Semiconductor manufacturing method and transistor manufacturing method

Abstract

The present invention provides a method for manufacturing semiconductors with low conduction loss and a method for manufacturing transistors. [Solution] The semiconductor manufacturing method involves heating the substrate 10 to 530°C or 830°C, and directly or via another layer to the substrate 10, n-type α-(Al x Ga (1-x) The system includes a film deposition step in which a 2O3 (1≧X≧0.7) single crystal film is epitaxially grown to form the film.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing semiconductors and a method for manufacturing transistors. [Background technology]

[0002] Power devices used in electric vehicles or general-purpose inverters utilize semiconductors with large band gaps, such as SiC-based semiconductors, GaN-based semiconductors, and Ga2O3-based semiconductors.

[0003] Patent Document 1 discloses a Ga2O3-based crystalline film obtained by epitaxial growth on a Ga2O3-based crystalline substrate while precisely controlling the n-type conductivity. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6082700 [Overview of the project] [Problems that the invention aims to solve]

[0005] Semiconductors used in power devices can withstand higher voltages and reduce conduction losses as their dielectric breakdown strength increases. While high dielectric breakdown strength can be achieved with Ga2O3-based semiconductors, power devices are expected to become more widespread in the future. Therefore, semiconductors with even higher dielectric breakdown strength and thus lower conduction losses are in demand.

[0006] This invention was made to solve the above-mentioned problems, and aims to provide a method for manufacturing semiconductors with low conduction loss and a method for manufacturing transistors. [Means for solving the problem]

[0007] To achieve the objectives of the present invention, one mode of semiconductor manufacturing according to the present invention is: The substrate is heated to 530°C to 830°C, and n-type α-(Al) is applied directly to the substrate or via another layer. x Ga (1-x) The system includes a film deposition step in which a 2O3 (1≧X≧0.7) single crystal film is formed by epitaxial growth. It is characterized by the following:

[0008] To achieve the objectives of the present invention, one method of manufacturing a transistor according to the present invention is: The semiconductor is manufactured by the aforementioned semiconductor manufacturing method, The n-type α-(Al x Ga (1-x) A 2O3 single crystal film is used to manufacture a transistor that functions as an n-type electron generating layer. It is characterized by the following: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for manufacturing semiconductors with low conduction loss and a method for manufacturing transistors. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing a semiconductor according to an embodiment. [Figure 2] This is a diagram of a manufacturing apparatus for producing semiconductors according to an embodiment. [Figure 3] This is a flowchart showing the semiconductor manufacturing process according to the embodiment. [Figure 4] This is a cross-sectional view showing a semiconductor according to a modified example. [Figure 5] This is a cross-sectional view showing a semiconductor according to an embodiment. [Figure 6] This figure shows the relationship between annealing temperature and conductivity of semiconductors in the examples and comparative examples. [Figure 7] This figure shows the relationship between annealing time and conductivity of the semiconductor according to the example. [Figure 8](A) to (G) are electron microscope images of the semiconductor surface according to the examples and comparative examples. [Figure 9] This figure shows the relationship between the annealing temperature of semiconductors and the surface roughness of semiconductors in the examples and comparative examples. [Figure 10] This figure shows the relationship between the doping concentration and conductivity of the semiconductor according to the example. [Figure 11] This figure shows the relationship between the atmosphere and conductivity during the annealing process of semiconductors according to the examples. [Figure 12] This figure shows the relationship between conductivity and semiconductors containing Ga and semiconductors without Ga according to the examples. [Figure 13] This figure shows the relationship between Sn-doped semiconductors and conductivity according to the examples. [Figure 14] This figure shows the relationship between the Ga content and conductivity of the semiconductor according to the example. [Modes for carrying out the invention]

[0011] Hereinafter, a semiconductor and a method for manufacturing the semiconductor according to embodiments for carrying out the present invention will be described with reference to the drawings.

[0012] As shown in Figure 1, the semiconductor 1 according to the embodiment comprises a substrate 10, an interlayer 20, and n-type α-(Al x Ga (1-x) The device comprises a 2O3 single crystal film 30 and an electrode 40.

[0013] The substrate 10 is formed from an α-Al2O3 single crystal or (AlGa)2O3 crystal in a plate-like shape. The faces that appear on the main surface of the substrate 10 may be M faces, R faces, S faces, A faces, or C faces. Preferably, the substrate 10 is an α-Al2O3 single crystal formed so that the M face appears on the main surface.

