WO2019098294A1

WO2019098294A1 - P-type oxide semiconductor film formation method

Info

Publication number: WO2019098294A1
Application number: PCT/JP2018/042345
Authority: WO
Inventors: 勲 ▲高▼橋; 時宜松田; 四戸　孝
Original assignee: 株式会社Flosfia
Priority date: 2017-11-15
Filing date: 2018-11-15
Publication date: 2019-05-23
Also published as: TW201934818A

Abstract

Provided is a formation method that makes it possible to industrially advantageously form a p-type oxide semiconductor film that has excellent semiconductor characteristics. According to the present invention, a metal oxide gas that has been obtained by heating and sublimating a solid body of a metal oxide (such as iridium oxide) is used as a raw material to grow crystals on a base (such as a sapphire substrate) and form a p-type oxide semiconductor film that has a corundum structure, a film thickness of at leaset 50 nm, and a surface roughness of no more than 10 nm.

Description

Method of forming p-type oxide semiconductor film

The present invention relates to a method for forming a p-type oxide semiconductor.

A semiconductor device using gallium oxide (Ga ₂ O ₃ ) with a large band gap has attracted attention as a next-generation switching element capable of achieving high withstand voltage, low loss, and high heat resistance, and is used for power semiconductor devices such as inverters. Application is expected. Moreover, application as a light emitting and receiving device such as an LED or a sensor is also expected from a wide band gap. According to Non-Patent Document 1, the gallium oxide can be band gap controlled by mixing crystal with indium or aluminum respectively or in combination, and constitutes an extremely attractive material family as an InAlGaO-based semiconductor. . Here, the InAlGaO based semiconductor _In X _Al Y _Ga Z _O 3 indicates (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5 ~ 2.5), gallium oxide It can be regarded as the same material system to be contained.

In recent years, gallium oxide based p-type semiconductors have been studied. For example, in Patent Document 1, a β-Ga ₂ O ₃ based crystal is subjected to FZ method using MgO (p-type dopant source). It is described that when formed, a substrate exhibiting p-type conductivity is obtained. Further, Patent Document 2 describes that a p-type semiconductor is formed by ion-implanting a p-type dopant into an α- (Al _x Ga _{1 -x} ) ₂ O ₃ single crystal film formed by MBE. . However, in these methods, it is difficult to realize the production of p-type semiconductors (Non-patent Document 2), and it has not been reported that these methods succeeded in producing p-type semiconductors. Therefore, a viable p-type oxide semiconductor and a method for producing the same have been desired.

Further, as described in Non-Patent Document 3 and Non-Patent Document 4, for example, using Rh ₂ O ₃ or ZnRh ₂ O ₄ as a p-type semiconductor has been studied, but Rh ₂ O ₃ There is a problem that the concentration of the raw material becomes particularly thin at the time of film formation, which affects the film formation, and it was difficult to prepare a Rh ₂ O ₃ single crystal even using an organic solvent. Also, there is a problem that even if the Hall effect measurement is performed, the p type is not determined and the measurement itself can not be performed, and the measurement value of the Hall coefficient is, for example, 0.2 cm ³ / C) There was only the following, and it was not enough to use it. In addition, since ZnRh ₂ O ₄ has a low mobility and a narrow band gap, there is a problem that it can not be used for an LED or a power device, and these were not necessarily satisfactory.

In addition to Rh ₂ O ₃ and ZnRh ₂ O _4, etc., various p-type oxide semiconductors have been studied as wide band gap semiconductors. Patent Document 3 describes that delafossite, oxychalcogenide or the like is used as a p-type semiconductor. However, these semiconductors have mobility of about 1 cm ² / V · s or less, have poor electrical characteristics, and have pn junctions with n-type next-generation oxide semiconductors such as α-Ga ₂ O _3. There was also a problem that did not work well.

Note that Ir ₂ O ₃ is conventionally known. For example, Patent Document 4 describes using Ir ₂ O ₃ as an iridium catalyst. Patent Document 5 describes that Ir ₂ O ₃ is used as a dielectric. In addition, Patent Document 6 describes using Ir ₂ O ₃ for the electrode. However, although it was not known to use Ir ₂ O ₃ for p-type semiconductors, recently, the applicants have studied using Ir ₂ O ₃ as a p-type semiconductor, and development is advanced. It is done.

JP 2005-340308 A JP, 2013-58637, A JP, 2016-25256, A Unexamined-Japanese-Patent No. 9-25255 JP-A-8-227793 Japanese Patent Application Laid-Open No. 11-21687

An object of the present invention is to provide a method capable of industrially advantageously forming a p-type oxide semiconductor film excellent in semiconductor characteristics.

As a result of intensive studies to achieve the above object, the present inventors used metal oxide gas as a raw material for forming a p-type oxide semiconductor film, so that the film thickness is 50 nm or more even though it is not amorphous. Have been found that a p-type oxide semiconductor film having a surface roughness of 10 nm or less can be formed, and such a p-type oxide semiconductor film can solve the aforementioned conventional problems at once. Found out.

