TWI594432B - Oxide semiconductor element, method for manufacturing oxide semiconductor element, display device and image sensor - Google Patents

Description

Oxide semiconductor device, method of manufacturing oxide semiconductor device, display device, and image sensor

The present invention relates to an oxide semiconductor device, a method of manufacturing an oxide semiconductor device, a display device, and an image sensor.

In recent years, an In-Ga-Zn-O-based oxide semiconductor thin film has been used for an oxide semiconductor element (channel layer) of an oxide semiconductor element, particularly a thin film transistor (TFT). Development is prevalent. The oxide semiconductor thin film can be formed at a low temperature, exhibits a higher mobility than amorphous silicon, and is transparent to visible light, so that a flexible thin film transistor can be formed on a substrate such as a plastic plate or a film.

However, when it is suitable for practical use and the above-mentioned thin film transistor is used on a driving circuit of a liquid crystal display (LCD) or an organic electroluminescence (EL) display, etc., the operation of the thin film transistor is driven. The instability (ΔVth: threshold shift) or the operational instability at the time of light irradiation becomes a problem.

The operational instability during driving of a thin film transistor is caused by the fact that the In-Ga-Zn-O-based oxide is low in resistance to moisture, oxygen, pollution, etc., so that the In-Ga-Zn-O system is used. When the oxide-based oxide semiconductor layer is exposed to the atmosphere, the oxide deteriorates with time.

Further, the operational instability at the time of light irradiation is caused by the backlight of the liquid crystal display or the blue light-emitting layer of the organic electroluminescence having an emission peak of about λ = 450 nm, and the bottom of the emission spectrum is continued to 420 nm. The in-Ga-Zn-O system to be irradiated includes at least one oxide semiconductor layer selected from the group consisting of In, Zn, Ga, and Sn, and generally has light in a short-wavelength region with respect to visible light (light having a wavelength of 400 nm or more and 450 nm or less). ) and the work is unstable.

In the above-mentioned Japanese Patent No. 4982619, a protective layer is formed on the exposed surface of an oxide semiconductor layer mainly composed of an In—Ga—Zn—O-based oxide to protect the oxide semiconductor layer from the oxide semiconductor layer. Invasion of moisture or the like, thereby improving the operational instability during driving of the thin film transistor. Further, it has been revealed that the oxygen diffusion control at the time of formation of the protective film improves the operational instability at the time of light irradiation.

Further, Japanese Laid-Open Patent Publication No. 2009/075281 discloses a thin film transistor in which a light shielding film is provided on a protective layer for protecting an oxide semiconductor layer mainly composed of an In—Ga—Zn—O based oxide. It is composed of a resin material or a metal material having a large absorption or reflection in a region having a wavelength of 500 nm or less.

However, the protective layer of Japanese Patent No. 4992619 cannot sufficiently protect the oxide semiconductor layer with respect to moisture, oxygen, contamination, or the like.

In addition, in the international publication No. 2009/075281, only a light-shielding film made of a resin material is provided on the protective layer, and the oxide semiconductor layer cannot be sufficiently protected from moisture, oxygen, or the like. Further, even if only a light-shielding film made of a metal material is provided on the protective layer, an unnecessary manufacturing cost is required due to the presence of the light-shielding film.

The present invention has been made in view of the above circumstances, and an object of the invention is to provide an oxide semiconductor device or a method for manufacturing an oxide semiconductor device which can ensure operational stability at the time of light irradiation, suppress manufacturing cost, and improve a protective function of an oxide semiconductor layer. , display device and image sensor.

The above problems of the present invention are solved by the following methods.

<1> An oxide semiconductor device comprising: an electrode comprising: a metal material; an oxide semiconductor layer comprising at least one selected from the group consisting of In, Zn, Ga, and Sn; and a protective layer laminated on the oxide semiconductor layer Further, the protective layer includes an inorganic insulating layer and a metal layer made of the same metal material as the electrode.

<2> The oxide semiconductor device according to <1>, wherein the total thickness of the metal layer is 50 nm or more.

The oxide semiconductor device according to the above aspect, wherein the electrode is a source in which the protective layer is sandwiched between the oxide semiconductor layers and can be electrically connected to each other via the oxide semiconductor layer. The electrode and the drain electrode include a gate electrode disposed via a gate insulating layer on a side opposite to a side of the oxide semiconductor layer on which the protective layer is disposed, and at least a portion of the metal layer is formed by the source electrode and the source electrode The drain electrode is made of the same metal material and is disposed on the top of the above protective layer.

The oxide semiconductor device according to any one of the above aspects, wherein the metal layer is a plurality of layers.

The oxide semiconductor device according to the above <4>, wherein the plurality of metal layers include a sacrificial metal layer disposed on top of the protective layer, and a reflective metal layer disposed on the inorganic insulating layer The inside of the layer has a higher reflectance for light having a wavelength of 400 nm or more and 450 nm or less than the above-mentioned worn metal layer.

The oxide semiconductor device according to the above <3>, wherein the metal layer is made of the same metal material as the gate electrode.

The oxide semiconductor device according to any one of the above aspects, wherein the inorganic insulating layer contains a metal material of the metal layer.

<8> A method of producing an oxide semiconductor device, comprising: forming an oxide semiconductor layer, wherein the oxide semiconductor layer comprises at least one selected from the group consisting of In, Zn, Ga, and Sn; and the step of forming an electrode, the electrode And a step of forming a protective layer, wherein the protective layer is laminated on the oxide semiconductor layer, and the protective layer comprises an inorganic insulating layer and a metal layer made of the same metal material as the electrode.

The method for producing an oxide semiconductor device according to the above aspect, wherein the step of forming the electrode includes: forming a metal conductive film on the inorganic insulating layer and the oxide semiconductor layer; and patterning the metal conductive film a step of forming a source electrode and a drain electrode; and in the step of forming the metal layer in the step of forming the protective layer, in the step of forming the electrode, When the metal conductive film is patterned, the source electrode and the drain electrode are formed, and the metal conductive film remains in the inorganic insulating layer to form the metal layer.

The display device of any one of <1> to <7> above.

The oxide semiconductor device according to any one of the above-mentioned <7>, wherein the oxide semiconductor device according to any one of the above <7>.

According to the present invention, it is possible to ensure the operational stability at the time of light irradiation, and to suppress the manufacturing cost and improve the protective function of the oxide semiconductor layer.

10, 30, 40‧‧‧ film transistor

10a‧‧‧Drive film transistor

10b‧‧‧Transistor film transistor

12‧‧‧Substrate

14‧‧‧ gate electrode

14A‧‧‧Electrical film

16‧‧‧ gate insulation

16A, 26A, 34A, 34B, 210‧‧‧ insulating film

18‧‧‧Oxide semiconductor layer

18A‧‧‧Oxide semiconductor film

20‧‧‧Source electrode

20A, 36C‧‧‧Metal conductive film

22‧‧‧汲electrode

24, 32, 42‧‧ ‧ protective layer

26, 34, 44‧‧‧Inorganic insulation

28, 36, 46‧‧‧ metal layers

36A‧‧‧reflective metal layer

36B‧‧‧Worn metal layer

100‧‧‧Liquid crystal display device

102‧‧‧ Passivation layer

104‧‧‧ pixel lower electrode

106‧‧‧for the upper electrode

108‧‧‧Liquid layer

110‧‧‧Red, Green and Blue Color Filters

112, 220‧‧‧ gate wiring

112a, 112b‧‧‧ polarizing plate

114, 222‧‧‧ data wiring

116‧‧‧Contact hole

118‧‧‧ capacitor

200‧‧‧Organic electroluminescent display device

202‧‧‧Substrate insulation

204‧‧‧Color filter layer

206‧‧‧ pixel electrodes (anode)

208‧‧‧Connecting electrode

212‧‧‧Organic layer

214‧‧‧ cathode

224‧‧‧Drive wiring

226‧‧‧ capacitor

1 is a schematic view showing an example of a thin film transistor according to an embodiment of the present invention, that is, a bottom gate structure and a top contact type thin film transistor.

