Battery pack

Abstract

To provide a semiconductor device with reduced power consumption.SOLUTION: A voltage is detected by switching potentials of two nodes with three transistors. One of a source and a drain of a first transistor is electrically connected with a first terminal, and the other is electrically connected with a non-inverted input of a comparator via a first node. One of a source and a drain of a second transistor is electrically connected with a second terminal, and the other is electrically connected with one of a source and a drain of a third transistor via a second node. The other of the source and the drain of the third transistor is electrically connected with a third terminal. A first capacitive element is provided between the first node and the second node. An inverted input of the comparator is electrically connected with a fourth terminal, and an output of the comparator is electrically connected with a fifth terminal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One embodiment of the present invention relates to a semiconductor device, a battery pack, and an electronic device.

[0002] Note that one aspect of the present invention is not limited to the above technical field. The technical field of the invention disclosed in the present specification relates to an object, a method, or a manufacturing method. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter.

[0003] In this specification and the like, a semiconductor device generally refers to anything that can function by utilizing semiconductor characteristics. Thus, semiconductor elements such as transistors and diodes, and circuits including semiconductor elements are semiconductor devices. Furthermore, display devices, light-emitting devices, lighting devices, electro-optical devices, and electronic devices may include semiconductor elements and semiconductor circuits. Thus, display devices, light-emitting devices, lighting devices, electro-optical devices, imaging devices, and electronic devices may also be called semiconductor devices. [Background technology]

[0004] In recent years, various types of power storage devices, such as lithium ion secondary batteries, lithium ion capacitors, and air batteries, have been actively developed. In particular, the demand for high-output, high-energy-density lithium ion secondary batteries has rapidly expanded in conjunction with the development of the semiconductor industry, and they have become indispensable in the modern information society as a rechargeable energy source, for use in portable information terminals, such as mobile phones, smartphones, tablets, and notebook computers, game devices, portable music players, digital cameras, medical devices, next-generation clean energy automobiles, such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs), and electric motorcycles.

[0005] A power storage device is usually equipped with a battery protection circuit to detect abnormalities during charging and discharging, such as over-discharging, over-charging, overcurrent, or short circuit.

[0006] A battery protection circuit acquires data such as voltage and current to detect abnormalities during charging or discharging. The battery protection circuit controls the opening and closing of a switch provided in the charging path or discharging path based on the observed data, and protects the battery cell from overcharging or overdischarging (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2016-118821 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of one embodiment of the present invention is to provide a semiconductor device or the like with reduced power consumption. Another object is to provide a semiconductor device or the like with high voltage detection accuracy. Another object is to provide a semiconductor device or the like with stable operation. Another object is to provide a semiconductor device or the like with high reliability. Another object is to provide a semiconductor device or the like with high productivity. Another object is to provide a novel semiconductor device or the like.

[0009] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not need to solve all of these problems. Note that problems other than these will become apparent from the description of the specification, drawings, claims, etc., and it is possible to extract problems other than these from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0010] One embodiment of the present invention is a semiconductor device including first to third switches, a first capacitance element, and a comparator, in which one terminal of the first switch is electrically connected to the first terminal, the other terminal of the first switch is electrically connected to a non-inverting input of the comparator, one terminal of the second switch is electrically connected to the second terminal, the other terminal of the second switch is electrically connected to one terminal of a third switch, and the other terminal of the third switch is electrically connected to the third terminal, the first capacitance element is provided between the other terminal of the first switch and the one terminal of the third switch, an inverting input of the comparator is electrically connected to a fourth terminal, and an output of the comparator is electrically connected to a fifth terminal.

[0011] Another embodiment of the present invention is a semiconductor device including first to third transistors, a first capacitor, and a comparator, in which one of a source or a drain of the first transistor is electrically connected to a first terminal, the other of the source or the drain of the first transistor is electrically connected to a non-inverting input of the comparator, one of a source or a drain of the second transistor is electrically connected to a second terminal, the other of the source or the drain of the second transistor is electrically connected to one of a source or a drain of a third transistor, and the other of the source or the drain of the third transistor is electrically connected to a third terminal, the first capacitor is provided between the other of the source or the drain of the first transistor and the one of the source or the drain of the third transistor, an inverting input of the comparator is electrically connected to a fourth terminal, and an output of the comparator is electrically connected to a fifth terminal.

[0012] The first transistor preferably includes an oxide semiconductor in a semiconductor layer, and at least one of the second transistor and the third transistor preferably includes an oxide semiconductor in a semiconductor layer.

[0013] Another embodiment of the present invention includes first to sixth switches, a first capacitance element, a second capacitance element, and a comparator, in which one terminal of the first switch is electrically connected to the first terminal, the other terminal of the first switch is electrically connected to one terminal of the sixth switch, one terminal of the second switch is electrically connected to the second terminal, the other terminal of the second switch is electrically connected to one terminal of the third switch, the other terminal of the third switch is electrically connected to the third terminal, one terminal of the fourth switch is electrically connected to the first terminal, the other terminal of the fifth switch is electrically connected to the non-inverting input of the comparator, one terminal of the fifth switch is electrically connected to the second terminal and the other terminal of the fifth switch is electrically connected to the other terminal of the sixth switch, the first capacitive element is provided between the other terminal of the first switch and one terminal of the third switch, the second capacitive element is provided between the other terminal of the fourth switch and the other terminal of the fifth switch, the inverting input of the comparator is electrically connected to the fourth terminal, and the output of the comparator is electrically connected to the fifth terminal.

[0014] Another embodiment of the present invention is a battery pack including any one of the above semiconductor devices provided over a flexible substrate and a secondary battery, in which a negative electrode of the secondary battery is electrically connected to a first terminal and a positive electrode of the secondary battery is electrically connected to a third terminal.

[0015] Another embodiment of the present invention is an electronic device including the above battery pack and a power receiving device. Effect of the Invention

[0016] According to one embodiment of the present invention, a semiconductor device or the like with reduced power consumption can be provided. Alternatively, a semiconductor device or the like with high voltage detection accuracy can be provided. Alternatively, a semiconductor device or the like with stable operation can be provided. Alternatively, a semiconductor device or the like with high reliability can be provided. Alternatively, a semiconductor device or the like with high productivity can be provided. Alternatively, a novel semiconductor device or the like can be provided.

[0017] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not need to have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract effects other than these from the description in the specification, drawings, claims, etc. [Brief description of the drawings]

[0018] [Figure 1] 1A and 1B are diagrams illustrating a configuration example of a semiconductor device. [Diagram 2] FIG. 2 is a timing chart illustrating an example of the operation of the semiconductor device. [Diagram 3] 3A and 3B are diagrams illustrating an example of the operation of the semiconductor device. [Figure 4] 4A and 4B are diagrams illustrating an example of the operation of the semiconductor device. [Diagram 5] 5A and 5B are diagrams showing a configuration example of a conventional semiconductor device. [Figure 6] 6A to 6D are diagrams showing circuit symbols for transistors. [Figure 7] FIG. 7 is a diagram illustrating a configuration example of a semiconductor device. [Figure 8] FIG. 8 is a diagram illustrating a configuration example of a semiconductor device. [Figure 9] FIG. 9 is a diagram illustrating a configuration example of a semiconductor device. [Figure 10] FIG. 10 is a timing chart illustrating an example of the operation of the semiconductor device. [Figure 11] FIG. 11 is a diagram illustrating an example of the operation of the semiconductor device. [Figure 12] FIG. 12 is a diagram illustrating an example of the operation of the semiconductor device. [Figure 13] FIG. 13 is a diagram illustrating an example of the operation of the semiconductor device. [Figure 14] FIG. 14 is a diagram illustrating an example of the operation of the semiconductor device. [Figure 15] 15A and 15B are diagrams illustrating a configuration example of a semiconductor device. [Figure 16] FIG. 16 is a diagram illustrating a configuration example of a semiconductor device. [Figure 17] FIG. 17 is a diagram illustrating a configuration example of a semiconductor device. [Figure 18] 18A to 18C are diagrams showing configuration examples of transistors. [Figure 19] 19A to 19C are diagrams showing configuration examples of transistors. [Figure 20] 20A to 20C are diagrams showing configuration examples of transistors. [Figure 21] 21A to 21C are diagrams showing configuration examples of a secondary battery. [Figure 22] 22A and 22B are diagrams showing configuration examples of a wound body and a secondary battery. [Diagram 23] 23A to 23C are diagrams showing configuration examples of a battery pack. [Figure 24] 24A to 24D are diagrams showing configuration examples of a battery pack. [Diagram 25] 25A to 25D are diagrams showing configuration examples of a battery pack. [Figure 26] 26A and 26B are diagrams showing configuration examples of a secondary battery. [Figure 27] 27A and 27B are diagrams showing an example of an electronic device. [Figure 28] 28A and 28B are diagrams showing an example of an electronic device. [Figure 29] FIG. 29 is a diagram illustrating an example of an electronic device. [Diagram 30] 30A to 30D are diagrams showing the verification results of the circuit operation. [Diagram 31] 31A to 31D are diagrams showing the verification results of the circuit operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that the form and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below. In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and repeated explanations thereof will be omitted.

[0020] In addition, 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.

[0021] In addition, in top views (also called "plan views"), perspective views, and the like, illustration of some components may be omitted in order to make the drawings easier to understand.

[0022] In addition, the terms "electrode" and "wiring" used in this specification and the like 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" include cases where multiple "electrodes" or "wirings" are formed integrally.

[0023] In addition, in this specification and the like, a "terminal" in an electric circuit refers to a portion where a current is input or output, a voltage is input or output, or a signal is received or transmitted. Therefore, a part of a wiring or an electrode may function as a terminal.

[0024] In this specification, the terms "above" and "below" do not limit the positional relationship of components to being directly above or below and in direct contact. For example, the expression "electrode B on insulating layer A" does not require that electrode B be formed in direct contact with insulating layer A, and does not exclude the inclusion of other components between insulating layer A and electrode B.

[0025] In addition, the functions of the source and drain are interchangeable depending on the operating conditions, such as when transistors of different polarities are used or when the direction of current changes during circuit operation, so it is difficult to determine which is the source and which is the drain. For this reason, in this specification, the terms source and drain can be used interchangeably.

[0026] In addition, in this specification, "electrically connected" includes a direct connection and a connection via "something having some electrical action." Here, the "something having some electrical action" is not particularly limited as long as it allows the transmission and reception of electrical signals between the connected objects. Therefore, even when it is expressed as "electrically connected," in the actual circuit, there may be no physical connection and only wiring extending therethrough.

[0027] In this specification and elsewhere, "parallel" refers to, for example, a state in which two straight lines are arranged at an angle of -10° or more and 10° or less. This therefore includes cases in which the angle is -5° or more and 5° or less. Furthermore, "perpendicular" and "orthogonal" refer to, for example, a state in which two straight lines are arranged at an angle of 80° or more and 100° or less. This therefore includes cases in which the angle is 85° or more and 95° or less.

[0028] In this specification and elsewhere, when referring to counting values ​​and measurement values, terms such as "same," "equal," "uniform," etc. are used, they are intended to include an error of plus or minus 20% unless otherwise expressly stated.

[0029] 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 interchanged. In this specification and the like, unless otherwise specified, voltage and potential can be interchanged.

[0030] Even when written as "semiconductor", for example, if the conductivity is sufficiently low, it has the characteristics of an "insulator". Therefore, it is also possible to use "semiconductor" instead of "insulator". In this case, the boundary between "semiconductor" and "insulator" is ambiguous, and it is difficult to strictly distinguish between the two. Therefore, "semiconductor" and "insulator" described in this specification may be read as interchangeable.

[0031] Furthermore, even when written as "semiconductor", if the conductivity is sufficiently high, it has the characteristics of a "conductor". Therefore, it is also possible to use "semiconductor" in place of "conductor". In this case, the boundary between "semiconductor" and "conductor" is ambiguous, and it is difficult to strictly distinguish between the two. Therefore, "semiconductor" and "conductor" described in this specification may be interchangeable.

[0032] In addition, ordinal numbers such as "first" and "second" in this specification are used to avoid confusion of components, and do not indicate any order or ranking, such as the order of processes or stacking. Even if a term does not have an ordinal number in this specification, an ordinal number may be added in the claims to avoid confusion of components. Even if a term has an ordinal number in this specification, a different ordinal number may be added in the claims. Even if a term has an ordinal number in this specification, the ordinal number may be omitted in the claims.

[0033] In this specification, the "on state" of a transistor refers to a state in which the source and drain of the transistor can be regarded as being 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 can be regarded as being electrically disconnected (also referred to as a "non-conductive state").

[0034] In this specification, the term "on-state current" may refer to a current that flows between a source and a drain when a transistor is on, and the term "off-state current" may refer to a current that flows between a source and a drain when a transistor is off.

[0035] In this specification, the high power supply potential VDD (hereinafter simply referred to as "VDD", "H potential", or "H") 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", "L potential", or "L") 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.