Furthermore, after obtaining the above-mentioned findings, the present inventors repeated studies and completed the present invention. That is, the present invention relates to the following inventions.
[1] A method of forming a p-type oxide semiconductor film, wherein a metal oxide gas is used as a raw material for forming the p-type oxide semiconductor film.
[2] The method according to the above [1], wherein the metal oxide gas contains a d-block metal of the periodic table or a periodic group 13 metal.
[3] The method of forming a p-type oxide semiconductor film according to the above [1] or [2], wherein the metal oxide gas contains a periodic table group 9 metal or a group 13 metal.
[4] The method for forming a p-type oxide semiconductor film according to any one of the above [1] to [3], wherein the metal oxide gas contains at least iridium.
[5] The p-type oxide semiconductor film according to any one of the above [1] to [4], wherein the metal oxide gas is obtained by sublimation of a solid of the metal oxide gas by heating. Formation method.
[6] The method for forming a p-type oxide semiconductor film according to any one of the above [1] to [5], wherein the formation of the p-type oxide semiconductor film is performed under atmospheric pressure.
[7] The method for forming a p-type oxide semiconductor film according to any one of the above [1] to [6], wherein the formation of the p-type oxide semiconductor film is performed by crystal growth.
[8] The method for forming a p-type oxide semiconductor film according to the above [7], wherein the crystal growth is performed on a substrate having a corundum structure.
[9] A method for forming a metal oxide film, which is a method for forming a metal oxide film, comprising forming a metal oxide film, the metal oxide gas containing a periodic table group 9 and / or periodic table group 13 metal in an oxygen atmosphere A method of forming a metal oxide film characterized by performing a thermal reaction on a substrate.
[10] The method for forming a metal oxide film according to the above [9], wherein the metal oxide gas contains a p-type dopant.
[11] The method for forming a metal oxide film according to the above [9] or [10], wherein the metal oxide gas at least contains a metal of Group 13 of the periodic table.
[12] The method for forming a metal oxide film according to any one of the above [9] to [11], wherein the metal oxide gas contains at least iridium.

The method for forming a p-type oxide semiconductor film of the present invention can industrially advantageously form a p-type oxide semiconductor film excellent in semiconductor characteristics.

It is a schematic block diagram of the film-forming apparatus used in an Example. It is a schematic block diagram of the film-forming apparatus (mist CVD apparatus) used in a comparative example. It is a figure which shows the XRD measurement result in an Example and a comparative example. The horizontal axis represents diffraction angle (deg.), And the vertical axis represents diffraction intensity (arb. Unit). It is a figure which shows the AFM surface observation result in an Example. It is a figure which shows the AFM surface observation result in a comparative example. It is a figure which shows the observation result of cross-sectional SEM, (a) shows the observation result of cross-sectional SEM of an Example, (b) shows the observation result of cross-sectional SEM of a comparative example. It is a figure which shows the result of IV measurement in an Example. It is a schematic block diagram of the film-forming apparatus used in an Example. It is a schematic block diagram of the film-forming apparatus used in an Example. It is a figure which shows the XRD measurement result in an Example. The horizontal axis represents the diffraction angle (deg.), And the vertical axis represents the diffraction intensity (arb. Unit.). It is a figure which shows the XRD measurement result in an Example. The horizontal axis represents the diffraction angle (deg.), And the vertical axis represents the diffraction intensity (arb. Unit.).

The method for forming a p-type oxide semiconductor film of the present invention is a method for forming a p-type oxide semiconductor film, characterized in that a metal oxide gas is used as a raw material for forming the p-type oxide semiconductor film. Do. More specifically, for example, a solid substance (such as powder) of metal oxide gas is sublimated (sublimation step), and then the resulting metal oxide gas is used to grow crystals on a substrate having a corundum structure. (Crystal growth process).

(Sublimation process)
In the sublimation process, a metal oxide gas is obtained by subliming a solid substance (for example, powder or the like) of the metal oxide gas into a gaseous state. Examples of the metal oxide gas include metal oxides of metals contained in a gaseous p-type oxide semiconductor film, and the valence of the metal oxide does not hinder the object of the present invention. It is not particularly limited, and may be monovalent or divalent. It may be trivalent or tetravalent. In the present invention, the metal oxide preferably contains the d block metal of the periodic table or the periodic table group 13 metal, and more preferably includes the periodic table group 9 metal or the group 13 metal. preferable. In the case where the p-type oxide semiconductor film contains mixed crystals, the metal oxide may be iridium, and a metal of Group 2 of the periodic table, a metal of Group 9 other than iridium, or a metal of Group 13 It is also preferable to contain. By using a preferable metal oxide as described above, one having a band gap of 2.4 eV or more can be obtained, so that a wider band gap and more excellent electric characteristics can be exhibited in the p-type oxide semiconductor. it can.

In addition, "periodic table" means the periodic table defined by International Union of Pure and Applied Chemistry (IUPAC). "D block" refers to an element having electrons that satisfy 3d, 4d, 5d and 6d orbitals. Examples of the d-block metal include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper. (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), laurenthium (Lr), razarhodium (Rf), dubnium (Db), seaborgium (Sg), boli Beam (Bh), hassium (Hs), meitnerium (Mt), darmstadtium (Ds), roentgenium (Rg), including Copernicium (Cn) and two or more metals thereof.

In addition, “group 2 metal” may be any group 2 metal of the periodic table, and examples of the group 2 metal include beryllium (Be), magnesium (Mg), calcium (Ca), and strontium Sr), barium (Ba), or two or more of these metals, and the like. The “group 9 metal” may be a group 9 metal of the periodic table, and such a group 9 metal includes, for example, iridium (Ir), cobalt (Co), rhodium (Rh) or these And the like. The “group 13 metal” is not particularly limited as long as it is a group 13 metal of the periodic table, and examples of the group 13 metal include aluminum (Al), gallium (Ga), indium (In), and the like. Although thallium (Tl) or two or more of these metals and the like can be mentioned, in the present invention, one or more selected from aluminum (Al), gallium (Ga) and indium (In) are preferable.

