Solid-state secondary batteries

Abstract

To provide an all-solid secondary battery with higher safety than a conventional lithium ion secondary battery including an electrolyte solution, specifically, provide a thin-film type solid secondary battery and a manufacturing method for the same.SOLUTION: As a solid electrolyte, a mixed material obtained by co-evaporation of SiO and an organic complex of lithium is used. That is to say, a solid electrolyte layer formed of a mixed material of an inorganic material and an organic material is used for a solid secondary battery. The ratio of oxygen to silicon in the solid electrolyte layer is more than 1 and less than 2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, a manufacture, or a composition of matter. One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, or an electronic device, or a manufacturing method thereof.

[0002] In this specification, the term "electronic device" refers to any device having a power storage device, and includes electro-optical devices having a power storage device, information terminal devices having a power storage device, and the like. [Background technology]

[0003] 2. Description of the Related Art Electronic devices that are carried by users or worn by users have been actively developed.

[0004] Electronic devices carried by users or worn by users operate using primary or secondary batteries, which are examples of power storage devices, as their power source. It is desirable for electronic devices carried by users to be used for long periods of time, and for this reason, large-capacity secondary batteries are used. However, incorporating a large-capacity secondary battery into an electronic device poses the problem of its large size and weight. Therefore, development is underway to develop small or thin, large-capacity secondary batteries that can be incorporated into portable electronic devices.

[0005] Lithium-ion secondary batteries, which use liquids such as organic solvents as a medium for transporting lithium ions, the carrier ions, are widely used. However, secondary batteries using liquids have problems such as electrolyte decomposition reactions depending on the operating temperature range and operating potential, as well as leakage to the outside of the secondary battery. Furthermore, secondary batteries using liquid electrolytes have the risk of fire due to leakage.

[0006] Fuel cells are a type of secondary battery that does not use liquid, but they are devices that use precious metals for the electrodes and the solid electrolyte material is also expensive.

[0007] Furthermore, a power storage device called a solid-state battery that uses a solid electrolyte as a secondary battery that does not use a liquid is known. For example, Patent Document 1 and Patent Document 2 disclose such a device. Patent Document 3 describes using one of a solvent, a gel, or a solid electrolyte as the electrolyte of a lithium-ion secondary battery.

[0008] Patent Document 1 describes an example in which a lithium cobalt oxide film is formed on a positive electrode current collector by sputtering. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 8,404,001 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-023032 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-229308 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides an all-solid-state secondary battery, specifically a thin-film solid-state secondary battery (also called a thin-film all-solid-state battery), which is safer than conventional lithium-ion secondary batteries that use an electrolyte solution, and a method for producing the same.

[0011] Another challenge is to provide new materials as solid electrolytes for use in thin-film solid secondary batteries.

[0012] Another challenge is to provide an all-solid-state secondary battery suitable as a secondary battery for use in thin electronic devices such as card terminals.

[0013] Another object is to provide an all-solid-state secondary battery suitable for use in a wearable device, specifically a small electronic device in the form of a wristwatch, or a small electronic device in the form of glasses. In particular, in a wearable device, since it may come into contact with the user's skin, it is desirable to use an all-solid-state secondary battery with high safety that does not cause liquid leakage or the like.

Means for Solving the Problems

[0014] One of the configurations disclosed in this specification uses a mixed material obtained by co-evaporation of SiO X (0 < X < 2) and an organic complex of lithium. That is, one of the features of the present invention is to use a solid electrolyte layer composed of a mixed material of an inorganic material and an organic material in a solid secondary battery.

[0015] SiO X The material to be co-evaporated with SiO(0 < X < 2) is either a simple substance of an alkali metal or an alkaline earth metal, an organic complex or a compound, and examples thereof include Li, Li2O, etc. In particular, an organic complex of lithium is preferable, and among them, lithium 8-hydroxyquinolinate (abbreviation: Liq) is preferable.

[0016] One of the configurations related to the manufacturing method disclosed in this specification is a method for manufacturing a solid secondary battery in which a solid electrolyte layer is formed by co-evaporating an organic complex of lithium and SiO X (0 < X < 2) on a positive electrode active material layer or a negative electrode active material layer.

[0017] In the above manufacturing method, since the positive electrode and the negative electrode are formed by sputtering, it is preferable that the positive electrode active material layer or the negative electrode active material layer is formed by sputtering. The sputtering apparatus can also perform continuous film formation using the same chamber or a plurality of chambers, and can be a multi-chamber type manufacturing apparatus or an inline type manufacturing apparatus. The sputtering method is a manufacturing method suitable for mass production using a chamber and a sputtering target. In addition, the sputtering method can form a thin film and has excellent film formation characteristics.

[0018] Furthermore, the method is not particularly limited to sputtering, and the positive electrode active material layer or the negative electrode active material layer can also be formed using a gas phase method (vacuum deposition, thermal spraying, pulsed laser deposition (PLD), ion plating, cold spray, aerosol deposition). The aerosol deposition (AD) method is a method for forming a film without heating the substrate. Aerosol refers to fine particles dispersed in a gas.

[0019] Alternatively, the positive electrode, negative electrode, positive electrode active material layer, or negative electrode active material layer may be formed by using a CVD method or an ALD (Atomic Layer Deposition) method.

[0020] Furthermore, a solid secondary battery can be fabricated by stacking material films obtained by the above-described fabrication method.

[0021] The obtained solid secondary battery also constitutes one aspect of the present invention, and is configured to have a positive electrode, a negative electrode, and a solid electrolyte layer containing silicon, oxygen, lithium, and carbon between the positive electrode and the negative electrode.

[0022] In the above-described configuration, the solid electrolyte layer further contains nitrogen, which is derived from nitrogen contained in the organic complex of lithium.

[0023] In the above-described structure, a negative electrode active material layer containing silicon is provided between the negative electrode and the solid electrolyte layer. The negative electrode active material layer can be formed using a sputtering target containing silicon as a main component.

[0024] In addition, in the above-described structure, a positive electrode active material layer is provided between the positive electrode and the solid electrolyte layer. The positive electrode active material layer can be formed using a sputtering target containing lithium cobalt oxide (LiCoO2) as a main component.

[0025] The ratio of oxygen to silicon (O / Si) in the solid electrolyte layer is greater than 1 and less than 2. That is, the ratio of oxygen to silicon in the solid electrolyte layer is greater than 1 and less than 2. By setting it within such a range, it is possible to realize a solid electrolyte in which lithium ions diffuse easily and there is no electronic conductivity.

[0026] In order to improve the lithium ion conductivity of the solid electrolyte, phosphorus or the like may be further added.

[0027] In this specification, the oxygen ratio of the solid electrolyte layer described above is based on the value obtained by EDX measurement.

[0028] Among EDX measurements, the measurement while scanning within a region and the two-dimensional evaluation of the region are sometimes referred to as EDX surface analysis. Also, from the surface analysis of EDX, the data of a linear region is extracted and the evaluation of the distribution of atomic concentration within the positive electrode active material particles is sometimes referred to as line analysis.

[0029] By EDX surface analysis (for example, elemental mapping), the concentrations of silicon, nitrogen, carbon, and oxygen in the interior or the surface layer portion can be quantitatively analyzed. Also, by EDX line analysis, the peaks of the concentrations of silicon, nitrogen, carbon, and oxygen can be analyzed. The unit of the concentration of EDX is, for example, atomic %.

Advantages of the Invention

[0030] As the solid electrolyte layer, a thin film formed by co-evaporating a lithium organic complex and SiO X (0 < X < 2) enables the manufacture of a thin film type solid secondary battery.

[0031] Since no electrolyte solution is used, the thin film type solid secondary battery has heat resistance to such an extent that it can be used even at high temperatures.

[0032] Also, the thin film type solid secondary battery can be multi-layer laminated by series or parallel connection by increasing the number of laminations with one set of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and the capacity can be increased.

[0033] Furthermore, the capacity of a thin-film solid secondary battery can be increased by increasing the area.

[0034] Furthermore, by using peel-and-transpose technology, it is possible to enlarge the area and then bend it to a desired size. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of the present invention. [Figure 2] 2A and 2B are a top view and a cross-sectional view illustrating one embodiment of the present invention. [Figure 3] FIG. 3 shows EDX data of a solid electrolyte layer showing one embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing one embodiment of the present invention. [Figure 5] FIG. 5 is a production flow diagram showing one embodiment of the present invention. [Figure 6] FIG. 6A is a perspective view showing an example of a battery cell, FIG. 6B is a perspective view of a circuit, and FIG. 6C is a perspective view of the battery cell and the circuit superimposed on each other. [Figure 7] FIG. 7A is a perspective view showing an example of a battery cell, FIG. 7B is a perspective view of a circuit, and FIGS. 7C and 7D are perspective views of the battery cell and the circuit superimposed on each other. [Figure 8] FIG. 8 is a diagram showing a configuration example of a semiconductor device. [Figure 9] FIG. 9 is a diagram showing a configuration example of a semiconductor device. [Figure 10] 10A, 10B, and 10C are diagrams showing configuration examples of a semiconductor device. [Figure 11] FIG. 11A is a perspective view of a battery cell, and FIG. 11B is a diagram showing an example of an electronic device. [Figure 12] 12A, 12B, and 12C are diagrams showing examples of electronic devices. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various modifications can be made to the embodiments and details. Furthermore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0037] 1 shows one embodiment of a single-layer cell of a thin-film solid secondary battery. In this specification, a single-layer cell of a solid secondary battery refers to a unit having at least a positive electrode, a solid electrolyte layer, and a negative electrode.

