JP7053539B2 - Laminates, semiconductor films, semiconductor devices, semiconductor systems and methods for manufacturing laminates - Google Patents

Description

The present invention relates to a semiconductor film containing a metal oxide having a corundum structure as a main component, a laminate having the semiconductor film, a method for manufacturing the laminate, a semiconductor device including the semiconductor film, and a semiconductor system including the semiconductor device. ..

As a next-generation switching element that can realize high withstand voltage, low loss, and high heat resistance, semiconductor devices using gallium oxide (α-Ga ₂ O ₃ ) with a large bandgap are attracting attention, and semiconductor devices for electric power such as inverters. It is also expected to be applied to light receiving and receiving elements.

A mist chemical vapor deposition (Mist CVD) method, in which crystals are grown on a substrate using an atomized mist-like raw material, has been developed and has a colland structure. It has become possible to produce gallium oxide (α-Ga ₂ O ₃ ) having the above (Patent Document 1). In this method, a gallium compound such as gallium acetylacetonate is dissolved in an acid such as hydrochloric acid to form a precursor, and the precursor is atomized to generate raw material fine particles, which are mixed with the raw material fine particles and a carrier gas. Qi is supplied to the surface of a substrate having a corundous structure such as sapphire, and a raw material mist is reacted to grow a unidirectional gallium oxide thin film on the substrate epitaxially.

In showing the performance of α-Ga ₂ O ₃ thus obtained, the mobility of charge carriers (hereinafter, also referred to as “carrier mobility” or “mobility”) is one of the important indexes. Patent Document 1 describes that a Sn-doped α-Ga ₂ O3 thin film formed on a _c -plane sapphire substrate has a mobility of about 1 cm ² / Vs. Further, Patent Document 2 describes that a mobility of 3.26 cm ² / Vs was obtained in the Ge-doped α-Ga ₂ O ₃ formed on the c-plane sapphire substrate.

Japanese Unexamined Patent Publication No. 2013-028480 Japanese Unexamined Patent Publication No. 2015-228495

However, since the mobility obtained by α-Ga ₂ O ₃ described in the above patent document is insufficient as a semiconductor characteristic, it has been difficult to form a high-performance semiconductor device.

The present invention has been made to solve the above problems, to provide a semiconductor film having a corundum structure excellent in electrical characteristics, to provide a laminate containing the semiconductor film, and to provide a corundum structure having excellent electrical characteristics. It is an object of the present invention to provide a method for manufacturing a laminate including a semiconductor film.

The present invention has been made to achieve the above object, and is a laminate including a crystal substrate and a semiconductor film containing a metal oxide having a corundum structure as a main component, and the film thickness of the semiconductor film. The average value of the carbon (C) concentration in the direction is 1.0 × 10 ¹⁹ cm ^-3 or more, 1.0 × 10 ²¹ cm ^-3 or less, and the hydrogen (H) concentration in the film thickness direction of the semiconductor film. Provided is a laminate in which the average value of is equal to or less than the average value of the carbon (C) concentration.

According to such a laminate, a semiconductor film having a high-quality corundum structure having excellent electrical characteristics can be obtained.

At this time, the laminate may have an average value of carbon (C) concentration of 2.0 × 10 ¹⁹ cm ^-3 or more and 5.0 × 10 ²⁰ cm ^-3 or less.

As a result, it has better electrical characteristics.

At this time, a laminate having a carrier mobility in the semiconductor film of 5 cm ² / Vs or more can be obtained. Further, a laminated body having a carrier density of 1.0 × 10 ¹⁶ / cm ³ or more and 1.0 × 10 ²¹ / cm ³ or less in the semiconductor film can be obtained.

This makes it more suitable for semiconductor devices such as power devices.

At this time, the metal oxide may contain Ga oxide or Al oxide.

As a result, it has even better electrical characteristics.

At this time, it is possible to form a laminated body in which the area of the main surface of the crystal substrate is 10 cm ² or more.

This makes it possible to obtain a laminate applicable to a large-area semiconductor device.

At this time, the semiconductor film can be a laminated body having a film thickness of 1 μm or more.

This makes it possible to obtain a laminate having a higher quality semiconductor film with reduced defects.

The present invention is also a semiconductor film containing a metal oxide having a corundum structure as a main component, and the average value of carbon (C) concentration in the film thickness direction of the semiconductor film is 1.0 × 10 ¹⁹ cm ^-3 . As described above, the present invention provides a semiconductor film having 1.0 × 10 ²¹ cm ^-3 or less and having an average value of hydrogen (H) concentration in the film thickness direction of the semiconductor film equal to or less than the average value of carbon (C) concentration. do.

According to such a semiconductor film, a high-quality corundum-structured semiconductor film having excellent electrical characteristics can be obtained.

At this time, the semiconductor device includes at least the semiconductor film and the electrodes, and the semiconductor film can be a semiconductor device including the semiconductor film. Further, it can be a semiconductor system including the above-mentioned semiconductor device.

This makes it possible to provide high-performance semiconductor devices and semiconductor systems.

The present invention also supplies a mixture containing an atomized metal oxide precursor and a carrier gas to a heated crystal substrate, and contains a metal oxide having a corundum structure on the crystal substrate as a main component. A method for producing a laminate for forming a semiconductor film, wherein the air-fuel mixture contains a carbon source, and the content of the carbon source in the air-fuel mixture is the average of the hydrogen (H) concentrations in the film thickness direction of the semiconductor film. It is possible to provide a method for producing a laminate having a content whose value is equal to or less than the average value of the carbon (C) concentration.

