JP5528612B1 - Semiconductor device - Google Patents

Abstract

In a semiconductor device or substrate using a semiconductor crystal containing indium, aluminum, and gallium, a loss other than a channel layer is reduced, and a semiconductor layer is formed on a base material that is inexpensive and can have a large diameter. It is intended to be used as a base material for nitride semiconductors and to be combined with Si semiconductor devices.
According to the present invention, at least one of indium, aluminum, and gallium formed on a uniaxially oriented platinum, gold, or palladium thin film or substrate, or a crystalline oxidation that is a combination thereof. A semiconductor device or substrate including a physical thin film is provided.
[Selection] Figure 1

Description

  The present invention relates to a power or light emitting / receiving semiconductor device.

A semiconductor device using gallium oxide (Ga ₂ O ₃ ) having a large band gap has been attracting attention as a next-generation switching element that can achieve high breakdown voltage, low loss, and high heat resistance. Application is expected. Moreover, application as a light emitting / receiving device such as an LED or a sensor is also expected from a wide band gap. According to Non-Patent Document 1, the gallium oxide can control the band gap by mixing crystals of indium and aluminum, respectively, or in combination, and constitutes an extremely attractive material system as an InAlGaO-based semiconductor. . Here, the InAlGaO-based semiconductor means In _X Al _Y Ga Ga _Z O ₃ (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, 0 ≦ Z ≦ 2, X + Y + Z = 1.5 to 2.5). It can be overlooked as the same material system to be included.

As a base material used for realizing a semiconductor device using these InAlGaO-based semiconductors, a β-gallium oxide substrate and a sapphire substrate have been studied.
According to Patent Document 1, when a β gallium substrate is used, gallium oxide can be homoepitaxially grown, and the quality of the aluminum gallium oxide thin film can be improved. However, the substrate size that can be procured is limited, and it has been difficult to increase the diameter compared to materials that are already mass-produced, such as silicon and sapphire.
According to Patent Document 2 and Patent Document 3, when a sapphire substrate is used, it is possible to improve the quality of an Al _x Ga _Y O ₃ (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, X + Y = 2) thin film having a corundum structure. However, it is difficult to improve the quality of the β-gallia structure film. In addition, since sapphire is an insulator, there is a problem that current cannot flow through the base material. In this case, either the source or drain electrode cannot be formed on the base material, and the output current per unit area of the semiconductor device is limited. When the diameter was increased to 6 inches or 8 inches, industrial applications of these large diameter sapphires were not so advanced, and there was a problem of stable procurement and an increase in procurement costs.

In addition, the low thermal conductivity of gallium oxide and sapphire is also a problem in increasing the heat resistance of semiconductor devices.
Furthermore, the characteristics of the base material also cause problems in electrical characteristics for realizing a low-loss semiconductor device. For example, in order to realize a semiconductor device having a high breakdown voltage and a low loss, it is necessary to reduce the loss other than the channel layer in addition to the reduction of the loss in the channel layer. For example, the contact region constituting the semiconductor device is required to have a low loss, and the vertical semiconductor device is also required to reduce the loss of the base material and the layer between the base material and the channel layer.

  In addition, with the development of mobile devices, etc., there is a demand for downsizing of semiconductor devices against the background of improving the processing capacity per unit volume of information processing terminals. The number of semiconductor devices by combining semiconductor devices having different functions There are also market demands to reduce Here, there is a strong demand for compounding with a semiconductor device or substrate using Si, for which industrial applications are overwhelmingly advanced. Even when using a gallium oxide or sapphire substrate for which crystal growth technology has been demonstrated so far, it has been difficult to realize the composite because it is necessary to replace the base material and the like.

  By the way, as an important application field of InAlGaO-based semiconductors, the application of underlying materials for nitride semiconductors such as GaN, AlN, InN, AlGaN, InGaN, and InAlGaN is also important. Nitride semiconductors are industrially applied in the field of receiving and emitting light such as LEDs and lasers. However, when the most common sapphire substrate is used as a base material, the voltage drop, heat loss, and current distribution are not good due to the n layer, which is a conductive layer. In addition to problems such as uniformity, the limit of the current density due to the fact that bipolar electrodes must be formed on the same InAlGaN semiconductor due to the insulating sapphire substrate. There is also a problem that it is difficult to combine the LED element and the Si semiconductor device. Nitride semiconductor film formation technology on the Si {111} surface has attracted attention due to a device such as a buffer layer, but the nitride semiconductor film formation technology on the Si {100} surface, which has been mass-produced, has progressed. Industrial applications are still difficult.

  According to Patent Document 3, a gallium nitride crystal can be grown using a β-gallium oxide substrate as a base material, but the substrate size that can be procured is limited, and materials that have already been mass-produced such as silicon and sapphire It was difficult to increase the diameter compared to the above.

  According to Non-Patent Document 2, Tomas Palacios et al. Of MIT peels an AlGaN / GaN film grown on Si {111} from a Si {111} substrate, and attaches an AlGaN / GaN thin film to the Si {100} substrate. Integration of devices and GaN devices is planned. However, there is a problem that the number of work steps is large and it is difficult to cleanly peel off the entire surface of the substrate.

