Film forming apparatus and film forming method, as well as crystalline metal oxide film, and multilayer structure and semiconductor device using same

Abstract

The present invention provides a film forming apparatus which includes: an atomizing unit that generates mist by atomizing a starting material solution; a carrier gas supply unit that supplies a carrier gas for conveying the mist; a film forming unit that forms a film on a base material by heat-treating the mist; and a conveyance unit which connects the atomizing unit and the film forming unit, and in which the mist is conveyed by the carrier gas. The film forming unit is provided with: a nozzle for supplying the mist, which has been rectified, to the base material; and a microwave heating device for irradiating the mist in the nozzle with microwaves of a multimode system so as to heat the mist. Consequently, a film forming apparatus is provided which is capable of forming a film that has good in-plane uniformity of the film thickness and high crystallinity at a high film forming speed by supplying a large amount of mist to a large diameter substrate while suppressing foreign matter and abnormal growth.

Description

Film forming apparatus, film forming method, crystalline metal oxide film, stacked structure using the same, and semiconductor device

[0001] The present invention relates to a film forming apparatus, a film forming method, a crystalline metal oxide film, and a stacked structure and a semiconductor device using the same.

[0002] High-vacuum film-forming apparatuses capable of realizing a non-equilibrium state, such as pulsed laser deposition (PLD), molecular beam epitaxy (MBE), and sputtering, have been developed to date, and it has become possible to produce oxide semiconductors that could not be produced by conventional melt methods or the like.

[0003] Furthermore, a mist chemical vapor deposition (Mist CVD) method has been developed, which uses atomized mist-like raw materials to grow crystals on a substrate, and has been used to produce gallium oxide (α-Ga) having a corundum structure. ２ O ３ ) has become possible to produce. ２ O ３ As a semiconductor with a large band gap, it is expected to be applied to next-generation switching elements that can achieve high voltage resistance, low loss, and high heat resistance.

[0004] Regarding mist CVD methods, Patent Document 1 describes a tubular furnace-type mist CVD apparatus. Patent Document 2 describes a fine channel-type mist CVD apparatus. Patent Document 3 describes a linear source-type mist CVD apparatus. Patent Document 4 describes a tubular furnace-type mist CVD apparatus, which differs from the mist CVD apparatus described in Patent Document 1 in that a carrier gas is introduced into the mist generator. Patent Document 5 describes a mist CVD apparatus in which a substrate is placed above a mist generator and a susceptor is a rotating stage mounted on a hot plate.

[0005] Japanese Patent Application Laid-Open No. 01-257337 Japanese Patent Application Laid-Open No. 2005-307238 Japanese Patent Application Laid-Open No. 2012-046772 Japanese Patent No. 5397794 Japanese Patent Application Laid-Open No. 2014-063973 Japanese Patent No. 7080115 Japanese Patent No. 6875336 Japanese Patent No. 7239919

[0006] Unlike other CVD methods, the mist CVD method can form films at relatively low temperatures. ２ O ３ However, the present inventors have found that in the mist CVD method, when a large amount of mist is supplied to a substrate in order to improve productivity when forming a film on a large-diameter substrate, the mist is at a low temperature, which leads to a rapid drop in the temperature of the film-forming surface of the substrate, resulting in problems such as a decrease in the crystallinity of the film, damage to the substrate, and a decrease in the film-forming rate.

[0007] α-Ga by mist CVD method ２ O ３ Regarding the fabrication, Patent Document 6 reports an example in which the life of the mist is extended and the film formation rate is improved by heating the pipe that transports the mist with a heater. Also, as a similar attempt, Patent Document 7 reports an example in which the life of the mist is extended and the film formation rate is improved by heating the carrier gas that transports the mist.

[0008] However, in the methods described in Patent Documents 6 and 7, the saturated water vapor pressure increases as the gas temperature increases, accelerating the evaporation of the mist, which not only reduces the amount of mist supplied to the substrate but also causes the raw material in the mist to precipitate and adhere to the film as foreign matter, resulting in abnormal growth.

[0009] Furthermore, when a semiconductor device is fabricated using a film containing a large number of such foreign particles, the foreign particles become killer defects, resulting in problems such as a decrease in breakdown voltage. In particular, large foreign particles, or even small foreign particles clustered together, are likely to become killer defects. These foreign particles generated during film formation can cause abnormal growth if they become embedded in or adhere to the film during film formation, so it is desirable to suppress their generation during the film formation process.

[0010] Furthermore, Patent Document 8 reports an example in which the deposition rate was improved by adding moisture to the carrier gas that transports the mist and increasing the relative humidity as a method for suppressing the evaporation of the mist. However, this method could not be used as a method for depositing a film at a high deposition rate on a large diameter substrate because the moisture in the carrier gas lowers the temperature of the deposition surface of the substrate, resulting in a decrease in crystallinity or damage to the substrate.

[0011] The present invention has been made to solve the above problems, and aims to provide a film formation apparatus and film formation method that can supply a large amount of mist to a large diameter substrate while suppressing foreign matter and abnormal growth, and that can form a film with good in-plane film thickness uniformity and high crystallinity at a high film formation rate, as well as a crystalline metal oxide film with suppressed foreign matter.

[0012] The present invention has been made to achieve the above-mentioned object, and provides a film formation apparatus comprising: a mist-forming section that generates mist by turning a raw material solution into mist; a carrier gas supply section that supplies a carrier gas that transports the mist; a film formation section that heat-treats the mist to form a film on a substrate; and a transport section that connects the mist-forming section with the inside of the film formation section and transports the mist by the carrier gas, wherein the film formation section comprises: a nozzle for supplying the rectified mist to the substrate; and a microwave heating device that irradiates the mist in the nozzle with microwaves in a multimode system to heat the mist.

[0013] This type of film formation apparatus selectively and rapidly heats only the mist out of the mist and carrier gas supplied to the substrate. This prevents the saturated water vapor pressure of the carrier gas from increasing, suppressing mist evaporation and increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate is suppressed even when the mist supply rate is increased, making it possible to form films at a high film formation rate even on large-diameter substrates without impairing crystallinity. Furthermore, by providing a nozzle for rectifying the mist and heating the mist inside the nozzle, it is possible to form films with excellent in-plane film thickness uniformity. Furthermore, by heating a large amount of mist, it is possible to simultaneously form films on multiple substrates, improving productivity.

[0014] In this case, the microwave heating device comprises a microwave generating unit, a microwave irradiating unit that irradiates the microwaves generated by the microwave generating unit onto the mist, and a microwave guide unit through which the microwaves propagate from the microwave generating unit to the microwave irradiating unit, and the microwave irradiating unit can have a wall surface for diffusely reflecting the microwaves and irradiating the microwaves onto the mist.

[0015] This allows the microwaves to be irradiated onto the mist in a stable manner.

[0016] In this case, the portion of the nozzle onto which the microwave is irradiated may be formed of a microwave-transparent material.

[0017] This allows microwaves to directly reach the mist inside, enabling direct microwave heating of the mist.

[0018] In this case, the portion of the nozzle onto which the microwaves are irradiated may be formed from any one of quartz, ceramic, alumina, polytetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, and polyether ether ketone resin.

[0019] This effectively prevents unintentional contamination from the part of the nozzle that is irradiated with microwaves.

[0020] In this case, the representative length of the ejection surface of the nozzle from which the mist is ejected may be greater than 3 cm.

[0021] This makes it possible to further improve the in-plane uniformity of the film to be produced.

[0022] In this case, the film forming section may include a moving mechanism for moving the substrate.

[0023] This makes it possible to further improve the in-plane uniformity of the film to be produced.

[0024] The present invention also provides a film formation method including the steps of: atomizing or dropletizing a raw material solution to generate a mist; transporting the mist to a film formation unit by a carrier gas; and supplying the mist to the substrate through a nozzle in the film formation unit and performing a heat treatment on the substrate to form a film on the substrate, wherein in the step of forming a film on the substrate, microwaves in the nozzle are irradiated by a multimode method to heat the mist.

[0025] According to this film formation method, only the mist can be selectively and rapidly heated out of the mist and carrier gas supplied to the substrate, so the saturated water vapor pressure of the carrier gas does not increase, mist evaporation can be suppressed, and the film formation rate can be increased while suppressing foreign matter and abnormal growth. Furthermore, because high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate can be suppressed even when the amount of mist supplied is increased, making it possible to form films at a high film formation rate without impairing crystallinity, even on large-diameter substrates. Furthermore, by providing a nozzle for rectifying the mist and heating the mist inside the nozzle, it is possible to form films with excellent in-plane film thickness uniformity, and by heating a large amount of mist, it is possible to form films on multiple substrates simultaneously, improving productivity.

[0026] In this case, the raw material solution may contain a metal raw material and at least one solvent selected from water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, tetraethylene glycol, glycerol, benzyl alcohol, and dipropylene glycol.

[0027] This allows the mist to be selectively and rapidly heated by microwave heating.

[0028] In this case, the solvent of the raw material solution may be one containing water as a main component.

[0029] This makes it difficult for impurities derived from the solvent to remain in the film, resulting in excellent atomization efficiency and an advantage in terms of cost.

[0030] In this case, the metal raw material may contain Ga.

[0031] This allows stable α-Ga ２ O ３ A membrane can be prepared.

[0032] In this case, the substrate to be used may have a film-forming surface with a diameter of 10 cm (4 inches) or more.

[0033] By using a substrate with such a large diameter, the crystalline metal oxide film formed on the substrate can be of higher quality and with higher productivity.

[0034] At this time, in the step of forming a film on the substrate, the film can be formed on the substrate while the substrate is being moved.

[0035] This allows the production of a film with improved uniformity.

[0036] In this case, the frequency of the microwaves can be set to 0.9 GHz or more and 300 GHz or less.

[0037] This allows the mist to be heated stably, and the penetration depth of the microwaves to be maintained at an appropriate length, allowing the mist to be heated uniformly all the way to its interior.

[0038] In this case, the frequency of the microwaves can be set to 2.45 GHz or more and 25 GHz or less.

[0039] This allows the mist to be heated more stably, and the penetration depth of the microwaves to be maintained at an appropriate length, allowing for more uniform heating to be achieved even inside the mist.

[0040] The present invention has also been made to achieve the above object, and provides a crystalline metal oxide film containing at least one of gallium and aluminum as a main component, the film having a field of view of 1 mm2 or less per film at a plurality of points on the surface of the crystalline metal oxide film. ２ The present invention provides a crystalline metal oxide film in which a plurality of microscopic images each having the same field of view area and each having a size of 100 nm or less are acquired so that the total field of view area is 20% or more of the surface area of ​​the crystalline metal oxide film and the fields of view do not overlap, and when the number of foreign matter contained in each of the acquired microscopic images is determined, the ratio of the number of microscopic images determined to contain a plurality of foreign matter to the total number of acquired microscopic images is less than 10%.

[0041] Such a crystalline metal oxide film has good film smoothness due to the small amount of foreign matter, and furthermore, the deviation in the position of foreign matter occurrence within the surface is small, making it suitable for use in semiconductor devices.

[0042] At this time, the density of the foreign particles observed from the surface direction of the crystalline metal oxide film was 48 particles / cm ２ It can be less than.

[0043] Such a crystalline metal oxide film has less foreign matter and therefore has better film smoothness, making it suitable for use in semiconductor devices.

[0044] In this case, the distribution of the film thickness measured at 17 or more points on the crystalline metal oxide film can be 4.6% or less.

[0045] Such a crystalline metal oxide film has better film smoothness and a more uniform film thickness over the entire surface, making it more suitable for use in semiconductor devices.

[0046] In this case, the crystalline metal oxide film may have a corundum structure.

[0047] Such a crystalline metal oxide film has a corundum structure with better smoothness.

[0048] In this case, the half-width of the rocking curve of the (006) plane of the crystalline metal oxide film as determined by X-ray diffraction can be less than 19.1 seconds.

[0049] Such a crystalline metal oxide film has good crystallinity and can therefore be suitably used in semiconductor devices.

[0050] In this case, the surface of the crystalline metal oxide film can have a diameter of 10 cm (4 inches) or more.

[0051] Such a crystalline metal oxide film has better smoothness and a large area, and therefore can be more suitably used in semiconductor devices.

[0052] In this case, a laminated structure can be formed which has a substrate, a buffer layer on the substrate, and the above-mentioned crystalline metal oxide film on the buffer layer.

[0053] Such a laminated structure can be suitably used in semiconductor devices because the crystalline metal oxide film has good smoothness.

[0054] In this case, the semiconductor device can include at least one of the crystalline metal oxide film and the laminated structure.

[0055] Such a semiconductor device has excellent electrical characteristics due to the excellent smoothness of the crystalline metal oxide film.

