Power storage device

Abstract

To provide a power storage device and the like that consume less power, or a power storage device and the like having a high degree of integration.SOLUTION: There is provided a power storage device in which a first battery cell has a first electrode on a first substrate, a positive electrode active material layer on the first electrode, an electrolyte layer on the positive electrode active material layer, a negative electrode active material layer on the electrolyte layer, and a second electrode on the negative electrode active material layer, a comparator circuit has a first input terminal, a second input terminal, an output terminal, and a first transistor, the first transistor has an oxide semiconductor on the first substrate, a first insulator on the oxide semiconductor, and a gate electrode on the first insulator, the first electrode is electrically connected to a gate of the first transistor and the first input terminal, the comparator circuit has a function of outputting, from the output terminal to a control circuit, a first signal in response to a result of comparison between a potential of the first electrode and a desired reference potential, and the control circuit has a function of controlling charging of the first battery cell in response to the first signal.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] BACKGROUND OF THE INVENTION 1. Field of the Invention One embodiment of the present invention relates to a semiconductor device and a method for operating the semiconductor device. 2. Description of the Related Art One embodiment of the present invention relates to a battery control circuit, a battery protection circuit, a power storage device, and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of the invention disclosed in this specification relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a display device, a light-emitting device, a power storage device, an imaging device, a memory device, a driving method thereof, or a manufacturing method thereof. [Background technology]

[0003] Energy storage devices (also known as batteries or secondary batteries) are now used in a wide range of fields, from small electronic devices to automobiles. As the range of applications for batteries expands, there are also more applications using multi-cell battery stacks, in which multiple battery cells are connected in series.

[0004] Energy storage devices are equipped with circuits to detect abnormalities during charging and discharging, such as over-discharge, over-charge, overcurrent, or short circuit. In this way, the circuits that protect and control the battery acquire data such as voltage and current to detect abnormalities during charging and discharging. Furthermore, these circuits use the observed data to control operations such as stopping charging and discharging and balancing cells.

[0005] Patent Document 1 discloses a protection IC that functions as a battery protection circuit. The protection IC has multiple internal comparators that compare a reference voltage with the voltage at the terminal to which the battery is connected to detect abnormalities during charging and discharging.

[0006] Furthermore, Patent Document 2 discloses a battery state detection device that detects minute short circuits in a secondary battery, and a battery pack incorporating the same.

[0007] Furthermore, Patent Document 3 discloses a protective semiconductor device that protects a battery pack in which secondary battery cells are connected in series. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent Application Publication No. 2011-267726 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-66161 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-220389 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of one embodiment of the present invention is to provide a novel battery control circuit, battery protection circuit, power storage device, semiconductor device, vehicle, electronic device, etc. Another object of one embodiment of the present invention is to provide a battery control circuit, battery protection circuit, power storage device, semiconductor device, vehicle, electronic device, etc. that consumes low power. Another object of one embodiment of the present invention is to provide a highly integrated battery control circuit, battery protection circuit, power storage device, semiconductor device, vehicle, electronic device, etc.

[0010] The problems of one embodiment of the present invention are not limited to the problems listed above. The problems listed above do not preclude the existence of other problems. The other problems are problems not mentioned in this section, which will be described below. Problems not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be extracted as appropriate from these descriptions. One embodiment of the present invention solves at least one of the problems listed above and / or other problems. [Means for solving the problem]

[0011] One embodiment of the present invention is a power storage device including a first substrate, a first battery cell, a comparison circuit, and a control circuit. The first battery cell includes a first electrode over the first substrate, a positive electrode active material layer over the first electrode, an electrolyte layer over the positive electrode active material layer, a negative electrode active material layer over the electrolyte layer, and a second electrode over the negative electrode active material layer. The comparison circuit includes a first input terminal, a second input terminal, an output terminal, and a first transistor. The first transistor includes an oxide semiconductor over the first substrate, a first insulator over the oxide semiconductor, and a gate electrode over the first insulator. The first electrode is electrically connected to a gate of the first transistor and the first input terminal. The comparison circuit outputs a first signal from the output terminal to the control circuit, the first signal being indicative of a comparison result between a potential of the first electrode and a desired reference potential. The control circuit controls charging of the first battery cell in accordance with the first signal.

[0012] In addition, in the above configuration, it is preferable that the semiconductor device further includes a second transistor and a capacitor, one of the source and the drain of the second transistor is electrically connected to the second input terminal, the other of the source and the drain of the second transistor is electrically connected to one electrode of the capacitor, and the second transistor includes an oxide semiconductor.

[0013] In the above structure, the output terminal is preferably electrically connected to the source or drain of the first transistor.

[0014] In the above configuration, it is preferable that the semiconductor device includes a second transistor including an oxide semiconductor, a third transistor including an oxide semiconductor, and a capacitor, wherein one of a source and a drain of the second transistor is electrically connected to a second input terminal and a gate of the third transistor, the other of the source and the drain of the second transistor is electrically connected to one electrode of the capacitor, and the output terminal is electrically connected to the source or the drain of the third transistor.

[0015] In addition, in the above configuration, it is preferable that the first transistor has a second insulator on a gate electrode thereof and a third electrode on the second insulator, the first electrode is located on the second insulator, the first electrode and the third electrode each have a titanium compound, and the third electrode is electrically connected to the source or drain of the first transistor.

[0016] In the above structure, it is preferable that the first transistor has a source electrode and a drain electrode, and that the first electrode, the source electrode of the first transistor, and the drain electrode of the first transistor each contain a titanium compound.

[0017] In the above structure, the first electrode and the gate electrode of the first transistor preferably each contain a titanium compound.

[0018] Furthermore, in the above configuration, it is preferable that the device has a second battery cell, a conversion circuit, a clock generation circuit, a boost circuit, and a voltage holding circuit, the first transistor has a back gate, the conversion circuit has a function of converting the positive electrode potential of the second battery cell and providing it as a second signal to the clock generation circuit, the clock generation circuit has a function of generating a third signal that is a clock signal using the second signal, the boost circuit has a function of generating a first potential using the third signal, and the voltage holding circuit has a function of providing the first potential to the back gate and holding it.

[0019] In the above configuration, the first substrate is preferably any one of a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, a metal substrate, a semiconductor substrate, an SOI substrate, and a plastic substrate.

[0020] In the above structure, it is preferable that the first substrate is a semiconductor substrate, the first substrate includes silicon, and the transistor has a channel formation region provided in the first substrate.

[0021] Another embodiment of the present invention is a power storage device including a first substrate, a first transistor including an oxide semiconductor over the first substrate, a first insulator over the oxide semiconductor, and a gate electrode over the first insulator, a second insulator over the oxide semiconductor, a first electrode over the second insulator, a positive electrode active material layer over the first electrode, an electrolyte layer over the positive electrode active material layer, a negative electrode active material layer over the electrolyte layer, and a second electrode over the negative electrode active material layer, and a third electrode over the second insulator, wherein the third electrode is electrically connected to a source or a drain of the first transistor.

[0022] In the above configuration, the first electrode and the third electrode preferably contain a titanium compound.

[0023] In the above structure, the first transistor preferably includes an oxide semiconductor in a channel formation region.

[0024] In addition, in the above configuration, it is preferable that the device has a fourth electrode on the third electrode and a third insulator sandwiched between the third electrode and the fourth electrode, and that the first electrode and the fourth electrode each contain a titanium compound.

[0025] In the above configuration, it is preferable that the piezoelectric element further comprises a fourth electrode on the third electrode and a piezoelectric layer sandwiched between the third electrode and the fourth electrode, and that the first electrode and the fourth electrode each contain a titanium compound.

[0026] Another embodiment of the present invention is a power storage device including: a first substrate; a first transistor including a source electrode and a drain electrode over the first substrate, an oxide semiconductor over the source electrode and the drain electrode, a first insulator over the oxide semiconductor, and a gate electrode over the first insulator; and a first battery cell including a first electrode over the first substrate, a positive electrode active material layer over the first electrode, an electrolyte layer over the positive electrode active material layer, a negative electrode active material layer over the electrolyte layer, and a second electrode over the negative electrode active material layer, in which the source electrode, the drain electrode, and the first electrode each contain a titanium compound.

[0027] Alternatively, one embodiment of the present invention is an electronic device including a first substrate, a first battery cell, a comparison circuit, a control circuit, and a piezoelectric element. The first battery cell includes a first electrode on the first substrate, a positive electrode active material layer on the first electrode, an electrolyte layer on the positive electrode active material layer, a negative electrode active material layer on the electrolyte layer, and a second electrode on the negative electrode active material layer. The comparison circuit includes a first transistor. The first transistor includes an oxide semiconductor on the first substrate, a first insulator on the oxide semiconductor, and a gate electrode on the first insulator. The piezoelectric element includes a third electrode, a piezoelectric layer on the third electrode, and a fourth electrode on the piezoelectric layer. The first electrode is electrically connected to the gate electrode of the first transistor. The comparison circuit has a function of outputting a first signal according to a comparison result between a potential of the first electrode and a desired potential to the control circuit. The control circuit has a function of controlling charging of the first battery cell according to the first signal.

[0028] In the above configuration, it is preferable that the first electrode and the third electrode each contain a titanium compound.

[0029] Alternatively, one embodiment of the present invention is an electronic device including a first substrate, a first battery cell, a comparison circuit, a display unit, and a driver circuit. The first substrate is selected from a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, a metal substrate, a semiconductor substrate, an SOI substrate, and a plastic substrate. The first battery cell includes a first electrode over the first substrate, a positive electrode active material layer over the first electrode, an electrolyte layer over the positive electrode active material layer, a negative electrode active material layer over the electrolyte layer, and a second electrode over the negative electrode active material layer. The first electrode includes a titanium compound. The comparison circuit includes a first transistor including an oxide semiconductor over the first substrate, a source electrode and a drain electrode over the oxide semiconductor, a first insulator over the oxide semiconductor, and a gate electrode over the first insulator. The first electrode is electrically connected to a gate of the first transistor. The driver circuit has a function of applying an image signal to the display unit. The driver circuit includes a plurality of transistors including an oxide semiconductor.

[0030] Alternatively, one embodiment of the present invention includes a first substrate, a first battery cell, a comparison circuit, and a control circuit. The first battery cell includes a first electrode over the first substrate, a positive electrode active material layer over the first electrode, an electrolyte layer over the positive electrode active material layer, a negative electrode active material layer over the electrolyte layer, and a second electrode over the negative electrode active material layer. The first electrode includes a titanium compound. The comparison circuit includes a first input terminal, a second input terminal, an output terminal, and a first transistor. The first transistor includes an oxide semiconductor over the first substrate and an oxide a first input terminal electrically connected to the gate electrode; a first electrode electrically connected to the first input terminal; a comparator circuit having a function of outputting a first signal according to a comparison result between the potential of the first electrode and a desired reference potential from an output terminal to a control circuit; and a control circuit having a function of controlling charging of a first battery cell according to the first signal. [Effects of the Invention]

[0031] One embodiment of the present invention can provide a novel battery control circuit, a novel battery protection circuit, a power storage device, a semiconductor device, a vehicle, an electronic device, etc. One embodiment of the present invention can provide a battery control circuit, a battery protection circuit, a power storage device, a semiconductor device, a vehicle, an electronic device, etc. that consumes low power. One embodiment of the present invention can also provide a highly integrated battery control circuit, a battery protection circuit, a power storage device, a semiconductor device, a vehicle, an electronic device, etc.

[0032] The effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not preclude the existence of other effects. The other effects are described below and are not mentioned in this section. Effects not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be extracted as appropriate from these descriptions. One embodiment of the present invention has at least one of the effects listed above and / or other effects. Therefore, one embodiment of the present invention may not have the effects listed above in some cases. [Brief explanation of the drawings]

[0033] [Figure 1] 1A and 1B are a top view and a cross-sectional view of a secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing one embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view 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 cross-sectional view showing one embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view showing one embodiment of the present invention. [Figure 7] 7A and 7B are cross-sectional views illustrating a transistor according to one embodiment of the present invention. [Figure 8] 8A and 8B are top views of a secondary battery according to one embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram illustrating one embodiment of the present invention. [Figure 10] 10A and 10B are circuit diagrams illustrating one embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram illustrating one embodiment of the present invention. [Figure 12] 12A and 12B are block diagrams illustrating one embodiment of the present invention, and circuit diagrams illustrating one embodiment of the present invention. [Figure 13] 13A and 13B are circuit diagrams illustrating one embodiment of the present invention. [Figure 14] 14A, 14B, and 14C are circuit diagrams illustrating one embodiment of the present invention. [Figure 15] 15A and 15B are circuit diagrams illustrating one embodiment of the present invention. [Figure 16] FIG. 16 is a diagram illustrating an example of an electronic device. [Figure 17] Fig. 17A is a diagram illustrating an example of an electronic device, Fig. 17B is a diagram illustrating an example of an electronic device, and Fig. 17C is a diagram illustrating an example of an electronic device. [Figure 18] 18A and 18B are diagrams illustrating an example of an electronic device. [Figure 19] Fig. 19A is a diagram illustrating an example of an electronic device. Fig. 19B is a diagram illustrating an example of an electronic device. Fig. 19C is a diagram illustrating an example of an aircraft. Fig. 19D is a diagram illustrating an example of a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, embodiments will be described with reference to the drawings. However, it will be readily understood by those skilled in the art that the embodiments can be implemented in many different ways and that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the following description of the embodiments.