International Publication Number WO2013 / 035842 International publication number WO2013 / 035844 JP2013-58636A

Kentaro Kaneko, “Growth and Physical Properties of Corundum Structure Gallium Oxide Mixed Crystal Thin Films”, Kyoto University Doctoral Dissertation, March 2013 IEEE EDL, 30, 1015, 2009

The present invention has been made in view of the above circumstances,
The first purpose of the application for InAlGaO-based semiconductors is to reduce loss other than the channel layer in a semiconductor device or substrate using a semiconductor crystal containing at least indium, aluminum, and gallium, and to be inexpensive and large. Forming a semiconductor layer on a base material that can be calibrated, forming a semiconductor layer on a base material having better thermal conductivity than a β-gallium oxide substrate or a sapphire substrate, and realizing a composite with a Si semiconductor device There is.
The second purpose is to use an InAlGaO-based semiconductor as a base material as an application field for nitride semiconductors, to reduce loss other than the light receiving and emitting layers and reduce wasteful heat generation. It is to form a semiconductor layer on a base material that can be formed and to realize a composite with a Si semiconductor device.

  According to the present invention, a uniaxially oriented platinum, gold, or palladium thin film or a crystalline oxide thin film formed by combining at least one of indium, aluminum, and gallium, or a combination thereof is included. A semiconductor device or substrate is provided.

  As a method for solving the above problems, the inventors of the present invention formed an oxide thin film on at least one of indium, aluminum, gallium, or a combination thereof on various metals and metal oxides. The present inventors have found that the crystalline oxide thin film can be formed on a platinum or gold thin film or substrate oriented in the above manner. The crystalline oxide thin film is not formed on any metal or metal oxide. Conventionally, those skilled in the art have never assumed that a uniaxially oriented platinum or gold thin film or substrate is used as a base for the oxide thin film. Trials have shown that the crystalline oxide thin film can be formed on a platinum or gold thin film or substrate. Therefore, when the oxide thin film was formed on a platinum or gold thin film or substrate formed by several methods, (1) either the platinum or gold thin film or substrate was uniaxially oriented before the start of film formation. Or (2) when the platinum or gold thin film or substrate is not uniaxially oriented before the start of film formation, but is exposed to a high temperature during the film formation, so that the platinum or gold thin film or substrate is uniaxially oriented. It was found that a crystalline oxide thin film can be formed only in

  The inventors of the present invention formed the oxide thin film using a platinum or gold vapor-deposited material on a silicon substrate as a base, but in this case, the platinum or gold was not oriented uniaxially even after the film formation. The obtained oxide thin film was amorphous. On the other hand, platinum or gold was deposited on a sapphire substrate and the oxide thin film was formed. The platinum or gold thin film was uniaxially oriented after the film formation, and the obtained oxide thin film was crystalline. .

Further, an oriented platinum thin film was formed by forming a silicon oxide film on a silicon substrate and forming the film while performing high-temperature annealing using titanium and platinum and a sputtering method. When the oxide thin film was formed thereon, it was found that the oxide thin film became crystalline.
Platinum and gold are noble metals, and it is known that surface oxide films hardly occur. The surface of platinum or gold does not change during the crystal growth process of the metal oxide film formed on the upper layer, and platinum or gold It is considered important to be able to maintain the plane orientation. Furthermore, it can be inferred that the fact that the lattice constant of the metal oxide film is relatively close to the lattice constant of platinum or gold was also an important factor that brought this result.
Palladium exists as a similar metal, and almost no surface oxide film is formed, and since the lattice constant is close to that of platinum or gold, it can be reasonably analogized that the same effect as that of platinum or gold is brought about. Since platinum, palladium, and gold are less likely to have high resistance due to oxide film formation, loss reduction can be realized by utilizing the structure of the present invention as a contact region or an electrically conductive layer.

The present invention can also be implemented in the following forms.
Preferably, a platinum or gold, palladium thin film or substrate is oriented in the {111} plane.
Preferably, a Si {100} substrate that is used in a large amount as the base material is any one of a Si substrate, a sapphire substrate, and a glass substrate, is inexpensive, and has high versatility.
Preferably, a layer that is not uniaxially oriented is formed between the base material and platinum, gold, or palladium. Thereby, platinum, gold | metal | money, and palladium become easy to orient. Examples of the layer that is not uniaxially oriented include metal oxides and nitrides. For example, silicon oxide, zinc oxide, tin _{oxide, InGaZnO, ITO, In X Al} Y Ga Z O 3 (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5~2. 5) Any one of 5) or a combination of these in the same layer or in layers. The layer that is not uniaxially oriented includes an amorphous layer. By forming the conductive oxide as a layer that is not uniaxially oriented, the electrical conductivity between the base substrate and platinum, gold, or palladium can be kept good. By using an insulating film such as silicon oxide as a layer that is not uniaxially oriented, the insulating property between the base material and platinum, gold, or palladium can be kept good.
Preferably, a layer in which one or more metals such as titanium and nickel are combined is formed between the base material and platinum, gold, or palladium. Alternatively, a layer containing one or a combination of conductive oxides is interposed. As a result, the base material and platinum or gold can be connected to each other with low resistance, or ohmic characteristics can be imparted.