[0056] In this case, the semiconductor device is any one of a semiconductor laser, a diode, and a transistor.

[0057] Such a semiconductor device can be a semiconductor laser, a diode, or a transistor with excellent electrical characteristics.

[0058] As described above, the film formation apparatus of the present invention can selectively and rapidly heat only the mist out of the mist and carrier gas supplied to the substrate. This prevents the saturated water vapor pressure of the carrier gas from increasing, suppressing mist evaporation and thereby increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate is suppressed even when the mist supply rate is increased, making it possible to form films at a high film formation rate even on large-diameter substrates without impairing crystallinity. Furthermore, by providing a nozzle for rectifying the mist and heating the mist inside the nozzle, it is possible to form films with excellent in-plane film thickness uniformity. Furthermore, by heating a large amount of mist, it is possible to simultaneously form films on multiple substrates, improving productivity.

[0059] Furthermore, according to the film formation method of the present invention, only the mist can be selectively and rapidly heated out of the mist and carrier gas supplied to the substrate. This prevents the saturated water vapor pressure of the carrier gas from increasing, suppressing mist evaporation and thereby increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate can be suppressed even when the amount of mist supplied is increased, making it possible to form films at a high film formation rate even on large-diameter substrates without impairing crystallinity. Furthermore, by providing a nozzle for rectifying the mist and heating the mist in the nozzle, it is possible to form films with excellent in-plane film thickness uniformity, and by heating a large amount of mist, it is possible to simultaneously form films on multiple substrates, improving productivity.

[0060] Furthermore, the crystalline metal oxide film of the present invention has good film smoothness due to the small amount of foreign matter, and the in-plane unevenness of the location of foreign matter is small, so when a semiconductor device is fabricated using the crystalline metal oxide film, the influence of foreign matter on the device characteristics is negligible, making it suitable for use in semiconductor devices. The present invention further provides a stacked structure and a semiconductor device having a crystalline metal oxide film having such characteristics.

[0061] 10 is a diagram showing an example of a film forming apparatus according to the present invention. FIG. 11 is a diagram showing an example of a mist generating unit according to the present invention. FIG. 12 is a diagram showing an example of a nozzle according to the present invention. FIG. 13 is a diagram showing another example of a nozzle according to the present invention. FIG. 14 is a diagram showing an example of a reciprocating movement mechanism according to the present invention as viewed vertically from above the film forming unit. FIG. 15 is a diagram showing an example of a rotary movement mechanism according to the present invention as viewed vertically from above the film forming unit. FIG. 16 is a diagram showing an example of a microwave heating device according to the present invention. A cross-sectional view of FIG. 7. FIG. 17 is a diagram showing an example of a foreign substance found in a film produced in a comparative example. FIG. 18 is a diagram showing an example of an abnormally grown portion found in a film produced in a comparative example. FIG. 19 is an electron beam diffraction image of the outside of the abnormally grown portion in FIG. 10. FIG. 19 is an electron beam diffraction image of a crystalline portion found in the center of the abnormally grown portion in FIG. 10. FIG. 19 is a diagram showing an example of a substrate moving mechanism used in Example 6. FIG. 20 is a diagram showing a foreign substance map of Example 5. FIG. 21 is a diagram showing the counted results of the number of foreign substances performed in Example 5. FIG. 22 is a diagram showing the results of Evaluation 4. FIG. 23 is a schematic cross-sectional view showing one embodiment of the structure of a stacked structure according to the present invention. FIG. 24 is a schematic cross-sectional view showing an example of a Schottky barrier diode according to the present invention. FIG. 25 is a schematic cross-sectional view showing an example of a high electron mobility transistor according to the present invention. FIG. 26 is a schematic cross-sectional view showing an example of a semiconductor field effect transistor according to the present invention. FIG. 27 is a schematic cross-sectional view showing an example of an insulated gate bipolar transistor 1 is a schematic cross-sectional view showing an example of a light-emitting diode according to the present invention.

[0062] The present invention will be described in detail below, but the present invention is not limited thereto.

[0063] As described above, there has been a demand for a film formation apparatus and film formation method that can supply a large amount of mist to a large diameter substrate while suppressing foreign matter and abnormal growth, and that can form a film with good in-plane film thickness uniformity and high crystallinity at a high film formation rate, as well as a crystalline metal oxide film with suppressed foreign matter.

[0064] As a result of extensive research into the above-mentioned problems, the inventors have found a film formation apparatus comprising: a mist-forming section that generates mist by turning a raw material solution into a mist; a carrier gas supply section that supplies a carrier gas that transports the mist; a film formation section that heat-treats the mist to form a film on a substrate; and a transport section that connects the mist-forming section with the inside of the film formation section and transports the mist by the carrier gas, wherein the film formation section comprises: a nozzle for supplying the rectified mist to the substrate; and a microwave heating device that irradiates the mist in the nozzle with microwaves using a multimode system to heat the mist. With this film formation apparatus, of the mist and carrier gas that are supplied to the substrate, only the mist can be selectively and rapidly heated. This prevents the saturated water vapor pressure of the carrier gas from increasing and suppresses evaporation of the mist, thereby increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate is suppressed even when the amount of mist supplied is increased, making it possible to form films at a high film formation rate without impairing crystallinity, even on substrates with large diameters.Furthermore, the inventors have discovered that by providing a nozzle for rectifying the mist and heating the mist inside the nozzle, it is possible to form films with excellent in-plane uniformity in film thickness, and that by being able to heat a large amount of mist, it is possible to form films on multiple substrates simultaneously, improving productivity, and have completed the present invention.

[0065] The inventors have also developed a film formation method comprising the steps of atomizing or dropletizing a raw material solution to generate a mist, transporting the mist to a film formation unit using a carrier gas, and supplying the mist to the substrate through a nozzle in the film formation unit and heat-treating the mist on the substrate to form a film on the substrate, wherein the film formation step comprises irradiating the mist in the nozzle with microwaves in a multimode manner to heat the mist. This method selectively and rapidly heats only the mist out of the mist and carrier gas supplied to the substrate, thereby preventing an increase in the saturated vapor pressure of the carrier gas and suppressing mist evaporation, thereby increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate is suppressed even when the amount of mist supplied is increased, making it possible to form films at a high film formation rate without impairing crystallinity, even on large-diameter substrates. Furthermore, the inventors discovered that by providing a nozzle for rectifying the mist and heating the mist inside the nozzle, it is possible to form a film with excellent in-plane uniformity in film thickness, and that by being able to heat a large amount of mist, it is possible to form a film on multiple substrates simultaneously, thereby improving productivity, and thus completed the present invention.

[0066] The present inventors further discovered a crystalline metal oxide film containing at least one of gallium and aluminum as a main component, in which the field of view area per film is 1 mm2 at a plurality of points on the surface of the crystalline metal oxide film. ２ The inventors have found that a crystalline metal oxide film having a ratio of the number of microscopic images determined to contain a plurality of foreign particles to the total number of microscopic images obtained is less than 10%, and that the film has good film smoothness due to the small number of foreign particles, and further has little deviation in the position of foreign particles occurring within the surface, and is therefore suitable for use in semiconductor devices, and have completed the present invention.

[0067] A film forming apparatus according to the present invention will be described below with reference to FIGS.

[0068] (Film Forming Apparatus) Figure 1 shows an example of a film forming apparatus according to the present invention. The film forming apparatus 100 includes a mist generating unit 120 that generates mist by misting a raw material solution, a carrier gas supply unit 130 that supplies a carrier gas for transporting the mist, a film forming unit 140 that heat-treats the mist to form a film on a substrate, a transport unit 109 that connects the mist generating unit 120 and the film forming unit 140 and transports the mist by the carrier gas, a nozzle 150 that supplies the rectified mist onto the substrate 110 in the film forming unit 140, and a microwave heating device 200 that irradiates the mist in the nozzle with microwaves in a multimode system to heat the mist. The film forming apparatus 100 may also be provided with a control unit (not shown) that controls all or part of the film forming apparatus 100, thereby controlling its operation.

[0069] With this type of film formation apparatus, only the mist can be selectively and rapidly heated from the mist and carrier gas supplied to the substrate (crystalline substrate) 110. This prevents the saturated water vapor pressure of the carrier gas from increasing, suppressing mist evaporation, thereby increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate 110, a decrease in the temperature of the substrate 110 is suppressed even when the amount of mist supplied is increased, making it possible to form films at a high film formation rate without impairing crystallinity, even on large-diameter substrates 110. Furthermore, by providing a nozzle 150 for rectifying the mist and heating the mist within the nozzle 150, it is possible to form films with excellent in-plane film thickness uniformity, and by being able to heat a large amount of mist, it is possible to form films on multiple substrates 110 simultaneously, improving productivity.

[0070] [Mist-forming section] The mist-forming section 120 forms mist by forming the raw material solution into mist. The mist-forming means is not particularly limited as long as it can form mist from the raw material solution, and any known mist-forming means may be used, but it is preferable to use a mist-forming means that uses ultrasonic vibrations, as this allows for more stable mist formation.

[0071] An example of such a mist generating unit 120 is shown in FIG. 2 . For example, the mist generating unit 120 may include a mist generating source 104 containing raw solution 104a, a container 105 containing a medium capable of transmitting ultrasonic vibrations, such as water 105a, and an ultrasonic vibrator 106 attached to the bottom of the container 105. Specifically, the mist generating source 104, which is a container containing raw solution 104a, is housed in the container 105 containing water 105a using a support (not shown). An ultrasonic vibrator 106 is attached to the bottom of the container 105, and the ultrasonic vibrator 106 is connected to an oscillator 116. When the oscillator 116 is activated, the ultrasonic vibrator 106 vibrates, and ultrasonic waves propagate through the water 105a into the mist generating source 104, turning the raw solution 104a into mist.

[0072] The carrier gas supply unit 130 has a carrier gas source 102a that supplies a carrier gas, and may also include a flow rate control valve 103a that controls the flow rate of the carrier gas delivered from the carrier gas source 102a. The carrier gas supply unit 130 may also include a dilution carrier gas source 102b that supplies a dilution carrier gas as needed, and a flow rate control valve 103b that controls the flow rate of the dilution carrier gas delivered from the dilution carrier gas source 102b.

[0073] The type of carrier gas is not particularly limited and can be appropriately selected depending on the film to be formed. Examples include inert gases such as oxygen, ozone, nitrogen, and argon, and reducing gases such as hydrogen gas and forming gas. The type of carrier gas may be one or more. For example, a dilution gas obtained by diluting the same gas as the first carrier gas with another gas (e.g., diluted 10 times) may be used as the second carrier gas, or air may be used.

[0074] Furthermore, the number of supply points for the carrier gas may not be one, but may be two or more.

[0075] The flow rate of the carrier gas is not particularly limited. For example, when forming a film on a substrate with a diameter of 10 cm (4 inches), the flow rate is preferably 1 to 80 L / min, and more preferably 4 to 40 L / min. The flow rate of the carrier gas in the present invention is a value measured at 20°C and atmospheric pressure. When measured at other temperatures and pressures or when a different type of flow rate (mass flow rate, etc.) is measured, the flow rate can be converted to a volumetric flow rate at 20°C and atmospheric pressure using the gas state equation.

[0076] [Transport Unit] The transport unit 109 connects the mist generation unit 120 and the film formation unit 140. Mist is transported by a carrier gas from the mist generation source 104 of the mist generation unit 120 to the film formation chamber 107 of the film formation unit 140 via the transport unit 109. The transport unit 109 can be, for example, a supply pipe 109a. The supply pipe 109a can be, for example, a quartz pipe or a resin tube.

[0077] [Film Forming Section] In the film forming section 140, the mist is heated to cause a thermal reaction, thereby forming a film on a part or all of the surface of the base (crystalline substrate) 110. The film forming section 140 may include, for example, a film forming chamber 107 in which the base (crystalline substrate) 110 is placed, and a hot plate 108 for heating the base (crystalline substrate) 110.

[0078] 1 , the hot plate 108 may be provided outside the film formation chamber 107, or may be provided inside the film formation chamber 107. In addition, the film formation chamber 107 may be provided with an exhaust gas outlet 112 at a position that does not affect the supply of mist to the base (crystalline substrate) 110.

[0079] Furthermore, the film forming section 140 includes a nozzle 150 for rectifying the mist and supplying it to the substrate 110, and a microwave heating device 200 for heating the mist with microwaves.

[0080] 1, the film forming unit 140 is equipped with a nozzle 150 for supplying mist to the substrate 110. The nozzle 150 straightens the mist that flows into the nozzle 150 from the supply pipe 109a and supplies it onto the substrate 110. An example of such a nozzle is shown in FIG.

