Classifications

• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B19/00—Liquid-phase epitaxial-layer growth
  • C30B19/02—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux
  • C30B19/04—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux the solvent being a component of the crystal composition
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/10—Inorganic compounds or compositions
  • C30B29/16—Oxides
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/60—Insulated-gate field-effect transistors [IGFET]
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials

Definitions

• ⁇ 7> The method according to any one of the above items ⁇ 1> to ⁇ 6>, wherein the gallium oxide melt contains Ga 2 O 3 and one or more selected from the group consisting of PbO, Bi 2 O 3 , SnO 2 , SiO 2 , and MgO.
• ⁇ 8> A ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate having a layer containing a ⁇ -Ga 2 O 3 single crystal on a ⁇ -Ga 2 O 3 substrate, produced by the method described in any one of ⁇ 1> to ⁇ 7> above.
• ⁇ 11> The ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate according to ⁇ 9> or ⁇ 10>, 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.
• ⁇ 12> The ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate according to ⁇ 11>, wherein the tetravalent different elements are Sn, Si, and C, and the divalent different element is Mg.
• ⁇ 13> The ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate according to any one of ⁇ 8> to ⁇ 12> above, a Schottky electrode provided on the surface of the layer containing the ⁇ -Ga 2 O 3 single crystal; and an ohmic electrode provided on the surface of the ⁇ -Ga 2 O 3 substrate opposite to the layer containing the ⁇ -Ga 2 O 3 single crystal.
• ⁇ 14> The ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate according to any one of ⁇ 8> to ⁇ 12> above, a source electrode and a drain electrode provided directly or via a contact region on the surface of the layer containing the ⁇ -Ga 2 O 3 single crystal; and a gate electrode formed directly or via a gate insulating film on the ⁇ -Ga 2 O 3 single crystal between the source electrode and the drain electrode.
• ⁇ 15> The ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate according to any one of ⁇ 8> to ⁇ 12> above, a source electrode provided directly or via a contact region on the surface of the layer containing the ⁇ -Ga 2 O 3 single crystal; a gate electrode embedded directly on the surface of the layer containing the ⁇ -Ga 2 O 3 single crystal or via a gate insulating film, or embedded directly in a trench formed on the surface or via a gate insulating film; and a drain electrode provided on the surface of the ⁇ -Ga 2 O 3 substrate opposite to the layer containing the ⁇ -Ga 2 O 3 single crystal.
• FIG. 1 is a graph showing the measurement results of the laminate obtained in Example 1 by secondary ion mass spectrometry (SIMS).
• 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 the example.
• a first embodiment of the present invention is a method for producing a ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate having a layer containing a ⁇ -Ga 2 O 3 single crystal on a ⁇ -Ga 2 O 3 substrate , the method comprising: forming a layer containing the ⁇ -Ga 2 O 3 single crystal on the ⁇ -Ga 2 O 3 substrate by liquid phase epitaxial growth using a gallium oxide melt containing a tetravalent heteroelement (donor heteroelement) and a divalent heteroelement (acceptor heteroelement); the concentration difference between the tetravalent heteroelement and the divalent heteroelement in the obtained layer containing the ⁇ -Ga 2 O 3 single crystal is -1 ⁇ 10 19 to +1 ⁇ 10 19 atoms / cm 3 ; and the total content of the heteroelements in the obtained layer containing the ⁇ -Ga 2 O 3 single crystal is less than 0.01 mol%.
• the control method is effective by setting the difference in concentration between the tetravalent heterogeneous element (donor heterogeneous element) and the divalent heterogeneous element (acceptor heterogeneous element) to -1 x 10 19 to +1 x 10 19 atoms/cm 3 and setting the total content of heterogeneous elements in the obtained layer containing ⁇ -Ga 2 O 3 single crystal to less than 0.01 mol%, and that precise carrier concentration control is possible with the addition of a small amount of heterogeneous elements compared to conventional techniques.