[0014] The interlayer 20 is formed on the main surface of the substrate 10 and is n-type α-(Al x Ga (1-x)) It is a film disposed between the 2O3 single crystal film 30. The intermediate film 20 includes, for example, an α-Al2O3 single crystal film without added impurities (UID: UnIntentionally Doped), or an α-Al2O3 single crystal film added with at least one acceptor impurity of Mg, Zn, or N. The thickness t1 of the intermediate film 20 is preferably 10 nm or more and 1 μm or less, more preferably 30 nm or more and 100 nm or less. Note that the intermediate film 20 is provided as needed, and an n-type α-(Al x Ga (1-x) )2O3 single crystal film 30 may be formed directly on the substrate 10. Also, the intermediate film 20 may include a plurality of films.

[0015] The n-type α-(Al x Ga (1-x) )2O3 single crystal film 30 is a single crystal film of n-type α-(Al x Ga (1-x) )2O3 formed on the intermediate film 20 and contains at least one donor impurity of Si, Ge, or Sn. The n-type α-(Al x Ga (1-x) )2O3 single crystal film 30 is preferably a single crystal film with few defects. Also, 1≧X≧0.7, preferably 1≧X≧0.8, and more preferably X = 1. By having a large value of X, the dielectric breakdown strength can be increased. The thickness t2 of the n-type α-(Al x Ga (1-x) )2O3 single crystal film 30 is preferably 10 nm or more and 200 nm or less, more preferably 50 nm or more and 150 nm or less. The n-type α-(Al x Ga (1-x) )2O3 single crystal film 30 preferably contains at least one donor impurity of Si, Ge, or Sn. The carrier concentration of the n-type α-(Al x Ga (1-x) )2O3 single crystal film 30 is 1×10 17 / cm 3 or more and 1×10 20 / cm 3 or less. In terms of dopant concentration, this is 1×10 18 / cm 3 or more and 1×1020 / cm 3 The following is considered to be the case: n-type α-(Al x Ga (1-x) The surface roughness Rms of the 2O3 single crystal film 30 is preferably 2.7 nm or less, and more preferably 0.4 nm or less.

[0016] Electrode 40 is n-type α-(Al x Ga (1-x) The ) is formed on an Al2O3 single crystal film 30, for example, by stacking Ti / Au and subjecting it to heat treatment, causing Ti and Au to react with the Al2O3 surface. The size of the electrode 40 is, for example, 50 μm × 100 μm, and the distance L1 between electrodes is, for example, 2 μm.

[0017] Next, a method for manufacturing the semiconductor 1 having the above configuration will be described.

[0018] n-type α-(Al x Ga 1-x As an example of a method for producing a 2O3 single crystal film, the molecular beam epitaxy (MBE) method is described below. The MBE method is a crystal growth method that uses the MBE apparatus 100 shown in Figure 2, in which a solid element or compound is heated in an evaporation source called a cell, and the vapor generated by the heating is supplied to the substrate surface as a molecular beam.

[0019] The MBE apparatus 100 is n-type α-(Al x Ga 1-x This is an example of an apparatus used for forming a 2O3 single crystal film. As shown in Figure 2, it comprises a vacuum chamber 110, a substrate holder 120, a heating device 130, first to third cells 140a, 140b, and 140c, first to third heaters 150a, 150b, and 150c, a plasma cell 160, and a vacuum pump 170. With this configuration, the MBE apparatus 100 can grow crystals on the substrate surface using the Plasma-Assisted MBE method.

[0020] The vacuum chamber 110 forms a sealed space that houses a substrate holder 120 and the like for holding the substrate 10.

[0021] The substrate holder 120 holds the substrate 10 and is supported within the vacuum chamber 110, and is rotatably held via a shaft 121 by a motor (not shown).

[0022] The heating device 130 heats the substrate 10 held in the substrate holder 120 to a temperature of 530°C to 1000°C, preferably 530°C to 830°C. The heating device 130 may be a resistance heating device or a lamp heating device.

[0023] The first to third cells 140a, 140b, and 140c are containers provided for each atom or molecule constituting the thin film, and are made of, for example, boron nitride. The first cell 140a is filled with particulate Al raw material, such as powder or spherical. The purity of this powdered Al raw material is preferably 5N or higher, and more preferably 6N or higher. The second cell 140b is filled with powdered dopant raw material to be doped as a donor. The dopant raw material contains at least one of Si, Ge, or Sn. The Si, Ge, or Sn used here may be compounds such as oxides. The third cell 140c is filled with powdered Ga raw material. The purity of this powdered Ga raw material is preferably 6N or higher. Shutters are provided at the openings of the first to third cells 140a, 140b, and 140c.