2 is a schematic view showing another example of a thin film transistor of the embodiment of the present invention, that is, a bottom gate structure and a top contact type thin film transistor.

3 is a schematic view showing still another example of a thin film transistor according to an embodiment of the present invention, that is, a bottom gate structure and a top contact type thin film transistor.

4(A) to 4(F) are diagrams showing a series of manufacturing steps of the thin film transistor shown in Fig. 1.

5(A) to 5(C) are diagrams showing a series of manufacturing steps of the thin film transistor subsequent to FIG. 4(F).

6(A) to 6(F) are a series of thin film transistors shown in FIG. Make a step map.

7(A) to 7(E) are diagrams showing a series of manufacturing steps of the thin film transistor subsequent to FIG. 6(F).

Fig. 8 is a schematic cross-sectional view showing a part of a liquid crystal display device according to an embodiment of the photovoltaic device of the present invention.

Fig. 9 is a schematic configuration diagram of electrical wiring of the liquid crystal display device shown in Fig. 8;

Fig. 10 is a schematic cross-sectional view showing a part of an active matrix type organic electroluminescence display device according to an embodiment of the photovoltaic device of the present invention.

Fig. 11 is a schematic configuration diagram of electrical wiring of the organic electroluminescence display device shown in Fig. 10;

Fig. 12 is a graph showing the calculation results of ΔVth at each wavelength of Example 1, Example 2, and Comparative Example 1 with the wavelength on the horizontal axis and ΔVth as the vertical axis.

Hereinafter, an oxide semiconductor device and a method of manufacturing an oxide semiconductor device according to embodiments of the present invention will be specifically described with reference to the accompanying drawings. In the drawings, members (components) having the same or corresponding functions are denoted by the same reference numerals, and their description will be appropriately omitted. In addition, the terms "upper" and "lower" used in the following description are terms used for convenience, and should not be limited to the direction.

1. Oxide semiconductor device: schematic structure of thin film transistor

The oxide semiconductor device according to the embodiment of the present invention is a thin film transistor (TFT), a photo diode, or the like. Hereinafter, a thin film transistor will be described as an example of an oxide semiconductor device.

The thin film transistor of the present embodiment is an active element including at least a gate electrode, a gate insulating layer, an oxide semiconductor layer, a source electrode, and a drain electrode, and has a function of applying a voltage to the gate electrode The current flowing through the peroxide semiconductor layer is controlled to switch the current between the source electrode and the drain electrode.

As an element structure of a thin film transistor, there is a so-called inverse stagger structure (also referred to as a bottom gate type) and a staggered structure (also referred to as a top gate type) based on the position of the gate electrode. (top gate type)), but an inverse staggered structure is used in the present embodiment.

Further, the contact portion between the oxide semiconductor layer and the source electrode and the drain electrode (referred to as "source-drain electrode" as appropriate) may be a so-called top contact type or bottom contact type ( Bottom contact type).

In addition, the top gate type refers to a form in which a gate electrode is disposed on the upper side of the gate insulating layer and an oxidation is formed on the lower side of the gate insulating layer when the substrate on which the thin film transistor is formed is the lowermost layer. The material semiconductor layer and the bottom gate type are those in which a gate electrode is disposed on the lower side of the gate insulating layer and an oxide semiconductor layer is formed on the upper side of the gate insulating layer. Further, the bottom contact type refers to a form in which the source-drain electrode is formed earlier than the oxide semiconductor layer and the lower surface of the oxide semiconductor layer is in contact with the source-drain electrode, and the top contact type is as follows The morphology, that is, the oxide semiconductor layer is formed earlier than the source-drain electrode, and the upper surface of the oxide semiconductor layer is in contact with the source-drain electrode.

1 is a thin film transistor, that is, a bottom gate showing an embodiment of the present invention. A schematic view of an example of a thin-film transistor of a polar structure and a top contact type.

The thin film transistor 10 shown in FIG. 1 includes: a gate electrode 14 formed on one main surface of the substrate 12; a gate insulating layer 16 covering the gate electrode 14; and an oxide semiconductor layer 18 disposed on the gate The opposite side of the side of the gate electrode 14 is disposed of the pole insulating layer 16. Further, the thin film transistor 10 includes a source electrode 20 and a drain electrode 22 which are disposed apart from each other on the side opposite to the side where the gate insulating layer 16 of the oxide semiconductor layer 18 is disposed, and a protective layer 24 formed thereon. The surface of the oxide semiconductor layer 18 exposed between the source electrode 20 and the drain electrode 22 is formed.

Further, in the present embodiment, the protective layer 24 includes an inorganic insulating layer 26 adjacent to the oxide semiconductor layer 18, and the metal layer 28 is not adjacent to the source electrode 20 and the drain electrode 22 and is adjacent to the inorganic insulating layer 26.

2 is a schematic view showing another example of a thin film transistor of the embodiment of the present invention, that is, a bottom gate structure and a top contact type thin film transistor.

The thin film transistor 30 shown in FIG. 2 includes a substrate 12, a gate electrode 14, a gate insulating layer 16, an oxide semiconductor layer 18, a source electrode 20, and a gate electrode 22, similarly to the thin film transistor 10. Further, the thin film transistor 30 has a protective layer 32 which is different from the protective layer 24 of the thin film transistor 10.

Further, in the present example, the protective layer 32 includes an inorganic insulating layer 34 adjacent to the oxide semiconductor layer 18 and a metal layer 36 having a two-layer structure. The metal layer 36 includes a reflective metal layer 36A disposed in the inorganic insulating layer 34, and a worn metal layer 36B adjacent to the reflective metal layer 36A and adjacent to the inorganic insulating layer 34 on the outer side (opposite side in the direction of the substrate 12).

3 is a schematic view showing another example of a thin film transistor according to an embodiment of the present invention, that is, a bottom gate structure and a top contact type thin film transistor.

The thin film transistor 40 shown in FIG. 3 includes a substrate 12, a gate electrode 14, a gate insulating layer 16, an oxide semiconductor layer 18, a source electrode 20, and a drain electrode 22, similarly to the thin film transistor 10. Further, the thin film transistor 40 has a protective layer 42 which is different from the protective layer 24 of the thin film transistor 10.

Further, in this example, the protective layer 42 includes an inorganic insulating layer 44 adjacent to the oxide semiconductor layer 18, and a metal layer 46 disposed in the inorganic insulating layer 44.

Further, the thin film transistor of the present embodiment may have various configurations in addition to the above, and for example, an insulating layer may be provided on the substrate 12, or the oxide semiconductor layer 18 may be a plurality of layers, or the oxide semiconductor layer 18 may be A configuration in which a contact layer is provided between the source electrode 20 and the drain electrode 22.