According to such a method for producing a laminate, it is possible to produce a laminate having a high-quality corundum-structured semiconductor film having excellent electrical characteristics.

At this time, the carbon source may contain any one or more of carbon monoxide, carbon dioxide, alcohol, ketone, carboxylic acid or organic metal complex.

This makes it possible to add carbon to the semiconductor film more stably.

At this time, the carbon source may contain any one or more of carbon monoxide gas, carbon dioxide gas, and hydrocarbon gas.

Thereby, the amount of carbon added to the semiconductor film can be adjusted with higher accuracy.

As described above, according to the present invention, it is possible to provide a high-quality semiconductor film having a corundum structure having excellent electrical characteristics and a laminate having the semiconductor film. Further, according to the present invention, a semiconductor film having a high-quality corundum structure having excellent electrical characteristics and a laminate having the semiconductor film can be easily produced at low cost.

It is a figure which shows one form of the structure of the laminated body which concerns on this invention. It is a figure which shows another form of the structure of the laminated body which concerns on this invention. It is a figure which shows typically a suitable example of the Schottky barrier diode (SBD) which concerns on this invention. It is a figure which shows typically a suitable example of the high electron mobility transistor (HEMT) which concerns on this invention. It is a figure which shows typically a suitable example of the metal oxide film semiconductor field effect transistor (PWM) which concerns on this invention. It is a figure which shows typically a suitable example of the insulated gate type bipolar transistor (IGBT) which concerns on this invention. It is a figure which shows typically a suitable example of the light emitting diode (LED) which concerns on this invention. It is a figure which shows typically another suitable example of the light emitting diode (LED) which concerns on this invention. It is a figure which shows typically a preferable example of the power-source system which concerns on this invention. It is a figure which shows typically a suitable example of the system apparatus which concerns on this invention. It is a figure which shows typically a preferable example of the power supply circuit diagram of the power supply apparatus which concerns on this invention. It is a figure which shows one form of the mist CVD apparatus used in the manufacturing method of the laminated body which concerns on this invention.

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

As described above, there has been a demand for a semiconductor film having a corundum structure having excellent electrical characteristics, a laminate containing the semiconductor film, and a method for producing the same.

As a result of diligent studies on the above problems, the present inventors have obtained a laminate including a crystal substrate and a semiconductor film containing a metal oxide having a corundum structure as a main component, in the film thickness direction of the semiconductor film. The average value of the carbon (C) concentration in the above is 1.0 × 10 ¹⁹ cm ^-3 or more and 1.0 × 10 ²¹ cm ^-3 or less, and the hydrogen (H) concentration in the film thickness direction of the semiconductor film is The present invention has been completed by finding that a laminate having an average value equal to or less than the average value of the carbon (C) concentration can provide a laminate having a high-quality semiconductor film having a corundum structure having excellent electrical characteristics.

Further, the present inventors have a semiconductor film containing a metal oxide having a corundum structure as a main component, and the average value of the carbon (C) concentration in the film thickness direction of the semiconductor film is 1.0 × 10 ¹⁹ cm. A semiconductor film having ^-3 or more, 1.0 × 10 ²¹ cm ^-3 or less, and an average value of hydrogen (H) concentration in the film thickness direction of the semiconductor film being equal to or less than the average value of carbon (C) concentration. As a result, we have found that it is possible to provide a high-quality semiconductor film having a corundum structure with excellent electrical characteristics, and completed the present invention.

Further, the present inventors supply an air-fuel mixture containing an atomized metal oxide precursor and a carrier gas to the heated crystal substrate, and the main component is a metal oxide having a corundum structure on the crystal substrate. A method for producing a laminate for forming a semiconductor film, wherein the air-fuel mixture contains a carbon source, and the content of the carbon source in the air-fuel mixture is the hydrogen (H) concentration in the film thickness direction of the semiconductor film. It has been found that a laminate having a high-quality semiconductor film having a corundum structure having excellent electrical characteristics can be produced by a method for producing a laminate having a content in which the average value of carbon (C) is equal to or less than the average value of the carbon (C) concentration. , The present invention has been completed.

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

(Semiconductor film and laminate having semiconductor film)
FIG. 1 is a diagram showing a semiconductor film according to the present invention and one form of a laminate having a semiconductor film. In the example of FIG. 1, the laminate 100 is composed of a crystal substrate 101 and a semiconductor film 102 directly formed on the crystal substrate 101.

The crystal substrate 101 is not particularly limited as long as it has a crystal structure on all or part of the main surface, and examples thereof include Si, Ge, Al ₂ O ₃ , Ga ₂ O ₃ , LiTaO ₃ , and NiO. Can be used. In the laminate according to the present invention, a substrate having a corundum structure on all or part of the main surface on the crystal growth surface side is particularly preferable, and α-Al ₂ O ₃ (sapphire) or α-Ga. ₂ O ₃ is preferably used. Further, in the laminated body according to the present invention, it is preferable that the main surface is the c-plane because the electrical characteristics can be further improved. Further, the crystal substrate 101 may have an off angle. In this case, it is generally better to set the off angle to 0.1 ° to 10.0 °. Here, the off angle indicates the smaller angle formed by the normal vector of the main surface (surface) of the crystal substrate and the normal vector of the low exponential surface. In this specification, the normal vector of the main surface (surface) of the crystal substrate and the crystal planes defined in FIG. 1 of SEMI M65-0306 (for example, c-plane, a-plane, m-plane, r-plane). The angle formed by the normal vector is compared, and the surface with the smallest angle is called the low exponential surface. In the laminate according to the present invention, when the crystal substrate has an off angle, it is preferable that the c-plane is the main surface.

