Patent Application
20240170285
The present disclosure relates to a crystalline oxide film that is useful in a semiconductor device, and a semiconductor device using the crystalline oxide film.
Germanium oxide is of interest for use as a wide band gap semiconductor that is useful in a power device or the like. Germanium oxide has a reported band gap of from 4.44 eV to 4.68 eV and has a first-principles predicted Hall mobility of 27 cm2/Vs (in a direction perpendicular to a c-axis) or 29 cm2/Vs. Thus, use in a p-n homojunction is expected.
Research is also being conducted on actually creating germanium oxide, rather than just making predictions such as those above. For example, one known technique is using an MBE method to form a film of germanium oxide on an R-plane sapphire substrate via an (Sn,Ge)O2 buffer layer. Forming a (Sn,Ge)O2 film having a rutile-type structure on a (001)TiO2 substrate using a hybrid MBE method is also known.
According to an example of the present disclosure, there is provided a crystalline oxide film including an oxide of germanium, an area percentage of abnormal grains determined by surface SEM observation being 3% or less.
Thus, a crystalline oxide film according to the present disclosure has reduced abnormal grains and good crystallinity.
The present inventors researched diligently and were successful for the first time in the world in fabricating, by creating geranium oxide on a tetragonal crystal substrate under specific conditions using a mist CVD method, a crystalline oxide film containing an oxide of germanium, in which an area percentage of abnormal grains determined by surface SEM observation is 3% or less. The present inventors also found that such a crystalline oxide film may solve the related art problem mentioned above.
Embodiments of the present disclosure will be described below with reference to the accompanying drawings. In the following description, the same parts and components are designated by the same reference numerals. The present embodiment includes, for example, the following disclosures.
A crystalline oxide film including an oxide of germanium, an area percentage of abnormal grains determined by surface SEM observation being 3% or less.
The crystalline oxide film according to [Structure 1], wherein the crystalline oxide film has a film thickness of 100 nm or more.
The crystalline oxide film according to [Structure 1] or [Structure 2], wherein a region in which the area percentage of the abnormal grains determined by surface SEM observation is 3% or less exists over an area of at least 0.04 mm2.
The crystalline oxide film according to any one of [Structure 1] to [Structure 3], wherein the crystalline oxide film has a surface roughness of 10 nm or less.
The crystalline oxide film according to any one of [Structure 1] to [Structure 4], wherein the crystalline oxide film has a tetragonal crystal structure.
The crystalline oxide film according to any one of [Structure 1] to [Structure 5], wherein the crystalline oxide film is a uniaxially oriented film.
The crystalline oxide film according to any one of [Structure 1] to [Structure 6], wherein the crystalline oxide film has a full width at half maximum determined by X-ray diffraction measurement of 1000 arcsec or less.
[Structure 8]
A semiconductor device including at least a crystalline oxide film and an electrode, the crystalline oxide film being the crystalline oxide film described in any one of [Structure 1] to [Structure 7].
A power conversion device using the semiconductor device described in
A control system using the semiconductor device described in [Structure 8].
A crystalline oxide film according to the present disclosure is a crystalline oxide film containing an oxide of germanium, in which an area percentage of abnormal grains determined by surface scanning electron microscope (SEM) observation is 3% or less. In an embodiment of the present disclosure, the area percentage of the abnormal grains is preferably 1% or less. The term “abnormal grains” herein refers to grains observed as a region having a different height from its surroundings by surface SEM observation. The area percentage of the abnormal grains is calculated as the area percentage of a region having a different height to a flat portion, relative to the total area of the observed region, by surface SEM observation over an area of at least 100 μm square. In an embodiment of the present disclosure, a region in which the area percentage of the abnormal grains determined by surface SEM observation is 3% or less preferably exists over an area of at least 0.04 mm2. In the crystalline oxide film, an atomic ratio of germanium in a metal element in the film is preferably greater than 0.5. The crystal structure of the crystalline oxide film is also not particularly limited. Examples of the crystal structure of the crystalline oxide film include a hexagonal crystal structure and a tetragonal crystal structure. In an embodiment of the present disclosure, the crystalline oxide film preferably has a tetragonal crystal structure, and more preferably has a rutile-type structure. The crystalline oxide film may be composed of a single crystal or may be composed of many crystals. In an embodiment of the present disclosure, the crystalline oxide film is preferably a single crystal.