Hereinafter, each constituent element of the thin film transistor 10, the thin film transistor 30, and the thin film transistor 40 will be described in detail.

<Detailed Structure of Thin Film Transistor>

-Substrate -

The shape, structure, size, and the like of the substrate 12 are not particularly limited as long as the main surface on which the film can be formed, and may be appropriately selected depending on the purpose. The structure of the substrate 12 may be a single layer structure or a laminate structure.

The material of the substrate 12 is not particularly limited, and for example, an inorganic substrate such as glass or yttrium-stabilized zirconia (YSZ), a resin substrate, or a composite material thereof can be used. Which is lightweight and flexible. In other words, a resin substrate or a composite material thereof is preferred. Specifically, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polystyrene, polycarbonate, polyfluorene can be used. , polyether oxime, polyarylate, allyl diglycol carbonate, polyamine, polyimine, polyamidimide, polyether phthalimide, polybenzoxazole, polyphenylene sulfide, Polycycloolefin, norbornene resin, fluororesin such as polychlorotrifluoroethylene, liquid crystal polymer, acrylic resin, epoxy resin, fluorenone resin, ionomer resin, cyanate resin, cross-linked fumaric acid Synthetic resin substrate such as diester, cyclic polyolefin, aromatic ether, maleimide olefin, cellulose, episulfide compound, composite plastic material with cerium oxide particles, metal nanoparticle, inorganic oxide Composite plastic materials such as rice particles, inorganic nitride nanoparticles, composite plastic materials with carbon fibers and carbon nanotubes, composite plastic materials with glass flakes, glass fibers, glass beads, clay minerals or mica-derived crystal structures Composite plastic material for particles, in thin a laminated plastic material having at least one joint interface between the glass and the above-mentioned individual organic material, a composite material having barrier properties having at least one joint interface by alternately laminating the inorganic layer and the organic layer, a stainless steel substrate or a stainless steel A metal multilayer substrate in which a dissimilar metal layer is laminated, an aluminum substrate, or an aluminum substrate having an oxide film which is improved in insulation properties by surface oxidation treatment (for example, anodization treatment). Further, the resin substrate is preferably excellent in heat resistance, dimensional stability, solvent resistance, electrical insulating properties, workability, low gas permeability, or low moisture absorption. The resin substrate preferably has a gas barrier layer for preventing moisture or oxygen from permeating, or an undercoat layer for improving the flatness of the resin substrate or the adhesion to the lower electrode. Here, the undercoat layer is formed on the resin substrate In the case of a single surface, the resin substrate is warped due to internal residual stress. Therefore, it is preferable to apply the coating on both surfaces or to control the film quality with low stress, or to control by compression/tensile stress by lamination. . Further, the undercoat layer is preferably a material for use in a gate insulating layer 16 to be described later, etc., in order to improve barrier properties.

-Gate electrode -

The gate electrode 14 is formed on one main surface of the substrate 12.

The conductive film constituting the gate electrode 14 is preferably a conductive film having high conductivity. For example, a metal film such as Al, Mo, Cr, Ta, Ti, Au, Ag, or Al-Nd, Ag alloy, or tin oxide can be used. A metal oxide conductive film such as zinc oxide, indium oxide, indium tin oxide (ITO) or indium zinc oxide (IZO). Here, as described later, since the material of the metal layer is the same material as that of the gate electrode 14, it is preferable to use a metal film.

- Gate insulation -

The gate insulating layer 16 is laminated on the surface of the gate electrode 14 on the opposite side of the substrate 12 and on the exposed surface of the substrate 12 so as to cover the gate electrode 14.

The insulating film constituting the gate insulating layer 16 is preferably an insulating film having high insulating properties, and is, for example, SiO ₂ , SiN _x (x is nitrogen non-stoichiometric), SiON, Al ₂ O ₃ , Y ₂ O ₃ , An insulating film of Ta ₂ O ₅ or HfO ₂ or an insulating film containing at least two or more of these compounds.

-Oxide semiconductor layer -

The oxide semiconductor layer 18 is laminated on the surface of the gate insulating layer 16 on the opposite side of the gate electrode 14.

The oxide semiconductor layer 18 may be mainly composed of an oxide semiconductor containing at least one selected from the group consisting of In, Zn, Ga, and Sn, and may contain impurities or the like. Here, the "main body" indicates the component having the largest content among the constituent components constituting the oxide semiconductor layer 18.

The oxide semiconductor may be either amorphous or crystalline, but an amorphous oxide semiconductor is preferably used. When the semiconductor film is composed of an oxide semiconductor, the mobility of charges is much higher than that of the amorphous germanium semiconductor film, and thus can be driven with a low voltage. Further, when an oxide semiconductor is used, a semiconductor film having a relatively high light transmittance can be usually formed. Further, since an oxide semiconductor, particularly an amorphous oxide semiconductor, can be uniformly formed at a low temperature (for example, room temperature), it is particularly advantageous when a flexible resin substrate such as plastic is used.

The constituent material of the oxide semiconductor is not particularly limited as long as it contains at least one selected from the group consisting of In, Zn, Ga, and Sn, and is preferably an oxide containing at least one of In, Ga, and Zn ( For example, In-O system). In particular, it is preferable to contain at least two kinds of oxides of In, Ga, and Zn (for example, In-Zn-O-based, In-Ga-O-based, and Ga-Zn-O-based), and more preferably include In, Ga, and All oxides of Zn. As the In—Ga—Zn—O-based oxide semiconductor, an oxide semiconductor having a composition in a crystalline state of InGaO ₃ (ZnO) _m (m is a natural number less than 6) is preferable, and more preferably, InGaZnO is preferable. ₄ . The characteristics of the oxide semiconductor having such a composition tend to increase the electron mobility as the conductivity increases. Among them, the composition ratio of the In-Ga-Zn-O system is not necessarily strictly In:Ga:Zn=1:1:1.

The layer structure of the oxide semiconductor layer 18 may also include two or more layers, and is oxidized. The semiconductor layer 18 includes a low resistance layer and a high resistance layer. Preferably, the low resistance layer is in contact with the gate insulating layer 16, and the high resistance layer is in electrical contact with at least one of the source electrode 20 and the drain electrode 22.

The thickness of the oxide semiconductor layer 18 is not particularly limited, and is preferably 30 nm or more and 60 nm or less from the viewpoint of ensuring both carrier migration and cost reduction.

-Source-drain electrode -

The source electrode 20 and the drain electrode 22 are formed on the surface of the oxide semiconductor layer 18 on the opposite side of the gate insulating layer 16 with a space therebetween, and the oxide semiconductor layer can be applied by the applied voltage of the gate electrode 14. 18 conduction.

The conductive film constituting the source electrode 20 and the drain electrode 22 is made of a conductive film having high conductivity. For example, a metal film such as Al, Mo, Cr, Ta, Ti, Au, Ag, or Al-Nd or Ag alloy can be used. It is formed by a metal oxide conductive film such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO) or indium zinc oxide (IZO). Here, as described later, since the material of the metal layer is the same material as that of the source electrode 20 and the gate electrode 22, it is preferable to use a metal film. Moreover, as the source electrode 20 and the drain electrode 22, these conductive films can be used in a single layer structure or a laminated structure of two or more layers.

In consideration of film formability, patterning property by electroplating or lift off method, conductivity, and the like, the film thickness of the formed conductive film is preferably 1 nm or more and 1000 nm or less, and more preferably 50 nm or more. Below 500 nm.

