JP6904517B2 - Crystalline oxide semiconductor film and its manufacturing method - Google Patents

Description

The present invention relates to a crystalline oxide semiconductor film useful for a semiconductor device and a method for producing the same.

Conventionally, there is a problem that cracks and crystal defects occur when crystals are grown on dissimilar substrates. To solve this problem, matching the lattice constants and the coefficient of thermal expansion of the substrate and the film has been studied. Further, when inconsistency occurs, a film forming method such as ELO is also being studied.

Patent Document 1 describes a method in which a buffer layer is formed on a dissimilar substrate and a zinc oxide-based semiconductor layer is crystal-grown on the buffer layer. Patent Document 2 describes that a nanodot mask is formed on a dissimilar substrate, and then a single crystal semiconductor material layer is formed. Non-Patent Document 1 describes a method of crystal growing GaN on sapphire via a nanocolumn of GaN. Non-Patent Document 2 describes a method of crystal growing GaN on Si (111) using a periodic SiN intermediate layer to reduce defects such as pits.

However, with any of these techniques, it is possible to obtain a high-quality epitaxial film due to poor film formation speed, cracks, dislocations, warpage, etc. on the substrate, and dislocations, cracks, etc. on the epitaxial film. It was difficult, and there were problems in increasing the diameter of the substrate and increasing the thickness of the epitaxial film.

Further, as a next-generation switching element capable of achieving high withstand voltage, low loss, and high heat resistance, _{a semiconductor device using gallium oxide (Ga 2} O ₃ ) having a large bandgap is attracting attention, and a semiconductor device for power such as an inverter is attracting attention. It is expected to be applied to. Moreover, it is expected to be applied as a light receiving / receiving device for LEDs, sensors, etc. due to its wide band gap. According to Non-Patent Document 2, the gallium oxide can control the bandgap by mixing indium and aluminum individually or in combination, and constitutes an extremely attractive material system as an InAlGaO-based semiconductor. .. Here, the InAlGaO based semiconductor _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), gallium oxide It can be overlooked as the same material system included.

When forming an InAlGaO-based semiconductor film having a corundum structure, crystals usually grow on dissimilar substrates, which causes problems such as cracks in the epitaxial film. So far, a method for suppressing cracks and crystal defects of an InAlGaO-based semiconductor film has been studied, and in Patent Document 3, an α-Ga ₂ O ₃ film having few cracks is obtained by a film forming method using ELO technology. Is forming a film. Further, in Patent Document 4, a void is provided at the time of forming an epitaxial film to form an α-Ga ₂ O ₃ film having reduced cracks. However, with these methods, it is difficult to obtain a crystalline oxide semiconductor film that substantially does not contain cracks over a large area (300 μm square or more) of the film surface, and particularly when a thick film of 3 μm or more is formed. It was not possible to obtain a crystalline oxide semiconductor film in which cracks were sufficiently reduced. Therefore, a crystalline oxide semiconductor film that does not substantially contain cracks over an area of 300 μm square or more and a method for producing the same have been long-awaited.
Both Patent Documents 3 and 4 are publications relating to patent applications by the present applicant.

Japanese Unexamined Patent Publication No. 2010-2326223 Special Table 2010-516599 Japanese Unexamined Patent Publication No. 2016-100592 Japanese Unexamined Patent Publication No. 2016-100593

K. Y. Zang., Et al., "Defect reduction by periodic SiNx propagates in gallium nitride grown on Si (111)", Journal of Applied Physics 101, 093502 (2007) Kentaro Kaneko, "Growth and Physical Properties of Corundum Structure Gallium Oxide Mixed Crystal Thin Film", Doctoral Dissertation, Kyoto University, March 2013

An object of the present invention is to provide a crystalline oxide semiconductor film substantially free of cracks and a method for producing the same over an area of 300 μm square or more on the film surface.