Preferably, the crystalline oxide has a corundum structure, a β-gallia structure, and a bixbite structure.
Preferably, the crystalline oxide _{is In X Al Y Ga Z O 3} (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5~2.5). Specifically, X, Y, and Z are, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0, respectively. .1, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 and the numerical values exemplified here It may be within the range between any two. Specifically, X + Y or X + Y + Z is, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2 .5, and may be within a range between any two of the numerical values exemplified here.

Preferably, the crystalline oxide is the α-type _{In X Al Y Ga Z O 3} (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5~2.5) However, at least one of indium, aluminum, and gallium, or a combination thereof, and a semiconductor device or crystal in which an element other than indium, aluminum, or gallium is mixed or mixed with impurities may be used as the structure.

  Preferably, a semiconductor device or a substrate including a crystalline oxide thin film containing at least one of indium, aluminum, and gallium, or a combination thereof, but used as an amorphous oxide or a polycrystalline oxide. You can also. In the prior art, since it was difficult to form the oxide thin film on various deposition materials, the invention is expected to be applied to various application fields.

Preferably, it is a semiconductor device in which a nitride semiconductor in which any one of indium, aluminum, gallium, or a combination thereof is formed directly on the oxide thin film or through another layer. In this case, the base substrate is not particularly limited, but a metal substrate such as a Si {100} substrate, a sapphire substrate, a silicon oxide substrate, or copper is preferable. Examples of the silicon oxide substrate include quartz, glass, quartz glass, and crystallized glass. Preferably nitride semiconductor _{In X Al Y Ga Z N (} 0 ≦ X ≦ 1.1,0 ≦ Y ≦ 1.1,0 ≦ Z ≦ 1.1, X + Y + Z = 0.9~1.1) in the semiconductor is there. Specifically, X, Y, and Z are, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0, respectively. .9, 1.0, 1.1, and may be within a range between any two of the numerical values exemplified here. At least one of indium, aluminum, and gallium, or a combination thereof, and a semiconductor device or crystal in which an element other than indium, aluminum, or gallium, for example, boron or the like is mixed or impurities mixed may be used as the structure.

The present invention can be further developed and applied to the formation of various semiconductor layers on a platinum, gold or palladium thin film. In this case, various semiconductors such as a Si semiconductor, a nitride semiconductor, and a group III-IV semiconductor can be used as the semiconductor layer in addition to an oxide thin film of at least indium, aluminum, gallium, or a combination thereof. Although it does not specifically limit as base material, If Si {100} board | substrate is used, it will be easy to compound with various semiconductor devices or a board | substrate. Conventionally, there has been a case where a semiconductor device is compounded by using a semiconductor device re-covering technique, but according to the present invention, a thin film of platinum, gold, or palladium is formed on a semiconductor device such as a Si semiconductor device. A semiconductor device is formed by forming semiconductor layers having different functions, and the semiconductor devices are combined. As a method for forming a semiconductor layer on a platinum, gold or palladium thin film, a CVD reaction or a sputtering method is preferably used, and the growth is influenced by the plane orientation of the platinum, gold or palladium thin film formed in the lower layer. It is preferable to cause. The platinum, gold or palladium thin film is preferably formed by uniaxially orienting the platinum, gold or palladium thin film itself by forming an appropriate intermediate layer directly below the thin film. Those that are not oriented and that produce an effect of reducing the influence of the plane orientation of the underlying material located under the intermediate layer are preferred.
Note that the description of Si {100} in the present invention includes all surfaces having equivalent symmetry planes such as (100), (010), and (001) having the same plane orientation.

It is sectional drawing of the semiconductor device which shows the example of embodiment of this invention, and a board | substrate. It is sectional drawing of the semiconductor device which shows the other example of embodiment of this invention, and a board | substrate. It is sectional drawing of the semiconductor device which shows the other example of embodiment of this invention, and a board | substrate. It is sectional drawing of the semiconductor device which shows the other example of embodiment of this invention, and a board | substrate. It is sectional drawing of the semiconductor device which shows the other example of embodiment of this invention, and a board | substrate. It is a block diagram of the film-forming apparatus which shows the example of embodiment of this invention. It is a block diagram of the film-forming apparatus which shows the example of embodiment of this invention. It is a figure which shows an example of the X-ray-diffraction profile of the Example of this invention. It is a figure which shows an example of the X-ray-diffraction profile of the Example of this invention. It is a figure which shows an example of the X-ray-diffraction profile of the Example of this invention. It is a figure which shows an example of the X-ray-diffraction profile of the Example of this invention.

  Hereinafter, with reference to the attached drawings, a form relating to the formation of a platinum, gold or palladium thin film or substrate and a form relating to the formation of an oxide thin film will be described. A description will be given using a mist CVD method, which is one of the preferred embodiments. In addition, the component which attached | subjected the same code | symbol in each figure shall be the same.

