JP6932904B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device having a Schottky electrode.

Gallium oxide (Ga ₂ O ₃ ) is a transparent semiconductor that has a wide bandgap of 4.8-5.3 eV at room temperature and hardly absorbs visible light and ultraviolet light. Therefore, it is a promising material for use in optical / electronic devices and transparent electronics that operate in the deep ultraviolet region, and in recent years, it is a photodetector and light emitting based on _{gallium oxide (Ga 2} O _3). Diodes (LEDs) and transistors are being developed (see Non-Patent Document 1).

In addition, gallium oxide (Ga ₂ O ₃ ) has five crystal structures of α, β, γ, σ, and ε, and the most stable structure is generally β-Ga ₂ O ₃ . However, since β-Ga ₂ O ₃ has a β-gaul structure, it is not always suitable for use in semiconductor devices, unlike crystal systems generally used for electronic materials and the like. Further, since the growth of the β-Ga ₂ O ₃ thin film requires a high substrate temperature and a high degree of vacuum, there is also a problem that the manufacturing cost increases. Further, as described in Non-Patent Document 2, in β-Ga ₂ O ₃ , even a high concentration (for example, 1 × 10 ¹⁹ / cm ³ or more) dopant (Si) is 800 after ion implantation. It could not be used as a donor unless it was annealed at a high temperature of ° C to 1100 ° C.
On the other hand, α-Ga ₂ O ₃ has the same crystal structure as the sapphire substrate already sold for general purposes, and is therefore suitable for use in optical and electronic devices, and is more suitable than _{β-Ga 2} O _3. Since it has a wide bandgap, it is particularly useful for power devices, and therefore, there is a long-awaited situation for a semiconductor device using _{α-Ga 2} O _{3 as a semiconductor.}

In Patent Documents 1 and 2, β-Ga ₂ O ₃ is used as a semiconductor, and as an electrode capable of obtaining ohmic characteristics suitable for this, two layers composed of a Ti layer and an Au layer, a Ti layer, an Al layer and an Au layer are used. A semiconductor device using three layers, or four layers including a Ti layer, an Al layer, a Ni layer, and an Au layer is described.
Further, in Patent Document 3, β-Ga ₂ O ₃ is used as a semiconductor, and a semiconductor using any of Au, Pt, or a laminate of Ni and Au as an electrode capable of obtaining Schottky characteristics suitable for the β-Ga 2 O 3 is used as a semiconductor. The device is described.
However, when the electrodes described in Patent Documents 1 to _{3 are applied to a semiconductor device using α-Ga 2} O 3 as a semiconductor, they may not function as Schottky electrodes or ohmic electrodes, or the electrodes may not adhere to the film. There was a problem that the semiconductor characteristics were impaired.

Further, Patent Document 4 discloses a semiconductor device using _{α-Ga 2} O _{3 having a corundum structure as a semiconductor.} Then, as an example of the shot key electrode, Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In , Pd, Nd or Ag or other metals or alloys thereof, metal oxide conductive films such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), polyaniline, polythiophene or polypyrro- Organic conductive compounds such as ru, or mixtures thereof, and the like are mentioned. However, since such semiconductor devices are required to have oxidation resistance, metals and alloys are unsuitable, and even Pt having oxidation resistance has poor adhesion to _{α-Ga 2} O _{3 having a corundum structure.} In addition, there is a problem of causing deterioration of the film due to catalytic action and oxygen permeability. Further, as for the metal oxide film, tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. have poor cooperation _{with α-Ga 2} O _{3 having a corundum structure and have high resistance.} There was a problem such as becoming. In addition, there is a problem that the crystal structure of the semiconductor layer is damaged when the electrode is formed, which makes it difficult to realize an industrially useful semiconductor device.

Japanese Unexamined Patent Publication No. 2005-260101 Japanese Unexamined Patent Publication No. 2009-81468 Japanese Unexamined Patent Publication No. 2013-12760 Japanese Unexamined Patent Publication No. 2015-228495

Jun Liang Zhao et al, “UV and Visible Electroluminescence From a Sn: Ga2O3 / n + −Si Heterojunction by Metal−Organic Chemical Vapor Deposition”, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 58, NO.5 MAY 2011 Kohei Sasaki et al, “Si-Ion Implantation Doping in β-Ga2O3 and Its Application to Fabrication of Low-Resistance Ohmic Contacts”, Applied Physics Express 6 (2013) 086502

An object of the present invention is to provide a semiconductor device having excellent semiconductor characteristics and Schottky characteristics.

As a result of diligent studies to achieve the above object, the present inventors have formed a corundum structure in a metal oxide containing one or more metals belonging to any of the 6th to 9th groups of the periodic table. It was found that it has excellent adhesion to the InAlGa-based oxide semiconductor layer and also has excellent shotkey characteristics, and that it is useful as a shotkey electrode. Then, they have found that such a semiconductor device can solve the above-mentioned conventional problems at once.
In addition, after obtaining the above findings, the present inventors have further studied and completed the present invention.