• the difference in concentration between the tetravalent heteroelement (donor heteroelement) and the divalent heteroelement (acceptor heteroelement) is preferably +1 ⁇ 10 12 to +1 ⁇ 10 19 atoms/cm 3 , more preferably +1 ⁇ 10 13 to +1 ⁇ 10 18 atoms/cm 3 , and particularly preferably +1 ⁇ 10 14 to +1 ⁇ 10 18 atoms/cm 3, from the viewpoint of carrier concentration control .
• the concentration of the foreign element in the layer containing the ⁇ -Ga 2 O 3 single crystal preferably an epitaxial layer, more preferably a liquid phase epitaxial layer
• the difference in concentration between tetravalent heteroelements and divalent heteroelements refers to the difference in concentration between the sum of tetravalent heteroelements and the sum of divalent heteroelements, and corresponds to the donor concentration that provides electrons. If this value is positive, the semiconductor will be n-type (electron carriers), and if it is negative, the semiconductor will be p-type (hole carriers ). However, in the case of Ga2O3 , if this value is negative, holes do not flow and the semiconductor will be an insulator.
• the total content of different elements in the layer containing the obtained ⁇ -Ga 2 O 3 single crystal is preferably 0.0095 mol% or less, 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 different elements.
• the lower limit is usually about 0.0005 mol%.
• the concentration difference and total content of the different elements can be measured by the method described in the examples below.
• 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.
• 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.
• 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.
• the gallium oxide melt preferably contains Ga 2 O 3 and one or more selected from the group consisting of SnO 2 , SiO 2 , and MgO. In one embodiment of the present invention, the gallium oxide melt preferably contains Ga 2 O 3 and one or more selected from the group consisting of PbO, Bi 2 O 3 , SnO 2 , SiO 2 , and MgO. Furthermore, in one embodiment of the present invention, the gallium oxide melt preferably contains Ga 2 O 3 and one or more selected from the group consisting of PbO, Bi 2 O 3 , SnO 2 , SiO 2 , MgO, CaO, and FeO.
• the gallium oxide melt preferably further contains at least one of MnO 2 , TiO 2 , ZrO 2 , GeO 2 , and CeO 2 .
• the oxide components such as PbO, Bi2O3 , SnO2 , SiO2 , MgO , CaO, and FeO are generally intentionally used as melt raw materials, but may also be contained in other oxides used as melt raw materials.
• ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate useful as a power device, it is necessary to control the carrier concentration of the layer containing the ⁇ -Ga 2 O 3 single crystal (preferably an epitaxial layer, more preferably a liquid phase epitaxial layer).
• ⁇ -Ga 2 O 3 is an oxide of trivalent Ga and generally exhibits n-type conductivity.
• doping ⁇ -Ga 2 O 3 with a different element can impart carrier concentration, band gap, insulating properties, etc.
• doping ⁇ -Ga 2 O 3 with MgO or ZnO as a divalent impurity can reduce carrier electrons.
• doping SiO 2 or SnO 2 as a tetravalent impurity can increase the carrier concentration.
• the carrier concentration in the layer containing the ⁇ -Ga 2 O 3 single crystal is preferably 1 ⁇ 10 13 to 1 ⁇ 10 18 atoms/cm 3 , more preferably 1 ⁇ 10 14 to 1 ⁇ 10 17 atoms/cm 3 , and particularly preferably 1 ⁇ 10 15 to 1 ⁇ 10 17 atoms/cm 3.
• the carrier concentration is the number of electrons or holes per 1 cm 3 volume. In the present invention, the carrier concentration can be measured by the method described in the examples below.
• the concentration of the tetravalent heterogeneous element is 1 ⁇ 10 15 atoms/cm 3 or more and less than 5.0 ⁇ 10 17 atoms/cm 3 , and the concentration of the divalent heterogeneous element is less than 5.0 ⁇ 10 17 atoms/cm 3 ;
• the concentration of the tetravalent heterogeneous element is 1 ⁇ 10 17 atoms/cm 3 or more and less than 1.0 ⁇ 10 18 atoms/cm 3 , and the concentration of the divalent heterogeneous element is less than 1.0 ⁇ 10 17 atoms/cm 3 .