[0081] 3, the nozzle 150 is preferably a box-shaped member that has a connection part 151 that connects to the transport part 109, an internal space (not shown) for rectifying the flow of the mist, and a nozzle discharge surface 152 that discharges the mist toward the substrate 110. Here, rectifying the flow means aligning the flow directions of the mist and carrier gas discharged at the nozzle discharge surface.

[0082] The installation position of the nozzle is not particularly limited. As shown in Fig. 1 , the substrate 110 may be installed on the lower surface of the film formation chamber 107 and the nozzle 150 may be provided vertically above the substrate 110, thereby forming a face-up arrangement, or the substrate 110 may be installed on the upper surface of the film formation chamber 107 and the nozzle 150 may be provided vertically below the substrate, thereby forming a face-down arrangement.

[0083] The number of nozzles and the number of nozzle discharge surfaces are not particularly limited as long as they are at least 1. A plurality of nozzles may be provided, and there may be a plurality of nozzle discharge surfaces 152, as in the nozzle shown in FIG.

[0084] Furthermore, there are no particular limitations on the angle formed between the plane including the nozzle discharge surface 152 and the plane including the surface of the base 110. A nozzle (not shown) may be provided in which part or all of the nozzle discharge surface 152 is inclined so that the mist flows more easily in a specific direction, but it is preferable that the base 110 and the nozzle discharge surface 152 are arranged parallel to each other, as shown in Fig. 1. This is because a film with good in-plane uniformity in film thickness can be formed with a simpler structure.

[0085] The nozzle 150 may also be equipped with a nozzle position adjustment mechanism (not shown) that can appropriately adjust the longest distance between any point in the nozzle discharge surface 152 and the surface of the substrate 110. The longest distance between any point in the nozzle discharge surface 152 and the surface of the substrate 110 is not particularly limited, but is preferably 0.1 cm or more and less than 10 cm, more preferably 0.1 cm or more and less than 6 cm, and even more preferably 0.1 cm or more and less than 3 cm. If the distance is 0.1 cm or more, contact between the nozzle 150 and the substrate 110 due to thermal expansion during film formation can be effectively prevented, and if it is less than 10 cm, the in-plane uniformity of the film thickness can be further improved.

[0086] There are no particular limitations on the shape of the nozzle discharge surface 152. Possible shapes include polygonal, circular, and elliptical, but a quadrangular shape is preferable, and a rectangular shape is more preferable.

[0087] Furthermore, the representative length L [cm] of the nozzle discharge surface 152 of the nozzle 150 that discharges the mist is preferably greater than 3 cm. L can be determined appropriately depending on the size of the base 110, but it is preferably longer than the representative length R [cm] of the base 110. Note that the representative length in the present invention refers to the diameter in the case of a circle, the length of the major axis in the case of an ellipse, and the length of the longest side in the case of a polygon. For example, if the base 110 is a circle with a diameter of 4 inches, R is approximately 10 cm, and if the nozzle discharge surface is a rectangle with a long side of 15 cm and a short side of 2 cm, L is 15 cm.

[0088] If L is greater than 3 cm, or if L is greater than R, the in-plane uniformity of the film to be produced can be further improved. There is no particular upper limit to L, but it can be set to, for example, about twice the representative length R of the substrate 110. If it is equal to or less than twice the representative length R, an effective amount of mist is supplied to the substrate, and the utilization efficiency of the raw material can be effectively maintained.

[0089] The film forming unit 140 may also be provided with a moving mechanism that moves the substrate 110 below the nozzle 150. Figures 5 and 6 show a reciprocating moving mechanism 160a and a rotary moving mechanism 160b provided in the film forming unit 140, viewed from vertically above the substrate 110. As shown in Figures 5 and 6, the moving mechanism includes moving stages 161a and 161b on which the substrate 110 and the hot plate 108 are placed.

[0090] Such a movement mechanism can further improve the in-plane uniformity of the film to be formed.

[0091] It is preferable that the portion of the nozzle 150 that is irradiated with microwaves is formed from a microwave-transparent material.

[0092] By using a material that is easily permeable to microwaves, microwaves can reach the mist inside directly, allowing the mist to be directly heated by microwaves.

[0093] Microwave heating can generate heat in a much shorter time than conventional heating by heat transfer, so the mist can be heated to a predetermined temperature quickly.

[0094] The material for forming the portion of the nozzle 150 onto which microwaves are irradiated is not particularly limited as long as it is microwave transparent, and can be appropriately selected depending on the purpose. Examples include quartz, ceramic, alumina, polytetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, polyether ether ketone resin, glass, sapphire, polyethylene resin, etc., but among these, any of quartz, ceramic, alumina, polytetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, and polyether ether ketone resin is more preferred.

[0095] Such a material can effectively prevent unintentional contamination from the part of the nozzle 150 that is irradiated with microwaves.

[0096] In order to avoid contact between the nozzle 150 and the raw material solution, the inner wall surface of the nozzle 150 may be surface-treated depending on the type of solvent contained in the raw material solution. For example, when the solvent is water, the surface of the inner wall may be hydrophobized by irradiating it with ultraviolet light, ultrasonic waves, or radiation, or may be hydrophobized using a hydrophobic material such as a silane coupling agent or polytetrafluoroethylene resin. In any case, the material of the portion of the nozzle 150 that is not irradiated with microwaves is not particularly limited.

[0097] The thickness of the wall of the nozzle 150 is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 0.05 mm to 10 mm, and more preferably 0.1 mm to 2 mm. If the thickness is in the range of 0.05 mm to 10 mm, appropriate strength can be maintained, damage due to pressure fluctuations within the nozzle 150 can be effectively prevented, and a decrease in heating efficiency due to microwave transmission loss can be effectively prevented.

[0098] In addition, the volume V [cm ３ ] is not particularly limited. It can be appropriately determined depending on the flow rate of the carrier gas and the mist, but the flow rate of the carrier gas is ３ / s], it is preferable that V / Q be 0.01≦V / Q≦10. If V / Q is in this range, the mist can be appropriately rectified and heated, so that the uniformity of the film thickness and the film formation rate can be maintained at an appropriate level, and further, evaporation of the mist can be suppressed, so that a deterioration in film quality can be effectively prevented.

[0099] [Microwave Heating Device] The microwave heating device is not particularly limited as long as it can irradiate microwaves, and is composed of a known microwave generating unit, a microwave irradiating unit and a microwave guide unit formed of a conductive material such as aluminum, copper, brass, etc., and within the microwave irradiating unit, at least a part of the nozzle 150 is arranged so as to pass through the microwave irradiation space of the microwave irradiating unit.

[0100] An example of a microwave heating device according to the present invention is shown in Figures 7 and 8. Figure 8 is a cross-sectional view of Figure 7. As shown in Figure 7, a microwave heating device 200 according to the present invention comprises a microwave generating unit 201, a microwave irradiating unit 204 that irradiates mist with microwaves generated in the microwave generating unit, and a microwave guide unit 205 through which microwaves propagate from the microwave generating unit to the microwave irradiating unit, and the microwave irradiating unit comprises a wall surface 206 for diffusely reflecting the microwaves to irradiate the mist with the microwaves.

[0101] Such a microwave heating device can stably irradiate the mist with microwaves.

[0102] The microwave heating device 200 is disposed in the film forming section 140. If the distance from the microwave heating device 200 to the substrate 110 is too great, the mist heated by microwaves will radiate heat, causing the temperature of the mist to drop, and in addition, the temperature of the surrounding carrier gas will rise, increasing the saturated vapor pressure, accelerating the evaporation of the mist, and decreasing the film forming rate.

[0103] Microwave heating can be divided into a multimode system, such as that used in a microwave oven, and a single mode system in which one standing wave is formed in a waveguide, but the microwave heating device 200 of the present invention is a multimode system. Although the single mode system has excellent heating efficiency, the space that can be heated is limited, making it difficult to use a component that rectifies the mist, such as a nozzle, which can result in poor in-plane film thickness uniformity and poor productivity due to the difficulty of forming films on multiple substrates.

[0104] A standing wave is a wave whose waveform does not progress but appears to be stationary and vibrating, creating a state in which the positions of places with zero electric field strength and places with strong electric field strength do not change over time.

[0105] In multimode microwave heating, microwaves generated in a microwave generator are diffusely reflected by the wall of the microwave irradiator and irradiated onto the mist, which is the object to be heated. This eliminates the need to control the size of the microwave irradiator or microwave waveguide to form standing waves, making the device simpler and enabling microwaves to be irradiated into large spaces.

[0106] The multi-mode microwave heating device 200 according to the present invention comprises a microwave oscillator as a microwave generating section 201, an applicator as a microwave irradiating section 204, and a waveguide as a microwave guiding section 205, the applicator 204 having a wall surface 206 that diffusely reflects microwaves, and the nozzle 150 is arranged within the applicator 204 so that part or all of it passes through the microwave irradiation space.

[0107] Microwaves are output from a microwave oscillator 201, propagate through a waveguide 205, enter an applicator 204, and are diffusely reflected within the applicator 204. A portion of the energy of the microwaves is absorbed by the mist passing through the nozzle 150.

[0108] The microwave heating device 200 may also include a thermometer 207 that measures the temperature of the nozzle 150 .

[0109] The microwave oscillator 201 may be of a magnetron type or a semiconductor type (or solid-state type), but in the present invention, the magnetron type is preferred because it allows microwave irradiation with a large output.

[0110] The material of the applicator 204 is not particularly limited, and may be made of a conductive material such as aluminum, copper, or brass. The outer surface of the applicator 204 may be coated with an acid-resistant material to prevent corrosion even in an acidic raw material solution. The acid-resistant coating agent is not particularly limited, and known coating agents such as Teflon (registered trademark) can be used.

[0111] The shape of the applicator 204 is not particularly limited. Specifically, a box-shaped container such as a microwave oven can be used. Microwaves irradiated into the applicator 204 are diffusely reflected by the wall surface of the applicator 204, allowing the microwaves to be irradiated into a large-volume space.

[0112] Furthermore, the relative positions of the nozzle 150 and the applicator 204 are not particularly limited, but it is preferable that the nozzle 150 is located at the center of the internal space of the applicator 204, as shown in Fig. 8. This is because microwave irradiation efficiency is excellent.

[0113] The material of the waveguide 205 is not particularly limited, and it may be formed of a conductive material such as aluminum, copper, brass, etc. The outer surface of the waveguide 205 may be coated with an acid-resistant material to prevent corrosion even in an acidic raw material solution. The acid-resistant coating material is not particularly limited, and known coating materials such as Teflon (registered trademark) can be used.

[0114] The cross-sectional shape of the waveguide 205 is not particularly limited, and may be circular, elliptical, rectangular, or the like.

[0115] (Crystalline Metal Oxide Film) Next, the crystalline metal oxide film of the present invention will be described. The crystalline metal oxide film of the present invention is a crystalline metal oxide film containing at least one of gallium and aluminum as a main component, and has a field area of ​​1 mm2 per film at a plurality of points on the surface of the crystalline metal oxide film.２ The method is characterized in that a plurality of microscopic images each having the same field of view area and each having a size of 0.01 mm or less are acquired so that the total field of view area is 20% or more of the surface area of ​​the crystalline metal oxide film and the fields of view do not overlap, and when the number of foreign matter contained in each of the acquired microscopic images is determined, the ratio of the number of microscopic images determined to contain multiple foreign matter to the total number of acquired microscopic images is less than 10%.

[0116] Such a crystalline metal oxide film has good film smoothness due to the small amount of foreign matter, and furthermore, the position of foreign matter occurrence within the film surface is less uneven, making it suitable for use in semiconductor devices.

[0117] The surface of the crystalline metal oxide film in the present invention refers to one of the surfaces of the crystalline metal oxide film, which has a front surface and a back surface.

[0118] In the present invention, the surface direction refers to the direction from the side with a larger z coordinate than the surface of the crystalline metal oxide film to the side with a smaller z coordinate, when the direction from the back side to the front side of the crystalline metal oxide film is defined as the positive z-axis direction.

[0119] In the present invention, the location of the foreign matter is not particularly limited as long as it can be observed from the surface direction. It may be attached to the surface, or may be partially or completely embedded in the film. The observation method will be described later, but is not particularly limited. The height in the observation direction can also be distinguished by using a confocal microscope or the like.

[0120] Generally, crystalline metal oxide films are composed of metal and oxygen, but in the crystalline metal oxide film according to the present invention, the metal is primarily composed of at least one of gallium and aluminum. The term "primary component" as used herein means that 50 to 100 atomic % of the metal component is gallium or aluminum. It also means that the combined total of gallium and aluminum is 50 to 100 atomic %.

