (or 203f). In addition to or instead of this, for example, as shown in
In the Group III nitride crystal generation step, the temperature of the substrate (i.e., crystal growth temperature) is not particularly limited. From the viewpoint of ensuring the generation rate of crystal and improving crystallinity, the temperature is preferably in the range from 700° C. to 1500° C., more preferably in the range from 1000° C. to 1400° C., and still more preferably in the range from 1100° C. to 1350° C. As described above, preferably, the method for producing a Group III nitride crystal includes an early stage crystal growth step and a late stage crystal growth step and the crystal growth temperature in the late stage crystal growth step is higher than the crystal growth temperature in the early stage crystal growth step. In this case, the crystal growth temperature in the early stage crystal growth step is, for example, in the range from 700° C. to 1400° C., preferably in the range from 900° C. to 1300° C., and more preferably in the range from 000° C. to 1200° C. The crystal growth temperature in the late stage crystal growth step is, for example, in the range from 1000° C. to 1500° C., preferably in the range from 1100° C. to 1400° C., and more preferably in the range from 1200° C. to 1350° C. Moreover, the crystal growth temperature in the early stage crystal growth step is preferably equal to or higher than the crystal growth temperature in the substrate production step.
The Group III nitride crystal generation step may be performed in a condition under pressure, in a condition under reduced pressure, or in conditions other than these conditions. The pressure in the condition under pressure is not particularly limited, and is preferably in the range from 1.01×105 to 1.50×107 Pa, more preferably in the range from 1.05×105 to 5.00×106 Pa, and still more preferably in the range from 1.10×105 to 9.90×105 Pa. The pressure in the condition under reduced pressure is not particularly limited, and is preferably in the range from 1×101 to 1×105 Pa, more preferably in the range from 1×102 to 9×104 Pa, and still more preferably in the range from 5×103 to 7×104 Pa.
In the Group III nitride crystal generation step, the supply amount of the Group III element metal oxidation product gas (e.g., Ga2O gas indicated by 111b in
The flow rate of the nitrogen-containing gas can be set appropriately according to the conditions such as the temperature of the substrate and the like. The flow rate of the nitrogen-containing gas is, for example, in the range from 0.1 to 150 Pa·m3/s, preferably in the range from 0.3 to 60 Pa·m3/s, and more preferably in the range from 0.5 to 30 Pa·m3/s.
For transferring the introduced nitrogen-containing gas to a crystal generation region (in the vicinity of the substrate support 103 in the first container 101 in
In the case of introducing the second carrier gas from the carrier gas introduction pipe, the flow rate of the second carrier gas can be set appropriately according to the flow rate of the nitrogen-containing gas and the like. The flow rate of the second carrier gas is, for example, in the range from 0.1 to 150 Pa·m3/s, preferably in the range from 0.8 to 60 Pa·m3/s, and more preferably in the range from 1.5 to 30 Pa·m3/s.
The mixing ratio A:B (volume ratio) between the nitrogen-containing gas (A) and the second carrier gas (B) is not particularly limited, and is preferably in the range from 2 to 80:98 to 20, more preferably in the range from 5 to 60:95 to 40, and still more preferably in the range from 10 to 40:90 to 60. The mixing ratio A:B (volume ratio) can be set, for example, by preliminarily mixing the nitrogen-containing gas and the second carrier gas at a predetermined mixing ratio or adjusting the flow rate (partial pressure) of the nitrogen-containing gas and the flow rate (partial pressure) of the second carrier gas.
Preferably, the Group III nitride crystal (e.g., GaN crystal) generation step is performed in a condition under pressure. The pressure in the condition under pressure is as described above. The method of applying pressure can be, for example, a method of applying pressure by the nitrogen-containing gas, the second carrier gas, or the like.
The Group III nitride crystal generation step may be performed in a dopant-containing gas atmosphere. This allows a dopant-containing GaN crystal to be generated. Examples of the dopant include Si, S, Se, Te, Ge, Fe, Mg, and Zn. One type of the dopants may be used alone or two or more of them may be used in combination. Examples of the dopant-containing gas include monosilane (SiH4), disilane (Si2H6), triethylsilane (SiH(C2H5)3), tetraethylsilane Si(C2H5)4), H2S, H2Se, H2Te, GeH4, Ge2O, SiO, MgO, and ZnO, and one of them may be used alone or two or more of them may be used in combination.