[0035] In this specification, the ordinal numbers "first," "second," and "third" are used to avoid confusion between components. Therefore, they do not limit the number of components. Furthermore, they do not limit the order of the components. For example, a component referred to as "first" in one embodiment of this specification may be a component referred to as "second" in another embodiment or in the claims. For example, a component referred to as "first" in one embodiment of this specification may be omitted in another embodiment or in the claims.

[0036] In the drawings, the same elements or elements having similar functions, elements made of the same material, or elements formed at the same time may be given the same reference numerals, and repeated explanations thereof may be omitted.

[0037] Furthermore, the position, size, range, etc. of each component shown in the drawings, etc. may not represent the actual position, size, range, etc. in order to facilitate understanding of the invention. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings, etc. For example, in an actual manufacturing process, a resist mask, etc. may be unintentionally eroded by a process such as etching, but this may not be reflected in the drawings in order to facilitate understanding.

[0038] In addition, in top views (also called "plan views"), perspective views, and the like, some components may be omitted to make the drawings easier to understand.

[0039] Furthermore, the terms "electrode" and "wiring" used in this specification and elsewhere do not limit the functionality of these components. For example, an "electrode" may be used as part of a "wiring," and vice versa. Furthermore, the terms "electrode" and "wiring" also include cases where multiple "electrodes" or "wirings" are integrally formed.

[0040] Furthermore, in this specification etc., the term "terminal" may refer to, for example, a wiring or an electrode connected to a wiring. Furthermore, in this specification etc., a part of a "wiring" may be called a "terminal".

[0041] In this specification, the terms "above" and "below" do not limit the positional relationship of components to being directly above or below, and being in direct contact with each other. For example, the expression "electrode B on insulating layer A" does not necessarily mean that electrode B is formed on insulating layer A in direct contact with it, and does not exclude the inclusion of other components between insulating layer A and electrode B.

[0042] In addition, the functions of the source and drain are interchangeable depending on operating conditions, such as when transistors of different polarities are used or when the direction of current changes during circuit operation, making it difficult to define which is the source and which is the drain. For this reason, the terms source and drain can be used interchangeably in this specification.

[0043] Furthermore, in this specification, "electrically connected" includes both direct connection and connection via "something that has some kind of electrical effect." Here, "something that has some kind of electrical effect" is not particularly limited as long as it allows electrical signals to be transmitted and received between the connected objects. Therefore, even when the expression "electrically connected" is used, in an actual circuit, there may be no physical connection and only wiring may be extended.

[0044] Furthermore, in this specification, "parallel" refers to a state in which two straight lines are arranged at an angle of, for example, -10° or more and 10° or less. Therefore, it also includes cases in which the angle is -5° or more and 5° or less. Furthermore, "perpendicular" and "orthogonal" refer to a state in which two straight lines are arranged at an angle of, for example, 80° or more and 100° or less. Therefore, it also includes cases in which the angle is 85° or more and 95° or less.

[0045] In this specification and elsewhere, when referring to counting values ​​and measurement values, terms such as "same," "equal," or "uniform" are used, they are considered to include an error of plus or minus 20%, unless otherwise specified.

[0046] In addition, in this specification, when etching is performed after forming a resist mask, the resist mask is removed after the etching is completed unless otherwise specified.

[0047] Furthermore, voltage often refers to the potential difference between a certain potential and a reference potential (for example, a ground potential or a source potential). Therefore, voltage and potential can often be used interchangeably.

[0048] It should be noted that even when written as "semiconductor," if the conductivity is sufficiently low, it will have the properties of an "insulator." Therefore, it is also possible to use "semiconductor" instead of "insulator." In this case, the boundary between "semiconductor" and "insulator" is vague, and it is difficult to strictly distinguish between the two. Therefore, "semiconductor" and "insulator" described in this specification may be read interchangeably.

[0049] Furthermore, even when written as "semiconductor," if the conductivity is sufficiently high, it will have the properties of a "conductor." Therefore, it is also possible to use "semiconductor" instead of "conductor." In this case, the boundary between "semiconductor" and "conductor" is vague, and it is difficult to strictly distinguish between the two. Therefore, "semiconductor" and "conductor" described in this specification may be read interchangeably.

[0050] In this specification and the like, the "on state" of a transistor refers to a state in which the source and drain of the transistor are considered to be electrically short-circuited (also referred to as a "conductive state"). The "off state" of a transistor refers to a state in which the source and drain of the transistor are considered to be electrically disconnected (also referred to as a "non-conductive state").

[0051] In this specification, the term "on-state current" may refer to a current that flows between the source and drain of a transistor when the transistor is on, and the term "off-state current" may refer to a current that flows between the source and drain of a transistor when the transistor is off.

[0052] In this specification, the high power supply potential VDD (hereinafter simply referred to as "VDD" or "H potential") refers to a power supply potential that is higher than the low power supply potential VSS. The low power supply potential VSS (hereinafter simply referred to as "VSS" or "L potential") refers to a power supply potential that is lower than the high power supply potential VDD. The ground potential can also be used as VDD or VSS. For example, when VDD is the ground potential, VSS is a potential lower than the ground potential, and when VSS is the ground potential, VDD is a potential higher than the ground potential.

[0053] In this specification and the like, a gate refers to a gate electrode and a part or all of a gate wiring, and a gate wiring refers to a wiring for electrically connecting the gate electrode of at least one transistor to another electrode or another wiring.

[0054] In this specification, the term "source" refers to a source region, a source electrode, and part or all of a source wiring. The term "source region" refers to a region of a semiconductor layer whose resistivity is equal to or less than a certain value. The term "source electrode" refers to a conductive layer connected to the source region. The term "source wiring" refers to wiring that electrically connects the source electrode of at least one transistor to another electrode or wiring.

[0055] In this specification, the term "drain" refers to a part or all of the drain region, drain electrode, and drain wiring. The term "drain region" refers to a region of the semiconductor layer whose resistivity is equal to or less than a certain value. The term "drain electrode" refers to a conductive layer connected to the drain region. The term "drain wiring" refers to wiring that electrically connects the drain electrode of at least one transistor to another electrode or wiring.

[0056] (Embodiment 1) A secondary battery of one embodiment of the present invention will be described with reference to FIG.

[0057] [Secondary battery configuration]

[0058] 1A and 1B show a specific example of a secondary battery 200 according to one embodiment of the present invention. Here, the secondary battery 200 formed over a substrate 110 will be described.

[0059] FIG. 1A is a top view, and FIG. 1B is a cross-sectional view taken along line A-A' in FIG. 1A. The secondary battery 200 is a thin-film battery. As shown in FIG. 1B, a stack of a positive electrode 100 and a solid electrolyte layer 203 is formed on a substrate 110, and a negative electrode 210 is formed on the solid electrolyte layer 203. The positive electrode 100 includes a positive electrode current collector 103 and a positive electrode active material layer 101 on the positive electrode current collector 103. The negative electrode 210 includes a negative electrode active material layer 204 and a negative electrode current collector 205 on the negative electrode active material layer 204. The solid electrolyte layer 203 is provided between the positive electrode active material layer 101 and the negative electrode active material layer 204.

[0060] Further, it is preferable that a protective layer 206 is formed on the positive electrode 100, the solid electrolyte layer 203, and the negative electrode 210 of the secondary battery 200.

[0061] The films forming these layers can be formed using a metal mask respectively. The positive electrode current collector 103, the positive electrode active material layer 101, the solid electrolyte layer 203, the negative electrode active material layer 204, and the negative electrode current collector 205 can be selectively formed using a sputtering method. Also, the solid electrolyte layer 203 may be selectively formed by using a co-evaporation method and a metal mask.

[0062] As shown in FIG. 1A, a part of the negative electrode current collector 205 is exposed to form a negative electrode terminal portion. Also, a part of the positive electrode current collector 103 is exposed to form a positive electrode terminal portion. Regions other than the negative electrode terminal portion and the positive electrode terminal portion are covered with the protective layer 206.

[0063] As the positive electrode current collector 103, it is preferable to use a material having conductivity. Also, it is preferable to use a material that is easy to suppress oxidation. For example, titanium oxide, titanium nitride, titanium oxide partially substituted with nitrogen, titanium nitride partially substituted with oxygen, or titanium oxynitride (TiO x N y , 0 < x < 2, 0 < y < 1), etc. can be applied. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By using titanium nitride, the crystal structure of the positive electrode active material layer 101 may be stabilized.

[0064] Alternatively, a laminated structure may be used for the positive electrode current collector 103. For example, a first layer containing a material such as a metal, such as gold, platinum, aluminum, titanium, copper, magnesium, iron, cobalt, nickel, zinc, germanium, indium, silver, or palladium, or an alloy thereof, may be provided, and a second layer containing a titanium compound may be provided on the first layer.

[0065] The material of the solid electrolyte layer 203 is Li 0.35 La 0.55 TiO3, La (2 / 3-X) Li 3X TiO3, Li3PO4, Li X PO (4-Y) N Y , LiNb (1-X) Ta (X) WO6, Li7La3Zr2O 12 , Li (1+X) Al (X) Ti (2-X) (PO4)3, Li (1+X) Al (X) Ge (2-X) Examples include (PO4)3 and LiNbO2. Note that X>0 and Y>0. Film formation methods include sputtering and vapor deposition.

[0066] The solid electrolyte layer 203 may have a laminated structure. When the solid electrolyte layer 203 is laminated, one layer is made of a material in which nitrogen is added to lithium phosphate (Li3PO4) (Li3PO (4-Z) N Z It is also possible to laminate a thin film of SiO2 (also called LiPON), where Z>0.

[0067] The solid electrolyte layer 203 can be formed by, for example, a sputtering method.

[0068] The positive electrode active material layer 101 contains lithium, a transition metal M, and oxygen. It can also be said that the positive electrode active material layer 101 contains a composite oxide containing lithium and the transition metal M.

[0069] The transition metal M contained in the positive electrode active material layer 101 is preferably a metal capable of forming a layered rock-salt composite oxide belonging to the space group R-3m with lithium. For example, one or more of manganese, cobalt, and nickel can be used as the transition metal M. That is, the positive electrode active material layer 101 may contain only cobalt, only nickel, a combination of cobalt and manganese, or a combination of cobalt and nickel, or three of cobalt, manganese, and nickel. That is, the positive electrode active material layer 101 may contain a composite oxide containing lithium and the transition metal M, such as lithium cobalt oxide, lithium nickel oxide, lithium cobalt oxide in which some of the cobalt is substituted with manganese, lithium cobalt oxide in which some of the cobalt is substituted with nickel, or nickel-manganese-lithium cobalt oxide.

[0070] Furthermore, the positive electrode active material layer 101 may contain elements other than the transition metal M, such as magnesium, fluorine, and aluminum, in addition to the above. These elements may further stabilize the crystal structure of the positive electrode active material layer 101. That is, the positive electrode active material layer 101 may contain lithium cobalt oxide to which magnesium and fluorine have been added, lithium nickel-cobalt oxide to which magnesium and fluorine have been added, lithium cobalt-aluminate to which magnesium and fluorine have been added, nickel-cobalt-lithium aluminum oxide, nickel-cobalt-lithium aluminum oxide, or nickel-cobalt-lithium aluminum oxide to which magnesium and fluorine have been added.

[0071] When the positive electrode active material layer 101 contains lithium, cobalt, nickel, aluminum, magnesium, oxygen, and fluorine, the atomic ratio of nickel is preferably, for example, 0.05 to 2, more preferably 0.1 to 1.5, and even more preferably 0.1 to 0.9, when the atomic ratio of cobalt in the positive electrode active material layer 101 is taken as 100. The atomic ratio of aluminum is preferably, for example, 0.05 to 2, more preferably 0.1 to 1.5, and even more preferably 0.1 to 0.9, when the atomic ratio of cobalt in the positive electrode active material layer 101 is taken as 100. The atomic ratio of magnesium is preferably, for example, 0.1 to 6, more preferably 0.3 to 3. Furthermore, when the atomic ratio of magnesium in the positive electrode active material layer 101 is taken as 1, the atomic ratio of fluorine is preferably, for example, 2 to 3.9.

[0072] By containing nickel, aluminum, and magnesium at the above concentrations, a stable crystal structure can be maintained even after repeated charge and discharge at high voltages, resulting in a positive electrode active material layer 101 with high capacity and excellent charge and discharge cycle characteristics.