In the present invention, when the p-type oxide semiconductor film contains a metal oxide containing iridium as a main component, it is preferable to use IrO ₂ gas as the metal oxide gas. A heating means is mentioned as a sublimation means. The heating temperature is not particularly limited, but is preferably 600 ° C. to 1200 ° C., more preferably 800 ° C. to 1000 ° C. In the present invention, the metal oxide gas obtained by sublimation is preferably transported to the substrate by the carrier gas. The type of carrier gas is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include oxygen, ozone, inert gases such as nitrogen and argon, and reducing gases such as hydrogen gas and forming gas. In the present invention, it is preferable to use oxygen as a carrier gas. As a carrier gas in which oxygen is used, air, oxygen gas, ozone gas etc. are mentioned, for example, Especially oxygen gas and / or ozone gas are preferred. In addition, although one kind of carrier gas may be used, it may be two or more kinds, and a dilution gas (for example, 10-fold dilution gas etc.) in which the carrier gas concentration is changed may be used as the second carrier gas. You may use further. Further, the carrier gas may be supplied not only to one place, but also to two or more places. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min and more preferably 0.1 to 10 L / min.

The substrate is not particularly limited as long as it can support the p-type oxide semiconductor film, but preferably has a corundum structure. The material of the substrate may be a known substrate, may be an organic compound, or may be an inorganic compound. As a base material, for example, a metal oxide having a corundum structure such as sapphire or α-type gallium oxide can be mentioned as a preferable example. The shape of the substrate may be any shape, and is effective for any shape, for example, plate-like such as flat plate or disc, fiber-like, rod-like, cylindrical, prismatic, Although cylindrical shape, helical shape, spherical shape, ring shape etc. are mentioned, a substrate is preferable in the present invention. The thickness of the substrate is not particularly limited in the present invention.

The substrate is not particularly limited as long as it has a plate shape and serves as a support for the p-type oxide semiconductor film. The substrate may be an insulator substrate, a semiconductor substrate, or a conductive substrate, but the substrate is preferably an insulator substrate and has a metal film on the surface. It is also preferred that it is a substrate. The substrate preferably includes, for example, a substrate having a corundum structure. The substrate material is not particularly limited as long as it has a corundum structure, and may be known. Examples of the substrate having the corundum structure include a base substrate mainly composed of a substrate material having a corundum structure, and more specifically, for example, a sapphire substrate (preferably c-plane sapphire substrate) or an α-type A gallium oxide substrate etc. are mentioned. Here, “main component” means that the substrate material having the above-mentioned specific crystal structure is, in atomic ratio, preferably 50% or more, more preferably 70% or more, still more preferably 90% to all components of the substrate material. It means that% or more is included, and it may mean that it may be 100%.

(Crystal growth process)
In the crystal growth step, the metal oxide gas is crystal-grown near the surface of the substrate, and a film is formed on part or all of the surface of the substrate. The crystal growth temperature is preferably lower than the heating temperature of the sublimation process, more preferably 900 ° C. or less, and most preferably 500 ° C. to 900 ° C. In addition, crystal growth may be performed under any atmosphere of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxidizing atmosphere, as long as the object of the present invention is not hindered. Although it may be carried out under any conditions of reduced pressure and reduced pressure, in the present invention, it is preferable to be carried out under an oxidizing atmosphere, preferably under atmospheric pressure, preferably under an oxidizing atmosphere and under atmospheric pressure. More preferably, The “oxidative atmosphere” is not particularly limited as long as it is an atmosphere in which crystals or mixed crystals of metal oxides can be formed, and it may be any oxygen or oxygen-containing compound, for example, a carrier gas containing oxygen. An oxidizing atmosphere may be used by using or using an oxidizing agent. The film thickness can be set by adjusting the film formation time. In the present invention, it is preferably 50 nm or more, more preferably 100 nm or more, and most preferably 1.0 μm or more. The upper limit of the film thickness is not particularly limited, but is preferably 1 mm, and more preferably 100 μm. In the present invention, the metal oxide gas may be added to a p-type dopant to be subjected to this step, and the metal oxide having the corundum structure may be p-type doped. As the p-type dopant, for example, Mg, H, Li, Na, K, Rb, Cs, Fr, Be, Ca, Sr, Ba, Ra, Mn, Fe, Co, Ni, Pd, Cu, Ag, Au And Zn, Cd, Hg, Tl, Pb, N, P and the like, and two or more of these elements and the like. In the present invention, the p-type dopant is preferably a Group 1 metal or a Group 2 metal of the periodic table, more preferably a Group 2 metal, and most preferably magnesium (Mg). preferable. In the present invention, the p-type oxide semiconductor film obtained in this step may be annealed.

In the present invention, the metal oxide gas may be obtained, for example, by evaporating and optionally oxidizing a liquid substance (for example, mist or the like) of a precursor of the metal oxide gas. . In this case, the liquid substance (for example, mist or the like) of the precursor of the metal oxide gas is preferably a mist obtained by atomizing or dropletizing the raw material solution.

Hereinafter, as another preferable embodiment of the method for forming a p-type oxide semiconductor film of the present invention, it is obtained by evaporating and optionally oxidizing a liquid substance (for example, mist etc.) of a precursor of metal oxide gas A method for forming a p-type oxide semiconductor film when using a metal oxide is described in more detail.