That is, the present invention relates to the following invention.
[1] A semiconductor device including at least a Schottky electrode containing a metal oxide and a semiconductor layer containing indium, gallium, or aluminum.
The metal oxide is a metal oxide containing one or more metals belonging to any of Group 6 to Group 9 of the periodic table, and the semiconductor layer is an n + type semiconductor layer and the n + type. A semiconductor device including an n-type semiconductor layer provided on a semiconductor layer, wherein the shotkey electrode is provided on the n-type semiconductor layer .
[2] The semiconductor device according to the above [1], wherein the semiconductor layer is made of a crystalline oxide semiconductor film having a corundum structure as a constituent material.
[3] The semiconductor device according to the above [1] or [2], wherein the semiconductor layer contains indium or gallium.
[4] The semiconductor device according to any one of [1] to [3], wherein the metal oxide contains a metal of Group 6 of the periodic table.
[5] The semiconductor device according to any one of the above [1] to [3], wherein the metal oxide contains tungsten.
[6] The semiconductor device according to any one of [1] to [3], wherein the metal oxide contains a metal of Group 7 of the periodic table.
[7] The semiconductor device according to any one of the above [1] to [3], wherein the metal oxide contains rhenium.
[8] The semiconductor device according to any one of [1] to [3], wherein the metal oxide contains a metal of Group 8 of the periodic table.
[9] The semiconductor device according to any one of the above [1] to [3], wherein the metal oxide contains ruthenium.
[10] The semiconductor device according to any one of [1] to [3], wherein the metal oxide contains a metal of Group 9 of the periodic table.
[11] The semiconductor device according to any one of the above [1] to [3], wherein the metal oxide contains cobalt or iridium.
[12] The semiconductor device according to any one of the above [1] to [11], which is a Schottky barrier diode.
[13] A semiconductor system including a semiconductor device, wherein the semiconductor device is the semiconductor device according to any one of [1] to [12].

The semiconductor device of the present invention is excellent in semiconductor characteristics and Schottky characteristics.

It is a figure which shows typically a preferable example of the Schottky barrier diode (SBD) of this invention. It is a figure which shows typically a preferable example of the Schottky barrier diode (SBD) of this invention. It is a figure which shows typically a preferable example of the 1st metal layer used in this invention. It is a figure which shows typically a preferable example of the 2nd metal layer used in this invention. It is a schematic block diagram of the mist CVD apparatus used in an Example. It is a schematic block diagram of the mist CVD apparatus used in an Example. It is a figure which shows typically a preferable example of the metal semiconductor field effect transistor (MESFET) of this invention. It is a figure which shows typically a preferable example of a power-source system. It is a figure which shows typically a preferable example of a system apparatus. It is a figure which shows typically a preferable example of the power supply circuit diagram of a power supply device. It is a figure which shows the result of IV measurement of a comparative example.

The semiconductor device of the present invention is a semiconductor device including at least a Schottky electrode containing a metal oxide and a semiconductor layer containing indium, gallium or aluminum, and the metal oxide is a group 6 to No. 6 of the periodic table. It is a metal oxide containing one kind or two or more kinds of metals belonging to any of Group 9, and the semiconductor layer is an n + type semiconductor layer and an n− type semiconductor layer provided on the n + type semiconductor layer. The shot key electrode is characterized in that it is provided on the n− type semiconductor layer.

The semiconductor layer (hereinafter, also referred to as “crystalline oxide semiconductor film”) is not particularly limited as long as it is a semiconductor containing indium, gallium or aluminum, but is an oxide semiconductor from the viewpoint of having oxidation resistance. Is preferable. The oxide semiconductor preferably contains an InAlGaO-based semiconductor as a main component, more preferably contains at least gallium or indium, and most preferably contains at least gallium. Here, the InAlGaO based semiconductor, _{typically, In X Al Y Ga Z O} 3 indicates (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5~2.5), It can be overlooked as the same material system containing gallium oxide. Further, in the present invention, it is preferable that the semiconductor layer is made of a crystalline oxide semiconductor film having a corundum structure as a constituent material. Incidentally, the "main component" such as crystalline If oxide semiconductor is α-Ga ₂ O _3, the atomic ratio of gallium in a proportion of more than 0.5 α-Ga ₂ O of metal elements in the film _{If 3} is included, that is fine. In the present invention, the atomic ratio of gallium in the metal element in the film is preferably 0.7 or more, more preferably 0.8 or more. The thickness of the crystalline oxide semiconductor film is not particularly limited, and may be 1 μm or less, or 1 μm or more. The crystalline oxide semiconductor film is usually a single crystal, but may be a polycrystal.

The crystalline oxide semiconductor film preferably contains a dopant. The dopant is not particularly limited and may be a known one. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. In the present invention, the dopant is preferably Sn. The Sn content is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic%, and 0.00001 atomic% in the composition of the crystalline oxide semiconductor film. Most preferably, it is 10 atomic%.

In the crystalline oxide semiconductor film, for example, the raw material solution is atomized or dropleted (atomization / droplet atomization step), and the obtained mist or droplet is conveyed onto the substrate with a carrier gas (transportation step). ), Then, by thermally reacting the mist or droplets in the film forming chamber, a crystalline oxide semiconductor film containing a crystalline oxide semiconductor as a main component is laminated on the substrate (deposition step). Obtained in.