[0073] The molar concentrations of cobalt, nickel, aluminum, and magnesium can be determined, for example, by inductively coupled plasma mass spectrometry (ICP-MS), and the molar concentration of fluorine can be determined, for example, by glow discharge mass spectrometry (GD-MS).

[0074] For example, a composite oxide having a spinel crystal structure can be used as the positive electrode active material. Also, for example, a polyanion-based material can be used as the positive electrode active material. Examples of polyanion-based materials include materials having an olivine crystal structure and Nasicon-based materials. Also, for example, a material containing sulfur can be used as the positive electrode active material.

[0075] As a material having a spinel-type crystal structure, for example, a composite oxide represented by the general formula LiM2O4 can be used. In the general formula LiM2O4, it is preferable to have Mn as the element M. For example, LiMn2O4 can be used. Furthermore, in the general formula LiM2O4, by having Ni in addition to Mn as the element M, the discharge voltage of the secondary battery can be improved and the energy density can be improved, which is preferable. Furthermore, a small amount of lithium nickel oxide (LiNiO2 or LiNi 1-x M x Mixing O2 (M=Co, Al, etc.) is preferable because it can improve the characteristics of the secondary battery.

[0076] An example of a polyanionic material that can be used is a composite oxide containing oxygen, a metal A, a metal M, and an element Z. The metal A contained in the polyanionic material is one or more of Li, Na, and Mg, the metal M contained in the polyanionic material is one or more of Fe, Mn, Co, Ni, Ti, V, and Nb, and the element Z is one or more of S, P, Mo, W, As, and Si.

[0077] As a material having an olivine-type crystal structure, for example, a composite material (general formula LiMPO4 (M is one or more of Fe(II), Mn(II), Co(II), and Ni(II))) can be used. Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, and LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4(a+b is less than 1, 0 <a<1、0<b<1)、LiFe c Ni d Co e PO4, LiFe c Ni d Mne PO4, LiNi c Co d Mn e PO4 (c + d + e is less than or equal to 1, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is less than or equal to 1, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc., lithium compounds can be used.

[0078] Also, composite materials such as general formula Li (2-j) MSiO4 (M is one or more of Fe(II), Mn(II), Co(II), Ni(II), 0 ≦ j ≦ 2) can be used. General formula Li (2-j) As representative examples of general formula Li (2-j) FeSiO4, Li (2-j) NiSiO4, Li (2-j) CoSiO4, Li (2-j) MnSiO4, Li (2-j) Fe k Ni l SiO4, Li (2-j) Fe k Co l SiO4, Li (2-j) Fe k Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k Mn l SiO4 (k + l is less than or equal to 1, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li<000007​​​​​​​​​​​​​​​​​​​​Co t Mn u Lithium compounds such as SiO4 (where r + s + t + u ≤ 1, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1) can be used as materials.

[0079] Also, A x NASICON-type compounds represented by the general formula M2(XO4)3 (A = Li, Na, Mg, M = Fe, Mn, Ti, V, Nb, X = S, P, Mo, W, As, Si) can be used. Examples of NASICON-type compounds include Fe2(MnO4)3, Fe2(SO4)3, Li3Fe2(PO4)3, etc. Also, as the positive electrode active material, compounds represented by the general formula Li2MPO4F, Li2MP2O7, Li5MO4 (M = Fe, Mn) can be used.

[0080] Also, as the positive electrode active material, perovskite-type fluorides such as NaFeF3, FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2, MoS2, oxides having an inverse spinel crystal structure such as LiMVO4, vanadium oxides (V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, and other materials may be used.

[0081] Also, as the positive electrode active material, borate-based materials represented by the general formula LiMBO3 (M is Fe(II), Mn(II), Co(II)) may be used.

[0082] Examples of materials containing sodium include sodium-containing oxides such as NaFeO2, Na 2 / 3 [Fe 1 / 2 Mn 1 / 2 O2, Na 2 / 3 [Ni 1 / 3 Mn 2 / 3 O2, Na2Fe2(SO4)3, Na3V2(PO4)3, Na2FePO4F, NaVPO4F, NaMPO4 (M is Fe(II), Mn(II), Co(II), Ni(II)), Na2FePO4F, Na4Co3(PO4)2P2O7, etc., can be used as the positive electrode active material.

[0083] Alternatively, lithium-containing metal sulfides such as Li2TiS3 and Li3NbS4 may be used as the positive electrode active material.

[0084] As the positive electrode active material of one embodiment of the present invention, two or more of the materials listed above may be mixed and used.

[0085] For the negative electrode active material layer 204, silicon, carbon, titanium oxide, vanadium oxide, indium oxide, zinc oxide, tin oxide, nickel oxide, etc. can be used. Also, materials that can be alloyed with Li, such as tin, gallium, and aluminum, can be used. Metal oxides that can be alloyed with these can also be used. Lithium titanium oxide (Li4Ti5O 12 Among them, the negative electrode active material layer 204 may be made of a material containing silicon and oxygen (SiO x It is preferable to use a lithium metal film (also referred to as a lithium film) for the negative electrode active material layer 204.

[0086] In the secondary battery 200, a positive electrode, a solid electrolyte layer, and a negative electrode may be combined into a set, and multiple sets may be stacked and connected in series to increase the voltage of the secondary battery.

[0087] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0088] (Embodiment 2) In this embodiment, a structural example of a power storage device of one embodiment of the present invention will be described.

[0089] A power storage device of one embodiment of the present invention includes a secondary battery and a battery control circuit. The battery control circuit has, for example, a function of protecting the secondary battery. The battery control circuit has, for example, a function of controlling charging of the secondary battery. The battery control circuit has, for example, a function of monitoring the voltage of the secondary battery.

[0090] The battery control circuit of one embodiment of the present invention preferably includes a transistor having an oxide semiconductor in a channel formation region (hereinafter referred to as an OS transistor). The battery control circuit including an OS transistor will be described in detail later. The battery control circuit of one embodiment of the present invention may also include a transistor having silicon, germanium, silicon germanium, silicon carbide, or the like in a channel formation region in addition to the OS transistor.

[0091] FIG. 2 illustrates a configuration example applicable to a power storage device of one embodiment of the present invention. In the configuration example illustrated in FIG. 2, a secondary battery 200 and a transistor 500, which is an OS transistor included in a battery control circuit, are stacked over a substrate 599. Although FIG. 2 illustrates an example in which one secondary battery is provided over the substrate 599, two or more secondary batteries may be provided over the substrate 599. In such a case, for example, either the positive electrode or the negative electrode of the secondary batteries may be shared. Furthermore, it is preferable to use the same material for the positive electrode, the negative electrode, the electrolyte, and the like.

[0092] Examples of the substrate 599 include glass substrates, quartz substrates, sapphire substrates, ceramic substrates, metal substrates (e.g., stainless steel substrates, substrates with stainless steel foil, tungsten substrates, substrates with tungsten foil, etc.), semiconductor substrates (e.g., single-crystal semiconductor substrates, polycrystalline semiconductor substrates, or compound semiconductor substrates), SOI (Silicon-on-Insulator) substrates, and plastic substrates. Flexible substrates, laminated films, paper containing fibrous materials, and base films can also be used. 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 examples. Polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride are also examples. Other examples include polyamide, polyimide, aramid resin, epoxy resin, inorganic vapor deposition film, and paper.

[0093] 2, an insulator 514 is provided over a substrate 599. A film having a barrier property that prevents diffusion of hydrogen and impurities is preferably used as the insulator 514. For example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, or the like can be used as the insulator 514.

[0094] 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.

[0095] <Transistor 500> In the transistor 500, a metal oxide functioning as an oxide semiconductor is preferably used for the oxide 530 including the channel formation region. For example, a metal oxide such as In-M-Zn oxide (wherein 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, or the like) may be used as the oxide 530.

[0096] Specifically, oxide 530a may be a metal oxide having an atomic ratio of In:Ga:Zn=1:3:4 or 1:1:0.5. Oxide 530b may be a metal oxide having an atomic ratio of In:Ga:Zn=4:2:3 or 1:1:1. Oxide 530c may be a metal oxide having an atomic ratio of In:Ga:Zn=1:3:4, Ga:Zn=2:1, or Ga:Zn=2:5. Specific examples of the oxide 530c having a layered structure include a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and In:Ga:Zn=1:3:4 [atomic ratio], a layered structure of Ga:Zn=2:1 [atomic ratio] and In:Ga:Zn=4:2:3 [atomic ratio], a layered structure of Ga:Zn=2:5 [atomic ratio] and In:Ga:Zn=4:2:3 [atomic ratio], and a layered structure of gallium oxide and In:Ga:Zn=4:2:3 [atomic ratio].

[0097] The oxide 530b may be crystalline. For example, it is preferable to use a c-axis aligned crystalline oxide semiconductor (CAAC-OS) described later. Crystalline oxides such as CAAC-OS have few impurities and defects (such as oxygen vacancies), have high crystallinity, and have a dense structure. This can prevent the source or drain electrode from extracting oxygen from the oxide 530b. Furthermore, even when heat treatment is performed, the transistor 500 is stable against high temperatures (so-called thermal budget) in the manufacturing process because extraction of oxygen from the oxide 530b can be reduced.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] The conduction band minimum energy of the oxide 530a and the oxide 530c is preferably higher than that of the oxide 530b. In other words, the electron affinity of the oxide 530a and the oxide 530c is preferably smaller than that of the oxide 530b.

[0102] Here, the energy level of the conduction band minimum changes gradually 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.

[0103] Specifically, when the oxide 530a and the oxide 530b, and the oxide 530b and the oxide 530c have 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 oxide 530a and the oxide 530c may be made of an In-Ga-Zn oxide, a Ga-Zn oxide, or a gallium oxide.

[0104] 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. As a result, the influence of interface scattering on carrier conduction is reduced, and the transistor 500 can obtain a high on-state current.

[0105] 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.

[0106] 2, the conductor 542a and the conductor 542b are shown as single-layer structures, but they may also have a stacked structure of 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.

[0107] Further, there are three-layer structures 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, 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, etc. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may also be used.

[0108] 2, 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 one of a source region and a drain region, and the region 543b functions as the other of the source region and the drain region. A channel formation region is formed in a region sandwiched between the regions 543a and 543b.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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). In particular, hafnium aluminate has higher heat resistance than a hafnium oxide film. Therefore, it is preferable because it is less likely to crystallize during heat treatment in a later process. Note that the insulator 544 is not an essential component 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 may be designed appropriately depending on the desired transistor characteristics.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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. Similar 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.

[0117] 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.

[0118] The insulator 550 may have a stacked 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 stacked structure of a high-k material and a thermally stable material for the insulator that functions as the gate insulating film, it becomes possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. Furthermore, a stacked structure that is thermally stable and has a high dielectric constant can be achieved.

[0119] The conductor 560 functioning as the first gate electrode is shown as having a two-layer structure in FIG. 2, but may have a single-layer structure or a stacked structure of three or more layers.

[0120] 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 conductor 560a has the function of suppressing the diffusion of oxygen, which can suppress the oxidation of the conductor 560b due to the oxygen contained in the insulator 550, thereby preventing a decrease in conductivity. Examples of conductive materials that suppress the diffusion of oxygen include tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Alternatively, the conductor 560a can be made of an oxide semiconductor that can be used for the oxide 530. 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.

[0121] 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-mentioned conductive material.

[0122] 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 excess oxygen regions in a later step.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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, excess oxygen regions can be provided in the insulator 550 and the insulator 580. This allows oxygen to be supplied from the excess oxygen regions into the oxide 530.

[0127] For example, the insulator 574 can be a metal oxide containing one or more elements selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like.

[0128] 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.

[0129] 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.

[0130] The conductor 540a and the conductor 540b are placed in openings formed in the insulator 581, the insulator 574, the insulator 580, and the insulator 544. The conductor 540a and the conductor 540b are provided opposite to each other with the conductor 560 interposed therebetween.

[0131] The conductor 610 and the secondary battery 200 are provided on the insulator 581. The conductor 610 functions as a wiring that connects to the conductor 540a.

[0132] The conductor 610 is preferably made of the same material as the positive electrode current collector 103. By using the same material for the conductor 610 and the positive electrode current collector 103, they can be formed using the same process, facilitating manufacturing.

[0133] 3 is different from FIG. 2 in that a capacitive element 600 and a sensor element 660 are provided on an insulator 581. In FIG.

[0134] The example configuration shown in Figure 3 has an insulator 514 on a substrate 599, a transistor 500 on the insulator 514, an insulator 574 and an insulator 581 on the transistor 500, conductors 540a and 540b formed so as to be embedded in insulator 580, insulator 574 and insulator 581, and conductor 540a functions as a plug connecting to conductor 542a, and conductor 540b functions as a plug connecting to conductor 542b.

[0135] 3, the conductor 610b is provided over the insulator 581, the insulator 611 is provided over the conductor 610b and the insulator 581, and the conductor 610 is provided over the insulator 611 to overlap with the conductor 610b. The conductors 610 and 610b function as electrodes of the capacitor 600, and the region of the insulator 611 between the conductor 610 and the conductor 610b functions as a dielectric of the capacitor 600.

