PRODUCTION METHOD FOR β-Ga2O3 / β-Ga2O3 LAMINATE, LAMINATE OBTAINED VIA SAID PRODUCTION METHOD, AND SEMICONDUCTOR DEVICE COMPRISING SAID LAMINATE

Abstract

The present invention makes it possible to provide a production method for a β-Ga2O3 / β-Ga2O3 laminate that has, on a β-Ga2O3 substrate, a layer which includes a β-Ga2O3 single crystal, said method comprising a step for using a gallium oxide melt which contains a tetravalent differing element and a divalent differing element to form, on a β-Ga2O3 substrate, a layer which includes a β-Ga2O3 single crystal via a liquid phase epitaxial growth method, wherein: the difference in concentration between the tetravalent differing element and the divalent differing element in the obtained layer which includes the β-Ga2O3 single crystal is -1×1019 to +1×1019 atoms / cm3; and the total content of the differing elements in the obtained layer which includes the β-Ga2O3 single crystal is less than 0.01 mol%.

Description

Method for manufacturing β-Ga2O3 / β-Ga2O3 laminate, laminate obtained by the manufacturing method, and semiconductor device including the laminate

[0001] The present invention is ２ O ３ / β-Ga ２ O ３ The present invention relates to a method for manufacturing a laminate, a laminate obtained by the manufacturing method, and a semiconductor device including the laminate.

[0002] Conventionally, Ga ２ O ３ As a method for doping a GaAs single crystal, there are methods for doping a different element simultaneously with crystal growth by HVPE (Hydride Vapor Phase Epitaxy), MBE (Molecular Beam Epitaxy), or EFG (Edge-defined Film-fed Growth). ２ O ３ A method of adding a different element by ion implantation after growing a Ga-based single crystal is known. The applicant of the present application has shown in Patent Document 1 that by using the LPE (Liquid Phase Epitaxy) method, a film with good crystallinity can be obtained even when the different element is contained in a relatively high concentration range of 0.01 mol % to 20 mol %. ２ O ３ Schottky barrier diodes and field-effect transistors made of compound semiconductors are known, but the carrier concentration of the epitaxial layer is １３ ~6.0 x 10 １７ atoms / cm ３ In particular, it has been found that lowering the carrier concentration improves the breakdown voltage of the device (Patent Document 2).

[0003] Patent No. 7380948 Patent No. 6758569

[0004] When attempting to fabricate an epitaxial layer for such a high-voltage device by the LPE method, the method of Patent Document 1 had the problem that the carrier concentration was too high or the amount of heterogeneous elements was too large, making it difficult to control. Also, the prior art HVPE method had the problem that Cl was mixed into the epitaxial layer because a halide compound was used as a raw material. Cl is a β-Ga ２ O ３ Because chloride ions act as dopants in single-crystal films, they generate carriers even when no other elements are intentionally added. Furthermore, chloride ions are prone to corroding electrodes and wiring, so it is undesirable for materials used in semiconductors to contain Cl.

[0005] The present invention aims to solve at least one of the above-mentioned problems in the prior art. ２ O ３ β-Ga with reduced content of foreign elements in layer containing single crystal ２ O ３ / β-Ga ２ O ３ Another object of the present invention is to provide a method for manufacturing a laminate. ２ O ３ β-Ga with reduced Cl content in the layer containing the single crystal ２ O ３ / β-Ga ２ O ３ In this specification, the term "different element" refers to an element other than Ga and O. In addition, in this specification, the term "β-Ga ２ O ３ / β-Ga ２ O ３ The laminate is a β-Ga ２ O ３ On a substrate containing β-Ga ２ O ３ It means a stack of layers containing single crystals.