[0024] The first to third heaters 150a, 150b, and 150c heat the first to third cells 140a, 140b, and 140c, respectively. By heating the first to third cells 140a, 140b, and 140c with the first to third heaters 150a, 150b, and 150c, atoms or molecules packed into the first to third cells 140a, 140b, and 140c are supplied to the substrate 10.

[0025] The plasma cell 160 supplies oxygen in a plasma state. The plasma cell 160 supplies oxygen in a plasma state under conditions such as oxygen flow rate: 0.5 sccm and oxygen plasma power: 200 W.

[0026] The vacuum pump 170 is used to discharge the air from the vacuum chamber 110.

[0027] Next, the manufacturing process for semiconductor 1 having the above configuration will be described.

[0028] As shown in Figure 3, the manufacturing process of semiconductor 1 includes a cleaning step (step S101), an interlayer deposition step (step S102), a film deposition step (step S103), an annealing step (step S104), and an electrode formation step (step S105).

[0029] In the cleaning step (step S101), the substrate 10 is cleaned. Suitable cleaning solutions include, for example, acetone, isopropanol, methanol, and deionized water. Preferably, the substrate 10 is a sapphire (α-Al2O3) substrate with the M-plane (0-2° off) exposed on the surface.

[0030] In the interlayer deposition process (step S102), the substrate 10, which was cleaned in the cleaning process (step S101), is fixed to the substrate holder 120 of the MBE apparatus 100, and an interlayer 20 is formed on the substrate 10. The interlayer 20 is, for example, a UID-Al2O3 film having a thickness of 50 nm. Specifically, the vacuum pump 170 is activated to raise the air pressure inside the vacuum chamber 110 to 2 × 10⁻¹⁰ -6 The pressure is reduced to below Pa. Next, the substrate 10 is heated to between 530°C and 830°C using the heating device 130. Then, plasma-state oxygen is supplied from the plasma cell 160, and the first cell 140a is heated by the first heater 150a, causing Al to evaporate and irradiate the surface of the substrate 10 as a molecular beam. As a result, Al2O3 is epitaxially grown on the main surface of the substrate 10, and an interlayer film 20 is formed on the main surface of the substrate 10.

[0031] In the film formation process (step S103), the interlayer 20 formed in the interlayer formation process (step S102) is coated with n-type α-(Al x Ga (1-x) A 2O3 single crystal film 30 is formed. In detail, the substrate 10 is then heated to 530°C to 830°C by the heating device 130. Next, oxygen is supplied from the plasma cell 160, for example, with an oxygen flow rate of 0.5 sccm to 1.5 sccm, an oxygen plasma power of 150W to 600W, preferably 150W to 300W, and a vacuum chamber 110 internal pressure of 1 × 10⁻¹⁰ -3 Oxygen in a plasma state is supplied under conditions equivalent to Pa. The first cell 140a is heated with the first heater 150a, and Al is evaporated and irradiated onto the surface of the substrate 10 as a molecular beam. The second cell 140b is heated with the second heater 150b, and the dopant raw material is evaporated and irradiated onto the surface of the substrate 10 as a molecular beam. The dopant raw material contains at least one of Si, Ge, or Sn, and Si, Ge, or Sn may be compounds such as oxides. The doping concentration is adjusted by the heating temperature of the second cell 140b. In addition, if necessary, the third cell 140c is heated with the third heater 150c, and Ga is evaporated and irradiated onto the surface of the substrate 10 as a molecular beam. As a result, n-type α-(Al) is deposited on the interlayer film 20. x Ga (1-x) )2O3 is epitaxially grown and at least one of the dopant Si, Ge, or Sn is added to n-type α-(Al x Ga (1-x) A 2O3 single crystal film 30 is formed.

[0032] In the annealing process (step S104), n-type α-(Al x Ga (1-x)Annealing is performed on the substrate 10 on which the 2O3 single crystal film 30 is formed. The temperature of the annealing is preferably 1200°C to 1400°C. The duration of the annealing is preferably 1 minute to 60 minutes, and more preferably 10 minutes to 60 minutes. The atmosphere for the annealing is air, high vacuum, and an inert gas atmosphere containing N2 or Ar, preferably an inert gas atmosphere containing N2 or Ar. By performing the annealing, compensation donors are reduced and conductivity is improved. Note that the annealing step (step S104) is not essential and may be omitted.