In an embodiment of the present disclosure, the crystalline oxide film is also preferably a uniaxially oriented film, and is preferably oriented to a crystallographic axis direction perpendicular or parallel to the c-axis. The term “c-axis” herein refers to an axis perpendicular to the (001) plane in a tetragonal system. Additionally, the phrase “crystallographic axis direction perpendicular to the c-axis” also includes a crystallographic axis substantially perpendicular to the c-axis (within ±10% of a direction perpendicular to the c-axis). The phrase “crystallographic axis direction parallel to the c-axis” also includes a crystallographic axis direction substantially parallel to the c-axis (within ±10% of a direction parallel to the c-axis). In the present disclosure, the crystalline oxide film is preferably oriented in a crystallographic axis direction parallel to the c-axis and preferably oriented to the c-axis direction. Note that, the term “oriented” refers to a state in which the crystal faces represented by the (001) plane, for example, are aligned in a particular direction. The state of orientation may be confirmed by X-ray diffraction. More specifically, in a case where the crystalline oxide film is oriented to the (001) plane, for example, it may be determined that the crystalline oxide film is oriented to the (001) plane when the ratio of the integrated intensity ratio of peaks derived from the (001) plane to peaks derived from other crystal planes is greater than the ratio of the integrated intensity ratio of peaks derived from the (001) plane to peaks derived from other crystal planes in the same randomly oriented crystal. Additionally, in an embodiment of the present disclosure, the rocking curve full width at half maximum determined by X-ray diffraction measurement in the crystallographic axis direction of orientation as described above is preferably 1000 arcsec or less, more preferably 600 arcsec or less.
The film thickness of the crystalline oxide film is not particularly limited. In an embodiment of the present disclosure, the film thickness is preferably 100 nm or more, more preferably 200 nm or more. Additionally, in an embodiment of the present disclosure, a surface roughness (RMS) of the crystalline oxide film is preferably 10 nm or less, more preferably 1 nm or less. By setting such a preferred film thickness or surface roughness, the semiconductor device may be provided with better breakdown voltage resistance when the crystalline oxide film is applied to the semiconductor device. Note that, the surface roughness (RMS) is a value obtained by performing a calculation using the surface profile measurement results for a region of 10 μm square by an atomic force microscope (AFM) in accordance with JIS B0601 and using the obtained value.
In an embodiment of the present disclosure, the crystalline oxide film preferably contains an oxide of germanium having a rutile-type structure. In an embodiment of the present disclosure, the crystalline oxide film more preferably contains the oxide of germanium as a major component. Note that, the term “major component” here means that the amount of the oxide of germanium (germanium oxide) in the crystalline oxide film is 50% or more in terms of the composition ratio in the crystalline oxide film. In an embodiment of the present disclosure, the content of the oxide of germanium in the crystalline oxide film is preferably 70% or more, more preferably 90% or more in terms of the composition ratio in the crystalline oxide film. The oxide of germanium is not particularly limited provided that the oxide is a compound of oxygen and germanium. Additionally, the crystalline oxide film may include another metal other than germanium. An example of the other metal is a Group 14 metal other than germanium (e.g., tin or silicon). The atomic ratio of germanium in a metal element in the crystalline oxide film is not particularly limited provided that the atomic ratio is greater than 0.5. In an embodiment of the present disclosure, the atomic ratio of germanium in a metal element in the crystalline oxide film is preferably 0.7 or more, more preferably 0.9 or more. With germanium in the above preferable range, a crystalline oxide film having a higher band gap (e.g., 4.0 eV or more, more preferably 4.4 eV or more) may be achieved.
The crystalline oxide film also preferably contains a dopant. The dopant is not particularly limited unless it interferes with the present disclosure. The dopant may be an n type dopant or a p type dopant. Examples of the n type dopant include antimony (Sb), arsenic (As), bismuth (Bi), and fluorine (F). In an embodiment of the present disclosure, the n type dopant is preferably antimony (Sb). Examples of the p type dopant include aluminum (Al), gallium (Ga), and indium (In). The amount of the dopant in the crystalline oxide film is not particularly limited unless it interferes with the present disclosure. Specifically, the amount of the dopant in the crystalline oxide film may be approximately 1×1016/cm3 to 1×1022/cm3 and, according to the present disclosure, the dopant may be provided in a high concentration of approximately 1×1020/cm3 or more.