[0006] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following invention. That is, the present invention is as follows. <1> β-Ga２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing a single crystal ２ O ３ / β-Ga ２ O ３ A method for producing a laminate, comprising: using a gallium oxide melt containing a tetravalent heteroelement and a divalent heteroelement, ２ O ３ The β-Ga was grown on the substrate by liquid phase epitaxial growth. ２ O ３ forming a layer containing a single crystal, ２ O ３ The concentration difference between the tetravalent heteroelement and the divalent heteroelement in the layer containing the single crystal is −1×10 １９ ~ +1 x 10 １９ atoms / cm ３ and the obtained β-Ga ２ O ３ <2> The above-mentioned manufacturing method, wherein the total content of different elements in the layer containing the single crystal is less than 0.01 mol %. ２ O ３ The carrier concentration in the layer containing the single crystal is 1×10 １３ ~1 x 10 １８ atoms / cm ３ The manufacturing method according to the above <1>, wherein the tetravalent heteroelement is one or more selected from the group consisting of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge, and C, and the divalent heteroelement is one or more selected from the group consisting of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn, and Fe. <4> The manufacturing method according to the above <3>, wherein the tetravalent heteroelement is Sn, Si, and C, and the divalent heteroelement is Mg, Ca, and Fe. <5> The manufacturing method according to the above <3>, wherein the tetravalent heteroelement is Sn, Si, and C, and the divalent heteroelement is Mg. <6> The gallium oxide melt is ２ O ３ and SnO ２ , SiO ２<7> The manufacturing method according to any one of the above items <1> to <5>, wherein the gallium oxide melt contains one or more selected from the group consisting of Ga ２ O ３ and PbO, Bi ２ O ３ , SnO ２ , SiO ２ <8> The method according to any one of the above items <1> to <6>, wherein the β-Ga alloy is produced by the method according to any one of the above items <1> to <7>, and the β-Ga alloy is produced by the method according to any one of the above items <1> to <7>. ２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing a single crystal ２ O ３ / β-Ga ２ O ３ It is a laminate. <9> β-Ga ２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing a single crystal ２ O ３ / β-Ga ２ O ３ A laminate comprising: ２ O ３ The layer containing the single crystal contains a tetravalent heteroelement and a divalent heteroelement, and the concentration difference between the tetravalent heteroelement and the divalent heteroelement is −1×10 １９ ~ +1 x 10 １９ atoms / cm ３ and the β-Ga ２ O ３ the total content of different elements in the layer containing the single crystal is less than 0.01 mol %, ２ O ３ The Cl concentration in the layer containing the single crystal is 1×10 １６ atoms / cm ３ or the β-Ga ２ O ３ The layer containing the single crystal does not contain Cl. ２ O ３ / β-Ga ２ O ３<10> The β-Ga ２ O ３ The carrier concentration in the layer containing the single crystal is 1×10 １３ ~1 x 10 １８ atoms / cm ３ The β-Ga according to the above item <9>, ２ O ３ / β-Ga ２ O ３ <11> The β-Ga alloy according to <9> or <10> above, wherein the tetravalent heteroelement is at least one selected from the group consisting of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge, and C, and the divalent heteroelement is at least one selected from the group consisting of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn, and Fe. ２ O ３ / β-Ga ２ O ３ <12> The β-Ga alloy according to <11>, wherein the tetravalent heteroelement is Sn, Si, and C, and the divalent heteroelement is Mg. ２ O ３ / β-Ga ２ O ３ <13> The β-Ga alloy according to any one of <8> to <12> above, ２ O ３ / β-Ga ２ O ３ a laminate; and the β-Ga ２ O ３ a Schottky electrode provided on a surface of the layer containing the single crystal; ２ O ３ The β-Ga on the substrate ２ O ３ <14> A semiconductor device comprising the β-Ga GaN layer according to any one of <8> to <12> above, and an ohmic electrode provided on the surface opposite to the layer containing the single crystal. ２ O ３ / β-Ga ２ O ３ a laminate; and the β-Ga ２ O ３a source electrode and a drain electrode provided directly on a surface of the layer containing the single crystal or via a contact region; and ２ O ３ <15> A semiconductor device comprising the β-Ga single crystal according to any one of <8> to <12> above, and a gate electrode formed on the single crystal directly or via a gate insulating film. ２ O ３ / β-Ga ２ O ３ a laminate; and the β-Ga ２ O ３ a source electrode provided directly on the surface of the layer containing the single crystal or via a contact region; ２ O ３ a gate electrode embedded directly on a surface of the layer containing the single crystal or via a gate insulating film, or embedded directly in a trench formed on the surface or via a gate insulating film; ２ O ３ The β-Ga on the substrate ２ O ３ and a drain electrode provided on the surface opposite to the layer containing the single crystal.

[0007] According to one embodiment of the present invention, the β-Ga obtained using the LPE method ２ O ３ β-Ga with reduced content of foreign elements in layer containing single crystal ２ O ３ / β-Ga ２ O ３ According to another embodiment of the present invention, a method for manufacturing a laminate can be provided. ２ O ３ β-Ga with reduced Cl content in the layer containing the single crystal ２ O ３ / β-Ga ２ O ３ A laminate can be provided.

[0008] Fig. 1 is a graph showing the measurement results of secondary ion mass spectrometry (SIMS) for the stack obtained in Example 1. Fig. 2 is a schematic diagram showing an example of a general LPE growth furnace. Fig. 3 is a schematic diagram showing an example of a semiconductor device according to an embodiment of the present invention. Fig. 4 is a schematic diagram showing an example of a semiconductor device according to an embodiment of the present invention. Fig. 5 is a graph showing the current (I)-voltage (V) characteristics of the Schottky barrier diode obtained in Example.