[0033] In the electrode formation step (step S105), n-type α-(Al) film formed in the film formation step (step S103) or annealed in the annealing step (step S104) is used. x Ga (1-x) An electrode 40 is formed on a 2O3 single crystal film 30. The electrode 40 is made by stacking Ti / Au, for example, with an RTA (Rapid Thermal Annealing) of 700°C or higher, preferably 800 to 900°C, atmosphere: N2, pressure: 1 × 10⁻⁶ 4 By heat treatment under conditions of Pa or higher and time: 1 min, Ti and Au are alloyed and formed. The size of the electrode 40 is, for example, 50 μm × 100 μm, and the distance between electrodes is 2 μm to 10 μm.

[0034] As described above, according to the semiconductor 1 and the method for manufacturing the semiconductor 1 of this embodiment, n-type α-(Al x Ga (1-x) The 2O3 single crystal film 30 is 1 × 10 17 / cm 3 The above 1 x 10 20 / cm 3 The following carrier concentrations are obtained, and good conductivity can be achieved. Specifically, the substrate 10 is heated to 530°C or higher and 830°C or lower, and n-type α-(Al) is obtained by the MBE method. x Ga (1-x) By epitaxially growing a 2O3 single crystal film 30, n-type α-(Al) with good conductivity is obtained. x Ga (1-x)A 2O3 single crystal film 30 can be obtained. Also, n-type α-(Al x Ga (1-x) The )2O3 single crystal film 30 has a large band gap, so a semiconductor 1 with high dielectric breakdown strength can be obtained. x Ga (1-x) The )2O3 single crystal film 30 can obtain good conductivity by containing at least one donor impurity from Si, Ge, or Sn. Also, n-type α-(Al x Ga (1-x) By annealing the 2O3 single crystal film 30 in an inert gas atmosphere at a temperature of 1200°C to 1400°C, an n-type α-(Al) film with a surface roughness Rms of 0.4 nm or less is obtained. x Ga (1-x) A 2O3 single crystal film 30 can be obtained. This allows for the production of n-type α-(Al x Ga (1-x) The Al2O3 single crystal film 30 can achieve excellent conductivity. Furthermore, the Al2O3 substrate used in semiconductor 1 is widely available as a low-cost, high-quality product and can be obtained at a lower cost compared to SiC or GaN substrates. For this reason, semiconductor 1 can be manufactured at a low cost.

[0035] (modified version) Furthermore, in the above embodiment, n-type α-(Al x Ga (1-x) A semiconductor 1 in which an electrode 40 is provided on a 2O3 single crystal film 30 was described. The semiconductor 1 is n-type α-(Al x Ga (1-x) It is sufficient to have a 2O3 single crystal film 30, and as shown in Figure 4, the substrate 11, the first intermediate layer 21, the second intermediate layer 31, and UID α-(Al 0.7 Ga 0.3 The transistor may also comprise an α-Al2O3 single crystal film 22, a source electrode 41, a gate electrode 42, and a drain electrode 43. The substrate 11 is formed from an α-Al2O3 single crystal in a plate shape. The first intermediate layer 21 is, for example, a 200 nm UID α-Al2O3 crystal film. The second intermediate layer 31 is n-type α-(Al x Ga (1-x))2O3 single crystal film, for example, having a thickness of 50 nm, is a Sn-doped n-type electron generation layer. α-(Al 0.7 Ga 0.3 The α-(Al)2O3 crystal film 22 has a thickness of, for example, 30 nm and is a UID high-resistance layer. The electrode distance L2 between the source electrode 41 and the gate electrode 42 is, for example, 1 μm. The electrode distance L3 between the gate electrode 42 and the drain electrode 43 is, for example, 2 μm. In this way, n-type α-(Al) 0.7 Ga 0.3 A field-effect transistor having a 2O3 crystal film 22 can be obtained. [Examples]

[0036] The effects of semiconductor 1 are demonstrated below by examples. These examples illustrate one embodiment of the present disclosure, and the present disclosure is not limited to these examples.

[0037] In Examples 1 to 7 and Comparative Examples 1 to 4, a semiconductor 1 comprising a substrate 12, an interlayer 23, a Si-doped n-type α-Al2O3 single crystal film 32, and an electrode 44, as shown in Figure 5, was fabricated by the MBE method using the MBE apparatus 100 described above.

[0038] A 10mm x 10m sapphire (α-Al2O3) substrate with the m-plane (2° off-center) exposed on the surface was used as substrate 12. A cleaning process was performed on substrate 12 using acetone, methanol, and deionized water.