In the method of forming a p-type oxide semiconductor film according to the present invention, for example, a raw material solution containing a precursor of the metal oxide gas is atomized or formed into droplets using a two-zone film forming apparatus shown in FIG. The obtained mist or droplets are evaporated or optionally oxidized (evaporation step), and then the obtained metal oxide gas is used to grow crystals on a substrate having a corundum structure (Crystal growth step). Here, the substrate and the crystal growth step may be the same as the substrate and crystal growth step in the method for forming a p-type oxide semiconductor film using the solid substance of the metal oxide gas described above. By thus forming the p-type oxide semiconductor film, it is possible to form the p-type oxide semiconductor film more favorably, unlike the case where the conventional mist CVD method or the like is used. A p-type oxide semiconductor film excellent in smoothness can be obtained.

(Atomization / droplet formation process)
In the atomization / droplet formation step, the raw material solution is atomized or formed into droplets. The means for atomizing or dropletizing the raw material solution is not particularly limited as long as it can atomize or drop the raw material solution, and may be a known means, but in the present invention, ultrasonic waves are used. The atomizing means or dropletizing means used is preferred. The mist or droplet obtained by using ultrasonic waves is preferable because it has an initial velocity of zero and floats in the air, and for example, it can be transported as a gas floating in a space rather than being sprayed like a spray. It is very suitable because it is a mist which is not damaged by collision energy. The droplet size is not particularly limited, and may be about several mm, but preferably 50 μm or less, and more preferably 100 nm to 10 μm.

(Raw material solution)
The raw material solution contains a precursor of the metal oxide gas, and is not particularly limited as long as atomization or dropletization is possible, and may contain an inorganic material or an organic material. It may be. In the present invention, preferably, the raw material solution contains a metal or a compound thereof contained in the p-type oxide semiconductor film. In the present invention, as the raw material solution, one in which the metal contained in the p-type oxide semiconductor film is dissolved or dispersed in the form of a complex or a salt in an organic solvent or water can be suitably used. Examples of the form of the complex include acetylacetonato complex, carbonyl complex, ammine complex, hydride complex and the like. Examples of the salt form include organic metal salts (eg, metal acetate, metal oxalate, metal citric acid, etc.), metal sulfides, metal nitrates, metal phosphates, metal halides (eg metal chlorides) And metal bromides, metal iodides and the like).

Moreover, it is preferable to mix additives, such as hydrohalic acid and an oxidizing agent, with the said raw material solution. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, hydroiodic acid and the like, but hydrobromic acid or hydroiodic acid is preferable among them because a better film can be obtained. preferable. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), benzoyl peroxide (C ₆ H ₅ CO) ₂ O _{2 and the} like. Peroxides, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, organic oxides such as peracetic acid and nitrobenzene, and the like.

The raw material solution may contain a dopant. Doping can be favorably performed by including the dopant in the raw material solution. The dopant is not particularly limited as long as the object of the present invention is not impaired. As the dopant, for example, Mg, H, Li, Na, K, Rb, Cs, Fr, Be, Ca, Sr, Ba, Ra, Mn, Fe, Co, Ni, Pd, Cu, Ag, Au, Zn And p-type dopants such as Cd, Hg, Tl, Pb, N, P and the like. The concentration of the dopant may generally be about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant may be low, for example, about 1 × 10 ¹⁷ / cm ³ or less. May. Furthermore, in the present invention, the dopant may be contained at a high concentration of about 1 × 10 ²⁰ / cm ³ or more.

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

(Evaporation process)
In the evaporation step, the metal oxide gas is obtained by evaporating and optionally oxidizing a liquid substance (for example, mist or the like) of the precursor of the metal oxide gas. The metal oxide gas may be the same as the metal oxide gas in the sublimation process. Moreover, as an evaporation means, a heating means is mentioned, for example. The heating temperature in the evaporation means may be the same as the heating temperature in the sublimation means. In the present invention, the metal oxide gas obtained by evaporation is preferably transported to the substrate by the carrier gas. The type of carrier gas is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include oxygen, ozone, inert gases such as nitrogen and argon, and reducing gases such as hydrogen gas and forming gas. In particular, oxygen gas and / or ozone gas are preferred. In the present invention, the precursor of the metal oxide gas can be more suitably oxidized by using oxygen gas and / or ozone gas as the carrier gas. In addition, although one kind of carrier gas may be used, it may be two or more kinds, and a dilution gas (for example, 10-fold dilution gas etc.) in which the carrier gas concentration is changed may be used as the second carrier gas. You may use further. Further, the carrier gas may be supplied not only to one place, but also to two or more places. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 L / min to 20 L / min and more preferably 0.1 to 10 L / min.

The p-type oxide semiconductor film obtained as described above is suitably used as a p-type semiconductor layer using a known means. In the present invention, the p-type oxide semiconductor film is formed by using, as the metal oxide gas, a substance obtained by sublimation of a solid substance (for example, powder) of the metal oxide gas. The above-described p-type oxide semiconductor film can be formed more favorably, and for example, a p-type oxide semiconductor film having a surface roughness of 5 nm or less and excellent in surface smoothness can be obtained, which is preferable. In the present invention, a film may be formed as it is on the substrate, but a semiconductor layer different from the p-type semiconductor layer (for example, n-type semiconductor layer, n + -type semiconductor layer, n − -type semiconductor) may be formed on the substrate After laminating other layers such as a layer or the like), an insulator layer (including a semi-insulator layer), a buffer layer and the like, a film may be formed on the substrate via the other layer. As a semiconductor layer and an insulator layer, the semiconductor layer containing the said 13th group metal, an insulator layer, etc. are mentioned, for example. As the buffer layer, for example, a semiconductor layer including a corundum structure, an insulator layer, a conductor layer, and the like can be given as preferable examples. Examples of the semiconductor layer containing the corundum structure include α-Fe ₂ O ₃ , α-Ga ₂ O ₃ , and α-Al ₂ O ₃ . The means for laminating the buffer layer is not particularly limited, and may be the same as the means for forming the p-type oxide semiconductor.