• the concentration of the tetravalent heterogeneous element is preferably less than 1.0 ⁇ 10 atoms/cm 3 and the concentration of the divalent heterogeneous element is preferably less than 1.9 ⁇ 10 atoms/cm 3 , and more preferably the concentration of the tetravalent heterogeneous element is 1.0 ⁇ 10 atoms/cm 3 or more and less than 1.0 ⁇ 10 atoms/cm 3 and the concentration of the divalent heterogeneous element is 1.0 ⁇ 10 atoms/cm 3 or more and less than 1.0 ⁇ 10 atoms/cm 3 .
• 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.
• a thermocouple 10 is provided at the bottom of the crucible.
• 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 material is left to stand for 2 to 3 hours to homogenize the raw material melt.
• a platinum plate may be attached to the tip of an alumina shaft, immersed in the melt, and stirred by rotating the shaft to homogenize the melt. Growth of the ⁇ -Ga 2 O 3 single crystal layer preferably proceeds only directly below the substrate.
• the three-stage heater is offset to adjust the crucible bottom to be several degrees higher than the melt surface.
• the seed crystal substrate is brought into contact with the melt surface.
• the temperature is maintained constant or decreased at a rate of 0.025 to 5°C/hr, and the desired ⁇ -Ga 2 O 3 single crystal layer is grown on the surface of the seed crystal substrate.
• the layer containing the ⁇ -Ga 2 O 3 single crystal is preferably an epitaxial layer, more preferably a liquid phase epitaxial layer. That is, the ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate of the second embodiment of the present invention can be preferably produced by the above-mentioned first embodiment of the present invention.
• the doping raw material is a halide compound (GaCl, GaCl3 , etc.), and Cl derived from the raw material is mixed in as an impurity.
• GaCl is used as the raw material
• Cl is mixed into the ⁇ - Ga2O3 -based single crystal film, and the Cl concentration is about 1 ⁇ 1016 to 2 ⁇ 1016 atoms/cm3, and the concentration of generated carriers (free electrons) is also about the same.
• the carrier concentration in the layer containing the ⁇ -Ga 2 O 3 single crystal is preferably 1 ⁇ 10 13 to 1 ⁇ 10 18 atoms/cm 3 , more preferably 1 ⁇ 10 15 to 1 ⁇ 10 18 atoms/cm 3 , and particularly preferably 1 ⁇ 10 15 to 1 ⁇ 10 17 atoms/cm 3 .
• the radius of curvature in 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.
• the radius of curvature in the (100) direction can be measured by the method described in the examples below.
• the explanation of the heterogeneous elements, the concentration difference between the tetravalent heterogeneous elements and the divalent heterogeneous elements, and the total content of the heterogeneous elements in the layer containing the ⁇ -Ga 2 O 3 single crystal are the same as those in the first embodiment of the present invention.
• ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate includes a ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate, a Schottky electrode provided on a surface of the layer containing the ⁇ -Ga 2 O 3 single crystal, and an ohmic electrode provided on a surface of the ⁇ -Ga 2 O 3 substrate opposite to the layer containing the ⁇ -Ga 2 O 3 single crystal.
• a fourth embodiment of the present invention is a semiconductor device including the ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate of the second embodiment described above, a source electrode and a drain electrode provided directly on the surface of the layer including the ⁇ -Ga 2 O 3 single crystal or via a contact region, and a gate electrode formed directly on the ⁇ -Ga 2 O 3 single crystal between the source electrode and the drain electrode or via a gate insulating film.
• 4 is a schematic diagram showing an example of a semiconductor device according to a fourth embodiment of the present invention. The semiconductor device in FIG.
• ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 stacked body includes a source electrode and a drain electrode provided on a surface of a layer including the ⁇ -Ga 2 O 3 single crystal via contact regions, and a gate electrode formed on the ⁇ -Ga 2 O 3 single crystal between the source electrode and the drain electrode via a gate insulating film.