1. Formation of platinum, gold or palladium thin film or substrate When using a platinum, gold or palladium substrate, a commercially available material may be purchased. Those having a thickness of 100 μm or more that are easy to handle without being damaged in steps such as film formation and device process are desirable, and the film formation surface is desirably processed flat by a method such as chemical polishing. For platinum and gold thin films, various film forming techniques such as sputtering, vapor deposition and plating can be used. In order to manufacture a sample with a surface orientation of {111}, heat treatment may be performed during film formation, or heat treatment may be performed after film formation. At least one of indium, aluminum, and gallium, or a combination thereof, may be used to align platinum, gold, or palladium by thermal energy when forming a crystalline oxide thin film.

  Before the platinum, gold, or palladium thin film is formed, a layer of silicon oxide, titanium, nickel, or the like can be provided as a block layer or an adhesion enhancement layer between the film-forming material. The block layer is introduced for the purpose of preventing the base material of each layer from diffusing and mixing into the upper layer by a process such as heat treatment. There is also an effect of improving the frequency characteristics of the semiconductor device formed in a layer above the block layer. By using low resistance metal oxide films such as metals such as titanium and nickel, zinc oxide, tin oxide, ITO, InGaZnO, InO, GaO, and InAlGaO for the block layer and adhesion enhancement layer, platinum, gold, or palladium and a base material Can be connected to a low resistance, or ohmic characteristics can be imparted to the connection. At this time, the metal oxide film does not necessarily have to be uniaxially oriented, and may be amorphous or polycrystalline. In order to improve the adhesion strength, the material is selected on the basis of the compatibility with the base material of each layer in addition to the material characteristics, and titanium or nickel is preferably used. Some layers, such as titanium, can also serve as a block layer and an adhesion enhancement layer.

As an example of a preferred embodiment, there is a method of forming a thin film of platinum, gold or palladium on c-plane sapphire by vapor deposition or sputtering. The thickness of the thin film is not particularly limited, but is preferably 500 nm or less, more preferably 50 nm or less.
As an example of a preferred embodiment, there is a method in which a silicon oxide film is formed on a Si {100} surface by thermal oxidation, and then a platinum, gold, or palladium film is formed by sputtering while applying heat treatment. By performing the heat treatment after the film formation, the crystallinity of platinum, gold, or palladium can be further improved.

2. Oxide thin film deposition <Raw material>
The raw material for the crystalline oxide is not particularly limited, and any of a gallium compound, an indium compound, and an aluminum compound, or a metal compound in combination of these can be used as a material. A gallium compound or an indium compound may be formed immediately before film formation using gallium metal or indium metal as a starting material. There are many types of gallium compounds and indium compounds, including organic complexes and halides. In this embodiment, gallium acetylacetonate and indium acetylacetonate are used as the gallium compound and indium compound. As the aluminum compound, aluminum acetylacetonate is used.

  The solvent of the raw material solution is preferably water, hydrogen peroxide solution, or an organic solvent. In the raw material solution, a dopant compound can be added, whereby conductivity can be imparted to the thin film to be formed, so that it can be used as a semiconductor layer.

From _{In X Al Y Ga Z O 3} (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1.5~2.5) in X, Y, at least two 0 of Z In the case of forming a thin film (mixed crystal film) containing two or more kinds of metal elements as in the case of large, two or more kinds of metal compounds may be dissolved in one kind of raw material solution. A raw material solution may be prepared, and each raw material solution may be finely divided separately.

It should be noted that the notation “In _X Al _Y Ga _Z O ₃ ” in this specification is used only to express the ratio of metal ions to oxygen ions, and is not clear from the notation “X + Y + Z = 2”. Thus, non-stoichiometric oxides are included, which include not only metal-deficient oxides and metal-excess oxides, but also oxygen-deficient oxides and oxygen-excess oxides.

<Mineralization>
The method for producing the raw material fine particles by making the raw material solution into fine particles is not particularly limited, but a general method is to apply ultrasonic vibration to the raw material solution to form fine particles. Also, in other methods, for example, the raw material fine particles can be generated by atomizing the raw material solution by spraying the raw material solution.

<Carrier gas>
The carrier gas is, for example, nitrogen, but a gas such as argon, oxygen, ozone, or air may be used. Moreover, the flow volume of carrier gas is although it does not specifically limit, For example, it is 0.1-50 L / min. When an organic solvent is used for the raw material solution, it is preferable to use a gas such as oxygen containing oxygen element or ozone.

<Deposition chamber / deposition sample / deposition>
The raw material fine particles are supplied to the film formation chamber by the carrier gas, and a reaction occurs in the film formation chamber, so that a thin film is formed on the film formation sample placed in the film formation chamber. The thin film formed on the deposition target sample is an oxide crystal (preferably oxide single crystal) thin film.

  The film formation chamber is a space in which a thin film is formed, and its configuration and material are not particularly limited. In one example, the film forming chamber is configured to supply a carrier gas containing raw material fine particles from one end of a quartz tube and to discharge exhaust gas from the other end of the quartz tube as in the embodiment. In the case of this configuration, the film formation sample may be arranged so that the film formation surface is horizontal, or may be arranged so as to be inclined at, for example, 45 degrees toward the carrier gas supply side. In addition, a fine channel method using a channel of several mm or less as a reaction region, or a linear nozzle is provided on the substrate, from which raw material fine particles (and carrier gas) are sprayed in a direction perpendicular to the substrate, and the nozzle is linear A linear source method of moving in the vertical direction with respect to the outlet of the film, or a film forming method by a method in which a plurality of methods are mixed or derived may be used. With the fine channel method, it is possible to produce a homogeneous thin film and improve the utilization efficiency of raw materials, and with the linear source method, it is possible to continuously form a film on the future large-area substrate and roll-to-roll. The film forming chamber is configured such that the inner space can be heated to a desired temperature by, for example, surrounding the film forming chamber with a heater. Further, the film formation chamber may be pressurized or depressurized instead of atmospheric pressure.