For example, the dopant-containing gas may be introduced from a dopant-containing gas introduction pipe (not shown) provided separately from the nitrogen-containing gas introduction pipe or introduced from the nitrogen-containing gas introduction pipe after being mixed with the nitrogen-containing gas. In the case of introducing the second carrier gas, the dopant-containing gas may be introduced after being mixed with the second carrier gas.
The concentration of the dopant in the dopant-containing gas is not particularly limited, and is, for example, in the range from 0.001 to 100000 ppm, preferably in the range from 0.01 to 1000 ppm, and more preferably in the range from 0.1 to 10 ppm.
The generation rate of the Group III nitride crystal (e.g., GaN crystal) is not particularly limited. The rate is, for example, 100 μm/h or more, preferably 500 μm/h or more, and more preferably 1000 μm/h or more.
The Group III nitride crystal production method (A) can be performed as described above. However, the Group III nitride crystal production method (A) is not limited thereto. For example, as described above, in the Group III nitride crystal production method (A), preferably, a reaction is performed also in the presence of reducing gas in a reaction system. Furthermore, as described above, preferably, at least one of the oxidizing gas and the nitrogen-containing gas is mixed with the reducing gas. That is, in
Furthermore, in the Group III nitride crystal production method (A), when the reaction is performed in the presence of the reducing gas in a reaction system, for example, a larger Group III nitride crystal can be produced. For example, by growing a Group III nitride crystal on a seed crystal and then slicing the Group III nitride crystal, a plate-like semiconductor wafer formed of a Group III nitride crystal is produced. However, the Group III nitride crystal tends to have a tapered pyramid shape as it grows, and thus only a small semiconductor wafer is obtained at the tip of the pyramid-shaped crystal. It is to be noted that, in the production method of the present invention, when the reaction is performed in the presence of the reducing gas in a reaction system, a columnar (i.e., not tapered) crystal instead of a pyramid-shaped crystal tends to be obtained although the reason is unknown. Different from a pyramid-shaped crystal, when such a columnar Group III nitride crystal is sliced, semiconductor wafers (Group III nitride crystals) each having a large diameter can be obtained in most parts.
In the Group III nitride crystal production method (A), examples of the reducing gas include hydrogen gas; carbon monoxide gas; hydrocarbon gas such as methane gas, ethane gas, or the like; hydrogen sulfide gas; and sulfur dioxide gas, and one of them may be used alone or two or more of them may be used in combination. Among them, hydrogen gas is particularly preferable. The hydrogen gas with high purity is preferable. The purity of the hydrogen gas is particularly preferably 99.9999% or more.
When the Group III element metal oxidation product gas generation step is performed in the presence of the reducing gas, the reaction temperature is not particularly limited. From the viewpoint of inhibiting generation of a by-product, the reaction temperature is preferably 900° C. or higher, more preferably 1000° C. or higher, and still more preferably 1100° C. or higher. The upper limit of the reaction temperature is not particularly limited, and is, for example, 1500° C. or lower.
When the reducing gas is used in the Group III nitride crystal production method (A), the amount of the reducing gas to be used is not particularly limited. The amount of the reducing gas relative to the total volume of the oxidizing gas and the reducing gas is, for example, in the range from 1 to 99 vol. %, preferably in the range from 3 to 80 vol. %, and more preferably in the range from 5 to 70 vol. %. The flow rate of the reducing gas can be set appropriately according to the flow rate of the oxidizing gas or the like. The flow rate of the reducing gas is, for example, in the range from 0.01 to 100 Pa·m3/s, preferably in the range from 0.05 to 50 Pa·m3/s, and more preferably in the range from 0.1 to 10 Pa·m3/s. Furthermore, as described above, generation of Group III element metal oxidation product gas 111a (111b) is preferably performed in a condition under pressure. The pressure is, for example, as described above. The method of applying pressure may be, for example, a method of applying pressure by the oxidizing gas and the reducing gas.