• a fifth embodiment of the present invention is a semiconductor device including the ⁇ - Ga2O3 / ⁇ - Ga2O3 laminate of the second embodiment described above, a source electrode provided directly on the surface of the layer containing the ⁇ - Ga2O3 single crystal or via a contact region, a gate electrode buried directly on the surface of the layer containing the ⁇ - Ga2O3 single crystal or via a gate insulating film, or in a trench formed on the surface, or directly or via a gate insulating film, and a drain electrode provided on the surface of the ⁇ - Ga2O3 substrate opposite to the layer containing the ⁇ - Ga2O3 single crystal.
• a method for forming a layer (epitaxial layer) containing a ⁇ -Ga 2 O 3 single crystal on a ⁇ -Ga 2 O 3 substrate will be described as a manufacturing method of a ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate according to one embodiment of the present invention.
• the present invention is not limited to the following examples.
• Example 1 The main components of the growth melt were PbO, Bi2O3 , and Ga2O3 (171.4 g, 181.1 g, and 58.7 g , respectively), and trace elements (heterogeneous element components) of SnO2 , SiO2 , and MgO (11.9 mg, 0 mg, and 2.1 mg, respectively) were added 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 surface of a ⁇ - Ga2O3 substrate (11 mm x 11 mm x 0.65 mm) was brought into contact with the melt, and a crystal thin film was grown over 1 hour (liquid phase epitaxial growth).
• the surface was polished using colloidal silica as abrasive grains to obtain a ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate having a layer containing ⁇ -Ga 2 O 3 single crystal on the ⁇ -Ga 2 O 3 substrate.
• Examples 2 to 12 Comparative Examples 1 to 3
• a ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate was obtained in the same manner as in Example 1, except that the raw material composition was changed as shown in Table 1 below.
• Measuring device CAMECA IMS-6f Measurement condition 1: Primary ion species: Cs + , primary acceleration voltage: 15.0 kV, detection area: 30 ⁇ m ⁇
• the amounts of heterogeneous elements (Sn, Mg, Pb, Bi) contained in the epitaxial layer (layer containing ⁇ -Ga 2 O 3 single crystal) of the ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate obtained by the above procedure were analyzed using secondary ion mass spectrometry (SIMS) with the following measuring device and under the following measuring conditions.
• FIG. 1 shows the measurement results of the ⁇ -Ga 2 O 3 / ⁇ -Ga 2 O 3 laminate obtained in Example 1 by secondary ion mass spectrometry (SIMS).
• the horizontal axis in Fig. 1 represents the depth ( ⁇ m) from the surface of the epitaxial layer (the surface of the layer containing the ⁇ -Ga 2 O 3 single crystal), and the vertical axis in Fig. 1 represents the concentration of each element (atoms/cm 3 ).
• the line on the right side of the graph represents the background level of each element concentration.
• the background level is the concentration of each element measured with no sample present in the analyzer.
• the depth ranges indicated by "epitaxial layer” and “substrate” on the graph represent the measurement regions of a layer containing ⁇ -Ga 2 O 3 single crystals and a commercially available ⁇ -Ga 2 O 3 substrate containing Sn as a dopant, respectively. Note that the rise in concentration of each element near the surface of the layer containing ⁇ -Ga 2 O 3 single crystals is due to the influence of surface adsorbates and does not represent the concentration of each element inside.
• the C concentration in the epitaxial layer is consistent with the background concentration of 9 ⁇ 10 15 atoms/cm 3 , and is below the detection limit of the SIMS device, i.e., 9 ⁇ 10 15 atoms/cm 3 or less.
• the concentration of Si in the epitaxial layer is 3 ⁇ 10 15 atoms/cm 3 compared to the background concentration of 2 ⁇ 10 15 atoms/cm 3 , that is, Si is contained at a constant concentration in the epitaxial layer.
• the Cl concentration in the epitaxial layer is consistent with the background concentration of 2 ⁇ 10 14 atoms/cm 3 , and is below the detection limit of the SIMS device, i.e., 2 ⁇ 10 14 atoms/cm 3 or less.
• the Sn concentration in the epitaxial layer is 6 ⁇ 10 17 atoms/cm 3 compared to the background concentration of 2 ⁇ 10 14 atoms/cm 3 , that is, Sn is contained at a constant concentration in the epitaxial layer. According to FIG.

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