[0036] In this specification and the like, a gate refers to a gate electrode and a part or the whole of a gate wiring. A gate wiring refers to a wiring for electrically connecting a gate electrode of at least one transistor to another electrode or another wiring.

[0037] In this specification and the like, the source refers to a source region, a source electrode, and a part or all of a source wiring. The source region refers to a region of a semiconductor layer having a resistivity equal to or lower than a certain value. The source electrode refers to a conductive layer connected to the source region. The source wiring refers to a wiring for electrically connecting the source electrode of at least one transistor to another electrode or another wiring.

[0038] In this specification and the like, the drain refers to a part or all of the drain region, the drain electrode, and the drain wiring. The drain region refers to a region of the semiconductor layer whose resistivity is equal to or lower than a certain value. The drain electrode refers to a conductive layer that is connected to the drain region. The drain wiring refers to a wiring for electrically connecting the drain electrode of at least one transistor to another electrode or another wiring.

[0039] In addition, in drawings, etc., to make the potential of wiring and electrodes easier to understand, "H" indicating H potential or "L" indicating L potential may be written next to the wiring and electrode. Wiring and electrodes where a potential change has occurred may be written with "H" or "L" enclosed in a box. When a transistor is in the off state, an "x" symbol may be written over the transistor.

[0040] (Embodiment 1) A semiconductor device according to one embodiment of the present invention will be described with reference to drawings.

[0041] <Voltage detection circuit 9900> First, a conventional example of a semiconductor device will be described. As a conventional example of a semiconductor device, a configuration example of a voltage detection circuit 9900 using resistive voltage division shown in FIG.

[0042] The voltage detection circuit 9900 has a resistor R1, a resistor R2, and a comparator 9901 (comparison circuit). The resistor R1 is provided between a terminal 9911 and a node ND9, and the resistor R2 is provided between a terminal 9912 and the node ND9. The node ND9 is also electrically connected to the non-inverting input of the comparator 9901. The inverting input of the comparator 9901 is electrically connected to a terminal 9915, and the output of the comparator 9901 is electrically connected to a terminal 9913.

[0043] Terminal 9912 is electrically connected to terminal 201 and the positive electrode of secondary battery 300. Terminal 9911 is electrically connected to terminal 202 and the negative electrode of secondary battery 300. Voltage detection circuit 9900 has a function of changing the voltage of terminal 9913 from L to H when the voltage supplied to secondary battery 300 via terminals 201 and 202 reaches or exceeds a certain value.

[0044] The operation of the voltage detection circuit 9900 will be described with reference to Fig. 5B. Note that the comparator shown in this specification etc. outputs L when the voltage input to the non-inverting input is equal to or lower than the voltage input to the inverting input, and outputs H when the voltage input to the non-inverting input exceeds the voltage input to the inverting input.

[0045] For example, if the resistance value of resistor R1 is 1 MΩ, the resistance value of resistor R2 is 3 MΩ, and the voltage of terminal 9915 is 1.0 V, when the voltage of terminal 9911 is 0 V and the voltage of terminal 9912 becomes 4.0 V, the voltage of node ND9 becomes 1.0 V due to the resistive voltage division. That is, 1.0 V is supplied to the non-inverting input of comparator 9901. Also, since 1.0 V is supplied to the inverting input of comparator 9901 via terminal 9915, L is output from comparator 9901. As a result, the voltage of terminal 9913 becomes L.

[0046] When the voltage at terminal 9912 exceeds 4.0 V, the voltage at node ND9 also exceeds 1.0 V, causing the comparator 9901 to output H. As a result, the voltage at terminal 9913 becomes H. For example, when the voltage at terminal 9912 increases by 0.4 V from 4.0 V to 4.4 V, the voltage at node ND9 increases by 0.1 V from 1.0 V to 1.1 V.

[0047] In the conventional voltage detection circuit 9900 using resistive voltage division, it is difficult to reduce power consumption because a current It always flows between the terminal 9911 and the terminal 9912. Also, in principle, the amount of voltage change at the node ND9 is smaller than the amount of voltage change at the terminal 9912, which causes a problem of low detection sensitivity.

[0048] <Voltage detection circuit 100> As an example of a semiconductor device according to one embodiment of the present invention, a configuration example of a voltage detection circuit 100 will be described with reference to FIG. 1A.

[0049] [Configuration example] The voltage detection circuit 100 includes a switch SW1, a switch SW2, a switch SW3, a capacitor C1, and a comparator 101 (comparison circuit). One terminal of the switch SW1 is electrically connected to a terminal 111, and the other terminal is electrically connected to a node ND1. One terminal of the switch SW2 is electrically connected to a terminal 114, and the other terminal is electrically connected to a node ND2. One terminal of the switch SW3 is electrically connected to the node ND2, and the other terminal is electrically connected to a terminal 112.

[0050] The capacitor C1 is provided between the node ND1 and the node ND2. The non-inverting input of the comparator 101 is electrically connected to the node ND1, and the inverting input is electrically connected to the terminal 115. The output of the comparator 101 is electrically connected to the terminal 113.

[0051] Terminal 112 is electrically connected to terminal 201 and the positive electrode of secondary battery 300. Terminal 111 is electrically connected to terminal 202 and the negative electrode of secondary battery 300. Voltage detection circuit 100 has a function of changing the voltage of terminal 113 from L to H when the voltage supplied to secondary battery 300 via terminals 201 and 202 reaches or exceeds a certain value.

[0052] In this specification and the like, a switch refers to a device that has a function of being in a conductive state (on state) or a non-conductive state (off state) and controlling whether or not a current flows. Alternatively, a switch refers to a device that has a function of selecting and switching a path through which a current flows. As an example, an electrical switch, a mechanical switch, or the like can be used. In other words, the switch is not limited to a specific one as long as it can control a current.

[0053] Examples of electrical switches include transistors (e.g., bipolar transistors, MOS transistors, etc.), diodes (e.g., PN diodes, PIN diodes, Schottky diodes, MIM (Metal Insulator Metal) diodes, MIS (Metal Insulator Semiconductor) diodes, diode-connected transistors, etc.), and logic circuits combining these. Note that when a transistor is operated as a switch, the polarity (conductivity type) of the transistor is not particularly limited.

[0054] An example of a mechanical switch is a switch that uses MEMS (microelectromechanical system) technology, such as a digital micromirror device (DMD). The switch has an electrode that can be moved mechanically, and the movement of the electrode controls whether the switch is conductive or non-conductive.

[0055] [Modifications] FIG. 1B shows a configuration example of a voltage detection circuit 100T in which the switches SW1, SW2, and SW3 constituting the voltage detection circuit 100 are replaced with transistors.

[0056] The voltage detection circuit 100T includes a transistor M1, a transistor M2, a transistor M3, a capacitor C1, and a comparator 101 (comparison circuit). One of the source or drain of the transistor M1 is electrically connected to a terminal 111, and the other of the source or drain is electrically connected to a node ND1. The gate of the transistor M1 is electrically connected to a terminal G1. One of the source or drain of the transistor M2 is electrically connected to a terminal 114, and the other of the source or drain is electrically connected to a node ND2. The gate of the transistor M2 is electrically connected to a terminal G2. One of the source or drain of the transistor M3 is electrically connected to a node ND2, and the other of the source or drain is electrically connected to a terminal 112. The gate of the transistor M3 is electrically connected to a terminal G3.

[0057] The capacitor C1 is provided between the node ND1 and the node ND2. The non-inverting input of the comparator 101 is electrically connected to the node ND1, and the inverting input is electrically connected to the terminal 115. The output of the comparator 101 is electrically connected to the terminal 113.

[0058] The transistors M1, M2, and M3 are preferably transistors including an oxide semiconductor, which is a type of metal oxide, in a semiconductor layer in which a channel is formed (also referred to as "OS transistors"). The oxide semiconductor has a band gap of 2 eV or more and therefore has an extremely small off-state current. This allows the power consumption of the voltage detection circuit 100T to be reduced. Furthermore, the power consumption of a semiconductor device including the voltage detection circuit 100T can be reduced. In particular, it is preferable to use an OS transistor as the transistor M1 because charge supplied to the node ND1 can be held for a long period of time.

[0059] When a transistor functions as a switch, one of the source or drain of the transistor corresponds to one end (one terminal) of the switch, and the other of the source or drain of the transistor corresponds to the other end (the other terminal) of the switch.

[0060] In addition, each of the transistors M1, M2, and M3 may be a double-gate transistor. An example of a circuit symbol of a double-gate transistor 150A is shown in FIG 6A.

[0061] The transistor 150A has a configuration in which a transistor Tr1 and a transistor Tr2 are connected in series. Fig. 6A shows a state in which one of the source or drain of the transistor Tr1 is electrically connected to a terminal S, the other of the source or drain of the transistor Tr1 is electrically connected to one of the source or drain of the transistor Tr2, and the other of the source or drain of the transistor Tr2 is electrically connected to a terminal D. Fig. 6A also shows a state in which the gates of the transistor Tr1 and the transistor Tr2 are electrically connected and also electrically connected to a terminal G.

[0062] 6A has a function of switching the state between terminals S and D into a conductive state or a non-conductive state by changing the potential of terminal G. Thus, the transistor 150A, which is a double-gate transistor, functions as one transistor with transistors Tr1 and Tr2 built in. That is, in FIG. 6A, one of the source or drain of the transistor 150A is electrically connected to the terminal S, the other of the source or drain is electrically connected to the terminal D, and the gate is electrically connected to the terminal G.

[0063] In addition, each of the transistors M1, M2, and M3 may be a triple-gate transistor. An example of a circuit symbol of a triple-gate transistor 150B is shown in FIG.

[0064] The transistor 150B has a configuration in which a transistor Tr1, a transistor Tr2, and a transistor Tr3 are connected in series. In FIG. 6B, one of the source or drain of the transistor Tr1 is electrically connected to a terminal S, the other of the source or drain of the transistor Tr1 is electrically connected to one of the source or drain of the transistor Tr2, the other of the source or drain of the transistor Tr2 is electrically connected to one of the source or drain of the transistor Tr3, and the other of the source or drain of the transistor Tr3 is electrically connected to a terminal D. In addition, in FIG. 6B, the gates of the transistors Tr1, Tr2, and Tr3 are electrically connected to a terminal G.

[0065] The transistor 150B shown in FIG. 6B has a function of switching the state between the terminal S and the terminal D between conductive and non-conductive states by changing the potential of the terminal G. Thus, the triple-gate transistor 150B, which includes the transistors Tr1, Tr2, and Tr3, functions as one transistor. That is, in FIG. 6B, one of the source or the drain of the transistor 150B is electrically connected to the terminal S, the other of the source or the drain is electrically connected to the terminal D, and the gate is electrically connected to the terminal G.

[0066] A transistor having multiple gates that are electrically connected, such as the transistor 150A and the transistor 150B, may be referred to as a "multi-gate transistor" or a "multi-gate transistor".

[0067] Also, each of the transistors M1, M2, and M3 may be a transistor having a back gate. Fig. 6C shows an example of a circuit symbol of a transistor 150C having a back gate. Fig. 6D shows an example of a circuit symbol of a transistor 150D having a back gate.

[0068] The transistor 150C has a structure in which the gate and the backgate are electrically connected. The transistor 150D has a structure in which the backgate is electrically connected to the terminal BG. The backgate is disposed so as to sandwich a channel formation region of the semiconductor layer between the gate and the backgate. The backgate can function in the same manner as the gate.

[0069] The on-state current of a transistor can be increased by electrically connecting the gate and the back gate, and the threshold voltage of the transistor can be changed by independently changing the potential of the back gate.

[0070] [Example of operation] An operation example of the voltage detection circuit 100 will be described with reference to Figures 2 to 4. Figure 2 is a timing chart illustrating the operation of the voltage detection circuit 100. Figures 3 and 4 are diagrams illustrating the operating state of the voltage detection circuit 100.

[0071] In this embodiment, an operation will be described in which, in the charging operation of secondary battery 300, when the charging voltage is 4V or less, the potential of terminal 113 becomes L, and when the charging voltage exceeds 4V, the potential of terminal 113 becomes H. It is also assumed that 3V is supplied to terminal 114 and 1V is supplied to terminal 115. It is also assumed that the voltage of terminal 201 changes from 3.5V to 4.4V during charging operation.

[0072] [Period T1] In period T1, the switches SW1 and SW2 are turned on, and the switch SW3 is turned off (see FIG. 3A). Then, the voltage of the node ND1 becomes 0V, and the voltage of the node ND2 becomes 3V. 1V is input to the inverting input of the comparator 101, and 0V is input to the non-inverting input. Therefore, the output of the comparator 101 is L, and the voltage of the terminal 113 also becomes L.

[0073] [Period T2] In period T2, the switches SW1 and SW2 are turned off, and the switch SW3 is turned on (see FIG. 3B). Then, the voltage of the node ND2 becomes 3.5 V, and the voltage of the node ND1 becomes 0.5 V. 1 V is input to the inverting input of the comparator 101, and 0.5 V is input to the non-inverting input. Therefore, the output of the comparator 101 remains at L, and the voltage of the terminal 113 also remains at L.