As a result of diligent studies to achieve the above object, the present inventors have made that two or more oxide layers including at least the first layer and the second layer are 300 μm square or more directly or via another layer. When a crystalline oxide semiconductor film is formed on the oxide layer using a base substrate formed on the surface over an area, surprisingly, cracks are substantially formed over an area of 300 μm square or more on the film surface. We have found that a crystalline oxide semiconductor film that does not contain the film can be obtained, and found that this crystalline oxide semiconductor film 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 crystalline oxide semiconductor film containing a crystalline oxide semiconductor having a corundum structure as a main component, characterized in that cracks are substantially not contained over an area of 300 μm square or more on the film surface. Sex oxide semiconductor film.
[2] The crystalline oxide semiconductor film according to the above [1], which has a film thickness of 3 μm or more.
[3] The crystalline oxide semiconductor film according to the above [1] or [2], wherein the crystalline oxide semiconductor contains indium, gallium or aluminum.
[4] The crystalline oxide semiconductor film according to any one of the above [1] to [3], wherein the crystalline oxide semiconductor contains gallium.
[5] The crystalline oxide semiconductor film according to any one of [1] to [4] above, further containing a dopant.
[6] The crystalline oxide semiconductor film according to any one of [1] to [5] above, wherein the film thickness is 5 μm or more.
[7] The crystalline oxide semiconductor film according to any one of [1] to [6] above, wherein cracks are substantially not contained over an area of 400 μm square or more on the film surface.
[8] On a base substrate having a corundum structure, two or more oxide layers including at least a first layer and a second layer directly on the base substrate or via another layer, and on the oxide layer. The crystalline oxide semiconductor film according to any one of [1] to [7] is provided, and the main component of the first layer is a crystalline oxide having a corundum structure, which is the main component of the second layer. A laminated structure characterized in that the components are different in composition ratio from the main components of the first layer.
[9] A semiconductor device including at least the crystalline oxide semiconductor film according to any one of [1] to [7] or the laminated structure according to [8] and an electrode.
[10] A system including the semiconductor device according to the above [9].
[11] Using a base substrate in which two or more oxide layers including at least the first layer and the second layer are formed on the surface over an area of 300 μm square or more directly or via other layers. A method for producing a crystalline oxide semiconductor film for forming a crystalline oxide semiconductor film on the oxide layer, wherein the base substrate has a corundum structure and the main component of the first layer is. , A crystalline oxide having a corundum structure, wherein the main component of the second layer has a composition ratio different from that of the main component of the first layer. Method.
[12] The production method according to the above [11], wherein the crystalline oxide semiconductor film is formed by a mist CVD method.
[13] The production method according to the above [11] or [12], wherein the main component of the base substrate is a crystalline oxide different from the main component of the first layer.
[14] The production method according to any one of [11] to [13] above, wherein the main component of the crystalline oxide semiconductor film is a crystalline oxide semiconductor different from the main component of the first layer.

The crystalline oxide semiconductor film of the present invention is substantially free of cracks over an area of 300 μm square or more on the film surface. Further, the production method of the present invention can produce such a crystalline oxide semiconductor film in an industrially advantageous manner.

It is a schematic block diagram of the film forming apparatus (mist CVD apparatus) used in an Example. It is a figure which shows the film surface observed by the optical microscope in Example 1. FIG. It is a figure which shows the film surface observed by the optical microscope in the comparative example 1. FIG. It is a figure which shows the film surface observed by the optical microscope in the comparative example 2. It is a figure which shows typically a preferable example of a Schottky barrier diode (SBD). It is a figure which shows typically a preferable example of a high electron mobility transistor (HEMT). It is a figure which shows typically a preferable example of a metal oxide film semiconductor field effect transistor (MOSFET). It is a figure which shows typically a preferable example of a junction field effect transistor (JFET). It is a figure which shows typically a preferable example of an insulated gate type bipolar transistor (IGBT). It is a figure which shows typically a preferable example of a light emitting element (LED). It is a figure which shows typically a preferable example of a light emitting element (LED). 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 typically the base substrate which used in Example 1 and has the oxide layer formed on the surface. It is a figure which shows typically the base substrate which used in the comparative example 1 and has the oxide layer formed on the surface.

Hereinafter, preferred embodiments of the present invention will be described.

The crystalline oxide semiconductor film of the present invention is a crystalline oxide semiconductor film containing a crystalline oxide having a corundum structure as a main component, and substantially contains cracks over an area of 300 μm square or more on the film surface. It is characterized by the absence. In the present invention, it is more preferable that the crystalline oxide semiconductor film substantially does not contain cracks over an area of 400 μm square or more on the film surface. As used herein, the term "crack" usually refers to a linear or substantially circular defect site that occurs on the surface or in the crystalline oxide semiconductor film, and includes cracks, openings, and cracks. Further, the "crack" particularly preferably means a defect site of a linear crystal having a width of 0.2 μm or more and a length of 50 μm or more, and also includes a crystal defect due to dislocation. More preferably, the defect site is a defect site of a linear crystal having a width of 1.0 μm or more and a length of 50 μm or more. "Substantially free of cracks" means that the presence of the cracks cannot be confirmed by observing the film surface with an optical microscope, and in particular, it means that there are no cracks that can be confirmed by observing the film surface with an optical microscope. .. In the present invention, the crystalline oxide semiconductor preferably contains indium, gallium or aluminum, more preferably contains an InAlGaO-based semiconductor, and most preferably contains at least gallium. 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, but in the present invention, it is preferably 3 μm or more, and 5 μm or more. The above is more preferable. The shape of the crystalline oxide semiconductor film is not particularly limited, and whether it is a square shape (including a square shape or a rectangular shape) or a circular shape (including a semicircular shape), it has a polygonal shape. It may be. The surface area of the crystalline oxide semiconductor film is not particularly limited as long as it is 300 μm square or more, but in the present invention, it is preferably 400 μm square or more, more preferably 5 mm square or more, and having a diameter of 50 mm or more. Is most preferable. The crystalline oxide semiconductor film may be a single crystal film or a polycrystalline film, but is preferably a single crystal film.