The shape of the crystal substrate 101 is not particularly limited as long as it has a plate shape and serves as a support for the semiconductor film 102. It may also be substantially circular (eg, circular, oval, etc.) or polygonal (eg, triangle, square, rectangular, pentagon, hexagon, hexagon, octagon, nonagon, etc.). It may be present, and various shapes can be used. In the laminate according to the present invention, the shape of the semiconductor film 102 can be set by changing the shape of the crystal substrate 101 to a desired shape. Further, in the laminate according to the present invention, a large-area crystal substrate 101 having a main surface area of 10 cm ² or more, more preferably 20 cm ² or more can be used, and such a large-area crystal substrate 101 is used. Thereby, the area of the semiconductor film 102 can be increased. The thickness of the crystal substrate 101 is not particularly limited, but those having a thickness of 0.3 mm to 3 mm can be preferably used, and those having a thickness of 0.4 mm to 1 mm are more preferable. Within such a range, the warp due to residual stress is smaller and the crystallinity is higher.

The semiconductor film 102 contains an oxide semiconductor having a corundum structure as a main component, and further, the average carbon (C) concentration (hereinafter, simply referred to as “C concentration”) is 1.0 in the film thickness direction of the semiconductor film 102. It is × 10 ¹⁹ cm ^-3 or more and 1.0 × 10 ²¹ cm ^-3 or less. More preferably, it is 2.0 × 10 ¹⁹ cm ^-3 or more and 5.0 × 10 ²⁰ cm ^-3 or less. By using such a semiconductor film 102, the semiconductor film 102 is appropriately distorted, and the carrier mobility can be improved. If the C concentration is less than 1.0 × 10 ¹⁹ cm ^-3 , the effect of improving mobility cannot be sufficiently obtained, and if it exceeds 1.0 × 10 ²¹ cm ^-3 , the withstand voltage of the semiconductor decreases.

Further, in the film thickness direction of the semiconductor film 102, the average hydrogen (H) concentration (hereinafter, simply referred to as “H concentration”) is C concentration or less. When the H concentration exceeds the C concentration, crystal defects increase and the electrical characteristics of the semiconductor film deteriorate.

Here, the C concentration and the H concentration in the film film direction are quantitatively analyzed by SIMS in the film film direction (depth direction) for the elements (here, C and H) in the semiconductor film, and each element in the film film direction. It is a value obtained by calculating the average value of the concentration.

The expression "mainly composed of an oxide semiconductor" means that a dopant, an unavoidable impurity, or the like may be contained in addition to the oxide semiconductor. For example, the oxide semiconductor may be contained. It refers to those containing approximately 50% or more.

The mobility of charge carriers in the semiconductor film 102 is preferably 5 cm ² / Vs or more, more preferably 10 cm ² / Vs or more, and most preferably 20 cm ² / Vs or more. The mobility is the mobility obtained by measuring the Hall effect.

Further, in the semiconductor film according to the present invention and the laminate having the semiconductor film, the carrier density of the semiconductor film 102 is 1.0 × 10 ¹⁶ / cm ³ or more and 5.0 × 10 ²¹ / cm ³ or less. Is preferable. The carrier density refers to the carrier density in the semiconductor film obtained by the Hall effect measurement.

Further, it is preferable that the main surface of the semiconductor film 102 is the c-plane in that the crystallinity can be improved and, as a result, the electrical characteristics can be further improved.

Further, the semiconductor film 102 can be an oxide containing at least one of In, Ga, Al, Ir, V, Fe, Cr and Ti as a main component. It is most preferable to contain at least Ga or Al as the main component from the viewpoint of the electrical characteristics of the film. Regarding the "main component" here, for example, in the case of "containing at least Ga as the main component", it means that the atomic ratio of gallium in the metal element in the metal oxide is 0.5 or more. means.

The thickness of the semiconductor film 102 is not particularly limited, and is preferably 1 μm or more. By setting the film thickness to 1 μm or more, defects can be reduced and a higher quality film can be obtained.

Further, in the semiconductor film according to the present invention and the laminate having the semiconductor film, it is preferable that there are no cracks inside 10 mm from the outer peripheral edge of the substrate and inside 5 mm from the outer peripheral edge of the substrate when observing the film surface with an optical microscope. It is most preferable that there are no cracks in the film. Further, the semiconductor film according to the present invention may be a single crystal or a polycrystal film, but a single crystal film is preferable.

The dopant contained in the semiconductor film 102 is not particularly limited and may be a known one. Examples of the dopant include n-type dopants such as Sn, Ge, Si, Ti, Zr, V, Nb, or Pb, and p-type dopants such as Cu, Ag, Ir, and Rh. In the semiconductor film according to the present invention, Sn, Ge, or Si can be applied as the dopant, and Sn or Ge is more preferable, and Sn is most preferable. The dopant content of the semiconductor film may be from 1 × 10 ¹⁶ cm ^-3 to 1 × 10 ²² cm ^-3 , preferably from 1 × 10 ¹⁸ cm ^-3 to 5 × 10 ²¹ cm ^-3 . Within such a range, a resistance value sufficient for application to semiconductor devices can be obtained, and changes in physical properties due to narrowing of the energy band and degeneracy are more effectively suppressed, resulting in more stable electrical characteristics. Will have.

Although FIG. 1 shows an example in which the semiconductor film 102 is directly formed on the crystal substrate 101, the semiconductor film may be formed on another layer formed on the crystal substrate. In the laminate 200 shown in FIG. 2, a stress relaxation layer 203 is provided between the crystal substrate 201 and the semiconductor film 202. As a result, the lattice mismatch between the crystal substrate 201 and the semiconductor film 202 can be alleviated, and the electrical characteristics of the semiconductor film 202 can be further improved.

