JP2021038116A - Laminate structure, semiconductor device, and method for producing laminate structure - Google Patents

Abstract

To provide an inexpensive laminate structure that is thermally stable and includes a crystalline oxide film with excellent electrical characteristics.SOLUTION: A laminate structure has a crystalline substrate, and a crystalline oxide film having gallium as the main component and having a β-gallia structure. The crystalline substrate is a lithium tantalate crystalline substrate. On the principal surface of the lithium tantalate crystalline substrate, the crystalline oxide film having β-Ga2O3 as the main component is laminated. The principal surface of the lithium tantalate crystalline substrate is an a-, m- or r-plane.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated structure, a semiconductor device, and a method for manufacturing the laminated structure.

Oxide semiconductors typified by gallium oxide (Ga ₂ O ₃ ) are expected to be applied to next-generation switching devices capable of achieving high withstand voltage, low loss, and high heat resistance as semiconductors with a large bandgap.

Japanese Unexamined Patent Publication No. 2014-072463 Japanese Unexamined Patent Publication No. 2014-015366 JP-A-2015-091740

Patent Document 1 describes a method for producing _{gallium oxide (α-Ga 2} O ₃ ) having a corundum structure at a relatively low temperature, _{but since α-Ga 2} O ₃ is a metastable phase, There is a problem of thermal instability.

On the other hand, β-Ga ₂ O ₃ is the most stable phase, and the above-mentioned phase transition does not occur. However, as described in Patent Documents 2 and 3, it is necessary to heat to an extremely high temperature in order to form a film, and a lower temperature, simple and inexpensive film forming method is required. It was.

In order to use a crystalline oxide film having a beta-gallian structure in a semiconductor device, as described above, a film having high thermal stability and excellent electrical characteristics of the film has been required.

The present invention has been made to solve the above problems, to provide an inexpensive laminated structure having a crystalline oxide film which is thermally stable and has excellent electrical characteristics, and heat. It is an object of the present invention to provide a film forming method capable of forming a laminated structure having a crystalline oxide film which is stable and has excellent electrical characteristics easily and inexpensively by a low temperature process.

The present invention has been made to achieve the above object, and is a laminated structure having a crystalline substrate and a crystalline oxide film containing gallium as a main component and having a beta-gallian structure, and the crystalline substrate. Is a lithium tantalate crystal substrate, and the _{crystalline oxide film containing β-Ga 2} O ₃ as a main component is laminated on the main surface of the lithium tantalate crystal substrate. Provided is a laminated structure characterized in that the main surface of the above is an a-plane, an m-plane or an r-plane.

Such a laminated structure can be obtained easily and inexpensively, is thermally stable, has excellent electrical characteristics, and can be suitably used for a semiconductor device.

At this time, the crystalline oxide film can be a laminated structure containing a dopant.

By including the dopant in this way, the conductivity of the crystalline oxide film can be controlled more reliably.

At this time, the dopant can be a laminated structure containing one or more selected from tin, germanium, silicon, titanium, zirconium, vanadium, and niobium.

This results in an n-type crystalline oxide film.

At this time, the crystalline oxide film can be a laminated structure having a film thickness of 1 μm or more.

This makes the semiconductor device more useful.

At this time, a laminated structure having an area of 100 mm ² or more of the crystalline oxide film can be formed.

This makes the large area more useful for semiconductor devices.

At this time, the semiconductor device including the above-mentioned laminated structure can be obtained.

As a result, the semiconductor device has excellent characteristics.

Further, the mist generated by atomizing or dropletizing an aqueous solution containing at least gallium is conveyed to a substrate using a carrier gas, and the mist is thermally reacted on the substrate to have gallium as a main component and beta galia. A method of forming a crystalline oxide film having a structure on the main surface of the substrate, wherein the substrate is a lithium tantalate crystal substrate whose main surface is an a-plane, an m-plane or an r-plane. Provided is a method for manufacturing a laminated structure characterized by the above.

According to the method for producing such a laminated structure, a laminated structure containing a crystalline oxide film having a beta-gallian structure, being thermally stable, and having excellent electrical characteristics can be produced with high productivity in a low temperature process. , Can be manufactured easily and inexpensively.

