Method for producing beta-ga2o3 / beta-ga2o3 laminate, laminate obtained by the method, and semiconductor device comprising the laminate

Abstract

According to the present invention, a method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate having a layer containing a β-Ga2O3 single crystal on a β-Ga2O3 substrate is provided. The method includes the following steps: forming the layer containing the β-Ga2O3 single crystal on the β-Ga2O3 substrate using a gallium oxide melt containing a tetravalent and a divalent isomer via liquid phase epitaxy, wherein the concentration difference between the tetravalent and divalent isomers in the resulting layer containing the β-Ga2O3 single crystal is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 Furthermore, the total content of heterogeneous elements in the obtained layer containing β-Ga2O3 single crystals is less than 0.01 mol%.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate, the laminate obtained by the manufacturing method, and a semiconductor device comprising the laminate. Background Technology

[0002] Previously, methods for doping Ga2O3 single crystals included HVPE (Hydride Vapor Phase Epitaxy), MBE (Molecular Beam Epitaxy), and EFG (Edge-defined Film-fed Growth), which involve adding foreign elements simultaneously with crystal growth, and ion implantation, which involves adding foreign elements after the Ga2O3 single crystal has been grown.

[0003] The applicant of this application stated in Patent Document 1 that by using the LPE (Liquid phase epitaxy) method, even when there are foreign elements in a high concentration range of 0.01 mol% to 20 mol%, a film with good crystallinity can be obtained.

[0004] On the other hand, although Schottky barrier diodes and field-effect transistors made of Ga2O3-based compound semiconductors are known, it is necessary to control the carrier concentration of the epitaxial layer to 1×10⁻⁶. 13 ~6.0×10 17 atoms / cm 3 Approximately. It is particularly known that the breakdown voltage performance of the device improves when the carrier concentration is reduced (Patent Document 2).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 7380948

[0008] Patent Document 2: Japanese Patent No. 6758569 Summary of the Invention

[0009] In attempting to fabricate epitaxial layers for high-voltage devices as described above using the LPE method, the method in Patent Document 1 suffers from problems such as excessively high carrier concentration and too many foreign elements, making it difficult to control.

[0010] Furthermore, the existing HVPE method has the following problems: Cl is introduced into the epitaxial layer due to the use of halides in the raw materials. Since Cl acts as a dopant in β-Ga₂O₃ single crystal films, charge carriers are generated even without intentional addition of foreign elements. Additionally, since chloride ions readily corrode electrodes and wiring, materials containing Cl are not preferred for semiconductor applications.

[0011] The objective of this invention is to solve at least one of the aforementioned conventional problems. Furthermore, one embodiment of this invention aims to provide a method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate that reduces the content of dissimilar elements in a layer containing β-Ga2O3 single crystals obtained using the LPE method.

[0012] Furthermore, another objective of the present invention is to provide a β-Ga2O3 / β-Ga2O3 laminate with reduced Cl content in a layer containing a β-Ga2O3 single crystal.

[0013] It should be noted that in this specification, "dissimilar elements" refers to elements other than Ga and O. Furthermore, in this specification, "β-Ga₂O₃ / β-Ga₂O₃ laminate" refers to a laminate formed by stacking layers containing β-Ga₂O₃ single crystals on a substrate containing β-Ga₂O₃.

[0014] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that the above-mentioned problems can be solved by the following invention. That is, the present invention is as follows.

[0015] <1> A method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate, wherein the β-Ga2O3 / β-Ga2O3 laminate has a layer containing β-Ga2O3 single crystals on a β-Ga2O3 substrate.

[0016] The above manufacturing method includes the following steps: using a gallium oxide melt containing tetravalent and divalent hetero-elements, liquid phase epitaxy is used to form the layer containing β-Ga2O3 single crystal on the above β-Ga2O3 substrate.

[0017] The concentration difference between the aforementioned tetravalent and divalent isovalent elements in the obtained layer containing β-Ga₂O₃ single crystals is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 Furthermore, the total content of heterogeneous elements in the obtained layer containing β-Ga2O3 single crystals is less than 0.01 mol%.

[0018] <2> According to the manufacturing method described in <1> above, the carrier concentration in the layer containing β-Ga2O3 single crystals is 1×10213 ~1×10 18 atoms / cm 3 .

[0019] <3> According to the manufacturing method described in <1> or <2> above, the tetravalent isomorphic element is selected from one or more of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge and C, and the divalent isomorphic element is selected from one or more of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn and Fe.

[0020] <4> According to the manufacturing method described in <3> above, the tetravalent heterogeneous elements are Sn, Si and C, and the divalent heterogeneous elements are Mg, Ca and Fe.

[0021] <5> According to the manufacturing method described in <3> above, the tetravalent isomer is Sn, Si and C, and the divalent isomer is Mg.

[0022] <6> The manufacturing method according to any one of <1> to <5> above, wherein the gallium oxide melt contains Ga2O3 and one or more selected from SnO2, SiO2 and MgO.