The crystal substrate is not particularly limited unless it interferes with the present disclosure, and a known substrate may be used. The crystal substrate may be an insulator substrate, a conductive substrate, or a semiconductor substrate. The crystal substrate may be a single crystal substrate or a polycrystalline substrate. A front surface of the crystal substrate may include a metal film. Note that, in a case where the crystal substrate is a conductive substrate, a vertical device may be fabricated without removing the substrate. The crystal structure of the crystal substrate is also not particularly limited unless it interferes with the present disclosure. Examples of the crystal structure of the crystal substrate include a hexagonal crystal structure and a tetragonal crystal structure. An example of a crystal substrate with a corundum structure is a sapphire substrate (e.g., an R-face sapphire substrate). Examples of a crystal substrate with a tetragonal crystal structure include a SrTiO3 substrate, a TiO2 substrate, and an MgF2 substrate. In an embodiment of the present disclosure, the crystal substrate preferably has a tetragonal crystal structure, and more preferably has a rutile-type structure. An example of a crystal substrate having a rutile-type structure is a rutile-type titanium dioxide (r-TiO2) substrate. An r-TiO2 substrate is preferably a conductive substrate containing a dopant such as Nb. Note that, the crystal substrate may have an off-angle. Additionally, in an embodiment of the present disclosure, a Ge substrate is preferably used as the crystal substrate.
The crystalline oxide film may be obtained by, for example, the following suitable film forming method. This manufacturing method of a crystalline oxide film (hereinafter also referred to as “oxide semiconductor” or “oxide crystal”) is also novel and useful and is incorporated as one aspect of the present disclosure.
In the manufacturing method of an oxide semiconductor according to the present disclosure, for example, a raw material solution containing germanium is atomized or formed into droplets (atomization step), a carrier gas is supplied to the obtained atomized droplets, the atomized droplets are carried onto a crystal substrate having a tetragonal crystal structure by the carrier gas (carrying step) and, simultaneously, the atomized droplets are caused to thermally react on the crystal substrate (film forming step).
The base is not particularly limited provided that the base supports the oxide semiconductor. The material of the base is also not particularly limited unless it interferes with the present disclosure, and a known base may be used. The base may be made of an organic compound or an inorganic compound. Additionally, the shape of the base is not particularly limited unless it interferes with the present disclosure. Examples of the shape of the base include a plate shape, such as a flat plate or a disc, a fibrous shape, a rod shape, a cylindrical shape, a polygonal shape, a tubular shape, a spiral shape, a spherical shape, and a ring shape. In the present disclosure, the base is preferably a substrate, more preferably a crystal substrate. The thickness of the substrate is not particularly limited. Additionally, the crystal substrate may be the same as the crystal substrate described above.
In the atomization step, the raw material solution is atomized. The atomization method is not limited as long as the raw material solution is atomized, and any known method may be used. In the present disclosure, an atomization method using ultrasonic waves is preferred. A mist obtained by using ultrasonic waves is desirable because the mist has an initial velocity of zero and is suspended in the air. The mist obtained by using ultrasonic waves is also very suitable because it is transported as a gas suspended in space rather than being sprayed, so there is no damage caused by collision energy, for example. The size of the mist droplets is not particularly limited and may be several millimeters, but is preferably less than 50 μm, and more preferably 100 nm to 10 μm.
The raw material solution may contain a dopant element and germanium, as long as the content of the germanium is greater than the content of the dopant element. The raw material solution may contain an inorganic material or an organic material. In an embodiment of the present disclosure, the raw material solution preferably contains germanium in the form of an organic germanium compound. Additionally, in an embodiment of the present disclosure, the organic germanium compound preferably has a carboxy group. The ratio of germanium (e.g., the organic germanium compound) in the raw material solution is not particularly limited, but 0.0001 mol/L to 20 mol/L is preferably used, and 0.001 mol/L to 1.0 mol/L is more preferably used, with respect to the entire raw material solution. Note that the raw material solution may contain another metal (e.g., tin or silicon) other than geranium.