[0038] The single-layer cell shown in Fig. 1 has a positive electrode 201, a positive electrode active material layer 204, a solid electrolyte layer 202, a negative electrode active material layer 205, and a negative electrode 203 stacked in this order on a substrate 101. Note that the cross-sectional view shown in Fig. 1 is only a partial view, and the positive electrode is arranged so that its planar area is smaller than that of the negative electrode. The edges are rounded, and only one edge is shown in Fig. 1.

[0039] The substrate 101 may be a ceramic substrate, a glass substrate, a plastic substrate, a silicon substrate, a metal substrate, or the like.

[0040] The positive electrode 201 and the negative electrode 203 are made of one or more conductive materials selected from Al, Ti, Cu, Au, Cr, W, Mo, Ni, Ag, etc. Sputtering, vapor deposition, etc. can be used as the film formation method. In the sputtering method, a metal mask can be used to selectively form the film. Alternatively, the conductive film may be patterned by selectively removing the resist mask by dry etching or wet etching.

[0041] The positive electrode active material layer 204 can be formed by sputtering using a sputtering target mainly composed of lithium cobalt oxide (such as LiCoO2, LiCo2O4), a sputtering target mainly composed of lithium manganese oxide (such as LiMnO2, LiMn2O4), or a sputtering target mainly composed of lithium nickel oxide (such as LiNiO2, LiNi2O4). Also, lithium manganese cobalt oxide (such as LiMnCoO4, Li2MnCoO4), a ternary material of nickel cobalt manganese (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2: NCM), a ternary material of nickel cobalt aluminum (LiNi 0.8 Co 0.15 Al 0.05 O2: NCA), etc. can also be used.

[0042] The solid electrolyte layer 202 uses a mixed material of an inorganic material and an organic material. In this embodiment, a mixed material obtained by co-evaporation of SiO X (0 < X < 2) and an organic complex of lithium is used.

[0043] The material co-evaporated with SiO X (0 < X < 2) is either a simple substance of an alkali metal or an alkaline earth metal, an organic complex, or a compound, and examples thereof include Li, Li2O, etc. In particular, an organic complex of lithium is preferable, and among them, lithium 8-hydroxyquinolinate (abbreviation: Liq) is preferable. Other organic materials co-evaporated with SiO X (0 < X < 2) can also use dilithium phthalocyanine (phthalocyanine dilithium), lithium 2-(2-pyridyl)phenolate (abbreviation: Lipp), lithium 2-(2’,2’’-bipyridin-6’-yl)phenolate (abbreviation: Libpp).

[0044] Furthermore, it is preferable to adjust the film formation conditions so that the silicon to oxygen ratio (O / Si) of the resulting solid electrolyte layer 202 is greater than 1 and less than 2. By setting the ratio within this range, it is possible to realize a solid electrolyte layer in which lithium ions are easily diffused and which has no electronic conductivity.

[0045] The solid electrolyte layer 202 may have a laminated structure. In this case, one layer is made of a material in which nitrogen is added to lithium phosphate (Li3PO4) (Li3PO 4-Y N Y It is also possible to laminate a thin film of SiO2 (also called LiPON), where Y>0.

[0046] The negative electrode active material layer 205 can be formed by sputtering or the like using a film mainly composed of silicon, a film mainly composed of carbon, a titanium oxide film, a vanadium oxide film, an indium oxide film, a zinc oxide film, a tin oxide film, a nickel oxide film, or the like. Alternatively, a Li metal film may be used as the negative electrode active material layer 205. Alternatively, lithium titanium oxide (Li4Ti5O 12 , LiTi2O4, etc.) may also be used.

[0047] Since a thin-film solid-state secondary battery is constructed by stacking various films, it is preferable to reduce the interface resistance and internal resistance. It is also preferable to combine films with excellent surface uniformity and adhesion depending on the film they are in contact with.

[0048] Furthermore, the layers can be deposited in any order. An example of a different layer order from that shown in Figure 1 is shown in Figures 2A and 2B. Figure 2A is a top view, and Figure 2B corresponds to a cross-sectional view taken along line AA' in Figure 2A.

[0049] As shown in FIG. 2B, a negative electrode 203 is formed on a substrate 101, and a negative electrode active material layer 205, a solid electrolyte layer 202, a positive electrode active material layer 204, a positive electrode 201, and a protective layer 206 are laminated on the negative electrode 203 in this order.

[0050] These films can be formed using a metal mask. The negative electrode 203, the negative electrode active material layer 205, the positive electrode active material layer 204, the positive electrode 201, and the protective layer 206 can be selectively formed using a sputtering method. Alternatively, the solid electrolyte layer 202 can be selectively formed using a metal mask by co-evaporation. The solid electrolyte layer 202 is formed by co-evaporating Si powder (SiO) and Li powder. A resistance heating source or an electron beam evaporation source is used for the co-evaporation. The material is not limited to Si powder (SiO), and pellet-shaped powder may also be used.

[0051] 2A, a portion of the negative electrode 203 is exposed to form a negative electrode terminal. The area other than the negative electrode terminal is covered with a protective layer 206. Furthermore, a portion of the positive electrode 201 is exposed to form a positive electrode terminal. The area other than the positive electrode terminal is covered with a protective layer 206.

[0052] A silicon nitride film (also called an SiN film) is used as the protective layer 206. The silicon nitride film is formed by sputtering.

[0053] Through the series of steps described above, the thin-film solid secondary battery shown in FIG. 2A can be manufactured.

[0054] Furthermore, in the obtained thin-film solid secondary battery, the concentrations of silicon, nitrogen, carbon, and oxygen inside or on the surface of the solid electrolyte layer 202 can be quantitatively analyzed by using EDX area analysis (e.g., element mapping).

[0055] The solid electrolyte layer 202 was formed and subjected to EDX measurement.

[0056] The EDX spectrum of the cross section of the solid electrolyte layer 202 will be described. In the EDX measurement, an electron beam is irradiated onto the measurement point, and the energy and number of characteristic X-rays generated are measured to obtain the EDX spectrum. The results are shown in Figure 3. The atomic concentration (%) is also shown in Table 1.

[0057] [Table 1]

[0058] From these results, it can be said that the obtained material is a material in which lithium ions easily diffuse and has no electronic conductivity, and can be used as a solid electrolyte.

[0059] The oxygen ratio of the solid electrolyte layer can be calculated based on the value obtained by EDX measurement. The silicon to oxygen ratio (O / Si) of the solid electrolyte layer is greater than 1 and less than 2. By setting the ratio in this range, it is possible to realize a solid electrolyte that allows lithium ions to diffuse easily and has no electronic conductivity.

[0060] Furthermore, the deposition of a solid electrolyte film is not limited to co-evaporation, but can also be performed by simultaneously generating SiO gas and Li gas in the same chamber and cooling these gases on the same deposition surface.

[0061] (Embodiment 2) While an example of a single-layer cell was shown in Embodiment 1, an example of a multi-layer cell is shown in this embodiment. Figures 4 and 5 show one embodiment of a multi-layer cell of a thin-film solid secondary battery.

[0062] FIG. 4 shows an example of a cross section of a three-layer cell.

[0063] A positive electrode 201 is formed on a substrate 101, and a positive electrode active material layer 204, a solid electrolyte layer 202, a negative electrode active material layer 205, and a negative electrode 203 are sequentially formed on the positive electrode 201 to form a first cell.

[0064] Furthermore, a second negative electrode active material layer, a second solid electrolyte layer, a second positive electrode active material layer, and a second positive electrode are sequentially formed on the negative electrode 203 to form a second cell.

[0065] Furthermore, a third positive electrode active material layer, a third solid electrolyte layer, a third negative electrode active material layer, and a third negative electrode are sequentially formed on the second positive electrode layer to form a third cell.

[0066] In Fig. 4, a protective layer 206 is formed last. The three-layer stack shown in Fig. 4 is configured to be connected in series to increase capacity, but it can also be connected in parallel via external wiring. Also, series and parallel or series-parallel can be selected via external wiring.

[0067] It is preferable to use the same material for the solid electrolyte layer 202, the second solid electrolyte layer, and the third solid electrolyte layer, as this reduces manufacturing costs.

[0068] FIG. 5 shows an example of a manufacturing flow for obtaining the structure shown in FIG.

[0069] In Figure 5, to reduce the number of manufacturing steps, an LCO film is used as the positive electrode active material layer, and a titanium film is used as the current collector, with the titanium film considered to be the positive electrode. A silicon film is used as the negative electrode active material layer, and a titanium film is used as the current collector, with the titanium film considered to be the negative electrode. By using the titanium film as the common electrode, a three-layer stacked cell can be realized with a small configuration.

[0070] 6A is an external view of a thin-film solid secondary battery 913. Secondary battery 913 has terminal 951 and terminal 952. Terminal 951 is electrically connected to the positive electrode, and terminal 952 is electrically connected to the negative electrode.

[0071] 6B is an external view of the battery control circuit. The battery control circuit shown in FIG. 6B includes a substrate 900 and a layer 916. A circuit 912 and an antenna 914 are provided over the substrate 900. The antenna 914 is electrically connected to the circuit 912. Terminals 971 and 972 are electrically connected to the circuit 912. The circuit 912 is electrically connected to terminal 911.