[0039] Next, an interlayer deposition process was carried out to form an interlayer 23 on the substrate 12. The interlayer 23 was a UID-Al2O3 film with a thickness of 50 nm.

[0040] Next, a film deposition process was carried out to form an n-type α-Al2O3 single crystal film 32 on the interlayer film 23. The conditions for forming the n-type α-Al2O3 single crystal film 32 were: oxygen flow rate: 0.5 sccm, oxygen plasma power: 200 W, Al BEP (Beam Equivalent Pressure): 2 × 10⁻¹⁰ -6 Pa, substrate temperature T sub= It was 780 °C. Also, Si, which is a dopant, was added to the n-type α-Al₂O₃ single crystal film 32 at the doping concentration shown in Table 1. The doping concentration 8×10 18 (cm -3 ) is considered to correspond to a carrier concentration of 1×10 17 / cm 3 .

[0041] Next, annealing treatment was performed on the substrate 12 on which the n-type α-Al₂O₃ single crystal films 32 of Examples 1 to 7 and Comparative Examples 1 to 4 were formed under the conditions of temperature, time, and atmosphere shown in Table 1. Note that the fabrication conditions of the semiconductor 1 in Examples 1 to 7 and Comparative Examples 1 to 4 are the same except for the conditions described in Table 1.

[0042]

Table 1

[0043] Next, an electrode formation step of forming the electrode 44 on the n-type α-Al₂O₃ single crystal film 32 was performed. The electrode 40 was formed by laminating Ti(20 nm) / Au(50 nm) and performing heat treatment under the conditions of RTA: 850 °C, atmosphere: N₂, pressure: 1×10 4 Pa, and time: 1 min, so that Ti and Au reacted with the Al₂O₃ surface to be formed. The size of the electrode 44 was 50 μm × 100 μm, and the electrode distance L4 was 2 μm.

[0044] Next, voltages were applied to the electrodes 44 of the semiconductors 1 of Examples 1 to 7 and Comparative Examples 1 to 3 fabricated under the above-described conditions, and the current values were measured respectively. The current values with respect to the voltages of the semiconductors 1 of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in FIG. 6. Also, the current values with respect to the voltages of the semiconductors 1 of Examples 1, 5 to 7 are shown in FIG. 7.

[0045] For the semiconductors 1 of Examples 1 and 2, when a voltage of 80 V was applied by performing annealing treatment without annealing or at 1200 °C, 10 -11A current of A or more flowed, indicating good conductivity. Semiconductor 1 of Examples 3-7 was annealed at 1300°C or 1400°C, resulting in 10 -8 A current of A or more was flowing, indicating excellent conductivity.

[0046] As shown in Examples 1 and 2, it was found that good conductivity could be obtained with or without annealing, or by annealing at 1200°C. Furthermore, as shown in Examples 3 to 7, it was found that excellent conductivity could be obtained by annealing at 1300°C or 1400°C. In addition, as shown in Example 7, the best conductivity was obtained when annealing was performed at 1400°C for 60 minutes. As shown in Example 6, when annealing was performed at 1400°C for 10 minutes, it exhibited excellent conductivity at almost the same level as when annealing was performed for 60 minutes. As shown in Example 5, when annealing was performed at 1400°C for 1 minute, it showed lower conductivity compared to when annealing was performed for 10 minutes or 60 minutes, but 10 -8 A current of A or higher was flowing, indicating excellent conductivity. This revealed that when annealing was performed at 1400°C, the effect could be obtained with an annealing time of 1 minute or more, and a sufficient effect could be obtained with 10 minutes or more.

[0047] In contrast, semiconductor 1 of Comparative Examples 1 to 3 was annealed at 1000°C, 1100°C, or 1500°C, resulting in 10 -11 A current of less than A was flowing, indicating a malfunction.

[0048] Next, the surfaces of the n-type α-Al2O3 single crystal films 32 of Examples 1-4 and Comparative Examples 2-4, prepared under the conditions described above, were observed using an atomic force microscope as shown in Figures 8(A) to 8(G). Furthermore, the surface roughness Rms of semiconductor 1 of Examples 1-4 and Comparative Examples 2-4 was measured as shown in Figure 9.