The raw material solution may contain a dopant element. Examples of the dopant element include antimony (Sb), arsenic (As), bismuth (Bi), fluorine (F), aluminum (Al), gallium (Ga), or indium (In). In the embodiment of the present disclosure, the dopant element is preferably antimony (Sb). Note that, the dopant element may be contained in the raw material solution in the form of an inorganic compound or in the form of an organic compound.
The solvent of the raw material solution is not particularly limited and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solution of an inorganic solvent and an organic solvent. In the present disclosure, the solvent preferably contains water, and is also preferably a mixed solvent of water and an acid. More specifically, examples of the water include pure water, ultrapure water, tap water, well water, mineral spring water, mineral water, hot spring water, spring water, fresh water, and seawater. In the present disclosure, ultrapure water is preferably used. Further, examples of the acid include organic acids such as acetic acid, propionic acid, and butanoic acid, boron trifluoride, boron trifluoride etherate, boron trichloride, boron tribromide, trifluoroacetic acid, trifluoromethanesulfonic acid, and p-toluenesulfonic acid.
An additive such as a hydrohalogenated acid or an oxidizing agent may be mixed into the raw material solution. Examples of the hydrohalogenated acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid. Examples of the oxidizing agent include peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), benzoyl peroxide (C6H5CO)2O2, hypochlorous acid (HClO), and organic peroxides such as perchloric acid, nitric acid, ozone water, peracetic acid, and nitrobenzene.
In the carrying step, a carrier gas is supplied to the obtained atomized droplets (hereinafter also simply referred to as “mist”), and the mist is carried onto the base by the carrier gas. The type of carrier gas is not particularly limited unless it interferes with the present disclosure. For example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas may be used. In the present disclosure, oxygen is preferably used as the carrier gas. Air, oxygen gas, and ozone gas are examples of a carrier gas in which oxygen is used, and oxygen and/or ozone gas is especially preferably used. One type of carrier gas may be used, or two or more types of carrier gas may be used, and a diluted gas having a varied carrier gas concentration (e.g., gas diluted by 10 times) may be further used as a second carrier gas. The carrier gas may be supplied not only to one location but also to two or more locations. In the present disclosure, when an atomization chamber, a feed tube, and a film forming chamber are used, a supply location for the carrier gas is preferably provided in the atomization chamber and in the feed tube, respectively. More preferably, a supply location for the carrier gas is provided in the atomization chamber and a supply location for the diluted gas in provided in the feed tube. Further, the flow rate of the carrier gas is not particularly limited but is preferably 0.01 to 20 L/min, more preferably 1 to 10 L/min. In the case of diluted gas, the flow rate of the dilution gas is preferably 0.001 to 2 L/min, more preferably 0.1 to 1 L/min.
In the film forming step, the atomized droplets are caused to thermally react on the base to form a film on all or some of the surface of the base. The thermal reaction is not particularly limited as long as the thermal reaction forms a film from the mist. The reaction conditions are also not particularly limited unless it interferes with the present disclosure, and the mist need only be caused to react by heat. In this step, the thermal reaction is usually performed at a temperature equal to or greater than the temperature at which the solvent evaporates, and a moderate temperature is preferable. In the present disclosure, the thermal reaction is preferably performed at 700° C. to 800° C. Additionally, unless it interferes with the present disclosure, the thermal reaction may be performed in any atmosphere such as a vacuum, an oxygen-free atmosphere, a reducing gas atmosphere, or an oxidizing atmosphere, and may be performed under any conditions such as under atmospheric pressure, under pressure, or under decompression. In the present disclosure, the thermal reaction is preferably performed in an oxidizing atmosphere, and also preferably performed under atmospheric pressure, more preferably performed in an oxidizing atmosphere under atmospheric pressure. Note that, the term “oxidizing atmosphere” is not particularly limited and may be any atmosphere in which the oxide semiconductor may be formed by the thermal reaction. For example, the oxidizing atmosphere may be created by using a carrier gas containing oxygen or by using a mist consisting of a raw material solution containing an oxidizing agent. Additionally, the thickness of the film may be set by adjusting the film formation time.