[0023] <7> The manufacturing method according to any one of <1> to <6> above, wherein the gallium oxide melt contains Ga2O3 and one or more selected from PbO, Bi2O3, SnO2, SiO2 and MgO.

[0024] <8> A β-Ga2O3 / β-Ga2O3 laminate having a layer containing β-Ga2O3 single crystals on a β-Ga2O3 substrate is manufactured by any one of <1> to <7> above.

[0025] <9> A β-Ga₂O₃ / β-Ga₂O₃ laminate, having a layer containing β-Ga₂O₃ single crystals on a β-Ga₂O₃ substrate,

[0026] The aforementioned layer containing β-Ga₂O₃ single crystals contains both tetravalent and divalent isovalent elements, with a concentration difference of -1 × 10⁻⁶ between the tetravalent and divalent isovalent elements. 19 ~ +1×10 19 atoms / cm 3 The total content of heterogeneous elements in the aforementioned layer containing β-Ga2O3 single crystals is less than 0.01 mol%.

[0027] The Cl concentration in the layer containing β-Ga₂O₃ single crystals is less than 1 × 10⁻⁶. 16 atoms / cm 3Alternatively, the layer containing β-Ga2O3 single crystals may not contain Cl.

[0028] <10> According to the β-Ga2O3 / β-Ga2O3 stack described in <9> above, the carrier concentration in the layer containing the β-Ga2O3 single crystal is 1×102. 13 ~1×10 18 atoms / cm 3 .

[0029] <11> According to the β-Ga2O3 / β-Ga2O3 stack described in <9> or <10> above, the tetravalent heteroelement is selected from one or more of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge and C, and the divalent heteroelement is selected from one or more of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn and Fe.

[0030] <12> According to the β-Ga2O3 / β-Ga2O3 stack described in <11> above, the tetravalent heterogeneous element is Sn, Si and C, and the divalent heterogeneous element is Mg.

[0031] <13> A semiconductor device comprising:

[0032] The β-Ga₂O₃ / β-Ga₂O₃ laminate described in any one of <8> to <12> above,

[0033] Schottky electrodes disposed on the surface of the layer containing β-Ga2O3 single crystals, and

[0034] An ohmic electrode is disposed on the surface of the β-Ga2O3 substrate opposite to the layer containing the β-Ga2O3 single crystal.

[0035] <14> A semiconductor device comprising:

[0036] The β-Ga₂O₃ / β-Ga₂O₃ laminate described in any one of <8> to <12> above,

[0037] The source and drain electrodes are disposed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal, either in contact with the contact region.

[0038] A gate electrode formed directly or through a gate insulating film on the β-Ga2O3 single crystal between the source and the drain.

[0039] <15> A semiconductor device comprising:

[0040] The β-Ga₂O₃ / β-Ga₂O₃ laminate described in any one of <8> to <12> above,

[0041] The source electrode is disposed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal through a contact region.

[0042] A gate electrode formed directly or indirectly on the surface of the layer containing β-Ga2O3 single crystal, or directly or indirectly embedded in a trench formed on the surface by a gate insulating film.

[0043] A drain electrode disposed on the surface of the β-Ga2O3 substrate opposite to the layer containing the β-Ga2O3 single crystal.

[0044] According to one embodiment of the present invention, a method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate with reduced heterogeneous element content in a layer containing β-Ga2O3 single crystals obtained by the LPE method can be provided. Furthermore, according to another embodiment of the present invention, a β-Ga2O3 / β-Ga2O3 laminate with reduced Cl content in a layer containing β-Ga2O3 single crystals can be provided. Attached Figure Description

[0045] Figure 1 This is a graph showing the determination results of the laminate obtained in Example 1 based on secondary ion mass spectrometry (SIMS).

[0046] Figure 2 This is a schematic diagram showing an example of a typical LPE growth furnace.

[0047] Figure 3 This is a schematic diagram illustrating an example of a semiconductor device as one embodiment of the present invention.

[0048] Figure 4 This is a schematic diagram illustrating an example of a semiconductor device as one embodiment of the present invention.

[0049] Figure 5 This is a graph showing the current (I)-voltage (V) characteristics of the Schottky barrier diode obtained in the embodiment. Detailed Implementation

[0050] The present invention will now be described in detail. It should be noted that the present invention is not limited to the embodiments described below, and can be implemented in any way that achieves the desired inventive effect.

[0051] The first embodiment of the present invention is a method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate having a layer containing a β-Ga2O3 single crystal on a β-Ga2O3 substrate, comprising the following steps: forming the layer containing a β-Ga2O3 single crystal on the β-Ga2O3 substrate using a gallium oxide melt containing a tetravalent heteroelement (donor heteroelement) and a divalent heteroelement (acceptor heteroelement) via liquid phase epitaxy, wherein the concentration difference between the tetravalent heteroelement and the divalent heteroelement in the obtained layer containing the β-Ga2O3 single crystal is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 Furthermore, the total content of heterogeneous elements in the obtained layer containing β-Ga2O3 single crystals is less than 0.01 mol%.