[0121] The metal component other than gallium or aluminum may include, for example, one or more metals selected from iron, indium, vanadium, titanium, chromium, rhodium, iridium, nickel, and cobalt.

[0122] The microscope image according to the present invention refers to a microscope image obtained by observing the crystalline metal oxide film from the surface direction.

[0123] In the present invention, there is no particular limitation on the method for acquiring a microscopic image. The crystalline metal oxide film may be placed on an observation stage and images may be taken while manually changing the position. However, a method in which the stage is electrically controlled and the microscopic image is automatically taken at a fixed position is preferred, as this allows for efficient and stable imaging.

[0124] In the present invention, it is sufficient that the total field of view area of ​​the acquired microscope image is 20% or more of the surface area of ​​the crystalline metal oxide film. The larger the total field of view area, the better, and it is more preferable to inspect 90% or more of the surface (almost the entire surface). The upper limit can be, for example, 100%. Furthermore, if the total field of view area is less than 20% of the surface area of ​​the crystalline metal oxide film, there is a high possibility that the foreign matter will not be included in the observation range if the foreign matter is generated locally, and therefore the inspection will not be meaningful.

[0125] A method for observing and measuring such an area is, for example, to control an electric XY stage so that the field of view of the microscope image is 1 x 1 mm, and automatically photograph the entire surface of the wafer with an imaging camera at 2 mm intervals. With this method, 1789 points (= 17.89 cm) can be measured on a 4-inch diameter wafer. ２ ) can be automatically photographed, covering an area of ​​more than 20% of the entire 4-inch surface.

[0126] The field of view area per microscope image is 1 mm ２ less than or equal to 0.5 mm ２ The lower limit of the field of view area is not particularly limited, but is preferably 0.1 mm ２ The field of view area can be set to 1 mm ２If the field of view is made too large (i.e., a low magnification), it becomes difficult to identify small foreign particles, and if the field of view area is made too small (i.e., a high magnification), the number of images taken increases, making evaluation complicated.

[0127] In the present invention, it is sufficient that the ratio of the number of microscope images determined to contain multiple foreign substances to the total number of acquired microscope images is less than 10%, more preferably 5% or less, and even more preferably 1% or less. There is no particular lower limit, but the lower the better, for example, 0%. If there are so many foreign substances that multiple foreign substances exist within the field of view area, they are likely to become killer defects when a semiconductor device is fabricated, and the semiconductor device is likely to have low breakdown voltage. If the ratio of the number of microscope images containing multiple foreign substances to the total number of acquired microscope images is less than 10%, the yield when semiconductor devices are fabricated is good, and an industrially excellent crystalline metal oxide film is obtained.

[0128] Furthermore, the foreign matter according to the present invention is a particle as shown in FIG. 9, which originates from the metal raw material in the mist. The mechanism by which the foreign matter is formed is unclear, but possible causes include deposition of the metal raw material due to evaporation of water in the mist during film formation, and formation of metal oxide due to a side reaction of the metal raw material in the gas phase. The majority of these particles are amorphous. There are no particular limitations on the method for analyzing the particle composition. They can be examined using EDX, Auger electron spectroscopy, SIMS, etc. Furthermore, there are no particular limitations on the method for analyzing the crystal structure. They can be examined using common methods such as electron beam diffraction.

[0129] When these particles adhere to or are embedded in the film surface, they are partially or completely crystallized by heat. However, in this case, aluminum oxide crystals or gallium oxide crystals, or mixed crystals thereof, grow in the gamma phase, not the alpha phase. Therefore, when a voltage is applied to a film containing foreign matter, the electric field concentrates at the grain boundary between the alpha phase and the gamma phase, easily causing dielectric breakdown. If the ratio of the number of microscopic images containing multiple foreign matter to the total number of acquired microscopic images is less than 10%, dielectric breakdown due to grain boundary formation can be sufficiently suppressed, and semiconductor devices can be manufactured with a high yield using this crystalline metal oxide film.

[0130] In addition to the SEM used to observe the foreign matter shown in Figure 9, the shape and quantity of foreign matter can be determined by observing the shape and evaluating the number of occurrences using an electron microscope such as a TEM, an optical microscope, a surface inspection device that detects defects from the difference in brightness, or a surface inspection device that uses image recognition AI to learn and detect defects, but the observation method and the method for evaluating the number of occurrences are not particularly limited.

[0131] The foreign matter in the present invention has a particle diameter of 10 nm to 10 μm. The particle diameter here refers to the circle-equivalent diameter in a two-dimensional image observed from the surface direction of the crystalline metal oxide film. The circle-equivalent diameter is the diameter of a circle having an area equivalent to the area of ​​the particle captured in the two-dimensional image, and the particle area can be calculated by image analysis or the like.

[0132] The particle size distribution can be created by measuring the particle sizes of the foreign matter using the method described above. For the crystalline metal oxide film according to the present invention, the standard deviation of the particle sizes is preferably less than 1.25 μm, more preferably less than 0.50 μm, and even more preferably 0.30 μm or less.

[0133] Since the size of the foreign particles in such a crystalline metal oxide film is small and uniform, the impact of the foreign particles on the device characteristics is less when a semiconductor device is fabricated, making the film suitable for use in semiconductor devices. There is no particular lower limit. The smaller the value, the better, and it can be set to, for example, 0 (when all the values ​​are the same). The standard deviation σ can be calculated using the following formula:

[0134]

[0135] Furthermore, the crystalline metal oxide film according to the present invention preferably has a particle size distribution index D90 / D10 of less than 5.7, preferably 4.0 or less, and more preferably 3.0 or less. Since such a crystalline metal oxide film has more uniformly sized foreign particles, it facilitates the design of semiconductor devices and is suitable for use in semiconductor devices. The lower limit is not particularly limited, but is typically around 1.5.

[0136] In the present invention, the particle diameter D90 refers to the particle diameter corresponding to a cumulative ratio of 90% in the particle diameter distribution, the particle diameter D10 refers to the particle diameter corresponding to a cumulative ratio of 10%, and the particle diameter D50 refers to the particle diameter corresponding to a cumulative ratio of 50%.

[0137] The particle diameter D90 value is not particularly limited, but is preferably less than 4.25 μm, and more preferably 1.0 μm or less. The lower limit is also not particularly limited. The smaller the value, the better, and it can be, for example, greater than 1 nm. Since the size of the foreign particles in such a crystalline metal oxide film is small, the effect of the foreign particles on the device characteristics when a semiconductor device is fabricated is less, making the film suitable for use in semiconductor devices.

[0138] The value of the particle diameter D10 is not particularly limited. The smaller the particle diameter D10, the less the influence of the foreign matter on the device characteristics when a semiconductor device is manufactured, and the more suitable the particle diameter D10 is for use in a semiconductor device.

[0139] Furthermore, for the crystalline metal oxide film according to the present invention, the particle diameter D50, which is the cumulative ratio of 50% in the particle diameter distribution, is preferably less than 2.75 μm, preferably 2.0 μm or less, and more preferably 0.5 μm or less. The lower limit is not particularly limited. The smaller the D50, the better, and it can be, for example, greater than 1 nm. When a semiconductor device is fabricated using such a crystalline metal oxide film, the effect of foreign matter on the device characteristics is less severe, making the film suitable for use in semiconductor devices.

[0140] Furthermore, in the crystalline metal oxide film according to the present invention, the proportion of particles having a particle diameter of at least D50 minus the standard deviation σ and at most D50 plus the standard deviation σ, relative to the total number of foreign particles, is preferably at least 60%, more preferably at least 75%. The higher this proportion, the better, and the upper limit can be, for example, 100%. Because the size of the foreign particles in such a crystalline metal oxide film is small, the effect of the foreign particles on the device characteristics when a semiconductor device is fabricated is less, making the film suitable for use in semiconductor devices.

[0141] The crystalline metal oxide film had a density of 48 particles / cm2 observed from the surface of the film. ２ Less than 10 pieces / cm is preferable.２ Preferably, the density is 1 particle / cm or less. ２ It is more preferable that the number of foreign matters is less than 0.01 pieces / cm. There is no particular lower limit for the number of foreign matters. The fewer the number of foreign matters, the better. ２ Such a crystalline metal oxide film has better film smoothness and can therefore be more suitably used in semiconductor devices.

[0142] The crystalline metal oxide film may have a corundum structure, and such a crystalline metal oxide film has a corundum structure with better smoothness.

[0143] Furthermore, in the crystalline metal oxide film according to the present invention, the half-width of the rocking curve of the (006) plane X-ray diffraction peak is preferably less than 19.1 seconds, more preferably 9.4 seconds or less.

[0144] The measurement device and method for the (006) plane X-ray diffraction peak half-width are not particularly limited. For example, an X-ray diffractometer (SmartLab manufactured by Rigaku Corporation) is used to perform out-of-plane XRD 2θ / ω scan measurement of an oxide semiconductor film formed on a substrate, and the 2θ and ω at which the (006) plane peak is obtained are examined. Thereafter, the diffraction angle is fixed at 2θ at which the (006) plane peak is obtained, and ω scan is performed to measure the rocking curve half-width. The measurement conditions are not particularly limited, and can be, for example, as follows: Measurement equipment: SmartLab (product name) manufactured by Rigaku Analysis conditions Measurement method: Out-of-plane XRD method (2θ / ω scan) X-ray generator: Cu anticathode: Output 45 kV 200 mA Detector: Semiconductor detector Incident optical system: Ge (220) channel cut monochromator Soller slit: Incident side -: Receiving side 5.0° Slit: Incident side IS = 1 (mm): Length limit 0.5 (mm): Receiving side RS1 = 1 RS2 = 1.1 (mm) Scanning conditions: Scan axis 2θ / ω: Scanning mode Step measurement: Scan range 35 to 45°: Step width 0.005°: Integration time 0.5 sec. / step Measurement device: SmartLab (product name) manufactured by Rigaku Analysis conditions Measurement method: Rocking curve measurement (ω scan) X-ray generator: Cu anticathode: Output 45 kV 200 mA Detector: Semiconductor detector Incident optical system: Ge (220) channel cut monochromator Soller slit: Incident side -: Receiving side 5.0° Slit: Incident side IS = 1 (mm): Length limit 0.5 (mm): Receiving side RS1 = 1 RS2 = 1.1 (mm) Scanning conditions: Evaluation diffraction surface Ga ２ O ３ (006): Scan axis ω: Scan mode step measurement: Scan range 19-22°: Step width 0.005°: Integration time 0.5 sec. / step

[0145] Such a crystalline metal oxide film has better crystal orientation and can be suitably used in semiconductor devices. Note that the smaller the half-width of the rocking curve, the more preferable it is, so the lower limit is, for example, more than 0 seconds.

[0146] The crystalline metal oxide film can contain a dopant depending on the application. The dopant is not particularly limited. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, and p-type dopants such as copper, silver, tin, iridium, or rhodium. The dopant concentration is, for example, about 1.0×10 １６ ~1.0 x 10 ２２ / cm ３ may be about 1.0×10 １７ / cm ３ Even at a low concentration of about 1.0 × 10 ２０ / cm ３ A concentration higher than this may be used.

[0147] The thickness of the crystalline metal oxide film according to the present invention is not particularly limited, and may be, for example, 0.05 to 100 μm, preferably 0.1 to 50 μm, and more preferably 0.5 to 20 μm.

[0148] Furthermore, the crystalline metal oxide film according to the present invention preferably has a film thickness distribution of 4.6% or less, more preferably 2.8% or less, measured at at least 17 points within the surface. Such a film has a flatter surface and a more uniform film thickness, making it suitable for use in semiconductor devices. The smaller the film thickness distribution, the better, so the lower limit is, for example, greater than 0%.

[0149] Preferably, there are 17 or more measurement points, and although the number of measurement points and measurement positions are not particularly limited, it is preferable to set the measurement points symmetrically with respect to the center of the substrate. For example, in a polar coordinate system (r, θ) with the center of the substrate as the origin, where R is the radius of the substrate, 17 points can be set as follows: r = 0, R / 4, R / 2 θ = 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, 7π / 4, 2π. There is no particular upper limit on the number of measurement points, but it can be, for example, 81. If there are too many, the inspection process becomes complicated and productivity decreases.

[0150] Among the above measurement points, the maximum film thickness D Ｍａｘ , the minimum film thickness D Ｍｉｎ , average film thickness D Ａｖｅ Using this, the film thickness distribution χ [%] can be calculated using the following formula.

[0151]

[0152] The crystalline metal oxide film may be formed directly on a substrate, or may be laminated on an intermediate layer 252 (a buffer film or a release film) formed on a substrate 253 as shown in Fig. 17. The intermediate layer is not particularly limited as long as it is a metal oxide that can have a corundum structure, and may be primarily composed of an oxide containing any of aluminum, titanium, vanadium, chromium, iron, gallium, rhodium, indium, and iridium, for example.