(Atomization / droplet formation process)
In the atomization / droplet atomization step, the raw material solution is atomized or dropletized. The means for atomizing or dropletizing the raw material solution is not particularly limited as long as the raw material solution can be atomized or atomized, and may be known means, but in the present invention, ultrasonic waves are used. The atomizing means or droplet forming means used is preferable. Mists or droplets obtained using ultrasonic waves are preferable because they have a zero initial velocity and float in the air. For example, instead of spraying them like a spray, they float in space and are transported as gas. Since it is a possible mist, it is not damaged by collision energy, so it is very suitable. The droplet size is not particularly limited and may be a droplet of about several mm, but is preferably 50 μm or less, and more preferably 100 nm to 10 μm.

(Raw material solution)
The raw material solution contains a material that can be atomized or atomized, and is not particularly limited as long as it contains dehydrogen, and may be an inorganic material or an organic material. In the invention, it is preferably a metal or metal compound and is selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium, calcium, silicon, yttrium, strontium and barium. More preferably, it contains one or more metals.

In the present invention, as the raw material solution, a solution in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or a salt can be preferably used. Examples of the form of the complex include an acetylacetonate complex, a carbonyl complex, an ammine complex, and a hydride complex. Examples of the salt form include organic metal salts (for example, metal acetate, metal oxalate, metal citrate, etc.), metal sulfide salts, nitrified metal salts, phosphor oxide metal salts, and metal halide metal salts (for example, metal chloride). Salts, metal bromide salts, metal iodide salts, etc.) and the like.

Further, it is preferable to mix an additive such as a hydrohalic acid or an oxidizing agent with the raw material solution. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydrogen iodide acid. Among them, hydrobromic acid or hydrogen iodide acid is used because a better quality film can be obtained. Is preferable. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), benzoyl peroxide (C ₆ H ₅ CO) ₂ O _{2 and the} like. Examples include hydrogen peroxide, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, and organic peroxides such as peracetic acid and nitrobenzene.

The raw material solution may contain a dopant. Doping can be performed satisfactorily by including the dopant in the raw material solution. The dopant is not particularly limited as long as it does not interfere with the object of the present invention. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. The concentration of the dopant may usually be about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant should be as ^{low as about 1 × 10 17} / cm ³ or less, for example. You may. Further, according to the present invention, the dopant may be contained in a high concentration of ^{about 1 × 10 20} / cm ^{3 or more.}

The solvent of the raw material solution is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of the inorganic solvent and the organic solvent. In the present invention, the solvent preferably contains water, and more preferably water or a mixed solvent of water and alcohol.

(Transport process)
In the transfer step, the mist or the droplets are conveyed into the film forming chamber by the carrier gas. The carrier gas is not particularly limited as long as the object of the present invention is not impaired, and for example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas is a suitable example. Can be mentioned. Further, the type of the carrier gas may be one type, but may be two or more types, and a diluted gas having a reduced flow rate (for example, a 10-fold diluted gas) or the like is further used as the second carrier gas. May be good. Further, the carrier gas may be supplied not only at one location but also at two or more locations. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of a diluting gas, the flow rate of the diluting gas is preferably 0.001 to 2 L / min, more preferably 0.1 to 1 L / min.

(Film formation process)
In the film forming step, a crystalline oxide semiconductor film is formed on the substrate by thermally reacting the mist or droplets in the film forming chamber. The thermal reaction may be such that the mist or droplets react with heat, and the reaction conditions and the like are not particularly limited as long as the object of the present invention is not impaired. In this step, the thermal reaction is usually carried out at a temperature equal to or higher than the evaporation temperature of the solvent, but is preferably not too high (for example, 1000 ° C.) or lower, more preferably 650 ° C. or lower, and most preferably 300 ° C. to 650 ° C. preferable. Further, the thermal reaction may be carried out in any of a vacuum, a non-oxygen atmosphere, a reducing gas atmosphere and an oxygen atmosphere as long as the object of the present invention is not impaired, but the thermal reaction may be carried out in a non-oxygen atmosphere or oxygen. It is preferably performed in an atmosphere. Further, it may be carried out under any conditions of atmospheric pressure, pressurization and depressurization, but in the present invention, it is preferably carried out under atmospheric pressure. The film thickness can be set by adjusting the film formation time.

(Hypokeimenon)
The substrate is not particularly limited as long as it can support the crystalline oxide semiconductor film. The material of the substrate is not particularly limited as long as it does not interfere with the object of the present invention, and may be a known substrate, an organic compound, or an inorganic compound. The shape of the substrate may be any shape and is effective for any shape, for example, plate-like, fibrous, rod-like, columnar, prismatic, such as a flat plate or a disk. Cylindrical, spiral, spherical, ring-shaped and the like can be mentioned, but in the present invention, a substrate is preferable. The thickness of the substrate is not particularly limited in the present invention.