[0049] The surface roughness Rms of the semiconductor 1 in Examples 1 to 4 was 2.7 nm or less, indicating that the surface roughness Rms was small. In particular, the surface roughness Rms of the semiconductor 1 in Examples 2 to 4 annealed at 1200 °C to 1500 °C was 0.4 nm or less, indicating that the surface roughness Rms was even smaller. It is considered that excellent or good conductivity can be obtained due to the small surface roughness Rms. In contrast, the surface roughness Rms of the semiconductor 1 in Comparative Examples 2 to 4 was 3.1 nm or more, indicating that the surface roughness Rms was large. Therefore, it is considered that conductivity can be obtained due to the small surface roughness Rms.

[0050] Next, the conductivity with respect to the doping concentration is verified.

[0051] Similar to Examples 1 to 7 and Comparative Examples 1 to 4, semiconductors 1 of Examples 8 to 10 were fabricated. After forming the intermediate film 23 on the substrate 12, when forming the n-type α-Al2O3 single crystal film 32 on the intermediate film 23, Si, which is a dopant, was added to the n-type α-Al2O3 single crystal film 32 at the doping concentrations shown in Table 2. Then, an annealing process was performed on the substrate 12 on which the n-type α-Al2O3 single crystal film 32 was formed under the conditions of temperature, time, and atmosphere shown in Table 2. Note that the fabrication conditions of the semiconductor 1 in Examples 8 to 10 were the same except for the conditions described in Table 2. Also, Example 4 shown in Table 2 is the same as Example 4 shown in Table 1.

[0052]

Table 2

[0053] Next, voltages were applied to the electrodes 44 of the semiconductors 1 of Examples 4, 8 to 10 fabricated under the above-described conditions, and the current values were measured respectively. The current values with respect to the voltages of the semiconductors 1 of Examples 4, 8 to 10 are shown in FIG. 10.

[0054] The semiconductors 1 of Examples 4 and 9 had doping concentrations of 8×10 18 cm -3 or 4×10 18 cm -3 and thus 10-8 A current of A or more flowed, indicating excellent conductivity. Semiconductor 1 in Examples 8 and 10 had a doping concentration of 1 × 10⁻⁶. 18 cm -3 or 2 × 10 19 cm -3 Therefore, 10 -12 A current of 1x or more was flowing, indicating good conductivity. Doping concentration: 1x10 18 cm -3 ~2×10 19 cm -3 is 1 × 10 17 / cm 3 ~2×10 19 / cm 3 This is thought to correspond to carrier concentrations within this range.

[0055] As a result, as shown in Examples 4 and 9, the doping concentration was 4 × 10 18 cm -3 The above 8 x 10 18 cm -3 It was found that excellent conductivity can be obtained by the following conditions. Also, as shown in Examples 8 and 10, when the doping concentration is 1 × 10⁻⁶ 18 cm -3 The above 2 x 10 19 cm -3 It was found that good conductivity can be obtained by the following conditions.

[0056] Next, we will examine the conductivity of the material in the annealing atmosphere.

[0057] Semiconductor 1 of Examples 11 and 12 was prepared in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 4. After forming an interlayer 23 on the substrate 12, when forming an n-type α-Al2O3 single crystal film 32 on the interlayer 23, the dopant Si was added to the n-type α-Al2O3 single crystal film 32 at the doping concentrations shown in Table 2. Subsequently, the substrate 12 on which the n-type α-Al2O3 single crystal film 32 was formed was subjected to an annealing process under the temperature, time, and atmosphere conditions shown in Table 2. The preparation conditions for semiconductor 1 in Examples 11 and 12 are the same except for the conditions described in Table 3. The high vacuum in Example 12 was 1 × 10⁻⁶ -4The value is Pa. Furthermore, Examples 1 and 4 shown in Table 3 are the same as Examples 1 and 4 shown in Table 1, respectively.

[0058] [Table 3]

[0059] Next, a voltage was applied to the electrodes 44 of the semiconductor 1 in Examples 1, 4, and 11-12, which were prepared under the conditions described above, and the current values ​​were measured for each. The current values ​​of the semiconductor 1 in Examples 1, 4, and 11-12 against voltage are shown in Figure 11.

[0060] Because semiconductor 1 in Example 11 is annealed in an Ar atmosphere, 10 -9 A current of A or more flowed, and it exhibited excellent conductivity, similar to semiconductor 1 of Example 4 which was annealed in an N2 atmosphere. Furthermore, semiconductor 1 of Example 12 was annealed in a high vacuum, so 10 -12 A current of A or more flowed, and it exhibited good conductivity, similar to semiconductor 1 in Example 1, which did not undergo annealing treatment.