[0009] The present invention will be described in detail below. Note that the present invention is not limited to the following embodiments, and can be implemented by making any modifications within the scope of the effects of the invention.

[0010] The first embodiment of the present invention is a β-Ga ２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing a single crystal ２ O ３ / β-Ga ２ O ３ A method for producing a laminate, comprising the steps of: forming a gallium oxide melt containing a tetravalent heteroelement (a donor heteroelement) and a divalent heteroelement (an acceptor heteroelement) on the β-Ga ２ O ３ The β-Ga was grown on the substrate by liquid phase epitaxial growth. ２ O ３ forming a layer containing a single crystal, ２ O ３ The concentration difference between the tetravalent heteroelement and the divalent heteroelement in the layer containing the single crystal is −1×10 １９ ~ +1 x 10 １９ atoms / cm ３ and the obtained β-Ga ２ O ３ In the manufacturing method, the total content of hetero elements in the layer containing the single crystal is less than 0.01 mol %. The inventors have found that, in order to form a device layer for a power semiconductor, the difference in concentration between the tetravalent hetero elements (donor hetero elements) and the divalent hetero elements (acceptor hetero elements) should be less than −1×10 １９ ~ +1 x 10 １９ atoms / cm３ And the obtained β-Ga ２ O ３ It was found that the control method is effective by setting the total content of heterogeneous elements in the layer containing the single crystal to less than 0.01 mol%, and that precise carrier concentration control is possible by adding a small amount of heterogeneous elements compared to conventional techniques.

[0011] In the present invention, the difference in concentration between the tetravalent heteroelement (donor heteroelement) and the divalent heteroelement (acceptor heteroelement) is +1×10 from the viewpoint of carrier concentration control. １２ ~ +1 x 10 １９ atoms / cm ３ Preferably, +1×10 １３ ~ +1 x 10 １８ atoms / cm ３ More preferably, +1×10 １４ ~ +1 x 10 １８ atoms / cm ３ It is particularly preferable that β-Ga ２ O ３ The concentration of the foreign element in the layer containing the single crystal (preferably an epitaxial layer, more preferably a liquid phase epitaxial layer) is ３ It is expressed as the number of atoms of heteroelements per volume. Here, the concentration difference between tetravalent heteroelements and divalent heteroelements means the concentration difference between the total of tetravalent heteroelements and the total of divalent heteroelements, and corresponds to the donor concentration that provides electrons. If this value is positive, it will be an n-type semiconductor (carriers are electrons), and if it is negative, it will be a p-type semiconductor (carriers are holes). However, in Ga ２ O ３ In the case of , if this value is negative, holes do not flow and the material becomes an insulator.

[0012] In the present invention, the obtained β-Ga ２ O ３The total content of the hetero elements in the layer containing the single crystal is preferably 0.0095 mol% or less, and more preferably 0.0070 mol% or less, from the viewpoint of preventing an increase in gate leakage current or traps that block the gate electric field due to the presence of an excessive amount of the hetero elements. The lower limit is usually about 0.0005 mol%. In the present invention, the concentration difference and total content of the hetero elements described above can be measured by the method described in the examples below.

[0013] In the present invention, from the viewpoints of ease of availability of oxides and safety, the tetravalent hetero element is preferably one or more elements selected from the group consisting of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge, and C, and more preferably one or more elements selected from the group consisting of Sn, Si, and C. From the same viewpoints, the divalent hetero element is preferably one or more elements selected from the group consisting of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn, and Fe, and more preferably one or more elements selected from the group consisting of Mg, Ca, Pb, and Fe, and even more preferably one or more elements selected from the group consisting of Mg, Ca, and Fe. In the present invention, it is particularly preferable that the tetravalent hetero elements are Sn, Si, and C, and the divalent hetero elements are Mg, Ca, and Fe, and it is more preferable that the tetravalent hetero elements are Sn, Si, and C, and the divalent hetero element is Mg.

[0014] In one embodiment of the present invention, the gallium oxide melt is Ga ２ O ３ and SnO ２ , SiO ２ In one embodiment of the present invention, the gallium oxide melt preferably contains one or more selected from the group consisting of Ga ２ O ３ and PbO, Bi ２ O ３ , SnO ２ , SiO ２ Furthermore, in one embodiment of the present invention, the gallium oxide melt preferably contains one or more selected from the group consisting of Ga ２O ３ and PbO, Bi ２ O ３ , SnO ２ , SiO ２ In one embodiment of the present invention, the gallium oxide melt further contains one or more selected from the group consisting of MnO, MgO, CaO, and FeO. ２ , TiO ２ , ZrO ２ , GeO ２、 and CeO ２ It is preferable that the alloy contains at least one of the above-mentioned PbO, Bi ２ O ３ , SnO ２ , SiO ２ Oxide components such as MgO, CaO, and FeO are generally intentionally used as melt raw materials, but may be contained in other oxides used as melt raw materials.