[0136] In addition, in FIG. 3, the secondary battery 200 and the sensor element 660 are provided on an insulator 611 .

[0137] The sensor element 660 has a conductor 660a on an insulator 611, a conductor 660c on the conductor 660a, and a layer 660b sandwiched between the conductor 660a and the conductor 660c.

[0138] The conductor 610 and the conductor 660a are preferably made of the same material as the positive electrode current collector 103.

[0139] The sensor element 660 may be, for example, a pressure sensor, a piezoelectric sensor, an acceleration sensor, a gyro sensor, a magnetic sensor, an optical sensor, an infrared sensor, a distance sensor, a pulse sensor, an ultrasonic sensor, a touch sensor, or a fingerprint sensor.

[0140] The following is an example in which a piezoelectric sensor is used as the sensor element 660. By using a piezoelectric sensor, pressure, displacement, etc. can be detected.

[0141] It is preferable to use a titanium compound for the conductor 660a. Specifically, it is preferable to use titanium nitride, for example. Alternatively, it is preferable to use titanium. Using titanium nitride may increase the crystallinity of the layer 660b. Furthermore, a second conductive layer may be provided on the conductor 660a. For example, titanium and platinum on the titanium may be stacked. Using titanium and platinum on the titanium may increase the crystallinity of the layer 660b.

[0142] The layer 660b may be made of piezoelectric ceramics such as lead zirconate titanate and barium titanate. x Ti 1-x )O3. Barium titanate is sometimes expressed as BaTiO3.

[0143] A compound containing strontium (e.g., La) is used as a buffer layer between the conductor 660a and the layer 660b. 0.5 Sr 0.5 CoO3, SrTiO3, SrRuO3, etc.), lanthanum-containing compounds (LaNiO3), (Bi,La)4Ti3O 12 etc.), compounds containing yttrium (e.g. Y1Ba2Cu3O 7-x It is also possible to provide a laminate of one or more selected from the following:

[0144] As in the example configuration shown in FIG. 4, the transistor 500, which is an OS transistor, and the secondary battery 200 may be provided in a region sandwiched between the insulator 514 and the insulator 574.

[0145] The transistor 500 shown in FIG. 4 has a bottom-contact structure. In FIG. 4, a conductor 542a and a conductor 542b are provided over an insulator 524. The transistor 500 shown in FIG. 4 also includes an oxide 530 over the insulator 524, the conductor 542a, and the conductor 542b, an insulator 550 over the oxide 530, and a conductor 560 over the insulator 550. In FIG. 4, the conductor 560 and the conductor 503 overlap with each other, with the oxide 530 sandwiched therebetween. The insulator 520, the insulator 522, and the insulator 524 are provided between the conductor 503 and the oxide 530.

[0146] 4, the secondary battery 200 is provided on an insulator 524. An insulating layer 550 is provided on the protective layer 206 of the secondary battery 200, an insulator 580 is provided on the insulating layer 550, and an insulator 574 is provided on the insulator 580.

[0147] The conductor 542a and the conductor 542b function as a source electrode and a drain electrode of the transistor 500. The conductor 542a and the conductor 542b are preferably made using the same material as the positive electrode current collector 103.

[0148] 4 and FIG. 5 described later, the transistor 500 may have the structure of the transistor shown in FIG. 2 or the like.

[0149] 5, the secondary battery 200 may be provided over a substrate 599, an insulator 580b may be provided over the secondary battery 200, an insulator 514 may be provided over the insulator 580b, and the transistor 500 may be provided over the insulator 514. For materials that can be used for the insulator 580b, see the description of the insulator 580.

[0150] 6 , silicon, silicon germanium, or silicon carbide may be used as a substrate 599, the transistor 300 may be provided over the substrate 599, and an insulator 514, the transistor 500, a capacitor 600, a sensor element 660, and the like may be provided over the transistor 300. Part of the transistors included in the battery control circuit of one embodiment of the present invention may be formed using the transistor 300, for example.

[0151] 6 is provided on a substrate 599 and includes a conductor 316, an insulator 315, a semiconductor region 313 made of part of the substrate 599, a low-resistance region 314a, and a low-resistance region 314b. One of the low-resistance region 314a and the low-resistance region 314b functions as a source region, and the other functions as a drain region.

[0152] In the transistor 300, the top surface and the side surfaces in the channel width direction of the semiconductor region 313 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, and the on-state characteristics can be improved. Furthermore, the contribution of the electric field of the gate electrode can be increased, and the off-state characteristics of the transistor 300 can be improved.

[0153] The transistor 300 may be either a p-channel transistor or an n-channel transistor.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] The transistor 300 may be formed using an SOI (Silicon on Insulator) substrate or the like.

[0158] The SOI substrate may be a SIMOX (Separation by Implanted Oxygen) substrate formed by implanting oxygen ions into a mirror-polished wafer and then heating it at a high temperature to form an oxide layer to a certain depth from the surface and eliminate defects that have occurred in the surface layer, or an SOI substrate formed using the Smart Cut method or the ELTRAN (registered trademark: Epitaxial Layer Transfer) method, which cleaves a semiconductor substrate by utilizing the growth of microvoids formed by hydrogen ion implantation through heat treatment. A transistor formed using a single crystal substrate has a single crystal semiconductor in the channel formation region.

[0159] An insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order over the transistor 300.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] The insulator 324 is preferably a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 599 or the transistor 300 to a region where the transistor 500 is provided.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] Conductors 328, 330, and the like are embedded in insulators 320, 322, 324, and 326. 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, the wiring and the plug connecting to the wiring may be integral. That is, there are cases where a portion of a conductor functions as a wiring, and cases where a portion of a conductor functions as a plug.

[0168] 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. It is preferable to use a high-melting-point material such as tungsten or molybdenum, which has both heat resistance and conductivity, and tungsten is preferred. Alternatively, it is preferable to form the plug and wiring from a low-resistance conductive material such as aluminum or copper. Using a low-resistance conductive material can reduce the wiring resistance.

[0169] Note that, for example, the insulator 350 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 330 preferably includes a conductor having a barrier property against hydrogen. In particular, it is preferable that a conductor having a barrier property against hydrogen be formed in an opening of an insulator 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.

[0170] 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, it is preferable that the tantalum nitride layer having a barrier property against hydrogen be in contact with the insulator 350 having a barrier property against hydrogen.

[0171] An insulator 512 is provided on the insulator 350, and an insulator 514 is provided on the insulator 512. For materials that can be used for the insulator 512, see, for example, the insulator 326.

[0172] The transistor 500 shown in Figure 7A is a modified example of the transistor 500 shown in Figure 2, and Figure 7A is a cross-sectional view of the transistor 500 in the channel length direction, and Figure 7B is a cross-sectional view of the transistor 500 shown in Figure 7A in the channel width direction.

[0173] 7A differs from the transistor 500 shown in FIG. 2A in that it does not include oxide 530c. An insulator 550 is disposed on the bottom and side surfaces of an opening formed in insulator 580 between conductor 542a and conductor 542b, and a conductor 560 is disposed on the surface on which insulator 550 is formed. Because the transistor 500 shown in FIG. 7A does not include oxide 530c, parasitic capacitance between oxide 530c and conductor 560 can be eliminated via insulator 550.

[0174] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0175] (Embodiment 3) In order to increase the output voltage of a thin-film secondary battery, the secondary batteries can be connected in series. While the example of a secondary battery having one cell was shown in the second embodiment, this embodiment shows an example of fabricating a thin-film secondary battery in which a plurality of cells are connected in series.

[0176] Fig. 8A shows a top view of the first secondary battery immediately after its formation, and Fig. 8B shows a top view of two secondary batteries connected in series. Note that in Fig. 8A and Fig. 8B, the same reference numerals are used for the same parts as in Fig. 5A shown in Embodiment 2.

[0177] 8A shows the state immediately after the deposition of negative electrode current collector 205. The shape of the top surface of negative electrode current collector 205 differs from that of FIG. 5A. Negative electrode current collector 205 shown in FIG. 8A is in contact with a part of the side surface of the solid electrolyte layer and also with the insulating surface of the substrate.

[0178] 8B, a second negative electrode active material layer is formed on a region of the negative electrode current collector 205 that does not overlap with the first negative electrode active material layer. Then, a second solid electrolyte layer 213 is formed, and a second positive electrode active material layer and a second positive electrode current collector 215 are formed thereon. Finally, a protective layer 206 is formed.

[0179] FIG. 8B shows a configuration in which two solid-state secondary batteries are arranged on a plane and connected in series.

[0180] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0181] (Fourth embodiment) In this embodiment, an example of a power storage device of one embodiment of the present invention will be described.

[0182] <Example of an electricity storage device 1> 9 shows an example of a power storage device 90. The power storage device 90 shown in FIG. 9 includes a battery control circuit 91 and a battery pack 120. The battery control circuit 91 preferably includes a circuit using the above-described OS transistor.

[0183] The battery control circuit 91 includes a circuit 91a and a circuit 91b.

[0184] The circuit 91 a includes a cell balance circuit 130 , a detection circuit 185 , a detection circuit 186 , a detection circuit MSD, a detection circuit SD, a temperature sensor TS, and a logic circuit 182 .

[0185] The circuit 91b also includes a transistor 140 and a transistor 150. Various transistors can be used as the transistor 140 and the transistor 150. Note that, as shown in FIG. 9, each of the transistor 140 and the transistor 150 preferably includes a parasitic diode.

[0186] OS transistors can be used as transistors included in the cell balance circuit 130, the detection circuits 185, 186, the detection circuits MSD, the detection circuits SD, the temperature sensor TS, and the logic circuit 182 included in the circuit 91a.

[0187] Consider an example in which the transistors 140 and 150 included in the circuit 91b are transistors having single crystal silicon in their channel formation regions. In such a case, for example, the transistors 140 and 150 can be formed on a silicon substrate, and an OS transistor can be formed thereon by a deposition process, so that the circuits 91a and 91b can be formed on the same substrate. This can reduce costs, for example. It also enables circuit integration and reduces the circuit area. Furthermore, by stacking the circuits 91a and 91b on the same substrate, it is possible to reduce wiring resistance. Large currents may flow through the transistors 140 and 150, so it is preferable to reduce wiring resistance.

[0188] The battery pack 120 has a plurality of battery cells 121. FIG. 9 shows an example having n battery cells 121. The kth battery cell (k is an integer between 1 and n) may be referred to as battery cell 121(k). The battery pack 120 has a plurality of battery cells 121 electrically connected in series. Here, FIG. 9 shows an example in which the battery pack 120 has a plurality of battery cells 121 connected in series, but the battery pack 120 may have only one battery. Alternatively, the battery pack 120 may have a plurality of batteries connected in parallel.

[0189] Here, for example, a secondary battery described in the embodiment described later can be used as the battery cell. For example, a secondary battery having a wound battery element can be used. The battery cell preferably has an exterior body. For example, a cylindrical exterior body, a rectangular exterior body, or the like can be used. The exterior body can be made of a metal plate covered with an insulator, a metal film sandwiched between insulators, or the like. The battery cell has, for example, a pair of positive and negative electrodes. The battery cell may also have a terminal electrically connected to the positive electrode and a terminal electrically connected to the negative electrode. The battery cell may also have a part of the configuration of a battery control circuit of one embodiment of the present invention.

[0190] The cell balance circuit 130 has a function of controlling the charging of each battery cell 121 of the battery pack 120. The detection circuit 185 has a function of detecting overcharging and overdischarging of the battery pack 120. The detection circuit 186 has a function of detecting discharging overcurrent and charging overcurrent of the battery pack 120.

[0191] The detection circuit MSD has the function of detecting micro-short circuits.

[0192] A micro-short circuit refers to a tiny short circuit inside a secondary battery that does not short the positive and negative electrodes of the secondary battery to the point that charging and discharging are impossible, but rather refers to a phenomenon in which short-circuit current flows for a short period of time at the tiny short-circuited part.The cause of a micro-short circuit is thought to be that metal elements such as lithium and cobalt precipitate inside the battery when multiple charging and discharging cycles are performed, and the growth of the precipitates causes localized current concentration in parts of the positive electrode and negative electrode, resulting in parts of the separator not functioning or the generation of by-products.

[0193] The detection circuit SD detects, for example, a short circuit in a circuit that is operated using the battery pack 120. The detection circuit SD also detects, for example, the charging current and discharging current of the battery pack 120.

[0194] The battery control circuit 91 has terminals VC1 to VCN electrically connected to the positive electrodes of the n battery cells 121 included in the battery pack 120, and a terminal VSSS electrically connected to the negative electrode of the nth battery cell 121.