At this time, a method for producing a laminated structure in which the crystalline oxide film contains β-Ga ₂ O _{3 as a main component can be used.}

This makes it possible to provide a laminated structure having a thermally more stable crystalline oxide film.

At this time, a method for producing a laminated structure in which a dopant is contained in the aqueous solution and doped at the time of forming the crystalline oxide film can be used.

By doping in this way, the conductivity of the crystalline oxide film can be controlled more reliably.

At this time, the method for producing a laminated structure in which the dopant is one or more selected from tin, germanium, silicon, titanium, zirconium, vanadium, and niobium can be used.

As a result, an n-type crystalline oxide film can be obtained.

At this time, the method for manufacturing a laminated structure in which the temperature of the thermal reaction is 250 to 900 ° C. can be used.

As a result, the laminated structure having a beta-galia structure can be manufactured at a lower temperature, so that not only the running cost can be reduced, but also the time required for manufacturing can be shortened.

At this time, a method for producing a laminated structure in which the film thickness of the crystalline oxide film is 1 μm or more can be used.

Thereby, a useful laminated structure can be obtained by the semiconductor device.

At this time, as the substrate, a substrate having an area of 100 mm ² or more on the main surface can be used.

As a result, a large-area laminated structure can be easily and inexpensively obtained.

As described above, according to the laminated structure of the present invention, the laminated structure is thermally stable, has excellent electrical characteristics, and can be suitably used for a semiconductor device. In addition, the semiconductor device has excellent characteristics. Further, according to the method for producing a laminated structure of the present invention, a laminated structure containing a crystalline oxide film having a beta-gallian structure, being thermally stable, and having excellent electrical characteristics can be easily and inexpensively produced. Can be manufactured.

It is a schematic sectional drawing which shows an example of the laminated structure which concerns on this invention. It is a schematic block diagram which shows an example of the film forming apparatus used in the manufacturing method of the laminated structure which concerns on this invention. It is a figure explaining an example of the mist formation part in the film forming apparatus.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

As described above, it is possible to provide an inexpensive laminated structure having a crystalline oxide film which is thermally stable and has excellent electrical properties, and which is thermally stable and has excellent electrical properties. It has been required to provide a method for producing a laminated structure in which a crystalline oxide film is formed by a low-temperature process easily and inexpensively.

As a result of diligent studies on the above problems, the present inventors have found that the crystalline substrate is a laminated structure having a crystalline substrate and a crystalline oxide film containing gallium as a main component and having a beta-gallian structure. It is a lithium tantalate crystal substrate, and the _{crystalline oxide film containing β-Ga 2} O ₃ as a main component is laminated on the main surface of the lithium tantalate crystal substrate. A laminated structure in which the main surface is an a-plane, an m-plane, or an r-plane makes it easy and inexpensive to obtain, is thermally stable, and has excellent electrical characteristics, and is suitable for semiconductor devices. The present invention has been completed by finding that it can be used in the above.

Further, the present inventors transfer the mist generated by atomizing or dropletizing an aqueous solution containing at least gallium to a substrate using a carrier gas, and thermally react the mist on the substrate. A method of forming a crystalline oxide film containing gallium as a main component and having a beta-gallian structure on the main surface of the substrate, wherein the main surface of the substrate is a-plane, m-plane or r-plane tantalate. By the method for producing a laminated structure using a lithium crystal substrate, a laminated structure containing a crystalline oxide film having a beta-gallian structure, being thermally stable, and having excellent electrical characteristics can be produced at a low temperature with high productivity. The present invention has been completed by finding that it can be manufactured easily and inexpensively.

Hereinafter, description will be made with reference to the drawings.

(Laminated structure)
As shown in FIG. 1, one embodiment of the laminated structure 1 according to the present invention contains gallium as a main component on the main surface of a lithium tantalate crystal substrate (a crystalline substrate containing lithium tantalate as a main component) 10. It is a laminated structure 1 in which a crystalline oxide film 20 having a beta-gallium structure (specifically, one containing β-Ga ₂ O ₃ as a main component) is laminated. A buffer layer or the like may be interposed between the lithium tantalate crystal substrate 10 and the crystalline oxide film 20.
In the lithium tantalate crystal substrate 10, the main surface on which the crystalline oxide film 20 is laminated is an a-plane, an m-plane or an r-plane, but the a-plane or the m-plane is particularly preferable, and the a-plane is the a-plane. Is even more preferable.