[0072] The terminal 911 is connected to, for example, a device to which power is supplied from the thin-film solid secondary battery, such as a display device, a sensor, or the like.

[0073] The layer 916 has a function of shielding, for example, an electromagnetic field generated by the secondary battery 913. The layer 916 can be made of, for example, a magnetic material.

[0074] 6C shows an example in which the battery control circuit shown in FIG. 6B is disposed on a secondary battery 913. Terminal 971 is electrically connected to terminal 951, and terminal 972 is electrically connected to terminal 952. Layer 916 is disposed between substrate 900 and secondary battery 913.

[0075] The substrate 900 is preferably a flexible substrate.

[0076] A thin battery control circuit can be realized by using a flexible substrate as the substrate 900. Furthermore, the battery control circuit can be wrapped around the secondary battery as shown in Fig. 7D, which will be described later.

[0077] 7A is an external view of a thin-film solid-state secondary battery. The battery control circuit shown in FIG.

[0078] As shown in FIG. 7C, by bending the substrate 900 to fit the shape of the secondary battery 913 and arranging the battery control circuit around the secondary battery, the battery control circuit can be wrapped around the secondary battery as shown in FIG. 7D.

[0079] (Embodiment 4) In this embodiment, a structure of a transistor applicable to the battery control circuit described in the above embodiment will be described. Specifically, a structure in which transistors having different electrical characteristics are stacked will be described. This structure can increase the degree of freedom in designing a semiconductor device. In addition, stacking transistors having different electrical characteristics can increase the degree of integration of a semiconductor device.

[0080] 8 includes a transistor 300, a transistor 500, and a capacitor 600. Fig. 10A is a cross-sectional view of the transistor 500 in the channel length direction, Fig. 10B is a cross-sectional view of the transistor 500 in the channel width direction, and Fig. 10C is a cross-sectional view of the transistor 300 in the channel width direction.

[0081] The transistor 500 is an OS transistor. Therefore, the off-state current of the transistor 500 is extremely low. Therefore, by using the transistor 500 as a transistor in a semiconductor device, written data voltage or charge can be held for a long period of time. In other words, refresh operations are performed less frequently or are not required, thereby reducing the power consumption of the semiconductor device.

[0082] 8, the semiconductor device described in this embodiment includes a transistor 300, a transistor 500, and a capacitor 600. The transistor 500 is provided above the transistor 300, and the capacitor 600 is provided above the transistors 300 and 500.

[0083] The transistor 300 is provided on a substrate 311 and includes a conductor 316, an insulator 315, a semiconductor region 313 made of part of the substrate 311, a low-resistance region 314a functioning as a source region or a drain region, and a low-resistance region 314b.

[0084] 10C , the upper surface and the side surfaces in the channel width direction of the semiconductor region 313 of the transistor 300 are covered with a conductor 316 via an insulator 315. By forming the transistor 300 as a fin type in this way, the effective channel width is increased, thereby improving the on-state characteristics of the transistor 300. Furthermore, the contribution of the electric field of the gate electrode can be increased, thereby improving the off-state characteristics of the transistor 300.

[0085] The transistor 300 may be either a p-channel type or an n-channel type.

[0086] The region where the channel of the semiconductor region 313 is formed, the region nearby, the low-resistance region 314a that serves as the source region or drain region, and the low-resistance region 314b preferably contain a semiconductor such as a silicon-based semiconductor, and preferably contain single-crystal silicon. Alternatively, they may be formed of a material containing Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), or the like. A configuration using silicon in which the effective mass is controlled by applying stress to the crystal lattice and changing the lattice spacing may also be used. Alternatively, the transistor 300 may be a HEMT (High Electron Mobility Transistor) by using GaAs and GaAlAs, or the like.

[0087] The low resistance region 314a and the low resistance region 314b contain, in addition to the semiconductor material applied to the semiconductor region 313, an element that imparts n-type conductivity, such as arsenic or phosphorus, or an element that imparts p-type conductivity, such as boron.

[0088] The conductor 316 functioning as the gate electrode can be made of a conductive material such as a semiconductor material, metal material, alloy material, or metal oxide material, such as silicon containing an element that imparts n-type conductivity, such as arsenic or phosphorus, or an element that imparts p-type conductivity, such as boron.

[0089] Since the work function is determined by the material of the conductor, the threshold voltage of the transistor can be adjusted by selecting the material of the conductor. Specifically, it is preferable to use a material such as titanium nitride or tantalum nitride as the conductor. Furthermore, in order to achieve both conductivity and embeddability, it is preferable to use a metal material such as tungsten or aluminum as the conductor in a laminated state, and tungsten is particularly preferable in terms of heat resistance.

[0090] 8 is just an example, and the structure is not limited thereto. An appropriate transistor may be used depending on the circuit configuration and driving method. For example, when the semiconductor device is a unipolar circuit including only OS transistors (meaning transistors with the same polarity, such as only n-channel transistors), the structure of the transistor 300 may be the same as that of the transistor 500 including an oxide semiconductor, as shown in FIG. The details of the transistor 500 will be described later.

[0091] An insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order over the transistor 300.

[0092] The insulators 320, 322, 324, and 326 can be made of, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, or the like.

[0093] In this specification, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen, aluminum oxynitride refers to a material whose composition contains more oxygen than nitrogen, and aluminum nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0094] The insulator 322 may function as a planarizing film that flattens steps caused by the transistor 300 or the like provided thereunder. For example, the top surface of the insulator 322 may be planarized by planarization treatment using a chemical mechanical polishing (CMP) method or the like to improve the flatness.

[0095] The insulator 324 is preferably a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311 or the transistor 300 to a region where the transistor 500 is provided.

[0096] An example of a film having a barrier property against hydrogen is silicon nitride formed by a CVD method. Here, hydrogen diffusion into a semiconductor element having an oxide semiconductor, such as the transistor 500, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 500 and the transistor 300. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0097] The amount of desorption of hydrogen can be analyzed using, for example, thermal desorption spectroscopy (TDS). For example, the amount of desorption of hydrogen from the insulator 324 is calculated as 10×10 per area of ​​the insulator 324 when the surface temperature of the film is in the range of 50° C. to 500° C. in TDS analysis. 15 atoms / cm 2 Less than or equal to 5 x 10 15 atoms / cm 2 The following is fine.

[0098] It is preferable that the insulator 326 has a lower dielectric constant than the insulator 324. For example, the relative dielectric constant of the insulator 326 is preferably less than 4, and more preferably less than 3. Furthermore, for example, the relative dielectric constant of the insulator 326 is preferably 0.7 times or less, and more preferably 0.6 times or less, the relative dielectric constant of the insulator 324. By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance that occurs between wirings can be reduced.

[0099] Furthermore, insulators 320, 322, 324, and 326 are embedded with conductors 328 and 330, which connect to capacitor 600 or transistor 500. Conductors 328 and 330 function as plugs or wiring. Conductors that function as plugs or wiring may be collectively designated by the same reference numeral. In this specification and the like, a wiring and a plug connected to the wiring may be integrated. That is, a portion of a conductor may function as a wiring, and a portion of a conductor may function as a plug.

[0100] The materials for each plug and wiring (conductor 328, conductor 330, etc.) can be a conductive material such as a metal material, an alloy material, a metal nitride material, or a metal oxide material, and can be used in a single layer or a laminated layer. High-melting-point materials such as tungsten and molybdenum, which have both heat resistance and conductivity, are preferably used, and tungsten is preferred. Alternatively, they are preferably formed from a low-resistance conductive material such as aluminum or copper. The use of a low-resistance conductive material can reduce the wiring resistance.

[0101] A wiring layer may be provided over the insulator 326 and the conductor 330. For example, in FIG. 8, the insulator 350, the insulator 352, and the insulator 354 are stacked in this order. The conductor 356 is formed in the insulator 350, the insulator 352, and the insulator 354. The conductor 356 functions as a plug or wiring connected to the transistor 300. Note that the conductor 356 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0102] Note that, for example, the insulator 350 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 356 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 350 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0103] Note that, for example, tantalum nitride or the like is preferably used as the conductor having a barrier property against hydrogen. Stacking tantalum nitride and highly conductive tungsten can suppress diffusion of hydrogen from the transistor 300 while maintaining the conductivity of the wiring. In this case, a structure in which the tantalum nitride layer having a barrier property against hydrogen is in contact with the insulator 350 having a barrier property against hydrogen is preferable.

[0104] A wiring layer may be provided over the insulator 354 and the conductor 356. For example, in FIG. 8, an insulator 360, an insulator 362, and an insulator 364 are stacked in this order. A conductor 366 is formed in the insulator 360, the insulator 362, and the insulator 364. The conductor 366 functions as a plug or a wiring. The conductor 366 can be provided using the same material as the conductors 328 and 330.

[0105] Note that, for example, the insulator 360 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 366 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 360 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0106] A wiring layer may be provided over the insulator 364 and the conductor 366. For example, in FIG. 8, an insulator 370, an insulator 372, and an insulator 374 are stacked in this order. A conductor 376 is formed in the insulator 370, the insulator 372, and the insulator 374. The conductor 376 functions as a plug or a wiring. The conductor 376 can be formed using the same material as the conductors 328 and 330.