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 content of the dopant 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 of the present invention, for example, two or more oxide layers including at least a first layer and a second layer are surfaced over an area of 300 μm square or more directly or via another layer. It can be obtained by forming the crystalline oxide semiconductor film on the base substrate using the base substrate formed in. Here, the main component of the first layer is a crystalline oxide having a corundum structure, and the main component of the second layer is a crystalline oxide having a composition ratio different from that of the main component of the first layer. .. The "main component of the first layer" is preferably 50% or more, more preferably 70% or more, more preferably 70% or more of the crystalline oxide in terms of atomic ratio with respect to all the components of the first layer. Means that it is contained in an amount of 90% or more, and may be 100%. Further, the "main component of the second layer" means that the crystalline oxide is preferably 50% or more, more preferably 70% or more, more preferably 70% or more, based on the atomic ratio of all the components of the second layer. Means that it is contained in an amount of 90% or more, and may be 100%. In addition to the crystalline oxide semiconductor film, the laminated structure thus obtained is also included in the present invention, and as one of the preferred embodiments, a base substrate and a base substrate and a layer directly or another layer on the substrate substrate. It is provided with two or more oxide layers including at least a first layer and a second layer, and the crystalline oxide semiconductor film on the oxide layer, and the main component of the first layer is , A laminated structure which is a crystalline oxide having a corundum structure and in which the main component of the second layer has a composition ratio different from that of the main component of the first layer.

The base substrate has a plate-like shape in which two or more oxide layers including at least a first layer and a second layer are formed on the surface over an area of 300 μm square or more directly or via another layer. The present invention is not particularly limited as long as it serves as a support for the crystalline oxide semiconductor film. The base substrate may be an insulator substrate, a semiconductor substrate, or a conductive substrate, but it is preferable that the base substrate is an insulator substrate. Examples of the base substrate include a substrate containing a substrate material having a corundum structure as a main component. 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 it means that it 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. As a base substrate containing the substrate material having a corundum structure as a main component, a sapphire substrate (preferably a c-plane sapphire substrate), an α-type gallium oxide substrate, and the like can be mentioned as suitable examples. The base substrate is preferably a sapphire substrate, and more preferably a c-plane sapphire substrate.

On the base substrate, two or more oxide layers including at least a first layer and a second layer are formed on the surface over an area of 300 μm square or more directly or via another layer. It is also preferable that the surface is formed over an area of 400 μm square or more. Such a preferred substrate is shown in FIG. The base substrate of FIG. 15 has a first layer and a second layer formed on the surface thereof. Both the first layer and the second layer are oxide layers, and a film-forming means such as a mist CVD method or a mist epitaxy method may be used to form the first layer and the second layer. It is possible. Further, the main component of the first layer constituting the oxide layer is a crystalline oxide having a corundum structure, and the main component of the second layer has a composition ratio different from that of the main component of the first layer. It is a crystalline oxide. In the present invention, the main component of the first layer preferably contains gallium or aluminum, and more preferably gallium and aluminum. When the main components of the first layer contain gallium and aluminum, the atomic ratio of aluminum to gallium in the main components excluding oxygen of the first layer is preferably 1 to 20%, and the second layer. It is also preferable that it is larger than the atomic ratio of aluminum to gallium in the main component excluding oxygen of the layer.

Further, in the present invention, the main component of the base substrate is preferably a crystalline oxide different from the main component of the first layer, and the main component of the crystalline oxide semiconductor film is the first layer. It is also preferable that the crystalline oxide semiconductor is different from the main component of.

The means for forming the oxide layer is not particularly limited and may be a known means as long as the object of the present invention is not impaired. Examples of the means for forming the oxide layer include a CVD method, a MOCVD method, a MOVPE method, a mist CVD method, a mist epitaxy method, an MBE method, an HVPE method, and a pulse growth method. In the present invention, the means for forming the oxide layer is preferably a MOCVD method, an MBE method, an HVPE method, a mist CVD method or a mist epitaxy method, and more preferably a mist CVD method or a mist epitaxy method. preferable.

Hereinafter, as a preferable example of the means for forming the oxide layer, two or more oxide layers including at least the first layer and the second layer are used as a base by using a mist CVD method or a mist epitaxy method. The present invention will be described in more detail with reference to an example formed on the substrate.

In the mist CVD method or mist epitaxy method, the first and second raw material solutions are atomized (atomization step I), respectively, and the first and second mists produced are used as the first and second carrier gases. Each of them is used to transfer to the base substrate (transport step I), and then the first and second mists are thermally reacted to form the first and second layers on the base substrate, respectively. (Film formation step I).

(Atomization step I)
In the atomization step I, the first and second raw material solutions are atomized, respectively. The first and second atomizations may be performed simultaneously or separately, but in the present invention, they are preferably performed separately. The atomizing means is not particularly limited as long as the first and second raw material solutions can be atomized, and may be known means, but in the present invention, the atomizing means using ultrasonic waves is preferable. The mist obtained by using ultrasonic waves is preferable because it has a zero initial velocity and floats in the air. For example, a mist that can float in a space and be transported as a gas instead of being sprayed like a spray. Therefore, it is very suitable because it is not damaged by collision energy. The size of the mist droplets is not particularly limited and may be about several mm, but is preferably 50 μm or less, and more preferably 100 nm to 10 μm.