[0015] β-Ga useful for power devices ２ O ３ / β-Ga ２ O ３ In the laminate, β-Ga ２ O ３ It is necessary to control the carrier concentration of the layer containing the single crystal (preferably an epitaxial layer, more preferably a liquid phase epitaxial layer). ２ O ３ is an oxide of trivalent Ga, and generally exhibits n-type conductivity. ２ O ３ By doping a different element into β-Ga, the carrier concentration, band gap, insulating properties, etc. can be given. ２ O ３ However, if MgO or ZnO is doped as a divalent impurity, the carrier electrons can be reduced. ２ and SnO ２ The carrier concentration can be increased by doping.

[0016] In the present invention, β-Ga ２ O ３The carrier concentration in the layer containing the single crystal is set to 1×10 from the viewpoint of imparting n-type conductivity. １３ ~1 x 10 １８ atoms / cm ３ It is preferable that the １４ ~1 x 10 １７ atoms / cm ３ More preferably, it is 1×10 １５ ~1 x 10 １７ atoms / cm ３ It is particularly preferable that the carrier concentration is 1 cm ３ It is the number of electrons or holes per volume. In the present invention, the carrier concentration can be measured by the method described in the examples below.

[0017] β-Ga obtained by the present invention ２ O ３ When forming an n-type conductive layer, the concentration of the heterogeneous element in the layer containing the single crystal is preferably 1.9×10 １８ atoms / cm ３ The concentration of divalent foreign elements is less than 1.9 × 10 １８ atoms / cm ３ More preferably, the concentration of the tetravalent foreign element is less than 1.0 × 10 １５ atoms / cm ３ 1.9 x 10 １８ atoms / cm ３ The concentration of divalent foreign elements is less than 1.9 × 10 １８ atoms / cm ３ Furthermore, when the conductive layer is used as a high-voltage layer of a power semiconductor, the concentration of the tetravalent foreign element is preferably less than 1×10 １５ atoms / cm ３ Above 5.0 x 10 １７ atoms / cm ３ The concentration of divalent foreign elements is less than 5.0 × 10 １７ atoms / cm ３ It is particularly preferable that the concentration of the tetravalent foreign element is less than 1 × 10 １７ atoms / cm ３ Above 1.0 x 10 １８atoms / cm ３ The concentration of divalent foreign elements is less than 1.0 × 10 １７ atoms / cm ３ On the other hand, when forming an insulating layer, the concentration of the tetravalent different element is preferably less than 1.0×10 １８ atoms / cm ３ The concentration of divalent foreign elements is less than 1.9 × 10 １８ atoms / cm ３ More preferably, the concentration of the tetravalent foreign element is less than 1.0 × 10 １３ atoms / cm ３ Above 1.0 x 10 １８ atoms / m ３ The concentration of divalent foreign elements is less than 1.0 × 10 １４ atoms / cm ３ Above 1.0 x 10 １８ atoms / m ３ Furthermore, in the case of an insulating layer application for a power semiconductor, the concentration of the tetravalent foreign element is preferably less than 1.0 × 10 １５ atoms / cm ３ The concentration of divalent foreign elements is less than 1.0 × 10 １５ atoms / cm ３ Above 1.0 x 10 １７ atoms / cm ３ It is particularly preferred that it is less than 10 ...

[0018] FIG. 2 is a schematic diagram showing an example of a typical LPE growth furnace. Inside the LPE growth furnace, a platinum crucible 7 containing melted raw materials (growth melt) 8 is placed on a crucible stand 9 made of mullite (a compound of aluminum oxide and silicon dioxide). Three-stage side heaters (upper heater 1, central heater 2, and lower heater 3) are provided on the sides of the platinum crucible 7 to heat and melt the raw materials in the platinum crucible 7. The heaters have independently controlled outputs, allowing for independent adjustment of the heat amount applied to the melt 8. A mullite furnace tube 11 is provided between the heater and the inner wall of the furnace, and a mullite furnace cover 12 is provided above the furnace tube 11. Note that the crucible stand 9 and the furnace tube 11 may be made of a material other than mullite. A pulling mechanism is provided above the platinum crucible 7. An alumina pulling shaft 5 is fixed to the pulling mechanism, and a substrate holder 6 and a substrate 4 fixed by the holder are provided at the tip of the shaft. A mechanism for rotating the shaft is provided above the pulling shaft 5. Additionally, a thermocouple 10 is provided at the bottom of the crucible.