-The protective layer-

Protective layers of the thin film transistor 10, the thin film transistor 30, and the thin film transistor 40 24. The protective layer 32 and the protective layer 42 are laminated on the oxide semiconductor layer 18 exposed between the source electrode 20 and the drain electrode 22 to protect the oxide semiconductor layer 18 from water, oxygen, or the like.

Further, each of the protective layer 24, the protective layer 32, and the protective layer 42 includes an inorganic insulating layer 26, an inorganic insulating layer 34, an inorganic insulating layer 44, and a metal layer 28, a metal layer 36, and a metal layer 46.

Thereby, in the thin film transistor 10, the thin film transistor 30, and the thin film transistor 40 of the present embodiment, the outer side of the protective layer 24, the protective layer 32, and the protective layer 42 (opposite side of the substrate 12) is directed to the oxide semiconductor layer. Since light having an incident wavelength of 400 nm or more and 450 nm or less on the 18 side is reflected by the metal layer 28, the metal layer 36, and the metal layer 46, the amount of light reaching the oxide semiconductor layer 18 can be suppressed. Therefore, even if the oxide semiconductor layer 18 contains at least one selected from the group consisting of In, Zn, Ga, and Sn and does not withstand light having a wavelength of 400 nm or more and 450 nm or less (even if the operation of the thin film transistor is unstable), The amount of light reaching the oxide semiconductor layer 18 is suppressed, so that the operational stability of the thin film transistor 10, the thin film transistor 30, and the thin film transistor 40 at the time of light irradiation can be ensured.

Further, the denseness of the metal layer 28, the metal layer 36, and the metal layer 46 is higher than that of the inorganic insulating layer 26, the inorganic insulating layer 34, and the inorganic insulating layer 44 which are used as a single protective layer as a normal protective layer, and thus water, oxygen, etc. It is difficult to transmit the outer side of the protective layer 24, the protective layer 32, and the protective layer 42 to the side of the oxide semiconductor layer 18, whereby the protective function to the oxide semiconductor layer 18 can be improved.

Further, compared with the case where an absorbing film that absorbs light is used as a light shielding layer, By using the metal layer 28, the metal layer 36, and the metal layer 46, generation of heat due to light irradiation can be suppressed.

Further, since the metal layer 28, the metal layer 36, the protective layer 24 other than the metal layer 46, the protective layer 32, and the portion of the protective layer 42 are the inorganic insulating layer 26, the inorganic insulating layer 34, and the inorganic insulating layer 44, it is easy to be separated from moisture. The metal layer 28, the metal layer 36, and the metal layer 46 are less likely to rust than in the case of the transmitted organic insulating layer.

The constituent material of the inorganic insulating layer 26, the inorganic insulating layer 34, and the inorganic insulating layer 44 is not particularly limited, and examples thereof include SiO ₂ , SiO, MgO, Al ₂ O ₃ , GeO, NiO, SrO, Y ₂ O ₃ , and ZrO ₂ . CeO ₂ , Rb ₂ O, Sc ₂ O ₃ , La ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₃ , an inorganic material such as a metal oxide such as Ta ₂ O ₅ , Nb ₂ O ₅ , HfO ₂ , Ga ₂ O ₃ or TiO ₂ or a metal nitride such as AlN, SiN or SiN _x O _y . Wherein, preferably SiO ₂ film speed of Gd ₂ O ₃ or the like, more preferably Gd ₂ O _3. Further, a material which is the same as the oxide semiconductor layer 18 such as the In—Ga—Zn—O-based material by changing the resistivity or the like by oxygen amount adjustment, composition adjustment, element doping or the like can be used.

Moreover, from the viewpoint of improving the adhesion to the oxide semiconductor layer 18, the inorganic insulating layer 26, the inorganic insulating layer 34, and the inorganic insulating layer 44 preferably contain at least a part of the metal constituting the oxide semiconductor layer 18. Similarly, the inorganic insulating layer 26, the inorganic insulating layer 34, and the inorganic insulating layer 44 are preferably metal materials including the metal layer 28, the metal layer 36, and the metal layer 46.

The thickness of the inorganic insulating layer 26, the inorganic insulating layer 34, and the inorganic insulating layer 44 is preferably 1 μm or more and 1 mm or less from the viewpoint of both the protective function and the cost. Further preferably, it is 5 μm or more and 100 μm or less, and most preferably 10 μm. Above and 50 μm or less.

Further, as shown in FIGS. 1 and 2, the thickness of the inorganic insulating layer 26 and the inorganic insulating layer 34 including the reflective metal layer 36A is preferably equal to or greater than the thickness of the source electrode 20 and the drain electrode 22 to laminate The metal layer 28 and the worn metal layer 36B are not in contact with the source electrode 20 and the drain electrode 22, and are preferably over the source electrode 20 in order to prevent erroneous contact caused by film formation errors or patterning errors. The thickness of the drain electrode 22.

The metal layer 28, the metal layer 36, and the metal layer 46 are not in contact with the source electrode 20 and the gate electrode 22 (non-conducting), and the constituent materials can be used in the same target (the same material). From the viewpoint of suppressing the manufacturing cost, it is preferably the same as the source electrode 20 and the drain electrode 22. The constituent materials of the metal layer 28, the metal layer 36, and the metal layer 46 are preferably the same as those of the gate electrode 14 from the same viewpoint. Further, from the viewpoint of further suppressing the manufacturing cost, the constituent materials of the metal layer 28, the metal layer 36, and the metal layer 46 are preferably the same as those of the source electrode 20, the gate electrode 22, and the gate electrode 14.

Specifically, the constituent material may be a metal material such as Al, Cu, Ni, Mo, Cr, Ta, Ti, Au, Ag, Pt, Rh, Sn, Fe, Nb, Si, or Mo-Nb. The constituent material of the metal layer 28, the metal layer 36, and the metal layer 46 is preferably Ag, Al, Rh, or Mo having a reflectance of 50% or more for light having a wavelength of 400 nm or more and 450 nm or less.

The metal layer of the present embodiment is preferably formed on at least a portion of the protective layer 24 and the protective layer 32, such as the metal layer 28 and the metal layer 36. The reason is such as As will be described later, the formation of the metal layer 28 and the metal layer 36 and the formation of the source electrode 20 and the drain electrode 22 can be simultaneously performed, thereby simplifying the manufacturing process.

Further, the metal layer of the present embodiment is not a single layer like the metal layer 28 or the metal layer 46, and is preferably a multilayer such as the metal layer 36. This is because if it is a multilayer, deterioration of the metal layer located inside can be suppressed. Further, it is more preferable that the inorganic insulating layer is sandwiched between the plurality of layers.

Specifically, when the metal layer 36 shown in FIG. 2 is taken as an example, the worn metal layer 36B is disposed outside the reflective metal layer 36A via the inorganic insulating layer 34, and thus receives water or oxygen from the outside. Thereby, the reflective metal layer 36A located inside does not receive water, oxygen, etc., and can suppress deterioration (hydrogenation etc.) of the reflective metal layer 36A. Thereby, the reflective metal layer 36A can maintain the original function of the metal layer 36, that is, the reflective function.

The worn metal layer 36B receives water or oxygen, and thus it is preferable that the corrosion resistance is higher than that of the reflective metal layer 36A. On the other hand, it is preferable that the reflective metal layer 36A has a higher reflectance than the worn metal layer 36B. Further, since the reflective metal layer 36A has a low necessity for considering the corrosion resistance due to the presence of the worn metal layer 36B, the material having a high reflectance has a wide selection range.