  The heating temperature of the film formation chamber at the time of film formation is not particularly limited as long as it is a temperature at which a raw material solute (gallium compound, indium compound, etc.) contained in the raw material solution can be chemically reacted, and is, for example, 300 to 1500 ° C. 400 to 700 ° C is preferable, and 450 to 550 ° C is more preferable. If the heating temperature is too low, the reaction rate of the raw material solute will be slow and the film forming rate will be slow, and if the heating temperature is too high, the etching rate of the formed thin film will become large and the film forming rate will be slow. It is. Specifically, the heating temperature is, for example, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 900, 1000, 1500 ° C., and any of the numerical values exemplified here is 2 It may be within a range between the two. However, when the oxide thin film has a corundum structure (α layer), the β phase tends to grow when the film formation temperature is high. It is necessary to optimize conditions such as composition and flow rate during film formation. Each oxide thin film may be a single composition film or a mixed crystal film. In the case of a mixed crystal film, mist may be generated from the solution 13a in which two or more types of solutes are mixed, or two or more types of mist generated separately may be introduced into the film forming chamber 16 at the same time.

  The sample to be deposited is not particularly limited as long as a thin film or substrate of platinum, gold or palladium, preferably a thin film or substrate oriented in a plane direction, for example, oriented in {111} can be formed. As a suitable example when forming a thin film of platinum, gold, or palladium, any of a Si substrate, a glass substrate, and a sapphire substrate may be used as a base material. As the Si substrate, {100} is particularly preferable, but a {111} substrate may be used. Examples of other suitable underlayer materials for the film formation target include a thin film or substrate having a corundum structure, a thin film or substrate having a hexagonal crystal structure typified by GaN and ZnO, and a cubic crystal typified by YSZ. And a β-type gallium oxide thin film or substrate, a γ-type gallium oxide thin film or substrate, and the like. An amorphous oxide is preferably formed between the platinum, gold or palladium thin film and the underlying material. If the amorphous oxide is a conductive oxide, an electrode can be formed over the base material, and the area of the semiconductor device can be reduced in some cases.

  It is also possible to put a buffer layer between the platinum, gold or palladium thin film or substrate and the oxide thin film containing at least indium, aluminum and gallium. The buffer layer may be an oxide containing at least indium, aluminum, and gallium and having a composition different from that of the oxide thin film. The buffer layer is formed between a platinum, gold or palladium thin film and an oxide thin film. For example, an oxide thin film can be formed while being formed at a low film formation temperature and maintaining a good surface state of platinum, gold, or palladium. In another example, a low work function metal such as titanium or zinc oxide or indium oxide formed between platinum, gold or palladium and an upper oxide thin film to reduce contact resistance with platinum or gold. A thin film of metal oxide such as ITO, InGaZnO may be used. It may have a corundum structure, a β-gallia structure, a bixbite structure, and preferably has the same crystal structure as the oxide thin film layer.

Examples of semiconductor devices or crystals that can be manufactured by the method of this embodiment are shown in FIGS.
In the example of FIG. 1, In _X Al _Y Ga _Z O ₃ (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, 0 ≦ Z ≦ 2, X + Y + Z = 1.5 to 2 on a platinum, gold or palladium substrate 2. .5) The film 1 is formed in this order.
In the example of FIG. 2, a thin film 4 of platinum, gold or palladium is formed on the base material 5, and In _X Al _Y Ga _Z O ₃ (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, 0 ≦ Z ≦ 2, X + Y + Z = 1.5 to 2.5) The film 3 is formed in this order. The platinum, gold or palladium thin film 4 is preferably oriented, and particularly preferably oriented in the {111} plane. The base material 5 is preferably a Si substrate, a sapphire substrate, or a glass substrate, and may be a metal substrate such as Cu.

In the example of FIG. 3, a block layer 8 is formed between a platinum, gold or palladium thin film 7 and a base material 9. The block layer 8 is formed for the purpose of preventing the base material 9 from appearing on the platinum, gold or palladium thin film 7, and titanium or silicon oxide is preferable. Thereby, In _X Al _Y Ga _Z O ₃ (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, 0 ≦ Z ≦ 2, X + Y + Z = 1.5 to 2.5) film 6 which prevents impurities derived from the base material. Can be formed.
In the example of FIG. 4, an adhesion enhancement layer 12 is formed between the platinum, gold or palladium thin film 11 and the base material 13. The adhesion enhancement layer 12 is formed for the purpose of enhancing the adhesion between the base material 13 and the platinum, gold, or palladium thin film 11, and titanium or nickel is preferable.
In the example of FIG. 5, the block layer 16 and the adhesion enhancement layer 17 are formed between the platinum, gold or palladium thin film 15 and the base material 18.