[0052] The inventors have discovered that, in order to form a device layer for power semiconductors, the concentration difference between a tetravalent heteroelement (donor heteroelement) and a divalent heteroelement (acceptor heteroelement) is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 Furthermore, the total content of heterogeneous elements in the resulting layer containing β-Ga2O3 single crystals is less than 0.01 mol%, thus the control method is effective. Compared with previous techniques, it is possible to achieve precise carrier concentration control by adding a small amount of heterogeneous elements.

[0053] In this invention, from the viewpoint of controlling carrier concentration, the concentration difference between the tetravalent heteroelement (donor heteroelement) and the divalent heteroelement (acceptor heteroelement) is preferably +1 × 10⁻⁶. 12 ~ +1×10 19 atoms / cm 3 More preferably +1×10 13 ~ +1×10 18 atoms / cm 3 The preferred value is +1×10. 14 ~ +1×10 18 atoms / cm 3 .

[0054] The concentration of heterogeneous elements in the layer containing β-Ga₂O₃ single crystals (preferably an epitaxial layer, more preferably a liquid phase epitaxial layer) is determined by the concentration of heterogeneous elements per 1 cm⁻¹. 3 The atomic number of different elements in the volumetric gallium oxide.

[0055] Here, the concentration difference between tetravalent and divalent isovalent elements refers to the difference between the total concentration of tetravalent isovalent elements and the total concentration of divalent isovalent elements, which is equivalent to the donor concentration of electrons. When this value is positive, it becomes an n-type semiconductor (charge carriers are electrons), and when it is negative, it becomes a p-type semiconductor (charge carriers are holes). However, in the case of Ga2O3, when this value is negative, holes do not flow and it becomes an insulator.

[0056] In this invention, from the viewpoint of preventing an increase in the occurrence of traps that block gate leakage current and gate electric field due to the presence of excessive foreign elements, the total content of foreign elements in the obtained layer containing β-Ga2O3 single crystal is preferably 0.0095 mol% or less, more preferably 0.0070 mol% or less. The lower limit is usually around 0.0005 mol%.

[0057] In this invention, the concentration difference and total content of the aforementioned dissimilar elements can be determined by the methods described in the following examples.

[0058] In this invention, from the viewpoint of ease of obtaining oxides and safety, the aforementioned tetravalent isomer is preferably selected from one or more of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge and C, more preferably selected from one or more of Sn, Si and C. From the same viewpoint, the aforementioned divalent isomer is preferably selected from one or more of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn and Fe, more preferably selected from one or more of Mg, Ca, Pb and Fe, and even more preferably selected from one or more of Mg, Ca and Fe.

[0059] In this invention, the tetravalent isomers are particularly preferred to be Sn, Si and C, and the divalent isomers are preferred to be Mg, Ca and Fe. More preferably, the tetravalent isomers are Sn, Si and C, and the divalent isomers are preferred to be Mg.

[0060] In one embodiment of the present invention, the gallium oxide melt preferably contains Ga2O3 and one or more selected from SnO2, SiO2 and MgO.

[0061] In another embodiment of the present invention, the gallium oxide melt preferably contains Ga2O3 and one or more selected from PbO, Bi2O3, SnO2, SiO2 and MgO.

[0062] Furthermore, in one embodiment of the present invention, the above-mentioned gallium oxide melt preferably contains Ga2O3 and one or more selected from PbO, Bi2O3, SnO2, SiO2, MgO, CaO and FeO.

[0063] In one embodiment of the present invention, the gallium oxide melt preferably further comprises at least one of MnO2, TiO2, ZrO2, GeO2 and CeO2.

[0064] The aforementioned oxide components such as PbO, Bi2O3, SnO2, SiO2, MgO, CaO, and FeO are usually used intentionally as raw materials for molten liquids, and may also be included in other oxides used as raw materials for molten liquids.

[0065] In β-Ga₂O₃ / β-Ga₂O₃ stacks useful for power devices, it is necessary to control the carrier concentration of the layer containing the β-Ga₂O₃ single crystal (preferably an epitaxial layer, more preferably a liquid-phase epitaxial layer). β-Ga₂O₃ is an oxide of trivalent Ga and generally exhibits n-type conductivity. In the first embodiment of the present invention, carrier concentration, band gap, and insulation properties can be imparted by doping β-Ga₂O₃ with dissimilar elements. For example, doping β-Ga₂O₃ with MgO or ZnO as divalent impurities can reduce carrier electrons. Furthermore, doping with SiO₂ or SnO₂ as tetravalent impurities can increase the carrier concentration.

[0066] In this invention, from the viewpoint of imparting n-type conductivity, the carrier concentration in the layer containing β-Ga₂O₃ single crystals is preferably 1 × 10⁻⁶. 13 ~1×10 18 atoms / cm 3 More preferably 1×10 14 ~1×10 17 atoms / cm 3 The preferred value is 1×10 15 ~1×10 17 atoms / cm 3 It should be noted that carrier concentration refers to the concentration per 1 cm³. 3 The number of electrons or holes in a volume.

[0067] In this invention, the carrier concentration can be determined by the method described in the embodiments described later.