In the present invention, it is preferable to form an n-type semiconductor layer before or after forming the p-type semiconductor layer. More specifically, it is preferable that the method for manufacturing a semiconductor device includes the step of laminating at least a p-type semiconductor layer and an n-type semiconductor layer. The means for forming the n-type semiconductor layer is not particularly limited and may be a known means, but in the present invention, the mist CVD method is preferable. The n-type semiconductor layer preferably contains an oxide semiconductor as a main component, and an oxide semiconductor containing a metal of Group 13 of the periodic table (for example, Al, Ga, In, Tl, etc.) as a main component. More preferable. The n-type semiconductor layer preferably contains a crystalline oxide semiconductor as a main component, more preferably contains a crystalline oxide semiconductor containing Ga, and has a corundum structure and contains Ga. Most preferably, a crystalline oxide semiconductor is used as the main component. In the present invention, a pn junction is formed favorably even when the lattice constant difference between the oxide semiconductor which is the main component of the n-type semiconductor and the p-type oxide semiconductor is 1.0% or less. It is preferable that the content is 0.3% or less. Here, the “lattice constant difference” is a value obtained by subtracting the lattice constant of the p-type oxide semiconductor from the lattice constant of the oxide semiconductor which is the main component of the n-type semiconductor, It is defined as a value (%) obtained by multiplying the absolute value of the value divided by the lattice constant by 100. An example of the case where the lattice constant difference is 1.0% or less is the case where the p-type oxide semiconductor has a corundum structure, and the oxide semiconductor which is the main component of the n-type semiconductor also has a corundum structure And the like, and more preferably, the p-type oxide semiconductor is a single crystal or mixed crystal of Ir ₂ O ₃ , and the oxide semiconductor that is the main component of the n-type semiconductor is a single oxide of Ga ₂ O ₃ . The case of a crystal or mixed crystal may, for example, be mentioned. Note that “the main component” means that the oxide semiconductor is contained in an atomic ratio, preferably 50% or more, more preferably 70% or more, still more preferably 90% or more to all components of the n-type semiconductor layer Meaning that it may be 100%. In the present invention, the p-type oxide semiconductor may be single crystal or polycrystal.

The p-type oxide semiconductor film obtained by the above preferable formation method is industrially useful and has excellent electrical characteristics. More specifically, the mobility is usually 1.0 cm ² / V · s or more. The mobility refers to the mobility obtained by Hall effect measurement, and in the present invention, the mobility is preferably 3.0 cm ² / Vs or more. In addition, the p-type oxide semiconductor film preferably has a carrier density of 8.0 × 10 ²⁰ / cm ³ or more. Here, the carrier density refers to the carrier density in the semiconductor film obtained by Hall effect measurement. The lower limit of the carrier density is not particularly limited, but is preferably about 1.0 × 10 ¹⁵ / cm ³ or more, and more preferably about 1.0 × 10 ¹⁷ / cm ³ or more. In the present invention, the carrier density is in the range of 1.0 × 10 ¹⁶ / cm ³ to 1.0 × 10 ²⁰ / cm ³ by adjusting the kind and amount of dopant or the mixed crystal material and the content thereof. It can be easily controlled.

The p-type oxide semiconductor film obtained as described above can be used for a semiconductor device as a p-type semiconductor layer, and is particularly useful for power devices. By using the p-type oxide semiconductor film for a semiconductor device, roughness scattering can be suppressed, and the channel mobility of the semiconductor device can be made excellent. Semiconductor devices are classified into horizontal devices (horizontal devices) in which electrodes are formed on one side of the semiconductor layer and vertical devices (vertical devices) each having electrodes on the front and back sides of the semiconductor layer. In the present invention, although it can be used suitably also as a horizontal type device and a vertical type device, it is preferred to use for a vertical type device especially. As the semiconductor device, for example, Schottky barrier diode (SBD), metal semiconductor field effect transistor (MESFET), high electron mobility transistor (HEMT), metal oxide semiconductor field effect transistor (MOSFET), electrostatic induction transistor ( SIT), a junction field effect transistor (JFET), an insulated gate bipolar transistor (IGBT) or a light emitting diode.

Example 1
1. Film Forming Apparatus The film forming apparatus used in the present embodiment will be described with reference to FIG. The film forming apparatus 1 of FIG. 1 is provided with a quartz cylinder 2 connected to a carrier gas supply source, and a raw material installation stand 4 made of quartz in the quartz cylinder 2. Raw material 5 is placed. A heater 3 is cylindrically provided outside the quartz cylinder 2 around the raw material installation stand, and is configured to be able to heat the raw material 5. Further, a quartz substrate table is installed as a susceptor 7 at the back of the quartz tube 2 and the installation position is adjusted so that the susceptor 7 is within the crystal growth temperature.

2. Preparation for Film Formation IrO ₂ powder as the raw material 5 was placed on the raw material installation stand 4, and a sapphire substrate was placed on the susceptor 7 as the substrate 6. Next, the temperature of the heater 3 is raised to 850 ° C., and the IrO ₂ powder placed on the raw material installation table 4 is heated to sublime the IrO ₂ powder, thereby making gaseous iridium oxide Generated.