The substrate is not particularly limited as long as it has a plate shape and serves as a support for the crystalline oxide semiconductor film. It may be an insulator substrate, a semiconductor substrate, a metal substrate or a conductive substrate, but the substrate is preferably an insulator substrate, and the surface is made of metal. A substrate having a film is also preferable. The metal film is preferably a multilayer film. The substrate includes, for example, a base substrate containing a substrate material having a corundum structure as a main component, a base substrate containing a substrate material having a β-gaul structure as a main component, and a substrate material having a hexagonal structure as a main component. Examples include a base substrate. Here, the "main component" means that the substrate material having the specific crystal structure is preferably 50% or more, more preferably 70% or more, still more preferably 90% or more, in terms of atomic ratio, with respect to all the components of the substrate material. It means that it is contained in% or more, and may be 100%.

The substrate material is not particularly limited and may be a known one as long as the object of the present invention is not impaired. Examples of the substrate material having the corundum structure are α-Al ₂ O ₃ (sapphire substrate) or α-Ga ₂ O ₃ , and a-plane sapphire substrate, m-plane sapphire substrate, and r-plane sapphire substrate are preferable. , C-plane sapphire substrate, α-type gallium oxide substrate (a-plane, m-plane or r-plane) and the like are more preferable examples. As the base substrate containing the substrate material having a β-gaul structure as a main component, for example, β-Ga ₂ O ₃ substrate or Ga ₂ O ₃ and Al ₂ O ₃ are included, and Al ₂ O ₃ is more than 0 wt%. Examples thereof include a mixed crystal substrate having a content of 60 wt% or less. Examples of the base substrate containing a substrate material having a hexagonal structure as a main component include a SiC substrate, a ZnO substrate, and a GaN substrate.

In the present invention, it is preferable that the substrate has a metal or corundum structure on a part or all of the surface. When the substrate has a corundum structure, it is more preferably a base substrate containing a substrate material having a corundum structure as a main component, and most preferably a sapphire substrate or an α-type gallium oxide substrate. Further, the substrate may contain aluminum, and in this case, it is preferable that the substrate is a base substrate containing an aluminum-containing substrate material having a corundum structure as a main component, and a sapphire substrate (preferably c-plane sapphire substrate, a-plane). A sapphire substrate, an m-plane sapphire substrate, and an R-plane sapphire substrate) are more preferable. Further, the substrate preferably contains an oxide, and examples of the oxide include a YSZ substrate, an MgAl ₂ O ₄ substrate, a ZnO substrate, an MgO substrate, an SrTIO ₃ substrate, an Al ₂ O ₃ substrate, and a quartz substrate. Glass substrate, β-type gallium oxide substrate, barium titanate substrate, strontium titanate substrate, cobalt oxide substrate, copper oxide substrate, chromium oxide substrate, iron oxide substrate, Gd ₃ Ga ₅ O ₁₂ substrate, potassium tantalate substrate, aluminic acid Lantern Substrate, Lantern Strontium Aluminate Substrate, Lantern Strontium Galate Substrate, Lithium Niobate Substrate, Lithium Tantalate Substrate, Lantern Strontium Aluminum Tantrate, Manganese Oxide Substrate, Neodium Garade Substrate, Nickel Oxide Substrate, Scandium Magnesium Aluminate Substrate, Oxidation Strontium, strontium titanate substrate, tin oxide substrate, tellurium oxide substrate, titanium oxide substrate, YAG substrate, ittrium / aluminate substrate, lithium / aluminate substrate, lithium gallate substrate, LAST substrate, neodymium gallate substrate, ittrium orthobana A date substrate and the like can be mentioned.

In the present invention, an annealing treatment may be performed after the film forming step. The annealing treatment temperature is not particularly limited as long as the object of the present invention is not impaired, and is usually 300 ° C. to 650 ° C., preferably 350 ° C. to 550 ° C. The annealing treatment time is usually 1 minute to 48 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 12 hours. The annealing treatment may be carried out in any atmosphere as long as the object of the present invention is not impaired, but it is preferably in a non-oxygen atmosphere, and more preferably in a nitrogen atmosphere.

Further, in the present invention, the crystalline oxide semiconductor film may be provided directly on the substrate, or the crystalline oxide semiconductor may be provided through another layer such as a buffer layer (buffer layer) or a stress relaxation layer. A film may be provided. The means for forming each layer is not particularly limited and may be a known means, but in the present invention, the mist CVD method is preferable.

In the present invention, the crystalline oxide semiconductor film may be used as a semiconductor layer after using a known means such as peeling from the substrate or the like, or may be used as it is as a semiconductor layer.

The semiconductor device of the present invention includes at least a Schottky electrode containing a metal oxide and a semiconductor layer containing indium, gallium or aluminum.