The total thickness of the metal layer 28, the metal layer 36, and the metal layer 46 is not particularly limited, but is preferably 50 nm or more from the viewpoint of suppressing the capacitance of the metal layer 28, the metal layer 36, and the metal layer 46 from heat generation.

Moreover, in order to avoid electrical conduction between the metal layer 28 or the worn metal layer 36B and the source electrode 20 and the drain electrode 22, the thickness of the inorganic insulating layer 26 is thicker than that of the source electrode. The thickness of the pole 20 and the drain electrode 22 is set to a height that does not contact the source electrode 20 and the drain electrode 22. Further, the metal layer 46 or the reflective metal layer 36A is surrounded by the inorganic insulating layer 44 and the inorganic insulating layer 34, and is not in contact with the source electrode 20 and the drain electrode 22.

2. Method for producing an oxide semiconductor device: a method for manufacturing a thin film transistor

Next, a method of manufacturing the thin film transistor 10 will be described as an example of a method for producing an oxide semiconductor device according to the present embodiment.

(Method of Manufacturing Thin Film Transistor 10)

4(A) to 4(F) and Figs. 5(A) to 5(C) are diagrams showing a series of manufacturing steps of the thin film transistor 10.

- Gate electrode formation step -

First, a gate electrode forming step is performed. In the gate electrode forming step, the substrate 12 is prepared as shown in Fig. 4(A). Then, as shown in FIG. 4(B), a conductive film 14A is formed on the prepared substrate 12. As a film formation method of the conductive film 14A, a physical method such as a wet method such as a printing method or a coating method, a vacuum vapor deposition method, a sputtering method, or an ion plating method, or chemical vapor deposition is used. (Chemical Vapor Deposition, CVD), chemical methods such as plasma chemical vapor deposition, and the like, which are suitable for the materials used.

After the film formation, as shown in FIG. 4(C), the conductive film 14A is patterned into a predetermined shape by photolithography, etching, lift-off, or the like, whereby the gate electrode 14 is formed from the conductive film 14A. At this time, it is preferable to simultaneously pattern the gate electrode 14 and the gate wiring.

- gate insulating layer forming step, oxide semiconductor layer forming step, and inorganic insulating layer forming step -

Next, a gate insulating layer forming step, an oxide semiconductor layer forming step, and an inorganic insulating layer forming step are performed. The forming step may be sequentially performed in the order of the gate insulating layer forming step, the oxide semiconductor layer forming step, and the inorganic insulating layer forming step, but may be performed simultaneously, or may be performed only at the time of film formation as follows The sequence proceeds, and the patterning proceeds in the reverse order.

In the forming step, first, as shown in FIG. 4(D), the insulating film 16A, the oxide semiconductor film 18A, and the insulating film 26A are sequentially formed on the gate electrode 14 and the substrate 12.

As such a film forming method, a wet method such as a printing method or a coating method, a physical method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a chemical vapor deposition or a plasma chemical vapor deposition method is used. A method suitable for the materials used in the method and the like. Among these, from the viewpoint of easy control of the film thickness, a vapor phase film formation method such as a vacuum deposition method, a sputtering method, an ion plating method, a chemical vapor deposition method or a plasma chemical vapor deposition method is preferably used. In the vapor phase film formation method, a sputtering method or a Pulsed Laser Deposition (PLD) method is more preferable. Further, from the viewpoint of mass productivity, it is more preferably a sputtering method. For example, the film can be formed by a radio frequency (RF) magnetron sputtering film formation method to control the degree of vacuum and oxygen flow.

Further, in the aspect in which the films can be formed continuously, the film formation methods of the insulating film 16A, the oxide semiconductor film 18A, and the insulating film 26A are preferably the same.

Next, as shown in Fig. 4(E), by photolithography and etching or lifting The insulating film 26A is patterned into a predetermined shape by a separation method or the like. Thereby, the inorganic insulating layer 26 which is a part of the protective layer 24 is formed from the insulating film 26A.

Next, as shown in FIG. 4(F), the oxide semiconductor film 18A is patterned into a predetermined shape by photolithography, etching, lift-off, or the like. Thereby, the oxide semiconductor layer 18 is formed from the oxide semiconductor film 18A. Here, the channel portion of the oxide semiconductor film 18A opposed to the gate electrode 14 is covered by the inorganic insulating layer 26, and therefore the inorganic insulating layer 26 functions as an etch stop layer to the channel portion. Thereby, deterioration of the channel portion due to etching can be suppressed.

Next, as shown in FIG. 5(A), the insulating film 16A is patterned into a predetermined shape by photolithography, etching, lift-off, or the like. Thereby, the gate insulating layer 16 is formed from the insulating film 16A. Here, the channel portion of the oxide semiconductor film 18A opposed to the gate electrode 14 is covered by the inorganic insulating layer 26, and therefore the inorganic insulating layer 26 functions as an etch stop layer to the channel portion. Thereby, deterioration of the channel portion due to etching can be suppressed.

Next, as shown in FIG. 5(B), a metal conductive film 20A is formed on the inorganic insulating layer 26, on the oxide semiconductor layer 18, and on the gate insulating layer 16.

As a film formation method, a chemical method such as a wet method such as a printing method or a coating method, a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a chemical method such as chemical vapor deposition or plasma chemical vapor deposition is used. A method that is compatible with the materials used.

- source-drain electrode forming step and metal layer forming step -

Next, as shown in FIG. 5(C), by photolithography and etching or lift-off method, etc. The metal conductive film 20A is patterned into a predetermined shape, and the source electrode 20 and the drain electrode 22 are formed from the metal conductive film 20A. Here, the metal layer 28 as a part of the protective layer 24 may be formed thereafter, but from the viewpoint of simplifying the manufacturing process, it is preferable to pattern the metal conductive film 20A at the source electrode 20 and the drain electrode. Between the electrodes 22, the metal conductive film 20A remains on the surface of the inorganic insulating layer 26 to form the metal layer 28.

The thin film transistor 10 shown in Fig. 1 was produced by the above steps.

(Method of Manufacturing Thin Film Transistor 30)

Next, a method of manufacturing the thin film transistor 30 will be described as an example of a method of manufacturing the oxide semiconductor device of the present embodiment.

6(A) to 6(F) and Figs. 7(A) to 7(C) are diagrams showing a series of manufacturing steps of the thin film transistor 30.

- Gate electrode formation step -

First, a gate electrode forming step is performed. This gate electrode forming step is the same as the gate electrode forming step of the thin film transistor 10 as shown in FIGS. 6(A) to 6(C).

- gate insulating layer forming step, oxide semiconductor layer forming step, inorganic insulating layer forming step, and metal layer forming step -

Next, a gate insulating layer forming step, an oxide semiconductor layer forming step, an inorganic insulating layer forming step, and a metal layer forming step are performed. The forming step may be sequentially performed in the order of the gate insulating layer forming step, the oxide semiconductor layer forming step, and the inorganic insulating layer forming step, but may be performed simultaneously or may be performed as follows The film is carried out sequentially, and the patterning is carried out in the reverse order.

In the forming step, first, as shown in FIG. 6(D), the insulating film 16A, the oxide semiconductor film 18A, the insulating film 34A, and the metal conductive film 36C are sequentially formed on the gate electrode 14 and the substrate 12. . The film formation method is the same as the film formation method of each film of the thin film transistor 10.