[0074] Furthermore, when the voltage at the terminal 201 rises, the voltages at the terminal 112 and the node ND2 also rise, and therefore the voltage at the node ND1 also rises.

[0075] [Period T3] Following the period T2, the voltage of the terminal 201 also rises in the period T3. Therefore, the potentials of the terminal 112, the node ND2, and the node ND1 rise. It is assumed that the voltage of the terminal 201 rises to 4V in the period T3.

[0076] When the voltage at terminal 201 becomes 4 V, the voltages at terminal 112 and node ND2 also become 4 V. Also, the voltage at node ND1 becomes 1 V (see FIG. 4A). 1 V is input to the inverting input of comparator 101, and 1 V is also input to the non-inverting input. Therefore, the output of comparator 101 remains at L, and the voltage at terminal 113 also remains at L.

[0077] [Period T4] The voltage at the terminal 201 also rises during the period T4. It is assumed that the voltage at the terminal 201 rises to 4.4V during the period T4.

[0078] When the voltage at terminal 201 exceeds 4 V, the voltages at terminal 112 and node ND2 also exceed 4 V. Furthermore, the voltage at node ND1 also exceeds 1 V. 1 V is input to the inverting input of comparator 101, and a voltage exceeding 1 V is input to the non-inverting input. Therefore, the output of comparator 101 becomes H, and the voltage at terminal 113 also becomes H.

[0079] When the voltage at the terminal 201 becomes 4.4V, the voltage at the node ND2 also becomes 4.4V, and the voltage at the node ND1 becomes 1.4V (see FIG. 4B).

[0080] Unlike the conventional voltage detection circuit 9900, the voltage detection circuit 100 according to one embodiment of the present invention does not generate a current It during operation. This reduces power consumption. In addition, the voltage change amounts of the terminal 112 and the node ND2 are equal, resulting in good detection sensitivity.

[0081] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0082] (Embodiment 2) In this embodiment, a modified example of the semiconductor device shown in the above embodiment will be described. For matters not described in this embodiment, the above embodiment may be referred to.

[0083] <Voltage detection circuit 100A> A voltage detection circuit 100A will be described as a modification of the semiconductor device according to one embodiment of the present invention. Note that the voltage detection circuit 100A is a modification of the voltage detection circuit 100 described in the above embodiment.

[0084] [Configuration example] 7 shows an example of the configuration of the voltage detection circuit 100A. The voltage detection circuit 100A has a configuration in which a switch SW4, a switch SW5, a switch SW6, and a capacitor C2 are added to the configuration of the voltage detection circuit 100.

[0085] Specifically, one terminal of the switch SW1 is electrically connected to the terminal 111, and the other terminal is electrically connected to the node ND1. One terminal of the switch SW2 is electrically connected to the terminal 114, and the other terminal is electrically connected to the node ND2. One terminal of the switch SW3 is electrically connected to the node ND2, and the other terminal is electrically connected to the terminal 112. One terminal of the switch SW4 is electrically connected to the terminal 111, and the other terminal is electrically connected to the node ND3. One terminal of the switch SW5 is electrically connected to the terminal 114, and the other terminal is electrically connected to the node ND4. One terminal of the switch SW6 is electrically connected to the node ND1, and the other terminal is electrically connected to the node ND4.

[0086] The capacitor C1 is provided between the nodes ND1 and ND2. The capacitor C2 is provided between the nodes ND3 and ND4. The non-inverting input of the comparator 101 is electrically connected to the node ND3, and the inverting input is electrically connected to the terminal 115. The output of the comparator 101 is electrically connected to the terminal 113.

[0087] Terminal 112 is electrically connected to terminal 201 and the positive electrode of secondary battery 300. Terminal 111 is electrically connected to terminal 202 and the negative electrode of secondary battery 300. Voltage detection circuit 100A has a function of changing the voltage of terminal 113 from L to H when the voltage supplied to secondary battery 300 via terminals 201 and 202 reaches or exceeds a certain value.

[0088] [Variation 1] A voltage detection circuit 100B, which is a modification of the voltage detection circuit 100A, is shown in Fig. 8. The voltage detection circuit 100B has terminals 111A and 111B instead of the terminal 111, and has terminals 114A and 114B instead of the terminal 114.

[0089] In the voltage detection circuit 100B, one terminal of the switch SW1 is electrically connected to the terminal 111A, and one terminal of the switch SW4 is electrically connected to the terminal 111B. Furthermore, one terminal of the switch SW2 is electrically connected to the terminal 114A, and one terminal of the switch SW5 is electrically connected to the terminal 114B.

[0090] In the voltage detection circuit 100B, different voltages can be supplied to one terminal of the switch SW2 and one terminal of the switch SW5. In addition, although the terminals 111A and 111B are both electrically connected to the terminal 202 in Fig. 8, the terminals 111A and 111B may be electrically connected to different terminals or wirings.

[0091] [Modification 2] 9 shows a configuration example of a voltage detection circuit 100TA in which the switches SW1 to SW6 constituting the voltage detection circuit 100A are replaced with transistors. The voltage detection circuit 100TA is a modified example of the voltage detection circuit 100T. The voltage detection circuit 100TA has a configuration in which a transistor M4, a transistor M5, a transistor M6, and a capacitor C2 are added to the configuration of the voltage detection circuit 100T.

[0092] Specifically, the voltage detection circuit 100TA includes a transistor M1, a transistor M2, a transistor M3, a transistor M4, a transistor M5, a transistor M6, a capacitor C1, a capacitor C2, and a comparator 101. One of the source or the drain of the transistor M1 is electrically connected to a terminal 111, and the other of the source or the drain is electrically connected to a node ND1. The gate of the transistor M1 is electrically connected to a terminal G1. One of the source or the drain of the transistor M2 is electrically connected to a terminal 114, and the other of the source or the drain is electrically connected to a node ND2. The gate of the transistor M2 is electrically connected to a terminal G2. One of the source or the drain of the transistor M3 is electrically connected to a node ND2, and the other of the source or the drain is electrically connected to a terminal 112. The gate of the transistor M3 is electrically connected to a terminal G3.

[0093] One of a source or a drain of the transistor M4 is electrically connected to the terminal 111, and the other of the source or the drain is electrically connected to the node ND3. The gate of the transistor M4 is electrically connected to the terminal G4. One of a source or a drain of the transistor M5 is electrically connected to the terminal 114, and the other of the source or the drain is electrically connected to the node ND4. The gate of the transistor M5 is electrically connected to the terminal G5. One of a source or a drain of the transistor M6 is electrically connected to the node ND1, and the other of the source or the drain is electrically connected to the node ND4. The gate of the transistor M6 is electrically connected to the terminal G6.

[0094] The capacitor C1 is provided between the nodes ND1 and ND2. The capacitor C2 is provided between the nodes ND3 and ND4. The non-inverting input of the comparator 101 is electrically connected to the node ND3, and the inverting input is electrically connected to the terminal 115. The output of the comparator 101 is electrically connected to the terminal 113.

[0095] Like the transistors M1 to M3, the transistors M4 to M6 are preferably OS transistors. In particular, it is preferable to use an OS transistor for the transistor M4 because the charge supplied to the node ND3 can be held for a long period of time. It is also preferable to use an OS transistor for the transistor M5 because the charge supplied to the node ND4 can be held for a long period of time.

[0096] [Example of operation] An operation example of the voltage detection circuit 100A will be described with reference to Figures 10 to 14. Figure 10 is a timing chart illustrating the operation of the voltage detection circuit 100A. Figures 11 to 14 are diagrams showing the operating states of the voltage detection circuit 100A.

[0097] In this embodiment, an operation will be described in which, in the charging operation of secondary battery 300, when the charging voltage is 4V or less, the potential of terminal 113 becomes L, and when the charging voltage exceeds 4V, the voltage of terminal 113 becomes H. It is also assumed that 1.5V is supplied to terminal 114, and 1V is supplied to terminal 115. It is also assumed that the voltage of terminal 201 changes from 3.5V to 4.4V during charging operation.

[0098] [Period T1] In period T1, switches SW1, SW2, SW4 and SW5 are turned on, and switches SW3 and SW6 are turned off (see FIG. 11). Then, the voltages of nodes ND1 and ND3 become 0V, and the voltages of nodes ND2 and ND4 become 1.5V. 1V is input to the inverting input of comparator 101, and 0V is input to the non-inverting input. Therefore, the output of comparator 101 is L, and the voltage of terminal 113 also becomes L.

[0099] [Period T2] In period T2, the switches SW1, SW2, SW4, and SW5 are turned off, and the switches SW3 and SW6 are turned on (see FIG. 12). Then, the voltage of the node ND2 rises from 1.5V to 3.5V by 2V, and the voltage of the node ND1 rises from 0V to 2V by 2V. In addition, since the switch SW6 is in the on state, the nodes ND1 and ND4 are electrically connected. Therefore, the node ND4 also becomes 2V. At this time, the voltage of the node ND4 rises from 1.5V to 0.5V. Therefore, the voltage of the node ND3 becomes 0.5V, and 0.5V is input to the non-inverting input of the comparator 101. Since 1V is input to the inverting input of the comparator 101, the output of the comparator 101 remains at L, and the voltage of the terminal 113 also remains at L.

[0100] Furthermore, when the voltage at the terminal 201 rises, the voltages at the terminal 112 and the node ND2 also rise, and therefore the voltages at the nodes ND1, ND3, and ND4 also rise.

[0101] [Period T3] Following the period T2, also in a period T3, the potentials of the terminal 112 and the nodes ND1 to ND4 increase in accordance with the increase in the potential of the terminal 201. It is assumed that the voltage of the terminal 201 increases to 4 V in the period T3.

[0102] When the voltage at terminal 201 becomes 4V, the voltages at terminal 112 and node ND2 also become 4V. Furthermore, the voltages at nodes ND1 and ND4 become 2.5V, and the voltage at node ND3 becomes 1V (see FIG. 13). Therefore, 1V is input to the inverting input of comparator 101. 1V is input to the non-inverting input of comparator 101. Therefore, the output of comparator 101 remains L, and the voltage at terminal 113 also remains L.

[0103] [Period T4] The voltage at the terminal 201 also rises during the period T4. It is assumed that the voltage at the terminal 201 rises to 4.4V during the period T4.

[0104] When the voltage at terminal 201 exceeds 4 V, the voltages at terminal 112 and node ND2 also exceed 4 V. Furthermore, the voltage at node ND3 also exceeds 1 V. 1 V is input to the inverting input of comparator 101, and a voltage exceeding 1 V is input to the non-inverting input. Therefore, the output of comparator 101 becomes H, and the voltage at terminal 113 also becomes H.

[0105] When the voltage of the terminal 201 becomes 4.4 V, the voltage of the node ND2 also becomes 4.4 V. Furthermore, the voltages of the nodes ND1 and ND4 become 2.9 V, and the voltage of the node ND3 becomes 1.4 V (see FIG. 14).

[0106] The voltage detection circuit 100A described in this embodiment can apply a smaller voltage to the terminal 114 than the voltage detection circuit 100. Therefore, the power consumption can be reduced more than that of the voltage detection circuit 100. In addition, the voltage required for operation can be reduced, so the load on the voltage generation circuit is reduced. Therefore, the operation of a semiconductor device using the voltage detection circuit 100A is stable, and the reliability can be improved.

[0107] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0108] (Embodiment 3) In this embodiment, a configuration example of a wireless power feeding system (also referred to as "wireless power feeding") using a semiconductor device according to one embodiment of the present invention will be described.

[0109] Known methods for achieving wireless power supply include radio wave, electric field coupling, magnetic field resonance, and electromagnetic induction. The electromagnetic induction method in particular is known for its ease of circuit design and high power transmission efficiency, and is being considered for use in mobile devices such as personal digital assistants. International standards for wireless power supply using the electromagnetic induction method include the Qi standard, the PMA standard, and the AirFuel Inductive standard.

[0110] In addition, the magnetic resonance method requires a more complex circuit design and is less efficient at transmitting power than the electromagnetic induction method, but it is capable of transmitting power over longer distances than the electromagnetic induction method, and its adoption in EVs (Electric Vehicles) is being considered. International standards for wireless power supply using the magnetic resonance method include the WPT1 standard, WPT2 standard, WPT3 standard, and AirFuel Resonant standard.

[0111] The semiconductor device according to one embodiment of the present invention can be used in various wireless power supply systems.

[0112] The wireless power feeding system exemplified in this embodiment includes a power transmitting device 400 and a power receiving device 450. An example of the configuration of the power transmitting device 400 is shown in Fig. 15A. An example of the configuration of the power receiving device 450 is shown in Fig. 15B.