For example, when an α-Ga ₂ O ₃ film is formed on an Al ₂ O ₃ substrate, the stress relaxation layer 203 may be, for example, α-Fe ₂ O ₃ , α-Ga ₂ O ₃ , α-Al ₂ O ₃ and These mixed crystals and the like are preferably used. At this time, the lattice constant of the stress relaxation layer 203 is changed from a value close to or similar to the lattice constant of the crystal substrate 201 to a value close to or similar to the lattice constant of the semiconductor film 202 toward the growth direction of the stress relaxation layer 203. It is preferable to change it continuously or stepwise. That is, the stress relaxation layer 203 is formed of (Al _x Ga _1-x ) ₂ O ₃ (0 ≦ x ≦ 1), and the x value is reduced from the crystal substrate 201 side toward the semiconductor film 202 side. good.

The method for forming the stress relaxation layer 203 is not particularly limited, and may be a known method, and may be the same as the method for forming the semiconductor film 202. The stress relaxation layer 203 may or may not contain a dopant.

The semiconductor film according to the present invention not only has low resistance, but also has excellent electrical characteristics and is industrially useful. Such a semiconductor film can be suitably used for semiconductor devices and the like, and is particularly useful for power devices. For example, the semiconductor film according to the present invention is used for an n-type semiconductor layer (including an n ⁺ type semiconductor layer and an n ⁻ type semiconductor layer) of a semiconductor device. In the semiconductor device according to the present invention, the laminate having the semiconductor film may be used as it is, or it may be made into a single film by a known means such as peeling from the crystal substrate or the like, and then the semiconductor device or the like. May be applied to.

(Semiconductor device)
Semiconductor devices can be classified into horizontal elements (horizontal devices) in which electrodes are formed on one side of the semiconductor film and vertical elements (vertical devices) in which electrodes are provided on both the front and back sides of the semiconductor film. However, at least a part of the semiconductor film or laminate according to the present invention can be suitably used for both horizontal devices and vertical devices. In particular, 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 (MOS FET), and a junction field effect transistor (junction field effect transistor). JFET), an isolated gate type bipolar transistor (IGBT), a light emitting diode (LED), and the like.

A suitable example when the semiconductor film according to the present invention is applied to an n-type semiconductor layer (n ⁺ type semiconductor, n ^- type semiconductor layer, etc.) will be described with reference to the drawings. Not limited.

In the semiconductor device exemplified below, another layer (for example, an insulator layer or a conductor layer) may be further included depending on the specifications and purpose, and an intermediate layer and a buffer layer (buffer layer) may be included. ), The stress relaxation layer and the like may be added or omitted as appropriate.

FIG. 3 shows an example of a Schottky barrier diode (SBD). The SBD 300 includes an n ^- type semiconductor layer 301a with a relatively low concentration of doping, an n ⁺ type semiconductor layer 301b with a relatively high concentration of doping, a Schottky electrode 302, and an ohmic electrode 303.

The material of the Schottky electrode 302 and the ohmic electrode 303 may be a known electrode material, and examples of the electrode material include Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, and Au. , Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd or Ag or other metals or alloys thereof, tin oxide, zinc oxide, renium oxide, indium oxide, indium tin oxide ( Examples thereof include metal oxide conductive films such as ITO) and indium tin oxide (IZO), organic conductive compounds such as polyaniline, polythiophene or polypyrrol, or mixtures and laminates thereof.

The Schottky electrode 302 and the ohmic electrode 303 can be formed by a known means such as a vacuum vapor deposition method or a sputtering method. More specifically, for example, when a shotkey electrode is formed by using two kinds of the first metal and the second metal among the metals, it is composed of a layer made of the first metal and a second metal. It can be formed by laminating layers and performing patterning on a layer made of a first metal and a layer made of a second metal by using a photolithography technique.

When a reverse bias is applied to the SBD 300, the depletion layer (not shown) spreads in the n ^- type semiconductor layer 301a, so that the SBD 300 has a high withstand voltage. Further, when a forward bias is applied, electrons flow from the ohmic electrode 303 to the Schottky electrode 302. Therefore, the SBD 300 according to the present invention is excellent for high withstand voltage and large current, has a high switching speed, and is also excellent in withstand voltage and reliability.

FIG. 4 shows an example of a high electron mobility transistor (HEMT). The HEMT400 includes an n-type semiconductor layer 401 with a wide bandgap, an n-type semiconductor layer 402 with a narrow bandgap, an n + type semiconductor layer 403, a semi-insulator layer 404, a buffer layer 405, a gate electrode 406, a source electrode 407, and a drain electrode 408. It is equipped with.

FIG. 5 shows an example of a metal oxide film semiconductor field effect transistor (PWM). The MOSFET 500 includes an n ^- type semiconductor layer 501, an n ⁺ type semiconductor layer 502 and 503, a gate insulating film 504, a gate electrode 505, a source electrode 506, and a drain electrode 507.

FIG. 6 shows an example of an insulated gate bipolar transistor (IGBT). The IGBT 600 includes an n-type semiconductor layer 601, an n ^- type semiconductor layer 602, an n ⁺ type semiconductor layer 603, a p-type semiconductor layer 604, a gate insulating film 605, a gate electrode 606, an emitter electrode 607, and a collector electrode 608.

FIG. 7 shows an example of a light emitting diode (LED). The LED 700 includes a first electrode 701, an n-type semiconductor layer 702, a light emitting layer 703, a p-type semiconductor layer 704, a translucent electrode 705, and a second electrode 706.