[0153] More specifically, the intermediate layer is Al ２ O ３ , Ti ２ O ３ , V ２ O ３ , Cr ２ O ３ , Fe ２ O ３ , Ga ２ O ３ , Rh ２ O ３ , In ２ O ３ , Ir ２ O ３ Furthermore, when two elements selected from the above metal elements are designated as A and B, (A ｘ B １－ｘ ) ２ O３ Binary metal oxides represented by (0<x<1), or when three elements selected from the above metal elements are A, B, and C, (A ｘ B ｙ C １－ｘ－ｙ ) ２ O ３ The oxide may be a ternary metal oxide represented by (0<x<1, 0<y<1).

[0154] The crystalline metal oxide film preferably has a diameter of 10 cm (4 inches) or more. The upper limit of the area is not particularly limited, but it is preferably 750 cm. ２ The following is preferable, and in the case of a circle, it is preferable that the area corresponds to a diameter of 12 inches (300 mm) or less. Such a crystalline metal oxide film has better smoothness and a large area, and therefore can be more suitably used in semiconductor devices.

[0155] (Method for Producing Crystalline Metal Oxide Film) The method for producing a crystalline metal oxide film according to the present invention can be carried out by a mist CVD method including a microwave heating step, as will be described later.

[0156] 17 is a diagram showing one embodiment of the structure of a laminated structure according to the present invention. A laminated structure 250 having a crystalline metal oxide film according to the present invention basically includes a substrate 253 and a crystalline metal oxide film 251. In this case, the aforementioned intermediate layer 252 may be included between the substrate 253 and the crystalline metal oxide film 251.

[0157] The crystalline metal oxide film and stacked structure according to the present invention can be used in semiconductor devices by appropriately designing the structure, such as to form semiconductor layers in Schottky barrier diodes (SBDs), metal semiconductor field effect transistors (MESFETs), high electron mobility transistors (HEMTs), metal oxide semiconductor field effect transistors (MOSFETs), static induction transistors (SITs), junction field effect transistors (JFETs), insulated gate bipolar transistors (IGBTs), and light emitting diodes (LEDs).

[0158] (Semiconductor Device) The semiconductor device according to the present invention includes at least one of the above-described crystalline metal oxide film and the above-described stacked structure. For example, a semiconductor device (semiconductor element) such as a semiconductor laser, a diode, or a transistor can be provided. Such a semiconductor device may include a substrate or may have the substrate removed. The semiconductor device according to the present invention uses a high-quality crystalline metal oxide film with good flatness, and is a high-quality semiconductor device. Application examples (specific examples) of the semiconductor device are as follows.

[0159] (Examples of Applicable Semiconductor Devices) The above-described crystalline metal oxide film and stacked structure having the crystalline metal oxide film have good flatness and excellent electrical properties, and are industrially useful. Such crystalline metal oxide film and stacked structure having the crystalline metal oxide film can be suitably used in various semiconductor devices, and are particularly useful in power devices.

[0160] Semiconductor devices can be classified into horizontal elements (horizontal devices) in which an electrode is formed on one side of a crystalline metal oxide film, and vertical elements (vertical devices) in which an electrode is formed on both the front and back sides of a crystalline metal oxide film. The semiconductor device of the present invention can be suitably used in both horizontal and vertical devices, but is preferably used in vertical devices. Examples of semiconductor devices include Schottky barrier diodes (SBDs), metal-semiconductor field-effect transistors (MESFETs), high-electron-mobility transistors (HEMTs), semiconductor field-effect transistors (MOSFETs), junction field-effect transistors (JFETs), insulated-gate bipolar transistors (IGBTs), and light-emitting diodes (LEDs).

[0161] (Method for manufacturing a semiconductor device) First, a crystalline metal oxide film is formed on the main surface of a substrate, either directly or via another layer, to obtain a stacked structure according to the present invention. Then, electrodes and the like are formed on the crystalline metal oxide film to manufacture a semiconductor device. At this time, the stacked structure including the substrate and the crystalline metal oxide film can be used as is, or the substrate can be removed to leave the intermediate layer and the crystalline oxide semiconductor film, or the substrate and the intermediate layer can be removed to leave only the crystalline oxide semiconductor film. In this way, a high-performance semiconductor device can be manufactured using a high-quality crystalline metal oxide film with excellent flatness.

[0162] Below, preferred examples of the application of the crystalline metal oxide film of the present invention to an n-type semiconductor layer (such as an n+ type semiconductor or an n- type semiconductor layer) will be described with reference to the drawings, but the present invention is not limited to these examples. Note that the semiconductor elements exemplified below may further include other layers (such as an insulator layer or a conductor layer), and intermediate layers and buffer layers may be omitted as appropriate.

[0163] 18 shows an example of an SBD (Schottky barrier diode) according to the present invention. The SBD 300 includes a relatively lightly doped n-type semiconductor layer 301a, a relatively heavily doped n+ type semiconductor layer 301b, a Schottky electrode 302, and an ohmic electrode 303.

[0164] The material of the Schottky electrode 302 and the ohmic electrode 303 may be a known electrode material, and examples of this electrode material include metals such as aluminum, molybdenum, cobalt, zirconium, tin, niobium, iron, chromium, tantalum, titanium, gold, platinum, vanadium, manganese, nickel, copper, hafnium, tungsten, iridium, zinc, indium, palladium, neodymium, and silver, and alloys thereof; conductive metal oxide films such as tin oxide, zinc oxide, rhenium oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); organic conductive compounds such as polyaniline, polythiophene, and polypyrrole; and mixtures and laminates thereof.

[0165] The Schottky electrode 302 and the ohmic electrode 303 can be formed by known means such as vacuum deposition or sputtering. More specifically, when forming a Schottky electrode using two types of metals, a first metal and a second metal, among the above-mentioned metals, the Schottky electrode can be formed by stacking a layer made of the first metal and a layer made of the second metal, and then patterning the layer made of the first metal and the layer made of the second metal using a photolithography technique.

[0166] When a reverse bias is applied to the SBD 300, a depletion layer (not shown) expands into the n-type semiconductor layer 301a, resulting in a high-voltage SBD. When a forward bias is applied, electrons flow from the ohmic electrode 303 to the Schottky electrode 302. Therefore, the SBD according to the present invention is excellent for high-voltage and large-current applications, has a fast switching speed, and is excellent in voltage resistance and reliability.

[0167] 19 shows an example of a HEMT (High Electron Mobility Transistor) according to the present invention. HEMT 400 includes a wide bandgap n-type semiconductor layer 401, a narrow bandgap n-type semiconductor layer 402, an n+ type semiconductor layer 403, a semi-insulating layer 404, a buffer layer 405, a gate electrode 406, a source electrode 407, and a drain electrode 408.

[0168] 20 shows an example of a MOSFET (semiconductor field effect transistor) according to the present invention. The MOSFET 500 includes an n-type semiconductor layer 501, n+ type semiconductor layers 502 and 503, a gate insulating film 504, a gate electrode 505, a source electrode 506, and a drain electrode 507.

[0169] 21 shows an example of an IGBT (insulated gate bipolar transistor) according to the present invention. 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.

[0170] 22 shows an example of an LED (light emitting diode) according to the present invention. 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 light-transmitting electrode 705, and a second electrode 706.

[0171] Examples of materials for the transparent electrode include conductive oxide materials containing indium or titanium. ２ O ３ , ZnO, SnO ２ , Ga ２ O ３ , TiO ２ , CeO ２ Alternatively, a mixed crystal of two or more of these materials or a doped material thereof may be used. A translucent electrode can be formed by applying these materials by a known method such as sputtering. After the formation of the translucent electrode, thermal annealing may be performed to make the translucent electrode transparent.

[0172] Examples of materials for the first electrode 701 and the second electrode 706 include metals such as aluminum, molybdenum, cobalt, zirconium, tin, niobium, iron, chromium, tantalum, titanium, gold, platinum, vanadium, manganese, nickel, copper, hafnium, tungsten, iridium, zinc, indium, palladium, neodymium, and silver, and alloys thereof; conductive metal oxide films such as tin oxide, zinc oxide, rhenium oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); organic conductive compounds such as polyaniline, polythiophene, and polypyrrole; and mixtures thereof.

[0173] The method for forming the electrode film is not particularly limited, and the electrode can be formed on the substrate by a method appropriately selected from wet methods such as printing, spraying, and coating; physical methods such as vacuum deposition, sputtering, and ion plating; and chemical methods such as CVD and plasma CVD, taking into consideration the suitability for the material.

[0174] (Film Forming Method) Next, the film forming method of the present invention will be described. The film forming method of the present invention includes a step of atomizing or dropletizing a raw material solution to generate a mist, a step of transporting the mist to a film forming unit using a carrier gas, and a step of supplying the mist to a substrate through a nozzle in the film forming unit and heat-treating the mist on the substrate to form a film on the substrate, and in the step of forming a film on the substrate, the mist in the nozzle is irradiated with microwaves in a multimode manner to heat the mist.

[0175] According to this film formation method, only the mist can be selectively and rapidly heated out of the mist and carrier gas supplied to the substrate. This prevents the saturated water vapor pressure of the carrier gas from increasing, suppressing mist evaporation and thereby increasing the film formation rate while suppressing foreign matter and abnormal growth. Furthermore, since high-temperature mist can be supplied to the substrate, a decrease in the temperature of the substrate is suppressed even when the amount of mist supplied is increased, making it possible to form films at a high film formation rate even on large-diameter substrates without impairing crystallinity. Furthermore, by providing a nozzle for rectifying the mist and heating the mist inside the nozzle, it is possible to form films with excellent in-plane film thickness uniformity, and by heating a large amount of mist, it is possible to form films on multiple substrates simultaneously, improving productivity.

[0176] Hereinafter, an embodiment of the film forming method of the present invention will be described with reference to an example of a film forming method using the film forming apparatus 100 of the present invention shown in FIG.

[0177] First, a base (crystalline substrate) 110 is placed on a hot plate 108, and the hot plate 108 is operated. Flow rate control valves 103 a and 103 b are opened to supply carrier gas from a carrier gas source 102 a (main carrier gas) and a dilution carrier gas source 102 b (dilution carrier gas) into the film formation chamber 107 via a transfer unit 109, so that the atmosphere in the film formation chamber 107 is sufficiently replaced with the carrier gas, and the flow rates of the main carrier gas and the dilution carrier gas are adjusted and controlled, respectively.

[0178] [Step of atomizing or turning the raw solution into droplets to generate mist] The raw solution 104a is contained in the mist generating source 104 of the mist generating section 120, and the ultrasonic vibrator 106 is vibrated. The vibrations are propagated to the raw solution 104a through the water 105a, thereby atomizing or turning the raw solution 104a into droplets to generate mist.

[0179] The raw material solution 104a preferably contains a metal raw material and at least one solvent selected from water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, tetraethylene glycol, glycerol, benzyl alcohol, and dipropylene glycol.

[0180] By using such a solvent, it becomes possible to selectively and rapidly heat the mist by microwave heating.

[0181] The raw material solution (aqueous solution) 104a is not particularly limited as long as it contains a material that can be turned into a mist, and may be an inorganic material or an organic material. A solution of a metal or a metal compound is preferably used as the raw material solution 104a, and a solution containing one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt can be used, but a solution containing Ga is particularly preferred.

[0182] This allows stable α-Ga ２ O ３ A membrane can be prepared.

[0183] The raw material solution 104a is not particularly limited as long as it can turn the metal solution into mist, but a solution in which a metal is dissolved or dispersed in an organic solvent or water in the form of a complex or salt can be suitably used as the raw material solution 104a. Examples of the complex include an acetylacetonate complex, a carbonyl complex, an ammine complex, and a hydride complex. Examples of the salt include a metal chloride salt, a metal bromide salt, and a metal iodide salt.

[0184] Alternatively, the above metals may be dissolved in hydrobromic acid, hydrochloric acid, hydroiodic acid, or the like to form aqueous salt solutions. The solute concentration is preferably 0.01 to 1 mol / L, more preferably 0.05 to 0.5 mol / L, and even more preferably 0.08 to 0.30 mol / L. Within these concentration ranges, a decrease in the film formation rate and the introduction of foreign matter and abnormal growth due to side reactions and precipitation of excess raw materials can be efficiently prevented.