[0113] Note that the configurations of the power transmitting device 400 illustrated in Fig. 15A and the power receiving device 450 illustrated in Fig. 15B are merely examples, and do not need to include all of the components. The power transmitting device 400 and the power receiving device 450 may include necessary components among the components illustrated in Fig. 15A and Fig. 15B. They may also include components other than those illustrated in Fig. 15A and Fig. 15B.

[0114] <Power transmission device 400> The power transmitting device 400 has a power transmission control circuit 411, a matching circuit 412, and a power radiation circuit 413. A power source 401 is connected to the power transmitting device 400. The power source 401 has a function of supplying AC power to the power transmitting device 400. The frequency fG of the AC power supplied by the power source 401 is not limited to a specific frequency, and any of the following can be used, for example: submillimeter waves of 300 GHz to 3 THz, millimeter waves of 30 GHz to 300 GHz, microwaves of 3 GHz to 30 GHz, ultra-high frequency waves of 300 MHz to 3 GHz, ultra-high frequency waves of 30 MHz to 300 MHz, short waves of 3 MHz to 30 MHz, medium waves of 300 kHz to 3 MHz, long waves of 30 kHz to 300 kHz, and very long waves of 3 kHz to 30 kHz.

[0115] The power transmission control circuit 411 has a function of supplying the power supplied from the power source 401 to the power radiation circuit 413 via the matching circuit 412. The power radiation circuit 413 is connected to the power transmitting antenna 402. The power radiation circuit 413 has a function of radiating the AC power supplied from the power source 401 to an external space via the power transmitting antenna 402.

[0116] If the impedance of power source 401 and the impedance of power radiation circuit 413 differ, a part of the AC power supplied from power source 401 is reflected according to the impedance difference, and the AC power cannot be efficiently supplied to power radiation circuit 413. Matching circuit 412 has a function of approximately matching the impedance of power source 401 and the impedance of power radiation circuit 413, and efficiently transmitting the AC power supplied from power source 401 to power radiation circuit 413.

[0117] <Power receiving device 450> 15B includes a power receiving antenna 403, a power receiving circuit 451, a charge control circuit 452, and a charge / discharge control circuit 453. The power receiving device 450 also includes a terminal 461, a terminal 462, and a terminal 463. In FIG. 15B, the positive electrode of the secondary battery 300 is electrically connected to the terminal 461, and the negative electrode of the secondary battery 300 is electrically connected to the terminal 462.

[0118] The power receiving circuit 451 has a resonant frequency fR determined based on the inductance of the power receiving antenna 403. By matching the frequency fG of the AC power radiated from the power transmitting antenna 402 with the resonant frequency fR of the power receiving circuit 451, an induced electromotive force is generated in the power receiving antenna 403, and power supply from the power transmitting device 400 to the power receiving device 450 can be realized.

[0119] The power receiving circuit 451 also includes a rectifier circuit. The rectifier circuit has a function of converting AC power induced in the power receiving antenna 403 into DC power.

[0120] The charging control circuit 452 has a function of adjusting the DC power supplied from the power receiving circuit 451 to an appropriate voltage. For example, the charging control circuit 452 may be provided with a function such as a switching regulator.

[0121] Furthermore, a normally-off CPU (Noff-CPU) may be used for the charge control circuit 452. Note that a normally-off CPU is an integrated circuit including normally-off transistors that are in a non-conductive state (also referred to as an off state) even when the gate voltage is 0 V. The normally-off transistors can be realized using OS transistors. By using a normally-off CPU, power consumption of the charge control circuit 452 during standby operation can be reduced.

[0122] The AC power induced in the power receiving antenna 403 can be charged to the secondary battery 300 via the power receiving circuit 451 and the charge control circuit 452. The power receiving device 450 can also function as a power source for an external device. Specifically, by electrically connecting to the external device via the terminals 461 and 463, the power receiving device 450 can supply the power of the secondary battery to the external device. The power received from the power transmitting device 400 can also be supplied to the external device.

[0123] The charge / discharge control circuit 453 has a function of monitoring the charge / discharge status of the secondary battery 300. The charge / discharge control circuit 453 has an overcurrent detection circuit, a voltage detection circuit, and the like. For example, if a current (also called "overcurrent") of a specified value or more flows when power is supplied from the secondary battery 300 to an external device, the charge / discharge control circuit 453 can turn off the transistor 471 to stop the power supply. If a current of a specified value or more flows when the secondary battery 300 is being charged, the charge / discharge control circuit 453 can turn off the transistor 472 to stop the charging. If a voltage (also called "overvoltage") of a specified value or more is applied to the secondary battery 300 when the secondary battery 300 is being charged, the charge / discharge control circuit 453 can turn off the transistor 472 to stop the charging.

[0124] In this embodiment, the power transmitting antenna 402 shown in Fig. 15A and the power receiving antenna 403 shown in Fig. 15B are illustrated with a circuit symbol indicating a coil. However, the power transmitting antenna 402 and the power receiving antenna 403 are not limited to coil-shaped antennas and may be appropriately changed depending on the power transmission method, etc. For example, they may be linear or plate-shaped. In addition, antennas such as planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas may be used.

[0125] The voltage detection circuit 100 according to one embodiment of the present invention can be used for the charge and discharge control circuit 453. Further, some or all of the transistors included in the wireless power feeding system can be OS transistors.

[0126] For example, by using an OS transistor as the transistor included in the power receiving device 450, the power receiving device 450 can be provided on a flexible substrate. This can reduce the volume and weight of the power receiving device 450. In addition, by providing the power receiving device 450 on a flexible substrate, the power receiving device 450 can also be provided along a side surface of the secondary battery 300, for example.

[0127] Note that a charge / discharge control circuit, an overcurrent detection circuit, a voltage detection circuit, an abnormality detection circuit, a secondary battery control system, or the like using an OS transistor may be referred to as a Battery operating system (BTOS) or a Battery oxide semiconductor.

[0128] OS transistors have an extremely low off-state current, which can reduce the power consumption of wireless power transfer systems. Furthermore, the off-state current of OS transistors hardly increases even in high-temperature environments. Specifically, the off-state current hardly increases even in environmental temperatures above room temperature and below 200°C. Furthermore, OS transistors have a high withstand voltage between the source and drain. By using OS transistors as the transistors that make up a wireless power transfer system, it is possible to realize a wireless power transfer system that operates stably even in high-temperature environments and has good reliability.

[0129] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0130] (Embodiment 4) In this embodiment mode, a structure of a transistor applicable to the semiconductor device described in the above embodiment mode will be described. Specifically, a structure in which transistors having different electrical characteristics are stacked will be described. By using this structure, the degree of freedom in designing the semiconductor device can be increased. In addition, by stacking transistors having different electrical characteristics, the degree of integration of the semiconductor device can be increased.

[0131] The semiconductor device shown in Fig. 16 includes a transistor 550, a transistor 500, and a capacitor 600. Fig. 18A is a cross-sectional view of the transistor 500 in the channel length direction, Fig. 18B is a cross-sectional view of the transistor 500 in the channel width direction, and Fig. 18C is a cross-sectional view of the transistor 550 in the channel width direction.

[0132] The transistor 500 is an OS transistor. Since the off-state current of the transistor 500 is extremely small, the transistor 500 can hold written data voltage or charge for a long period of time by using the transistor 500 as a transistor in a semiconductor device. In other words, the frequency of refresh operations is low or refresh operations are not required, so that the power consumption of the semiconductor device can be reduced.

[0133] 16, the semiconductor device described in this embodiment includes a transistor 550, a transistor 500, and a capacitor 600. The transistor 500 is provided above the transistor 550, and the capacitor 600 is provided above the transistors 550 and 500.

[0134] The transistor 550 is provided over a substrate 311 and includes a conductor 316, an insulator 315, a semiconductor region 313 formed of a part of the substrate 311, and a low-resistance region 314a and a low-resistance region 314b functioning as a source region or a drain region. Note that the transistor 550 can be applied to, for example, the transistor included in the comparator 101 in the above embodiment.

[0135] 18C, the upper surface and the side surface in the channel width direction of the semiconductor region 313 of the transistor 550 are covered with a conductor 316 via an insulator 315. By forming the transistor 550 as a fin type in this manner, the effective channel width is increased, thereby improving the on-characteristics of the transistor 550. In addition, the contribution of the electric field of the gate electrode can be increased, thereby improving the off-characteristics of the transistor 550.

[0136] The transistor 550 may be either a p-channel type or an n-channel type.

[0137] The region where the channel of the semiconductor region 313 is formed, the region nearby, the low resistance region 314a which becomes the source region or the drain region, and the low resistance region 314b preferably contain a semiconductor such as a silicon-based semiconductor, and preferably contain single crystal silicon. Alternatively, they may be formed of a material having Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), or the like. A configuration using silicon in which the effective mass is controlled by applying stress to the crystal lattice and changing the lattice spacing may be used. Alternatively, the transistor 550 may be a HEMT (High Electron Mobility Transistor) by using GaAs and GaAlAs, or the like.

[0138] Low resistance region 314a and low resistance region 314b contain, in addition to the semiconductor material applied to 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.

[0139] The conductor 316 functioning as the gate electrode can be made of a conductive material such as a semiconductor 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, a metal material, an alloy material, or a metal oxide material.

[0140] 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 for the conductor. Furthermore, in order to achieve both electrical conductivity and embeddability, it is preferable to use a metal material such as tungsten or aluminum as the conductor in a laminated state, and in particular, it is preferable to use tungsten in terms of heat resistance.

[0141] 16 is just an example and is not limited to the structure, and an appropriate transistor may be used depending on the circuit structure and driving method. For example, when the semiconductor device is a unipolar circuit including only OS transistors (meaning transistors having the same polarity, such as only n-channel transistors), the structure of the transistor 550 may be the same as that of the transistor 500 including an oxide semiconductor, as shown in FIG 17. Details of the transistor 500 will be described later.

[0142] An insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order over the transistor 550.

[0143] As the insulators 320, 322, 324, and 326, 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.

[0144] In this specification, silicon oxynitride refers to a material having a higher oxygen content than nitrogen, silicon nitride oxide refers to a material having a higher nitrogen content than oxygen, aluminum oxynitride refers to a material having a higher oxygen content than nitrogen, and aluminum nitride oxide refers to a material having a higher nitrogen content than oxygen.

[0145] The insulator 322 may function as a planarizing film that planarizes steps caused by the transistor 550 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 planarity.

[0146] The insulator 324 is preferably a film having a barrier property that prevents diffusion of hydrogen or impurities from the substrate 311, the transistor 550, or the like to a region where the transistor 500 is provided.

[0147] As an example of a film having a barrier property against hydrogen, for example, silicon nitride formed by a CVD method can be used. Here, when hydrogen diffuses into a semiconductor element having an oxide semiconductor such as the transistor 500, the characteristics of the semiconductor element may deteriorate. Therefore, it is preferable to use a film that suppresses the diffusion of hydrogen between the transistor 500 and the transistor 550. Specifically, the film that suppresses the diffusion of hydrogen is a film that releases a small amount of hydrogen.

[0148] The amount of desorption of hydrogen can be analyzed, for example, by using thermal desorption spectrometry (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 the TDS analysis. 15 atoms / cm 2 Less than or equal to 5×10 15 atoms / cm 2 The following is acceptable.

[0149] The insulator 326 preferably 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. 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 generated between wirings can be reduced.

[0150] Moreover, the insulator 320, the insulator 322, the insulator 324, and the insulator 326 are embedded with the capacitor 600 or the conductor 328 and the conductor 330 connected to the transistor 500. The conductor 328 and the conductor 330 function as a plug or wiring. In addition, a plurality of conductors having the function of a plug or wiring may be collectively given the same reference numeral. In addition, in this specification and the like, the wiring and the plug connected to the wiring may be integral. That is, there are cases where a part of the conductor functions as the wiring, and cases where a part of the conductor functions as the plug.

[0151] As the material for each plug and wiring (conductor 328, conductor 330, etc.), a conductive material such as a metal material, an alloy material, a metal nitride material, or a metal oxide material 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 that has both heat resistance and conductivity, and tungsten is preferably used. Alternatively, it is preferable to form the plug and wiring from a low resistance conductive material such as aluminum or copper. By using a low resistance conductive material, the wiring resistance can be reduced.

[0152] A wiring layer may be provided over the insulator 326 and the conductor 330. For example, in FIG. 16 , an insulator 350, an insulator 352, and an insulator 354 are stacked in this order. A conductor 356 is formed in the insulator 350, the insulator 352, and the insulator 354. The conductor 356 functions as a plug or wiring connected to the transistor 550. Note that the conductor 356 can be provided using a material similar to that of the conductor 328 and the conductor 330.

[0153] Note that, for example, the insulator 350 is preferably an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 356 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 350 having a barrier property against hydrogen. With this structure, the transistor 550 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 550 to the transistor 500 can be suppressed.

[0154] Note that, for example, tantalum nitride or the like may be used as a conductor having a barrier property against hydrogen. By stacking tantalum nitride and tungsten having high conductivity, diffusion of hydrogen from the transistor 550 can be suppressed 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.