Examples of the material of the translucent electrode 705 include a conductive material of an oxide containing In or 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. By providing these materials by a known means such as sputtering, the translucent electrode 705 can be formed. Further, after forming the translucent electrode 705, thermal annealing may be performed for the purpose of making the translucent electrode 705 transparent.

The materials of the first electrode 701 and the second electrode 706 include, for example, Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, and the like. 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 an organic conductive compound such as a metal oxide conductive film, polyaniline, polythiophene or polypyrrole, or a mixture 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 according to a method appropriately selected in consideration of suitability with the material from chemical methods such as a method.

Further, another aspect of the light emitting diode (LED) is shown in FIG. In the light emitting diode (LED) 800 of FIG. 8, the n-type semiconductor layer 801 is laminated on the substrate 806, and is exposed by cutting out a part of the p-type semiconductor layer 802, the light emitting layer 803, and the n-type semiconductor layer 801. The second electrode 804b is laminated on a part of the exposed surface of the semiconductor layer of the n-type semiconductor layer 801. A translucent electrode 805 and a first electrode 804a are provided on the upper portion of the p-type semiconductor layer 802.

(Semiconductor system)
The above semiconductor device is used for a semiconductor system, for example, a system using a power supply device. 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. 9 shows an example of a power supply system. In the example shown in FIG. 9, a power supply system is configured by using the plurality of power supply devices and control circuits. As shown in FIG. 10, 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. 11 shows a power supply circuit of a power supply device including a power circuit and a control circuit. In this power supply circuit, a DC voltage is switched at a high frequency by an inverter (composed of MOSFETs A to D), converted to AC, and then transformed into a transformer. Insulation and transformation are performed, rectified by a rectifying MOSFET (A to B), smoothed by a DCL (smoothing coils L1 and L2) and a capacitor, and a DC voltage is output. At this time, the output voltage is compared with the reference voltage by the voltage comparator, and the inverter and the rectifier MOSFET are controlled by the PWM control circuit so as to obtain the desired output voltage.

(Manufacturing method of semiconductor film and laminate)
Next, an example of the method for manufacturing a semiconductor film and a laminate according to the present invention described with reference to FIG. 1 will be described with reference to the film forming apparatus shown in FIG. 12, but the present invention is limited thereto. It's not something.

In the method for producing a semiconductor film and a laminate according to the present invention, a mixture containing an atomized metal oxide precursor and a carrier gas is supplied to a heated crystal substrate to have a corundum structure on the crystal substrate. When forming a semiconductor film containing a metal oxide as a main component, the air-fuel mixture contains a carbon source, and the content of the carbon source in the air-fuel mixture is the hydrogen (H) concentration in the film thickness direction of the semiconductor film. It is characterized in that the content is such that the average value of carbon (C) is equal to or less than the average value of the carbon (C) concentration.

FIG. 12 shows an example of a film forming apparatus that can be used in the method for producing a semiconductor film and a laminate according to the present invention. In carrying out the method for manufacturing a semiconductor film and a laminate according to the present invention, a mist CVD apparatus 900 is used. The atomizers 902a and 902b contain the first precursor 912a and the second precursor 912b as raw material solutions, respectively, and are atomized (also referred to as "mistification") by a known means. , Mist is formed.

Further, the mist CVD apparatus 900 includes a means for supplying the carrier gas 901. The carrier gas 901 is mixed with the atomized raw material solution (precursor) formed in the atomizers 902a and 902b to form an air-fuel mixture, and is conveyed to the film forming chamber 909. The air-fuel mixture supplied to the film-forming chamber 909 reacts in the film-forming chamber 909 on the crystal substrate 907 heated by the heat source 910 to form a semiconductor having a corundum structure. In addition, valves 904, 905 and the like can be appropriately installed in the piping.

In the example shown in FIG. 12, a structure is shown in which the atomizer 902b and the film forming chamber 909 are connected by a transfer pipe 906, and the transfer pipe 903 from the atomizer 902a joins in the middle of the transfer pipe 906. However, the transfer pipe 903 and the transfer pipe 906 may be independently connected to the film forming chamber 909. Further, not limited to this, even if the first air-fuel mixture 913 and the second air-fuel mixture 923 are introduced into a single buffer tank (not shown in the figure) and the mist mixed in the buffer tank is conveyed to the film forming chamber 909. good.

The transfer pipes 903 and 906 are not particularly limited as long as they have sufficient stability with respect to the solvent of the precursor and the temperature in the connection between the reactor and the transfer pipe, and are not particularly limited, and are quartz, polyethylene, polypropylene, vinyl chloride, and silicone. General resin pipes such as resin, urethane resin, and fluororesin can be widely used.

The material, structure, etc. of the film-forming chamber 909 are not particularly limited, and metals such as aluminum and stainless steel may be used, and quartz is used when film-forming is performed at a higher temperature exceeding the heat-resistant temperature of these metals. Or silicon carbide may be used. A heating means 910 for heating the crystal substrate 907 is provided inside or outside the film forming chamber 909. Further, the crystal substrate 907 may be placed on the susceptor 908 installed in the film forming chamber 909.

Examples of the first precursor 912a and the second precursor 912b include an acid solution in which a metal is dissolved in an acid, a metal halide (for example, fluoride, chloride, bromide, iodide, etc.), or a hydroxide. Examples include an aqueous solution of hydrate. The metal is not limited as long as it is a metal capable of forming a corundum structure as a metal oxide crystal, and examples thereof include Al, Ti, V, Cr, Fe, Ga, Rh, In, and Ir. The content of the metal in the raw material solution is not particularly limited and can be appropriately set according to the purpose and specifications. It is preferably 0.001 mol / L or more and 2 mol / L or less, and more preferably 0.01 mol / L or more and 0.7 mol / L or less. Further, the components of the first precursor 912a and the second precursor 912b may be the same or different.