[0195] The logic circuit 182 has a function of controlling the transistors 140 and 150 in response to output signals from the detection circuits 185, 186, SD, MSD, and temperature sensor TS. The logic circuit 182 may also provide a signal to a charging circuit provided outside or inside the battery control circuit 91. In this case, for example, charging of a secondary battery is controlled in response to a signal provided from the logic circuit 182 to the charging circuit. Here, the charging circuit has a function of controlling the conditions for charging the battery, for example. Alternatively, the signal for controlling the conditions for charging the battery is provided to another circuit, such as a cell balance circuit, an overcharge detection circuit, the transistor 140, the transistor 150, or a circuit controlling the transistors 140 and 150, which are included in one embodiment of the present invention.

[0196] The transistors 140 and 150 have a function of controlling charging or discharging of the battery pack 120. As an example, the transistor 140 is controlled to be in a conductive state or a non-conductive state by a control signal T1 provided by the logic circuit 182, thereby controlling whether to charge the battery pack 120. The transistor 150 is controlled to be in a conductive state or a non-conductive state by a control signal T2 provided by the logic circuit 182, thereby controlling whether to discharge the battery pack 120. In the example shown in FIG. 9 , one of the source and drain of the transistor 140 is electrically connected to a terminal VSSS. The other of the source and drain of the transistor 140 is electrically connected to one of the source and drain of the transistor 150. The other of the source and drain of the transistor 150 is electrically connected to a terminal VM. The terminal VM is electrically connected to, for example, the negative pole of a charger. The terminal VM is also electrically connected to, for example, a load during discharging.

[0197] The battery control circuit 91 may have a function of observing the voltage value (monitor voltage) of each terminal of the battery cells 121 of the battery pack 120 and the current value (monitor current) flowing through the battery pack. For example, the on-current of the transistor 140 or the transistor 150 may be observed as the monitor current. Alternatively, a resistive element may be provided in series with the transistor 140 or the like, and the current value of the resistive element may be observed.

[0198] The temperature sensor TS may have a function of measuring the temperature of the battery cell 121 and controlling the charging and discharging of the battery cell based on the measured temperature. For example, the resistance of the secondary battery may increase at low temperatures, so the charging current density and the discharging current density may be reduced. The resistance of the secondary battery may decrease at high temperatures, so the discharging current density may be increased. If increasing the charging current at high temperatures is likely to cause deterioration of the characteristics of the secondary battery, the charging current may be controlled to a value that suppresses the deterioration. Data such as the charging conditions and the discharging conditions is preferably stored in a memory circuit or the like included in the battery control circuit 91 of one embodiment of the present invention. The temperature of the battery control circuit 91 or the battery pack 120 may increase due to charging. In such cases, it is preferable to control charging according to the measured temperature. For example, the charging current may be suppressed as the temperature increases.

[0199] The cell balance circuit 130, the detection circuits 185 and 186, the detection circuits MSD and SD, and the temperature sensor TS preferably have a memory element, which can store, for example, the upper and lower limit voltages of the battery, voltages corresponding to overcurrents, and voltages corresponding to temperatures.

[0200] 10A can be used as the memory element. The memory element 114 shown in FIG.

[0201] An OS transistor is preferably used as the transistor 162. In one embodiment of the present invention, by using the memory element 114 including an OS transistor, a desired voltage can be held in the memory element by utilizing the extremely low leakage current (hereinafter referred to as off-state current) that flows between the source and drain in an off state.

[0202] 10B differs from FIG. 10A in that the transistor 162 included in the memory element 114 has a second gate. The second gate may be called a back gate or a bottom gate. The second gate of the OS transistor will be described in detail in a later embodiment.

[0203] Next, the components of the cell balancing circuit 130 and the detection circuit 185 will be described.

[0204] FIG. 11 shows a cell balancing circuit 130a and a detection circuit 185a corresponding to one battery cell 121.

[0205] 9 has multiple cell balance circuits 130a, with one cell balance circuit 130a connected to one battery cell. In a configuration in which multiple battery cells 121 are connected in series, a cell balance circuit 130a and a transistor 132 are provided for each battery cell 121, and the transistors 132 are directly connected, thereby reducing variations in charging voltage between the battery cells 121 when charging the multiple battery cells 121 connected in series.

[0206] The detection circuit 185a shown in Fig. 11 includes a circuit 185c and a circuit 185d. The detection circuit 185c has a function of detecting overcharging, and the detection circuit 185d has a function of detecting overdischarging.

[0207] The detection circuit 185 shown in Fig. 9 has multiple detection circuits 185a, and one detection circuit 185a is connected to one battery cell. Alternatively, the detection circuit shown in Fig. 9 may be provided with one detection circuit 185a for a configuration in which multiple battery cells 121 are connected in series.

[0208] 11, a transistor 132 and a resistor element 131 are connected in series, with one of the source and drain of the transistor 132 electrically connected to the negative electrode of the battery cell 121 and the other electrically connected to one electrode of the resistor element. The other electrode of the resistor element is electrically connected to the positive electrode of the secondary battery.

[0209] Here, one of the source and drain of the transistor 132 may be electrically connected to the positive electrode of the battery cell 121, the other to one electrode of the resistor element 131, and the other electrode of the resistor element 131 to the negative electrode of the battery cell 121.

[0210] 11, the cell balance circuit 130a, the circuit 185c, and the circuit 185d each include a comparator 113 and a storage element 114. The storage element 114 includes a capacitor 161 and a transistor 162. The storage element 114 is electrically connected to one of the non-inverting input terminal or the inverting input terminal of the comparator 113 included in each of the cell balance circuit 130a, the circuit 185c, and the circuit 185d. In each of the storage elements 114, a common terminal, here the terminal VT, is electrically connected to one of the source and the drain of the transistor 162 included in each of the storage elements 114. In each of the storage elements 114, a terminal (the terminal SH6 in the cell balance circuit a130, the terminal SH1 in the circuit 185c, and the terminal SH2 in the circuit 185d) is electrically connected to the gate of the transistor 162 included in each of the storage elements 114.

[0211] 11, the cell balance circuit 130a is electrically connected to the positive and negative electrodes of the battery cell 121. The positive electrode of the battery cell 121 is electrically connected to a terminal VC1, and the negative electrode is electrically connected to a terminal VC2. In the cell balance circuit 130a, the other of the source and drain of the transistor 162 included in the storage element 114 is electrically connected to the inverting input terminal of the comparator 113. In the cell balance circuit 130a, the non-inverting input terminal of the comparator 113 is preferably electrically connected to the terminal VC1. Alternatively, as shown in FIG. 11, a voltage obtained by resistor-dividing between the terminals VC1 and VC2 may be applied to the non-inverting input terminal of the comparator 113. In the cell balance circuit 130a, a node connected to the other of the source and drain of the transistor 162 included in the storage element 114 is referred to as a node N6.

[0212] In FIG. 11, the detection circuit 185a is electrically connected to the positive and negative electrodes of the battery cell 121. In the circuit 185c, the other of the source and drain of the transistor 162 is electrically connected to the inverting input terminal of a comparator. In the circuit 185c, the non-inverting input terminal of the comparator 113 is preferably electrically connected to the terminal VC1. Alternatively, as shown in FIG. 11, the non-inverting input terminal of the comparator 113 may be supplied with a voltage obtained by resistor-dividing the voltage between the terminals VC1 and VC2. In the circuit 185c, the node connected to the other of the source and drain of the transistor 162 is referred to as node N1.

[0213] In the circuit 185d, the non-inverting input terminal of the comparator is electrically connected to the other of the source and drain of the transistor 162. In the circuit 185d, the inverting input terminal of the comparator 113 is preferably electrically connected to the terminal VC1. Alternatively, as shown in FIG. 11, a voltage obtained by resistor-dividing the voltage between the terminals VC1 and VC2 may be applied to the inverting input terminal of the comparator 113. In the circuit 185d, the node connected to the other of the source and drain of the transistor 162 is referred to as a node N2.

[0214] In the cell balance circuit 130a and the detection circuit 185a, the nodes (here, the nodes N6, N1, and N2) to which the other electrodes of the capacitors 161 included in the respective circuits are connected are maintained by turning off the transistors 162.

[0215] Terminal VT sequentially supplies an analog signal to cell balance circuit 130a, circuit 185c, and circuit 185d. Analog signals are sequentially supplied to node N6, node N1, and node N2 and held therein. After supplying an analog signal to a first node among nodes N6, N1, and N2, transistor 162 connected to the node is turned off, thereby holding the potential of the first node. Thereafter, a potential is supplied to a second node and held therein, and then a potential is supplied to a third node and held therein. The transistor 162 is turned on and off by signals supplied to terminals SH1, SH2, and SH6.

[0216] 11 is provided for each of the battery cells 121 in the battery pack 120, thereby making it possible to individually control the voltage difference between both ends (the difference in voltage between the positive electrode and the negative electrode) of each of the multiple battery cells 121. Furthermore, the cell balance circuit 130a can store in the memory element 114 a value that is preferable as the first upper limit voltage of the positive electrode for each battery cell 121.

[0217] The cell balance circuit 130a controls whether to turn on or off the transistor 132 depending on the relationship between the voltage of the positive electrode of the battery cell 121 and the voltage of the non-inverting input terminal of the comparator 113. By controlling the transistor 132, it is possible to adjust the ratio between the amount of current flowing through the resistance element 131 and the amount of current flowing through the battery cell 121. For example, when charging of the battery cell 121 is stopped, a current is passed through the resistance element 131 to limit the current flowing through the battery cell 121.

[0218] 9, a plurality of battery cells 121 are electrically connected in series between terminals VC1 and VSSS. The plurality of battery cells 121 are charged by passing a current between terminals VC1 and VSSS.

[0219] Consider a case where the positive electrode of one of the multiple battery cells 121 reaches a predetermined voltage and the current is limited. In such a case, by passing a current through the transistor 132 and the resistor element 131 connected in parallel to the battery cell, the current path between the terminal VC1 and the terminal VSSS is not interrupted, and the other battery cells 121 whose positive electrodes have not yet reached the predetermined voltage can continue to be charged. That is, for the battery cell 121 whose charging has been completed, the transistor 132 is turned on to stop charging, and for the battery cell 121 whose charging has not yet been completed, the transistor 132 is turned off to continue charging.

[0220] For example, if there is a variation in resistance among the battery cells 121, charging of a battery cell 121 with low resistance may be completed first, while charging of a battery cell 121 with higher resistance compared to other battery cells 121 may be insufficient. Here, insufficient charging refers to, for example, the voltage difference between the positive and negative electrodes being lower than the desired voltage. By using the cell balance circuit 130, the voltage of the positive electrode of the battery cell 121 during charging can be controlled based on the voltage of the negative electrode of each battery cell.

[0221] In the cell balance circuit of one embodiment of the present invention, the charging voltage, charging capacity, and the like of one battery cell or multiple battery cells can be controlled without using a circuit provided outside the battery control circuit 91, such as an arithmetic circuit such as an MPU or an MCU.

[0222] That is, by using N cell balance circuits 130a, it is possible to reduce variations in the state after charging of the multiple battery cells 121, for example, when fully charged. This may increase the capacity of the entire battery pack 120. Furthermore, increasing the capacity may reduce the number of charge / discharge cycles of the battery cells 121, which may increase the durability of the battery pack 120.

[0223] The circuit 185c can store, for each battery cell 121, a second upper limit voltage of the positive electrode when charging the battery cell 121 in the memory element 114. The second upper limit voltage may be referred to as an overcharge voltage. The circuit 185d can store, for each battery cell 121, a lower limit voltage of the positive electrode when discharging the battery cell 121 in the memory element 114. The lower limit voltage may be referred to as an overdischarge voltage.

[0224] The comparator constituting the detection circuit 185 may have different thresholds when the output changes from L level to H level and when the output changes from H level to L level, i.e., may be a hysteresis comparator. It is preferable that the storage element connected to the input part of the reference potential of the hysteresis comparator has a function of holding two thresholds.

[0225] The detection circuit 185 can detect overcharge and overdischarge of one or more battery cells and protect the battery cells without using a circuit provided outside the battery control circuit 91, such as an arithmetic circuit such as an MPU or MCU. When a voltage drop due to overdischarge is detected, the control circuit of one embodiment of the present invention cuts off the discharge current to prevent the voltage drop. If the discharge current is not sufficiently cut off, leakage current may occur, resulting in a voltage drop. A circuit configuration using power gating may suppress leakage current. Furthermore, a circuit configuration using OS transistors may suppress leakage current.

[0226] The upper limit voltage of a battery cell is controlled by a cell balancing circuit connected to the battery cell and by a circuit for detecting overcharge. The upper limit voltage detected by the cell balancing circuit is, for example, lower than the upper limit voltage detected by the circuit for detecting overcharge. Therefore, during the charging process, the cell balancing circuit detects that the battery cell has reached its upper limit voltage in a first step and changes the charging conditions. Here, for example, the charging current density is reduced. Alternatively, discharging may be started. Thereafter, as the charging voltage of the battery cell increases, if it is detected that the upper limit voltage detected by the circuit for detecting overcharge is reached, the charging conditions of the battery cell are changed in a second step. Here, for example, charging is stopped and discharging is started.