Next, as shown in FIG. 6(E), the insulating film 34A and the metal conductive film 36C are patterned into a predetermined shape by photolithography, etching, lift-off, or the like. Thereby, a part of the inorganic insulating layer 34 is formed from the insulating film 34A, and the reflective metal layer 36A is formed from the metal conductive film 36C.

Next, as shown in FIG. 6(F), an insulating film 34B is formed on the oxide semiconductor film 18A and the reflective metal layer 36A. As a film formation method, a chemical method such as a wet method such as a printing method or a coating method, a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a chemical method such as chemical vapor deposition or plasma chemical vapor deposition is used. A method that is compatible with the materials used.

Next, as shown in FIG. 7(A), the insulating film 34B is patterned into a predetermined shape by photolithography, etching, lift-off, or the like. Thereby, the inorganic insulating layer 34 as a part of the protective layer 32 is formed from the insulating film 34B and a part of the inorganic insulating layer 34 previously formed. The reflective metal layer 36A is surrounded by the inorganic insulating layer 34 at the time of its formation.

Next, as shown in FIG. 7(B), the oxide semiconductor film 18A is patterned into a predetermined shape by photolithography, etching, lift-off or the like. Thereby, the oxide semiconductor layer 18 is formed from the oxide semiconductor film 18A. Here, the oxide semiconductor The channel portion of the film 18A opposed to the gate electrode 14 is covered by the inorganic insulating layer 34, and thus the inorganic insulating layer 34 functions as an etch stop layer to the channel portion. Thereby, deterioration of the channel portion due to etching can be suppressed.

Next, as shown in FIG. 7(C), the insulating film 16A is patterned into a predetermined shape by photolithography, etching, lift-off or the like. Thereby, the gate insulating layer 16 is formed from the insulating film 16A. Here, the channel portion of the oxide semiconductor film 18A opposed to the gate electrode 14 is covered by the inorganic insulating layer 34, and therefore the inorganic insulating layer 34 functions as an etch stop layer to the channel portion. Thereby, deterioration of the channel portion due to etching can be suppressed.

Next, as shown in Fig. 7(D), a metal conductive film 20A is formed on the inorganic insulating layer 34, on the oxide semiconductor layer 18, and on the gate insulating layer 16. The film formation method is the same as the film formation method of each film of the thin film transistor 30.

- source-drain electrode forming step and metal layer forming step -

Next, as shown in FIG. 7(E), the metal conductive film 20A is patterned into a predetermined shape by photolithography, etching, lift-off, or the like, and the source electrode 20 and the germanium are formed from the metal conductive film 20A. Polar electrode 22. Here, the worn metal layer 36B which is a part of the protective layer 32 may be formed thereafter, but from the viewpoint of simplifying the manufacturing process, it is preferable to pattern the metal conductive film 20A at the source electrode 20 and the germanium electrode 20 Between the electrode electrodes 22, the metal conductive film 20A remains on the inorganic insulating layer 34 to form the worn metal layer 36B.

The thin film transistor 30 shown in Fig. 2 was produced by the above steps.

3. Modifications

Further, the present invention will be described in detail with reference to the specific embodiments, but those skilled in the art will understand that the invention is not limited to the embodiments, and various other embodiments are possible within the scope of the invention.

For example, the step of annealing the oxide semiconductor film 18A (the oxide semiconductor layer 18) may be performed between any of the steps after the formation of the oxide semiconductor film 18A. The oxygen in the oxide semiconductor film 18A is diffused by the heat treatment temperature of the annealing, whereby the operational stability at the time of light irradiation can be improved. However, in the case of the present embodiment, the amount of light reaching the oxide semiconductor film 18A is suppressed by the metal layer 28, the metal layer 36, and the metal layer 46, so that the heat treatment temperature for annealing can be made low. Thereby, a wide selection of materials when obtaining the flexible substrate 12 is obtained.

Further, in the method of manufacturing the thin film transistor 10 and the thin film transistor 30, the source electrode 20 and the drain electrode 22 are made of the same metal material as the metal layer 28 or the worn metal layer 36B, but the gate may be used. The electrode material of the electrode layer 14 and the metal layer 28 or the worn metal layer 36B is the same metal material.

4. Application

The use of the thin film transistor 10, the thin film transistor 30, and the thin film transistor 40 of the present embodiment described above is not limited to the use of, for example, a photovoltaic device (for example, a liquid crystal display device or an organic electroluminescence (Electro Luminescence) display. A driving element of a device, a display device such as an inorganic electroluminescence display device, or the like, in particular, a device of a large area.

Further, the thin film transistor 10, the thin film transistor 30, and the thin film transistor 40 of the present embodiment are particularly suitable for a device which can be fabricated in a low temperature process using a resin substrate. It is preferably used as a driving element (drive circuit) of various electronic devices such as various sensors and micro electro mechanical systems.

5. Photoelectric device and sensor

The photovoltaic device or the sensor of the present embodiment is configured by including the thin film transistor 10 of the present embodiment.

As an example of the photovoltaic device, there are a display device (for example, a liquid crystal display device, an organic electroluminescence display device, an inorganic electroluminescence display device, etc.).

As an example of the sensor, an image sensor such as a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS) is preferable.

Hereinafter, a liquid crystal display device and an organic electroluminescence display device will be described as representative examples of the photovoltaic device or the sensor including the thin film transistor 10 of the present embodiment.

6. Liquid crystal display device

8 is a schematic cross-sectional view showing a part of a liquid crystal display device according to an embodiment of the photovoltaic device of the present invention, and FIG. 9 is a schematic configuration view showing electrical wiring of the liquid crystal display device.

As shown in FIG. 8, the liquid crystal display device 100 of the present embodiment is configured to include a bottom gate structure and a top contact type thin film transistor 10 shown in FIG. 1, and a liquid crystal layer 108 in the thin film transistor 10. The oxide semiconductor layer 18 protected by the passivation layer 102 is sandwiched by the pixel lower electrode 104 and its upper electrode 106; and red green blue (RGB) color The filter 110 is configured to emit light of different colors corresponding to each pixel, and has a polarizing plate 112a and a polarizing light on the substrate 12 side of the thin film transistor 10 and the red, green and blue color filter 110, respectively. Board 112b.

Further, as shown in FIG. 9, the liquid crystal display device 100 of the present embodiment includes a plurality of gate wirings 112 that are parallel to each other, and data wirings 114 that are parallel to each other and intersect with the gate wirings 112. Here, the gate wiring 112 is electrically insulated from the data wiring 114. The thin film transistor 10 is provided in the vicinity of the intersection of the gate wiring 112 and the data wiring 114.

The gate electrode 14 of the thin film transistor 10 is connected to the gate wiring 112, and the source electrode 20 of the thin film transistor 10 is connected to the data wiring 114. Further, the gate electrode 22 of the thin film transistor 10 is connected to the pixel lower electrode 104 via a contact hole 116 provided in the gate insulating layer 16 (a conductor is buried in the contact hole 116). The pixel lower electrode 104 and the grounded pair upper electrode 106 constitute a capacitor 118.

In the liquid crystal display device 100, a backlight including light having a wavelength of 400 nm or more and 450 nm or less is reflected and irradiated from the outside of the protective layer 24 of the thin film transistor 10 to the substrate 12 side (the thin film transistor forming side).