The Schottky electrode is not particularly limited as long as it contains a metal oxide containing one or more metals belonging to any of Group 6 to Group 9 of the periodic table. As one or more kinds of metals belonging to any of the 6th to 9th groups of the periodic table, the metal of the 6th group of the periodic table, the metal of the 7th group of the periodic table, and the 8th group of the periodic table. Metals, metals of Group 9 of the Periodic Table, and alloys thereof. Examples of the metal of Group 6 of the periodic table include chromium (Cr), molybdenum (Mo), tungsten (W) and an alloy thereof. In the present invention, the metal oxide is tungsten or tungsten. preferably comprises an alloy that contains, tungsten or _M X WO ₃ (where, M element, select Cs, Rb, K, Tl, Ba, in, Li, Sn, Ca, Sr, from among the Na More preferably, it is a tungsten-containing alloy represented by one or more kinds of elements, W is tungsten, O is oxygen, and 0.001 ≦ X ≦ 1), and the tungsten-containing alloy is most preferable. Examples of the metal of Group 7 of the periodic table include manganese (Mn), technetium (Tc), rhenium (Re) and alloys thereof. In the present invention, the oxide semiconductor having a corundum structure is used. It is preferable that the metal oxide contains rhenium or an alloy containing rhenium, and more preferably _{ReO 2} or ReO _{3 , because an excellent one can be obtained due to the adhesion of ReO 3.} Is most preferable. Examples of the metal of Group 8 of the periodic table include iron (Fe), ruthenium (Ru), osmium (Os) and alloys thereof. In the present invention, the metal oxide is ruthenium or It preferably contains an alloy containing ruthenium, more preferably _{RuO 2.} Examples of the metal of Group 9 of the periodic table include cobalt (Co), rhodium (Rh), iridium (Ir) and alloys thereof. In the present invention, the metal oxide is cobalt or It preferably contains iridium or an alloy containing cobalt or iridium, more preferably CoO ₃ or IrO ₂ .

Further, the Schottky electrode may be a single metal layer or may include two or more metal films. The means for laminating the metal layer is not particularly limited, and examples thereof include known means such as a vacuum deposition method, a sputtering method, and a mist CVD method. In the present invention, it is preferable to form a metal layer of a Schottky electrode by a mist CVD method. The formation by the mist CVD method can be performed in the same manner as the formation of the semiconductor layer described above. Further, in the present invention, the metal oxide preferably contains one or more metals selected from tungsten, rhenium, ruthenium, cobalt and iridium, and more preferably rhenium. More specifically, tungsten oxide, rhenium oxide, ruthenium oxide, cobalt oxide and iridium oxide are preferable, and rhenium oxide is more preferable. By using such a preferable metal oxide, the semiconductor characteristics (for example, durability, dielectric breakdown voltage, breakdown voltage, on-resistance, stability, etc.) of the semiconductor having a corundum structure can be made better. The shut key characteristics can also be exhibited well.

Further, the semiconductor device of the present invention usually includes an ohmic electrode. The ohmic electrode preferably contains a metal of Group 4 or Group 11 of the Periodic Table. Suitable metal of Group 4 or Group 11 of the periodic table used for the ohmic electrode may be the same as the metal contained in the Schottky electrode. Further, the ohmic electrode may be a single metal layer or may include two or more metal layers. The means for laminating the metal layer is not particularly limited, and examples thereof include known means such as a vacuum deposition method and a sputtering method. Further, the metal constituting the ohmic electrode may be an alloy. In the present invention, the ohmic electrode preferably contains Ti and / and Au, more preferably Ti and Au.

The semiconductor device is particularly useful for power devices. Examples of the semiconductor device include a semiconductor laser, a diode, a transistor, and the like. Among them, a diode is preferable, and a Schottky barrier diode is more preferable.

(SBD)
FIG. 1 shows a suitable example of the Schottky barrier diode (SBD) according to the present invention. The SBD of FIG. 1 includes an n-type semiconductor layer 101a, an n + type semiconductor layer 101b, a Schottky electrode 105a, and an ohmic electrode 105b.
The Schottky electrode and the ohmic electrode can be formed by a known means such as a vacuum vapor deposition method, a sputtering method, and a mist CVD method. More specifically, for example, when a Schottky electrode is formed, it can be performed by forming a metal layer by a vacuum vapor deposition method, a sputtering method, a mist CVD method, or the like, and then performing patterning using a photolithography method.

FIG. 3 shows an example of a preferred Schottky electrode used in the present invention. The Schottky electrode 50a is composed of an Al layer 51, a Re layer 52, and a ReO ₃ layer 53. A metal layer such as Ti or Cr (for example, a film thickness of 0.1 nm to 1 μm) may be provided between the Al layer 51 and the Re layer 52. The film thickness of the metal film of each layer is not particularly limited, but the Al layer 51 is preferably 10 nm to 50 μm, more preferably 300 nm to 30 μm, and most preferably 1 μm to 20 μm. The metal (for example, Re etc.) layer of Group 6 to 9 of the periodic table such as the Re layer 52 is preferably 1 nm to 10 μm, more preferably 1 nm to 5 μm, and most preferably 5 nm to 50 nm or 0.5 μm to 5 μm. The metal oxide layer of the metal of Group 6 to 9 of the periodic table such as ReO ₃ layer 53 (for example, Re etc.) is preferably, for example, 1 nm to 10 μm, more preferably 1 nm to 5 μm, and 5 nm to 50 nm or 0. Most preferably, it is 5.5 μm to 5 μm.