[0107] Note that, for example, the insulator 370 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 376 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 370 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0108] A wiring layer may be provided over the insulator 374 and the conductor 376. For example, in FIG. 8, an insulator 380, an insulator 382, ​​and an insulator 384 are stacked in this order. A conductor 386 is formed in the insulator 380, the insulator 382, ​​and the insulator 384. The conductor 386 functions as a plug or a wiring. The conductor 386 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0109] Note that, for example, the insulator 380 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 386 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 380 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0110] Although the above describes a wiring layer including the conductor 356, a wiring layer including the conductor 366, a wiring layer including the conductor 376, and a wiring layer including the conductor 386, the semiconductor device according to this embodiment is not limited to this. There may be three or fewer wiring layers similar to the wiring layer including the conductor 356, or there may be five or more wiring layers similar to the wiring layer including the conductor 356.

[0111] An insulator 510, an insulator 512, an insulator 514, and an insulator 516 are stacked in this order on the insulator 384. Any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516 is preferably made of a substance that has a barrier property against oxygen and hydrogen.

[0112] For example, the insulator 510 and the insulator 514 are preferably formed using a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311 or a region where the transistor 300 is provided to a region where the transistor 500 is provided. Therefore, a material similar to that of the insulator 324 can be used.

[0113] An example of a film having a barrier property against hydrogen is silicon nitride formed by a CVD method. Here, hydrogen diffusion into a semiconductor element having an oxide semiconductor, such as the transistor 500, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 500 and the transistor 300. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0114] As a film having a barrier property against hydrogen, for example, the insulators 510 and 514 are preferably made of a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0115] In particular, aluminum oxide has a high blocking effect against both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0116] For example, the insulator 512 and the insulator 516 can be made of a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, the parasitic capacitance generated between wirings can be reduced. For example, the insulators 512 and 516 can be made of a silicon oxide film or a silicon oxynitride film.

[0117] A conductor 518 and a conductor constituting the transistor 500 (for example, the conductor 503) are embedded in the insulators 510, 512, 514, and 516. The conductor 518 functions as a plug or wiring connected to the capacitor 600 or the transistor 300. The conductor 518 can be formed using a material similar to that of the conductors 328 and 330.

[0118] In particular, the conductor 518 in the region in contact with the insulator 510 and the insulator 514 is preferably a conductor having a barrier property against oxygen, hydrogen, and water. With this structure, the transistor 300 and the transistor 500 can be separated by a layer having a barrier property against oxygen, hydrogen, and water, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0119] Above the insulator 516 is the transistor 500 .

[0120] As shown in Figures 10A and 10B, transistor 500 has conductor 503 arranged so as to be embedded in insulator 514 and insulator 516, insulator 520 arranged on insulator 516 and conductor 503, insulator 522 arranged on insulator 520, insulator 524 arranged on insulator 522, oxide 530a arranged on insulator 524, oxide 530b arranged on oxide 530a, conductors 542a and 542b arranged spaced apart from each other on oxide 530b, insulator 580 arranged on conductors 542a and 542b and having an opening formed therebetween overlapping conductors 542a and 542b, oxide 530c arranged on the bottom and side surfaces of the opening, insulator 550 arranged on the surface on which oxide 530c is formed, and conductor 560 arranged on the surface on which insulator 550 is formed.

[0121] 10A and 10B, it is preferable that insulator 544 be disposed between oxide 530a, oxide 530b, conductor 542a, and conductor 542b and insulator 580. It is preferable that conductor 560 include conductor 560a disposed inside insulator 550 and conductor 560b disposed so as to be embedded inside conductor 560a. It is preferable that insulator 574 be disposed on insulator 580, conductor 560, and insulator 550, as shown in FIGS.

[0122] In this specification and other documents, oxide 530a, oxide 530b, and oxide 530c may be collectively referred to as oxide 530.

[0123] Although the transistor 500 has a three-layer structure of oxides 530a, 530b, and 530c in and around the channel formation region, the present invention is not limited to this structure. For example, the transistor may have a single layer of oxide 530b, a two-layer structure of oxides 530b and 530a, a two-layer structure of oxides 530b and 530c, or a stacked structure of four or more layers. Although the transistor 500 has a two-layer structure, the present invention is not limited to this structure. For example, the conductor 560 may have a single-layer structure or a stacked structure of three or more layers. The transistor 500 shown in FIGS. 8 and 10A is merely an example, and the present invention is not limited to this structure. An appropriate transistor may be used depending on the circuit configuration and driving method.

[0124] Here, the conductor 560 functions as the gate electrode of the transistor, and the conductors 542a and 542b function as the source and drain electrodes, respectively. As described above, the conductor 560 is formed so as to be embedded in the opening of the insulator 580 and in the region sandwiched between the conductors 542a and 542b. The arrangement of the conductors 560, 542a, and 542b is selected in a self-aligned manner with respect to the opening of the insulator 580. That is, in the transistor 500, the gate electrode can be positioned between the source and drain electrodes in a self-aligned manner. Therefore, the conductor 560 can be formed without providing a margin for alignment, thereby reducing the area occupied by the transistor 500. This allows for miniaturization and high integration of semiconductor devices.

[0125] Furthermore, since the conductor 560 is formed in a self-aligned manner in the region between the conductor 542a and the conductor 542b, the conductor 560 does not have a region that overlaps with the conductor 542a or the conductor 542b. This reduces the parasitic capacitance formed between the conductor 560 and the conductor 542a and between the conductor 560 and the conductor 542b. This improves the switching speed of the transistor 500 and provides high frequency characteristics.

[0126] The conductor 560 may function as a first gate (also referred to as a top gate) electrode. The conductor 503 may function as a second gate (also referred to as a bottom gate) electrode. In this case, the threshold voltage of the transistor 500 can be controlled by changing the potential applied to the conductor 503 independently of the potential applied to the conductor 560. In particular, applying a negative potential to the conductor 503 can increase the threshold voltage of the transistor 500 above 0 V and reduce the off-state current. Therefore, applying a negative potential to the conductor 503 can reduce the drain current when the potential applied to the conductor 560 is 0 V compared to when a negative potential is not applied.

[0127] The conductor 503 is arranged to overlap the oxide 530 and the conductor 560. In this way, when a potential is applied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected, and a channel formation region formed in the oxide 530 can be covered.

[0128] In this specification, a transistor structure in which a channel formation region is electrically surrounded by the electric field of a pair of gate electrodes (a first gate electrode and a second gate electrode) is referred to as a surrounded channel (S-channel) structure. In this specification, the surrounded channel (S-channel) structure is characterized in that the side and periphery of the oxide 530 in contact with the conductors 542a and 542b, which function as source and drain electrodes, are I-type, just like the channel formation region. Furthermore, the side and periphery of the oxide 530 in contact with the conductors 542a and 542b can be I-type, just like the channel formation region, because they are in contact with the insulator 544. In this specification, I-type can be considered to be the same as high-purity intrinsic oxide, as described later. The S-channel structure disclosed in this specification differs from a fin structure and a planar structure. The S-channel structure enhances resistance to the short-channel effect, or in other words, makes the transistor less susceptible to the short-channel effect.

[0129] The conductor 503 has a structure similar to that of the conductor 518, in which the conductor 503a is formed in contact with the inner walls of the openings of the insulators 514 and 516, and the conductor 503b is formed further inside. Note that although the transistor 500 has a structure in which the conductors 503a and 503b are stacked, the present invention is not limited to this. For example, the conductor 503 may have a single layer or a stacked structure of three or more layers.

[0130] Here, the conductor 503a is preferably made of a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (the impurities are less likely to permeate). Alternatively, it is preferably made of a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (the oxygen is less likely to permeate). In this specification, the function of suppressing the diffusion of impurities or oxygen refers to the function of suppressing the diffusion of any one or all of the impurities and oxygen.

[0131] For example, the conductor 503a has a function of suppressing the diffusion of oxygen, so that the conductor 503b can be prevented from being oxidized and its conductivity from decreasing.

[0132] Furthermore, when the conductor 503 also functions as a wiring, it is preferable that the conductor 503b be made of a highly conductive material containing tungsten, copper, or aluminum as a main component. Note that, although the conductor 503 is illustrated in this embodiment as a stack of the conductors 503a and 503b, the conductor 503 may have a single-layer structure.

[0133] The insulators 520, 522, and 524 function as a second gate insulating film.

[0134] Here, it is preferable that the insulator 524 in contact with the oxide 530 contains more oxygen than the oxygen required for the stoichiometric composition. In other words, it is preferable that an excess oxygen region is formed in the insulator 524. By providing an insulator containing such excess oxygen in contact with the oxide 530, oxygen vacancies (V O When hydrogen enters the oxygen vacancy in the oxide 530, the defect (hereinafter referred to as V O H.) functions as a donor and may generate electrons as carriers. In addition, some of the hydrogen may bond with oxygen that is bonded to a metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing a large amount of hydrogen is likely to have normally-on characteristics. Furthermore, hydrogen in an oxide semiconductor is easily moved by stress such as heat or an electric field. Therefore, if an oxide semiconductor contains a large amount of hydrogen, the reliability of the transistor may be reduced. In one embodiment of the present invention, V in the oxide 530 O It is preferable to reduce H as much as possible to obtain high-purity intrinsic or substantially high-purity intrinsic V. OTo obtain an oxide semiconductor with a sufficiently reduced amount of H, it is important to remove impurities such as moisture and hydrogen from the oxide semiconductor (sometimes referred to as dehydration or dehydrogenation treatment) and to supply oxygen to the oxide semiconductor to fill oxygen vacancies (sometimes referred to as oxygen addition treatment). O When an oxide semiconductor in which impurities such as H are sufficiently reduced is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0135] Specifically, it is preferable to use an oxide material from which a portion of oxygen is released by heating as an insulator having an excess oxygen region. The oxide material from which oxygen is released by heating is an oxide material from which the amount of released oxygen converted to oxygen atoms is 1.0 × 10 in TDS (Thermal Desorption Spectroscopy) analysis. 18 atoms / cm 3 or more, preferably 1.0 × 10 19 atoms / cm 3 More preferably, 2.0 × 10 19 atoms / cm 3 or more, or 3.0 x 10 20 atoms / cm 3 The oxide film is one having the above properties. The surface temperature of the film during the TDS analysis is preferably in the range of 100°C or higher and 700°C or lower, or 100°C or higher and 400°C or lower.