[0061] This revealed that excellent conductivity can be obtained by annealing in an inert gas atmosphere containing N2 or Ar. When annealed in a high vacuum, the conductivity was inferior to that when annealed in an inert gas atmosphere containing N2 or Ar, but it was found to have the same level of good conductivity as when no annealing treatment was performed.

[0062] In the above-described example, the conductivity of the n-type α-Al2O3 single crystal film 32 was verified. Next, in which some of the Al is replaced with Ga, the conductivity of the n-type α-(Al x Ga (1-x) The conductivity of the 2O3 (1≧X≧0.7) single crystal film 33 was verified.

[0063] Semiconductor 1 of Example 13 was prepared in the same manner as semiconductor 1 of Example 1. After forming an interlayer 23 on the substrate 12, the interlayer 23 was modified by replacing Al with the amount of Ga shown in Table 4 to form n-type α-(Al x Ga(1-x) A 2O3 single crystal film 33 was formed. The conditions for creating semiconductor 1 in Example 13 are the same as those described in Table 5. Also, Example 1 shown in Table 4 is the same as Example 1 shown in Table 1. The Ga content of 30% is α-(Al 0.7 Ga 0.3 This indicates that it is 2O3.

[0064] [Table 4]

[0065] Next, a voltage was applied to the electrodes 44 of the semiconductor 1 of Examples 1 and 13, which were prepared under the conditions described above, and the current values ​​were measured. The current values ​​of the semiconductor 1 of Examples 1 and 13 against voltage are shown in Figure 12.

[0066] The semiconductor 1 of Example 13 had better conductivity than the semiconductor 1 of Example 1, which had an n-type α-Al2O3 single crystal film 32, because a portion of the Al was replaced with Ga. This showed that better conductivity can be obtained by replacing a portion of the Al in the n-type α-Al2O3 single crystal film 32 with Ga.

[0067] Next, n-type α-(Al) with added Sn x Ga (1-x) The conductivity of the 2O3 (1≧X≧0.7) single crystal film 34 was verified.

[0068] Semiconductor 1 of Example 14 was prepared in the same manner as semiconductor 1 of Example 1. After forming an interlayer 23 on the substrate 12, Al was replaced with the amount of Ga shown in Table 5 to form n-type α-(Al x Ga (1-x) A 2O3 single crystal film 34 was formed. n-type α-(Al x Ga (1-x) Sn was added as a dopant to the 2O3 single crystal film 34. The interelectrode distance L4 is 10 μm. The fabrication conditions for semiconductor 1 in Example 14 are the same as those described in Table 5. The Ga content of 20% is α-(Al 0.8 Ga 0.2 This indicates that it is 2O3.

[0069] [Table 5]

[0070] Next, voltages were applied to the electrodes 44 of the semiconductor 1 of Example 14, which was prepared under the conditions described above, and the current values ​​were measured. The current values ​​of the semiconductor 1 of Example 14 against voltage are shown in Figure 13.

[0071] Semiconductor 1 in Example 14 uses Sn instead of Si as the dopant, yet it exhibited conductivity. This demonstrates that conductivity can be obtained even when Sn is used instead of Si as the dopant.

[0072] Next, n-type α-(Al) with added Sn x Ga (1-x) The conductivity of the 2O3 (1≧X≧0.7) single crystal film 34 was investigated, examining the relationship between the Ga content, the distance between electrodes, and the conductivity.

[0073] Semiconductor 1 of Examples 15-20 and Comparative Example 5 was prepared in the same manner as semiconductor 1 of Example 1. After forming an interlayer 23 on the substrate 12, Al was replaced with the amount of Ga shown in Table 6 to form n-type α-(Al x Ga (1-x) A 2O3 single crystal film 34 was formed. n-type α-(Al x Ga (1-x) Sn was added as a dopant to the 2O3 single crystal film 34. Also, with the inter-electrode distance L4 shown in Table 6, n-type α-(Al x Ga (1-x) An electrode 44 was formed on a 2O3 single crystal film 34. The conditions for preparing semiconductor 1 in Examples 15-20 and Comparative Example 5 are the same except for the conditions listed in Table 6. The Ga content of 40% is α-(Al 0.6 Ga 0.4 This indicates that it is 2O3.

[0074] [Table 6]

[0075] Next, voltage was applied to the electrodes 44 of semiconductor 1 in Examples 15-20 and Comparative Example 5, which were prepared under the conditions described above, and the current values ​​were measured. The current values ​​of semiconductor 1 for Examples 15-20 and Comparative Example 5 against voltage are shown in Figure 14.