FIG. 4 shows the main parts of a preferred Schottky electrode used in the present invention. The main portion 50b of the Schottky electrode is composed of a Re layer 54 and a ReO ₃ layer 55. The film thickness of the metal film of each layer is not particularly limited, but in the case of the Re layer 54, 1 nm to 10 μm is preferable, 1 nm to 5 μm is more preferable, and 5 nm to 50 nm or 0.5 μm to 5 μm is most preferable. In _{the case of the ReO 3} layer 55, 1 nm to 10 μm is preferable, 1 nm to 5 μm is more preferable, and 5 nm to 50 nm or 0.5 μm to 5 μm is most preferable. Normally, a metal oxide layer such as _{ReO 3} layer 55 is provided on the semiconductor layer side.
In the present invention, it is preferable to use the metal layer together with the metal oxide layer because the semiconductor characteristics are better, and the metal layer used together with the metal oxide layer is selected from copper, aluminum, gold and nickel. It is more preferable to include one kind or two or more kinds.

When a reverse bias is applied to the SBD of FIG. 1, the depletion layer (not shown) spreads in the n-type semiconductor layer 101a, resulting in a high withstand voltage SBD. Further, when a forward bias is applied, electrons flow from the ohmic electrode 105b to the Schottky electrode 105a. The SBD using the laminated structure in this way is excellent for high withstand voltage and large current, has good Schottky characteristics, has a high switching speed, and is also excellent in withstand voltage and reliability.

FIG. 2 shows another suitable example of the Schottky barrier diode (SBD) according to the present invention. The SBD of FIG. 2 further includes an insulator layer 104 in addition to the configuration of the SBD of FIG. More specifically, it includes an n-type semiconductor layer 101a, an n + type semiconductor layer 101b, a Schottky electrode 105a, an ohmic electrode 105b, and an insulator layer 104.

Examples of the material of the insulator layer 104 include GaO, AlGaO, InAlGaO, AlInZnGaO ₄ , AlN, Hf ₂ O ₃ , SiN, SiON, Al ₂ O ₃ , MgO, GdO, SiO ₂ or Si ₃ N _4. However, in the present invention, it is preferable that it has a corundum structure. By using an insulator having a corundum structure for the insulator layer, the function of semiconductor characteristics at the interface can be satisfactorily exhibited. The insulator layer 104 is provided between the n-type semiconductor layer 101 and the Schottky electrode 105a. The insulator layer can be formed by a known means such as a sputtering method, a vacuum vapor deposition method, or a CVD method.
Other configurations and the like are the same as in the case of the SBD of FIG. 1 above.
The SBD of FIG. 2 is further excellent in insulation characteristics and has higher current controllability than the SBD of FIG.

(MESFET)
FIG. 7 shows an example of a metal semiconductor field effect transistor (MESFET) used in the present invention. The MESFET of FIG. 7 includes an n-type semiconductor layer 111a, an n + type semiconductor layer 111b, a buffer layer (buffer layer) 118, a semi-insulator layer 114, a gate electrode 115a, a source electrode 115b, and a drain electrode 115c.

The gate electrode preferably has Schottky characteristics, and in the present invention, the Schottky electrode can be preferably used for such a gate electrode. Further, the drain electrode preferably has ohmic characteristics, and the ohmic electrode can be suitably used as the drain electrode.

In the MESFET of FIG. 7, since a good depletion layer is formed under the gate electrode, the current flowing from the drain electrode to the source electrode can be efficiently controlled.

The semiconductor device is used, for example, in a system using a power supply device or the like. The power supply device can be manufactured by connecting the semiconductor device to a wiring pattern or the like by using a known means. FIG. 8 shows an example of a power supply system. In FIG. 8, a power supply system is configured by using the plurality of power supply devices and control circuits. As shown in FIG. 9, the power supply system can be used in a system device in combination with an electronic circuit. An example of the power supply circuit diagram of the power supply device is shown in FIG. FIG. 10 shows a power supply circuit of a power supply device including a power circuit and a control circuit. An inverter (composed of MOSFETs A to D) switches a DC voltage at a high frequency, converts it to AC, and then insulates and transforms it with a transformer. After rectifying with a rectifying MOSFET (A to B'), it is smoothed with a DCL (smoothing coils L1 and L2) and a capacitor, and a DC voltage is output. At this time, the output voltage is compared with the reference voltage by the voltage comparator, and the inverter and the rectifying MOSFET are controlled by the PWM control circuit so as to obtain the desired output voltage.

1. 1. Formation of n + type semiconductor layer 1-1. Film formation device The mist CVD device 1 used in this embodiment will be described with reference to FIG. The mist CVD apparatus 1 includes a carrier gas source 2a for supplying a carrier gas, a flow control valve 3a for adjusting the flow rate of the carrier gas sent out from the carrier gas source 2a, and a carrier gas (diluted) for supplying the carrier gas (diluted). A diluting) source 2b, a flow control valve 3b for adjusting the flow rate of the carrier gas (diluting) sent out from the carrier gas (diluting) source 2b, a mist generation source 4 containing the raw material solution 4a, and water 5a. In the container 5 to be put in, the ultrasonic vibrator 6 attached to the bottom surface of the container 5, the film forming chamber 7, the supply pipe 9 connecting the mist generation source 4 to the film forming chamber 7, and the film forming chamber 7. It includes an installed hot plate 8 and an exhaust port 11 for discharging mist, droplets, and exhaust gas after a thermal reaction. The substrate 10 is installed on the hot plate 8.