[0019] Next, an example of the manufacturing method of the present invention will be described below with reference to FIG. 2. To melt the raw materials in the platinum crucible 7, the manufacturing furnace is heated until the raw materials are melted. The temperature is preferably raised to 600 to 1000°C, more preferably 700 to 900°C, and the raw material melt is allowed to stand for 2 to 3 hours to homogenize. Alternatively, instead of leaving it to stand, a platinum plate may be fixed to the tip of an alumina shaft, which is immersed in the melt, and the shaft may be rotated to stir the melt and homogenize it. β-Ga ２ O ３ It is desirable that the growth of the single crystal layer proceeds only directly below the substrate. ２ O ３ As the single crystal growth progresses, the grown single crystal adheres to the substrate due to convection in the melt, resulting in a different phase with a different growth orientation, which is undesirable. Therefore, the three-stage heater is offset to adjust the temperature so that the bottom of the crucible is several degrees higher than the melt surface. After the melt temperature has stabilized, the seed crystal substrate is brought into contact with the melt surface. After the seed crystal substrate has been immersed in the melt, the temperature is kept constant or begins to decrease at a rate of 0.025 to 5°C / hr, and the desired β-Ga is deposited on the surface of the seed crystal substrate. ２ O ３A single crystal layer is grown. During growth, the seed crystal substrate is rotated at 5 to 300 rpm by the rotation of the growth shaft, and is rotated in the opposite direction at regular intervals. After crystal growth for 30 minutes to 24 hours, the growth shaft is pulled up to separate the grown crystal from the melt, and the growth shaft is rotated at 50 to 300 rpm to separate the melt components adhering to the surface of the grown crystal. The crystal is then cooled to room temperature over 1 to 24 hours, and the desired β-Ga ２ O ３ / β-Ga ２ O ３ A laminate can be obtained.

[0020] The second embodiment of the present invention is a β-Ga ２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing a single crystal ２ O ３ / β-Ga ２ O ３ A laminate, ２ O ３ The layer containing the single crystal contains a tetravalent heteroelement and a divalent heteroelement, and the concentration difference between the tetravalent heteroelement and the divalent heteroelement is −1×10 １９ ~ +1 x 10 １９ atoms / cm ３ and the β-Ga ２ O ３ The total content of different elements in the layer containing the single crystal is less than 0.01 mol %, and the β-Ga ２ O ３ The Cl concentration in the layer containing the single crystal is 1×10 １６ atoms / cm ３ or the β-Ga ２ O ３ The layer containing the single crystal does not contain Cl. ２ O ３ / β-Ga ２ O ３ In the second embodiment, β-Ga ２ O ３ The layer containing the single crystal is preferably an epitaxial layer, more preferably a liquid phase epitaxial layer.２ O ３ / β-Ga ２ O ３ The laminate can be preferably produced by the first embodiment of the present invention described above.

[0021] Generally, Ga ２ O ３ When HVPE (Hydride Vapor Phase Epitaxy) is used as a doping method for a GaAs single crystal, the doping material is a halide compound (GaCl, GaCl ３ For example, when GaCl is used as a raw material, Cl is mixed in as an impurity. ２ O ３ The Cl concentration is 1×10 １６ ~2 x 10 １６ atoms / cm ３ On the other hand, when the liquid phase epitaxial method (LPE method) is used as in the first embodiment of the present invention, doping is possible by adding an oxide raw material to a gallium oxide melt without using a Cl-containing gas, and the resulting single crystal film is characterized by containing almost no Cl or C. That is, the β-Ga ２ O ３ / β-Ga ２ O ３ The laminate is β-Ga ２ O ３ The Cl concentration in the layer containing the single crystal is 1×10 １６ atoms / cm ３ Less than (preferably 1 x 10 １５ atoms / cm ３ or β-Ga ２ O ３ The layer containing the single crystal is characterized in that it does not contain Cl.

[0022] In the second embodiment of the present invention, β-Ga ２ O ３ From the viewpoint of application to power semiconductors, the carrier concentration in the layer containing the single crystal is 1×10 １３ ~1 x 10 １８ atoms / cm３ It is preferable that the １５ ~1 x 10 １８ atoms / cm ３ More preferably, it is 1×10 １５ ~1 x 10 １７ atoms / cm ３ It is particularly preferred that:

[0023] In the second embodiment of the present invention, the radius of curvature of the (100) direction is preferably 30 to ∞ m, more preferably 71 to ∞ m, from the viewpoint of ensuring flatness for polishing and electrode formation processes. In the present invention, the radius of curvature of the (100) direction can be measured by the method described in the examples below.