[0068] In this invention, when forming an n-type conductive layer, the concentration of the heterogeneous element in the layer containing β-Ga₂O₃ single crystals is preferably less than 1.9 × 10⁻⁶. 18 atoms / cm 3 The concentration of divalent heteroelement is less than 1.9 × 10⁻⁶. 18 atoms / cm 3 The preferred concentration of the tetravalent heteroelement is 1.0 × 10⁻⁶. 15 atoms / cm 3 Above and less than 1.9 × 10 18atoms / cm 3 The concentration of divalent heteroelement is less than 1.9 × 10⁻⁶. 18 atoms / cm 3 That's all.

[0069] Furthermore, when the conductive layer is used as a high-voltage withstand layer for power semiconductors, a concentration of 1×10⁻⁶ tetravalent heteroelements is particularly preferred. 15 atoms / cm 3 Above and less than 5.0 × 10 17 atoms / cm 3 The concentration of divalent heteroelement is less than 5.0 × 10⁻⁶. 17 atoms / cm 3 When the conductive layer is used as a high conductivity layer for power semiconductors, a concentration of 1×10⁻⁶ tetravalent heteroelements is particularly preferred. 17 atoms / cm 3 Above and less than 1.0 × 10 18 atoms / cm 3 The concentration of divalent heteroelement is less than 1.0 × 10⁻⁶. 17 atoms / cm 3 .

[0070] On the other hand, when forming the insulating layer, it is preferable that the concentration of the tetravalent heteroelement is less than 1.0 × 10⁻⁶. 18 atoms / cm 3 The concentration of divalent heteroelement is less than 1.9 × 10⁻⁶. 18 atoms / cm 3 The preferred concentration of the tetravalent heteroelement is 1.0 × 10⁻⁶. 13 atoms / cm 3 Above and less than 1.0 × 10 18 atoms / m 3 The concentration of the divalent heteroelement is 1.0 × 10⁻⁶. 14 atoms / cm 3 Above and less than 1.0 × 10 18 atoms / m 3 That's all.

[0071] Furthermore, when used as an insulating layer for power semiconductors, a concentration of less than 1.0 × 10⁻⁶ tetravalent is particularly preferred. 15 atoms / cm 3 The concentration of the divalent heteroelement is 1.0 × 10⁻⁶. 15 atoms / cm 3 Above and less than 1.0 × 10 17 atoms / cm 3 .

[0072] Figure 2 This is a schematic diagram showing an example of a typical LPE growth furnace.

[0073] Inside the LPE growth furnace, a platinum crucible 7, containing molten raw material as a liquid (growing melt) 8, is placed on a mullite (a compound of alumina and silica) crucible base 9. A three-section side heater (upper heater 1, central heater 2, and lower heater 3) is located on the outside and side of the platinum crucible 7 to heat and melt the raw material inside. The output power of each heater is independently controlled, and the heating amount of the liquid 8 is independently adjusted. A mullite core tube 11 is installed between the heater and the inner wall of the furnace, and a mullite furnace cover 12 is installed on top of the core tube 11. It should be noted that the crucible base 9 and the core tube 11 can be made of materials other than mullite. A lifting mechanism is installed above the platinum crucible 7. An alumina lifting shaft 5 is fixed to the lifting mechanism, and a substrate support 6 and a substrate 4 fixed to the support are provided at its front end. A mechanism for rotating the shaft is provided above the lifting shaft 5. In addition, a thermocouple 10 is provided at the bottom of the crucible.

[0074] Next, use Figure 2 An example of the manufacturing method of the present invention will be described.

[0075] To melt the raw material in the platinum crucible 7, the manufacturing furnace is heated to the point where the raw material is molten. Preferably, the temperature is raised to 600–1000°C, more preferably to 700–900°C, and then allowed to stand for 2–3 hours to homogenize the molten material. It should be noted that a platinum plate can also be fixed to the front end of an alumina shaft, immersed in the molten material, and the shaft rotated to perform a stirring operation to achieve homogenization of the molten material instead of standing. The growth of the β-Ga₂O₃ single crystal layer is preferably carried out only directly below the substrate. If the β-Ga₂O₃ single crystal is grown in the molten material other than directly below the substrate, the grown single crystal will adhere to the substrate due to convection within the molten material, becoming a heterogeneous phase with different orientations, which is therefore undesirable. Therefore, a temperature offset is set for the three-stage heater, adjusting it so that the bottom of the crucible is a few°C higher than the surface of the molten material. After the temperature of the molten material stabilizes, the seed crystal substrate is brought into contact with the surface of the molten material. After immersing the seed substrate in the molten liquid, the substrate is cooled at a constant temperature or at a rate of 0.025–5 °C / hr to allow a target β-Ga₂O₃ single crystal layer to grow on its surface. During growth, the seed substrate is rotated at 5–300 rpm by a growth axis, which is then reversed at regular intervals. After approximately 30 minutes to 24 hours of crystal growth, the growth axis is pulled to detach the crystal from the molten liquid, and the growth axis is rotated at 50–300 rpm to separate the molten liquid components adhering to the crystal surface. The crystal is then cooled to room temperature over 1–24 hours to obtain the target β-Ga₂O₃ / β-Ga₂O₃ laminate.