3. Film Formation Next, while the temperature of the heater 3 is maintained at 850 ° C., the carrier gas is supplied from the carrier gas supply source into the quartz cylinder 2, and the above 2. The metal oxide gas (gaseous iridium oxide) generated in the above was supplied to the substrate 6 through the quartz cylinder 2. The flow rate of the carrier gas was 1.0 L / min, and oxygen was used as the carrier gas. The metal oxide gas reacted near the surface of the substrate 6 under atmospheric pressure to form a film on the substrate. The film formation time was 60 minutes, and the film thickness was 220 nm. In addition, the substrate temperature at the time of film formation was 600.degree.

4. Evaluation Above 3. The films obtained in the above were subjected to film identification using an X-ray diffraction apparatus, and the obtained film was an α-Ir ₂ O ₃ film. In addition, the result of XRD is shown in FIG. Further, when Hall effect measurement was performed on the obtained α-Ir ₂ O ₃ film, it was found that the F value is 0.998, the carrier type is “p”, and the semiconductor is a p-type semiconductor. The carrier concentration was 1.05 × 10 ²² (/ cm ³ ), and the mobility was 3.12 (cm ² / V · s).
Furthermore, when the film surface is observed using an atomic force microscope (AFM), as shown in FIG. 4, the surface roughness (Ra) is 3.5 nm, and it can be seen that the surface smoothness is very excellent. The surface roughness (Ra) was calculated based on JIS B0601 using a surface shape measurement result for an area of 90 μm square by an atomic force microscope (AFM).

(Comparative example 1)
1. Film Forming Apparatus The mist CVD apparatus used in this comparative example will be described with reference to FIG. The mist CVD apparatus 19 comprises a susceptor 21 for mounting the substrate 20, a carrier gas supply means 22a for supplying a carrier gas, and a flow rate control valve 23a for adjusting the flow rate of the carrier gas delivered from the carrier gas supply means 22a. A carrier gas (dilution) supply means 22b for supplying a carrier gas (dilution), a flow control valve 23b for adjusting the flow rate of the carrier gas delivered from the carrier gas (dilution) supply means 22b, and a raw material solution 24a , The container 25 into which the water 25a is put, the ultrasonic transducer 26 attached to the bottom of the container 25, the supply pipe 27 consisting of a quartz tube having an inner diameter of 40 mm, and the periphery of the supply pipe 27 And a heater 28 installed in the The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal surface. By making both the supply pipe 27 and the susceptor 21 to be the film forming chamber from quartz, the contamination of the device-derived impurities into the film formed on the substrate 20 is suppressed.

2. Preparation of Raw Material Solution Mix iridium chloride (iridium concentration 0.1 mol / L) and gallium bromide (gallium concentration 0.1 mol / L) in ultra pure water and add hydrochloric acid to make the volume ratio 20%. An aqueous solution was prepared and used as a raw material solution. The volume ratio of iridium chloride to gallium bromide was 19: 1.

3. Preparation for film formation The raw material solution 24 a obtained in the above was contained in the mist generation source 24. Next, a c-plane sapphire substrate was placed on the susceptor 21 as the substrate 20, and the temperature of the heater 28 was raised to 750 ° C. Next, the

flow control valves

23a and 23b are opened to supply the carrier gas from the carrier gas supply means 22a and 22b, which is a carrier gas source, into the supply pipe 27, and the atmosphere in the supply pipe 27 is sufficiently replaced with the carrier gas. After that, the flow rate of the carrier gas was adjusted to 1.0 L / min, and the flow rate of the carrier gas (dilution) was adjusted to 0.5 L / min. In addition, oxygen was used as carrier gas.

4. Film formation Next, the ultrasonic transducer was vibrated, and the vibration was propagated to the raw material solution 24 a through the water 25 to atomize the raw material solution 24 a to generate mist. The mist was conveyed by the carrier gas to the supply pipe 27 and thermally reacted in the vicinity of the surface of the substrate 20 at 750 ° C. under atmospheric pressure to form a film on the substrate 20. The film thickness was 280 nm.

Above 4. The films obtained in the above were subjected to film identification using an X-ray diffraction apparatus, and the obtained film was an α-Ir ₂ O ₃ film. In addition, the result of XRD is shown in FIG. Further, when Hall effect measurement was performed on the obtained α-Ir ₂ O ₃ film, it was found that the F value is 0.998, the carrier type is “p”, and the semiconductor is a p-type semiconductor. The carrier concentration was 2.97 × 10 ²¹ (/ cm ³ ), and the mobility was 0.38 (cm ² / V · s). Further, when the film surface was observed using an atomic force microscope (AFM), as shown in FIG. 5, the surface roughness (Ra) was 302 nm. The surface roughness (Ra) was calculated based on JIS B0601 using a surface shape measurement result for an area of 90 μm square by an atomic force microscope (AFM).

(Example 2 and Comparative Example 2)
Films were obtained in the same manner as in Example 1 and Comparative Example 1 except that the film formation time was increased, and they were referred to as Example 2 and Comparative Example 2, respectively. And about the obtained film | membrane, the cross section was observed using SEM. The results are shown in FIG. As apparent from FIG. 6, the film obtained in Example 2 is in the form of a film, whereas the film obtained in Comparative Example 2 is in the form of needles and is in the form of a homogeneous film. I understand that there is not.

From the results of Examples and Comparative Examples, the p-type oxide semiconductor film obtained by the forming method of the present invention is industrially useful because it is excellent in film quality such as surface smoothness and crystallinity. It can be seen that the electrical characteristics such as mobility are also excellent.