The block layer 16 and the adhesion enhancement layer 17 may be formed in a structure that is turned upside down. When the adhesion enhancing layer 17 is formed on the block layer 16, it is preferable that the adhesion enhancing layer 17 does not react with the platinum, gold or palladium thin film 15 in the film forming process or the post-film forming process. When this reaction occurs, the adhesion enhancement layer is mixed with a thin film of platinum, gold, or palladium, and a good quality In _X Al _Y Ga _Z O ₃ (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, 0 ≦ Z ≦ 2, X + Y + Z = 1.5 to 2.5) This is because it prevents the film from being formed. In addition, the adhesion between the block layer 16 and the base material 18 is preferably strong.
In the example of FIG. 6, a buffer layer is formed between the oxide thin film 19 and the platinum, gold or palladium thin film 21.

<Removal>
When film formation of the oxide thin film is completed, the base material with the oxide thin film is taken out from the film formation chamber.
When the oxide thin film is used as a base material for a nitride semiconductor such as GaN, AlN, InN, AlGaN, InGaN, or InAlGaN semiconductor, the nitride semiconductor is formed by a film formation process such as MOCVD. By performing nitriding treatment before forming the nitride semiconductor to nitride the outermost surface of the oxide thin film, the crystal quality of the nitride semiconductor such as InAlGaN can be improved. For the nitriding treatment, nitrogen plasma treatment or a method of annealing at a high temperature while flowing ammonia gas can be used.

  In particular, when forming an oxide thin film having a corundum structure, it can be grown at a low temperature, and even when it is combined with Si {100} or the like, the film forming temperature can be kept low. Thermal damage to materials, thin films, and semiconductor devices formed on the same substrate other than the above can be reduced. However, if thermal energy is required when forming the nitride semiconductor layer, a method for preventing phase transition may be introduced in order to maintain the corundum structure. For example, a technique such as introduction of a low-temperature buffer layer of a nitride semiconductor can be mentioned.

An example of a technique for preventing or controlling phase transition is introduced below.
For example, by forming an oxide thin film having a higher Al concentration as a layer on the oxide thin film, a phase transition of a corundum structure oxide thin film, preferably an InAlGaO-based semiconductor, can be prevented or controlled.
For example, the film forming temperature of the nitride semiconductor layer is suppressed to a low temperature at which the corundum structure oxide thin film, which is the base material, does not undergo phase transition. In particular, in the case of a gallium oxide semiconductor, it is preferable to suppress it to 500 ° C. or lower.

  For example, a low-temperature buffer layer of a nitride semiconductor is inserted between a nitride semiconductor layer such as an InAlGaN semiconductor and an InAlGaO semiconductor layer, and the film formation temperature at the time of interface formation is suppressed to a temperature at which the corundum structure oxide thin film does not undergo phase transition. Thus, the interface between the oxide thin film such as an InAlGaO-based semiconductor and the nitride semiconductor such as InAlGaN can be maintained well. In this case, the formation temperature of the nitride semiconductor layer after forming the low-temperature buffer layer is not necessarily limited to a temperature lower than the phase transition of the corundum structure oxide thin film.

  Moreover, in the said embodiment, although the oxide thin film was formed into a film by mist CVD method, you may form into a film by another method. By using the mist CVD method, an oxide thin film can be formed at a relatively low temperature. As a result, there is an advantage that platinum or gold migration hardly occurs, and that a difference in coefficient of thermal expansion depending on the material type hardly becomes a problem. Other methods capable of forming an oxide thin film include metal organic chemical vapor deposition, molecular beam epitaxy, sputtering, vapor deposition, and the like, which are appropriately performed in combination with heat treatment after film formation. The heat treatment after film formation can be replaced by heat treatment in a process that is not directly aimed at film formation of an oxide thin film, crystallinity improvement, and the like, which are placed in a subsequent manufacturing process.

  In the present invention, the oxide thin film, the buffer layer, the block layer, and the nitride semiconductor layer may be doped with an element other than indium, aluminum, and gallium or may be a mixed crystal. For example, elements such as Ge, Sn, Si, Zn, and Mg may be used for impurity doping, and mixed crystals such as InGaZnO may be used for the block layer and the oxide thin film layer. Thereby, electroconductivity and insulation can be adjusted.

  Furthermore, in the present invention, a certain repetitive structure regarding the film composition and element doping concentration may be introduced into a part of the oxide thin film, buffer layer, block layer, platinum, gold or palladium. As a result, it is possible to promote stress relaxation, or to adjust the carrier concentration increase / decrease, the carrier mobility level, the degree of adhesion, and the degree of prevention of mixing of other layers (blocking degree).

Thus, the film forming process of the semiconductor device according to the present invention is completed, and the process proceeds to device processes such as ion implantation, etching, photolithography, heat treatment, and electrode formation.
Thereafter, the platinum or gold thin film can also be used in a base material peeling technique. For example, platinum or gold can be dissolved with a chemical solution or the like, and the layer above platinum or gold fixed to the support substrate in advance can be peeled off. In this case, the chemical solution must be appropriately selected so that the target layer to be immobilized on the indicator substrate after peeling off platinum or gold from the upper layer is not dissolved by the chemical solution in which platinum or gold is dissolved.