[0076] The second embodiment of the present invention is a β-Ga2O3 / β-Ga2O3 laminate having a layer containing β-Ga2O3 single crystals on a β-Ga2O3 substrate. The layer containing β-Ga2O3 single crystals contains a tetravalent iso-element and a divalent iso-element, and the concentration difference between the tetravalent iso-element and the divalent iso-element is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 The total content of heterogeneous elements in the aforementioned layer containing β-Ga₂O₃ single crystals is less than 0.01 mol%, and the Cl concentration in the aforementioned layer containing β-Ga₂O₃ single crystals is less than 1 × 10⁻⁶. 16 atoms / cm 3 Alternatively, the layer containing β-Ga2O3 single crystals may not contain Cl.

[0077] In the second embodiment, the layer containing β-Ga2O3 single crystals is preferably an epitaxial layer, and more preferably a liquid-phase epitaxial layer. That is, the β-Ga2O3 / β-Ga2O3 laminate of the second embodiment of the present invention can preferably be manufactured by the first embodiment of the present invention described above.

[0078] Generally, when using HVPE (Hydride Vapor Phase Epitaxy) as a doping method for Ga₂O₃ single crystals, Cl from the dopant (GaCl, GaCl₃, etc.) will be introduced as an impurity because the dopant material is a halide. For example, when GaCl is used as the dopant, Cl will be mixed into the β-Ga₂O₃ single crystal film, with a Cl concentration of 1 × 10⁻⁶. 16 ~2×10 16 atoms / cm 3 Around the same time, the concentration of charge carriers (free electrons) produced is also at the same level.

[0079] On the other hand, when using liquid phase epitaxy (LPE) as in the first embodiment of the present invention, doping can be performed by adding oxide raw materials to gallium oxide melt without using Cl-containing gas. The characteristic is that the resulting single-crystal film contains almost no Cl or C. That is, the β-Ga₂O₃ / β-Ga₂O₃ laminate of the present invention has the following characteristic: the Cl concentration in the layer containing the β-Ga₂O₃ single crystal is less than 1 × 10⁻⁶. 16 atoms / cm 3 (Preferred size: 1×10) 15 atoms / cm 3 (The following), or, the layer containing β-Ga2O3 single crystals does not contain Cl.

[0080] In the second embodiment of the present invention, from the viewpoint of application to power semiconductors, the carrier concentration in the layer containing β-Ga₂O₃ single crystal is preferably 1 × 10⁻⁶. 13 ~1×10 18 atoms / cm 3 More preferably 1×10 15 ~1×10 18 atoms / cm 3 The preferred value is 1×10 15 ~1×10 17 atoms / cm 3 .

[0081] In the second embodiment of the present invention, from the viewpoint of ensuring the flatness of the grinding process for electrode formation, the radius of curvature of the (100) crystal orientation is preferably 30 to ∞ m, more preferably 71 to ∞ m.

[0082] In this invention, the radius of curvature of the (100) crystal orientation can be determined by the method described in the embodiments described later.

[0083] In the second embodiment of the present invention, the description of heterogeneous elements, the concentration difference between tetravalent and divalent heterogeneous elements, and the total content of heterogeneous elements in the layer containing β-Ga2O3 single crystal are the same as those described in the first embodiment of the present invention.

[0084] A third embodiment of the present invention is a semiconductor device comprising: a β-Ga2O3 / β-Ga2O3 stack as described in the second embodiment above; a Schottky electrode disposed on the surface of the layer containing the β-Ga2O3 single crystal; and an ohmic electrode disposed on the surface of a β-Ga2O3 substrate opposite to the surface of the layer containing the β-Ga2O3 single crystal.

[0085] Figure 3 This is a schematic diagram showing an example of a semiconductor device as a third embodiment of the present invention. Figure 3 The semiconductor device includes: a β-Ga2O3 / β-Ga2O3 stack, a Schottky electrode disposed on the surface of the layer containing the β-Ga2O3 single crystal, and an ohmic electrode disposed on the surface of the β-Ga2O3 substrate opposite to the surface of the layer containing the β-Ga2O3 single crystal.

[0086] A fourth embodiment of the present invention is a semiconductor device comprising: a source and a drain electrode disposed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal, which is a β-Ga2O3 / β-Ga2O3 stack as described in the second embodiment above; and a gate electrode formed directly or indirectly on the β-Ga2O3 single crystal between the source and the drain electrode by a gate insulating film.

[0087] Figure 4 This is a schematic diagram showing an example of a semiconductor device as a fourth embodiment of the present invention. Figure 4 The semiconductor device includes: a β-Ga2O3 / β-Ga2O3 stack, a source and a drain disposed on the surface of the layer containing the β-Ga2O3 single crystal via contact regions, and a gate formed on the β-Ga2O3 single crystal between the source and the drain via a gate insulating film.