[0155] A wiring layer may be provided on the insulator 354 and the conductor 356. For example, in FIG. 16, an insulator 360, an insulator 362, and an insulator 364 are stacked in this order. A conductor 366 is formed in the insulator 360, the insulator 362, and the insulator 364. The conductor 366 functions as a plug or a wiring. The conductor 366 can be provided using a material similar to that of the conductor 328 and the conductor 330.

[0156] Note that, for example, the insulator 360 is preferably an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 366 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 360 having a barrier property against hydrogen. With this structure, the transistor 550 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 550 to the transistor 500 can be suppressed.

[0157] A wiring layer may be provided on the insulator 364 and the conductor 366. For example, in FIG. 16, an insulator 370, an insulator 372, and an insulator 374 are stacked in this order. A conductor 376 is formed in the insulator 370, the insulator 372, and the insulator 374. The conductor 376 functions as a plug or a wiring. The conductor 376 can be provided using a material similar to that of the conductor 328 and the conductor 330.

[0158] Note that, for example, the insulator 370 is preferably an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 376 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 370 having a barrier property against hydrogen. With this structure, the transistor 550 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 550 to the transistor 500 can be suppressed.

[0159] A wiring layer may be provided over the insulator 374 and the conductor 376. For example, in FIG. 16, an insulator 380, an insulator 382, ​​and an insulator 384 are stacked in this order. A conductor 386 is formed in the insulator 380, the insulator 382, ​​and the insulator 384. The conductor 386 functions as a plug or a wiring. The conductor 386 can be provided using a material similar to that of the conductor 328 and the conductor 330.

[0160] Note that, for example, the insulator 380 is preferably an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 386 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 380 having a barrier property against hydrogen. With this structure, the transistor 550 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 550 to the transistor 500 can be suppressed.

[0161] In the above, a wiring layer including the conductor 356, a wiring layer including the conductor 366, a wiring layer including the conductor 376, and a wiring layer including the conductor 386 have been described, but the semiconductor device of this embodiment is not limited to this. There may be three or fewer wiring layers similar to the wiring layer including the conductor 356, or there may be five or more wiring layers similar to the wiring layer including the conductor 356.

[0162] An insulator 510, an insulator 512, an insulator 514, and an insulator 516 are stacked in this order on the insulator 384. Any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516 is preferably made of a substance that has a barrier property against oxygen or hydrogen.

[0163] For example, the insulator 510 and the insulator 514 are preferably formed using a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311 or a region where the transistor 550 is provided to a region where the transistor 500 is provided. Therefore, a material similar to that of the insulator 324 can be used.

[0164] As an example of a film having a barrier property against hydrogen, silicon nitride formed by a CVD method can be used. Here, when hydrogen diffuses into a semiconductor element having an oxide semiconductor such as the transistor 500, the characteristics of the semiconductor element may deteriorate. Therefore, it is preferable to use a film that suppresses the diffusion of hydrogen between the transistor 500 and the transistor 550. Specifically, the film that suppresses the diffusion of hydrogen is a film that releases a small amount of hydrogen.

[0165] As a film having a barrier property against hydrogen, for example, the insulator 510 and the insulator 514 are preferably made of a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0166] In particular, aluminum oxide has a high blocking effect of preventing the film from permeating both oxygen and impurities such as hydrogen and moisture, which are factors that cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the transistor manufacturing process. In addition, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0167] For example, the insulator 512 and the insulator 516 can be made of a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, the parasitic capacitance generated between wirings can be reduced. For example, the insulator 512 and the insulator 516 can be made of a silicon oxide film, a silicon oxynitride film, or the like.

[0168] A conductor 518, a conductor constituting the transistor 500 (for example, the conductor 503), and the like are embedded in the insulator 510, the insulator 512, the insulator 514, and the insulator 516. Note that the conductor 518 functions as a plug or wiring connected to the capacitor 600 or the transistor 550. The conductor 518 can be provided using a material similar to that of the conductor 328 and the conductor 330.

[0169] In particular, the insulator 510 and the conductor 518 in the region in contact with the insulator 514 are preferably conductors having barrier properties against oxygen, hydrogen, and water. With this structure, the transistor 550 and the transistor 500 can be separated by a layer having barrier properties against oxygen, hydrogen, and water, and diffusion of hydrogen from the transistor 550 to the transistor 500 can be suppressed.

[0170] Above the insulator 516 is a transistor 500 .

[0171] As shown in Figures 18A and 18B, a transistor 500 has a conductor 503 arranged so as to be embedded in an insulator 514 and an insulator 516, an insulator 520 arranged on the insulator 516 and the conductor 503, an insulator 522 arranged on the insulator 520, an insulator 524 arranged on the insulator 522, an oxide 530a arranged on the insulator 524, an oxide 530b arranged on the oxide 530a, conductors 542a and 542b arranged apart from each other on the oxide 530b, an insulator 580 arranged on the conductors 542a and 542b and having an opening formed therebetween overlapping with the conductors 542a and 542b, an oxide 530c arranged on the bottom and side surfaces of the opening, an insulator 545 arranged on the formation surface of the oxide 530c, and a conductor 560 arranged on the formation surface of the insulator 545.

[0172] 18A and 18B, it is preferable that an insulator 544 is disposed between the oxide 530a, the oxide 530b, the conductor 542a, and the conductor 542b and the insulator 580. It is preferable that the conductor 560 has a conductor 560a provided inside the insulator 545 and a conductor 560b provided so as to be embedded inside the conductor 560a, as shown in FIG. 18A and 18B. It is preferable that an insulator 574 is disposed on the insulator 580, the conductor 560, and the insulator 545, as shown in FIG. 18A and 18B.

[0173] In this specification and other places, oxide 530a, oxide 530b, and oxide 530c may be collectively referred to as oxide 530.

[0174] In the transistor 500, a three-layer structure of oxide 530a, oxide 530b, and oxide 530c is shown in the region where a channel is formed and in the vicinity thereof, but the present invention is not limited thereto. For example, a single layer of oxide 530b, a two-layer structure of oxide 530b and oxide 530a, a two-layer structure of oxide 530b and oxide 530c, or a stacked structure of four or more layers may be provided. In addition, in the transistor 500, the conductor 560 is shown as having a two-layer stacked structure, but the present invention is not limited thereto. For example, the conductor 560 may have a single layer structure or a stacked structure of three or more layers. In addition, the transistor 500 shown in FIG. 16 and FIG. 18A is an example, and the present invention is not limited thereto, and an appropriate transistor may be used depending on the circuit configuration and the driving method.

[0175] Here, the conductor 560 functions as a gate electrode of the transistor, and the conductors 542a and 542b function as a source electrode and a drain electrode, respectively. As described above, the conductor 560 is formed so as to be embedded in the opening of the insulator 580 and in the region sandwiched between the conductors 542a and 542b. The arrangement of the conductors 560, 542a, and 542b is selected in a self-aligned manner with respect to the opening of the insulator 580. That is, in the transistor 500, the gate electrode can be arranged in a self-aligned manner between the source electrode and the drain electrode. Therefore, the conductor 560 can be formed without providing a margin for alignment, so that the area occupied by the transistor 500 can be reduced. This allows the semiconductor device to be miniaturized and highly integrated.

[0176] Furthermore, since the conductor 560 is formed in a self-aligned manner in the region between the conductor 542a and the conductor 542b, the conductor 560 does not have a region that overlaps with the conductor 542a or the conductor 542b. This makes it possible to reduce the parasitic capacitance formed between the conductor 560 and the conductor 542a and between the conductor 560 and the conductor 542b. This makes it possible to improve the switching speed of the transistor 500 and provide high frequency characteristics.

[0177] The conductor 560 may function as a first gate (also referred to as a top gate) electrode. The conductor 503 may function as a second gate (also referred to as a bottom gate) electrode. In this case, the threshold voltage of the transistor 500 can be controlled by changing the potential applied to the conductor 503 independently of the potential applied to the conductor 560. In particular, by applying a negative potential to the conductor 503, the threshold voltage of the transistor 500 can be made higher than 0 V, and the off-current can be reduced. Therefore, applying a negative potential to the conductor 503 can reduce the drain current when the potential applied to the conductor 560 is 0 V, compared to when a negative potential is not applied.

[0178] The conductor 503 is disposed so as to overlap the oxide 530 and the conductor 560. In this manner, when a potential is applied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected, and a channel formation region formed in the oxide 530 can be covered.

[0179] In this specification, the configuration of a transistor in which the electric field of a pair of gate electrodes (a first gate electrode and a second gate electrode) electrically surrounds the channel formation region is called a surrounded channel (S-channel) configuration. In this specification, the surrounded channel (S-channel) configuration has a feature that the side and periphery of the oxide 530 in contact with the conductor 542a and the conductor 542b functioning as the source electrode and the drain electrode are I-type like the channel formation region. In addition, the side and periphery of the oxide 530 in contact with the conductor 542a and the conductor 542b are in contact with the insulator 544, so they can be I-type like the channel formation region. In this specification, the I-type can be treated as the same as the high purity intrinsic described later. In addition, the S-channel configuration disclosed in this specification is different from the fin type configuration and the planar type configuration. By adopting the S-channel configuration, it is possible to obtain a transistor that is more resistant to the short channel effect, in other words, in which the short channel effect is less likely to occur.

[0180] The conductor 503 has a structure similar to that of the conductor 518, and the conductor 503a is formed in contact with the inner walls of the openings of the insulator 514 and the insulator 516, and the conductor 503b is formed further inside. Note that, although the transistor 500 shows a structure in which the conductor 503a and the conductor 503b are stacked, the present invention is not limited to this. For example, the conductor 503 may have a single layer structure or a stacked structure of three or more layers.

[0181] Here, the conductor 503a is preferably made of a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (the impurities are less likely to permeate through). Alternatively, it is preferable to use a conductive material having a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) (the oxygen is less likely to permeate through). Note that in this specification, the function of suppressing the diffusion of impurities or oxygen refers to the function of suppressing the diffusion of any one or all of the impurities and oxygen.

[0182] For example, the conductor 503a has a function of suppressing the diffusion of oxygen, so that the conductor 503b can be prevented from being oxidized and the conductivity from decreasing.

[0183] In addition, when the conductor 503 also functions as a wiring, it is preferable that the conductor 503b is made of a highly conductive material containing tungsten, copper, or aluminum as a main component. Note that, although the conductor 503 is illustrated in this embodiment as a stack of the conductors 503a and 503b, the conductor 503 may have a single layer structure.

[0184] The insulators 520, 522, and 524 function as a second gate insulating film.

[0185] Here, it is preferable that the insulator 524 in contact with the oxide 530 is an insulator containing more oxygen than the oxygen required for the stoichiometric composition. In other words, it is preferable that an excess oxygen region is formed in the insulator 524. By providing an insulator containing such excess oxygen in contact with the oxide 530, the oxygen deficiency (V O In addition, when hydrogen enters an oxygen vacancy in the oxide 530, the defect (hereinafter, V OH.) may function as a donor and generate electrons as carriers. Some of the hydrogen may bond with oxygen that is bonded to a metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing a large amount of hydrogen is likely to have normally-on characteristics. Furthermore, hydrogen in an oxide semiconductor is easily moved by stress such as heat or an electric field. Therefore, if an oxide semiconductor contains a large amount of hydrogen, the reliability of the transistor may be deteriorated. In one embodiment of the present invention, V in the oxide 530 O It is preferable to reduce H as much as possible and make it high-purity intrinsic or substantially high-purity intrinsic. O In order to obtain an oxide semiconductor with sufficiently reduced H, it is important to remove impurities such as moisture and hydrogen from the oxide semiconductor (sometimes referred to as dehydration or dehydrogenation treatment) and to supply oxygen to the oxide semiconductor to compensate for oxygen vacancies (sometimes referred to as oxygen addition treatment). O By using an oxide semiconductor in which impurities such as H are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0186] Specifically, it is preferable to use an oxide material from which some oxygen is released by heating as an insulator having an excess oxygen region. An oxide material from which oxygen is released by heating is an oxide material from which the amount of released oxygen converted into oxygen atoms is 1.0×10 18 atoms / cm 3 More than 1.0×10 19 atoms / cm 3 More preferably, 2.0×10 19 atoms / cm 3 or more, or 3.0×10 20 atoms / cm 3 The oxide film is one having the above-mentioned properties. The surface temperature of the film during the TDS analysis is preferably in the range of 100° C. or more and 700° C. or less, or 100° C. or more and 400° C. or less.

[0187] In addition, the oxide 530 may be brought into contact with the insulator having the excess oxygen region and subjected to one or more of heat treatment, microwave treatment, and RF treatment. By carrying out such treatment, water or hydrogen in the oxide 530 can be removed. For example, a reaction occurs in the oxide 530 that breaks the bond of VoH, in other words, "V O The reaction "H → Vo + H" occurs, and the hydrogen can be dehydrogenated. Some of the hydrogen generated at this time may combine with oxygen to become H2O and be removed from the oxide 530 or the insulator near the oxide 530. Some of the hydrogen may also be gettered to the conductor 542.