Examples of the present invention will be described below.
1. Experiment 1
1-1. Film formation sample preparation What formed the platinum thin film into a film using the vapor deposition apparatus on the sapphire substrate (Namiki precision jewelry Co., Ltd. make, C surface, 0.55mm thickness) was made into the film formation sample.
In another example, titanium is deposited at a thickness of 10 nm at 600 ° C. on a Si {100) substrate (thermal oxide film 100 nm, N-type, 0.525 mm thickness) using a sputtering apparatus (EB 1100 manufactured by Canon Anelva) Then, using a sputtering apparatus (same as above), the film formation sample temperature during film formation was 600 ° C., and a platinum thin film having a film thickness of 35 nm was formed as a film formation sample.
Further, a gold thin film having a thickness of 35 nm was formed using a vapor deposition apparatus using the above-described sapphire substrate or Si {100} substrate as a film formation sample.

1-2. Mist CVD apparatus First, the mist CVD apparatus 25 used in the present embodiment will be described with reference to FIG. As the film formation sample 26, the film formation sample prepared by the method described in 1-1 above was used. The mist CVD apparatus 25 adjusts the flow rate of the carrier gas sent from the sample stage 27 on which the film-forming sample 26 such as the base material is placed, the carrier gas source 28 for supplying the carrier gas, and the carrier gas source 28. A flow rate adjusting valve 29, a mist generating source 24 in which a raw material solution 30a is stored, a container 31 in which water 31a is placed, an ultrasonic transducer 32 attached to the bottom surface of the container 31, and a quartz tube having an inner diameter of 40 mm. A film forming chamber 33, and a heater 34 installed in the periphery of the film forming chamber. The sample table 27 is made of quartz, and the surface on which the film formation sample 26 is placed is inclined. Both the film formation chamber 33 and the sample stage 27 are made of quartz, so that impurities derived from the apparatus are prevented from being mixed into the thin film formed on the film formation target sample 26.

1-3. Preparation of Raw Material Solution A raw material solution 30a having a desired concentration was prepared by dissolving the raw material solutes shown in Table 1 in ultrapure water.

1-4. Preparation of film formation Next, as a film formation sample 26, a base material having a square of 10 mm on one side and a thickness of 600 μm was placed on the sample stage 27, and the heater 34 was operated to bring the inside of the film formation chamber 33 to 500 ° C. The temperature was raised. Next, the flow rate adjusting valve 29 is opened to supply the carrier gas from the carrier gas source 29 into the film forming chamber 33, and the atmosphere in the film forming chamber 33 is sufficiently replaced with the carrier gas. Adjusted to minutes. Nitrogen gas was used as the carrier gas.

1-5. Thin Film Formation Next, the ultrasonic vibrator was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 30a through the water 31a, whereby the raw material solution 30a was made into fine particles to produce raw material fine particles.
The raw material fine particles are introduced into the film formation chamber 33 by the carrier gas, react in the film formation chamber 33, and form a thin film on the film formation sample 26 by the CVD reaction on the film formation surface of the film formation sample 26. Formed.

1-6. Evaluation The X-ray diffraction results for the experiment of Table 1 are shown in FIGS. In FIG. 8, which is a sample formed on the sapphire substrate, it was confirmed that platinum was oriented in the {111} plane in FIG. And it confirmed that the gallium oxide corundum structure (α-Ga 2 _{O 3)} is formed on each of the thin film. It is considered that the platinum thin film and the gold thin film were oriented uniaxially, and as a result, a crystalline gallium oxide thin film was formed on the platinum thin film and the gold thin film. When a gallium oxide thin film was formed on a platinum or gold thin film at a gallium oxide film forming temperature of 600 ° C., a β-type gallium oxide thin film could be formed. Also in this case, it was confirmed that the platinum thin film / gold thin film was uniaxially oriented after the film formation.

On the Si {100} substrate (thermal oxide film 100 nm, N-type, 0.525 mm thickness) shown in FIG. 10, gallium oxide formation using mist CVD is performed on a sample in which titanium is 10 nm and platinum thin film is 35 nm. Later, β-gallium gallium oxide (β-Ga ₂ O ₃ ) was confirmed. This platinum thin film was already uniaxially oriented before the gallium oxide film was formed, and a β-type gallium oxide thin film could be formed on the uniaxially oriented platinum thin film.
Even in the sample in which gold was deposited to 35 nm by a vapor deposition method on the Si {100} substrate (thermal oxide film 100 nm, N-type, 0.525 mm thickness) shown in FIG. 11, after gallium oxide formation using the mist CVD method was performed. A gallium oxide (β-Ga ₂ O ₃ ) having a β-gallia structure was confirmed. This gold thin film was already uniaxially oriented before the gallium oxide film was formed, and a β-type gallium oxide thin film could be formed on the uniaxially oriented gold thin film.