[0088] A fifth embodiment of the present invention is a semiconductor device comprising: a source electrode, which is a β-Ga2O3 / β-Ga2O3 stack as described in the second embodiment, disposed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal through a contact region; a gate electrode, which is formed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal through a gate insulating film or buried directly or indirectly in a trench formed on the surface through a gate insulating film; and a drain electrode disposed on the surface of the β-Ga2O3 substrate opposite to the side of the layer containing the β-Ga2O3 single crystal.

[0089] Example

[0090] The following describes a method for manufacturing a β-Ga2O3 / β-Ga2O3 laminate according to one embodiment of the present invention, which involves depositing a layer (epitaxial layer) containing a β-Ga2O3 single crystal on a β-Ga2O3 substrate. The present invention is not limited to any of the following embodiments.

[0091] (Example 1)

[0092] As the main components of the growth melt, PbO, Bi2O3, and Ga2O3 (171.4 g, 181.1 g, and 58.7 g, respectively) were added to a platinum crucible. Then, SnO2, SiO2, and MgO (11.9 mg, 0 mg, and 2.1 mg, respectively) were added as trace elements (dissimilar element components) to the platinum crucible. The platinum crucible was placed in an LPE furnace and heated to 900°C for 3 hours. The temperature of the LPE furnace was lowered to 850°C, and the substrate surface of the β-Ga2O3 substrate (11 mm × 11 mm × 0.65 mm) was brought into contact with the melt. A crystalline thin film (liquid phase epitaxial growth) was formed for 1 hour. After removing the melt components from the resulting laminate using hydrochloric acid, the surface was polished with colloidal silica as abrasive to obtain a β-Ga2O3 / β-Ga2O3 laminate with a layer containing β-Ga2O3 single crystals on the β-Ga2O3 substrate.

[0093] (Examples 2-12, Comparative Examples 1-3)

[0094] The feed composition was modified as shown in Table 1 below, and otherwise, the β-Ga2O3 / β-Ga2O3 laminate was obtained in the same manner as in Example 1.

[0095] [Table 1]

[0096]

[0097] <Impurity Analysis>

[0098] The amounts of heterogeneous elements (Si, C, Cl) in the epitaxial layers (including the layer containing the β-Ga2O3 single crystal) of the β-Ga2O3 / β-Ga2O3 stack obtained according to the above steps were analyzed using secondary ion mass spectrometry (SIMS) under the following measuring apparatus and conditions.

[0099] Measurement device: CAMECA IMS-6f

[0100] Measurement conditions 1: Primary ion beam: Cs ＋ Acceleration voltage: 15.0kV; Detection area: 30μmφ

[0101] On the other hand, the amount of different elements (Sn, Mg, Pb, Bi) contained in the epitaxial layer (including the layer containing the β-Ga2O3 single crystal) of the β-Ga2O3 / β-Ga2O3 stack obtained according to the above steps was analyzed by secondary ion mass spectrometry (SIMS) under the following measuring apparatus and measuring conditions.

[0102] Measurement device: CAMECA IMS-6f

[0103] Measurement condition 2: Primary ion beam: O2 ＋ Acceleration voltage: 8.0kV, Detection area: 30μmφ

[0104] Figure 1 The results of secondary ion mass spectrometry (SIMS) measurements of the β-Ga2O3 / β-Ga2O3 stack obtained in Example 1 are shown.

[0105] Figure 1 The horizontal axis represents the depth (μm) from the surface of the epitaxial layer (the surface of the layer containing the β-Ga2O3 single crystal). Figure 1 The vertical axis represents the concentration of each element (atoms / cm³). 3 Additionally, the line on the right side of the chart represents the background level of each element's concentration. The background level is the concentration of each element measured in the absence of a sample in the analytical apparatus.

[0106] The depth ranges shown in the charts as "epitaxial layer" and "substrate" represent the measurement areas of the layer containing β-Ga2O3 single crystals and the commercially available β-Ga2O3 substrate containing Sn as a dopant, respectively. It should be noted that the increase in the concentration of each element near the surface of the layer containing β-Ga2O3 single crystals is due to the influence of surface adsorbates and does not represent the concentration of elements within the layer.

[0107] according to Figure 1 It can be seen that the concentration of C in the epitaxial layer (containing the β-Ga2O3 single crystal) is 9 × 10⁻⁶. 15 atoms / cm 3 Consistent, meaning it is below the detection limit of the SIMS device, i.e., 9 × 10⁻⁶. 15 atoms / cm 3 the following.

[0108] according to Figure 1 It can be seen that the concentration of Si in the epitaxial layer (including the layer containing β-Ga2O3 single crystal) is 2 × 10⁻⁶ relative to the background concentration. 15 atoms / cm 3 , is 3×10 15 atoms / cm 3 This means that the epitaxial layer contains a certain concentration of Si.

[0109] according to Figure 1 It can be seen that the concentration of Cl in the epitaxial layer (including the layer containing the β-Ga2O3 single crystal) is 2×10⁻⁶ times that of the background concentration. 14 atoms / cm 3 Consistent, meaning it is below the detection limit of the SIMS device, i.e., 2 × 10⁻⁶. 14 atoms / cm 3 the following.