(Example 3)
A p-type oxide semiconductor film was obtained in the same manner as in Example 1 except that the film formation time was 2 hours. Next, an n − -type semiconductor layer was stacked over the p-type oxide semiconductor film. In the lamination of the n-type semiconductor layer, gallium bromide (gallium concentration 0.1 mol / L) is mixed with ultrapure water, hydrobromic acid is added to a volume ratio of 20%, and an aqueous solution is prepared. The film was formed in the same manner as in Comparative Example 1 except that this was used as a raw material solution, the temperature of the heater was 420 ° C., and the film forming time was 30 minutes. The film was an α-Ga ₂ O ₃ film.
In addition, an n + -type semiconductor layer was stacked on the obtained n − -type semiconductor layer. In the lamination of the n + -type semiconductor layer, gallium bromide (gallium concentration 0.1 mol / L) is mixed with ultrapure water, hydrobromic acid is added to a volume ratio of 10% to prepare an aqueous solution, and A film was formed in the same manner as in Comparative Example 1 except that 1% of germanium oxide was added to prepare a raw material solution, the temperature of the heater was set to 390 ° C., and the film forming time was set to 30 minutes. It was done by doing.
A Ti film was formed by sputtering on the n + -type semiconductor layer of the obtained laminate, and then photolithography and etching were performed to fabricate a pn diode. An IV measurement was performed on the obtained pn diode. The results are shown in FIG. As apparent from FIG. 7, the p-type oxide semiconductor film of the present invention, for example, has a good PN junction together with a high voltage and low loss n-type semiconductor (for example, gallium oxide etc.) having high breakdown electric field strength. It turns out that it can be realized.

(Example 4)
1. Film Forming Apparatus The film forming apparatus used in the present embodiment will be described with reference to FIG. The film forming apparatus 10 of FIG. 8 is provided with a quartz cylinder 2 connected to a carrier gas supply source, and a raw material installation stand 4 made of quartz in the quartz cylinder 2. Raw material 5 is placed. A heater (raw material side) 3a and a heater (substrate side) 3b are respectively provided cylindrically on the outside of the quartz cylinder 2 around the raw material installation stand so that the raw material 5 can be heated. Further, a quartz substrate table is installed as a susceptor 7 at the back of the quartz tube 2 and the installation position is adjusted so that the susceptor 7 is within the crystal growth temperature.

2. Preparation for Film Formation IrO ₂ powder as the raw material 5 was placed on the raw material installation stand 4, and a sapphire substrate was placed on the susceptor 7 as the substrate 6. Next, the temperature of the heater (raw material side) 3a is raised to 850 ° C., and the IrO ₂ powder placed on the raw material installation table 4 is heated to sublime the IrO ₂ powder, thereby forming a gaseous state. Produced iridium oxide. The temperature of the heater (substrate side) 3 b was increased to 350 ° C.

3. Next, the carrier gas is supplied from the carrier gas supply source into the quartz cylinder 2 while maintaining the temperature of the heater (raw material side) 3a at 850 ° C. and the temperature of the heater (substrate side) at 350 ° C. Above 2. The metal oxide gas (gaseous iridium oxide) generated in the above was supplied to the substrate 6 through the quartz cylinder 2. The carrier gas flow rate was 2.0 L / min, and oxygen was used as the carrier gas. The metal oxide gas reacted near the surface of the substrate 6 under atmospheric pressure to form a film on the substrate. The film formation time was 90 minutes.

4. Evaluation Above 3. The film obtained by the above was subjected to film identification using an X-ray diffractometer, and the obtained film was an α-Ir ₂ O ₃ film. In addition, the result of XRD is shown in FIG. Furthermore, when the film surface is observed using an atomic force microscope (AFM), it can be seen that the surface roughness (Ra) is 0.161 nm and the surface smoothness is very excellent. The surface roughness (Ra) was calculated based on JIS B0601 using a surface shape measurement result for an area of 90 μm square by an atomic force microscope (AFM).

(Example 5)
In the same manner as in Example 4, except that the temperature of the heater (substrate side) was 250.degree. C., the flow rate of the carrier gas was 4.0 L / min, and the film formation time was 120 minutes, p Type oxide semiconductor film was obtained. About the obtained film, when the film was identified using an X-ray diffractometer, the obtained film was an α-Ir ₂ O ₃ film. Moreover, the film | membrane obtained was a film | membrane excellent in surface roughness (Ra) similarly to what was obtained in Example 4. The Hall effect of the obtained α-Ir ₂ O ₃ film was measured. The F value was 0.999 and the carrier type was "p", which proved to be a p-type semiconductor. The carrier concentration was 1.64 × 10 ²¹ (/ cm ³ ), and the mobility was 1.63 (cm ² / V · s).

(Example 6)
1. Film Forming Apparatus The film forming apparatus used in the present embodiment will be described with reference to FIG. The film forming apparatus 30 of FIG. 21 has a susceptor 21 for mounting the substrate 20, carrier gas supply means 22a for supplying a carrier gas, and flow rate adjustment for adjusting the flow rate of the carrier gas delivered from the carrier gas supply means 22a. Valve 23a, carrier gas (dilution) supply means 22b for supplying carrier gas (dilution), flow control valve 23b for adjusting the flow rate of carrier gas delivered from carrier gas (dilution) supply means 22b, and raw material solution 24a, a container 25 for containing water 25a, an ultrasonic transducer 26 mounted on the bottom of the container 25, a supply tube 27 comprising a quartz tube having an inner diameter of 40 mm, a supply tube 27 The heater (raw material side) 28a and the heater (substrate side) 28b respectively installed in the peripheral part of The supply pipe 27 is constituted by two zones of a supply pipe (raw material side) 27a in which a heater (raw material side) 28a is installed and a supply pipe (substrate side) 27b in which a heater (substrate side) 28b is installed. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal surface. By supplying both the supply pipe 27 and the susceptor 21 to be the film forming chamber with quartz, it is possible to suppress the mixing of impurities derived from the device into the film formed on the substrate 20.