[0024] In the second embodiment of the present invention, the explanation of the hetero elements, the concentration difference between the tetravalent hetero elements and the divalent hetero elements, and the β-Ga ２ O ３ The above description of the first embodiment of the present invention applies to the total content of different elements in the layer containing the single crystal.

[0025] The third embodiment of the present invention is a β-Ga ２ O ３ / β-Ga ２ O ３ A laminate and the β-Ga ２ O ３ a Schottky electrode provided on the surface of the layer containing the single crystal; and ２ O ３ The β-Ga on the substrate ２ O ３ The semiconductor device includes a layer including a single crystal and an ohmic electrode provided on the surface opposite to the layer including the single crystal. ２ O ３ / β-Ga ２ O ３ A laminate and β-Ga ２ O ３ a Schottky electrode provided on the surface of the layer containing the single crystal; and ２ O ３ The β-Ga on the substrate２ O ３ and an ohmic electrode provided on the surface opposite to the layer containing the single crystal.

[0026] The fourth embodiment of the present invention is a β-Ga GaN crystal according to the second embodiment described above. ２ O ３ / β-Ga ２ O ３ A laminate and the β-Ga ２ O ３ a source electrode and a drain electrode provided directly on the surface of the layer containing the single crystal or via a contact region; and ２ O ３ The semiconductor device includes a gate electrode formed directly on the single crystal or via a gate insulating film. Fig. 4 is a schematic diagram showing an example of a semiconductor device according to a fourth embodiment of the present invention. The semiconductor device of Fig. 4 is a β-Ga ２ O ３ / β-Ga ２ O ３ A laminate and β-Ga ２ O ３ a source electrode and a drain electrode provided on the surface of the layer containing the single crystal via a contact region; and ２ O ３ and a gate electrode formed on the single crystal via a gate insulating film.

[0027] The fifth embodiment of the present invention is a β-Ga GaN crystal according to the second embodiment described above. ２ O ３ / β-Ga ２ O ３ A laminate and the β-Ga ２ O ３ a source electrode provided directly or via a contact region on the surface of the layer containing the single crystal; ２ O ３ a gate electrode embedded directly on a surface of the layer containing the single crystal or via a gate insulating film, or embedded directly in a trench formed on the surface or via a gate insulating film; ２ O ３ The β-Ga on the substrate ２ O３ and a drain electrode provided on the surface opposite to the layer containing the single crystal.

[0028] Hereinafter, β-Ga according to one embodiment of the present invention will be described. ２ O ３ / β-Ga ２ O ３ As a method for manufacturing a laminate, β-Ga ２ O ３ β-Ga on the substrate ２ O ３ A method for forming a layer containing a single crystal (epitaxial layer) will be described below. The present invention is not limited to the following examples.

[0029] (Example 1) The main components of the growth melt were PbO and Bi. ２ O ３ , Ga ２ O ３ (171.4 g, 181.1 g, and 58.7 g, respectively) were placed in a platinum crucible, and SnO ２ , SiO ２ , MgO (11.9 mg, 0 mg, 2.1 mg, respectively) were placed in a platinum crucible. The platinum crucible was placed in an LPE furnace and heated to 900°C for 3 hours to melt the β-Ga. The temperature of the LPE furnace was then lowered to 850°C, and the β-Ga. ２ O ３ The substrate surface of the substrate (11 mm x 11 mm x 0.65 mm) was brought into contact with the liquid, and a crystal thin film was formed over 1 hour (liquid phase epitaxial growth). After removing the melt components from the obtained laminate using hydrochloric acid, the surface was polished with colloidal silica abrasive grains to remove the β-Ga ２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing a single crystal ２ O ３ / β-Ga ２ O ３ A laminate was obtained.

[0030] (Examples 2 to 12, Comparative Examples 1 to 3) β-Ga was prepared in the same manner as in Example 1, except that the raw material composition was changed as shown in Table 1 below. ２ O ３ / β-Ga ２ O３ A laminate was obtained.