[0136] Alternatively, the oxide 530 may be brought into contact with the insulator having the excess oxygen region and subjected to one or more of heat treatment, microwave treatment, and RF treatment. By performing such treatment, water or hydrogen in the oxide 530 can be removed. For example, a reaction occurs in the oxide 530 that breaks the VOH bond, in other words, "V O The reaction "H → Vo + H" occurs, resulting in dehydrogenation. Some of the generated hydrogen may combine with oxygen to form HO, which may be removed from the oxide 530 or an insulator near the oxide 530. Some of the hydrogen may also be gettered to the conductor 542.

[0137] The microwave treatment is preferably performed using, for example, an apparatus having a power source for generating high-density plasma or an apparatus having a power source for applying RF to the substrate side. For example, high-density oxygen radicals can be generated by using an oxygen-containing gas and high-density plasma, and the oxygen radicals generated by the high-density plasma can be efficiently introduced into the oxide 530 or an insulator near the oxide 530 by applying RF to the substrate side. The microwave treatment is performed at a pressure of 133 Pa or higher, preferably 200 Pa or higher, and more preferably 400 Pa or higher. The gases introduced into the microwave treatment apparatus may be, for example, oxygen and argon, with an oxygen flow ratio (O2 / (O2+Ar)) of 50% or less, preferably 10% to 30%.

[0138] During the manufacturing process of the transistor 500, heat treatment is preferably performed with the surface of the oxide 530 exposed. The heat treatment may be performed, for example, at a temperature of 100° C. to 450° C., more preferably 350° C. to 400° C. Note that the heat treatment is performed in a nitrogen gas or inert gas atmosphere, or an atmosphere containing an oxidizing gas at 10 ppm or more, 1% or more, or 10% or more. For example, the heat treatment is preferably performed in an oxygen atmosphere. This supplies oxygen to the oxide 530, thereby eliminating oxygen vacancies (V O ) can be reduced. The heat treatment may be performed under reduced pressure. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas after the heat treatment in a nitrogen gas or inert gas atmosphere to compensate for the desorbed oxygen. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas, and then the heat treatment may be performed in a nitrogen gas or inert gas atmosphere.

[0139] By subjecting the oxide 530 to oxygen addition treatment, the oxygen vacancies in the oxide 530 can be repaired by the supplied oxygen, in other words, the reaction "Vo + O → null" can be promoted. Furthermore, the supplied oxygen reacts with the hydrogen remaining in the oxide 530, and the hydrogen can be removed as H2O (dehydration). As a result, the hydrogen remaining in the oxide 530 recombines with the oxygen vacancies to form V O The formation of H can be suppressed.

[0140] When the insulator 524 has an excess oxygen region, the insulator 522 preferably has a function of suppressing the diffusion of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (preferably making the oxygen less permeable).

[0141] The insulator 522 preferably has a function of suppressing diffusion of oxygen and impurities, which prevents oxygen contained in the oxide 530 from diffusing toward the insulator 520. Furthermore, reaction of the conductor 503 with oxygen contained in the insulator 524 or the oxide 530 can be suppressed.

[0142] The insulator 522 is preferably a single-layer or multi-layer insulator containing a high-k material, such as aluminum oxide, hafnium oxide, oxide containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As transistors become smaller and more highly integrated, thinner gate insulating films can cause problems such as leakage current. Using a high-k material for the insulator that functions as the gate insulating film allows for a reduction in the gate potential during transistor operation while maintaining the physical film thickness.

[0143] In particular, an insulator containing an oxide of one or both of aluminum and hafnium, which is an insulating material that has the function of suppressing the diffusion of impurities and oxygen (i.e., is difficult for oxygen to permeate), is preferably used. As an insulator containing an oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used. When the insulator 522 is formed using such a material, the insulator 522 functions as a layer that suppresses oxygen release from the oxide 530 and the intrusion of impurities such as hydrogen into the oxide 530 from the periphery of the transistor 500.

[0144] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the above insulators.

[0145] Furthermore, it is preferable that the insulator 520 be thermally stable. For example, silicon oxide and silicon oxynitride are suitable because they are thermally stable. Furthermore, by combining a high-k insulator with silicon oxide or silicon oxynitride, it is possible to obtain the insulator 520 having a thermally stable layered structure with a high dielectric constant.

[0146] The transistor 500 preferably uses a metal oxide functioning as an oxide semiconductor for the oxide 530 including the channel formation region. For example, a metal oxide such as In-M-Zn oxide (wherein the element M is one or more elements selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used as the oxide 530. In particular, the In-M-Zn oxide applicable to the oxide 530 is preferably a c-axis aligned crystalline oxide semiconductor (CAAC-OS). Alternatively, it is preferably a cloud-aligned composite oxide semiconductor (CAC-OS). Note that CAAC represents an example of a crystal structure, and CAC represents an example of a function or material configuration. Alternatively, an In-Ga oxide or an In-Zn oxide may be used as the oxide 530.

[0147] CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and the material as a whole functions as a semiconductor. When CAC-OS or CAC-metal oxide is used in the active layer of a transistor, the conductive function is a function of allowing electrons (or holes) to flow as carriers, and the insulating function is a function of preventing the flow of electrons as carriers. By making the conductive function and the insulating function act complementarily, a switching function (on / off function) can be imparted to CAC-OS or CAC-metal oxide. By separating the respective functions in CAC-OS or CAC-metal oxide, both functions can be maximized.

[0148] Furthermore, CAC-OS or CAC-metal oxide has conductive regions and insulating regions. The conductive regions have the above-mentioned conductive function, and the insulating regions have the above-mentioned insulating function. In addition, the conductive regions and the insulating regions may be separated at the nanoparticle level in the material. In addition, the conductive regions and the insulating regions may be unevenly distributed in the material. In addition, the conductive regions may be observed as connected in a cloud-like shape with the periphery blurred.

[0149] In addition, in CAC-OS or CAC-metal oxide, the conductive regions and the insulating regions may be dispersed in the material with sizes of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm.

[0150] Furthermore, the CAC-OS or CAC-metal oxide is composed of components with different band gaps. For example, the CAC-OS or CAC-metal oxide is composed of a component with a wide gap due to an insulating region and a component with a narrow gap due to a conductive region. In this configuration, when carriers flow, the carriers mainly flow in the component with the narrow gap. Furthermore, the component with the narrow gap acts complementarily with the component with the wide gap, and carriers also flow in the component with the wide gap in conjunction with the component with the narrow gap. Therefore, when the CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, the transistor can achieve high current driving power in the on state, i.e., a large on-state current, and high field-effect mobility.

[0151] That is, CAC-OS or CAC-metal oxide can also be called a matrix composite or a metal matrix composite.

[0152] Metal oxides that function as oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors, such as CAAC-OS, polycrystalline oxide semiconductors, nanocrystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0153] IGZO is broadly classified into Amorphous, Crystalline, and Crystal. Amorphous also includes completely amorphous. Crystalline includes c-axis aligned crystalline (CAAC), nanocrystalline (nc), and Cloud-Aligned Composite (CAC). Crystalline excludes single crystal, polycrystal, and completely amorphous. Crystal includes single crystal and polycrystal.

[0154] CAAC-OS has a c-axis orientation and a distorted crystal structure in which multiple nanocrystals are connected in the ab-plane direction. The distorted crystal structure refers to the change in the lattice orientation between regions with a uniform lattice arrangement and regions with a different uniform lattice arrangement in the regions where multiple nanocrystals are connected.

[0155] Nanocrystals are basically hexagonal, but not necessarily regular hexagons; they can also have non-regular hexagonal shapes. Furthermore, the lattice arrangement of CAAC-OS can be pentagonal, heptagonal, or other shapes due to distortion. It is difficult to identify clear grain boundaries in CAAC-OS, even near the distortion. This indicates that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is because CAAC-OS can tolerate distortion due to the lack of close-packed arrangement of oxygen atoms in the ab-plane direction and the change in interatomic bond distance caused by substitution of metal elements.

[0156] CAAC-OS also tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter referred to as an In layer) and a layer containing the element M, zinc, and oxygen (hereinafter referred to as an (M,Zn) layer) are stacked. Note that indium and the element M are mutually substituted, and when the element M in an (M,Zn) layer is substituted with indium, it can also be expressed as an (In,M,Zn) layer. When the indium in an In layer is substituted with the element M, it can also be expressed as an (In,M) layer.