Here, the term "crystallinity" means that the crystalline state includes a polycrystalline state or a single crystal state. Amorphous may be mixed in polycrystal or single crystal.

(Lithium tantalate crystal substrate)
First, the lithium tantalate crystal substrate contained in the laminated structure according to the present invention will be described.

When producing the laminated structure according to the present invention, first, a lithium tantalate crystal substrate is prepared. A substrate containing 50 to 100% lithium tantalate, which contains lithium tantalate as a single crystal as well as a polycrystalline one.

Lithium tantalate has an ilmenite structure and its lattice constant is relatively close to _{α-Ga 2} O _3. The magnitude relationship between the distances between oxygen atoms on the α-Ga ₂ O ₃ (001) plane, the β-Ga ₂ O ₃ (-201) plane, and the lithium tantalate (001) plane is generally α-Ga ₂ O ₃ <Lithium tantalate <β-Ga ₂ O ₃ . Since β-Ga ₂ O ₃ is energetically more stable than α-Ga ₂ O _{3 , α-Ga 2} O ₃ is not formed on the lithium tantalate substrate even at low temperatures, and β-Ga ₂ O ₃ is formed. It is presumed that they are formed preferentially.

As the lithium tantalate crystal substrate, it is most preferable to use a lithium tantalate single crystal substrate. This is because the quality of the crystalline oxide film is the highest quality.

Hereinafter, a lithium tantalate single crystal substrate will be described as an example. The lithium tantalate single crystal substrate can be obtained, for example, by growing a lithium tantalate single crystal by the Czochralski method to obtain a lithium tantalate single crystal ingot, and slicing this ingot to process it into a substrate shape.

The lithium tantalate single crystal substrate that can be used in the present invention is preferably cut so that the lattice constant on its surface is close to the lattice constant of the crystalline oxide film to be deposited later. For example, _{when a crystalline oxide film containing β-Ga 2} O ₃ as a main component is deposited, it is preferably cut so that the crystal orientation is within Z ± 10 °, and more preferably the crystal orientation is It should be cut so that it is within Z ± 5 °.

Further, in the lithium tantalate single crystal substrate that can be used in the present invention, it is preferable that the uniform polarization state of the substrate promotes uniform growth of the oxide single crystal film. That is, it is preferable that the lithium tantalate substrate is subjected to a single polarization treatment or a multi-polarization treatment.

To obtain a monopolarized substrate, for example, a lithium tantalate single crystal ingot prepared by the Czochralski method is heated to 700 ° C., and a voltage of 200 V is applied in the crystal direction Z direction for 10 hours. After polling, the ingot may be sliced and processed into a substrate shape. Further, the substrate itself processed into the substrate shape may be heated to 700 ° C., and a voltage of 200 V may be applied in the crystal direction Z direction to perform polling treatment for 10 hours.

When a substrate subjected to a single polarization treatment is further subjected to a pyroelectricity suppressing treatment on the substrate surface, it is possible to suppress the substrate from being charged when a crystalline oxide film is deposited on the heated substrate. Is preferable. In the pyroelectric suppression treatment, for example, a lithium tantalate single crystal substrate subjected to a single polarization treatment is embedded in lithium carbonate powder, and the temperature is 350 ° C. or higher and the Curie temperature (about 610 ° C.) in a reducing gas atmosphere. Heat treatment is performed at the following temperature. At this time, the volume resistivity in the thickness direction of the substrate is 1.0 × 10 ¹¹ Ω · cm or more, 2.0 × 10 ¹³ Ω · cm or less, and the maximum and minimum values of the volume resistivity in the substrate. When the treatment is performed so that the ratio is 4.0 or less, the resistivity of the substrate when the crystalline oxide film is deposited on the substrate can be effectively suppressed.