(First and second raw material solutions)
The first and second raw material solutions are not particularly limited as long as they are solutions in which the oxide layer can be obtained by a mist CVD method or a mist epitaxy method. Examples of the first and second raw material solutions include aqueous solutions of metal organic metal complexes (for example, acetylacetonate complex, etc.) and halides (for example, fluoride, chloride, bromide, iodide, etc.). The metal may be any metal that can form an oxide, and examples of such a metal include gallium, indium, aluminum, and iron. In the present invention, the metal preferably contains at least gallium or aluminum, more preferably at least gallium and aluminum. The content of the metal in the first and second raw material solutions is not particularly limited as long as the object of the present invention is not impaired, but is preferably 0.001 mol% to 50 mol%, more preferably 0.01. It is mol% to 50 mol%. When the first and second raw material solutions contain gallium and aluminum, it is preferable that the second raw material solution contains more gallium than the first raw material solution.

In addition, the first and second raw material solutions may further contain other additives such as acids and bases. In the present invention, it is preferable that the raw material solution contains an acid, and examples of such a preferable acid include hydrochloric acid, hydrobromic acid, hydroiodic acid and the like.

The solvent of the first and second raw material solutions is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solution of an inorganic solvent and an organic solvent. There may be. In the present invention, the solvent preferably contains water, and it is also preferable that the solvent is a mixed solvent of water and acid. More specific examples of the water include pure water, ultrapure water, tap water, well water, mineral spring water, mineral water, hot spring water, spring water, fresh water, seawater, and the like. Ultrapure water is preferred. More specifically, the acid includes organic acids such as acetic acid, propionic acid, and butanoic acid; boron trifluoride, boron trifluoride etherate, boron trichloride, boron tribromide, and trifluoroacetic acid. , Trifluoromethanesulfonic acid, p-toluenesulfonic acid and the like, but in the present invention, acetic acid is preferable.

(Transport step I)
In the transfer step I, the first and second carrier gases are used to transfer the first and second mists to the base substrate, respectively. The types of the first and second carrier gases are not particularly limited as long as the object of the present invention is not impaired, and for example, reduction of an inert gas such as oxygen, ozone, nitrogen or argon, or reduction of hydrogen gas or forming gas. Examples thereof include gas, but in the present invention, it is preferable to use oxygen as the first and second carrier gas. Further, the types of the first and second carrier gases may be one type, but may be two or more types, such as a diluted gas having a changed carrier gas concentration (for example, a 10-fold diluted gas, etc.). May be further used. Further, the first and second carrier gas supply points may be not only one place but also two or more places, respectively. The flow rates of the first and second carrier gases are not particularly limited, but are 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 I)
In the film-forming step I, the first and second mists are reacted in the vicinity of the surface of the base substrate to form a film on a part or all of the surface of the base substrate. The thermal reaction is not particularly limited as long as it is a thermal reaction in which a film is formed from the mist, and it may be sufficient if the mist reacts 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 400 ° C. to 650 ° C. preferable. Further, the thermal reaction may be carried out under any atmosphere of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere as long as the object of the present invention is not impaired, and the thermal reaction may be carried out under atmospheric pressure. It may be carried out under either pressure or reduced pressure, but in the present invention, it is preferably carried out in an oxygen atmosphere, preferably in an atmospheric pressure, and in an oxygen atmosphere and at atmospheric pressure. More preferably done below. The film thickness can be set by adjusting the film forming time.

The means for forming the crystalline oxide semiconductor film of the present invention is not particularly limited and may be a known means as long as the object of the present invention is not impaired. Examples of the means for forming the crystalline oxide semiconductor film include a CVD method, a MOCVD method, a MOVPE method, a mist CVD method, a mist epitaxy method, an MBE method, an HVPE method, and a pulse growth method. In the present invention, the means for forming the oxide layer is preferably a MOCVD method, an MBE method, an HVPE method, a mist CVD method or a mist epitaxy method, and more preferably a mist CVD method or a mist epitaxy method. preferable.

Hereinafter, as a preferred example of the means for forming the crystalline oxide semiconductor film, the crystalline oxide semiconductor film is formed on the surface of the crystalline oxide semiconductor film by using a mist CVD method or a mist epitaxy method. The present invention will be described in more detail with reference to an example formed on the substrate.

In the mist CVD method or mist epitaxy method, the raw material solution of the crystalline oxide semiconductor is atomized (atomization step II), and the generated mist is used as a carrier gas to form a base substrate on the surface of which the oxide layer is formed. (Transport step II), and a crystalline oxide semiconductor film is formed on the base substrate by a thermal reaction (film forming step II).