In an embodiment of the present disclosure, the film may be formed directly on the base, or another layer such as a layer different to the oxide semiconductor (e.g., an n type semiconductor layer, an n+ type semiconductor layer, or an n− type semiconductor layer), an insulator layer (including a semi-insulator layer), or a barrier layer may be stacked on the base and the film may be formed on the base via the other layer. Particularly, the buffer layer may be suitably used to reduce the difference in lattice constants between the crystal substrate and the crystalline oxide film. Examples of the constituent material of the buffer layer include SnO2, TiO2, VO2, MnO2, RuO2, CsO2, IrO2, GeO2, CuO2, PbO2, AgO2, CrO2, SiO2, and their mixed crystals.
The crystalline oxide film obtained as described above is useful in a semiconductor device, particularly a power semiconductor device, and is suitably used as a semiconductor device including, for example, at least the crystalline oxide film and an electrode. Examples of the semiconductor device formed using the crystalline oxide film include a transistor or TFT such as an MIS or an HEMT, a Schottky barrier diode employing a semiconductor-metal junction, a JBS, a PN or PIN diode combined with another P-layer, and a light-emitting/receiving element. Note that, in the present disclosure, the crystalline oxide film may be suitably used in photoelectric conversion devices, gas sensors, photoelectrodes, and memories, in addition to those listed above. In an embodiment of the present disclosure, the crystalline oxide film may be used in a semiconductor device as the crystalline oxide film by removing the crystal substrate if desired, or may be used in a semiconductor device as a crystalline multilayer structure with the crystal substrate. Particularly, in a case where the crystalline substrate is a conductive substrate, the crystalline oxide film may be suitably applied to a semiconductor device (vertical device) as the crystalline multilayer structure.
The semiconductor device is suitable for both a horizontal-type device in which electrodes are formed on one surface of the semiconductor layer (horizontal device) and a vertical-type device including electrodes on both the front and back surfaces of the semiconductor layer (vertical device). In an embodiment of the present disclosure, the semiconductor device is particularly preferably a vertical device. Suitable examples of the semiconductor device include Schottky barrier diodes (SBDs), junction barrier Schottky diodes (JBSs), metal-semiconductor field-effect transistors (MESFETs), high-electron-mobility transistors (HEMTs), metal-oxide-semiconductor field-effect transistors (MOSFETs, electrostatic induction transistors (SITs), junction field-effect transistors (JFETs), insulated gate bipolar transistors (IGBTs), and light-emitting diodes (LEDs).
Suitable examples of the semiconductor device in which the crystalline oxide film of the present disclosure is applied to an n type semiconductor layer (n+ type semiconductor layer, n− type semiconductor layer, etc.) will be described below with reference to the drawings, but the present disclosure is not limited to these examples.
The material of the Schottky electrode and the ohmic electrode may be any known electrode material. Examples of the electrode material include a metal such as Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd or Ag or alloys of these, conductive films made of a metal oxide 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 or polypyrrole, and mixtures or laminates of these materials.
The Schottky electrode and the ohmic electrode may be formed by a known technique such as vacuum deposition or sputtering. More specifically, for example, in a case where the Schottky electrode is formed using two of the aforementioned metals as a first metal and a second metal, a layer made of the first metal and a layer made of the second metal are stacked, and patterning using a photolithography technique may be performed on the layer made of the first metal and the layer made of the second metal.
When a reverse bias is applied to the SBD in
The method of forming each layer of the semiconductor device in
An example in which the oxide semiconductor of the present disclosure is a MOSFET is illustrated in
On the drain electrode 135c, the n+ type semiconductor layer 131b having a thickness of from 100 nm to 100 μm for example, is formed, and on the n+ type semiconductor layer 131b, the n− type semiconductor layer 131a having a thickness of from 100 nm to 100 μm for example, is formed. Further, the n+ type semiconductor layer 131c is formed on the n− type semiconductor layer 131a, and the source electrode 135b is formed on the n+ type semiconductor layer 131c.