1-2. Preparation of raw material solution Tin bromide was mixed with a 0.1 M gallium bromide aqueous solution, and the aqueous solution was adjusted so that the atomic ratio of tin to gallium was 1: 0.08. A ratio of 10% was contained, and this was used as a raw material solution.

1-3. Preparation for film formation 1-2. The raw material solution 4a obtained in 1 above was housed in the mist source 4. Next, as the substrate 10, a sapphire substrate was placed on the hot plate 8 and the hot plate 8 was operated to raise the temperature in the film forming chamber 7 to 470 ° C. Next, the flow rate control valves 3a and 3b are opened, the carrier gas is supplied into the film forming chamber 7 from the carrier gas supply means 2a and 2b which are the carrier gas sources, and the atmosphere of the film forming chamber 7 is sufficiently filled with the carrier gas. After the replacement, the flow rate of the carrier gas was adjusted to 5.0 L / min, and the flow rate of the carrier gas (diluted) was adjusted to 0.5 L / min. Nitrogen was used as the carrier gas.

1-4. Formation of Crystalline Oxide Semiconductor Film Next, the ultrasonic transducer 6 is vibrated at 2.4 MHz, and the vibration is propagated to the raw material solution 4a through water 5a to atomize the raw material solution 4a and mist 4b. Was generated. This mist 4b is introduced into the film forming chamber 7 by the carrier gas through the supply pipe 9, and the mist thermally reacts in the film forming chamber 7 at 470 ° C. under atmospheric pressure to cause the substrate 10 to react. A film was formed on top. The film thickness was 7.5 μm, and the film formation time was 180 minutes.

1-5. Evaluation Using the XRD diffractometer, the above 1-4. When the phase of the membrane obtained in the above was identified, the obtained membrane was α-Ga ₂ O ₃ .

2. Formation of n-type semiconductor layer 2-1. Film formation device The mist CVD device 19 used in the examples will be described with reference to FIG. The mist CVD apparatus 19 includes a susceptor 21 on which the substrate 20 is placed, a carrier gas supply means 22a for supplying the carrier gas, and a flow control valve 23a for adjusting the flow rate of the carrier gas sent out from the carrier gas supply means 22a. , A carrier gas (diluted) supply means 22b for supplying a carrier gas (diluted), a flow control valve 23b for adjusting the flow rate of the carrier gas sent out from the carrier gas (diluted) supply means 22b, and a raw material solution 24a are accommodated. A supply pipe 27 composed of a mist generation source 24, a container 25 in which water 25a is placed, an ultrasonic vibrator 26 attached to the bottom surface of the container 25, and a quartz pipe having an inner diameter of 40 mm, and a peripheral portion of the supply pipe 27. It is equipped with a heater 28 installed in. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal plane. By making both the supply tube 27 and the susceptor 21 serving as the film forming chamber from quartz, it is possible to prevent impurities derived from the apparatus from being mixed into the film formed on the substrate 20.

2-2. Preparation of Raw Material Solution A 0.1 M gallium bromide aqueous solution contained 20% by volume of hydrofluoric acid bromide, and this was used as a raw material solution.

2-3. Preparation for film formation 1-2. The raw material solution 24a obtained in 1) was housed in the mist generation source 24. Next, as the substrate 20, an n + type semiconductor film peeled from the sapphire substrate was placed on the susceptor 21, and the heater 28 was operated to raise the temperature inside the film forming chamber 27 to 510 ° C. Next, the flow control valves 23a and 23b are opened to supply the carrier gas into the film forming chamber 27 from the carrier gas supplying means 22a and 22b which are the carrier gas sources, and the atmosphere of the film forming chamber 27 is sufficiently filled with the carrier gas. After the replacement, the flow rate of the carrier gas was adjusted to 5 L / min, and the flow rate of the carrier gas (diluted) was adjusted to 0.5 L / min. Oxygen was used as the carrier gas.

2-4. Semiconductor film formation Next, the ultrasonic transducer 26 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 24a through water 25a to atomize the raw material solution 24a to generate mist. This mist was introduced into the film forming chamber 27 by the carrier gas, and the mist reacted in the film forming chamber 27 at 510 ° C. under atmospheric pressure to form a semiconductor film on the substrate 20. The film thickness was 3.6 μm, and the film formation time was 120 minutes.

2-5. Evaluation Using the XRD diffractometer, the above 2-4. When the phase of the membrane obtained in the above was identified, the obtained membrane was α-Ga ₂ O ₃ .

3. 3. Formation of Schottky Electrode As shown in FIG. 3, the ReO ₃ layer was laminated on the n-type semiconductor layer by the mist CVD method, and the Re layer and the Al layer were respectively laminated by electron beam deposition. The thickness of the ReO ₃ layer was 0.5 μm, the thickness of the Re layer was 0.08 μm, and the thickness of the Al layer was 5 μm.