[0188] In addition, the microwave treatment is preferably performed using, for example, a device having a power source that generates high-density plasma or a device having a power source that applies RF to the substrate side. For example, high-density oxygen radicals can be generated by using a gas containing oxygen and high-density plasma, and the oxygen radicals generated by the high-density plasma can be efficiently introduced into the oxide 530 or an insulator near the oxide 530 by applying RF to the substrate side. In addition, the pressure of the microwave treatment may be set to 133 Pa or more, preferably 200 Pa or more, and more preferably 400 Pa or more. In addition, for example, oxygen and argon are used as gases to be introduced into the microwave treatment device, and the oxygen flow rate ratio (O2 / (O2+Ar)) is 50% or less, preferably 10% or more and 30% or less.

[0189] In addition, in a manufacturing process of the transistor 500, it is preferable to perform heat treatment while the surface of the oxide 530 is exposed. The heat treatment may be performed, for example, at a temperature of 100° C. or higher and 450° C. or lower, more preferably 350° C. or higher and 400° C. or lower. Note that the heat treatment is performed in an atmosphere of nitrogen gas or an inert gas, or an atmosphere containing an oxidizing gas at 10 ppm or higher, 1% or higher, or 10% or higher. For example, the heat treatment is preferably performed in an oxygen atmosphere. In this way, oxygen is supplied to the oxide 530 to reduce oxygen deficiencies (V O) can be reduced. The heat treatment may be performed under reduced pressure. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas in order to compensate for the desorbed oxygen after the heat treatment in a nitrogen gas or inert gas atmosphere. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas in order to compensate for the desorbed oxygen. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas in succession to a heat treatment in a nitrogen gas or inert gas atmosphere.

[0190] By subjecting the oxide 530 to oxygen addition treatment, the oxygen vacancies in the oxide 530 can be repaired by the supplied oxygen, in other words, the reaction of "Vo+O→null" can be promoted. Furthermore, the supplied oxygen reacts with the hydrogen remaining in the oxide 530, and the hydrogen can be removed as H2O (dehydrated). As a result, the hydrogen remaining in the oxide 530 recombines with the oxygen vacancies to form V O The formation of H can be suppressed.

[0191] When the insulator 524 has an excess oxygen region, it is preferable that the insulator 522 has a function of suppressing the diffusion of oxygen (eg, oxygen atoms, oxygen molecules, etc.) (the oxygen is less likely to permeate).

[0192] The insulator 522 preferably has a function of suppressing diffusion of oxygen and impurities, so that oxygen contained in the oxide 530 does not diffuse toward the insulator 520. Furthermore, reaction of the conductor 503 with the insulator 524 or oxygen contained in the oxide 530 can be suppressed.

[0193] The insulator 522 is preferably a single layer or a multilayer insulator containing a so-called high-k material, such as aluminum oxide, hafnium oxide, oxide containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As transistors become smaller and more highly integrated, problems such as leakage current may occur due to the thinning of the gate insulating film. By using a high-k material for the insulator that functions as the gate insulating film, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0194] In particular, it is preferable to use an insulator containing an oxide of one or both of aluminum and hafnium, which are insulating materials having a function of suppressing the diffusion of impurities and oxygen (the oxygen is unlikely to permeate through them). As an insulator containing an oxide of one or both of aluminum and hafnium, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like. When the insulator 522 is formed using such a material, the insulator 522 functions as a layer that suppresses the release of oxygen from the oxide 530 and the intrusion of impurities such as hydrogen into the oxide 530 from the periphery of the transistor 500.

[0195] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the above insulators.

[0196] In addition, the insulator 520 is preferably thermally stable. For example, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In addition, by combining a high-k material insulator with silicon oxide or silicon oxynitride, it is possible to obtain the insulator 520 having a thermally stable and high dielectric constant laminate structure.

[0197] 18A and 18B, the second gate insulating film has a three-layer stack structure, and includes insulators 520, 522, and 524. However, the second gate insulating film may have a single layer, two layers, or four or more layers. In this case, the second gate insulating film is not limited to a stack structure made of the same material, and may have a stack structure made of different materials.

[0198] In the transistor 500, it is preferable to use a metal oxide that functions as an oxide semiconductor for the oxide 530 including the channel formation region. For example, a metal oxide such as In-M-Zn oxide (wherein the element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used as the oxide 530. In particular, the In-M-Zn oxide that can be used as the oxide 530 is preferably a c-axis aligned crystalline oxide semiconductor (CAAC-OS). Alternatively, it is preferably a cloud-aligned composite oxide semiconductor (CAC-OS). Note that CAAC represents an example of a crystal structure, and CAC represents an example of a function or material structure. In-Ga oxide or In-Zn oxide may be used as the oxide 530.

[0199] CAC-OS may be called CAC-metal oxide. A part of the CAC-OS or CAC-metal oxide has a conductive function, and a part of the CAC-OS or CAC-metal oxide has an insulating function, and the whole of the CAC-OS or CAC-metal oxide has a semiconductor function. When the CAC-OS or CAC-metal oxide is used in a channel forming region of a transistor, the conductive function is a function of flowing electrons (or holes) as carriers, and the insulating function is a function of not flowing electrons as carriers. By making the conductive function and the insulating function act complementarily, the CAC-OS or CAC-metal oxide can be given a switching function (a function of turning on / off). By separating the respective functions in the CAC-OS or CAC-metal oxide, both functions can be maximized.

[0200] Moreover, the CAC-OS or CAC-metal oxide has a conductive region and an insulating region. The conductive region has the above-mentioned conductive function, and the insulating region has the above-mentioned insulating function. In addition, in the material, the conductive region and the insulating region may be separated at the nanoparticle level. In addition, the conductive region and the insulating region may be unevenly distributed in the material. In addition, the conductive region may be observed to be connected in a cloud shape with a blurred periphery.

[0201] In addition, in the CAC-OS or CAC-metal oxide, the conductive regions and the insulating regions may each be dispersed in the material with a size of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm.

[0202] In addition, the CAC-OS or CAC-metal oxide is composed of components having different band gaps. For example, the CAC-OS or CAC-metal oxide is composed of a component having a wide gap due to an insulating region and a component having a narrow gap due to a conductive region. In this configuration, when carriers are caused to flow, the carriers mainly flow in the component having the narrow gap. In addition, the component having the narrow gap acts complementarily on the component having the wide gap, and carriers also flow in the component having the wide gap in conjunction with the component having the narrow gap. Therefore, when the above CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, a high current driving force in the on state of the transistor, that is, a large on-current and a high field effect mobility can be obtained.

[0203] That is, CAC-OS or CAC-metal oxide can also be called a matrix composite or a metal matrix composite.

[0204] Metal oxides that function as oxide semiconductors are classified into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors, such as CAAC-OS, polycrystalline oxide semiconductors, nanocrystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0205] CAAC-OS has a c-axis orientation and a crystal structure in which multiple nanocrystals are connected in the ab-plane direction and have a distortion. The distortion refers to a portion where the lattice orientation changes between a region with a uniform lattice arrangement and a region with a different uniform lattice arrangement in the region where multiple nanocrystals are connected.

[0206] Nanocrystals are basically hexagonal, but may be non-regular hexagonal. In addition, the lattice arrangement may be pentagonal or heptagonal due to the distortion. In CAAC-OS, it is difficult to confirm clear grain boundaries even near the distortion. In other words, it is found that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is because CAAC-OS can tolerate distortion due to the lack of dense arrangement of oxygen atoms in the ab-plane direction and the change in the bond distance between atoms due to the substitution of metal elements.

[0207] CAAC-OS also tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter, In layer) and a layer containing element M, zinc, and oxygen (hereinafter, (M, Zn) layer) are stacked. Note that indium and element M can be substituted for each other, and when element M in an (M, Zn) layer is substituted for indium, it can also be expressed as an (In, M, Zn) layer. When indium in an In layer is substituted for element M, it can also be expressed as an (In, M) layer.

[0208] CAAC-OS is a metal oxide with high crystallinity. On the other hand, it is difficult to confirm clear crystal boundaries in CAAC-OS, so it can be said that the decrease in electron mobility caused by crystal boundaries is unlikely to occur. In addition, since the crystallinity of metal oxides can be decreased by the inclusion of impurities or the generation of defects, CAAC-OS can be said to be a metal oxide with few impurities and defects (oxygen vacancies, etc.). Therefore, metal oxides with CAAC-OS have stable physical properties. As a result, metal oxides with CAAC-OS are resistant to heat and highly reliable.

[0209] The nc-OS has periodic atomic arrangement in a microscopic region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In addition, the nc-OS does not show regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is seen throughout the film. Therefore, depending on the analysis method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor.

[0210] In-Ga-Zn oxide (also called "IGZO"), a type of metal oxide containing indium, gallium, and zinc, may have a stable structure when made into the above-mentioned nanocrystals. In particular, since IGZO tends to have difficulty in crystal growth in the atmosphere, it may be structurally more stable to make it into small crystals (for example, the above-mentioned nanocrystals) rather than large crystals (here, crystals of several mm or several cm).

[0211] The a-like OS is a metal oxide having a structure between the nc-OS and an amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS.

[0212] Oxide semiconductors (metal oxides) have various structures and each structure has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[0213] In addition, it is preferable to use a metal oxide with a low carrier concentration for the transistor 500. In order to reduce the carrier concentration of the metal oxide, the impurity concentration in the metal oxide may be reduced to reduce the defect state density. In this specification and the like, a low impurity concentration and a low defect state density are referred to as high purity intrinsic or substantially high purity intrinsic. Note that examples of impurities in the metal oxide include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0214] In particular, hydrogen contained in metal oxide reacts with oxygen that bonds to metal atoms to form water, which may cause oxygen vacancies in the metal oxide. If oxygen vacancies are present in the channel formation region in the metal oxide, the transistor may have normally-on characteristics. Furthermore, defects in which hydrogen has entered the oxygen vacancies may function as donors and generate electrons that serve as carriers. In addition, some of the hydrogen may bond with oxygen that bonds to metal atoms to generate electrons that serve as carriers. Therefore, transistors using metal oxides that contain a large amount of hydrogen tend to have normally-on characteristics.

[0215] A defect in which hydrogen has entered an oxygen vacancy can function as a donor for a metal oxide. However, it is difficult to quantitatively evaluate the defect. Therefore, in a metal oxide, the carrier concentration may be used instead of the donor concentration. Therefore, in this specification, the carrier concentration assuming a state in which no electric field is applied may be used as a parameter of the metal oxide, instead of the donor concentration. In other words, the "carrier concentration" described in this specification may be rephrased as the "donor concentration".

[0216] Therefore, when a metal oxide is used for the oxide 530, it is preferable that hydrogen in the metal oxide is reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5×10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 By using a metal oxide in which impurities such as hydrogen are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0217] In addition, when a metal oxide is used for the oxide 530, the carrier concentration of the metal oxide in the channel formation region is 1×10 18 cm -3 It is preferable that the value is less than 1×10 17 cm -3 More preferably, it is less than 1×10 16 cm -3 More preferably, it is less than 1×10 13 cm -3 More preferably, it is less than 1×10 12 cm -3 The lower limit of the carrier concentration of the metal oxide in the channel formation region is not particularly limited, but is preferably, for example, 1×10 -9 cm -3 It can be said that:

[0218] Furthermore, when a metal oxide is used for the oxide 530, contact between the conductor 542 (conductor 542a and conductor 542b) and the oxide 530 may cause oxygen in the oxide 530 to diffuse into the conductor 542, resulting in the oxidation of the conductor 542. The oxidation of the conductor 542 is likely to result in a decrease in the conductivity of the conductor 542. The diffusion of oxygen in the oxide 530 into the conductor 542 can be rephrased as the conductor 542 absorbing the oxygen in the oxide 530.

[0219] Furthermore, oxygen in the oxide 530 may diffuse into the conductor 542 (conductor 542a and conductor 542b), forming a foreign layer between the conductor 542a and the oxide 530b and between the conductor 542b and the oxide 530b. The foreign layer contains more oxygen than the conductor 542, and is therefore presumed to have insulating properties. In this case, the three-layer structure of the conductor 542, the foreign layer, and the oxide 530b can be regarded as a three-layer structure made of a metal-insulator-semiconductor, and may be called a MIS (Metal-Insulator-Semiconductor) structure or a diode junction structure mainly based on the MIS structure.

[0220] In addition, the above-mentioned different layer is not limited to being formed between the conductor 542 and the oxide 530b. For example, the different layer may be formed between the conductor 542 and the oxide 530c, between the conductor 542 and the oxide 530b, and between the conductor 542 and the oxide 530c.

[0221] 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. In this manner, by using a metal oxide with a wide band gap, the off-state current of the transistor can be reduced.