2. Preparation of Raw Material Solution Iridium bromide (iridium concentration: 0.1 mol / L) was mixed with ultrapure water, and 48% hydrobromic acid was added to prepare an aqueous solution, which was used as a raw material solution.

3. Preparation for film formation The raw material solution 24 a obtained in the above was contained in the mist generation source 24. Next, a c-plane sapphire substrate was placed on the susceptor 21 as the substrate 20, the temperature of the heater (raw material side) 28a was raised to 950 ° C., and the temperature of the heater (substrate side) was raised to 350 ° C. Next, the

flow control valves

4. Film formation Next, the ultrasonic transducer was vibrated, and the vibration was propagated to the raw material solution 24 a through the water 25 to atomize the raw material solution 24 a to generate mist. The mist was conveyed by the carrier gas to the supply pipe 27a, and the mist was evaporated and oxidized to generate gaseous iridium oxide. Then, the generated metal oxide gas (gaseous iridium oxide) is supplied to the substrate 20 in the supply pipe 27b by the carrier gas, and then the metal oxide gas is at atmospheric pressure at 350 ° C. By reacting in the vicinity, a film was formed on the substrate. The film forming time was 60 minutes.

5. Evaluation Above 4. The film obtained by the above was subjected to film identification using an X-ray diffractometer, and the obtained film was an α-Ir ₂ O ₃ film. In addition, the result of XRD is shown in FIG. Further, when Hall effect measurement was performed on the obtained α-Ir ₂ O ₃ film, it was found that the F value is 1.000, the carrier gas is “p”, and it is a p-type semiconductor. Further, the carrier concentration was 1.12 × 10 ²² (/ cm ³ ), and the mobility was 1.60 (cm ² / V · s). Further, when the film surface is observed using an atomic force microscope (AFM), it can be seen that the surface roughness (Ra) is 9.443 nm and the surface smoothness is excellent. The surface roughness (Ra) was calculated based on JIS B0601 using a surface shape measurement result for an area of 90 μm square by an atomic force microscope (AFM).

Also from the results of Examples 4 to 6, since the p-type oxide semiconductor film obtained by the forming method of the present invention is excellent in film quality such as surface smoothness and crystallinity, it is industrially useful, and It is also found that the electric characteristics such as mobility are excellent.

The p-type oxide semiconductor film obtained by the formation method of the present invention can be used in all fields such as semiconductors (for example, compound semiconductor electronic devices etc.), electronic parts / electrical equipment parts, optical / electrophotographic related devices, industrial members, etc. Although they can be used, they are particularly useful for semiconductor devices and the like because they are excellent in p-type semiconductor characteristics.

DESCRIPTION OF SYMBOLS 1 film-forming apparatus 2 quartz pipe 3 heater 4 raw material installation stand 5 raw material 6 board | substrate 7 susceptor 10 film-forming apparatus 19 mist CVD apparatus 20 board 21 susceptor 22a carrier gas supply means 22b carrier gas (dilution) supply means 23a flow control valve 23b flow volume Control valve 24 Mist source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic transducer 27 Supply pipe 27a Supply pipe (raw material side)
27b Supply pipe (substrate side)
28 heater 29 exhaust port 30 film forming apparatus

Claims

A method of forming a p-type oxide semiconductor film, wherein a metal oxide gas is used as a raw material for forming the p-type oxide semiconductor film.
The method according to claim 1, wherein the metal oxide gas contains a d-block metal of the periodic table or a periodic table group 13 metal.
The method for forming a p-type oxide semiconductor film according to claim 1, wherein the metal oxide gas contains a periodic table group 9 metal or a group 13 metal.
The method for forming a p-type oxide semiconductor film according to any one of claims 1 to 3, wherein the metal oxide gas contains at least iridium.
The method for forming a p-type oxide semiconductor film according to any one of claims 1 to 4, wherein the metal oxide gas is obtained by sublimation of a solid of the metal oxide gas by heating.
The method for forming a p-type oxide semiconductor film according to any one of claims 1 to 5, wherein the formation of the p-type oxide semiconductor film is performed under atmospheric pressure.
The method for forming a p-type oxide semiconductor film according to any one of claims 1 to 6, wherein the formation of the p-type oxide semiconductor film is performed by crystal growth.
The method for forming a p-type oxide semiconductor film according to claim 7, wherein the crystal growth is performed on a substrate having a corundum structure.
A method of forming a metal oxide film, comprising: forming a metal oxide film by forming a metal oxide gas containing a metal of periodic table group 9 and / or periodic table group 13 under an oxygen atmosphere on a substrate A method of forming a metal oxide film characterized by performing a thermal reaction.
The method for forming a metal oxide film according to claim 9, wherein the metal oxide gas contains a p-type dopant.
The method for forming a metal oxide film according to claim 9 or 10, wherein the metal oxide gas contains at least a periodic table group 13 metal.
The method for forming a metal oxide film according to any one of claims 9 to 11, wherein the metal oxide gas contains at least iridium.