[0031]

[0032] <Impurity analysis> The β-Ga obtained by the above procedure ２ O ３ / β-Ga ２ O ３ The epitaxial layer (β-Ga ２ O ３ The amounts of different elements (Si, C, Cl) contained in the single crystal layer were analyzed by secondary ion mass spectrometry (SIMS) using the following measurement device and measurement conditions: Measurement device: CAMECA IMS-6f Measurement condition 1: Primary ion species: Cs ＋ , primary acceleration voltage: 15.0 kV, detection area: 30 μmφ On the other hand, the β-Ga obtained by the above procedure ２ O ３ / β-Ga ２ O ３ The epitaxial layer (β-Ga ２ O ３ The amounts of different elements (Sn, Mg, Pb, Bi) contained in the single crystal layer were analyzed by secondary ion mass spectrometry (SIMS) using the following measurement device and measurement conditions. Measurement device: CAMECA IMS-6f Measurement condition 2: Primary ion species: O ２ ＋ , primary acceleration voltage: 8.0 kV, detection area: 30 μmφ

[0033] FIG. 1 shows the β-Ga obtained in Example 1. ２ O ３ / β-Ga ２ O ３ The horizontal axis in FIG. 1 represents the surface of the epitaxial layer (β-Ga ２ O ３ The vertical axis in FIG. 1 represents the concentration of each element (atoms / cm ３) The lines on the right side of the graph represent the background level of each element concentration. The background level is the concentration of each element measured when there is no sample in the analyzer. The depth ranges indicated by "epitaxial layer" and "substrate" on the graph are the depths of β-Ga ２ O ３ A layer containing a single crystal, commercially available β-Ga containing Sn as a dopant ２ O ３ The measurement area of ​​the substrate is shown. ２ O ３ The rise in the concentration of each element near the surface of the layer containing the single crystal is due to the influence of substances adsorbed on the surface, and does not indicate the concentration of each element inside.

[0034] According to FIG. 1, the epitaxial layer (β-Ga ２ O ３ The concentration of C in the layer containing the single crystal was 9×10 １５ atoms / cm ３ This is below the detection limit of the SIMS instrument, i.e., 9 × 10 １５ atoms / cm ３ According to FIG. 1, the epitaxial layer (β-Ga ２ O ３ The concentration of Si in the layer containing the single crystal is 2×10 １５ atoms / cm ３ For 3 x 10 １５ atoms / cm ３ , that is, it can be seen that the epitaxial layer contains a certain concentration of Si. ２ O ３ The Cl concentration in the layer containing the single crystal was 2×10 １４ atoms / cm ３ This is consistent with the detection limit of the SIMS instrument, i.e., 2 × 10 １４ atoms / cm ３ According to FIG. 1, the epitaxial layer (β-Ga ２ O ３ The concentration of Sn in the layer containing the single crystal was 2×10１４ atoms / cm ３ For 6 x 10 １７ atoms / cm ３ , that is, it can be seen that the epitaxial layer contains a certain concentration of Sn. ２ O ３ The concentration of Mg in the layer containing the single crystal was 9×10 １３ atoms / cm ３ For 6 x 10 １７ atoms / cm ３ , that is, it is found that a certain concentration is contained in the epitaxial layer.

[0035] <Impurity conversion formula> The concentration of each element measured by secondary ion mass spectrometry (SIMS) (atoms / cm ３ ) from the following conversion formula, the epitaxial layer (β-Ga ２ O ３ The concentration (mol %) of each hetero element contained in the gallium oxide host crystal in the layer containing the β-Ga single crystal was calculated. ２ O ３ Concentration of different elements in (mol%) = SIMS concentration of each element / Na × Mw （Ｇａ２Ｏ３） / d （Ｇａ２Ｏ３） ×100 where SIMS concentration (atoms cm －３ ), Na: Avogadro's number ( / mol), Mw （Ｇａ２Ｏ３） : Molecular weight of gallium oxide (g / mol), d （Ｇａ２Ｏ３） : density of gallium oxide (g / cm ３ )

[0036] <Measurement of XRD rocking curve and curvature radius> If the single crystal substrate is warped, the orientation of the crystal lattice plane changes depending on the measurement position on the sample, and the incident angle ω at which X-ray diffraction occurs changes. The radius of curvature of the single crystal substrate can be calculated from this change. The radius of curvature of the wafer was measured using an X-ray diffractometer (Rigaku SmartLab). Using this device, the 2θ, ω, χ, and φ were adjusted to measure the β-Ga ２ O ３After the axis was set so that the peak of the (002) plane could be detected, measurements were made at a tube voltage of 40 kV and a tube current of 50 mA. The incident light was monochromated using four crystals of the Ge (220) plane. Other measurement conditions were as follows: Light source: Cu-Kα1 Wavelength: 0.1540593 nm Optical system: Parallel beam Measurement mode: ω scan (incident angle scan) ω range: β-Ga ２ O ３ The angle at which the (002) plane appears is set for each sample. ω range: 0.1 deg ω step: 0.0008 deg 2θ position: β-Ga ２ O ３ The angle at which the (002) plane appears was set for each sample. Entrance slit: 0.25 mm. Receiving slit: 1.1 mm. The wafer center was set to X=0, and the measurement position was shifted by 2 mm at a time. ω scans were performed at five points, and the diffraction peak angle at each position was measured. The radius of curvature R was calculated from the following formula, where ΔX is the displacement of the measurement position and Δω is the displacement of the ω peak. R=ΔX / sin Δω