[0222] The oxide 530 has the oxide 530a below the oxide 530b, so that the diffusion of impurities from components formed below the oxide 530a to the oxide 530b can be suppressed. Also, the oxide 530 has the oxide 530c on the oxide 530b, so that the diffusion of impurities from components formed above the oxide 530c to the oxide 530b can be suppressed.

[0223] The oxide 530 preferably has a laminated structure of a plurality of oxide layers with different atomic ratios of each metal atom. Specifically, in the metal oxide used for the oxide 530a, the atomic ratio of element M among the constituent elements is preferably larger than the atomic ratio of element M among the constituent elements in the metal oxide used for the oxide 530b. In addition, in the metal oxide used for the oxide 530a, the atomic ratio of element M to In is preferably larger than the atomic ratio of element M to In in the metal oxide used for the oxide 530b. In addition, in the metal oxide used for the oxide 530b, the atomic ratio of In to element M is preferably larger than the atomic ratio of In to element M in the metal oxide used for the oxide 530a. In addition, the oxide 530c can use a metal oxide that can be used for the oxide 530a or the oxide 530b.

[0224] In addition, the energy of the conduction band minimum of the oxide 530a and the oxide 530c is preferably higher than that of the oxide 530b, or in other words, the electron affinity of the oxide 530a and the oxide 530c is preferably smaller than that of the oxide 530b.

[0225] Here, the energy level of the conduction band minimum changes gradually at the junction of the oxide 530a, the oxide 530b, and the oxide 530c. In other words, it can be said that the energy level of the conduction band minimum at the junction of the oxide 530a, the oxide 530b, and the oxide 530c changes continuously or is a continuous junction. To achieve this, it is preferable to reduce the defect level density of the mixed layer formed at the interface between the oxide 530a and the oxide 530b and the interface between the oxide 530b and the oxide 530c.

[0226] Specifically, the oxides 530a and 530b, and the oxides 530b and 530c have a common element other than oxygen (as a main component), so that a mixed layer with a low density of defect states can be formed. For example, when the oxide 530b is an In-Ga-Zn oxide, the oxides 530a and 530c may be made of an In-Ga-Zn oxide, a Ga-Zn oxide, or a gallium oxide.

[0227] At this time, the main carrier path is the oxide 530b. 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. Therefore, the effect of interface scattering on carrier conduction is reduced, and the transistor 500 can obtain a high on-current.

[0228] Conductors 542a and 542b functioning as a source electrode and a drain electrode are provided on the oxide 530b. As the conductors 542a and 542b, it is preferable to use 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, an alloy containing the above-mentioned metal elements as a component, or an alloy combining the above-mentioned metal elements. For example, it is preferable to use 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, an oxide containing lanthanum and nickel, or the like. 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 conductive materials that are difficult to oxidize, or materials that maintain conductivity even when oxygen is absorbed, and are therefore preferable.Furthermore, metal nitride films such as tantalum nitride are preferable because they have barrier properties against hydrogen or oxygen.

[0229] 18, the conductor 542a and the conductor 542b are shown as having a single layer structure, but may have a laminated structure of two or more layers. For example, a tantalum nitride film and a tungsten film may be laminated. A titanium film and an aluminum film may be laminated. A two-layer structure in which an aluminum film is laminated on a tungsten film, a two-layer structure in which a copper film is laminated on a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is laminated on a titanium film, or a two-layer structure in which a copper film is laminated on a tungsten film may be used.

[0230] In addition, there are three-layer structures in which a titanium film or titanium nitride film is laminated with an aluminum film or copper film on the titanium film or titanium nitride film, and a titanium film or titanium nitride film is further formed thereon, and a three-layer structure in which a molybdenum film or molybdenum nitride film is laminated with an aluminum film or copper film 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 be used.

[0231] 18A, 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 the source region and the 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.

[0232] 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 a metal contained in the conductor 542a (conductor 542b) and a component 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.

[0233] The insulator 544 is provided to cover the conductor 542a and the conductor 542b and suppresses oxidation of the conductor 542a and the conductor 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.

[0234] 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.

[0235] 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 in a heat treatment in a later process. Note that the insulator 544 is not an essential component when the conductors 542a and 542b are made of a material having oxidation resistance or when the conductivity does not decrease significantly even when oxygen is absorbed. It may be designed appropriately depending on the desired transistor characteristics.

[0236] 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 545. The insulator 580 can also prevent the conductor 560 from being oxidized by excess oxygen contained in the insulator 580.

[0237] The insulator 545 functions as a first gate insulating film. The insulator 545 is preferably disposed in contact with the inside (top and side surfaces) of the oxide 530c. The insulator 545 is preferably formed using an insulator that contains excess oxygen and releases oxygen by heating, similar to the insulator 524 described above.

[0238] 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.

[0239] By providing an insulator that releases oxygen when heated as the insulator 545 in contact with the top surface of the oxide 530c, oxygen can be effectively supplied from the insulator 545 to the channel formation region of the oxide 530b through the oxide 530c. Similarly to the insulator 524, the concentration of impurities such as water or hydrogen in the insulator 545 is preferably reduced. The thickness of the insulator 545 is preferably 1 nm or more and 20 nm or less.

[0240] Furthermore, in order to efficiently supply excess oxygen contained in the insulator 545 to the oxide 530, a metal oxide may be provided between the insulator 545 and the conductor 560. The metal oxide preferably suppresses oxygen diffusion from the insulator 545 to the conductor 560. By providing a metal oxide that suppresses oxygen diffusion, the diffusion of excess oxygen from the insulator 545 to the conductor 560 can be suppressed. That is, a decrease in the amount of excess oxygen supplied to the oxide 530 can be suppressed. Furthermore, oxidation of the conductor 560 due to the excess oxygen can be suppressed. As the metal oxide, a material that can be used for the insulator 544 can be used.

[0241] The insulator 545 may have a layered structure, similar to the second gate insulating film. As transistors become smaller and more highly integrated, problems such as leakage current may occur due to the thinning of the gate insulating film. Therefore, by making the insulator that functions as the gate insulating film have a layered structure of a high-k material and a thermally stable material, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. In addition, a layered structure that is thermally stable and has a high relative dielectric constant can be obtained.

[0242] Although the conductor 560 functioning as the first gate electrode is shown as having a two-layer structure in FIGS. 18A and 18B, it may have a single-layer structure or a laminated structure of three or more layers.

[0243] The conductor 560a is preferably made of a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms. Alternatively, it is preferably made of a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.). The conductor 560a has a function of suppressing the diffusion of oxygen, so that it is possible to suppress the conductor 560b from being oxidized by the oxygen contained in the insulator 545 and its conductivity from decreasing. As a conductive material having a function of suppressing the diffusion of oxygen, for example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide is preferably used. In addition, an oxide semiconductor applicable to the oxide 530 can be used as the conductor 560a. In that case, the conductor 560b can be formed by a sputtering method to reduce the electrical resistance value of the conductor 560a and make it a conductor. This can be called an OC (Oxide Conductor) electrode.

[0244] The conductor 560b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor 560b also functions as wiring, so 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, for example, a layered structure of titanium or titanium nitride and the above conductive material.

[0245] The insulator 580 is provided on the conductor 542a and the conductor 542b via the insulator 544. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 preferably has silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine has been added, silicon oxide to which carbon has been added, silicon oxide to which carbon and nitrogen have been added, silicon oxide having voids, or a resin. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, silicon oxide and silicon oxide having voids are preferable because they can easily form an excess oxygen region in a later step.

[0246] The insulator 580 preferably has an excess oxygen region. By providing the insulator 580, which releases oxygen when heated, 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.

[0247] The opening of insulator 580 is formed to overlap the region between conductor 542a and conductor 542b, so that conductor 560 is formed so as to be embedded in the opening of insulator 580 and the region sandwiched between conductor 542a and conductor 542b.

[0248] In miniaturizing a semiconductor device, 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 for that purpose, 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, so that even if the conductor 560 has a shape with a high aspect ratio, the conductor 560 can be formed without collapsing during the process.

[0249] The insulator 574 is preferably provided in contact with a top surface of the insulator 580, a top surface of the conductor 560, and a top surface of the insulator 545. By forming the insulator 574 by a sputtering method, an excess oxygen region can be provided in the insulator 545 and the insulator 580. This allows oxygen to be supplied from the excess oxygen region into the oxide 530.

[0250] 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.

[0251] In particular, aluminum oxide has high barrier properties and can suppress the diffusion of hydrogen and nitrogen even in a thin film with a thickness of 0.5 nm to 3.0 nm. Therefore, aluminum oxide formed by sputtering can function as a barrier film against impurities such as hydrogen as well as an oxygen source.

[0252] 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.

[0253] Conductor 540a and conductor 540b are arranged in openings formed in insulator 581, insulator 574, insulator 580, and insulator 544. Conductor 540a and conductor 540b are provided facing each other with conductor 560 interposed therebetween. Conductor 540a and conductor 540b have the same configuration as conductor 546 and conductor 548, which will be described later.

[0254] An insulator 582 is provided over the insulator 581. The insulator 582 is preferably made of a substance that has a barrier property against oxygen and hydrogen. Therefore, the insulator 582 can be made of a material similar to that of the insulator 514. For example, the insulator 582 is preferably made of a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0255] In particular, aluminum oxide has a high blocking effect of preventing the film from permeating both oxygen and impurities such as hydrogen and moisture, which are factors that cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the transistor manufacturing process. In addition, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0256] An insulator 586 is provided over the insulator 582. The insulator 586 can be formed using a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, parasitic capacitance between wirings can be reduced. For example, a silicon oxide film, a silicon oxynitride film, or the like can be used as the insulator 586.

[0257] In addition, conductors 546, 548, etc. are embedded in insulators 520, 522, 524, 544, 580, 574, 581, 582, and 586.

[0258] The conductor 546 and the conductor 548 function as a plug or wiring that connects to the capacitor 600, the transistor 500, or the transistor 550. The conductor 546 and the conductor 548 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0259] After the transistor 500 is formed, an opening may be formed to surround the transistor 500, and an insulator having a high barrier property against hydrogen or water may be formed to cover the opening. By surrounding the transistor 500 with the insulator having a high barrier property, it is possible to prevent moisture and hydrogen from entering from the outside. Alternatively, a plurality of transistors 500 may be collectively surrounded by an insulator having a high barrier property against hydrogen or water. When an opening is formed to surround the transistor 500, for example, it is preferable to form an opening that reaches the insulator 522 or the insulator 514 and form the insulator having a high barrier property in contact with the insulator 522 or the insulator 514, since this can serve as part of the manufacturing process of the transistor 500. Note that as the insulator having a high barrier property against hydrogen or water, for example, a material similar to the insulator 522 or the insulator 514 may be used.

[0260] Subsequently, a capacitor 600 is provided above the transistor 500. The capacitor 600 has a conductor 610, a conductor 620, and an insulator 630.

[0261] A conductor 612 may be provided over the conductor 546 and the conductor 548. The conductor 612 functions as a plug or a wiring connected to the transistor 500. The conductor 610 functions as an electrode of the capacitor 600. Note that the conductor 612 and the conductor 610 can be formed at the same time.

[0262] A metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium, or a metal nitride film containing the above-mentioned element (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film), etc. can be used for the conductor 612 and the conductor 610. Alternatively, a conductive material such as indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, or indium tin oxide with added silicon oxide can also be used.

[0263] In this embodiment, the conductor 612 and the conductor 610 have a single-layer structure, but the present invention is not limited to this structure and may have a stacked structure of two or more layers. For example, a conductor having a barrier property and a conductor having high adhesion to the conductor having high conductivity may be formed between a conductor having a barrier property and a conductor having high conductivity.

[0264] The conductor 620 is provided so as to overlap with the conductor 610 with the insulator 630 interposed therebetween. Note that the conductor 620 can be made of a conductive material such as a metal material, an alloy material, or a metal oxide material. It is preferable to use a high melting point material such as tungsten or molybdenum that has both heat resistance and conductivity, and it is particularly preferable to use tungsten. When the conductor 620 is formed simultaneously with other components such as a conductor, a low resistance metal material such as Cu (copper) or Al (aluminum) may be used.

[0265] An insulator 640 is provided over the conductor 620 and the insulator 630. The insulator 640 can be provided using a material similar to that of the insulator 320. The insulator 640 may also function as a planarizing film that covers the uneven shape underneath.

[0266] With this structure, miniaturization or high integration can be achieved in a semiconductor device including a transistor including an oxide semiconductor.

[0267] Examples of the substrate that can be used in the semiconductor device according to one embodiment of the present invention include a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, a metal substrate (e.g., a stainless steel substrate, a substrate having stainless steel foil, a tungsten substrate, a substrate having tungsten foil, etc.), a semiconductor substrate (e.g., a single crystal semiconductor substrate, a polycrystalline semiconductor substrate, a compound semiconductor substrate, etc.), and an SOI (Silicon on Insulator) substrate. A plastic substrate having heat resistance that can withstand the processing temperature of this embodiment may also be used. Examples of the glass substrate include barium borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, and soda-lime glass. In addition, crystallized glass and the like can be used.