[0157] CAAC-OS is a metal oxide with high crystallinity. Because it is difficult to identify clear grain boundaries in CAAC-OS, it is unlikely that the electron mobility will decrease due to grain boundaries. Furthermore, because the crystallinity of metal oxides can be reduced by the incorporation of impurities or the generation of defects, CAAC-OS can be considered a metal oxide with few impurities or defects (such as oxygen vacancies). Therefore, metal oxides with CAAC-OS have stable physical properties. Therefore, metal oxides with CAAC-OS are heat-resistant and highly reliable.

[0158] The nc-OS has periodic atomic arrangement in a small region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). Furthermore, the nc-OS exhibits no regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is observed throughout the film. Therefore, depending on the analytical method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor.

[0159] In-Ga-Zn oxide (also known as "IGZO"), a type of metal oxide containing indium, gallium, and zinc, can sometimes have a stable structure when made into the above-mentioned nanocrystals. In particular, since IGZO tends to have difficulty growing crystals in the atmosphere, it may be structurally more stable when made into smaller crystals (for example, the above-mentioned nanocrystals) than larger crystals (here, crystals of a few millimeters or a few centimeters).

[0160] The a-like OS is a metal oxide having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has pores or low-density regions. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS.

[0161] Oxide semiconductors (metal oxides) have a variety of structures, each with different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[0162] Furthermore, it is preferable to use a metal oxide with a low carrier concentration for the transistor 500. To lower the carrier concentration of a metal oxide, the impurity concentration in the metal oxide should be lowered to lower the density of defect states. In this specification and the like, a low impurity concentration and a low density of defect states are referred to as high-purity intrinsic or substantially high-purity intrinsic. Examples of impurities in metal oxides include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0163] In particular, hydrogen contained in metal oxide reacts with oxygen bonded to metal atoms to form water, which can form oxygen vacancies in the metal oxide. If oxygen vacancies are present in the channel formation region of a metal oxide, the transistor may exhibit normally-on characteristics. Furthermore, defects in which hydrogen has entered the oxygen vacancies can function as donors, generating electrons as carriers. Furthermore, some of the hydrogen may bond with oxygen bonded to metal atoms to generate electrons as carriers. Therefore, transistors using metal oxides containing a large amount of hydrogen tend to exhibit normally-on characteristics.

[0164] Defects in which hydrogen has entered oxygen vacancies can function as donors in metal oxides. However, it is difficult to quantitatively evaluate such defects. Therefore, metal oxides are sometimes evaluated using carrier concentration rather than donor concentration. Therefore, in this specification and the like, the carrier concentration assuming a state in which no electric field is applied may be used as a parameter of metal oxides, rather than donor concentration. In other words, the "carrier concentration" described in this specification and the like may sometimes be rephrased as "donor concentration."

[0165] Therefore, when a metal oxide is used for the oxide 530, it is preferable that the hydrogen in the metal oxide is reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is set to 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5 × 10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 By using a metal oxide in which impurities such as hydrogen are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0166] When a metal oxide is used for the oxide 530, the carrier concentration of the metal oxide in the channel formation region is 1×10 18 cm -3 Preferably, it is 1×10 or less. 17 cm -3 More preferably, it is less than 1×10 16 cm -3 More preferably, it is less than 1×10 13 cm -3 More preferably, it is less than 1×10 12 cm -3 The lower limit of the carrier concentration of the metal oxide in the channel formation region is not particularly limited, but is preferably, for example, 1×10 -9 cm -3 It can be said that:

[0167] Furthermore, when a metal oxide is used for the oxide 530, contact between the conductor 542 (conductor 542a and conductor 542b) and the oxide 530 may cause oxygen in the oxide 530 to diffuse into the conductor 542, resulting in the oxidation of the conductor 542. The oxidation of the conductor 542 is likely to result in a decrease in the conductivity of the conductor 542. The diffusion of oxygen in the oxide 530 into the conductor 542 can be rephrased as the conductor 542 absorbing the oxygen in the oxide 530.

[0168] Furthermore, oxygen in the oxide 530 diffuses into the conductor 542 (conductor 542a and conductor 542b), which may form a heterogeneous layer between the conductor 542a and the oxide 530b and between the conductor 542b and the oxide 530b. Since the heterogeneous layer contains more oxygen than the conductor 542, it is presumed that the heterogeneous layer has insulating properties. In this case, the three-layer structure of the conductor 542, the heterogeneous layer, and the oxide 530b can be regarded as a three-layer structure consisting of a metal, an insulator, and a semiconductor, and may be called a metal-insulator-semiconductor (MIS) structure or a diode junction structure mainly based on the MIS structure.

[0169] It should be noted that the above-mentioned different layer is not limited to being formed between the conductor 542 and the oxide 530b, and for example, the different layer may be formed between the conductor 542 and the oxide 530c, between the conductor 542 and the oxide 530b, and between the conductor 542 and the oxide 530c.

[0170] The metal oxide that functions as a channel formation region in the oxide 530 preferably has a band gap of 2 eV or more, preferably 2.5 eV or more. By using a metal oxide with a wide band gap, the off-state current of the transistor can be reduced.

[0171] The oxide 530 has the oxide 530a below the oxide 530b, which can prevent impurities from diffusing from structures formed below the oxide 530a to the oxide 530b. Also, the oxide 530 has the oxide 530c on the oxide 530b, which can prevent impurities from diffusing from structures formed above the oxide 530c to the oxide 530b.

[0172] The oxide 530 preferably has a stacked structure of multiple oxide layers with different atomic ratios of the metal atoms. Specifically, the atomic ratio of the element M among the constituent elements in the metal oxide used for the oxide 530a is preferably greater than the atomic ratio of the element M among the constituent elements in the metal oxide used for the oxide 530b. The atomic ratio of the element M to In in the metal oxide used for the oxide 530a is preferably greater than the atomic ratio of the element M to In in the metal oxide used for the oxide 530b. The atomic ratio of In to M in the metal oxide used for the oxide 530b is preferably greater than the atomic ratio of In to M in the metal oxide used for the oxide 530a. The oxide 530c can be the same metal oxide as that used for the oxide 530a or the oxide 530b.

[0173] The oxides 530a and 530c preferably have a conduction band minimum energy higher than that of the oxide 530b, and the oxides 530a and 530c preferably have a lower electron affinity than that of the oxide 530b.

[0174] Here, the energy level of the conduction band minimum changes smoothly at the junction between the oxides 530a, 530b, and 530c. In other words, the energy level of the conduction band minimum at the junction between the oxides 530a, 530b, and 530c changes continuously or forms a continuous junction. To achieve this, it is preferable to reduce the defect level density of the mixed layers formed at the interface between the oxides 530a and 530b and at the interface between the oxides 530b and 530c.

[0175] Specifically, when the oxides 530a and 530b, and the oxides 530b and 530c, contain a common element (main component) other than oxygen, a mixed layer with a low density of defect states can be formed. For example, when the oxide 530b is an In-Ga-Zn oxide, the oxides 530a and 530c may be made of an In-Ga-Zn oxide, a Ga-Zn oxide, or a gallium oxide.

[0176] In this case, the oxide 530b serves as the main carrier path. By configuring the oxide 530a and the oxide 530c as described above, the defect state density at the interface between the oxide 530a and the oxide 530b and at the interface between the oxide 530b and the oxide 530c can be reduced. This reduces the effect of interface scattering on carrier conduction, allowing the transistor 500 to obtain a high on-state current.

[0177] Conductors 542a and 542b, which function as a source electrode and a drain electrode, are provided on oxide 530b. Conductors 542a and 542b are preferably made of a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, or an alloy containing any of the above metal elements or an alloy combining any of the above metal elements. For example, tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel is preferably used. In addition, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred because they are conductive materials that are resistant to oxidation or materials that maintain conductivity even when absorbing oxygen.Furthermore, metal nitride films such as tantalum nitride are preferred because they have barrier properties against hydrogen or oxygen.

[0178] 10, the conductors 542a and 542b are shown as single-layer structures, but they may also be stacked with two or more layers. For example, a tantalum nitride film and a tungsten film may be stacked. Alternatively, a titanium film and an aluminum film may be stacked. Alternatively, a two-layer structure in which an aluminum film is stacked on a tungsten film, a two-layer structure in which a copper film is stacked on a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is stacked on a titanium film, or a two-layer structure in which a copper film is stacked on a tungsten film may be used.

[0179] Other examples include a three-layer structure in which a titanium film or titanium nitride film is laminated on the titanium film or titanium nitride film, an aluminum film or copper film is laminated on the titanium film or titanium nitride film, and a titanium film or titanium nitride film is further formed thereon, and a three-layer structure in which a molybdenum film or molybdenum nitride film is laminated on the molybdenum film or molybdenum nitride film, an aluminum film or copper film is laminated on the molybdenum film or molybdenum nitride film, and a molybdenum film or molybdenum nitride film is further formed thereon. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may also be used.

[0180] 10A, regions 543a and 543b may be formed as low-resistance regions at and near the interface of the oxide 530 with the conductor 542a (conductor 542b). In this case, the region 543a functions as either a source region or a drain region, and the region 543b functions as the other. A channel formation region is formed in the region sandwiched between the regions 543a and 543b.

[0181] By providing the conductor 542a (conductor 542b) so as to be in contact with the oxide 530, the oxygen concentration in the region 543a (region 543b) may be reduced. Also, a metal compound layer containing the metal contained in the conductor 542a (conductor 542b) and components of the oxide 530 may be formed in the region 543a (region 543b). In such a case, the carrier density in the region 543a (region 543b) increases, and the region 543a (region 543b) becomes a low-resistance region.