On the other hand, in order to obtain a multipolarized substrate, for example, a single crystal (ingot or substrate) once monopolarized or a single crystal (ingot or substrate) not subjected to the monopolarization treatment is subjected to. It is heated to 700 ° C. or higher and annealed for several hours (preferably 1000 ° C. or higher, preferably 5 hours or longer, more preferably 10 hours or longer) to perform strain relief treatment, and in the case of an ingot, it is sliced to form a substrate. It is good to process it into. It is preferable to use a multipolarized substrate because it is possible to suppress the substrate from being charged when the crystalline oxide film is deposited on the heated substrate. In particular, when the average polarization size of the substrate surface is set to 5 μm or less, charging can be effectively suppressed. When the charging effect of the lithium tantalate substrate is suppressed, it is preferable that the crystalline oxide film is stably deposited. It is preferable that the composition (at least on the surface of the substrate) of the lithium tantalate single crystal is a congluent composition, because the average domain size of the polarization on the surface of the substrate tends to be small. Here, in the case of lithium tantalate, the congluent composition means that the ratio of Li to Ta is Li: Ta = 48.5-α: 51.5 + α, and α is −0.5 ≦ α ≦ 0.5. It means that it is a range.

When the surface of the lithium tantalate crystal substrate is polished so that the unevenness becomes small, a flat laminated film of a crystalline oxide film can be obtained. Ra is preferably 10 nm or less. It is more preferable that Ra is 5 nm or less.

In addition, ions selected from hydrogen, helium, argon, and other rare gases are injected in advance into the surface of the lithium tantalate crystal substrate on which the crystalline oxide film is deposited, and a fragile layer is formed directly below 50 nm to 3 μm of the deposited surface. It can also be formed. By doing so, after the crystalline oxide film is deposited, the deposited crystalline oxide film can be easily peeled off from the lithium tantalate single crystal substrate by giving an impact to the fragile layer.

The thickness of the crystalline substrate is not particularly limited, but is preferably 10 to 2000 μm, and more preferably 50 to 800 μm. The area of the substrate ^{is preferably 100 mm 2} or more, and more preferably the diameter is 2 inches (50 mm) or more.

(Crystalline oxide film)
The crystalline oxide film in the laminated structure according to the present invention is a crystalline oxide film containing gallium as a main component and having a beta-gallian structure. The crystalline oxide film is usually composed of a metal and oxygen, but in the present invention, there is no problem as long as gallium is the main component as the metal. Here, when the term "gallium is the main component" in the present invention, it means that 50 to 100% of the metal components are gallium. The metal component other than gallium may include, for example, one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, iridium, nickel and cobalt. The crystalline oxide film may be single crystal or polycrystalline as long as it has a beta-gallian structure.

Among the crystalline oxide films containing gallium as the main component and having a beta-gallian structure, those containing β-Ga ₂ O ₃ as the main component. β-Ga ₂ O ₃ is a thermally more stable crystalline oxide film.

The crystalline oxide film may contain a dopant. Examples thereof include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants such as copper, silver, tin, iridium and rhodium. The dopant is not particularly limited, but is preferably tin. The concentration of the dopant may be, for example, about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and even at ^{a low concentration of about 1 × 10 17} / cm ³ or less, about 1 × 10 ^20. / cm ³ or more may be a high concentration.

In the present invention, the film thickness of the crystalline oxide film is not particularly limited, but can be 1 μm or more. For example, it may be 1 to 100 μm, preferably 5 to 50 μm, and more preferably 10 to 20 μm. Further, another layer may be interposed between the substrate and the crystalline oxide film. The other layer is a layer having a composition different from that of the crystalline oxide film of the substrate and the outermost layer, and may be, for example, a crystalline oxide film, an insulating film, a metal film, or the like.
The area of the crystalline oxide film ^{is preferably 100 mm 2} or more, and more preferably 2 inches (50 mm) or more in diameter, as in the case of the substrate.

The laminated structure according to the present invention or the crystalline oxide film obtained from the laminated structure can be used in a semiconductor device by appropriately designing the structure. For example, Schottky barrier diode (SBD), metal semiconductor field effect transistor (MESFET), high electron mobility transistor (HEMT), metal oxide film semiconductor field effect transistor (MOSFET), electrostatic induction transistor (SIT), junction electric field effect. Each semiconductor layer such as a transistor (JFET), an insulated gate bipolar transistor (IGBT), and a light emitting diode (LED) can be formed.