[0037] <Fabrication of Schottky barrier diode and carrier concentration measurement> The obtained β-Ga ２ O ３ / β-Ga ２ O ３ The laminate sample was washed with isopropyl alcohol and ultrapure hydrogen peroxide, rinsed with ultrapure water, and dried by nitrogen blow. ２ O ３ An ohmic electrode made of Ti / Au was evaporated on the side of the substrate, and then an epitaxial layer (β-Ga ２ O ３A Schottky electrode made of Ni / Au was formed on the side of the single crystal layer (layer containing the single crystal). The ohmic electrode was formed uniformly over the entire surface, and the Schottky electrode was formed so that multiple electrodes of 1 mm diameter were formed within the surface. The current (I)-voltage (V) of the Schottky barrier diode fabricated as described above was measured, and the carrier concentration was calculated. Figure 5 shows the current (I)-voltage (V) characteristics of the obtained Schottky barrier diode. The measurement device and measurement conditions are as follows: Measurement device: FT 1030 FERA-DLTS device manufactured by PhysTech Sample temperature: room temperature, measurement frequency: 1 MHz, bias voltage: appropriately adjusted within the range of ±100 V

[0038] The epitaxial layers (β-Ga ２ O ３ The measurement results of the foreign element concentration, the total amount of foreign elements, the carrier concentration, and the radius of curvature of the (100) direction in the layer (including the single crystal) are shown in Table 2 below.

[0039] In Table 2 above, "tetravalent - divalent" represents the difference in concentration between tetravalent heterogeneous elements (total tetravalent) and divalent heterogeneous elements (total divalent). The heterogeneous elements contained in the epitaxial layer may be intentionally added, or may be introduced as trace impurities contained in the raw material. The smaller the value of the radius of curvature, the greater the warpage of the wafer. For example, 2.4 m in Comparative Example 3 represents the warpage of the surface of a sphere with a radius of 2.4 m. Large warpage is undesirable, as it can cause cracking during processing. Most of the radii of curvature in Examples 1 to 12 are ∞, but ∞ means no warpage.

[0040] REFERENCE SIGNS LIST 1 Upper heater 2 Central heater 3 Lower heater 4 Substrate 5 Pulling shaft (made of alumina) 6 Substrate holder 7 Platinum crucible 8 Melt in crucible 9 Crucible stand (made of mullite) 10 Crucible bottom thermocouple 11 Furnace tube (made of mullite) 12 Furnace lid (made of mullite)

Claims

1. β-Ga ２ O ３ β-Ga on the substrate ２ O ３ β-Ga having a layer containing single crystals ２ O ３ / β-Ga ２ O ３ A method for manufacturing a laminate, Using a gallium oxide melt containing a tetravalent hetero element and a divalent hetero element, the β-Ga ２ O ３ A layer containing a β-Ga ２ O ３ single crystal is formed on a substrate by liquid phase epitaxy, and the method includes a step of forming the layer. The obtained β-Ga ２ O ３ The concentration difference between the tetravalent heterogeneous element and the divalent heterogeneous element in the layer containing the single crystal is -1 × 10 １９ ~ + 1 × 10 １９ atoms / cm ３ And the obtained β-Ga ２ O ３ The manufacturing method wherein the total content of heterogeneous elements in the layer containing the single crystal is less than 0.01 mol%.

2. The aforementioned β-Ga ２ O ３ The carrier concentration in the layer containing the single crystal is 1 × 10 １３ ~1 x 10 １８ atoms / cm ３ The manufacturing method according to claim 1.

3. The manufacturing method according to claim 1 or 2, wherein the tetravalent heterogeneous element is one or more selected from the group consisting of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge, and C, and the divalent heterogeneous element is one or more selected from the group consisting of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn, and Fe.

4. The manufacturing method according to claim 3, wherein the tetravalent heterogeneous elements are Sn, Si, and C, and the divalent heterogeneous elements are Mg, Ca, and Fe.

5. The manufacturing method according to claim 3, wherein the tetravalent heterogeneous elements are Sn, Si, and C, and the divalent heterogeneous element is Mg.

6. The gallium oxide melt is Ga ２ O ３ And, SnO ２ SiO ２ The manufacturing method according to claim 1 or 2, comprising one or more selected from the group consisting of and MgO.

7. The gallium oxide melt is Ga ２ O ３ PbO, Bi ２ O ３ , SnO ２ SiO ２ The manufacturing method according to claim 1 or 2, comprising one or more selected from the group consisting of and MgO.