[0182] The insulator 544 is provided to cover the conductors 542a and 542b and suppresses oxidation of the conductors 542a and 542b. In this case, the insulator 544 may be provided to cover the side surface of the oxide 530 and to be in contact with the insulator 524.

[0183] The insulator 544 can be a metal oxide containing one or more elements selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, magnesium, etc. Alternatively, the insulator 544 can be silicon nitride oxide, silicon nitride, or the like.

[0184] In particular, it is preferable to use, as the insulator 544, an insulator containing an oxide of either or both of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate). Hafnium aluminate is particularly preferable because it has higher heat resistance than hafnium oxide film. Therefore, it is less likely to crystallize during heat treatment in a later process. Note that if the conductors 542a and 542b are made of oxidation-resistant materials or if their conductivity does not decrease significantly even when they absorb oxygen, the insulator 544 is not an essential component. It can be designed appropriately depending on the desired transistor characteristics.

[0185] The insulator 544 can prevent impurities such as water and hydrogen contained in the insulator 580 from diffusing to the oxide 530b through the oxide 530c and the insulator 550. The insulator 544 can also prevent the conductor 560 from being oxidized by excess oxygen contained in the insulator 580.

[0186] The insulator 550 functions as a first gate insulating film. The insulator 550 is preferably disposed in contact with the inside (top surface and side surface) of the oxide 530c. The insulator 550 is preferably formed using an insulator that contains excess oxygen and releases oxygen by heating, similar to the insulator 524 described above.

[0187] Specifically, silicon oxide having excess oxygen, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and silicon oxide having vacancies can be used. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

[0188] By providing the insulator 550, which releases oxygen upon heating, in contact with the top surface of the oxide 530c, oxygen can be effectively supplied from the insulator 550 to the channel formation region of the oxide 530b through the oxide 530c. Similarly to the insulator 524, the insulator 550 preferably has a low concentration of impurities such as water or hydrogen. The thickness of the insulator 550 is preferably 1 nm to 20 nm.

[0189] Furthermore, a metal oxide may be provided between the insulator 550 and the conductor 560 to efficiently supply excess oxygen contained in the insulator 550 to the oxide 530. The metal oxide preferably suppresses oxygen diffusion from the insulator 550 to the conductor 560. By providing a metal oxide that suppresses oxygen diffusion, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. In other words, a decrease in the amount of excess oxygen supplied to the oxide 530 can be suppressed. Furthermore, oxidation of the conductor 560 due to excess oxygen can be suppressed. As the metal oxide, a material that can be used for the insulator 544 may be used.

[0190] The insulator 550 may have a layered structure, similar to the second gate insulating film. As transistors become smaller and more highly integrated, thinner gate insulating films can cause problems such as leakage current. Therefore, by using a layered structure of a high-k material and a thermally stable material for the insulator that functions as the gate insulating film, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. Furthermore, a layered structure that is thermally stable and has a high dielectric constant can be achieved.

[0191] The conductor 560 functioning as the first gate electrode is shown as having a two-layer structure in FIGS. 10A and 10B, but may have a single-layer structure or a stacked structure of three or more layers.

[0192] The conductor 560a is preferably made of a conductive material that suppresses the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (e.g., NO, NO, and the like), and copper atoms. Alternatively, a conductive material that suppresses the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, and the like) is preferably used. The oxygen-suppressing function of the conductor 560a can suppress the oxidation of the conductor 560b due to oxygen contained in the insulator 550, which can reduce the conductivity. Examples of conductive materials that suppress the diffusion of oxygen include tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Alternatively, an oxide semiconductor that can be used for the oxide 530 can be used as the conductor 560a. In this case, the conductor 560b can be formed by sputtering to reduce the electrical resistance of the conductor 560a, thereby making it a conductor. This can be called an OC (Oxide Conductor) electrode.

[0193] The conductor 560b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. Since the conductor 560b also functions as wiring, it is preferable to use a conductor with high conductivity. For example, a conductive material containing tungsten, copper, or aluminum as a main component can be used. The conductor 560b may have a layered structure, such as a layered structure of titanium or titanium nitride and the above conductive material.

[0194] The insulator 580 is provided over the conductor 542a and the conductor 542b with the insulator 544 interposed therebetween. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 preferably includes silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, silicon oxide having voids, or a resin. Silicon oxide and silicon oxynitride are particularly preferred because they are thermally stable. Silicon oxide and silicon oxide having voids are particularly preferred because they allow for easy formation of an excess oxygen region in a later step.

[0195] The insulator 580 preferably has an excess oxygen region. By providing the insulator 580, from which oxygen is released by heating, in contact with the oxide 530c, oxygen in the insulator 580 can be efficiently supplied to the oxide 530 through the oxide 530c. Note that the concentration of impurities such as water or hydrogen in the insulator 580 is preferably reduced.

[0196] The opening of the insulator 580 is formed to overlap the region between the conductor 542a and the conductor 542b, so that the conductor 560 is formed to be embedded in the opening of the insulator 580 and the region sandwiched between the conductor 542a and the conductor 542b.

[0197] When miniaturizing semiconductor devices, it is necessary to shorten the gate length, but it is also necessary to prevent the conductivity of the conductor 560 from decreasing. If the film thickness of the conductor 560 is increased to achieve this, the conductor 560 may have a shape with a high aspect ratio. In this embodiment, the conductor 560 is provided so as to be embedded in the opening of the insulator 580. Therefore, even if the conductor 560 has a shape with a high aspect ratio, the conductor 560 can be formed without collapsing during the process.

[0198] The insulator 574 is preferably provided in contact with the top surface of the insulator 580, the top surface of the conductor 560, and the top surface of the insulator 550. By forming the insulator 574 by a sputtering method, an excess oxygen region can be provided in the insulator 550 and the insulator 580. This allows oxygen to be supplied from the excess oxygen region into the oxide 530.

[0199] For example, the insulator 574 can be a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like.

[0200] In particular, aluminum oxide has high barrier properties and can suppress the diffusion of hydrogen and nitrogen even when it is a thin film with a thickness of 0.5 nm to 3.0 nm. Therefore, aluminum oxide formed by sputtering can function as both an oxygen source and a barrier film against impurities such as hydrogen.

[0201] An insulator 581 functioning as an interlayer film is preferably provided over the insulator 574. Like the insulator 524, the insulator 581 preferably has a reduced concentration of impurities such as water or hydrogen.

[0202] Furthermore, conductors 540a and 540b are arranged in openings formed in insulators 581, 574, 580, and 544. Conductor 540a and 540b are arranged opposite each other with conductor 560 interposed therebetween. Conductor 540a and 540b have the same configuration as conductors 546 and 548, which will be described later.

[0203] An insulator 582 is provided over the insulator 581. The insulator 582 is preferably formed using a substance that has a barrier property against oxygen and hydrogen. Therefore, the insulator 582 can be formed using a material similar to that of the insulator 514. For example, the insulator 582 is preferably formed using a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0204] In particular, aluminum oxide has a high blocking effect against both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0205] An insulator 586 is provided over the insulator 582. The insulator 586 can be formed using a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, parasitic capacitance between wirings can be reduced. For example, a silicon oxide film, a silicon oxynitride film, or the like can be used as the insulator 586.

[0206] Furthermore, conductors 546, 548, etc. are embedded in insulators 520, 522, 524, 544, 580, 574, 581, 582, and 586.

[0207] The conductor 546 and the conductor 548 function as plugs or wirings that connect to the capacitor 600, the transistor 500, or the transistor 300. The conductor 546 and the conductor 548 can be formed using the same materials as the conductor 328 and the conductor 330.

[0208] After the transistor 500 is formed, an opening may be formed to surround the transistor 500, and an insulator with high barrier properties against hydrogen or water may be formed to cover the opening. By surrounding the transistor 500 with the insulator with high barrier properties, it is possible to prevent moisture and hydrogen from entering from the outside. Alternatively, multiple transistors 500 may be collectively surrounded by an insulator with high barrier properties against hydrogen or water. When forming an opening to surround the transistor 500, for example, it is preferable to form an opening that reaches the insulator 522 or the insulator 514 and form the insulator with high barrier properties in contact with the insulator 522 or the insulator 514, because this can serve as part of the manufacturing process of the transistor 500. For example, the insulator with high barrier properties against hydrogen or water may be made of a material similar to that of the insulator 522 or the insulator 514.

[0209] Subsequently, a capacitor 600 is provided above the transistor 500. The capacitor 600 has a conductor 610, a conductor 620, and an insulator 630.

[0210] A conductor 612 may be provided over the conductor 546 and the conductor 548. The conductor 612 functions as a plug or wiring connected to the transistor 500. The conductor 610 functions as an electrode of the capacitor 600. Note that the conductor 612 and the conductor 610 can be formed at the same time.

[0211] A metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium, or a metal nitride film containing any of the above elements (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film), etc. can be used for the conductor 612 and the conductor 610. Alternatively, a conductive material such as indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, or indium tin oxide with silicon oxide added can also be used.

[0212] In this embodiment, the conductor 612 and the conductor 610 have a single-layer structure, but the present invention is not limited to this structure and may have a stacked structure of two or more layers. For example, a conductor having a barrier property and a conductor having high adhesion to the conductor having high conductivity may be formed between a conductor having a barrier property and a conductor having high conductivity.