(Film formation equipment)
In one embodiment of the laminated structure according to the present invention, a mist generated by atomizing or dropletizing an aqueous solution containing at least gallium is conveyed to a substrate using a carrier gas, and the mist is transferred onto the substrate. A method of forming a crystalline oxide film containing gallium as a main component and having a beta-gallian structure on the main surface of the substrate by thermal reaction. The main surface of the substrate is a-plane, m-plane or It is characterized by using an r-plane lithium tantalate crystal substrate.

FIG. 2 shows an example of a film forming apparatus 101 that can be used in the method for manufacturing a laminated structure according to the present invention. The film forming apparatus 101 heat-treats the mist to form a film on the substrate, the mist-forming unit 120 that mists the raw material solution to generate the mist, the carrier gas supply unit 130 that supplies the carrier gas that conveys the mist, and the mist. It has a film forming section 140, a mist forming section 120, and a transport section 109 that connects the film forming section 140 and conveys mist by a carrier gas. Further, the film forming apparatus 101 may be controlled in its operation by providing a control unit (not shown) for controlling the whole or a part of the film forming apparatus 101.

Here, the mist in the present invention refers to a general term for fine particles of liquid dispersed in a gas, and includes those called mist, droplets, and the like.

(Raw material solution)
The raw material solution (aqueous solution) 104a is not particularly limited as long as it contains at least gallium. That is, in addition to gallium, for example, one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, iridium, nickel and cobalt may be contained. A metal obtained by dissolving or dispersing the metal in 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 metal chloride salt, metal bromide salt, metal iodide salt and the like. Further, a metal obtained by dissolving the above metal in hydrobromic acid, hydrochloric acid, hydrogen iodide acid or the like can also be used as an aqueous salt solution. The solute concentration is preferably 0.01 to 1 mol / L.

The raw material solution 104a may contain a dopant element. Examples thereof include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants such as copper, silver, tin, iridium and rhodium. The dopant is not particularly limited, but is preferably tin. Moreover, it is preferable that the dopant element is ionized. Therefore, an acid may be mixed with the raw material solution 104a to promote the dissolution of the dopant element. Examples of the acid include hydrogen halides such as hydrobromic acid, hydrochloric acid and hydroiodic acid, hypochlorous acid, chloronic acid, hypobromic acid, bromine acid, hypoiodic acid, iodic acid and the like. Examples thereof include halogen oxo acids, carboxylic acids such as formic acids, nitrates, and the like. In addition, it is also effective to heat or give ultrasonic waves to promote the dissolution.

(Mist conversion department)
In the mist-forming unit 120, a raw material solution 104a is prepared, and the raw material solution 104a is mist-ized to generate mist. The mist-forming means is not particularly limited as long as the raw material solution 104a can be mist-ized, and may be a known mist-forming means, but it is preferable to use a mist-forming means by ultrasonic vibration. This is because it can be made into a mist more stably.

An example of such a mist-forming unit 120 is shown in FIG. For example, even if the mist generation source 104 containing the raw material solution 104a, a medium capable of transmitting ultrasonic vibration, for example, a container 105 containing water 105a, and an ultrasonic vibrator 106 attached to the bottom surface of the container 105 are included. Good. Specifically, the mist generation source 104 composed of a container containing the raw material solution 104a is stored in the container 105 containing the water 105a by using a support (not shown). An ultrasonic oscillator 106 is provided at the bottom of the container 105, and the ultrasonic oscillator 106 and the oscillator 116 are connected to each other. Then, when the oscillator 116 is operated, the ultrasonic oscillator 106 vibrates, the ultrasonic waves propagate into the mist generation source 104 via the water 105a, and the raw material solution 104a is configured to become mist.

(Transport section)
The transport unit 109 connects the mist-forming unit 120 and the film-forming unit 140. The mist is conveyed by the carrier gas from the mist generation source 104 of the mist-forming unit 120 to the film-forming chamber 107 of the film-forming unit 140 via the transport unit 109. The transport unit 109 may be, for example, a supply pipe 109a. As the supply pipe 109a, for example, a quartz pipe, a resin tube, or the like can be used.