[0227] <Further Components of the Power Storage Device> An example of further components included in the power storage device of one embodiment of the present invention will be described below.

[0228] The battery control circuit 91 also has a terminal group AH, which may include one or more terminals.

[0229] 12, the terminal group AH is connected to the logic circuit 182. The terminal group AH preferably has a function of supplying signals to the logic circuit 182 and a function of supplying signals from the logic circuit 182 to a circuit provided outside the battery control circuit 91.

[0230] FIG. 12A illustrates an example of a logic circuit 182. The logic circuit 182 illustrated in FIG. 12A includes an interface circuit IF, a counter circuit CND, a latch circuit LTC, and a transistor 172. An OS transistor is preferably used as the transistor 172. Note that the configuration illustrated in FIG. 12A may be formed only with OS transistors included in the battery control circuit of one embodiment of the present invention, or only part of the configuration illustrated in FIG. 12A may be formed with OS transistors included in the battery control circuit of one embodiment of the present invention. When only part of the configuration illustrated in FIG. 12A is formed with OS transistors included in the battery control circuit of one embodiment of the present invention, the other part may be formed with transistors containing single crystal silicon, for example.

[0231] The interface circuit IF receives signals from output terminals OUT11 and OUT12 of the detection circuit 185, signals from output terminals OUT31 and OUT32 of the detection circuit 186, and a signal from output terminal OUT41 of the detection circuit SD. The output terminal OUT11 provides a signal corresponding to, for example, overcharging. The output terminal OUT12 provides a signal corresponding to, for example, overdischarging. The output terminal OUT31 provides a signal corresponding to, for example, an overcurrent during charging. The output terminal OUT32 provides a signal corresponding to, for example, an overcurrent during discharging.

[0232] The interface circuit IF applies a signal PG to the gate of the transistor 172 when detecting a signal that detects an abnormality, for example, a signal that corresponds to at least one of overcharge, overdischarge, and overcurrent.

[0233] The transistor 172 is connected to the counter circuit CND.

[0234] When the signal PG outputs a signal that turns on the transistor 172, more specifically, a high-potential signal, for example, the counter circuit CND operates the counter and the delay circuit. On the other hand, when the signal PG outputs a signal that turns off the transistor 172, more specifically, a low-potential signal, for example, the counter circuit CND can stop operation or put the counter circuit CND into a standby state. The interface circuit IF supplies the counter circuit CND and the latch circuit LTC with a signal res, which is a reset signal. The counter circuit CND is supplied with the signal res to start counting. The signal en is an enable signal. The counter circuit CND starts or stops operation according to the signal en.

[0235] When a signal detecting an abnormality is given to the interface circuit IF, the counter circuit CND counts for a certain period of time, and then a signal corresponding to the detected abnormality is given to the latch circuit LTC via the counter circuit CND.

[0236] The latch circuit LTC applies a signal to the gate of the transistor 140 or the transistor 150 in response to the detected abnormality, to turn the transistor off.

[0237] 13A shows an example of a circuit diagram of the detection circuit 186. The detection circuit 186 has two comparators 113.

[0238] A storage element 114 that holds a voltage corresponding to discharge overcurrent detection is electrically connected to the non-inverting input terminal of one comparator 113. A terminal SH3 is electrically connected to the gate of a transistor included in the storage element 114. A terminal SENS is electrically connected to the inverting input terminal. When an overcurrent is detected by the voltage applied to the inverting input terminal, the output from the output terminal OUT32 is inverted.

[0239] The terminal SENS is electrically connected to the non-inverting input terminal of the other comparator 113. A storage element 114 that holds a voltage corresponding to charging overcurrent detection is electrically connected to the inverting input terminal. A terminal SH4 is electrically connected to the gate of a transistor in the storage element 114. When an overcurrent is detected by the voltage applied to the non-inverting input terminal, the output from the output terminal OUT31 is inverted.

[0240] The temperature sensor TS has a function of measuring the temperature of the battery pack 120 or the power storage device 90 including the battery pack 120. Fig. 13B is a circuit diagram showing an example of the temperature sensor TS. Note that the circuit diagram shown in Fig. 13B may show only a portion of the circuit of the temperature sensor TS.

[0241] 13B, the temperature sensor TS has three comparators 113, and voltages VT (VT=Tm1, Tm2, ​​Tm3) corresponding to different temperatures are applied to the inverting input terminals of the respective comparators. Each applied voltage VT is stored in a storage element 114 electrically connected to the inverting input terminal. The voltages Tm1, Tm2, ​​Tm3 may be applied from the battery control circuit 91, for example.

[0242] A voltage corresponding to the measured temperature is applied to the input terminal Vt, which is applied to the non-inverting input terminals of the three comparators 113.

[0243] Corresponding to the comparison result between the voltage applied to the input terminal Vt and the voltage at the inverting input terminal of each comparator 113, a signal is output from the output terminal of each comparator (output terminal OUT51, output terminal OUT52, output terminal OUT53), and the temperature can be determined.

[0244] OS transistors have the property that their resistance decreases as the temperature rises. This property can be used to convert the ambient temperature into a voltage. This voltage can be applied to the input terminal Vt, for example.

[0245] The logic circuit 182 may be configured to detect the output of the temperature sensor TS, and if the temperature exceeds the operable temperature range of the battery pack 120, to make the transistor 140 and / or the transistor 150 non-conductive and stop charging and / or discharging.

[0246] <Battery cell> The battery cell 121 can be the secondary battery 200 shown in the previous embodiment.

[0247] <Transistor> In one embodiment of the present invention, a memory element including an OS transistor has an extremely low leakage current (hereinafter referred to as off-state current) flowing between the source and drain in an off state, and thus a reference voltage can be held in the memory element. In this case, the power supply to the memory element can be turned off, and therefore, by using a memory element including an OS transistor, the reference voltage can be held with extremely low power consumption.

[0248] Furthermore, a memory element having an OS transistor can hold an analog potential. For example, the voltage of a secondary battery can be held in the memory element without being converted into a digital value using an analog-to-digital converter. This eliminates the need for a converter, thereby reducing the circuit area.

[0249] In addition, in a memory element using an OS transistor, the reference voltage can be rewritten and read by charging or discharging an electric charge, so the monitor voltage can be acquired and read virtually unlimited times. Unlike magnetic memory or resistive memory, a memory element using an OS transistor does not involve structural changes at the atomic level, so it has excellent rewrite endurance. Furthermore, unlike flash memory, a memory element using an OS transistor does not exhibit instability due to an increase in electron trap centers even with repeated rewrite operations.

[0250] In addition, the OS transistor has characteristics such as extremely low off-state current and excellent switching characteristics even in a high-temperature environment, so that charging or discharging of the battery pack 120 can be controlled without malfunction even in a high-temperature environment.

[0251] Furthermore, memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, facilitating integration. Furthermore, OS transistors can be fabricated using the same manufacturing equipment as Si transistors, so they can be fabricated at low cost.

[0252] Furthermore, if an OS transistor includes a back gate electrode in addition to the gate, source, and drain electrodes, it can be a four-terminal semiconductor device. It can be configured as an electrical circuit network in which the input and output of signals flowing between the source and drain can be independently controlled depending on the voltage applied to the gate or back gate electrode. This allows circuit design to be carried out in the same way as with LSIs. Furthermore, OS transistors have superior electrical characteristics to Si transistors in high-temperature environments. Specifically, they have a large ratio of on-current to off-current, even at high temperatures of 100°C to 200°C, preferably 125°C to 150°C, allowing for good switching operation.

[0253] An OS transistor is preferably used as the transistor 162. Alternatively, an OS transistor may be used as the transistor 132.

[0254] The comparator may also be configured using an OS transistor.

[0255] This embodiment mode can be combined with the descriptions of other embodiment modes as appropriate.

[0256] (Embodiment 5) In this embodiment, an example of a detection circuit included in a battery control circuit according to one embodiment of the present invention will be described. A semiconductor device according to one embodiment of the present invention has a function of detecting instantaneous potential fluctuations (here, potential drops) due to micro-short circuits by sampling (acquiring) a potential between the positive and negative electrodes of a secondary battery during charging and discharging at predetermined time intervals and comparing the sampled potential with the potential between the positive and negative electrodes after sampling. Repeating sampling at predetermined time intervals allows the semiconductor device to respond to potential fluctuations of the secondary battery during charging and discharging, and the semiconductor device can be operated using the potential between the positive and negative electrodes of the secondary battery.

[0257] In this embodiment, potential fluctuations of the secondary battery and the semiconductor device during charging will be described using timing charts, etc. Potential fluctuations during discharging will be easily understood by those skilled in the art, and therefore will not be described here.

[0258] <An example of a detection circuit> 14A is a circuit diagram showing an example configuration of the detection circuit MSD. The detection circuit MSD has transistors 11 to 15, a capacitance element C11, and a comparator 50. In the drawings described in this specification, arrows or lines indicate the flow of main signals, and power lines and the like may be omitted. A hysteresis comparator may be used as the comparator 50 of the detection circuit MSD. The detection circuit MSD may perform detection on multiple battery cells connected in series, or may perform detection on each battery cell individually.

[0259] The detection circuit MSD shown in FIG. 14A also includes a terminal VC1, a wiring VB1_IN to which a predetermined potential VB1 is supplied, a wiring VB2_IN to which a predetermined potential VB2 is supplied, a wiring SH_IN to which a sampling signal is supplied, and an output terminal S_OUT.

[0260] Here, the predetermined potential VB1 is higher than the predetermined potential VB2, and the predetermined potential VB2 is higher than the potential of the terminal VSSS.

[0261] FIG. 14B differs from FIG. 14A in that the transistors 11 to 15 of the detection circuit MSD have second gates.

[0262] 14C differs from FIG. 14B in that it includes a terminal VSSS, a memory element 114 connected to a wiring VB1_IN, and a memory element 114 connected to a wiring VB2_IN. In FIG. 14C, one of the source and drain of the transistor 11, one of the source and drain of the transistor 13, and one electrode of the capacitor C11 are electrically connected to the terminal VSSS. The potentials VB1 and VB2 are applied to the wiring VB1_IN and the wiring VB2_IN, respectively, through the memory element 114, so that the potentials applied by the memory element 114 can be held. Therefore, the voltage generating circuits that supply the potentials VB1 and VB2 can be turned off or put into a standby state.

[0263] The transistors 11 to 15 are n-channel transistors. In this specification and the like, an example in which the detection circuit MSD is configured using n-channel transistors is shown, but p-channel transistors may also be used. Since it is easy for a person skilled in the art to understand how to change a circuit diagram configured using n-channel transistors to p-channel transistors, a description thereof will be omitted.

[0264] In the detection circuit MSD, one of the source and drain of transistor 11 is electrically connected to terminal VSSS, the other of the source and drain of transistor 11 is electrically connected to one of the source and drain of transistor 12 and one of the source and drain of transistor 15, the gate of transistor 11 is electrically connected to wiring VB1_IN, and the other of the source and drain of transistor 12 and the gate of transistor 12 are electrically connected to terminal VC1.

[0265] One of the source and drain of transistor 13 is electrically connected to terminal VSSS, the other of the source and drain of transistor 13 is electrically connected to one of the source and drain of transistor 14 and the inverting input terminal of comparator 50, the gate of transistor 13 is electrically connected to wiring VB2_IN, and the other of the source and drain of transistor 14 and the gate of transistor 14 are electrically connected to terminal VC1.

[0266] The other of the source and drain of the transistor 15 is electrically connected to the other terminal of the capacitor C11 and the non-inverting input terminal of the comparator 50, the gate of the transistor 15 is electrically connected to the wiring SH_IN, one terminal of the capacitor C11 is electrically connected to the terminal VSSS, and the output terminal of the comparator 50 is electrically connected to the output terminal S_OUT. Note that the one terminal of the capacitor C11 may be electrically connected to a wiring other than the terminal VSSS as long as it is a wiring to which a predetermined potential is supplied.

[0267] Here, the connection portion where the other of the source and drain of transistor 11, one of the source and drain of transistor 12, and one of the source and drain of transistor 15 are electrically connected is referred to as node N11, the connection portion where the other of the source and drain of transistor 13, one of the source and drain of transistor 14, and the inverting input terminal of comparator 50 are electrically connected is referred to as node N12, and the connection portion where the other of the source and drain of transistor 15, the other terminal of capacitor C11, and the non-inverting input terminal of comparator 50 are electrically connected is referred to as node N13.

[0268] Furthermore, transistors 11 and 12 form a first source follower, and transistors 13 and 14 form a second source follower. That is, the gate of transistor 11 corresponds to the input of the first source follower, and the first source follower outputs to node N11. The gate of transistor 13 corresponds to the input of the second source follower, and the second source follower outputs to node N12.

[0269] An example of the operation of the detection circuit MSD will be described using the circuit shown in FIG. 14C.