(Atomization step II)
The atomization step II atomizes the raw material solution of the crystalline oxide semiconductor (hereinafter, also referred to as “raw material solution II”). The atomizing means is not particularly limited as long as the raw material solution II can be atomized, and may be a known means, but in the present invention, the atomizing means using ultrasonic waves is preferable. The mist obtained by using ultrasonic waves is preferable because it has a zero initial velocity and floats in the air. For example, a mist that can float in a space and be transported as a gas instead of being sprayed like a spray. Therefore, it is very suitable because it is not damaged by collision energy. The size of the mist droplets is not particularly limited and may be about several mm, but is preferably 50 μm or less, and more preferably 100 nm to 10 μm.

(Raw material solution of crystalline oxide semiconductor)
The raw material solution II is not particularly limited as long as it is a solution from which the crystalline oxide semiconductor can be obtained by a mist CVD method or a mist epitaxy method. Examples of the raw material solution II include an aqueous solution of a metal organic metal complex (for example, an acetylacetonate complex) and a halide (for example, fluoride, chloride, bromide, iodide, etc.). The metal may be any metal that can form a semiconductor, and examples of such a metal include gallium, indium, aluminum, and iron. In the present invention, the metal preferably contains at least indium, gallium or aluminum, more preferably at least gallium. The content of the metal in the raw material solution II is not particularly limited as long as the object of the present invention is not impaired, but is preferably 0.001 mol% to 50 mol%, and more preferably 0.01 mol% to 50 mol. %.

Further, the raw material solution II preferably contains a dopant. By including the dopant, the crystalline oxide semiconductor film can be formed without performing ion implantation or the like. Examples of the dopant include n-type dopants such as silicon, germanium, tin, and lead when the metal contains at least gallium. In the present invention, it is preferable that the dopant is tin because the electrical characteristics can be further improved. When the dopant is contained in the raw material solution II, it is preferably contained in the form of a halide or a complex. The doping amount is not particularly limited as long as the object of the present invention is not impaired, but the volume ratio in the raw material solution II is preferably 0.001 to 20%, preferably 0.01 to 10%. More preferred. Further, in the present invention, non-doped is also preferable.

In addition, the raw material solution II may further contain other additives such as acids and bases. In the present invention, it is preferable that the raw material solution II contains an acid, and examples of such a preferable acid include hydrochloric acid, hydrobromic acid, hydroiodic acid and the like.

The solvent of the raw material solution II is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solution of an inorganic solvent and an organic solvent. In the present invention, the solvent preferably contains water, and it is also preferable that the solvent is a mixed solvent of water and acid. More specific examples of the water include pure water, ultrapure water, tap water, well water, mineral spring water, mineral water, hot spring water, spring water, fresh water, seawater, and the like. Ultrapure water is preferred. More specifically, the acid includes organic acids such as acetic acid, propionic acid, and butanoic acid; boron trifluoride, boron trifluoride etherate, boron trichloride, boron tribromide, and trifluoroacetic acid. , Trifluoromethanesulfonic acid, p-toluenesulfonic acid and the like, but in the present invention, acetic acid is preferable.

(Transport step II)
In the transport step II, the mist is transported to the base substrate by the carrier gas using the base substrate on which the oxide layer is formed on the surface. The type of carrier gas is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include an inert gas such as oxygen, ozone, nitrogen and argon, and a reducing gas such as hydrogen gas and forming gas. In the present invention, it is preferable to use oxygen as the carrier gas. Further, the type of the carrier gas may be one type, but may be two or more types, and a diluted gas having a changed carrier gas concentration (for example, a 10-fold diluted gas or the like) may be further used. 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 II)
In the film-forming step II, the mist is reacted in the vicinity of the surface of the base substrate to form a film on a part or all of the surface of the base substrate. The thermal reaction is not particularly limited as long as it is a thermal reaction in which a film is formed from the mist, and it may be sufficient if the mist reacts 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 400 ° C. to 650 ° C. preferable. Further, the thermal reaction may be carried out under any atmosphere of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere as long as the object of the present invention is not impaired, and the thermal reaction may be carried out under atmospheric pressure. It may be carried out under either pressure or reduced pressure, but in the present invention, it is preferably carried out in an oxygen atmosphere, preferably in an atmospheric pressure, and in an oxygen atmosphere and at atmospheric pressure. More preferably done below. The film thickness can be set by adjusting the film forming time.

The crystalline oxide semiconductor film or laminated structure obtained as described above can be suitably used for semiconductor devices and the like, and is particularly useful for power devices. For example, the crystalline oxide semiconductor film is used for an n-type semiconductor layer (including an n + type semiconductor layer and an n− type semiconductor layer) or a p-type semiconductor layer of the semiconductor device. Further, in the present invention, the crystalline oxide semiconductor film or the laminated structure may be used as it is, or may be applied to a semiconductor device or the like after using a known means such as peeling from the substrate or the like. You may.

Further, the semiconductor device is classified into a horizontal element (horizontal device) in which electrodes are formed on one side of the semiconductor layer and a vertical element (vertical device) in which electrodes are provided on both front and back sides of the semiconductor layer. Therefore, in the present invention, it can be suitably used for both horizontal devices and vertical devices, and among them, it is preferably used for vertical devices. Examples of the semiconductor device include a Schottky barrier diode (SBD), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), a metal oxide film semiconductor field effect transistor (MOSFET), and an electrostatic induction transistor (MSFET). SIT), junction field effect transistor (JFET), insulated gate bipolar transistor (IGBT), light emitting diode (LED), and the like.