(Film film part)
In the film forming section 140, the mist is heated to cause a thermal reaction to form a film on a part or all of the surface (main surface) of the substrate (crystalline substrate) 110. The film forming section 140 is provided with, for example, a film forming chamber 107, and a substrate (crystalline substrate) 110 is installed in the film forming chamber 107, and a hot plate for heating the substrate (crystalline substrate) 110 is provided. 108 can be provided. The hot plate 108 may be provided outside the film forming chamber 107 as shown in FIG. 2, or may be provided inside the film forming chamber 107. Further, the film forming chamber 107 may be provided with an exhaust gas exhaust port 112 at a position that does not affect the supply of mist to the substrate (crystalline substrate) 110.

Further, in the present invention, the substrate (crystalline substrate) 110 may be placed on the upper surface of the film forming chamber 107 to be face-down, or the substrate (crystalline substrate) 110 may be placed on the bottom surface of the film forming chamber 107. It may be installed and used as a face-up. The main surface of this substrate (crystalline substrate), that is, the lithium tantalate crystal substrate is the a-plane, m-plane, or r-plane, and the substrate is installed so as to form a film on the main surface.

The thermal reaction may be such that the mist reacts by heating, and the reaction conditions and the like are not particularly limited. It can be appropriately set according to the raw material and the film film. For example, the heating temperature can be in the range of 250 to 900 ° C, preferably in the range of 300 ° C to 800 ° C, and more preferably in the range of 350 ° C to 700 ° C.

The thermal reaction may be carried out under any of a vacuum, a non-oxygen atmosphere, a reducing gas atmosphere, an air atmosphere and an oxygen atmosphere, and may be appropriately set according to the film film. Further, the reaction pressure may be carried out under any condition of atmospheric pressure, pressurization or reduced pressure, but the film formation under atmospheric pressure is preferable because the apparatus configuration can be simplified.

(Carrier gas supply section)
The carrier gas supply unit 130 has a carrier gas source 102a for supplying the carrier gas, and a flow rate control valve 103a for adjusting the flow rate of the carrier gas (hereinafter, referred to as “main carrier gas”) sent out from the carrier gas source 102a. May be provided. Further, it is also possible to provide a dilution carrier gas source 102b for supplying a dilution carrier gas as needed, and a flow rate control valve 103b for adjusting the flow rate of the dilution carrier gas sent out from the dilution carrier gas source 102b. ..

The type of carrier gas is not particularly limited and can be appropriately selected depending on the film film. For example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas can be mentioned. Further, the type of carrier gas may be one type or two or more types. For example, a diluted gas obtained by diluting the same gas as the first carrier gas with another gas (for example, diluted 10-fold) may be further used as the second carrier gas, or air may be used.

In the present invention, the flow rate Q of the carrier gas refers to the total flow rate of the carrier gas. In the above example, the total flow rate of the main carrier gas sent out from the carrier gas source 102a and the flow rate of the dilution carrier gas sent out from the dilution carrier gas source 102b is defined as the flow rate Q of the carrier gas.

The flow rate Q of the carrier gas is appropriately determined depending on the size of the film forming chamber and the substrate, but is usually 1 to 60 L / min, preferably 2 to 40 L / min.

(Film formation method)
Next, an example of the film forming method according to the present invention will be described with reference to FIG. First, the raw material solution 104a is housed in the mist generation source 104 of the mist-forming unit 120, and the substrate (crystalline substrate) 110 is placed directly on the hot plate 108 or through the wall of the film forming chamber 107, and the hot plate 108 is placed. To operate. Since lithium tantalate has a large coefficient of thermal expansion, it is preferable to gradually raise the temperature from a low temperature.

Next, the flow control valves 103a and 103b are opened to supply the carrier gas from the carrier gas sources 102a and 102b into the film forming chamber 107, and the atmosphere of the film forming chamber 107 is sufficiently replaced with the carrier gas, and the main carrier gas is used. The carrier gas flow rate Q is controlled by adjusting the flow rate of the carrier gas and the flow rate of the carrier gas for dilution, respectively.