The Group III nitride crystal production method (A) of the present invention is vapor phase epitaxy and can be performed without using halide as a material. When halide is not used, different from the halide vapour phase epitaxy described in S52(1977)-023600 A (Patent Document 1) and the like, a Group III nitride crystal can be produced without generating a halogen-containing by-product. This makes it possible to prevent crystal generation from being adversely affected due to clogging of the exhaust pipe of the production apparatus with a halogen-containing by-product (e.g., NH4Cl), for example.
Next, production steps, reaction conditions, and the like in the Group III nitride crystal production method (B) are described with reference to an illustrative example.
The Group III nitride crystal production method (B) can be performed using the production apparatus 100 shown in
The Group III nitride crystal production method (B) is described specifically below using
First, Ga2O3 is placed on the Group III element oxide placement part 104, and a substrate 202 is set on the substrate support 103. Next, the Ga2O3 is heated using the first heating units 109a and 109b, and the substrate 202 is heated using the first heating units 200a and 200b. In this state, hydrogen gas 201a is introduced from the reducing gas introduction pipe 105, and ammonia gas 203a and 203b is introduced from the nitrogen-containing gas introduction pipes 107a and 107b. The introduced hydrogen gas 201b reacts with the Ga2O3, thereby generating Ga2O gas (the following formula (III)). The thus-generated Ga2O gas 111a is delivered to the outside of the second container 102 as Ga2O gas 111b through the reduced product gas delivery pipe 106. The delivered Ga2O gas 111b reacts with the introduced ammonia gas 203c, thereby generating a GaN crystal 204 on the substrate 202 (the following formula (IV)).
Ga2O3+2H2→Ga2O+2H2O (III)
Ga2O+2NH3→2GaN+2H2O+2H2 (IV)
The present invention is, as described above, characterized in that the reaction is performed in the presence of a carbon-containing substance in the Group III nitride crystal generation step. In the Group III nitride crystal production method (B), the usage of the carbon-containing substance is not limited to particular usages and can be, for example, the same as in the Group III nitride crystal production method (A). That is, for example, carbon-containing gas (methane gas, etc.) may be used as the carbon-containing substance and the carbon-containing gas may be introduced after being mixed with the nitrogen-containing gas 203a and 203b (or 203g). In addition to or instead of this, for example, as shown in
As can be seen from the formulae (III) and (IV), by-products generated in the Group III nitride crystal production method (B) are only water and hydrogen. That is, no solid by-product is generated. The water and the hydrogen can be exhausted from the exhaust pipe 108 in the state of gas or liquid, for example. As a result, for example, a GaN crystal can be grown for a long period, whereby a large and thick GaN crystal can be obtained. Moreover, for example, it is not necessary to provide a filter or the like for removing by-products, which is advantageous in terms of cost. It is to be noted, however, that the Group III nitride crystal production method (B) is not limited by the above description.
Preferably, the Ga2O3 is in the form of a powder or a granule. When the Ga2O3 is in the form of a powder or a granule, the Ga2O3 has a large surface area, which promotes the generation of Ga2O gas.
For generating a ternary or higher nitride crystal, it is preferable to generate reduced product gas of at least two kinds of Group III element oxides. In this case, it is preferable to use a production apparatus provided with at least two second containers.
The hydrogen gas with high purity is preferable. The purity of the hydrogen gas is preferably 99.9999% or more. The flow rate (partial pressure) of the hydrogen gas can be set as appropriate according to the conditions such as the temperature of the Ga2O3 and the like. The partial pressure of the hydrogen gas is, for example, in the range from 0.2 to 2000 kPa, preferably in the range from 0.5 to 1000 kPa, and more preferably in the range from 1.5 to 500 kPa.