The conductivity of the semiconductor film can be adjusted (imparted) by impurity doping. The impurity raw material in this case is not particularly limited. For example, when the metal contains at least Ga, a complex or compound containing Si, Ge or Sn can be preferably used, and tin halide is particularly preferable. These impurity raw materials can be mixed with 0.0001% to 20%, more preferably 0.001% to 10% with respect to the concentration of the metal element in the raw material solution.

The atomization of the raw material solution is not particularly limited as long as the raw material solution can be atomized or atomized, and may be a known means, but an atomizing means using ultrasonic waves is preferable. The mist or droplet obtained by using ultrasonic waves has a zero initial velocity and is preferable because it floats in the air. For example, it can float in space and be transported as a gas instead of being sprayed like a spray. Since it is a mist, it is very suitable because it is not damaged by collision energy. The droplet size is not particularly limited and may be a droplet of about several mm or less, but is preferably 50 μm or less, and more preferably 0.1 to 10 μm. Further, the number of atomizers and the type of precursor can be increased or decreased depending on the composition of the film formed on the crystal substrate and the laminated structure.

The carrier gas 901 is not particularly limited, and for example, in addition to air, oxygen, and ozone, an inert gas such as nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas is preferably used. The type of carrier gas may be one type or two or more types. The flow rate of the carrier gas may be appropriately set depending on the size of the substrate and the size of the film forming chamber, and can be about 0.01 to 100 L / min.

Further, although not shown, it is also possible to add a diluting gas to adjust the ratio of the atomized raw material to the carrier gas. The flow rate of the diluted gas may be appropriately set, and may be, for example, 0.1 to 10 times / min of the carrier gas. The diluted gas may be supplied to, for example, the downstream side of the atomizers 902a and 902b. As the diluting gas, the same one as the carrier gas may be used, or a different one may be used.

The temperature of the crystal substrate when forming a semiconductor film should be appropriately determined depending on the film type formed on the crystal substrate. For example, when forming an α-Ga ₂ O ₃ film, the temperature is 350 ° C. or higher and 950 ° C. It is better to do the following. Within such a temperature range, a semiconductor film having higher crystal quality can be obtained. The film thickness can be adjusted by adjusting the film formation time, the spray amount of the precursor, and the carrier gas flow rate.

Further, the film formation may be performed under any conditions of atmospheric pressure, pressurization, and decompression, but it is preferably performed under atmospheric pressure from the viewpoint of equipment cost and productivity.

When further forming a stress relaxation layer between the semiconductor film and the crystal substrate, first, a first air-fuel mixture in which the carrier gas 901 and the atomized first precursor 912a formed by the atomizer 902a are mixed. 913 is formed, and further, the carrier gas 901 and the atomized second precursor 912b formed by the atomizer 902b are mixed to form a second air-fuel mixture 923.

Next, the first air-fuel mixture 913 and the second air-fuel mixture 923 are placed on the susceptor 908 in the film forming chamber 909 and transported onto the crystal substrate 907 heated by the heating means 910, whereby the precursor is transferred to the substrate surface. A semiconductor film having a corundum structure is formed in which the components of the first precursor 912a and the components of the second precursor 912b are mixed. Here, the carrier gas flow rates of both or one of the first air-fuel mixture 913 and the second air-fuel mixture 923 may be changed discretely or continuously over a predetermined time. For example, when a stress relaxation layer is formed between a sapphire substrate and α-Ga ₂ O ₃ , the stress relaxation layer is formed by (Al _x Ga _1-x ) ₂ O ₃ (0 ≦ x ≦ 1), and the crystal substrate is formed. It is better to reduce the x value from the side to the growth direction side. For this purpose, when the first air-fuel mixture 913 containing the Al source and the second air-fuel mixture 923 containing the Ga source are supplied to the film forming chamber 909, the Al supply amount is relatively larger than the Ga supply amount. , Adjust the concentration of each precursor and the flow rate of carrier gas. Separately from this, the first film formation was performed with an air-fuel mixture using an Al-Ga precursor in which an Al source and a Ga source were mixed at a certain ratio, and then the Al concentration was reduced in a relative and stepwise manner. The lamination may be repeated using the Al—Ga precursor of (Al _x Ga _1-x ) to form a _{2O 3} multilayer film in which the Al composition is gradually reduced. The temperature of the crystal substrate at this time should be appropriately determined depending on the film type formed on the crystal substrate. For example, a (Al _x Ga _1-x ) ₂ O ₃ (0 ≦ x ≦ 1) film. It is preferable that the temperature is 350 ° C. or higher and 950 ° C. or lower. Within such a temperature range, a stress relaxation layer having higher crystal quality can be obtained. The film thickness can be adjusted by adjusting the film formation time.

In the method for producing a semiconductor film and a laminate according to the present invention, a carbon source is contained in the air-fuel mixture so that the content of the carbon source in the air-fuel mixture is such that the H concentration in the film thickness direction of the semiconductor film is C concentration or less. The content shall be. As a method for incorporating a carbon source into the air-fuel mixture, it is preferable to add a carbon compound as a carbon source to either or both of the above-mentioned first precursor 912a and the second precursor 912b. Examples of the carbon source in this case include an organic complex of a metal selected from the above metal group and a carbon compound such as carbon monoxide, carbon dioxide, alcohol, ketone, and carboxylic acid, but more preferably the acetylacetone complex of the above metal. Is better to use. This makes it possible to add carbon to the air-fuel mixture more stably. The amount of the carbon source added varies depending on the carbon source used, but for example, when a metal acetylacetone complex is used, it is preferable to add about 0.001 mol / L to 0.7 mol / L to the precursor solution.