Hereinafter, suitable examples when the crystalline oxide semiconductor film of the present invention is applied to an n-type semiconductor layer (n + type semiconductor, n-semiconductor layer, etc.) will be described with reference to the drawings. It is not limited to the example of. In the semiconductor device exemplified below, other layers (for example, an insulator layer, a semi-insulator layer, a conductor layer, a semiconductor layer, a buffer layer, another intermediate layer, etc.) may be used as long as the object of the present invention is not impaired. It may be contained, and the buffer layer (buffer layer) and the like may be omitted as appropriate.

FIG. 5 shows an example of a Schottky barrier diode (SBD) according to the present invention. The SBD of FIG. 5 includes an n-type semiconductor layer 101a, an n + type semiconductor layer 101b, a Schottky electrode 105a, and an ohmic electrode 105b.

The material of the Schottky electrode and the ohmic electrode may be a known electrode material, and the electrode material includes, for example, Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, etc. Metals such as Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd or Ag or alloys thereof, tin oxide, zinc oxide, renium oxide, indium oxide, indium tin oxide (ITO) ), Metal oxide conductive film such as zinc oxide indium (IZO), organic conductive compound such as polyaniline, polythiophene or polypyrrol, or a mixture and laminate thereof.

The Schottky electrode and the ohmic electrode can be formed by a known means such as a vacuum vapor deposition method or a sputtering method. More specifically, for example, when a Schottky electrode is formed by using two kinds of the first metal and the second metal among the metals, a layer made of the first metal and a layer made of the second metal are formed. It can be carried out by laminating and patterning the layer made of the first metal and the layer made of the second metal by using a photolithography technique.

When a reverse bias is applied to the SBD of FIG. 5, 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 semiconductor structure in this way is excellent for high withstand voltage and large current, has a high switching speed, and is also excellent in withstand voltage and reliability.

(HEMT)
FIG. 6 shows an example of a high electron mobility transistor (HEMT) according to the present invention. The HEMT of FIG. 6 includes an n-type semiconductor layer 121a with a wide bandgap, an n-type semiconductor layer 121b with a narrow bandgap, an n + type semiconductor layer 121c, a semi-insulator layer 124, a buffer layer 128, a gate electrode 125a, a source electrode 125b, and the like. It includes a drain electrode 125c.

(MOSFET)
FIG. 7 shows an example of the case where the semiconductor device of the present invention is a MOSFET. The MOSFET in FIG. 7 is a trench-type MOSFET, and includes an n-type semiconductor layer 131a, an n + type semiconductor layers 131b and 131c, a gate insulating film 134, a gate electrode 135a, a source electrode 135b, and a drain electrode 135c.

(JFET)
FIG. 8 includes an n-type semiconductor layer 141a, a first n + type semiconductor layer 141b, a second n + type semiconductor layer 141c, a p-type semiconductor layer 142, a gate electrode 145a, a source electrode 145b, and a drain electrode 145c. A suitable example of a junction field effect transistor (JFET) is shown.

(IGBT)
FIG. 9 shows an insulation provided with an n-type semiconductor layer 151, an n-type semiconductor layer 151a, an n + type semiconductor layer 151b, a p-type semiconductor layer 152, a gate insulating film 154, a gate electrode 155a, an emitter electrode 155b, and a collector electrode 155c. A suitable example of a gated bipolar transistor (IGBT) is shown.

(LED)
An example of the case where the semiconductor device of the present invention is a light emitting diode (LED) is shown in FIG. The semiconductor light emitting device of FIG. 10 includes an n-type semiconductor layer 161 on the second electrode 165b, and a light emitting layer 163 is laminated on the n-type semiconductor layer 161. A p-type semiconductor layer 162 is laminated on the light emitting layer 163. A translucent electrode 167 that transmits light generated by the light emitting layer 163 is provided on the p-type semiconductor layer 162, and a first electrode 165a is laminated on the translucent electrode 167. The semiconductor light emitting device of FIG. 10 may be covered with a protective layer except for the electrode portion.

Examples of the material of the translucent electrode include a conductive material of an oxide containing indium (In) or titanium (Ti). More specifically, for example, In ₂ O ₃ , ZnO, SnO ₂ , Ga ₂ O ₃ , TiO ₂ , CeO _2, or a mixed crystal of two or more of these, or those doped with these can be mentioned. A translucent electrode can be formed by providing these materials by a known means such as sputtering. Further, after forming the translucent electrode, thermal annealing may be performed for the purpose of making the translucent electrode transparent.

According to the semiconductor light emitting device of FIG. 10, a first electrode 165a is a positive electrode and a second electrode 165b is a negative electrode, and a current is passed through both of them to the p-type semiconductor layer 162, the light emitting layer 163, and the n-type semiconductor layer 161. As a result, the light emitting layer 163 emits light.