[0270] When charging of the battery pack begins, the sampling signal supplied to the line SH_IN goes high at predetermined time intervals. A potential higher than the potential VB2 is supplied as the potential VB1. As charging progresses, the potentials of the nodes N11 and N12 rise.

[0271] When the positive electrode potential drops instantaneously due to the occurrence of a micro-short circuit, the potentials of nodes N11 and N12 also drop instantaneously. On the other hand, when the sampling signal applied to line SH_IN is at a low level, the potential of node N13 is not affected by the potential of node N11, and the potential of node N12 becomes lower than the potential of node N13. This inverts the output of comparator 50, and a micro-short circuit is detected.

[0272] Furthermore, to improve the accuracy of detecting micro-short circuits, the voltage of the secondary battery may be converted into digital data using an analog-to-digital conversion circuit, and a processor unit or the like may be used to perform calculations based on the digital data, analyze the charging waveform or discharging waveform, and detect or predict micro-short circuits. For example, in the charging waveform or discharging waveform, the voltage error displacement at each time step is used to detect or predict micro-short circuits. The voltage error displacement can be found by calculating the voltage error and calculating the difference from the previous step.

[0273] To improve the accuracy of detecting micro-shorts, a neural network may be used.

[0274] A neural network is a method and neural network processing performed by a neural network unit (including, for example, a CPU (Central Processor Unit), GPU (Graphics Processing Unit), APU (Accelerated Processing Unit), memory, etc.). Note that an APU refers to a chip that integrates a CPU and GPU into one.

[0275] The discharge of secondary batteries installed in devices is random because it tends to depend on how the user uses them, but the charging conditions are fixed for charging, so the charging curve is easier to predict than the discharge curve. By using a certain number of charging curves as learning data, accurate values ​​can be predicted using a neural network. Once the charging curve is obtained, the SOC (State of charge) can be obtained using the neural network. A microprocessor, for example, can be used to calculate the neural network.

[0276] Specifically, the various data obtained is evaluated and learned using machine learning or artificial intelligence, the predicted degree of deterioration of the secondary battery is analyzed, and if an abnormality is detected, charging of the secondary battery is stopped or the current density of constant current charging is adjusted.

[0277] For example, in an electric vehicle, learning data can be acquired while the vehicle is running, allowing the deterioration state of the secondary battery to be ascertained. A neural network is used to predict the deterioration state of the secondary battery. The neural network can be configured as a neural network with multiple hidden layers, i.e., a deep neural network. Learning in a deep neural network is sometimes called deep learning.

[0278] Machine learning first extracts feature values ​​from training data. Relative changes over time are extracted as feature values, and a neural network is trained based on the extracted feature values. The training means can train the neural network based on different training patterns for each time interval. The connection weights applied to the neural network can be updated according to the training results based on the training data.

[0279] As a method for estimating the state of charge of a secondary battery using a neural network, the state of charge can also be obtained by performing calculation processing using a regression model, for example, a Kalman filter.

[0280] The Kalman filter is a type of infinite impulse response filter. Multiple regression analysis is a type of multivariate analysis in which multiple independent variables are used in regression analysis. Examples of multiple regression analysis include the least squares method. While regression analysis requires a large number of time series of observed values, the Kalman filter has the advantage of being able to sequentially obtain optimal correction coefficients as long as a certain amount of data has been accumulated. The Kalman filter can also be applied to non-stationary time series.

[0281] A nonlinear Kalman filter (specifically, an unscented Kalman filter (UKF)) can be used to estimate the internal resistance and state of charge (SOC) of a secondary battery. An extended Kalman filter (EKF) can also be used. SOC indicates the state of charge (also called the charge rate), with 100% being fully charged and 0% being fully discharged.

[0282] The initial parameters obtained by the optimization algorithm are collected every n cycles (n is an integer, for example, 50), and this data set is used as training data for neural network processing, enabling highly accurate estimation of the SOC.

[0283] The learning system includes a training data creation device and a learning device. The training data creation device creates training data used by the learning device when learning. Training data includes data whose recognition target is the same as the data to be processed and an evaluation of the label corresponding to the data. The training data creation device includes an input data acquisition unit, an evaluation acquisition unit, and a training data creation unit. The input data acquisition unit may acquire training input data from data stored in a storage device or via the Internet. The input data is data used for training and includes the current and voltage values ​​of a secondary battery. Furthermore, training data does not have to be actual measurement data. Initial parameters may be conditioned to provide diversity, and data close to actual measurements may be created. A predetermined characteristic database of such data may then be used as training data for neural network processing to estimate the state of charge (SOC). By creating data close to actual measurements based on the charge / discharge characteristics of a certain battery and then using the predetermined characteristic database as training data for neural network processing, SOC estimation for the same type of battery can also be performed efficiently.

[0284] As deterioration of a secondary battery progresses, a significant change in the FCC of the initial parameter may result in an error in the SOC. Therefore, the initial parameters used in the calculation for estimating the SOC may be updated. The updated initial parameters are calculated using an optimization algorithm based on data on charge / discharge characteristics measured in advance. By performing calculations using a regression model, such as a Kalman filter, using the updated initial parameters, it is possible to estimate the SOC with high accuracy even after deterioration. In this specification, calculations using a Kalman filter are also referred to as Kalman filter processing.

[0285] The timing for updating the initial parameters may be arbitrary, but in order to estimate the SOC with high accuracy, it is preferable to update the parameters frequently, and it is preferable to update them regularly and continuously. Note that when the temperature of the secondary battery is high, a high SOC may lead to accelerated deterioration. In such cases, it is preferable to suppress deterioration of the secondary battery by discharging the secondary battery and lowering the SOC.

[0286] This embodiment mode can be combined with the descriptions of other embodiment modes as appropriate.

[0287] (Embodiment 6) This embodiment shows an example of the configuration of a comparator.

[0288] 15A shows an example of the configuration of the comparator 50 described in the previous embodiment. The comparator 50 includes transistors 21 to 25. The comparator 50 also includes a wiring VBM_IN to which a negative electrode potential of the secondary battery is supplied, a wiring VBP_IN to which a positive electrode potential VBP of the secondary battery is supplied, a wiring VB3_IN to which a predetermined potential VB3 is supplied, an input terminal CP1_IN, an input terminal CM1_IN, an output terminal CP1_OUT, and an output terminal CM1_OUT.

[0289] When the comparator 50 in FIG. 15A is applied to the cell balance circuit 130 and the detection circuit 185, for example, the potential is connected to the wiring VBP_IN from the terminal VC1, and the potential is connected to the wiring VBM_IN from the terminal VC2.

[0290] Here, the predetermined potential VB3 is a potential higher than the negative electrode potential VBM, and in the comparator 50, the positive electrode potential VBP is a high power supply potential, and the negative electrode potential VBM is a low power supply potential.

[0291] In the comparator 50, one of the source and drain of the transistor 21 is electrically connected to the wiring VBM_IN, the other of the source and drain of the transistor 21 is electrically connected to one of the source and drain of the transistor 22 and one of the source and drain of the transistor 24, and the gate of the transistor 21 is electrically connected to the wiring VB3_IN.

[0292] The other of the source and drain of transistor 22 is electrically connected to one of the source and drain of transistor 23 and the output terminal CM1_OUT, the other of the source and drain of transistor 23 and the gate of transistor 23 are electrically connected to wiring VBP_IN, and the gate of transistor 22 is electrically connected to the input terminal CP1_IN.

[0293] The other of the source and drain of transistor 24 is electrically connected to one of the source and drain of transistor 25 and the output terminal CP1_OUT, the other of the source and drain of transistor 25 and the gate of transistor 25 are electrically connected to wiring VBP_IN, and the gate of transistor 24 is electrically connected to the input terminal CM1_IN.

[0294] 15A may be connected in parallel to each other and used as comparator 50. That is, the output of the comparator shown in FIG. 15A may be input to comparator 50 at the next stage, and multiple comparators may be connected and used.

[0295] 15A may have a back gate as shown in FIG. 15B. A voltage can be applied to the back gate and held by a holding circuit 99. In the holding circuit 99, one of the source and drain of the transistor 99a is electrically connected to the terminal SH_99, and the other is electrically connected to the back gate of the transistor 22, the back gate of the transistor 24, and one electrode of the capacitor 99b.

[0296] In the holding circuit 99, a voltage to be applied to the back gate is applied to the terminal SH_99, and the transistor 99a is turned on to apply the voltage to the back gates of the transistors 22 and 24. Then, the transistor 99a is turned off, thereby holding the voltage of the back gate. By using an OS transistor as the transistor 99a, a leakage current (hereinafter referred to as off current) that flows between the source and drain when the transistor 99a is off is extremely low, and therefore a desired voltage can be held in the back gates of the transistors 22 and 24.

[0297] The voltage applied to the terminal SH_99 is, for example, applied from a secondary battery 99f to a conversion circuit 99e, passed through the conversion circuit 99e, and then applied to a boost circuit 99c, where it is boosted and then applied to the terminal SH_99. A signal is applied to the boost circuit 99c from a clock generation circuit 99d. The conversion circuit 99e, the boost circuit 99c, and the clock generation circuit 99d can be configured using OS transistors.

[0298] In the power storage device of one embodiment of the present invention, two or more secondary batteries may be provided over the substrate. For example, a secondary battery 99f may be provided in addition to a secondary battery (referred to as a first secondary battery here) for sharing power from the power storage device with electronic devices or the like (described later). In such a case, the capacity of the secondary battery 99f may be smaller than that of the first secondary battery, for example, 0.1 times or less or 0.01 times or less.

[0299] FIG. 12B shows an example of the configuration of a clock buffer circuit 99g to which signals from the booster circuit 99c and the clock generating circuit 99d are applied.

[0300] (clock buffer circuit) The clock buffer circuit 99g includes inverters 70 to 75 and terminals a1 to a3. The clock buffer circuit 99g has a function of generating signals CK1_cp and CKB1_cp from the signal CLK_cp. The terminal a1 is an input terminal for the signal CLK_cp, and the terminals a2 and a3 are output terminals for the signals CK1_cp and CKB1_cp. The signal CLK_cp is a clock signal. The power storage device of one embodiment of the present invention may have a function of dividing the frequency of a reference clock signal to generate the signal CLK_cp. The signals CK1_cp and CKB1_cp are complementary clock signals.

[0301] (Boost circuit) The boost circuit 99c is a step-down charge pump and has a function of stepping down the potential GND to generate the potential Vcp1. Note that the input potential is not limited to the potential GND. The boost circuit 99c includes transistors MN61 to MN65 and capacitance elements C61 to C65. The boost circuit 99c has five stages, but the number of stages is not limited to this.

[0302] This embodiment mode can be combined with the descriptions of other embodiment modes as appropriate.

[0303] (Embodiment 7) In this embodiment, examples of electronic devices using a power storage device of one embodiment of the present invention will be described with reference to FIGS. 16A to 17C. In the power storage device of one embodiment of the present invention, a secondary battery and a battery control circuit can be provided over the same substrate, which enables miniaturization of the electronic device and improves the safety of the secondary battery. Furthermore, the power storage device of one embodiment of the present invention has a thin profile because it can be provided over a substrate.

[0304] 16 illustrates an IC card as an example of an application using a power storage device of one embodiment of the present invention. Power obtained by radio waves 3005 can be charged into a thin-film secondary battery 3001 included in the power storage device. An antenna, an IC 3004, and the thin-film secondary battery 3001 are arranged inside the IC card 3000. An ID 3002 and a photo 3003 of a worker wearing the management badge are displayed on the IC card 3000. A signal such as an authentication signal can also be transmitted from the antenna using the power charged in the thin-film secondary battery 3001.

[0305] The power storage device of one embodiment of the present invention may include a display device for displaying the ID 3002 and the photograph 3003. The display device includes, for example, a display unit and a driver circuit that supplies an image signal to the display unit. The driver circuit can include, for example, a plurality of OS transistors described in the above embodiment. In the power storage device of one embodiment of the present invention, a secondary battery and an OS transistor can be provided over the same substrate. Therefore, by providing the driver circuit using an OS transistor, the secondary battery and the driver circuit, or at least a part of the driver circuit, can be provided over the same substrate. Therefore, IC cards can be made thinner, lighter, and more durable.

[0306] For example, an active matrix display device may be provided as the display device. 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.

[0307] Since a plastic substrate is used in an IC card, an organic EL display device using a flexible substrate is preferred.

[0308] A solar cell may be provided in place of the photo 3003. When irradiated with external light, the solar cell absorbs the light, generates electricity, and the electricity can be used to charge the thin-film secondary battery 3001.

[0309] 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.

[0310] Figure 17A shows an example of a wearable device. The wearable device uses a secondary battery as a power source. Furthermore, in order to improve splash-proof, water-resistant, or dust-proof performance when used at home or outdoors, there is a demand for a wearable device that can be charged wirelessly as well as via a wired connection with an exposed connector.