In the thin film transistor 10 of the present embodiment, the backlight toward the oxide semiconductor layer 18 side is reflected by the metal layer 28, so that the amount of light reaching the oxide semiconductor layer 18 can be suppressed. Therefore, even if the oxide semiconductor layer 18 contains at least one selected from the group consisting of In, Zn, Ga, and Sn and does not withstand light having a wavelength of 400 nm or more and 450 nm or less, since the amount of light reaching the oxide semiconductor layer 18 is suppressed, The operational stability of the thin film transistor 10 upon light irradiation can be ensured. Therefore, the reliability of the liquid crystal display device 100 Increase.

7. Organic electroluminescent display device

FIG. 10 is a schematic cross-sectional view showing a part of an active matrix type organic electroluminescence display device according to an embodiment of the photovoltaic device of the present invention, and FIG. 11 is a schematic configuration view showing electrical wiring.

Among the driving methods of the organic electroluminescence display device, there are two types of a simple matrix method and an active matrix method. The simple matrix method has the advantage of being inexpensive to manufacture, but since the pixels are selected one by one to cause the pixels to emit light, the number of scanning lines is inversely proportional to the lighting time of each scanning line. Therefore, it is difficult to achieve high definition and large screen. The active matrix method increases the manufacturing cost by forming a transistor or a capacitor for each pixel. However, since there is no problem that the number of scanning lines is not increased as in the simple matrix method, it is suitable for high definition and large screen.

In the active matrix type organic electroluminescence display device 200 of the present embodiment, the thin film transistor 10 of the bottom gate structure shown in FIG. 1 is provided on the substrate 12. The substrate 12 is, for example, a flexible support and a plastic film such as polyethylene naphthalate, and has a substrate insulating layer 202 on the surface in order to provide insulation. A patterned color filter layer 204 is disposed on the substrate 12. The gate electrode 14 is provided on the driving thin film transistor portion, and the gate insulating layer 16 is further provided on the gate electrode 14. A connection hole is formed in a portion of the gate insulating layer 16 for electrical connection. An oxide semiconductor layer 18 is provided on the driving thin film transistor portion, and a source electrode 20 and a drain electrode 22 are provided on the oxide semiconductor layer 18. The gate electrode 22 and the pixel electrode (anode) 206 of the organic electroluminescent element are continuously integrated, and the same material is used. The same step is formed. The drain electrode 22 of the switching thin film transistor and the driving thin film transistor are electrically connected by a connection hole by connecting the electrode 208. Further, the pixel electrode portion is entirely covered with the insulating film 210 except for the portion where the organic electroluminescent element is formed. An organic electroluminescence element portion is formed by providing an organic layer 212 including a light-emitting layer and a cathode 214 on the pixel electrode portion.

Further, as shown in FIG. 11, the organic electroluminescence display device 200 of the present embodiment includes a plurality of gate wirings 220 that are parallel to each other, and mutually parallel data wirings 222 and driving wirings 224 that intersect the gate wirings 220. . Here, the gate wiring 220 is electrically insulated from the data wiring 222 and the driving wiring 224. The gate electrode 14 of the thin film transistor 10b for switching is connected to the gate wiring 220, and the source electrode 20 of the thin film transistor 10b for switching is connected to the data wiring 222. Further, the gate electrode 22 of the switching thin film transistor 10b is connected to the gate electrode 14 of the driving thin film transistor 10a, and the driving thin film transistor 10a is held in an on state by using the capacitor 226. The source electrode 20 of the driving thin film transistor 10a is connected to the driving wiring 224, and the drain electrode 22 is connected to the organic layer 212.

The organic electroluminescence display device 200 is a bottom emission type in which light from the light-emitting layer is emitted from the substrate 12 side, and light having wavelengths of 400 nm or more and 450 nm or less is emitted from the outside of the protective layer 24 of the thin film transistor 10 (substrate 12) The light-emitting layer on the opposite side of the light is irradiated toward the side of the oxide semiconductor layer 18.

In the thin film transistor 10 of the present embodiment, the light toward the oxide semiconductor layer 18 side is reflected by the metal layer 28, so that the amount of light reaching the oxide semiconductor layer 18 can be suppressed. Thus, even the oxide semiconductor layer 18 is selected from the group consisting of In, Zn, Ga, and Sn. At least one of the light which does not withstand the wavelength of 400 nm or more and 450 nm or less can suppress the amount of light reaching the oxide semiconductor layer 18, and therefore can ensure the operational stability of the thin film transistor 10 at the time of light irradiation. Therefore, the reliability of the organic electroluminescence display device 200 is increased.

[Examples]

The examples are described below, but the invention is not limited by the examples.

(Example 1)

In the first embodiment, a thin film transistor of the same type as the thin film transistor 10 shown in Fig. 1 was produced.

Specifically, in the production of the thin film transistor of Example 1, first, a glass substrate for a liquid crystal display is prepared and cleaned (ultrasonic cleaning: alkaline cleaning solution, rinse, drying) Ozone treatment). Next, a direct current (DC) sputtering was used to form a Mo-Nb film of about 100 nm as a conductive film for a gate electrode. After the film formation, the conductive film is patterned to form a gate electrode. The patterning is carried out in the following order, that is, the positive type photoresist is applied by spin coating, and prebake (90 ° C: hot plate / 1 min), exposure (about 100 mJ / cm ² ) is performed. , development, post bake (120 ° C: hot plate / 2 min), etching (commercially available etching solution: phosphoric acid + nitric acid + acetic acid), washing, drying.

Next, an SiO ₂ film is formed as an insulating film for a gate insulating layer, and InGaZnO ₄ (an amorphous state in the embodiment, but an amorphous state in the embodiment) is formed as an oxide semiconductor for an oxide semiconductor layer. A film is formed, and an SiO ₂ film is formed as an insulating film for the inorganic insulating layer.

The film formation of the insulating film for the gate insulating layer is performed by plasma chemical vapor deposition in which a film forming temperature is 350 degrees and a film atmosphere is a mixed gas of SiH ₄ and N ₂ O. The thickness is about 100 nm.

The film formation of the oxide semiconductor film for the oxide semiconductor layer is performed by DC sputtering in which a film formation temperature is set to a room temperature and a film atmosphere is a mixed gas of Ar and O ₂ so that the thickness of the film is about 50nm.

The film formation of the insulating film for the inorganic insulating layer is performed by plasma chemical vapor deposition in which a film forming temperature of 250 ° and a film atmosphere is a mixed gas of SiH ₄ and N ₂ O, and the film thickness is made. It is about 100 nm.

Next, resist patterning is performed by photolithography, and then the insulating film for the inorganic insulating layer is patterned by dry etching in a CHF ₃ gas atmosphere. The resist is then removed using O ₂ plasma. Thereby, an inorganic insulating layer is formed from the insulating film.

Next, resist patterning is performed by photolithography, and then the oxide semiconductor film for the oxide semiconductor layer is patterned by wet etching using an indium tin oxide etchant. The resist is then removed using O ₂ plasma. Thereby, an oxide semiconductor layer is formed from the oxide semiconductor film.

Next, resist patterning is performed by photolithography, and then the insulating film for the gate insulating layer is patterned by dry etching in a CHF ₃ gas atmosphere. The resist is then removed using O ₂ plasma. Thereby, a gate insulating layer is formed from the insulating film.