As described above, from the viewpoint of controlling the partial pressure of the hydrogen gas, preferably, the generation of Ga2O gas is performed in an atmosphere of mixed gas of the hydrogen gas and inert gas. Examples of the method for creating the mixed gas atmosphere include a method of introducing inert gas from an inert gas introduction pipe (not shown) provided in the second container separately from the reducing gas introduction pipe; and a method of preliminarily generating gas in which the hydrogen gas and the inert gas are mixed at predetermined proportions and introducing the thus obtained gas from the reducing gas introduction pipe. In the case of introducing the inert gas from the separately provided inert gas introduction pipe, the flow rate (partial pressure) of the inert gas can be set as appropriate according to the flow rate of the hydrogen gas and the like. The partial pressure of the inert gas is, for example, in the range from 0.2 to 2000 kPa, preferably in the range from 2.0 to 1000 kPa, and more preferably in the range from 5.0 to 500 kPa.
The proportion of the hydrogen gas and the proportion of the inert gas in the mixed gas are as described above. The proportion of the hydrogen gas and the proportion of the inert gas in the mixed gas can be set, for example, by preliminarily generating the mixed gas in which the hydrogen gas and the inert gas are mixed at predetermined proportions or by adjusting the flow rate (partial pressure) of the hydrogen gas and the flow rate (partial pressure) of the inert gas.
For delivering the Ga2O gas to the outside of the second container through the reduced product gas delivery pipe, first carrier gas may be introduced. As the first carrier gas, for example, the examples described for the inert gas can be used. The flow rate (partial pressure) of the first carrier gas can be the same as that of the inert gas. In the case of introducing the inert gas, the inert gas can be used as the first carrier gas.
Preferably, the generation of Ga2O gas is performed under pressure. The pressure in the condition under pressure is not particularly limited, and is preferably in the range from 1.01×105 to 1.50×107 Pa, more preferably in the range from 1.05×105 to 5.00×106 Pa, and still more preferably in the range from 1.10×105 to 9.90×105 Pa. The method of applying pressure can be, for example, a method of applying pressure by the hydrogen gas, the first carrier gas, or the like.
When reduced product gas of at least two kinds of Group III element oxides is generated as described above, a ternary or higher nitride crystal is generated on a substrate, for example. The ternary or higher nitride crystal can be, for example, a crystal represented by GaxIn1-xN (0<x<1).
The supply amount of the Ga2O gas is, for example, in the range from 5×10−5 to 1×10−1 mol/h, preferably in the range from 1×10−4 to 1×10−2 mol/h, and more preferably in the range from 2×10−4 to 5×10−4 mol/h. The supply amount of the Ga2O gas can be adjusted, for example, by adjusting the flow rate (partial pressure) of the first carrier gas in generation of the Ga2O gas.
The flow rate (partial pressure) of the ammonia gas can be set as appropriate according to the conditions such as the temperature of the substrate and the like. The partial pressure of the ammonia gas is, for example, in the range from 0.2 to 3000 kPa, preferably in the range from 0.5 to 2000 kPa, and more preferably in the range from 1.5 to 1000 kPa.
For transferring the introduced ammonia gas to a crystal generation region, second carrier gas may be introduced. For example, the second carrier gas may be introduced from a carrier gas introduction pipe (not shown) provided separately from the nitrogen-containing gas introduction pipe or introduced from the nitrogen-containing gas introduction pipe after being mixed with the ammonia gas. As the second carrier gas, for example, the examples described for the first carrier gas can be used.
In the case of introducing the second carrier gas from the carrier gas introduction pipe, the flow rate (partial pressure) of the second carrier gas can be set as appropriate according to the flow rate (partial pressure) of the nitrogen-containing gas and the like. The partial pressure of the second carrier gas is, for example, in the range from 0.2 to 3000 kPa, preferably in the range from 0.5 to 2000 kPa, and more preferably in the range from 1.5 to 1000 kPa.
The mixing ratio A:B (volume ratio) between the ammonia gas (A) and the second carrier gas (B) is not particularly limited, and is preferably in the range from 3 to 80:97 to 20, more preferably in the range from 8 to 60:92 to 40, and still more preferably in the range from 10 to 40:90 to 60. The mixing ratio A:B (volume ratio) can be set, for example, by preliminarily mixing the ammonia gas and the second carrier gas at a predetermined mixing ratio or adjusting the flow rate (partial pressure) of the ammonia gas and the flow rate (partial pressure) of the second carrier gas.