[0311] For example, the power storage device of one embodiment of the present invention can be mounted on an eyeglasses-type device 400 as shown in FIG. 17A. The eyeglasses-type device 400 includes a frame 400a and a display portion 400b. By mounting a power storage device including a secondary battery on temple portions of the curved frame 400a, the eyeglasses-type device 400 can be lightweight, well-balanced in weight, and has a long continuous use time. By including the secondary battery of one embodiment of the present invention, a space-saving configuration can be realized that accompanies a miniaturized housing.

[0312] Furthermore, a secondary battery according to one embodiment of the present invention can be mounted on a headset-type device 401. The headset-type device 401 includes at least a microphone unit 401a, a flexible pipe 401b, and an earphone unit 401c. A secondary battery can be provided in the flexible pipe 401b or the earphone unit 401c. By including a secondary battery according to one embodiment of the present invention, a configuration that can accommodate space savings due to a smaller housing can be realized.

[0313] Furthermore, the secondary battery of one embodiment of the present invention can be mounted on a device 402 that can be directly attached to the body. A power storage device 402b including a secondary battery can be provided in a thin housing 402a of the device 402. By including the secondary battery of one embodiment of the present invention, a space-saving configuration can be realized that accompanies a miniaturized housing.

[0314] Furthermore, the power storage device of one embodiment of the present invention can be mounted on a device 403 that can be attached to clothing. A power storage device 403b equipped with a secondary battery can be provided in a thin housing 403a of the device 403. By providing the secondary battery of one embodiment of the present invention, a space-saving configuration can be realized that accompanies a miniaturized housing.

[0315] Furthermore, the power storage device of one embodiment of the present invention can be mounted on the belt-type device 406. The belt-type device 406 includes a belt portion 406a and a wireless power receiving portion 406b, and a power storage device including a secondary battery can be mounted inside the belt portion 406a. By including the power storage device of one embodiment of the present invention, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0316] Furthermore, the power storage device of one embodiment of the present invention can be mounted on a wristwatch device 405. The wristwatch device 405 has a display portion 405a and a belt portion 405b, and the power storage device can be provided on the display portion 405a or the belt portion 405b. By providing the power storage device of one embodiment of the present invention, a structure that can accommodate space saving due to miniaturization of the housing can be realized.

[0317] The display unit 405a can display not only the time but also various other information such as incoming emails and phone calls.

[0318] 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 to manage the user's health.

[0319] FIG. 17B shows a perspective view of the wristwatch type device 405 removed from the wrist.

[0320] 17C shows a side view of the display portion 405. The display portion 405a includes a built-in power storage device 913 having a secondary battery. The power storage device 913 is provided at a position overlapping the display portion 405a, and is small and lightweight.

[0321] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0322] (Embodiment 8) In this embodiment, electronic devices using a power storage device of one embodiment of the present invention will be described with reference to FIGS. 18A and 18B and 19A to 19D. In the power storage device of one embodiment of the present invention, a secondary battery and a battery control circuit can be provided over the same substrate, which enables the electronic device to be miniaturized and improves the safety of the secondary battery. Furthermore, the power storage device of one embodiment of the present invention has a thin profile because it can be provided over a substrate.

[0323] 18A shows a perspective view of a wristwatch-type mobile information terminal (also called a smart watch (registered trademark)) 700. Mobile information terminal 700 has a housing 701, a display panel 702, a clasp 703, bands 705A and 705B, and operation buttons 711 and 712.

[0324] For example, an active matrix display device may be provided as the display panel. 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. Alternatively, an organic EL display device using a flexible substrate may be used.

[0325] The display device includes a display panel and a driver circuit that supplies an image signal to the display panel. The driver circuit can include, for example, a plurality of OS transistors described in the above embodiment. In a power storage device according to one embodiment of the present invention, a secondary battery and an OS transistor can be provided over the same substrate. Therefore, by providing the driver circuit using an OS transistor, the secondary battery and the driver circuit, or at least a part of the driver circuit, can be provided over the same substrate. Therefore, the portable information terminal according to one embodiment of the present invention can be made smaller, lighter, and more durable.

[0326] A display panel 702 mounted on a housing 701 that also serves as a bezel has a rectangular display area. The display area has a curved surface. The display panel 702 is preferably flexible. The display area may be non-rectangular.

[0327] Band 705A and band 705B are connected to housing 701. Clasp 703 is connected to band 705A. Band 705A and housing 701 are connected via a pin, for example, so that the connection can rotate. The same applies to the connections between band 705B and housing 701, and between band 705A and clasp 703.

[0328] FIG. 18B shows a perspective view of the band 705A. The band 705A has a power storage device. For example, the power storage device described in the previous embodiment can be used as the power storage device. The power storage device is embedded inside the band 705A, and a positive electrode lead 751 and a negative electrode lead 752 of a secondary battery included in the power storage device each partially protrude from the band 705A (see FIG. 18B). The positive electrode lead 751 and the negative electrode lead 752 are electrically connected to the display panel 702. Note that the pins may also function as electrodes. Specifically, the positive electrode lead 751 and the display panel 702, and the negative electrode lead 752 and the display panel 702 may each be electrically connected via a pin that connects the band 705A to the housing 701. This simplifies the configuration at the connection between the band 705A and the housing 701.

[0329] The power storage device is flexible. Therefore, the band 705A can be manufactured by integrally forming it with the power storage device. For example, the power storage device is placed in a mold corresponding to the outer shape of the band 705A, and the material for the band 705A is poured into the mold and cured, thereby manufacturing the band 705A shown in FIG. 18B.

[0330] When a rubber material is used as the material for the band 705A, the rubber is hardened by heat treatment. For example, when fluororubber is used as the rubber material, it is hardened by heat treatment at 170°C for 10 minutes. When silicone rubber is used as the rubber material, it is hardened by heat treatment at 150°C for 10 minutes.

[0331] Materials used for the band 705A include fluororubber, silicone rubber, fluorosilicone rubber, and urethane rubber.

[0332] 18A can have various functions. For example, it can have a function of displaying various information (still images, videos, text images, etc.) in a display area, a touch panel function, a function of displaying a calendar, date or time, etc., a function of controlling processing by various software (programs), a wireless communication function, a function of connecting to various computer networks using the wireless communication function, a function of transmitting or receiving various data using the wireless communication function, a function of reading out programs or data recorded on a recording medium and displaying them in a display area, etc.

[0333] The housing 701 may also include a speaker, a sensor (including a function of measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone, etc. The portable information terminal 700 can be manufactured by using a light-emitting element for the display panel 702.

[0334] 18A shows an example in which the power storage device is included in the band 705A, the power storage device may be included in the band 705B. The same material as that of the band 705A can be used for the band 705B.

[0335] 19A shows an example of a cleaning robot. The cleaning robot 6300 has a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side, a brush 6304, an operation button 6305, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0336] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 to determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, when an object that may become entangled in the brush 6304, such as a wire, is detected through image analysis, the cleaning robot 6300 can stop rotation of the brush 6304. The cleaning robot 6300 includes a power storage device according to one embodiment of the present invention and a semiconductor device or an electronic component. By using the power storage device according to one embodiment of the present invention in the cleaning robot 6300, the cleaning robot 6300 can be a highly reliable electronic device with a long operating time.

[0337] Fig. 19B shows an example of a robot. The robot 6400 shown in Fig. 19B includes a power storage device 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a computing device, etc.

[0338] The microphone 6402 has a function of detecting the user's voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0339] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0340] The upper camera 6403 and the lower camera 6406 have the function of capturing images of the surroundings of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

[0341] The robot 6400 includes a power storage device 6409 according to one embodiment of the present invention and electronic components inside the robot 6400. By using the power storage device according to one embodiment of the present invention in the robot 6400, the robot 6400 can be a highly reliable electronic device with a long operating time.

[0342] Fig. 19C shows an example of an aircraft 6500. The aircraft 6500 includes a propeller 6501, a camera 6502, a power storage device 6503, and the like, and has the ability to fly autonomously.

[0343] For example, image data captured by the camera 6502 is stored in the electronic component 6504. The electronic component 6504 can analyze the image data and detect the presence or absence of an obstacle when moving. The power storage device 6503 can estimate the remaining charge from a change in the power storage capacity of the secondary battery. The flying object 6500 includes the power storage device 6503 according to one embodiment of the present invention. By using the power storage device according to one embodiment of the present invention in the flying object 6500, the flying object 6500 can be an electronic device with long operating time and high reliability.

[0344] 19D illustrates an example of an automobile. The automobile 7160 includes a power storage device 7161, an engine, tires, brakes, a steering device, a camera, and the like. The automobile 7160 includes the power storage device 7161 according to one embodiment of the present invention. By using the power storage device according to one embodiment of the present invention in the automobile 7160, the weight of the vehicle can be reduced. Furthermore, the volume of the secondary battery in the vehicle can be reduced. Furthermore, the automobile 7160 can have a long cruising distance, high safety, and high reliability.

[0345] This embodiment mode can be implemented in appropriate combination with other embodiment modes. [Explanation of symbols]

[0346] 11: transistor, 12: transistor, 13: transistor, 14: transistor, 15: transistor, 21: transistor, 22: transistor, 23: transistor, 24: transistor, 25: transistor, 50: comparator, 90: power storage device, 91: battery control circuit, 91a: circuit, 91b: circuit, 99: holding circuit, 99a: transistor, 99b: transistor, 100: positive electrode, 101: positive electrode active material layer, 103: positive electrode current collector, 110: substrate, 113: comparator, 114: memory element, 120: battery pack, 121: battery cell, 130: Cell balance circuit, 130a: cell balance circuit, 131: resistive element, 132: transistor, 140: transistor, 150: transistor, 161: capacitive element, 162: transistor, 172: transistor, 182: logic circuit, 185: detection circuit, 185a: detection circuit, 185c: circuit, 185d: circuit, 186: detection circuit, 200: secondary battery, 203: solid electrolyte layer, 204: negative electrode active material layer, 205: negative electrode current collector, 206: protective layer, 210: negative electrode, 213: solid electrolyte layer, 215: positive electrode current collector, 300: transistor, 313: semiconductor region, 31 4a: low resistance region, 314b: low resistance region, 315: insulator, 316: conductor, 320: insulator, 322: insulator, 324: insulator, 326: insulator, 328: conductor, 330: conductor, 350: insulator, 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: power storage device, 403: device, 403a: housing, 403b: power storage device, 405: wristwatch-type device, 405a: Display unit, 405b: belt unit, 406: belt-type device, 406a: belt unit, 406b: wireless power receiving unit, 500: transistor, 503: conductor, 512: insulator, 514: insulator, 520: insulator, 522: insulator, 524: insulator, 530: oxide, 530a: oxide, 530b: oxide, 530c: oxide, 540a: conductor, 540b: conductor, 542a: conductor, 542b: conductor, 543a: region, 543b: region, 544: insulator, 550: insulator, 560: conductor, 560a: conductor, 560b: conductor, 574: insulator,580: insulator, 580b: insulator, 581: insulator, 599: substrate, 600: capacitance element, 610: conductor, 610b: conductor, 611: insulator, 660: sensor element, 660a: conductor, 660b: layer, 660c: conductor, 700: mobile information terminal, 701: housing, 702: display panel, 703: clasp, 705A: band, 705B: band, 711: operation button, 712: operation button, 751: positive electrode lead, 752: negative electrode lead, 913: power storage device, 3000: IC card, 3001: thin film secondary battery, 3002: ID, 3003: photograph, 3004: I C, 3005: radio waves, 6300: cleaning robot, 6301: housing, 6302: display unit, 6303: camera, 6304: brush, 6305: operation button, 6310: dust, 6400: robot, 6401: illuminance sensor, 6402: microphone, 6403: upper camera, 6404: speaker, 6405: display unit, 6406: lower camera, 6407: obstacle sensor, 6408: moving mechanism, 6409: power storage device, 6500: flying object, 6501: propeller, 6502: camera, 6503: power storage device, 6504: electronic component, 7160: automobile, 7161: power storage device,

Claims

1. a first battery cell, a comparison circuit, a control circuit, a first transistor, and a capacitance element; the comparison circuit has a first input terminal, a second input terminal, an output terminal, and a second transistor; one of the source and the drain of the first transistor is electrically connected to the second input terminal; the other of the source and the drain of the first transistor is electrically connected to one electrode of the capacitance element; the first transistor has an oxide semiconductor in a channel formation region; the second transistor has an oxide semiconductor in a channel formation region; a first electrode of the first battery cell electrically connected to a gate electrode of the second transistor and the first input terminal; the comparison circuit has a function of outputting a first signal corresponding to a comparison result between the potential of the first electrode and a desired reference potential from the output terminal to the control circuit; The control circuit is a power storage device having a function of controlling charging of the first battery cell in response to the first signal.

2. In claim 1, The output terminal of the power storage device is electrically connected to the source or drain of the second transistor.

3. In claim 1, a third transistor; the third transistor has an oxide semiconductor in a channel formation region; The output terminal of the power storage device is electrically connected to the source or drain of the third transistor.

Images