In the step of generating mist, the ultrasonic vibrator 106 is vibrated and the vibration is propagated to the raw material solution 104a through water 105a to mist the raw material solution 104a and generate mist. Next, in the step of transporting the mist with the carrier gas, the mist is transported from the mist-forming section 120 to the film forming section 140 via the conveying section 109 by the carrier gas, and is introduced into the film forming chamber 107. In the process of forming a film, the mist introduced into the film forming chamber 107 is heat-treated by the heat of the hot plate 108 in the film forming chamber 107 and undergoes a thermal reaction on the main surface of the substrate (crystalline substrate) 110. A film is formed.

(Peeling)
The crystalline substrate may be peeled off from the crystalline oxide film. The peeling means is not particularly limited and may be a known means. For example, a means for peeling by applying a mechanical impact, a means for peeling by applying heat and utilizing thermal stress, a means for peeling by applying vibration such as ultrasonic waves, a means for etching and peeling, laser lift-off, and the like can be mentioned. Be done. By the peeling, a crystalline oxide film can be obtained as a self-supporting film.

(electrode)
A general method can be used for forming the electrodes required for forming the semiconductor device. That is, in addition to vapor deposition, sputtering, CVD, plating, etc., any printing method such as bonding with a resin or the like may be used. The electrode materials include Al, Ag, Ti, Pd, Au, Cu, Cr, Fe, W, Ta, Nb, Mn, Mo, Hf, Co, Zr, Sn, Pt, V, Ni, Ir, Zn, In. , Nd and other metals, as well as metal oxide conductive films such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO) and indium zinc oxide (IZO), and organic conductive compounds such as polyaniline, polythiophene or polypyrrole. Either of these may be used, and two or more of these alloys and mixtures may be used. The thickness of the electrode is preferably 1 to 1000 nm, more preferably 10 to 500 nm.

Hereinafter, the present invention will be described in detail with reference to examples, but this does not limit the present invention.

(Example 1)
In order to carry out the above-mentioned manufacturing method of the laminated structure by the film forming apparatus (mist CVD apparatus) shown in FIG. 1, gallium oxide was formed under the following conditions.
First, gallium acetylacetonate and tin (II) chloride are mixed with ultrapure water, and the aqueous solution is adjusted so that the atomic ratio of tin to gallium is 1: 0.002 and gallium acetylacetonate is 0.05 mol / L. Then, hydrochloric acid was further contained in a volume ratio of 1.5%, and this was used as a raw material solution. Next, the raw material solution was filled in an atomizer (inside the mist source).

Next, an a-side LT substrate having a diameter of 4 inches (100 mm) and a thickness of 0.3 mm (that is, the main surface for film formation is the a-side) is placed on a quartz susceptor and installed in a quartz tubular film-forming chamber. , The substrate temperature was kept at 450 ° C by a heater.
Next, the raw material solution in the atomizer was atomized with a 2.4 MHz ultrasonic vibrator. After that, nitrogen of the carrier gas is introduced into the atomizer at 1.5 L / min and nitrogen of the diluted gas is introduced at 5 L / min to form an air-fuel mixture, which is supplied to the film forming chamber under atmospheric pressure. The film was formed for 120 minutes.

After that, the substrate was cooled to room temperature, taken out from the film forming chamber, the crystal phase of the formed film was evaluated by the XRD method, and the film thickness was measured by light reflection spectroscopy. After that, the electrical characteristics (carrier mobility, etc.) were further evaluated by measuring the Hall effect.

(Example 2)
The laminated structure was formed and evaluated in the same manner as in Example 1 except that an r-plane LT substrate (that is, the main surface for forming a film was the r-plane) was used as the substrate.

(Example 3)
The laminated structure was formed and evaluated in the same manner as in Example 1 except that an m-plane LT substrate (that is, the main surface on which the film was formed was the m-plane) was used as the substrate.

(Comparative Example 1)
A laminated structure was formed and evaluated in the same manner as in Example 1 except that an LT substrate having a plane orientation <013> was used as the substrate.

The evaluation results of Examples 1-3 and Comparative Example 1 are shown in Table 1 below. As is clear from the results of Examples 1-3, when the film formation is performed using an LT substrate whose main surface is the a-plane, m-plane or r-plane as the crystal substrate, the carrier mobility is more excellent. β-Ga ₂ O ₃ can be obtained.