As the carbon source, in addition to the method of adding to the precursor solution as described above, the carbon source solution containing only the carbon source as the solute is adjusted to the same concentration as the above, and then independently atomized to form the precursor. It can be mixed with mist and used.

In the above, the method of adding the carbon source to the raw material solution has been described, but separately from this, the carbon source may be added or replaced with the carrier gas or the diluted gas. The carbon source in this case is not particularly limited, but for example, carbon monoxide gas, carbon dioxide gas or hydrocarbon gas is preferably used, and more preferably carbon dioxide gas is used. If it is a gaseous carbon source, the C concentration in the semiconductor film can be adjusted with high accuracy. In this case, it is preferable to mix the carbon dioxide gas at a ratio of 0.5% to 90% by volume in the total flow rate of the carrier gas and the diluted gas, and more preferably 10% or more and 65%. Is good.

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

(Example 1)
In the mist CVD apparatus of FIG. 12, an apparatus equipped with only one atomizer was used. Then, a film of gallium oxide was formed by the following procedure. First, gallium chloride was dissolved in pure water to prepare an aqueous solution having a Ga concentration of 0.10 mol / L. Tin (II) chloride was added to this aqueous solution so that the atomic ratio of Sn to the Ga concentration was 1: 0.005, and 0.01 mol / L of gallium acetylacetonate was added to pure water. This was used as a raw material solution and filled in an atomizer.

Next, a c-plane sapphire substrate having a diameter of 2 inches (50 mm) was placed on a quartz susceptor and placed in a quartz tubular film-forming chamber, and the substrate temperature was maintained 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 5.0 L / min to form an air-fuel mixture, which is supplied to the membrane-forming chamber to atmospheric pressure. A film was formed underneath for 60 minutes to form an α-Ga ₂ O ₃ film having a thickness of 1.5 μm.

Then, the substrate was cooled to room temperature and then taken out from the film forming chamber, and the carrier concentration, resistivity and mobility were measured by the Van der Pauw method (accent HL5500). In addition, the C concentration and the H concentration in the membrane were measured by SIMS (CAMECA IMS-7f).

(Example 2)
In the mist CVD apparatus of FIG. 12, an apparatus equipped with only one atomizer was used. Then, a film of gallium oxide was formed by the following procedure. First, gallium chloride was dissolved in pure water to prepare an aqueous solution having a Ga concentration of 0.10 mol / L. Tin (II) chloride was added to this aqueous solution so that the atomic ratio of Sn to the Ga concentration was 1: 0.005, and this was used as a raw material solution and filled in an atomizer.

Next, a c-plane sapphire substrate having a diameter of 2 inches (50 mm) was placed on a quartz susceptor and placed in a quartz tubular film-forming chamber, and the substrate temperature was maintained 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 as a carrier gas is introduced into the atomizer at 1.5 L / min and carbon dioxide as a diluent gas is introduced at 5.0 L / min to form an air-fuel mixture, which is supplied to the membrane-forming chamber. A film was formed under atmospheric pressure for 60 minutes to form an α-Ga ₂ O ₃ film having a thickness of 1.5 μm.

After that, the substrate was cooled to room temperature and then taken out from the film forming chamber, and the carrier concentration, resistivity, mobility, and C concentration and H concentration in the film were measured in the same manner as in Example 1.

(Comparative Example 1)
In the mist CVD apparatus of FIG. 12, an apparatus equipped with only one atomizer was used. Then, a film of gallium oxide was formed by the following procedure. First, gallium chloride was dissolved in pure water to prepare an aqueous solution having a Ga concentration of 0.10 mol / L. Tin (II) chloride was added to this aqueous solution so that the atomic ratio of Sn to the Ga concentration was 1: 0.005, and this was used as a raw material solution and filled in an atomizer.

Next, a c-plane sapphire substrate having a diameter of 2 inches (50 mm) was placed on a quartz susceptor and placed in a quartz tubular film-forming chamber, and the substrate temperature was maintained at 430 ° 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 5.0 L / min to form an air-fuel mixture, which is supplied to the membrane-forming chamber. A film was formed under pressure for 60 minutes to form an α-Ga ₂ O ₃ film having a film thickness of 1.5 μm.

After that, the substrate was cooled to room temperature and then taken out from the film forming chamber, and the carrier concentration, resistivity, mobility, and C concentration and H concentration in the film were measured in the same manner as in Example 1.

(Comparative Example 2)
In Example 1, a film was formed under the same conditions except that gallium acetylacetonate was added to pure water at 0.1 mol / L to prepare a raw material solution, and the same evaluation as in Example 1 was performed.

(Comparative Example 3)
In Example 2, carbon dioxide was introduced as a diluting gas at 1.5 L / min to form an air-fuel mixture, and the film was formed under the same conditions, and the same evaluation as in Example 2 was performed.

Table 1 shows the carrier density, mobility and resistivity of the semiconductors obtained in Examples 1 and 2 and Comparative Example 1-3. As shown in Examples 1 and 2, it can be seen that the semiconductor film according to the present invention has low resistance and high mobility and is excellent in electrical characteristics. On the other hand, in Comparative Example 1 in which the carbon mixture was not contained in the air-fuel mixture, the mobility of the semiconductor film was low. Further, as shown in Comparative Example 2, even if the C concentration was equivalent to the C concentration of the semiconductor film according to the present invention, the mobility of the semiconductor film was low when the C concentration <H concentration. Further, as shown in Comparative Example 3, the mobility of the semiconductor film was also low when the C concentration was higher than the C concentration of the semiconductor film according to the present invention.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and the present invention can be anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same function and effect. Is included in the technical scope of.