[0110] according to Figure 1 It can be seen that the Sn concentration in the epitaxial layer (the layer containing the β-Ga2O3 single crystal) is 2 × 10⁻⁶ relative to the background concentration. 14 atoms / cm 3 , is 6×10 17 atoms / cm 3 That is, the epitaxial layer contains a certain concentration of Sn.

[0111] according to Figure 1 It can be seen that the Mg concentration in the epitaxial layer (containing the β-Ga2O3 single crystal) is 9 × 10⁻⁶ relative to the background concentration. 13 atoms / cm 3 , is 6×10 17 atoms / cm 3 This means that the epitaxial layer contains a certain concentration of Mg.

[0112] <Conversion formula for impurities>

[0113] The concentrations of each element (atoms / cm³) determined by secondary ion mass spectrometry (SIMS) 3 The concentration (mol%) of each heterogeneous element in the parent gallium oxide in the epitaxial layer (the layer containing the β-Ga2O3 single crystal) can be calculated using the following conversion formula.

[0114] Concentration of different elements in β-Ga₂O₃ (mol%) = SIMS concentration of each element / Na × Mw （Ga2O3） / d （Ga2O3） ×100

[0115] Here, the SIMS concentration (atoms·cm) －3 Na: Avogadro's constant ( / mol), Mw （Ga2O3） Gallium oxide molecular weight (g / mol), d （Ga2O3） Density of gallium oxide (g / cm³) 3 ).

[0116] <Determination of XRD rocking curve and radius of curvature>

[0117] When a single-crystal substrate is warped, the orientation of the lattice planes changes depending on the measurement position on the sample, and the incident angle ω for X-ray diffraction also changes. The radius of curvature of the single-crystal substrate can be determined based on this change.

[0118] The radius of curvature of the wafer was determined using an X-ray diffraction apparatus (Rigaku SmartLab). The apparatus was calibrated by adjusting 2θ, ω, χ, and φ to detect the peaks of the (002) crystal plane of β-Ga₂O₃, and measurements were performed at a tube voltage of 40 kV and a tube current of 50 mA. It should be noted that the incident light was monochromated using a four-crystal Ge (220) crystal. Other measurement conditions are described below.

[0119] Light source: Cu-Kα1

[0120] Wavelength: 0.1540593nm

[0121] Optical system: parallel beam

[0122] Measurement mode: ω scan (incident angle scan)

[0123] ω range: The angle at which the β-Ga2O3 (002) crystal plane appears is set for each sample.

[0124] ω range: 0.1deg

[0125] ω step size: 0.0008 deg

[0126] 2θ position: The angle at which the β-Ga2O3 (002) crystal plane appears is set for each sample.

[0127] Entrance slit: 0.25mm

[0128] Light-receiving slit: 1.1mm

[0129] With the wafer center set to X = 0, the measurement position was shifted by 2 mm each time, and an ω scan was performed at 5 points to measure the diffraction peak angle at each position. The radius of curvature R was calculated according to the following formula, with the displacement of the measurement position set as ΔX and the displacement of the ω peak set as Δω.

[0130] R = ΔX / sinΔω

[0131] <Fabrication and Carrier Concentration Measurement of Schottky Barrier Diodes>

[0132] The obtained β-Ga₂O₃ / β-Ga₂O₃ laminate sample was cleaned with isopropanol and ultrapure hydrogen peroxide, rinsed with ultrapure water, and dried with a nitrogen stream. Using a vacuum evaporation apparatus, an ohmic electrode composed of Ti / Au was deposited on one side of the β-Ga₂O₃ substrate. Then, a Schottky electrode composed of Ni / Au was formed on the epitaxial layer (containing the β-Ga₂O₃ single crystal layer). The ohmic electrode was uniformly formed across the entire surface, and the Schottky electrode was formed by creating multiple 1 mmΦ electrodes within the plane. Current (I)-voltage (V) measurements were performed on the Schottky barrier diode fabricated above to calculate the carrier concentration. Figure 5 The current (I)-voltage (V) characteristics of the obtained Schottky barrier diode are shown below. The measuring apparatus and conditions are described below.

[0133] Measurement apparatus: PhysTech FT 1030 FERA-DLTS apparatus

[0134] Sample temperature: room temperature,

[0135] Measurement frequency: 1MHz

[0136] Bias voltage: Adjust appropriately within the range of ±100V.

[0137] The results of measurements of the heteroelement concentration and total heteroelement amount, carrier concentration, and radius of curvature of the (100) crystal direction in the epitaxial layer (layer containing β-Ga2O3 single crystal) of the laminates obtained in Examples 1-12 and Comparative Examples 1-3 are shown in Table 2 below.

[0138] [Table 2]

[0139]

[0140] In Table 2 above, “tetravalent - divalent” represents the concentration difference between tetravalent heterogeneous elements (total tetravalent) and divalent heterogeneous elements (total divalent).

[0141] In addition, foreign elements contained in the epitaxial layer can be intentionally introduced or introduced from trace impurities contained in the raw material.