[0185] The solvent for dissolving the metal raw material in the present invention is one that has microwave absorption properties, and in addition to the above-mentioned alcohols such as water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, tetraethylene glycol, glycerol, benzyl alcohol, and dipropylene glycol, acidic solvents such as acetic acid, nitric acid, and formic acid, and basic solvents such as aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, and aqueous ammonia can also be used. Among these, it is particularly preferable to use a solvent that contains water as the main component. A solvent that contains water as the main component is less likely to leave impurities derived from the solvent in the film, has excellent atomization efficiency, and is advantageous in terms of cost.

[0186] In the present invention, the term "main component" refers to the component that is contained in the largest amount relative to all components, and means that it is contained in an amount of preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, and may be contained in an amount of 100% by mass.

[0187] The raw material solution 104a may be mixed with additives such as halogen-containing substances (e.g., hydrohalic acid) or oxidizing agents. Examples of hydrohalic acids include hydrobromic acid, hydrochloric acid, and hydroiodic acid, with hydrobromic acid and hydroiodic acid being preferred. Examples of oxidizing agents 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 ２hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, peracetic acid, nitrobenzene, and other organic peroxides.

[0188] Furthermore, when the film to be formed is a semiconductor, the raw material solution 104a may contain a dopant. The dopant is not particularly limited. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, and niobium, and p-type dopants such as copper, silver, tin, iridium, and rhodium. The concentration of the dopant is, for example, about 1.0×10 －９ It may be up to 1.0 mol / L, and may be about 1.0×10 －７ The concentration may be as low as 0.01 mol / L or less, or as high as about 0.01 mol / L or more.

[0189] In addition, a crystalline metal oxide film consisting of two or more metals (for example, α-(Al ｘ Ga １－ｘ ) ２ O ３ When forming a film (0≦X<1), the raw material solutions obtained by separately mixing the respective metal raw material solutions may be contained in the mist generating source 104 of one mist-forming unit 120 and turned into mist, or multiple mist-forming units may be provided and each metal raw material solution may be turned into mist in a different mist-forming unit. When multiple mist-forming units are provided, a mist mixer (not shown) may be provided to mix the respective misted raw material solutions, or the raw material solutions may be supplied separately to the film formation chamber 107 without providing a mist mixer.

[0190] [Step of transporting mist to film formation unit by carrier gas] In the step of transporting mist to the film formation unit by carrier gas, the mist is transported by the carrier gas from the mist-forming unit 120 to the film formation unit 140 via the transport unit 109, and is introduced into the film formation chamber 107. The mist transported by the carrier gas simultaneously passes through the microwave heating device 200 arranged in the film formation unit 140.

[0191] [Step of supplying mist to a substrate through a nozzle in a film-forming section and performing heat treatment on the substrate to form a film on the substrate] In microwave heating device 200, microwaves (2.45 GHz) generated by microwave oscillator 201 propagate through waveguide 205 and are irradiated to nozzle 150, which is disposed in applicator 204 and through which mist 220 and carrier gas pass. In addition, the temperature of the outlet portion of applicator 204 of nozzle 150 may be measured by optical fiber thermometer 207, and the output of microwave oscillator 201 may be automatically adjusted as appropriate so that the measured temperature remains constant.

[0192] Generally, to improve the film formation rate in the mist CVD method, it is necessary to increase the amount of mist supplied. However, supplying a large amount of mist lowers the temperature of the substrate 110 and reduces the crystallinity of the film. On the other hand, by performing microwave heating according to the present invention, high-temperature mist can be supplied onto the substrate 110, which prevents heat from being removed from the substrate 110 and improves the film formation rate while preventing a decrease in crystallinity.

[0193] Furthermore, when using heat transfer heating such as a heater, the temperature of not only the mist but also the carrier gas rises, increasing the saturated vapor pressure and promoting the evaporation of the mist. This makes it easier for the raw materials in the mist to precipitate, causing them to adhere to or become embedded in the film as foreign matter, thereby reducing film quality. On the other hand, microwave heating according to the present invention can directly heat the mist 220 without heating the carrier gas. As a result, the saturated vapor pressure does not increase, so the mist temperature can be increased without promoting the evaporation of the mist, improving the film formation rate without reducing film quality.

[0194] Furthermore, by using a multi-mode microwave heating method, it is possible to irradiate microwaves over a large space, so that a mist straightening component such as nozzle 150 can be provided, and by heating a large amount of mist, it is possible to supply heated mist to multiple substrates simultaneously to form films, resulting in excellent productivity.

[0195] There is no particular limitation on the method for controlling the microwave output. The output may be kept constant, or the temperature of the nozzle 150 may be measured and fed back to automatically adjust the output so that the temperature remains constant. However, controlling the temperature is more preferable because the temperature of the heated portion is less likely to fluctuate over time.

[0196] Although the temperature measurement method is not particularly limited, when measuring the temperature of the microwave irradiated portion, it is advisable to use an infrared radiation thermometer, an optical fiber thermometer, or the like depending on the object to be measured in order to prevent the thermometer 207 from absorbing microwaves. In this case, it is preferable that the temperature measuring portion of the optical fiber thermometer is made of a microwave-transparent material such as a non-metallic material.

[0197] The microwave irradiation intensity is not particularly limited and can be appropriately selected depending on the raw material solution, but when heating the mist, it is preferably 0.1 mW to 20 kW, and more preferably 1 mW to 500 W. If the irradiation intensity is in the range of 0.1 mW to 20 kW, the mist can be effectively heated and discharge within the applicator 204 can be effectively suppressed.

[0198] The microwave frequency is not particularly limited and can be appropriately selected depending on the physical properties of the raw material solution. For example, when water is used as the solvent, the microwave frequency is preferably 0.9 GHz or more and 300 GHz or less, at which point water can absorb the microwave.

[0199] If the frequency is within this range, the mist can be stably heated, and the penetration depth of the microwaves can be maintained at an appropriate length, allowing uniform heating to be achieved even inside the mist.

[0200] It is particularly preferable that the frequency of the microwaves be 2.45 GHz or more and 25 GHz or less.

[0201] A frequency within this range allows the mist to be heated more stably, and the penetration depth of the microwaves can be maintained at an appropriate length, allowing for more uniform heating to be achieved even inside the mist.

[0202] The mist heated as described above is supplied to the substrate 110 placed on the hot plate 108 , and is subjected to a heat treatment (thermal reaction) by the heat of the hot plate 108 in the film-forming chamber 107 , thereby forming a film on the substrate 110 .

[0203] The substrate 110 is not particularly limited as long as it can be formed on and support a film. It may be a known substrate. It may be an insulator, a conductor, a semiconductor, a single crystal, or a polycrystalline. Examples of the substrate include, but are not limited to, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel, and gold, silicon, sapphire, quartz, glass, gallium oxide, lithium niobate, and lithium tantalate.

[0204] It is also preferable to use a substrate 110 in which aluminum is the main component metal element contained in the greatest amount among the metal elements contained in the substrate 110. Among these, it is preferable to use a sapphire wafer from the viewpoints of quality and cost.

[0205] The plane orientation of the main surface of the substrate 110 is not particularly limited, and in the case of a sapphire wafer, a main plane such as the c-plane, m-plane, or a-plane can be used. The main surface may also have an off-angle with respect to the just plane. The off-angle is not particularly limited, but is preferably 0° to 15°.

[0206] The thickness of the substrate 110 is not particularly limited, but is preferably about 200 to 800 μm from the viewpoint of cost.

[0207] The film formation surface of the substrate 110 preferably has a diameter of about 10 cm (4 inches) or more, and more preferably a diameter of about 15 cm (6 inches) or more. There is no particular limit to the upper limit of the size of the film formation surface of the substrate 110, but it can be, for example, 30 cm (12 inches) in diameter.

[0208] By using a substrate 110 with a large diameter in this way, the crystalline metal oxide film formed on the substrate 110 can be made of even higher quality and with higher productivity.

[0209] The shape of the substrate 110 is not particularly limited in the present invention.

[0210] The substrate 110 may be placed face down on the top surface of the film formation chamber 107, or may be placed face up on the bottom surface of the film formation chamber 107.

[0211] The heat treatment (thermal reaction) of the mist supplied onto the substrate 110 is not particularly limited as long as the mist reacts when heated. The reaction conditions can be set appropriately depending on the raw material and the film to be formed. For example, the heating temperature is preferably in the range of 120 to 600°C, more preferably in the range of 200 to 600°C, and even more preferably in the range of 400 to 550°C.

[0212] The heat treatment (thermal reaction) may be carried out under any of a vacuum, a non-oxygen atmosphere, a reducing gas atmosphere, an air atmosphere, and an oxygen atmosphere, and may be appropriately set depending on the film to be formed. The reaction pressure may be any of atmospheric pressure, increased pressure, and reduced pressure, but film formation under atmospheric pressure is preferred because it simplifies the device configuration.

[0213] The film may be formed directly on the substrate 110, or may be laminated on an intermediate layer (a buffer film or a release film) formed on the substrate 110. The intermediate layer is not particularly limited as long as it is a metal oxide that can have a corundum structure, and may be primarily composed of, for example, an oxide containing any of aluminum, titanium, vanadium, chromium, iron, gallium, rhodium, indium, and iridium.

[0214] More specifically, Al ２ O ３ , Ti ２ O ３ , V ２ O ３ , Cr ２ O ３ , Fe ２ O ３ , Ga ２ O ３ , Rh ２ O ３ , In ２ O ３ , Ir ２ O ３Furthermore, when two elements selected from the above metal elements are designated as A and B, (A ｘ B １－ｘ ) ２ O ３ Binary metal oxides represented by (0<x<1), or when three elements selected from the above metal elements are A, B, and C, (A ｘ B ｙ C １－ｘ－ｙ ) ２ O ３ The oxide may be a ternary metal oxide represented by (0<x<1, 0<y<1).

[0215] Furthermore, in the step of forming a film on the substrate 110, the film can be formed on the substrate 110 while the substrate 110 is being moved.

[0216] The direction in which the base 110 is moved is not particularly limited. As shown in Fig. 5, there is a method in which a moving stage 161a on which the base 110 and the hot plate 108 are placed is provided, and the base 110 and the hot plate 108 move back and forth under the nozzle 150, or as shown in Fig. 6, there is a method in which a moving stage 161b on which the base 110 and the hot plate 108 are placed is used, and the base 110 and the hot plate 108 move in a rotational manner under the nozzle 150. In this case, a mechanism for rotating the base 110 about its own axis may be provided, and the base 110 may be rotated about its own axis.

[0217] By depositing the film while moving the substrate 110 in this way, it is possible to fabricate a film with improved uniformity.

[0218] In the present invention, an annealing treatment may be performed after the film formation. The temperature of the annealing treatment is not particularly limited, but is preferably 600°C or less, more preferably 550°C or less, so as not to impair the crystallinity of the film. The treatment time of the annealing treatment is not particularly limited, but is preferably 10 seconds to 10 hours, more preferably 10 seconds to 1 hour.

[0219] The crystalline metal oxide film formed by the above method may be peeled off from the substrate 110. The peeling method is not particularly limited and may be any known method. Examples include peeling by applying mechanical impact, peeling by applying heat and utilizing thermal stress, peeling by applying vibration such as ultrasonic waves, peeling by etching, and laser lift-off. The peeling method allows the crystalline metal oxide film to be obtained as a free-standing film.

[0220] Conventional methods can be used to form the electrodes required for constructing a semiconductor device. These methods include vapor deposition, sputtering, CVD, plating, and printing, which involves bonding with resins. Electrode materials include metals such as Al, Ag, Ti, Pd, Au, Cu, Cr, Fe, W, Ta, Nb, Mn, Mo, Hf, Co, Zr, Sn, Pt, V, Ni, Ir, Zn, In, and Nd; conductive metal oxide films such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and zinc indium oxide (IZO); and organic conductive compounds such as polyaniline, polythiophene, and polypyrrole. These materials may also be alloys or mixtures of two or more of these. The thickness of the electrode is preferably 1 to 1,000 nm, more preferably 10 to 500 nm.

[0221] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0222] Example 1 Gallium iodide was added to water to prepare a 0.1 mol / L aqueous solution, which was used as raw material solution 104a. The raw material solution 104a obtained as described above was placed in mist generating source 104. The temperature of the solution at this time was 25°C.

[0223] A 4-inch c-plane sapphire substrate was placed on the hot plate 108 in the film-forming chamber 107 as the substrate 110, and the hot plate 108 was operated to raise the temperature of the substrate 110 to 500°C.

[0224] Flow control valves 103a and 103b were opened to supply nitrogen gas as a carrier gas from carrier gas source 102a (main carrier gas) and dilution carrier gas source 102b (dilution carrier gas) into film formation chamber 107, and the atmosphere in film formation chamber 107 was thoroughly replaced with these carrier gases, while the flow rates of the main carrier gas and the dilution carrier gas were adjusted to 12 L / min and 12 L / min, respectively.