The considerations for each experiment are as follows.
When a gallium oxide film is formed directly on the Si substrate, specifically, the plane orientations {100}, {111}, {110}, the gallium oxide becomes amorphous and forms crystalline gallium oxide. I couldn't. Moreover, when a platinum thin film was directly formed on a Si substrate and a gallium oxide film was formed thereon, the gallium oxide became amorphous, and crystalline gallium oxide could not be formed. The platinum thin film was not uniaxially oriented even after the gallium oxide film was formed.

When an aluminum film is formed on a sapphire substrate using the above sputtering apparatus and gallium oxide is formed on the aluminum film, the gallium oxide becomes amorphous and crystalline gallium oxide cannot be formed. It was.
As described above, when the platinum or gold thin film is uniaxially oriented by the time of forming the oxide thin film, the oxide thin film having good crystallinity has been successfully formed.

1 Oxide thin film 2 Platinum, gold or palladium thin film or substrate 3 Oxide thin film 4 Platinum, gold or palladium thin film 5 Base material 6 Oxide thin film 7 Platinum, gold or palladium thin film 8 Block layer 9 Base material 10 Oxide Thin film 11 Thin film of platinum, gold or palladium 12 Adhesion enhancement layer 13 Base material 14 Oxide thin film 15 Thin film of platinum, gold or palladium 16 Block layer 17 Adhesion enhancement layer 18 Base material 19 Oxide thin film 20 Buffer layer 21 Platinum, Gold or palladium thin film 22 Block layer 23 Adhesion enhancement layer 24 Base material 25: Mist CVD device 26: Film formation sample 27: Sample stage 28: Carrier gas source 29: Flow rate control valve 30: Mist generation source 30a: Raw material solution 31: Mist generation source 31a: Water 32: Ultrasonic vibrator 33: Film formation chamber 34: Heater

Claims (15)

A crystalline oxide thin film comprising at least one of indium, aluminum, gallium, or a combination thereof, which is grown on a base made of a metal thin film or metal substrate of platinum, gold or palladium that is uniaxially oriented. seen including,
The crystalline oxide thin film is a semiconductor device or a substrate containing at least one of indium and gallium . Least indium was formed on an underlying body comprising oriented have Rukin or palladium metal thin film or metal substrate in a uniaxial, aluminum, any one of gallium, or a crystalline oxide film of a combination of these, the semiconductor device Or substrate. The semiconductor device or substrate according to claim 1, wherein the crystalline oxide thin film is an oxide thin film that is crystal-grown on the base body from the base body side. The crystalline oxide thin film is an oxide thin film that is crystal-grown on the base body from the base body side by an oxidation reaction of a gallium compound, an indium compound, an aluminum compound, or a metal compound that is a combination thereof. The semiconductor device or substrate according to claim 3. The crystalline oxide thin film is made of In. _X Al _Y Ga _Z O ₃ 5. The semiconductor device according to claim 1, wherein (0 ≦ X ≦ 2, 0 ≦ Y ≦ 2, 0 ≦ Z ≦ 2, X + Y + Z = 1.5 to 2.5). Or substrate. The semiconductor device or substrate according to any one of claims 1 to 5, wherein the base body is oriented in {111}. The base is a metal thin film,
The semiconductor according to any one of claims 1 to 6, wherein a non-oriented layer that is not uniaxially oriented is formed directly or via another layer under the metal thin film. Device or substrate. The semiconductor device or substrate according to claim 7, wherein the non-oriented layer has any of the following configurations.
(1) One or a combination of metal oxides .
(2) One or a combination of conductive oxides.
(3) a silicon oxide, zinc oxide, indium oxide, tin _{oxide, ITO, InGaZnO, In X Al} Y Ga Z O 3 (0 ≦ X ≦ 2,0 ≦ Y ≦ 2,0 ≦ Z ≦ 2, X + Y + Z = 1. 5 to 2.5) or a combination of these. The base is a metal thin film,
9. The metal thin film according to claim 1 , wherein the metal thin film is formed directly or via another layer on a base material of Si, sapphire, or silicon oxide. Semiconductor device or substrate. The semiconductor device or substrate according to claim 9 , wherein a layer in which one or a plurality of metals is combined is formed between the base material and the metal thin film . The semiconductor device or substrate according to claim 9 or 10, wherein the base material is made of a Si {100} substrate. The semiconductor device or substrate according to claim 11, wherein a Si semiconductor device is formed on the base material, and the crystalline oxide thin film is used for forming a semiconductor device having a function different from that of the Si semiconductor device. Semiconductor device, or the substrate according to any one of claims 1 to 12, characterized in that before Kiyui crystalline oxide thin film having corundum structure or β gallia structure, the bixbyite structure. The crystalline oxide thin film, at least indium, aluminum, any one or a nitride semiconductor which is a combination of these gallium, characterized in that it is formed directly or via another layer, claims The semiconductor device or substrate according to any one of claims 1 to 13 . The nitride semiconductor is In _X2 Al _Y2 Ga _Z2 15. The semiconductor device or substrate according to claim 14, comprising N (0 ≦ X2 ≦ 1.1, 0 ≦ Y2 ≦ 1.1, 0 ≦ Z2 ≦ 1.1, X2 + Y2 + Z2 = 0.9 to 1.1). .