Within the n− type semiconductor layer 131a and the n+ type semiconductor layer 131c, a plurality of trench grooves are formed with a depth that penetrates the n+ type semiconductor layer 131c and reaches the middle of the n− type semiconductor layer 131a. The gate electrode 135a is formed embedded in the trench grooves via the gate insulating film 134 with a thickness of, for example, 10 nm to 1 μm.
In the on state of the MOSFET in
In the above-described example, a p type semiconductor is not used. However, in an embodiment of the present disclosure, no limitation is intended and a p type semiconductor may be used. Examples in which a p type semiconductor is used are illustrated in
An example of a case where the semiconductor device according to an embodiment of the present disclosure is a light-emitting diode (LED) is illustrated in
Examples of the material of the light-transmitting electrode include an electrically-conductive material made of an oxide such as indium (In) or titanium (Ti), and more specifically, In2O3, ZnO, SnO2, Ga2O3, TiO2, CeO2, a mixed crystal of two or more of these, and a material doped with any of these. The light-transmitting electrode may be formed by providing these materials by sputtering or other known means. After forming the light-transmitting electrode, thermal annealing may be performed to make the light-transmitting electrode transparent.
According to the semiconductor light-emitting element in
Examples of the material of the first electrode 165a and the second electrode 165b include a metal such as Al, Mo, Co, Zr, Sn, Nb, Fe, Cr, Ta, Ti, Au, Pt, V, Mn, Ni, Cu, Hf, W, Ir, Zn, In, Pd, Nd or Ag or their alloys, metal oxide conductive films such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO), and organic conductive compounds such as polyaniline, polythiophene, or polypyrrole, and mixtures thereof. The method of forming the electrodes is not particularly limited, and the electrodes may be formed on the base according to an appropriate method selected in consideration of suitability from among 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.
In order to exhibit the functions described above, the crystalline oxide film, the oxide semiconductor and/or the semiconductor device of the disclosure described above can be applied to a power converter such as an inverter or a converter. More specifically, it can be applied as a diode incorporated in the inverter or converter, a thyristor, a power transistor, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor or the like as a switching element.
As shown in
The motor 505 is a three-phase AC motor constituting the traveling system of an electric vehicle, and is driven by an AC voltage of the three-phase output from the inverter 504. The rotational driving force is transmitted to the wheels of the electric vehicle via a transmission mechanism (not shown).
On the other hand, actual values such as rotation speed and torque of the wheels, the amount of depression of the accelerator pedal (accelerator amount) are measured from an electric vehicle in cruising by using various sensors (not shown), The signals thus measured are input to the drive control unit 506. The output voltage value of the inverter 504 is also input to the drive control unit 506 at the same time. The drive control unit 506 has a function of a controller including an arithmetic unit such as a CPU (Central Processing Unit) and a data storage unit such as a memory, and generates a control signal using the inputted measurement signal and outputs the control signal as a feedback signal to the inverters 504, thereby controlling the switching operation by the switching elements. The AC voltage supplied to the motor 505 from the inverter 504 is thus corrected instantaneously, and the driving control of the electric vehicle can be executed accurately. Safety and comfortable operation of the electric vehicle is thereby realized. In addition, it is also possible to control the output voltage to the inverter 504 by providing a feedback signal from the drive control unit 506 to the boost converter 502.
As indicated by a dotted line in
As shown in
As shown in
The inverter 604 converts the DC voltage supplied from the AC/DC converter 602 into three-phase AC voltage by switching operations and outputs to the motor 605. Configuration of the motor 605 is variable depending on the control object. It can be a wheel if the control object is a train, can be a pump and various power source if the control objects a factory equipment, can be a three-phase AC motor for driving a compressor or the like if the control object is a home appliance. The motor 605 is driven to rotate by the three-phase AC voltage output from the inverter 604, and transmits the rotational driving force to the driving object (not shown).