[0225] Next, the ultrasonic vibrator 106 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 104a through the water 105a, thereby turning the raw material solution 104a into mist and generating mist.

[0226] This mist was transported to the nozzle 150 via the supply pipe 109a by a carrier gas, and microwaves (2.45 GHz) were irradiated in the microwave heating device 200, and the heated mist was supplied to the substrate 110. In this case, the nozzle 150 was made of quartz, the nozzle discharge surface 152 was a rectangle with long sides of 120 mm and short sides of 5 mm, and the nozzle wall thickness was 2 mm. Furthermore, the nozzle discharge surface 152 and the surface of the substrate 110 were arranged so as to be parallel, and the distance between them was 2.5 cm.

[0227] The nozzle 150 and the applicator 204 were installed so that the nozzle 150 penetrated the applicator 204, as shown in Figures 7 and 8. At this time, the volume of the nozzle V [cm ３ ] and carrier gas flow rate Q [cm ３ / s] was V / Q=1.

[0228] The microwave output was controlled so that the temperature measured by the optical fiber thermometer was kept constant at 40°C.

[0229] Then, under atmospheric pressure and at 500° C., gas is exhausted from the exhaust port 112, and the substrate 110 is reciprocated under the nozzle 150 in the film-forming chamber 107 by the substrate moving mechanism shown in FIG. 5, and the mist is thermally reacted to form α-Ga ions having a corundum structure on the substrate 110. ２ O ３The film formation time was set to 1 hour, and the substrate 110 was moved so that the substrate 110 passed under the nozzle 150 once per minute. Furthermore, during the film formation process, the raw material solution 104a was appropriately replenished into the mist generating source 104 using a liquid replenishment mechanism (not shown) so that the water level of the raw material solution 104a in the mist generating source 104 during film formation was kept constant.

[0230] (Example 2) Film formation was performed under the same conditions as in Example 1, except that the nozzle discharge surface 152 was a circle with an inner diameter of 30 mm, the nozzle 150 had a wall thickness of 2 mm, and the applicator 204 was a cylindrical cavity resonator with an internal space having a diameter of 91 mm.

[0231] Comparative Example 1 Using a film formation apparatus not including the microwave irradiation device 200, film formation was carried out under the same conditions as in Example 1, except that microwave irradiation was not performed and the film formation time was set to 2 hours.

[0232] (Comparative Example 2) Using a film formation apparatus that did not have the microwave irradiation device 200, film formation was performed under the same conditions as in Example 1, except that microwave irradiation was not performed and the entire supply pipe 109a was heated at a set temperature of 40°C using a ribbon heater.

[0233] Example 3 As a raw material, gallium acetylacetonate was dissolved in a hydrochloric acid aqueous solution (1.0 vol %) to prepare a 0.1 mol / L aqueous solution, which was used as raw material solution 104a; the flow rates of the main carrier gas and the dilution carrier gas were adjusted to 18 L / min and 6 L / min, respectively; a 6-inch sapphire substrate was used as base 110; and the microwave output was controlled so that the temperature of an optical fiber thermometer reached 50°C. Film formation was performed under the same conditions as in Example 1, except for the following.

[0234] Comparative Example 3 A film was formed using a film forming apparatus not including the microwave irradiation device 200 under the same conditions as in Example 3, except that microwave irradiation was not performed.

[0235] Example 4 As a raw material, gallium acetylacetonate was dissolved in a hydrochloric acid aqueous solution (1.0 vol %) to prepare a 0.1 mol / L aqueous solution, to which 10 vol % formic acid was added, and the solution was used as raw material solution 104a. The flow rates of the main carrier gas and the dilution carrier gas were adjusted to 24 L / min and 0 L / min, respectively. An 8-inch sapphire substrate was used as the base 110. The microwave output was controlled so that the temperature measured by the optical fiber thermometer reached 75°C. Except for this, film formation was performed under the same conditions as in Example 1.

[0236] [Evaluation 1: Film Thickness Measurement] The film thickness of the films prepared in Examples 1-4 and Comparative Examples 1-3 was measured using an optical interference film thickness meter F50. The measurement points were 25 points expressed by the polar coordinate system (r, θ) with the center of the substrate as the origin, where r = 0, R / 4, R / 2, 3R / 4, θ = 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / 2, 7π / 4, 2π, where R is the radius of the substrate. Among the above measurement points, the maximum film thickness D Ｍａｘ , the minimum film thickness D Ｍｉｎ , average film thickness D Ａｖｅ Using the above, the film thickness distribution χ [%] was calculated using the following formula.

[0237]

[0238] In addition, the average film thickness D Ａｖｅ The film formation rate was calculated from the average film thickness. Ａｖｅ The film formation rate (μm / hour) was calculated as follows: (μm)÷film formation time (hours)=film formation rate (μm / hour).

[0239] [Evaluation 2: Crystal structure and crystallinity evaluation] The crystal structure of the prepared film was evaluated by XRD 2θ-ω scanning. ２ O ３ Thereafter, the (006) plane rocking curve was measured, and the half-value width of the (006) plane was measured.

[0240] [Evaluation 3: Measurement of the number of foreign particles and the number of abnormally grown areas] For the crystalline metal oxide films formed in Examples 1-4 and Comparative Examples 1-3, the number of foreign particles was counted in a dark field image at 20x magnification using an optical microscope. ２Observe and 1 cm ２ The number of foreign particles (= foreign particle density) was calculated. Examples of observed foreign particles are shown in Figure 9, and examples of abnormal growth locations are shown in Figure 10.

[0241] The foreign matter in Figure 9 appears to be a raw material deposit formed when the mist evaporates before reaching the substrate. The foreign matter can be observed as bright spots in a dark field microscope, as described above, and can also be counted using an electron microscope such as an SEM, a surface inspection machine that detects defects using differences in scattered light intensity, or a surface inspection device that takes images using a microscope and classifies them using machine learning. In this evaluation, particles between 0.01 μm and 10 μm in size were counted as foreign matter.

[0242] As shown in Figure 10, the abnormal growth area was circular with a diameter of 10 to 100 μm, and crystals other than the α phase were observed near the center. Cross-sectional analysis of the abnormal growth area revealed foreign matter measuring up to several μm in size at the bottom of the abnormal growth area, and a region that appeared to be a crystalline phase was present above the foreign matter. Analysis by electron beam diffraction revealed that the electron beam diffraction pattern in the flat area outside the abnormal growth area in Figure 10 was α-Ga as shown in Figure 11. ２ O ３ 10, the electron diffraction image of the crystalline portion of the region that appears to be a crystalline phase above the foreign material is α-Ga as shown in FIG. ２ O ３ This is because the Ga ２ O ３ It is believed that another crystalline phase (likely γ) was formed. The electron beam diffraction was performed under the following conditions.

[0243] Selected area electron diffraction method Transmission electron microscope: Hitachi High-Technologies H-9500 Acceleration voltage: 300 kV Camera length: 1.0 m Selected area: approx. 140 nmφ

[0244] The abnormal growth areas can be observed as bright spots in a dark-field image of a microscope, and the number of defects can be measured using an electron microscope such as an SEM, a surface inspection machine that detects defects using differences in scattered light intensity, or a surface inspection device that takes images with a microscope and classifies them using machine learning. Whether the defect is a γ phase or not can be determined by crystal orientation analysis such as the EBSD method. The results of evaluations 1 to 3 above are summarized in Table 1.

[0245]

[0246] [Evaluation 3-2: Measurement of particle size distribution of foreign matter] For the crystalline metal oxide films produced in Example 1 and Comparative Example 1, a machine learning type surface inspection device equipped with a confocal microscope was used to detect foreign matter observed from the surface direction of the film, and the particle size of the detected foreign matter was measured using a review function, and a particle size distribution of the foreign matter was created.

[0247] The particle diameter here is the equivalent circle diameter in a two-dimensional image observed from the surface direction of the crystalline metal oxide film. The equivalent circle diameter is the diameter of a circle having an area equivalent to the area of ​​the particle captured in the two-dimensional image, and the particle area can be calculated by image analysis. For example, an optical microscope using Optelics AI manufactured by Lasertec Corporation can be used. ２ The results are shown in Table 2.

[0248] As shown in Table 2, the mode of particle size of the foreign matter in Example 1 was 0.225 μm, and no particles of 0.5 μm or larger were observed. The particle size (D50) at which the cumulative frequency was 50% was 0.225 μm. The standard deviation σ was 0.08 μm. The ratio (D90 / D10) of the particle size (D90) at which the cumulative frequency was 90% to the particle size (D10) at which the cumulative frequency was 10% was 2.6.

[0249] The density of foreign matter obtained by dividing the number of foreign matter by the observation area was 0.4 pieces / cm ２ The ratio of foreign matter having a particle size of not less than particle size D50 - standard deviation σ and not more than particle size D50 + standard deviation σ to the total number of foreign matter was 75%.

[0250] In Comparative Example 1, larger particles were observed than in Example 1. The mode of particle size of the foreign matter was 3.25 μm. The particle size (D50) at which the cumulative frequency was 50% was 2.75 μm. The standard deviation was 1.25 μm. The ratio (D90 / D10) of the particle size (D90) at which the cumulative frequency was 90% to the particle size (D10) at which the cumulative frequency was 10% was 5.7.

[0251] The density of foreign matter obtained by dividing the number of foreign matter by the observation area is 47.8 pieces / cm ２ The ratio of foreign matter having a particle size of not less than particle size D50 - standard deviation σ and not more than particle size D50 + standard deviation σ to the total number of foreign matter was 59%.

[0252] A comparison between Example 1 and Comparative Example 1 reveals that there are fewer foreign matters and the variation in particle size of the foreign matters is small in Example 1, in which the mist is irradiated with microwaves. When a semiconductor device is fabricated using the crystalline metal oxide film having fewer foreign matters and a small variation in particle size of the foreign matters as in Example 1, the influence of the foreign matters on the device characteristics is minor, as will be described later.

[0253] Example 5 The crystalline metal oxide films produced in Example 1 and Comparative Example 1 were subjected to measurement of the in-plane distribution of foreign matter using a machine learning type surface inspection device.

[0254] Specifically, an automatic inspection device equipped with a microscope, an electric XY stage on which the wafer to be observed is placed and which can be electrically moved in the X and Y directions, an imaging camera such as a digital camera, and a controller for controlling the automatic inspection device was used, and by setting the coordinates so that the center of the substrate was the origin and controlling the electric XY stage so that the field of view size of the microscope image was 1 x 1 mm, the entire surface of the wafer was automatically photographed with the imaging camera at 2 mm intervals. For example, for a wafer with a diameter of 4 inches, 1789 points (= 17.89 cm ２ The total area of ​​the field of view was 22.8% of the surface area of ​​the crystalline metal oxide film.

[0255] The number of foreign objects in the automatically captured images was determined, and the microscopic images were classified.

[0256] FIG. 14 shows a foreign matter map in which areas where foreign matter was visible under the microscope are colored black and areas where no foreign matter was visible are colored white.

[0257] Next, the microscopic images determined to contain foreign matter were classified according to the number of foreign matter in each microscopic image. In the present invention, even partially visible foreign matter was counted as one. The results of tallying the number of foreign matter found in the microscopic images are shown in Figure 15.

[0258] In Example 1, 99.4% of the microscopic images showed zero foreign matter, 0.6% of the microscopic images showed one foreign matter, and 0% of the microscopic images showed two or more foreign matter. Furthermore, when the foreign matter density was calculated from this measurement, it was found to be 0.5 / cm in Example 1. ２ It was.

[0259] In Comparative Example 1, 63.0% of the microscopic images showed zero foreign matter, 27.0% showed one foreign matter, and 10.0% showed two or more foreign matter. The foreign matter density was calculated from this measurement and was 48.7 / cm ２ It was.

[0260] A comparison between Example 1 and Comparative Example 1 reveals that in Example 1, in which microwaves were irradiated onto the mist, the variation in the location of foreign matter generation was small, and foreign matter generation at the same location was low. When a semiconductor device is fabricated using such a crystalline metal oxide film, the impact of foreign matter on the device characteristics is negligible, as will be described later.

[0261] [Evaluation 4: Evaluation of Electrical Characteristics] For the crystalline metal oxide films prepared in Example 1 and Comparative Example 1, an SBD, which is a semiconductor device, was prepared in the 1×1 mm portion photographed in Example 5.

[0262] The current-voltage characteristics of the obtained semiconductor devices were evaluated. The voltage at which breakdown occurred was determined by measuring the reverse current-voltage characteristics. Semiconductor devices with a breakdown voltage of 600 V or more were considered to be acceptable products, and the yield was calculated by dividing the number of acceptable products by the total number of semiconductor devices produced = yield [%]. The yield of Example 1 was 98%, and the yield of the film of Comparative Example 1 was 44.9%.