(Example 4)
After forming a film under the same conditions as in Example 1, the substrate was divided into two at the center to prepare Sample A and Sample B, respectively. Then, sample B was annealed at 600 ° C. for 3 hours.
After that, the crystal phase of the divided sample A and the annealed sample B was evaluated by the XRD method, and the electrical characteristics were further evaluated by the Hall effect measurement. As a result, no difference in the crystallinity and electrical characteristics of the film (change due to annealing treatment) was observed between Sample A and Sample B.

(Comparative Example 2)
A c-plane sapphire was used as the substrate. Other than this, film formation and evaluation were performed under the same conditions as in Example 4.
In sample A, _{the peak of β-Ga 2} O ₃ did not appear, and instead the peak of α-Ga ₂ O ₃ appeared. On the other hand, in sample B, the crystal structure of the film was partially changed, and the peak of _{β-Ga 2} O _{3 appeared.} The carrier mobility was below the lower limit of detection.

Further, as is clear from the results of Example 4, the laminated structure obtained by the present invention can be thermally stable as compared with the results of Comparative Example 2.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

1 ... Laminated structure, 10 ... Crystalline substrate, 20 ... Crystalline oxide film,
101 ... film forming apparatus, 102a ... carrier gas source,
102b ... Carrier gas source for dilution, 103a ... Flow control valve,
103b ... Flow control valve, 104 ... Mist source, 104a ... Raw material solution,
105 ... container, 105a ... water, 106 ... ultrasonic oscillator, 107 ... film formation chamber,
108 ... hot plate, 109 ... transport section, 109a ... supply pipe,
110 ... Substrate (crystalline substrate), 112 ... Exhaust port, 116 ... Oscillator,
120 ... mist formation section, 130 ... carrier gas supply section, 140 ... film formation section.

Claims (13)

A laminated structure having a crystalline substrate and a crystalline oxide film containing gallium as a main component and having a beta-gallian structure.
The crystalline substrate is a lithium tantalate crystal substrate, and the _{crystalline oxide film containing β-Ga 2} O ₃ as a main component is laminated on the main surface of the lithium tantalate crystal substrate.
A laminated structure characterized in that the main surface of the lithium tantalate crystal substrate is an a-plane, an m-plane, or an r-plane. The laminated structure according to claim 1, wherein the crystalline oxide film contains a dopant. The laminated structure according to claim 2, wherein the dopant contains one or more selected from tin, germanium, silicon, titanium, zirconium, vanadium, and niobium. The laminated structure according to any one of claims 1 to 3, wherein the crystalline oxide film has a film thickness of 1 μm or more. The laminated structure according to any one of claims 1 to 4, wherein the area of the crystalline oxide film is 100 mm ^{2 or more.} A semiconductor device comprising the laminated structure according to any one of claims 1 to 5. The mist generated by atomizing or dropletizing an aqueous solution containing at least gallium is conveyed to a substrate using a carrier gas, and the mist is thermally reacted on the substrate to form a beta-gallian structure containing gallium as a main component. A method of forming a crystalline oxide film having a film on the main surface of the substrate.
A method for producing a laminated structure, which comprises using a lithium tantalate crystal substrate whose main surface is an a-plane, an m-plane, or an r-plane as the substrate. The method for producing a laminated structure according to claim 7, wherein the crystalline oxide film contains β-Ga ₂ O _{3 as a main component.} The method for producing a laminated structure according to claim 7, wherein a dopant is contained in the aqueous solution and doped at the time of forming the crystalline oxide film. The method for producing a laminated structure according to claim 9, wherein the dopant is one or more selected from tin, germanium, silicon, titanium, zirconium, vanadium, and niobium. The method for producing a laminated structure according to any one of claims 7 to 10, wherein the temperature of the thermal reaction is 250 to 900 ° C. The method for producing a laminated structure according to any one of claims 7 to 11, wherein the crystalline oxide film has a film thickness of 1 μm or more. The method for manufacturing a laminated structure according to any one of claims 7 to 12, wherein a substrate having an area of 100 mm ^{2 or more is used as the substrate.}

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