Preferably, the GaN crystal generation is performed in a condition under pressure. The pressure in the condition under pressure is as described above. The method of applying pressure can be, for example, a method of applying pressure by the ammonia gas, the second carrier gas, or the like.
The generation of a GaN crystal may be performed in a dopant-containing gas atmosphere. This allows a dopant-containing GaN crystal to be generated. Examples of the dopant include Si, S, Se, Te, Ge, Fe, Mg, and Zn. One type of the dopants may be used alone or two or more of them may be used in combination. Examples of the dopant-containing gas include monosilane (SiH4), disilane (Si2H6), triethylsilane (SiH(C2H5)3), tetraethylsilane Si(C2H5)4), H2S, H2Se, H2Te, GeH4, Ge2O, SiO, MgO, and ZnO, and one of them may be used alone or two or more of them may be used in combination.
For example, the dopant-containing gas may be introduced from a dopant-containing gas introduction pipe (not shown) provided separately from the nitrogen-containing gas introduction pipe or introduced from the nitrogen-containing gas introduction pipe after being mixed with the ammonia gas. In the case of introducing the second carrier gas, the dopant-containing gas may be introduced after being mixed with the second carrier gas.
The concentration of the dopant in the dopant-containing gas is not particularly limited, and is, for example, in the range from 0.001 to 100000 ppm, preferably in the range from 0.01 to 1000 ppm, and more preferably in the range from 0.1 to 10 ppm.
The generation rate of the GaN crystal is not particularly limited. The rate is, for example, 100 μm/h or more, preferably 500 μm/h or more, and more preferably 1000 μm/h or more.
Also in the case of using any Group III element oxide other than Ga2O3, the production method of the present invention can generate a Group III nitride crystal in the same manner as in the case of using Ga2O3.
The Group III element oxide other than the Ga2O3 may be as follows: when the Group III element is In, the Group III element oxide can be, for example, In2O3; when the Group III element is Al, the Group III element oxide can be, for example, Al2O3; when the Group III element is B, the Group III element oxide can be, for example, B2O3; and when the Group III element is Tl, the Group III element oxide can be, for example, Tl2O3. One of the Group III element oxides other than the Ga2O3 may be used alone, or two or more of them may be used in combination.
There is no particular limitation on the size of the Group III nitride crystal produced by the method for producing a Group III nitride crystal. Preferably, the major axis is 15 cm (about 6 inch) or more, more preferably, the major axis is 20 cm (about 8 inch) or more, and particularly preferably, the major axis is 25 cm (about 10 inch) or more, for example. There is no particular limitation on the height of the Group III nitride crystal. The height is, for example, 1 cm or more, preferably 5 cm or more, and more preferably 10 cm or more. The production method according to the present invention however is not limited to the production of such a large Group III nitride crystal. For example, the production method according to the present invention can be used for producing a Group III nitride crystal of higher quality having a conventional size. Furthermore, for example, as described above, the height (thickness) of the Group III nitride crystal is not particularly limited.
In the Group III nitride crystal, the dislocation density is not particularly limited and is preferably 1.0×107 cm−2 or less, more preferably 1.0×104 m−2 or less, still more preferably 1.0×103 cm−2 or less, and still more preferably 1.0×102 cm−2 or less. Although the dislocation density is ideally 0, it is normally impossible for the dislocation density to be 0. Thus, for example, the dislocation density is a value more than 0 and is particularly preferably not more than a measurement limit of a measurement instrument. The dislocation density may be, for example, an average value of the entire crystal, and, more preferably, the maximum value in the crystal is not more the above-described value. In the Group III nitride crystal of the present invention, the half width of each of a symmetric reflection component (002) and an asymmetric reflection component (102) by XRC is, for example, 300 seconds or less, preferably 100 seconds or less, more preferably 30 seconds or less, and ideally 0.
For example, the Group III nitride crystal production method of the present invention may further include a crystal re-growth step of further growing the produced Group III nitride crystal. Specifically, for example, in the crystal re-growth step, the produced Group III nitride crystal may be cut so that any plane (for example, c-, m-, or a-plane or another nonpolar plane) is exposed, and the Group III nitride crystal may be further grown using the plane as a crystal growth plane. Thus, a Group III nitride crystal having a large area of any plane and a large thickness can be produced.