There are many kinds of driving objects such as personal computer, LED lighting equipment, video equipment, audio equipment and the like capable of directly supplying a DC voltage output from the AC/DC inverter 602. In that case the inverter 604 becomes unnecessary in the control system 600, and a DC voltage from the AC/DC inverter 602 is supplied to the driving object directly as shown in
On the other hand, rotation speed and torque of the driving object, measured values such as the temperature and flow rate of the peripheral environment of the driving object, for example, is measured using various sensors (not shown), these measured signals are input to the drive control unit 606. At the same time, the output voltage value of the inverter 604 is also input to the drive control unit 606. Based on these measured signals, the drive control unit 606 provides a feedback signal to the inverter 604 thereby controls switching operations by the switching element of the inverter 604. The AC voltage supplied to the motor 605 from the inverter 604 is thus corrected instantaneously, and the operation control of the driving object can be executed accurately. Stable operation of the driving object is thereby realized. In addition, when the driving object can be driven by a DC voltage, as described above, feedback control of the AC/DC controller 602 is possible in place of feedback control of the inverter.
As indicated by a dotted line in
In such a control system 600, similarly to the control system 500 shown in
Although the motor 605 has been exemplified in
A mist CVD device used in the present example will be described with reference to
The susceptor 21 is made of quartz and the surface of the susceptor 21 on which the substrate 20 is placed is inclined relative to a horizontal plane. The supply tube 27 and the susceptor 21, which serve as the deposition chamber, are both fabricated from quartz to help prevent the introduction of equipment-derived impurities into the film to be formed on the substrate 20.
The raw material solution 24a was prepared by adding 10 volume percent of hydrochloric acid (HCl) to an aqueous solution of 0.001 M bis[2-carboxyethylgermanium(IV)] sesquioxide (C6H10Ge2O7).
The raw material solution 24a obtained in [2. Preparing Raw Material Solution] described above was placed in the mist generation source 24. Subsequently, a (001) surface r-TiO2 substrate serving as the crystal substrate 20 was placed on the susceptor 21 and the temperature of the heater 28 was raised to 750° C. Subsequently, the flow rate control valves 23a and 23b were opened to supply the carrier gas from the carrier gas supply means 22a and 22b, which are the carrier gas sources, into the supply tube 27. After the atmosphere in the supply tube 27 was sufficiently replaced with the carrier gas, the flow rate of the carrier gas and the carrier gas (diluted) were set to 3.0 L/min and 0.5 L/min, respectively. Note that, oxygen was used as the carrier gas.
Subsequently, the ultrasonic transducer 26 was oscillated at 2.4 MHz, and this oscillation was transmitted to the raw material solution 24a via the water 25a to atomize the raw material solution 24a and create a mist (atomized droplets) 24b. The mist 24b was passed through the supply tube 27 by the carrier gas and introduced into the film forming chamber 30, where the mist was made to thermally react on the substrate 20 at 725° C. under atmospheric pressure to form a GeO2 film on the substrate 20. The film thickness of the obtained GeO2 film was 200 nm.
The GeO2 film of the crystalline multilayer structure obtained in [4. Film Formation] described above was identified using an X-ray diffractometer, and the resulting film was a (001) plane-oriented r-GeO2 film with a rutile-type structure. The results of the XRD are shown in
A GeO2 film was formed in the same manner as in Example 1, except that the concentration of bis [2-carboxyethylgermanium(IV)] sesquioxide (C6H10Ge2O7) in the raw material solution was changed to 0.025 M (mol/L) and the film formation temperature was changed to 750° C. The obtained GeO2 film was identified using an X-ray diffractometer, and it was found that the resulting film was a (001) plane-oriented r-GeO2 film with a rutile-type structure. The results of observation of the obtained film surface using an SEM are shown in
The crystalline oxide film according to the present disclosure may be used in all fields, including semiconductors (e.g., compound semiconductor electronic devices, etc.), electronic and electrical components, optical and electrophotographic devices, and industrial components, but are particularly useful in semiconductor devices and components thereof.
The embodiments of the present invention are exemplified in all respects, and the scope of the present invention includes all modifications within the meaning and scope equivalent to the scope of claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-126327 | Jul 2021 | JP | national |
This application is a continuation-in-part application of International Patent Application No. PCT/JP2022/028852 (Filed on Jul. 26, 2022), which claims the benefit of priority from Japanese Patent Application No. 2021-126327 (filed on Jul. 30, 2021). The entire contents of the above applications, which the present application is based on, are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/028852 | Jul 2022 | US |
| Child | 18425922 | US |