[0263] The film produced in Comparative Example 1 had large foreign particles unevenly distributed, which had a large impact on device characteristics and resulted in a low yield of less than 50%. On the other hand, the film produced in Example 1 had small foreign particles and little uneven distribution of foreign particle positions, which resulted in little impact on device characteristics and a high yield of 95% or more.

[0264] Next, the yield was plotted for each number of foreign particles in one microscope image taken in Example 5, and the results are shown in Figure 16. Here, the data was compiled from all the semiconductor devices (1,789 devices) produced in this evaluation, excluding devices in which abnormally grown portions such as those shown in Figure 10 were observed. The yield of devices in which abnormally grown portions such as those shown in Figure 10 were observed was 0%. It can be seen that the presence of foreign particles in the film causes a rapid drop in yield, and in particular, the presence of two or more foreign particles almost always results in a rejection.

[0265]

[0266] Example 6 Film formation was performed under the same conditions as in Example 1, except that a film formation apparatus 100 equipped with a rotary moving mechanism 160b for rotating and revolving a substrate as shown in FIG. 13 was used, four 4-inch sapphire substrates were placed on the moving mechanism 160b, the nozzle 150 was made of quartz, the nozzle discharge surface 152 was circular with an inner diameter of 50 mm, the nozzle wall thickness was 2 mm, and the flow rates of the main carrier gas and dilution carrier gas were adjusted to 50 L / min and 10 L / min, respectively.

[0267] The film thickness and crystallinity of each of the four samples after deposition were evaluated, and the variation in the measured values ​​for the four samples was found to be within about 3%. The variation here is an index expressed as (maximum value - minimum value) / (maximum value + minimum value) x 100 (%).

[0268] Next, foreign substance maps were created for four samples in the same manner as in Example 5. Two foreign substance maps were overlaid and the degree of agreement between each map was evaluated. The degree of agreement (%) was 99.0% or higher for all two maps. The degree of agreement (%) was calculated as follows: (number of matching colors (black and white) in the foreign substance maps) / (total number of foreign substance map images (= 1,789)) × 100. For example, when two foreign substance maps, each containing 50 microscopic images in which black foreign substances were detected, are overlaid, if all the black positions do not match, the degree of agreement is (1,789 - 50 × 2) / 1,789 × 100 = 94.4%.

[0269] A comparison of Examples 1-5 and Comparative Examples 1-3 confirmed that Examples 1-5 of the present invention are a film-forming method in which a mist of a raw material solution is heat-treated on a substrate to form a crystalline metal oxide film, and that by irradiating microwaves onto the mist in the nozzle to heat it, foreign matter and abnormalities are suppressed, and a film with good crystallinity and good in-plane uniformity in film thickness can be formed at high speed. Furthermore, Example 6 demonstrated that films could be formed on multiple substrates with little variation.

[0270] This specification includes the following aspects: [1]: A film formation apparatus including a mist-forming unit that generates mist by misting a raw material solution, a carrier gas supply unit that supplies a carrier gas that transports the mist, a film formation unit that heat-treats the mist to form a film on a substrate, and a transport unit that connects the mist-forming unit with the inside of the film formation unit and transports the mist by the carrier gas, wherein the film formation unit includes a nozzle that supplies the rectified mist to the substrate, and a microwave heating device that irradiates the mist in the nozzle with microwaves in a multimode system to heat the mist. [2]: The film formation apparatus of [1] above, wherein the microwave heating device comprises a microwave generating unit, a microwave irradiating unit that irradiates the mist with microwaves generated by the microwave generating unit, and a microwave guide unit through which the microwaves propagate from the microwave generating unit to the microwave irradiating unit, and the microwave irradiating unit comprises a wall surface that diffusely reflects the microwaves to irradiate the mist with the microwaves. [3]: The film formation apparatus of [1] above or [2] above, wherein the portion of the nozzle that is irradiated with the microwaves is formed from a microwave-transparent material. [4]: ​​The film formation apparatus of [1] above, [2] or [3] above, wherein the portion of the nozzle that is irradiated with the microwaves is formed from any one of quartz, ceramic, alumina, polytetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, and polyether ether ketone resin. [5]: The film forming apparatus according to the above [1], [2], [3] or [4], wherein the representative length of the ejection surface of the nozzle that ejects the mist is greater than 3 cm. [6]: The film forming apparatus according to the above [1], [2], [3], [4] or [5], wherein the film forming unit includes a movement mechanism that moves the substrate.[7]: A film formation method including the steps of atomizing or dropletizing a raw material solution to generate a mist, transporting the mist to a film formation unit using a carrier gas, and supplying the mist to the substrate through a nozzle in the film formation unit and heat-treating the mist on the substrate to form a film on the substrate, wherein the film formation step includes irradiating the mist in the nozzle with microwaves in a multimode manner to heat the mist. [8]: The film formation method of [7] above, including using a raw material solution containing a metal raw material and at least one solvent selected from water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, tetraethylene glycol, glycerol, benzyl alcohol, and dipropylene glycol. [9]: The film formation method of [7] or [8] above, including using a solvent for the raw material solution containing water as a main component.

[10] : The film formation method of [8] or [9] above, including using a solvent containing Ga as the metal raw material.

[11] : The film formation method according to [7], [8], [9] or

[10] above, which comprises using a substrate having a film formation surface with a diameter of 10 cm (4 inches) or more as the substrate.

[12] : The film formation method according to [7], [8], [9],

[10] or

[11] above, which comprises, in the step of forming a film on the substrate, forming a film on the substrate while moving the substrate.

[13] : The film formation method according to [7], [8], [9],

[10] ,

[11] or

[12] above, which comprises setting the frequency of the microwave to 0.9 GHz or more and 300 GHz or less.

[14] : The film formation method according to [7], [8], [9],

[10] ,

[11] ,

[12] or

[13] above, which comprises setting the frequency of the microwave to 2.45 GHz or more and 25 GHz or less.

[15] : A crystalline metal oxide film containing at least one of gallium and aluminum as a main component, wherein the field area per sheet is 1 mm for a plurality of points on the surface of the crystalline metal oxide film. ２

[16] : A crystalline metal oxide film in which a number density of the foreign particles observed from the surface direction of the crystalline metal oxide film is 48 particles / cm or less and a plurality of microscopic images having the same field of view area are obtained so that the total field of view area is 20% or more of the surface area of ​​the crystalline metal oxide film and the fields of view do not overlap, and when the number of foreign particles contained in each of the obtained microscopic images is determined, the ratio of the number of microscopic images determined to contain a plurality of foreign particles to the total number of the obtained microscopic images is less than 10%. ２

[17] : The crystalline metal oxide film of

[15] above, wherein the film thickness distribution measured at 17 or more points on the crystalline metal oxide film is 4.6% or less.

[18] : The crystalline metal oxide film of

[15] above,

[16] above, or

[17] above, wherein the film thickness distribution measured at 17 or more points on the crystalline metal oxide film is 4.6% or less.

[19] : The crystalline metal oxide film of

[15] above,

[16] above,

[17] above, or

[18] above, wherein the half-width of the rocking curve of the (006) plane of the crystalline metal oxide film measured by X-ray diffraction is less than 19.1 seconds.

[20] : The crystalline metal oxide film of

[15] above,

[16] above,

[17] above,

[18] above, or

[19] above, wherein the surface of the crystalline metal oxide film has a diameter of 10 cm (4 inches) or more.

[21] : A laminated structure having a substrate, a buffer layer on the substrate, and a crystalline metal oxide film on the buffer layer, the crystalline metal oxide film of

[15] ,

[16] ,

[17] ,

[18] ,

[19] , or

[20] .

[22] : A semiconductor device including at least one of the crystalline metal oxide film of

[15] ,

[16] ,

[17] ,

[18] ,

[19] , or

[20] or the laminated structure of

[21] .

[23] : The semiconductor device of

[22] , which is a semiconductor laser, a diode, or a transistor.

[0271] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A film formation apparatus comprising: a mist generation section which generates a mist by turning a raw material solution into a mist; a carrier gas supply section which supplies a carrier gas which transports the mist; a film formation section which heat-treats the mist to form a film on a substrate; and a transport section which connects the mist generation section with the inside of the film formation section and transports the mist by the carrier gas, wherein the film formation apparatus further comprises: a nozzle in the film formation section for supplying the rectified mist to the substrate; and a microwave heating device which irradiates the mist in the nozzle with microwaves in a multi-mode manner to heat the mist.

2. The film forming apparatus of claim 1, characterized in that the microwave heating device comprises: a microwave generating unit; a microwave irradiation unit that irradiates the mist with microwaves generated in the microwave generating unit; and a microwave guide unit through which the microwaves propagate from the microwave generating unit to the microwave irradiation unit, and the microwave irradiation unit has a wall surface for irradiating the microwaves to the mist by diffusely reflecting the microwaves.

3. The film forming apparatus according to claim 1, wherein the portion of the nozzle onto which the microwaves are irradiated is made of a microwave-transparent material.

4. The film forming apparatus according to claim 1, wherein the portion of the nozzle onto which the microwaves are irradiated is formed from any one of quartz, ceramic, alumina, polytetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, and polyether ether ketone resin.

5. The film forming apparatus according to claim 1, wherein a representative length of the ejection surface of the nozzle from which the mist is ejected is greater than 3 cm.

6. The film forming apparatus according to any one of claims 1 to 5, wherein the film forming section is provided with a moving mechanism for moving the substrate.

7. A film formation method comprising: a step of generating a mist by atomizing or converting a raw material solution into droplets; a step of transporting the mist to a film formation section by a carrier gas; and a step of supplying the mist to the substrate through a nozzle in the film formation section and heat-treating the mist on the substrate to form a film on the substrate, characterized in that in the step of forming a film on the substrate, microwaves are irradiated to the mist in the nozzle using a multi-mode method to heat the mist.

8. The film forming method according to claim 7, characterized in that the raw material solution contains a metal raw material and at least one solvent selected from the group consisting of water, methanol, ethanol, ethylene glycol, diethylene glycol, propylene glycol, tetraethylene glycol, glycerol, benzyl alcohol, and dipropylene glycol.

9. The film forming method according to claim 8, wherein the solvent for said raw material solution is a solvent containing water as a main component.

10. The film forming method according to claim 8, wherein the metal source contains Ga.

11. The method according to claim 7, wherein the substrate has a film-forming surface having a diameter of 10 cm (4 inches) or more.

12. The method according to claim 7, wherein in the step of forming a film on the substrate, the film is formed on the substrate while the substrate is being moved.

13. A film forming method according to any one of claims 7 to 12, characterized in that the frequency of the microwaves is 0.9 GHz or more and 300 GHz or less.

14. The film forming method according to claim 13, wherein the frequency of the microwaves is set to be not less than 2.45 GHz and not more than 25 GHz.

15. A crystalline metal oxide film containing at least one of gallium and aluminum as a main component, wherein the field area of ​​each of the multiple points on the surface of the crystalline metal oxide film is 1 mm ２ a plurality of microscopic images each having the same field of view area and each of which is equal to or smaller than 20% of the surface area of ​​the crystalline metal oxide film and each of which has no overlapping fields of view; and when the number of foreign matter contained in each of the obtained microscopic images is determined for each of the obtained microscopic images, the ratio of the number of the microscopic images determined to contain multiple foreign matter to the total number of the obtained microscopic images is less than 10%.

16. The density of the foreign matter observed from the surface direction of the crystalline metal oxide film is 48 particles / cm ２ 16. The crystalline metal oxide film of claim 15, wherein the crystalline metal oxide film has a molecular weight of less than 1000 nm.

17. The crystalline metal oxide film according to claim 15, wherein the film thickness distribution measured at 17 or more points on the crystalline metal oxide film is 4.6% or less.

18. The crystalline metal oxide film according to claim 15, which has a corundum structure.

19. The crystalline metal oxide film according to claim 15, characterized in that the half-width of the rocking curve of the (006) plane of said crystalline metal oxide film by X-ray diffraction is less than 19.1 s.

20. The crystalline metal oxide film of claim 15, wherein the surface of said crystalline metal oxide film is 10 cm (4 inches) or greater in diameter.

21. A laminated structure comprising a substrate, a buffer layer on the substrate, and the crystalline metal oxide film according to claim 15 on the buffer layer.

22. A semiconductor device comprising at least one of the crystalline metal oxide film according to any one of claims 15 to 20 and the laminated structure according to claim 21.

23. The semiconductor device according to claim 22, wherein the semiconductor device is any one of a semiconductor laser, a diode, and a transistor.

Images