100 ... Laminated body, 101 ... Crystal substrate, 102 ... Semiconductor film,
200 ... Laminate, 201 ... Crystal substrate, 202 ... Semiconductor film,
203 ... Stress relaxation layer,
300 ... Schottky barrier diode (SBD), 301a ... n ^- type semiconductor layer,
301b ... n ⁺ type semiconductor layer, 302 ... Schottky electrode,
303 ... Ohmic electrode,
400 ... High electron mobility transistor (HEMT), 401 ... n-type semiconductor layer,
402 ... n-type semiconductor layer, 403 ... n ⁺ type semiconductor layer, 404 ... semi-insulator layer,
405 ... Buffer layer, 406 ... Gate electrode, 407 ... Source electrode,
408 ... Drain electrode,
500 ... Metal oxide film semiconductor field effect transistor (PWM),
501 ... n ^- type semiconductor layer, 502 ... n ⁺ type semiconductor layer, 503 ... n ⁺ type semiconductor layer,
504 ... Gate insulating film, 505 ... Gate electrode, 506 ... Source electrode,
507 ... Drain electrode,
600 ... Insulated gate type bipolar transistor (IGBT),
601 ... n-type semiconductor layer, 602 ... n ^- type semiconductor layer, 603 ... n ⁺ type semiconductor layer,
604 ... p-type semiconductor layer, 605 ... gate insulating film, 606 ... gate electrode,
607 ... Emitter electrode, 608 ... Collector electrode,
700 ... Light emitting diode (LED), 701 ... First electrode,
702 ... n-type semiconductor layer, 703 ... light emitting layer, 704 ... p-type semiconductor layer,
705 ... Translucent electrode, 706 ... Second electrode,
800 ... Light emitting diode (LED), 801 ... n-type semiconductor layer,
802 ... p-type semiconductor layer, 803 ... light emitting layer, 804a ... first electrode,
804b ... second electrode, 806 ... substrate,
900 ... mist CVD device, 901 ... carrier gas, 902a ... atomizer,
902b ... atomizer, 903 ... transfer piping, 904 ... valve,
905 ... Valve, 906 ... Conveying piping, 907 ... Crystal substrate, 908 ... Suceptor,
909 ... Film forming chamber, 910 ... Heating means, 912a ... First metal oxide precursor,
912b ... Second metal oxide precursor, 913 ... First air-fuel mixture, 923 ... Second air-fuel mixture.

Claims (13)

A laminate containing a crystal substrate and a semiconductor film containing a metal oxide having a corundum structure as a main component.
The average value of the carbon (C) concentration in the film thickness direction of the semiconductor film is 1.0 × 10 ¹⁹ cm ^-3 or more, 1.0 × 10 ²¹ cm ^-3 or less, and the semiconductor film film thickness direction. The laminate is characterized in that the average value of the hydrogen (H) concentration in the above is equal to or less than the average value of the carbon (C) concentration. The laminate according to claim 1, wherein the average value of the carbon (C) concentration is 2.0 × 10 ¹⁹ cm ^-3 or more and 5.0 × 10 ²⁰ cm ^-3 or less. The laminate according to claim 1 or 2, wherein the carrier mobility in the semiconductor film is 5 cm ² / Vs or more. The laminate according to any one of claims 1 to 3, wherein the carrier density in the semiconductor film is 1.0 × 10 ¹⁶ / cm ³ or more and 1.0 × 10 ²¹ / cm ³ or less. .. The laminate according to any one of claims 1 to 4, wherein the metal oxide contains a Ga oxide or an Al oxide. The laminate according to any one of claims 1 to 5, wherein the area of the main surface of the crystal substrate is 10 cm ² or more. The laminate according to any one of claims 1 to 6, wherein the semiconductor film has a film thickness of 1 μm or more. A semiconductor film containing a metal oxide having a corundum structure as a main component.
The average value of the carbon (C) concentration in the film thickness direction of the semiconductor film is 1.0 × 10 ¹⁹ cm ^-3 or more, 1.0 × 10 ²¹ cm ^-3 or less, and the semiconductor film film thickness direction. The semiconductor film is characterized in that the average value of the hydrogen (H) concentration in the above is equal to or less than the average value of the carbon (C) concentration. A semiconductor device including at least a semiconductor film and electrodes, wherein the semiconductor film includes the semiconductor film according to claim 8. A semiconductor system comprising the semiconductor device according to claim 9. A laminate containing an atomized metal oxide precursor and a carrier gas is supplied to a heated crystal substrate to form a semiconductor film containing a metal oxide having a corundum structure as a main component on the crystal substrate. It ’s a method of manufacturing the body.
The air-fuel mixture contains a carbon source and contains
The content of the carbon source in the air-fuel mixture is characterized in that the average value of the hydrogen (H) concentration in the film thickness direction of the semiconductor film is equal to or less than the average value of the carbon (C) concentration. Method for manufacturing a laminate. The method for producing a laminate according to claim 11, wherein the carbon source contains any one or more of carbon monoxide, carbon dioxide, alcohol, ketone, carboxylic acid, and an organic metal complex. The method for producing a laminate according to claim 11 or 12, wherein the carbon source contains any one or more of carbon monoxide gas, carbon dioxide gas, and hydrocarbon gas.

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