[0076] The semiconductor 1 of Examples 15-18, having a Ga content of 20%, showed better conductivity than the semiconductor 1 of Examples 19-20, which had a Ga content of 10%. Furthermore, good conductivity was also obtained with the semiconductor 1 of Example 13. This indicates that, up to a Ga content of 30%, increasing the Ga content leads to better conductivity. Additionally, the current value increased as the inter-electrode distance L4 decreased, and n-type α-(Al x Ga (1-x) It was found that the 2O3 single crystal film 34 had a constant resistance value. In contrast, semiconductor 1 of Comparative Example 5, which had a Ga content of 40%, showed poor conductivity. It is thought that a Ga content of 40% prevented good crystallinity from being obtained, and therefore poor conductivity could not be obtained.

[0077] As described above, it was found that semiconductor 1 of this embodiment can obtain good conductivity without annealing or by annealing at 1200°C. It was also found that excellent conductivity can be obtained by annealing at 1300°C or 1400°C. Furthermore, when annealing at 1400°C, it was found that an effect can be obtained with an annealing time of 1 minute or more, and a sufficient effect can be obtained with an annealing time of 10 minutes or more. In addition, when doped with Si, the doping concentration was 4 × 10⁻⁶. 18 cm -3 The above 8 x 10 18 cm -3 It was found that excellent conductivity can be obtained by the following conditions. Also, the doping concentration was 1 × 10⁻⁶. 18 cm -3 The above 2 x 10 19 cm -3It was found that good conductivity can be obtained by the following conditions. It was also found that excellent conductivity can be obtained by annealing in an inert gas atmosphere containing N2 or Ar. When annealing was performed in a high vacuum, the conductivity was inferior to that when annealing was performed in an inert gas atmosphere containing N2 or Ar, but it was found to have the same level of good conductivity as when no annealing was performed. It was also found that conductivity can be obtained by replacing Si with Sn as the dopant. It is also thought that conductivity can be obtained by replacing Ge as the dopant. Furthermore, it was found that even better conductivity can be obtained by replacing some of the Al in the n-type α-Al2O3 single crystal film 32 with Ga. It was also found that up to a Ga content of 30%, increasing the Ga content resulted in better conductivity. In contrast, when the Ga content was 40%, it was thought that good crystallinity could not be obtained, and therefore good conductivity could not be obtained.

[0078] This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated not by the embodiments, but by the claims. Various modifications made within the scope of the claims and the equivalent scope of the meaning of the invention are considered to be within the scope of this invention. [Explanation of Symbols]

[0079] 1… Semiconductor 10, 11, 12… circuit board 20, 23…interlayer 21…First interlayer 22…α-(Al 0.7 Ga 0.3 ) 2O3 single crystal film 30, 33, 34… n-type α-(Al x Ga (1-x) ) 2O3 single crystal film 31…Second interlayer 32...n-type α-Al2O3 single crystal film 40, 44...electrode 41…Source electrode 42… Gate 43... Drain electrode 100...MBE device 110...Vacuum chamber 120... Circuit board holder 121... Shaft 130...Heating device 140a, 140b, 140c... Cells 1 to 3 150a, 150b, 150c... Heaters 1 to 3 160…Plasma Cell 170... Vacuum pump T1, T2... thickness L1~L4…Distance between electrodes

Claims

1. The substrate is heated to 530°C to 830°C, and n-type α-(Al) is applied directly to the substrate or via another layer. ｘ Ga （１－ｘ） ) ２ O ３ The system includes a film deposition step in which a single crystal film (1 ≥ X ≥ 0.7) is formed by epitaxial growth. A semiconductor manufacturing method characterized by the following:

2. In the aforementioned film deposition process, plasma-state oxygen is supplied to a vacuum chamber in which the substrate is placed, and at least Al is evaporated and irradiated onto the substrate as a molecular beam. The semiconductor manufacturing method according to claim 1.

3. The n-type α-(Al) film formed in the aforementioned film formation step ｘ Ga （１－ｘ） ) ２ O ３ The system includes an annealing step in which a single crystal film is annealed in an inert gas atmosphere at a temperature of 1200°C to 1400°C. A method for manufacturing a semiconductor according to claim 1 or 2, characterized by the above.

4. The semiconductor comprises a semiconductor manufactured by the semiconductor manufacturing method described in any one of claims 1 to 3. The n-type α-(Al ｘ Ga （１－ｘ） ) ２ O ３ single crystal film manufactures a transistor that functions as an n-type electron generation layer, A method for manufacturing a transistor, characterized by the following features.

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