The materials of the first electrode 165a and the second electrode 165b include, for example, Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Metals such as Hf, W, Ir, Zn, In, Pd, Nd or Ag or alloys thereof, tin oxide, zinc oxide, renium oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO) and the like. Examples thereof include metal oxide conductive films, organic conductive compounds such as polyaniline, polythiophene or polypyrrole, or mixtures thereof. The film forming method of the electrode is not particularly limited, and is a wet method such as a printing method, a spray method, and a coating method, a physical method such as a vacuum vapor deposition method, a sputtering method, and an ion plating method, CVD, and plasma CVD. It can be formed on the substrate according to a method appropriately selected in consideration of suitability with the material from chemical methods such as a method.

In addition, another aspect of the light emitting element is shown in FIG. In the light emitting element of FIG. 11, an n-type semiconductor layer 161 is laminated on the substrate 169, and the n-type semiconductor exposed by cutting out a part of the p-type semiconductor layer 162, the light emitting layer 163, and the n-type semiconductor layer 161. The second electrode 165b is laminated on a part of the exposed surface of the semiconductor layer of the layer 161.

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. 12 shows an example of a power supply system. In FIG. 12, a power supply system is configured by using the plurality of power supply devices and control circuits. As shown in FIG. 13, 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. 14 shows a power supply circuit of a power supply device including a power circuit and a control circuit. A DC voltage is switched at a high frequency by an inverter (composed of MOSFETs A to D), converted to AC, and then insulated and transformed by 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 to output a DC voltage. 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.

Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.
<Example>
1. 1. Film-forming device The mist CVD device used in this embodiment 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 pipe 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. Preparation of raw material solution Gallium bromide was mixed with ultrapure water so as to be 0.1 mol / L, and at this time, hydrobromic acid was contained at 10% by volume, and this was used as the raw material solution.

3. 3. Preparation for film formation 2. The raw material solution 24a obtained in 1) was housed in the mist source 24. Next, as the substrate 20, as shown in FIG. 15, the first layer 2a is α- (Al _0.12 Ga _0.88 ) ₂ O ₃ layer (thickness 120 nm), and the second layer 2b is α. -(Al _0.02 Ga _0.98 ) _{A c-plane sapphire substrate 1 on which 2} O ₃ layers (thickness 120 nm) are laminated is installed on the susceptor 21, and the temperature of the heater 28 is raised to 500 ° C. It was. Next, the flow control valves 23a and 23b are opened to supply the carrier gas into the supply pipe 27 from the carrier gas supply means 22a and 22b which are the carrier gas sources, and the atmosphere in the supply pipe 27 is sufficiently replaced with the carrier gas. After that, 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. Oxygen was used as the carrier gas.

4. Membrane formation Next, the ultrasonic vibrator was vibrated and the vibration was propagated to the raw material solution 24a through the water 25 to atomize the raw material solution 24a and generate mist. This mist was conveyed to the supply pipe 27 by the carrier gas, and the mist thermally reacted near the surface of the substrate 20 at 500 ° C. under atmospheric pressure to form a film on the substrate 20. The film forming time was 1.5 hours, and the film thickness was 3 μm.

5. Evaluation Above 4. When the crystalline oxide semiconductor film obtained in (1) was identified using an X-ray diffractometer, the obtained film was an α-Ga ₂ O ₃ film. The results of observing the surface of the obtained α-Ga ₂ O ₃ film with an optical microscope are shown in FIG. As can be seen from FIG. 2, the obtained α-Ga ₂ O ₃ film was a film substantially free of cracks over an area of 300 μm square or more on the film surface. Further, even when the film is formed by the same method until the film thickness of the α-Ga ₂ O _{3 film reaches 5 μm, the α-Ga 2} O ₃ film containing no cracks is formed over an area of 300 μm square or more on the film surface. Obtained.

<Comparative example 1>
As the base substrate, as shown in FIG. 16, as the first layer 2a, _{a c-plane sapphire substrate 1 having an α- (Al 0.12} Ga _0.88 ) ₂ O ₃ layer (thickness 120 nm) formed on the surface thereof. A crystalline oxide semiconductor film was obtained in the same manner as in Example 1 except that it was used. When the membrane was identified using an X-ray diffractometer, the obtained membrane was an α-Ga ₂ O ₃ membrane. The film thickness was 3 μm. The result of observing the surface of the obtained α-Ga ₂ O ₃ film with an optical microscope is shown in FIG. As can be seen from FIG. 3, the obtained α-Ga ₂ O ₃ film was a film containing cracks in an area of 300 μm square on the film surface.

<Comparative example 2>
A crystalline oxide semiconductor film was obtained in the same manner as in Example 1 except that a c-plane sapphire substrate was used as the base substrate. When the membrane was identified using an X-ray diffractometer, the obtained membrane was an α-Ga ₂ O ₃ membrane. The film thickness was 3 μm. The result of observing the surface of the obtained α-Ga ₂ O ₃ film with an optical microscope is shown in FIG. As can be seen from FIG. 4, the obtained α-Ga ₂ O ₃ film was a film containing cracks in an area of 300 μm square on the film surface.