[0213] The conductor 620 is provided so as to overlap with the conductor 610 with the insulator 630 interposed therebetween. Note that the conductor 620 can be made of a conductive material such as a metal material, an alloy material, or a metal oxide material. It is preferable to use a high-melting-point material such as tungsten or molybdenum that has both heat resistance and conductivity, and tungsten is particularly preferable. Furthermore, when the conductor 620 is formed simultaneously with other structures such as a conductor, a low-resistance metal material such as Cu (copper) or Al (aluminum) can be used.

[0214] An insulator 640 is provided over the conductor 620 and the insulator 630. The insulator 640 can be provided using a material similar to that of the insulator 320. The insulator 640 may also function as a planarizing film that covers the uneven shape underneath.

[0215] By using this structure, miniaturization or high integration can be achieved in a semiconductor device including a transistor including an oxide semiconductor.

[0216] Examples of substrates that can be used in the semiconductor device of one embodiment of the present invention include glass substrates, quartz substrates, sapphire substrates, ceramic substrates, metal substrates (e.g., stainless steel substrates, substrates having stainless steel foil, tungsten substrates, and substrates having tungsten foil), semiconductor substrates (e.g., single-crystal semiconductor substrates, polycrystalline semiconductor substrates, and compound semiconductor substrates), and silicon-on-insulator (SOI) substrates. Plastic substrates that have heat resistance sufficient for the processing temperatures of this embodiment may also be used. Examples of glass substrates include barium borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, and soda-lime glass. Crystallized glass, for example, can also be used.

[0217] Alternatively, a flexible substrate, a laminated film, paper containing a fibrous material, or a base film can be used as the substrate. Examples of flexible substrates, laminated films, and base films include the following: Plastics such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Synthetic resins such as acrylic are also included. Polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride are also included. Polyamide, polyimide, aramid, epoxy, inorganic vapor-deposited films, and paper are also included. In particular, transistors manufactured using semiconductor substrates, single-crystal substrates, or SOI substrates can be manufactured to have small size, high current capacity, and minimal variations in characteristics, size, and shape. Constructing a circuit using such transistors can reduce the power consumption of the circuit or increase the circuit integration.

[0218] Alternatively, a flexible substrate may be used as the substrate, and transistors, resistors, and / or capacitors may be formed directly on the flexible substrate. Alternatively, a release layer may be provided between the substrate and the transistors, resistors, and / or capacitors. The release layer can be used to separate a semiconductor device, after it has been partially or entirely completed, from the substrate and transfer it to another substrate. In this case, the transistors, resistors, and / or capacitors can be transferred to a substrate with poor heat resistance or a flexible substrate. The release layer may be, for example, a laminated structure of an inorganic film made of a tungsten film and a silicon oxide film, a structure in which an organic resin film such as polyimide is formed on a substrate, or a silicon film containing hydrogen.

[0219] That is, a semiconductor device may be formed on a certain substrate and then transferred to another substrate. Examples of substrates onto which a semiconductor device may be transferred include, in addition to the substrates on which the above-mentioned transistors can be formed, paper substrates, cellophane substrates, aramid film substrates, polyimide film substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester), or recycled fibers (acetate, cupra, rayon, recycled polyester)), leather substrates, and rubber substrates. By using these substrates, it is possible to manufacture semiconductor devices that are flexible, durable, heat-resistant, lightweight, or thin.

[0220] (Embodiment 5) In this embodiment, examples of electronic devices using a thin-film secondary battery will be described with reference to FIGS.

[0221] Fig. 11B shows an IC card, which is an example of an application device using the thin-film secondary battery according to the present invention. The power obtained by receiving radio waves 3005 can be charged into thin-film secondary battery 3001 shown in Fig. 11A. An antenna, IC 3004, and thin-film secondary battery 3001 are arranged inside IC card 3000. An owner's ID 3002 and photo 3003 are attached to IC card 3000. The power charged in thin-film secondary battery 3001 can also be used to transmit signals such as authentication signals from the antenna.

[0222] Also, an active matrix display device may be provided in place of the photograph 3003. Examples of active matrix display devices include reflective liquid crystal display devices, organic EL display devices, and electronic paper. The active matrix display device can also display images (moving or still images) and time. Power for the active matrix display device can be supplied from a thin-film secondary battery 3001.

[0223] Since a plastic substrate is used in an IC card, an organic EL display device using a flexible substrate is preferred.

[0224] A solar cell may also be provided, which absorbs external light and generates electricity, which can then be used to charge the thin-film secondary battery 3001.

[0225] Furthermore, the thin-film secondary battery is not limited to use in IC cards, but can also be used as a power source for wireless sensors used in vehicles, a secondary battery for MEMS devices, and the like.

[0226] Figure 12A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. To improve water resistance for everyday use or outdoor use, there is a demand for wearable devices that can be charged wirelessly as well as via wired charging, with the connector exposed.

[0227] For example, a secondary battery can be mounted on an eyeglass-type device 400 as shown in FIG. 12A. The eyeglass-type device 400 has a frame 400a and a display unit 400b. By mounting a secondary battery on the temples of the curved frame 400a, the eyeglass-type device 400 can be made lightweight, have a good weight balance, and have a long continuous use time. The thin-film secondary battery shown in embodiment 1 may also be provided, thereby realizing a configuration that can accommodate space savings associated with a smaller housing.

[0228] Furthermore, a secondary battery can be mounted in headset type device 401. Headset type device 401 has at least microphone unit 401a, flexible pipe 401b, and earphone unit 401c. A secondary battery can be provided in flexible pipe 401b or earphone unit 401c. The thin-film secondary battery shown in embodiment 1 may also be provided, making it possible to realize a configuration that can accommodate space savings associated with a smaller housing.

[0229] Furthermore, a secondary battery can be mounted on device 402 that can be directly attached to the body. Secondary battery 402b can be provided in thin housing 402a of device 402. The thin-film secondary battery described in Embodiment 1 may be provided, and a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0230] Furthermore, a secondary battery can be mounted on device 403 that can be attached to clothing. Secondary battery 403b can be provided in thin housing 403a of device 403. The thin-film secondary battery shown in Embodiment 1 may be provided, and a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0231] Furthermore, a secondary battery can be mounted on the belt type device 406. The belt type device 406 has a belt portion 406a and a wireless power receiving portion 406b, and a secondary battery can be mounted inside the belt portion 406a. The belt type device 406 may be provided with the thin-film secondary battery described in Embodiment 1, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0232] Furthermore, a secondary battery can be mounted on the wristwatch device 405. The wristwatch device 405 has a display portion 405a and a belt portion 405b, and a secondary battery can be provided on the display portion 405a or the belt portion 405b. The wristwatch device 405 may be provided with the thin-film secondary battery described in Embodiment 3, and a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0233] The display unit 405a can display not only the time but also various other information such as incoming emails and phone calls.

[0234] Furthermore, since the wristwatch device 405 is a wearable device that is worn directly on the wrist, it may be equipped with sensors that measure the user's pulse, blood pressure, etc. Data on the user's exercise volume and health can be accumulated and used to help maintain health.

[0235] A detailed description of the wristwatch type device 405 shown in FIG. 12A will be given below.

[0236] FIG. 12B shows a perspective view of the wristwatch type device 405 removed from the wrist.

[0237] 12C shows a side view of the display portion 405a. FIG. 12C shows a state in which a secondary battery 913 is built inside the display portion 405a. The secondary battery 913 is the thin-film secondary battery described in Embodiment 3. The secondary battery 913 is provided at a position overlapping with the display portion 405a, and is small and lightweight. [Explanation of symbols]

[0238] 101: substrate, 201: positive electrode, 202: solid electrolyte layer, 203: negative electrode, 204: positive electrode active material layer, 205: negative electrode active material layer, 206: protective layer, 400: eyeglass-type device, 400a: frame, 400b: display unit, 401: headset-type device, 401a: microphone unit, 401b: flexible pipe, 401c: earphone unit, 402: device, 402a: housing, 402b: secondary battery, 403: device, 403a: housing, 403b: secondary battery, 405: wristwatch type device, 405a: display unit, 405b: belt unit, 406: belt type device, 406a: belt unit, 406b: wireless power supply receiving unit, 3000: IC card, 3001: thin film secondary battery, 3002: ID, 3003: photo, 3004: IC, 3005: radio wave

Claims

1. A positive electrode and a negative electrode; a solid electrolyte layer between the positive electrode and the negative electrode, the solid electrolyte layer having silicon, oxygen, lithium, and carbon; a protective layer; the ratio of oxygen to silicon (O / Si) of the solid electrolyte layer is greater than 1 and less than 2; a protective layer having a region in contact with the solid electrolyte layer protruding from the positive electrode and the negative electrode when viewed from above;

2. A positive electrode and a negative electrode; a solid electrolyte layer between the positive electrode and the negative electrode, the solid electrolyte layer having silicon, oxygen, lithium, and carbon; a protective layer; a ratio of oxygen to silicon (O / Si) of the solid electrolyte layer, determined from an EDX measurement result of a cross section of the solid electrolyte layer, is greater than 1 and less than 2; a protective layer having a region in contact with the solid electrolyte layer protruding from the positive electrode and the negative electrode when viewed from above;

3. 3. The solid secondary battery according to claim 1, wherein the solid electrolyte layer further contains nitrogen.

4. 4. The solid secondary battery according to claim 1, wherein the protective layer comprises silicon nitride.

Images