[0142] A smaller radius of curvature indicates greater wafer warpage. For example, 2.4m in Comparative Example 3 represents the warpage of a sphere with a radius of 2.4m. Large warpage can lead to cracks during processing, which is undesirable. The radii of curvature in Examples 1-12 are almost all ∞, where ∞ indicates no warpage.

[0143] Symbol Explanation

[0144] 1. Upper heater

[0145] 2. Central heater

[0146] 3. Lower heater

[0147] 4 substrate

[0148] 5. Lifting shaft (made of alumina)

[0149] 6. Substrate support

[0150] 7 Platinum crucible

[0151] 8. Molten liquid in the crucible

[0152] 9. Crucible base (made of mullite)

[0153] 10. Crucible bottom thermocouple

[0154] 11. Furnace core tube (made of mullite)

[0155] 12. Furnace lid (made of mullite)

Claims

1. A method for manufacturing a β-Ga₂O₃ / β-Ga₂O₃ laminate, wherein the β-Ga₂O₃ / β-Ga₂O₃ laminate has a layer comprising β-Ga₂O₃ single crystals on a β-Ga₂O₃ substrate. The manufacturing method includes the following steps: using a gallium oxide melt containing tetravalent and divalent heteroelements, liquid phase epitaxy is used to form the layer containing β-Ga2O3 single crystals on the β-Ga2O3 substrate. The concentration difference between the tetravalent and divalent isovalent elements in the obtained layer containing β-Ga₂O₃ single crystals is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 Furthermore, the total content of heterogeneous elements in the obtained layer containing β-Ga2O3 single crystals is less than 0.01 mol%.

2. The manufacturing method according to claim 1, wherein, The carrier concentration in the layer containing β-Ga₂O₃ single crystals is 1×10⁻⁶. 13 ~1×10 18 atoms / cm 3 .

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

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

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

6. The manufacturing method according to any one of claims 1 to 5, wherein, The gallium oxide melt contains Ga2O3 and one or more selected from SnO2, SiO2 and MgO.

7. The manufacturing method according to any one of claims 1 to 6, wherein, The gallium oxide melt contains Ga2O3 and one or more selected from PbO, Bi2O3, SnO2, SiO2 and MgO.

8. A β-Ga2O3 / β-Ga2O3 laminate having a layer comprising β-Ga2O3 single crystals on a β-Ga2O3 substrate, which is manufactured by the method of any one of claims 1 to 7.

9. A β-Ga₂O₃ / β-Ga₂O₃ laminate, having a layer comprising β-Ga₂O₃ single crystals on a β-Ga₂O₃ substrate. The layer containing β-Ga₂O₃ single crystals contains a tetravalent and a divalent isovalent element, and the concentration difference between the tetravalent and divalent isovalent is -1 × 10⁻⁶. 19 ~ +1×10 19 atoms / cm 3 The total content of heterogeneous elements in the layer containing β-Ga2O3 single crystals is less than 0.01 mol%. The Cl concentration in the layer containing β-Ga₂O₃ single crystals is less than 1 × 10⁻⁶. 16 atoms / cm 3 Alternatively, the layer containing β-Ga2O3 single crystals may not contain Cl.

10. The β-Ga₂O₃ / β-Ga₂O₃ laminate according to claim 9, wherein, The carrier concentration in the layer containing β-Ga₂O₃ single crystals is 1×10⁻⁶. 13 ~1×10 18 atoms / cm 3 .

11. The β-Ga₂O₃ / β-Ga₂O₃ laminate according to claim 9 or 10, wherein, The tetravalent isomer is selected from one or more of Sn, Si, Mn, Ti, Zr, Hf, Ce, Ge and C, and the divalent isomer is selected from one or more of Mg, Be, Ca, Sr, Ba, Zn, Pb, Ni, Cu, Mn and Fe.

12. The β-Ga₂O₃ / β-Ga₂O₃ laminate according to claim 11, wherein, The tetravalent isomer is Sn, Si and C, and the divalent isomer is Mg.

13. A semiconductor device comprising: The β-Ga₂O₃ / β-Ga₂O₃ laminate according to any one of claims 8 to 12, Schottky electrodes disposed on the surface of the layer containing β-Ga2O3 single crystals, and An ohmic electrode is disposed on the surface of the β-Ga2O3 substrate opposite to the layer containing the β-Ga2O3 single crystal.

14. A semiconductor device comprising: The β-Ga₂O₃ / β-Ga₂O₃ laminate according to any one of claims 8 to 12, The source and drain electrodes are disposed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal via contact regions, and A gate electrode formed directly or through a gate insulating film on the β-Ga2O3 single crystal between the source and the drain.

15. A semiconductor device comprising: The β-Ga₂O₃ / β-Ga₂O₃ laminate according to any one of claims 8 to 12, The source electrode is disposed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal via a contact region. A gate formed directly or indirectly on the surface of the layer containing the β-Ga2O3 single crystal by a gate insulating film, or a gate buried directly or indirectly in a trench formed on the surface by a gate insulating film, and The drain electrode is disposed on the surface of the β-Ga2O3 substrate opposite to the layer containing the β-Ga2O3 single crystal.

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