The Group III nitride crystal of the present invention is a Group III nitride crystal produced by the production method of the present invention or a Group III nitride crystal produced by further growing the Group III nitride crystal. The Group III nitride crystal of the present invention is, for example, a large Group III nitride crystal of high quality with few defects. Although the quality is not particularly limited, for example, the dislocation density is preferably in the above-described numerical range. The size of the Group III nitride crystal also is not particularly limited and is, for example, as mentioned above. The use of the Group III nitride crystal of the present invention also is not particularly limited and can be used in a semiconductor apparatus since it has properties of a semiconductor, for example. In the present invention, the Group III nitride crystal is not limited to particular crystals and is a Group III nitride crystal represented by AlxGayIn1-x-yN (0≦x≦1, 0≦y≦1, x+y≦1), and examples thereof include AlGaN, InGaN, InAlGaN. Among them, GaN is particularly preferable. The Group III element is, for example, at least one selected from the group consisting of gallium (Ga), indium (In), and aluminum (Al). Among them, Ga is particularly preferable.
According to the present invention, as mentioned above, a Group III nitride (e.g., GaN) crystal with a diameter of 6 inches or more, which has not been produced by a conventional technique, can be provided. Accordingly, for example, by using Group III nitride as a substitute for Si in a semiconductor apparatus such as a power device, a high frequency device, or the like generally required to have a large diameter of Si (silicon), the performance can further be improved. Therefore, the present invention has a great impact on the semiconductor industry. The application of the Group III nitride crystal of the present invention is not limited thereto and is applicable to any other semiconductor apparatuses such as solar battery and the like and any other applications besides the semiconductor apparatuses.
The semiconductor apparatus of the present invention is not limited to particular apparatuses, and the semiconductor apparatus can be any article as long as it is operated by using a semiconductor. Examples of the article operated by a semiconductor include semiconductor devices and electrical equipment using the semiconductor device. Examples of the semiconductor device include diodes, high frequency devices such as transistors, power devices, and light emitting devices such as light-emitting diodes (LEDs) and laser diodes (LDs). Examples of the electrical equipment using the semiconductor device include a cellular phone base station equipped with the high frequency device; control equipment for solar cell and power supply control equipment of a vehicle driven by electricity each equipped with the power device; and a display, lighting equipment, and an optical disk device each equipped with the light emitting device. For example, a laser diode (LD) that emits blue light is applied to a high density optical disk, a display, and the like, and a light-emitting diode (LED) that emits blue light is applied to a display, a lighting, and the like. An ultraviolet LD is expected to be applied in biotechnology and the like and an ultraviolet LED is expected as an ultraviolet source which is an alternate for a mercury lamp. Also, an inverter that uses the Group III-V compound of the present invention as a power semiconductor for inverter can be used for power generation in a solar cell, for example. As described above, the Group III nitride crystal of the present invention is not limited thereto, and can be applied to any other semiconductor apparatuses or various technical fields besides the semiconductor apparatuses.
The examples of the present invention are described below. The present invention, however, is not limited by the following examples.
In the Examples below, the XRC half width was measured using a SmartLab (product name) produced by Rigaku Corporation. The dislocation density was measured according to the evaluation of the etch pit density generated by KOH+NaOH melt etching.
In the present Example, a GaN crystal was generated by vapor phase epitaxy by using solid carbon (graphite) as a carbon-containing substance (Group III nitride crystal growth step), and was further grown, thereby producing an intended GaN crystal.