The crystalline oxide semiconductor film of the present invention can be used in all fields such as semiconductor devices (for example, compound semiconductor electronic devices, etc.), electronic parts / electrical equipment parts, optical / electrophotographic-related equipment, industrial parts, etc. It is useful for semiconductor devices and the like.

1 c-plane sapphire substrate 2a 1st layer 2b 2nd layer 19 Mist CVD device 20 Substrate 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 transducer 27 Supply pipe 28 Heater 29 Exhaust port 101a n-type semiconductor layer 101b n + type semiconductor layer 102p type semiconductor layer 103 Semi-insulator layer 104 Insulation layer 105a Shotkey electrode 105b Ohmic electrode 121a n-type semiconductor layer with wide band gap 121b n-type semiconductor layer with narrow band gap 121c n + type semiconductor layer 123 p-type semiconductor layer 124 Semi-insulator layer 125a Gate electrode 125b Source electrode 125c Drain electrode 128 Buffer layer 131a n-type semiconductor Layer 131b First n + type semiconductor layer 131c Second n + type semiconductor layer 132 p type semiconductor layer 134 Gate insulating film 135a Gate electrode 135b Source electrode 135c Drain electrode 141a n-type semiconductor layer 141b First n + type semiconductor layer 141c Second n + type semiconductor layer 142 p-type semiconductor layer 145a Gate electrode 145b Source electrode 145c Drain electrode 151 n-type semiconductor layer 151a n-type semiconductor layer 151b n + type semiconductor layer 152 p-type semiconductor layer 154 Gate insulating film 155a Gate electrode 155b Emitter electrode 155c Collector electrode 161 n-type semiconductor layer 162 p-type semiconductor layer 163 Light emitting layer 165a First electrode 165b Second electrode 167 Translucent electrode 169 Substrate

Claims (16)

The crystalline oxide semiconductor having a corundum structure a crystalline oxide semiconductor film containing as a main component, in the area of 300μm four-way membrane surface, crystalline oxide, wherein the free of cracks substantially Material semiconductor film. The crystalline oxide semiconductor film according to claim 1, wherein the film thickness is 3 μm or more. The crystalline oxide semiconductor film according to claim 1 or 2, wherein the crystalline oxide semiconductor contains indium, gallium, or aluminum. The crystalline oxide semiconductor film according to any one of claims 1 to 3, wherein the crystalline oxide semiconductor contains gallium. The crystalline oxide semiconductor film according to any one of claims 1 to 4, further comprising a dopant. The crystalline oxide semiconductor film according to any one of claims 1 to 5, wherein the film thickness is 5 μm or more. During the area of 400μm four-way membrane surface, characterized in that it contains no cracks in substantially crystalline oxide semiconductor film according to claim 1. A base substrate having a corundum structure, two or more oxide layers including at least a first layer and a second layer directly on the base substrate or via another layer, and claim 1 on the oxide layer. The crystalline oxide semiconductor film according to any one of 7 to 7 is provided, and the main component of the first layer is a crystalline oxide having a corundum structure, and the main component of the second layer is the first layer. A laminated structure characterized in that the composition ratio is different from that of the main component of the layer. The main components of the first layer contain gallium and aluminum, the main components of the second layer contain gallium and aluminum, and the atomic ratio of aluminum to gallium in the main components excluding oxygen of the first layer is 1 to 1. The laminated structure according to claim 8, which is 20% and is larger than the atomic ratio of aluminum to gallium in the main component excluding oxygen of the second layer. A semiconductor device including at least an electrode and the crystalline oxide semiconductor film according to any one of claims 1 to 7 or the laminated structure according to claim 8 or 9. A system including the semiconductor device according to claim 10. The oxide is formed by using a base substrate in which two or more oxide layers including at least a first layer and a second layer are formed on the surface over an area of 300 μm square or more directly or via another layer. on the layer, see containing a crystalline oxide semiconductor having a corundum structure as a main component, a crystalline oxide semiconductor forming the crystalline oxide semiconductor film containing no crack substantially in the area of 300μm square film surface In the method for producing a film, the base substrate has a corundum structure, the main component of the first layer is a crystalline oxide having a corundum structure, and the main component of the second layer is. A method for producing a crystalline oxide semiconductor film, which is characterized in that the composition ratio is different from that of the main component of the first layer. The main components of the first layer contain gallium and aluminum, the main components of the second layer contain gallium and aluminum, and the atomic ratio of aluminum to gallium in the main components excluding oxygen of the first layer is 1 to 1. The production method according to claim 12, which is 20% and is larger than the atomic ratio of aluminum to gallium in the main component excluding oxygen of the second layer. The production method according to claim 12 or 13, wherein the crystalline oxide semiconductor film is formed by a mist CVD method. The production method according to any one of claims 12 to 14, wherein the main component of the base substrate is a crystalline oxide different from the main component of the first layer. The production method according to any one of claims 12 to 15, wherein the main component of the crystalline oxide semiconductor film is a crystalline oxide semiconductor different from the main component of the first layer.

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