Next, a Mo film of about 100 nm was formed by DC sputtering as a metal conductive film for the source-drain electrode. After the film formation, the metal conductive film is patterned to form a source-drain electrode, and a metal layer is formed. The patterning is performed in the following order, that is, the positive type photoresist is applied by spin coating, and prebaking (90 ° C: hot plate / 1 min), exposure (about 100 mJ / cm ² ), development, post-baking ( 120 ° C: hot plate / 2 min), etching (commercially available etching solution: phosphoric acid + nitric acid + acetic acid), washing, drying.

The thin film transistor of Example 1 was produced by the above procedure.

(Example 2)

In the second embodiment, a thin film transistor of the same type as the thin film transistor 30 shown in Fig. 2 was produced.

Specifically, the gate electrode, the gate insulating layer, the oxide semiconductor layer, the inorganic insulating layer (part of), the source-drain electrode, and the metal layer (with the source) are formed in the same manner as in the first embodiment. The drain metal electrode simultaneously forms a depleted metal layer).

In the second embodiment, before the inorganic insulating film is patterned, a Mo film is formed as a metal film on the inorganic insulating layer by DC sputtering in advance, and the metal film is also patterned together in the patterning of the inorganic insulating film. Thereby, a part of the inorganic insulating layer and the metal layer (reflective metal layer) are formed. Then, an insulating film (SiO ₂ ) is further formed on the metal layer and on the oxide semiconductor layer, and patterned to form an inorganic insulating layer. The formation of the source-drain electrodes and the worn metal layer is performed after the inorganic insulating layer is completely formed.

The thin film transistor of Example 2 was produced by the above procedure.

(Comparative Example 1)

In Comparative Example 1, when a source-drain electrode was formed, a thin film electric crystal was produced by the same method as the thin film transistor 10 shown in Fig. 1 except that a lossy metal layer was not formed. body.

(assessment)

The operational stability (ΔVth) at the time of light irradiation of the produced thin film transistors of Example 1, Example 2, and Comparative Example 1 was evaluated. Furthermore, the element dimensions of the thin film transistor are 180 μ channel length and 1 mm channel width, respectively.

Each of the thin film transistors was placed in the atmosphere for 1 hour in a dark environment to eliminate the influence of room light in the storage environment of the thin film transistor. Then, each thin film transistor was irradiated with light from the protective layer side in a state where no voltage was applied between the gate electrode and the source-drain electrode (the xenon lamp was 10 μW/cm ² by splitting). A voltage was applied between the gate electrode and the source-drain electrode at a timing of 10 minutes after the irradiation time to measure the Vg-Id characteristic (in this case, the light was continuously irradiated, and the measurement wavelength was between 400 nm and 500 nm and the interval was 20 nm). Thereby, Vth is calculated from the Vg-Id characteristic when the light is not irradiated in advance, and ΔVth at each wavelength is calculated therefrom.

Further, in order to eliminate the influence of light irradiation in each measurement, the Vg-Id characteristic was released in a dark environment until the unexposed light was reproduced, at the end of each measurement (for example, 500 nm). Further, in the measurement of the Vg-Id characteristics, a semiconductor parameter analyzer (manufactured by Agilent Technologies, Inc.) was used.

The calculation results of ΔVth at each wavelength are shown in Table 1 and FIG.

As is apparent from the results shown in Table 1 and FIG. 12, in Comparative Example 1, the film transistor operation was unstable with respect to the light having an irradiation wavelength of 400 nm to 450 nm and |ΔVth| exceeding 1 V. In particular, it is known that |ΔVth| is greatly increased (deteriorated) with respect to light having an irradiation wavelength of 400 nm to 420 nm, and the operation of the thin film transistor is more unstable.

On the other hand, in Example 1 and Example 2, even if light of any wavelength of 400 nm to 450 nm was irradiated, |ΔVth| was less than 1 V, and the operational stability of the thin film transistor was ensured. In particular, even when light having a wavelength of 400 nm to 420 nm is irradiated, |ΔVth| is not drastically increased, and the operational stability of the thin film transistor is further ensured.

10‧‧‧film transistor

12‧‧‧Substrate

14‧‧‧ gate electrode

16‧‧‧ gate insulation

18‧‧‧Oxide semiconductor layer

20‧‧‧Source electrode

22‧‧‧汲electrode

24‧‧‧Protective layer

26‧‧‧Inorganic insulation

28‧‧‧metal layer

Claims (11)

An oxide semiconductor device comprising: an electrode composed of a metal material; an oxide semiconductor layer comprising at least one selected from the group consisting of In, Zn, Ga, and Sn; and a protective layer laminated on the oxide semiconductor layer And the protective layer comprises an inorganic insulating layer and a metal layer composed of the same metal material as the above electrode; and the metal layer is a plurality of layers; the plurality of metal layers comprise: a lossy metal layer disposed on top of the protective layer; The reflective metal layer is disposed inside the inorganic insulating layer, and has a higher reflectance for light having a wavelength of 400 nm or more and 450 nm or less than the worn metal layer. The oxide semiconductor device according to claim 1, wherein the total thickness of the metal layer is 50 nm or more. The oxide semiconductor device according to the first aspect of the invention, wherein the electrode is a source electrode and a germanium which are laminated on the oxide semiconductor layer and can be electrically connected to each other via the oxide semiconductor layer. a pole electrode including a gate electrode disposed via a gate insulating layer on a side opposite to a side of the oxide semiconductor layer on which the protective layer is disposed, wherein at least a portion of the metal layer is formed by the source electrode and the drain electrode The electrodes are made of the same metal material and are disposed on top of the above protective layer. An oxide semiconductor device according to claim 2, wherein The electrode is a source electrode and a drain electrode which are laminated on the oxide semiconductor layer and are electrically connected to each other via the oxide semiconductor layer, and the protective layer is disposed on the oxide semiconductor layer. The opposite side of the one side includes a gate electrode disposed via a gate insulating layer, and at least a portion of the metal layer is made of the same metal material as the source electrode and the gate electrode, and is disposed on top of the protective layer . The oxide semiconductor device according to claim 3, wherein the metal layer is made of the same metal material as the gate electrode. The oxide semiconductor device according to claim 4, wherein the metal layer is made of the same metal material as the gate electrode. The oxide semiconductor device according to claim 1, wherein the inorganic insulating layer comprises a metal material of the metal layer. A method of producing an oxide semiconductor device, comprising: forming an oxide semiconductor layer, wherein the oxide semiconductor layer comprises at least one selected from the group consisting of In, Zn, Ga, and Sn; and the step of forming an electrode, wherein the electrode is made of a metal material And a step of forming a protective layer, wherein the protective layer is laminated on the oxide semiconductor layer, and the protective layer comprises an inorganic insulating layer and a metal layer made of the same metal material as the electrode. The method for producing an oxide semiconductor device according to claim 8, wherein the step of forming the electrode includes: forming a metal conductive film on the inorganic insulating layer and the oxide semiconductor layer; and conducting the metal conductive membrane a step of patterning to form a source electrode and a drain electrode, and in the step of forming the metal layer in the step of forming the protective layer, in the step of forming the electrode, forming the metal conductive film The source electrode and the drain electrode are formed of the metal conductive film in the inorganic insulating layer to form the metal layer. A display device comprising the oxide semiconductor device according to any one of claims 1 to 7. An image sensor comprising the oxide semiconductor device according to any one of claims 1 to 7.