First, as a GaN seed crystal, 2-inch free-standing substrate produced by FKK Corporation was prepared. Next, on the GaN seed crystal (GaN crystal layer substrate), a GaN crystal was produced by vapor phase epitaxy (homoepi) using the apparatus shown in
The vapor phase epitaxy was performed as follows. In the present Example, powdery gallium oxide (III) (Ga2O3) was used as a Group III element-containing material 110 and hydrogen gas (H2) was used as reduced product gas 201a. The partial pressure of the hydrogen gas (H2) was 3.3 kPa. In this state, the hydrogen gas 201a (201b) was caused to react with gallium oxide (III) 110 to generate gallium oxide (I) (Ga2O) gas 111a (111b). In the present Example, the generation amount of Ga2O (gallium oxide (I)) was calculated based on the mass change (decrease amount) of Ga2O3 before and after the reaction with the conversion efficiency from H2 and Ga2O3 to Ga2O being estimated as 100%. According to this calculation, the partial pressure of the gallium oxide (I) gas 111a (111b) was estimated as 2×10−2 kPa. Furthermore, ammonia gas (NH3) was used as nitrogen-containing gas 203a and 203b. The partial pressure of the ammonia gas was 67 kPa. Moreover, N2 gas (100% N2 gas, containing no other gas) as carrier gas was introduced from the oxidizing gas introduction pipe 105 and nitrogen-containing gas introduction pipes 107a and 107b and pressure was applied so that the total pressure becomes 100 kPa. Prior to the feeding of each gas, as shown in
In this production method, GaN crystals were produced with different amounts of solid carbon. As a Comparative Example, a GaN crystal was produced in the same manner as in the present Example except that the solid carbon was not provided. The SEM image of each GaN crystal produced (grown) in this manner was obtained, and the film thickness, XRC half width, crack density, and dislocation density of each GaN crystal were measured. The results are shown in
First, as shown in (a) of
As shown in
In the present Example, methane gas (CH4) was used as a carbon-containing substance. Specifically, a GaN crystal was produced in the same manner as in Example 1 except that the apparatus shown in
feeding of gas was started during the temperature rising, the temperature rising time was 30 minutes, and the GaN crystal growth time was 60 minutes.
gas flow rate (during temperature rising)
201a:H2 0 sccm+N2 200 sccm
203e:N2 200 sccm
203f:NH3 2000 sccm+CH4
203g:N2 200 sccm
gas flow rate (during GaN crystal growth)
201a:H2 100 sccm+N2 400 sccm
203e:N2 3000 sccm
203f:NH3 2000 sccm+CH4
203g:N2 2000 sccm
In this production method, GaN crystals were produced at different flow rates of methane (methane gas) CH4 mixed with nitrogen-containing gas (ammonia gas) 203f. As a Comparative Example, a GaN crystal was produced in the same manner as in the present Example except that the methane gas was not used. The SEM image of each GaN crystal produced (grown) in this manner was obtained, and the film thickness, XRC half width, crack rate, and dislocation density of each GaN crystal were measured. The results are shown in
As shown in
In the present Example, a GaN crystal was produced with the apparatus shown in
gas flow rate (during GaN crystal growth)
201a:H2 100 sccm+N2 400 sccm+H2O 1.84 sccm
203e:N2 3000 sccm
203f:NH3 2000 sccm+CH4
203g:N2 2000 sccm
In the present Example, a GaN crystal was produced as described below. First, as a GaN seed crystal, 2-inch free-standing substrate produced by FKK Corporation was prepared as in Examples 1 and 2.
Next, as shown in
As a Comparative Example, a GaN crystal was produced in the same manner as in the present Example except that the methane gas was not used.
The SEM images of the GaN crystals of the present Example and the SEM image of the GaN crystal of Comparative Example in which methane gas was not used were obtained. The film thickness, XRC half width, crack density, and dislocation density of each GaN crystal were measured. The results are shown in
As described above, according to the present invention, a Group III nitride crystal of high quality with few defects can be produced by vapor phase epitaxy. According to the production method of the present invention, for example, a large Group III nitride crystal of high quality with few defects such as a distortion, dislocation, warping, and the like can be produced. Furthermore, for example, the present invention provides the semiconductor apparatus of the present invention that uses the Group III nitride crystal and the Group III nitride crystal production apparatus that can be used in the production method according to the present invention. For example, by using the Group III nitride crystal produced by the present invention as a substitute for Si in a semiconductor apparatus such as a power device, a high frequency device, or the like generally required to have a large diameter of Si (silicon), the performance can further be improved. The present invention, however, is not limited thereto and is applicable to any other semiconductor apparatuses and other applications besides the semiconductor apparatuses.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-196509 | Oct 2016 | JP | national |