4. Formation of Ohmic Electrode A Ti layer and an Au layer were laminated on an n + type semiconductor layer by electron beam deposition, respectively. The thickness of the Ti layer was 0.05 μm, and the thickness of the Au layer was 0.3 μm.

5. IV measurement The semiconductor device obtained as described above was subjected to IV measurement, and it was confirmed that the Schottky characteristics were good. Further, the withstand voltage was examined and found to be about 870V. From these results, it can be seen that the product of Example 1 is excellent in semiconductor characteristics and Schottky characteristics.

(Example 2)
A semiconductor device was obtained in the same manner as in Example 1 except that the Ti layer was used instead of the Re layer. The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Example 3)
A semiconductor device was obtained in the same manner as in Example 1 except that a Cr layer was used instead of the Re layer and a Cu-doped Cs _0.33 WO _{3 layer was used instead of the ReO 3 layer.} The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Example 4)
A semiconductor device was obtained in the same manner as in Example 1 except that the Ir layer was used instead of the Re layer and the IrO _{2 layer was used instead of the ReO 3 layer.} The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Example 5)
A semiconductor device was obtained in the same manner as in Example 1 except that the Co layer was used instead of the Re layer and the CoO _{3 layer was used instead of the ReO 3 layer.} The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Example 6)
A semiconductor device was obtained in the same manner as in Example 1 except that the Re layer was not used. The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Example 7)
A semiconductor device was obtained in the same manner as in Example 1 except that the Ti layer was used instead of the Re layer and the RuO _{3 layer was used instead of the ReO 3 layer.} The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Example 8)
A semiconductor device was obtained in the same manner as in Example 1 except that a Cu layer was used instead of the Al layer. The obtained semiconductor device exhibited good semiconductor characteristics and Schottky characteristics as in Example 1.

(Comparative Example 1)
For reference, FIG. 11 shows the IV measurement results when Pt is used for the Schottky electrode. As is clear from FIG. 11, _{it can be seen that when the semiconductor layer of α-Ga 2} O ₃ is used, the semiconductor characteristics and the Schottky characteristics are significantly impaired.

(Comparative Example 2)
When an ITO film was used for the Schottky electrode, the resistance of the ITO film was very poor. The ITO film was formed by sputtering.

As described above, it can be seen that the present invention is excellent in semiconductor characteristics and Schottky characteristics.

The laminated structure of the present invention can be used in all fields such as semiconductors (for example, compound semiconductor electronic devices, etc.), electronic parts / electrical equipment parts, optical / electrophotographic related devices, industrial parts, etc., but is excellent in semiconductor characteristics. Therefore, it is particularly useful for semiconductor devices.

1 Mist CVD equipment 2a Carrier gas source 2b Carrier gas (dilution) source 3a Flow control valve 3b Flow control valve 4 Mist generation source 4a Raw material solution 4b Mist 5 Container 5a Water 6 Ultrasonic transducer 7 Formation chamber 8 Hot plate 9 Supply Tube 10 Board 11 Exhaust port 19 Mist CVD device 20 Board 21 Suceptor 22a Carrier gas supply means 22b Carrier gas (dilution) supply means 23a Flow control valve 23b Flow control valve 24 Mist source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic vibration Child 27 Supply pipe 28 Heater 29 Exhaust port 50a Shot key electrode (3 layers)
50b Schottky electrode (2 layers)
51 Al layer 52 Re layer 53 ReO ₃ layer 54 Re layer 55 ReO ₃ layer 101a n-type semiconductor layer 101b n + type semiconductor layer 104 Insulation layer 105a Shotkey electrode 105b Ohmic electrode 111a n-type semiconductor layer 111b n + type semiconductor layer 114 Semi-insulator layer 115a Gate electrode 115b Source electrode 115c Drain electrode 118 Buffer layer

Claims (13)

A semiconductor device including at least a Schottky electrode containing a metal oxide and a semiconductor layer containing indium, gallium, or aluminum.
Wherein the metal oxide is a metal oxide containing one or more metals belonging to any of groups 6 to Group 9 of the periodic table,
The semiconductor layer is composed of an n + type semiconductor layer and an n− type semiconductor layer provided on the n + type semiconductor layer.
A semiconductor device characterized in that the Schottky electrode is provided on the n-type semiconductor layer. The semiconductor device according to claim 1, wherein the semiconductor layer comprises a crystalline oxide semiconductor film having a corundum structure as a constituent material. The semiconductor device according to claim 1 or 2, wherein the semiconductor layer contains indium or gallium. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains a metal of Group 6 of the periodic table. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains tungsten. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains a metal of Group 7 of the periodic table. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains rhenium. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains a metal of Group 8 of the periodic table. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains ruthenium. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains a metal of Group 9 of the periodic table. The semiconductor device according to any one of claims 1 to 3, wherein the metal oxide contains cobalt or iridium. The semiconductor device according to any one of claims 1 to 11, which is a Schottky barrier diode. A semiconductor system including a semiconductor device, wherein the semiconductor device is the semiconductor device according to any one of claims 1 to 12.

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