[0268] Alternatively, a flexible substrate, a laminated film, paper containing a fibrous material, or a base film can be used as the substrate. Examples of flexible substrates, laminated films, base films, etc. include the following. For example, there are plastics such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Alternatively, there are synthetic resins such as acrylic. Alternatively, there are polypropylene, polyester, polyvinyl fluoride, or polyvinyl chloride. Alternatively, there are polyamide, polyimide, aramid, epoxy, inorganic deposition film, or paper. In particular, by manufacturing transistors using a semiconductor substrate, a single crystal substrate, or an SOI substrate, etc., it is possible to manufacture transistors with small variations in characteristics, size, or shape, high current capacity, and small size. When a circuit is constructed using such transistors, it is possible to reduce the power consumption of the circuit or to increase the integration of the circuit.

[0269] Alternatively, a flexible substrate may be used as the substrate, and transistors, resistors, and / or capacitors may be formed directly on the flexible substrate. Alternatively, a peeling layer may be provided between the substrate and the transistors, resistors, and / or capacitors. The peeling layer can be used to separate a semiconductor device from the substrate after a part or whole of the semiconductor device is completed thereon, and transfer the semiconductor device to another substrate. In this case, the transistors, resistors, and / or capacitors can be transferred to a substrate having poor heat resistance or a flexible substrate. For the peeling layer, for example, a laminated structure of inorganic films of a tungsten film and a silicon oxide film, a structure in which an organic resin film such as polyimide is formed on a substrate, a silicon film containing hydrogen, or the like can be used.

[0270] That is, the semiconductor device may be formed on a certain substrate, and then the semiconductor device may be transferred to another substrate. Examples of substrates onto which the semiconductor device may be transferred include substrates on which the above-mentioned transistors can be formed, as well as paper substrates, cellophane substrates, aramid film substrates, polyimide film substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester), or regenerated fibers (acetate, cupra, rayon, regenerated polyester), etc.), leather substrates, or rubber substrates. By using these substrates, it is possible to manufacture semiconductor devices that are flexible, that are not easily broken, that have heat resistance, and that are lightweight or thin.

[0271] By providing the semiconductor device on a flexible substrate, for example, even if the secondary battery 300 has a curved or bent shape, the semiconductor device can be provided along the outer shape of the secondary battery. For example, when the secondary battery 300 has a cylindrical shape, the semiconductor device can be provided so as to be wrapped around the side surface of the secondary battery.

[0272] <Transistor modification 1> 19A and 19B is a modification of the transistor 500 having the structure shown in FIG. 18A and 18B. FIG. 19A is a cross-sectional view of the transistor 500A in the channel length direction, and FIG. 19B is a cross-sectional view of the transistor 500A in the channel width direction. Note that the structures shown in FIG. 19A and 19B can also be applied to other transistors included in the semiconductor device of one embodiment of the present invention, such as the transistor 550.

[0273] 19A and 19B includes an insulator 552, an insulator 513, and an insulator 404, and the oxide 530c is a stack of oxides 530c1 and 530c2. The transistor 500A also includes an insulator 552 in contact with a side surface of the conductor 540a, and an insulator 552 in contact with a side surface of the conductor 540b. The transistor 500A also includes an insulator 520 in contact with a side surface of the conductor 540b. The transistor 500A also includes an insulator 520 in contact with a side surface of the conductor 540b.

[0274] 19A and 19B, an insulator 513 is provided over an insulator 512. Furthermore, an insulator 404 is provided over the insulator 574 and the insulator 513.

[0275] 19A and 19B, the insulator 514, the insulator 516, the insulator 522, the insulator 524, the insulator 544, the insulator 580, and the insulator 574 are patterned, and the insulator 404 covers them. That is, the insulator 404 contacts the top surface of the insulator 574, the side surface of the insulator 574, the side surface of the insulator 580, the side surface of the insulator 544, the side surface of the insulator 524, the side surface of the insulator 522, the side surface of the insulator 516, the side surface of the insulator 514, and the top surface of the insulator 513. As a result, the oxide 530 and the like are isolated from the outside by the insulator 404 and the insulator 513.

[0276] The insulator 513 and the insulator 404 preferably have a high function of suppressing diffusion of hydrogen (for example, at least one of hydrogen atoms, hydrogen molecules, and the like) or water molecules. For example, the insulator 513 and the insulator 404 are preferably made of silicon nitride or silicon nitride oxide, which are materials with high hydrogen barrier properties. This can suppress diffusion of hydrogen and the like into the oxide 530, thereby suppressing deterioration in the characteristics of the transistor 500A. Therefore, the reliability of the semiconductor device of one embodiment of the present invention can be improved.

[0277] The insulator 552 is provided in contact with the insulator 581, the insulator 404, the insulator 574, the insulator 580, and the insulator 544. The insulator 552 preferably has a function of suppressing diffusion of hydrogen or water molecules. For example, the insulator 552 is preferably made of an insulator having a high hydrogen barrier property, such as silicon nitride, aluminum oxide, or silicon nitride oxide. In particular, silicon nitride is preferably used as the insulator 552 because it has a high hydrogen barrier property. By using a material having a high hydrogen barrier property as the insulator 552, impurities such as water or hydrogen can be suppressed from diffusing from the insulator 580 or the like to the oxide 530 through the conductor 540a and the conductor 540b. Furthermore, oxygen contained in the insulator 580 can be suppressed from being absorbed by the conductor 540a and the conductor 540b. As described above, the reliability of the semiconductor device of one embodiment of the present invention can be improved.

[0278] The oxide 530c1 contacts the top surface of the insulator 524, the side surface of the oxide 530a, the top surface and side surface of the oxide 530b, the side surfaces of the conductors 542a and 542b, the side surface of the insulator 544, and the side surface of the insulator 580 (see FIG. 19B). The oxide 530c2 contacts the insulator 545.

[0279] The oxide 530c1 may be, for example, an In-Zn oxide. The oxide 530c2 may be the same material as that used for the oxide 530c when the oxide 530c has a single layer structure. For example, the oxide 530c2 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.

[0280] By forming the oxide 530c in a two-layer structure of the oxide 530c1 and the oxide 530c2, the on-current of the transistor can be increased compared to when the oxide 530c is in a single-layer structure. Therefore, the transistor can be, for example, a power MOS transistor.

[0281] <Transistor modification 2> A configuration example of a transistor 500B will be described with reference to Figures 20A, 20B, and 20C. Figure 20A is a top view of the transistor 500B. Figure 20B is a cross-sectional view of the L1-L2 portion shown by the dashed line in Figure 20A. Figure 20C is a cross-sectional view of the W1-W2 portion shown by the dashed line in Figure 20A. Note that in the top view of Figure 20A, some elements are omitted for clarity.

[0282] The transistor 500B is a modified example of the transistor 500 and can be substituted for the transistor 500. Therefore, in order to avoid repetition of description, the following description will mainly focus on the differences from the transistor 500.

[0283] The conductor 560 functioning as the first gate electrode has a conductor 560a and a conductor 560b on the conductor 560a. The conductor 560a is preferably made of a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms. Alternatively, it is preferably made of a conductive material having a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, and the like).

[0284] The conductor 560a has a function of suppressing oxygen diffusion, which improves the material selectivity of the conductor 560b. In other words, the presence of the conductor 560a suppresses oxidation of the conductor 560b, thereby preventing a decrease in electrical conductivity.

[0285] It is preferable to provide an insulator 544 so as to cover the top surface and side surface of the conductor 560, the side surface of the insulator 545, and the side surface of the oxide 530c. Note that the insulator 544 may be made of an insulating material having a function of suppressing the diffusion of impurities such as water or hydrogen, and oxygen. For example, it is preferable to use aluminum oxide or hafnium oxide. In addition, for example, metal oxides such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, or tantalum oxide, silicon nitride oxide, or silicon nitride may be used.

[0286] Providing the insulator 544 can suppress oxidation of the conductor 560. Furthermore, providing the insulator 544 can suppress diffusion of impurities such as water and hydrogen contained in the insulator 580 to the transistor 500B.

[0287] In the transistor 500B, the conductor 560 overlaps with part of the conductor 542a and part of the conductor 542b, and thus the parasitic capacitance of the transistor 500B is likely to be larger than that of the transistor 500. Thus, the operating frequency of the transistor 500B tends to be lower than that of the transistor 500. However, the productivity of the transistor 500B is higher than that of the transistor 500 because a step of forming an opening in the insulator 580 or the like and filling the conductor 560 and the insulator 545 is not required.

[0288] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0289] (Embodiment 5) In this embodiment, a configuration example of a battery that can be used for the secondary battery 300 will be described with reference to the drawings. In this embodiment, an example of a lithium ion secondary battery will be shown, but the battery that can be used for the secondary battery 300 is not limited to a lithium ion secondary battery.

[0290] [Cylindrical secondary battery] FIG. 21A is an external view of a cylindrical secondary battery 715. FIG. 21B is a schematic diagram showing a cross section of a cylindrical secondary battery 715. Inside a hollow cylindrical battery can 702, a battery element is provided in which a strip-shaped positive electrode 704 and a negative electrode 706 are wound with a separator 705 sandwiched therebetween. Although not shown, the battery element is wound around a center pin. One end of the battery can 702 is closed and the other end is open. For the battery can 702, metals such as nickel, aluminum, and titanium that are resistant to corrosion by the electrolyte, or alloys of these metals and other metals (for example, stainless steel, etc.) can be used. In addition, it is preferable to coat the battery can with nickel, aluminum, etc. to prevent corrosion by the electrolyte. Inside the battery can 702, the battery element in which the positive electrode, negative electrode, and separator are wound is sandwiched between a pair of opposing insulating plates 708 and 709. A non-aqueous electrolyte (not shown) is injected into the battery can 702 in which the battery element is provided. A secondary battery is composed of a positive electrode containing an active material such as lithium cobalt oxide (LiCoO2) or lithium iron phosphate (LiFePO4), a negative electrode made of a carbon material such as graphite capable of absorbing and releasing lithium ions, and a non-aqueous electrolyte in which an electrolyte made of a lithium salt such as LiBF4 or LiPF6 is dissolved in an organic solvent such as ethylene carbonate or diethyl carbonate.

[0291] Since the positive and negative electrodes used in a cylindrical secondary battery are wound, it is preferable to form an active material on both sides of the current collector. A positive electrode terminal (positive electrode current collector lead) 703 is connected to the positive electrode 704, and a negative electrode terminal (negative electrode current collector lead) 707 is connected to the negative electrode 706. Both the positive electrode terminal 703 and the negative electrode terminal 707 can be made of a metal material such as aluminum. The positive electrode terminal 703 is resistance-welded to a safety valve mechanism 712, and the negative electrode terminal 707 is resistance-welded to the bottom of the battery can 702. The safety valve mechanism 712 is electrically connected to the positive electrode cap 701 via a PTC element (Positive Temperature Coefficient) 711. The safety valve mechanism 712 cuts off the electrical connection between the positive electrode cap 701 and the positive electrode 704 when the rise in the internal pressure of the battery exceeds a predetermined threshold value. The PTC element 711 is a thermosensitive resistor whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current to prevent abnormal heat generation. Barium titanate (BaTiO3)-based semiconductor ceramics and the like can be used for the PTC element.

[0292] A lithium ion secondary battery using an electrolyte has a positive electrode, a negative electrode, a separator, an electrolyte, and an exterior body. In a lithium ion secondary battery, the anode (positive electrode) and the cathode (negative electrode) are interchanged during charging and discharging, and the oxidation reaction and the reduction reaction are interchanged, so the electrode with a high reaction potential is called the positive electrode, and the electrode with a low reaction potential is called the negative electrode. Therefore, in this specification, the positive electrode is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "negative electrode" or "- electrode (minus electrode)" whether during charging, discharging, when a reverse bias is applied, or when a charging current is applied. If the terms anode (positive electrode) and cathode (negative electrode) related to the oxidation reaction and reduction reaction are used, they may be reversed during charging and discharging, which may cause confusion. Therefore, the terms anode (positive electrode) and cathode (negative electrode) are not used in this specification. If the terms anode and cathode are used, it should be specified whether they are used during charging or discharging, and also whether they correspond to the positive electrode (plus) or negative electrode (minus).

[0293] In this embodiment, an example of a lithium ion secondary battery is shown, but the present invention is not limited to the lithium ion secondary battery, and a material having element A, element X, and oxygen can be used as a positive electrode material of the secondary battery. Element A is preferably one or more selected from elements of Group 1 and elements of Group 2. For example, alkali metals such as lithium, sodium, and potassium can be used as elements of Group 1. For example, calcium, beryllium, and magnesium can be used as elements of Group 2. For example, element X can be one or more selected from metal elements, silicon, and phosphorus. For example, element X is preferably one or more selected from cobalt, nickel, manganese, iron, and vanadium. Representative examples include lithium cobalt composite oxide (LiCoO2) and lithium iron phosphate (LiFePO4).

[0294] The negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may include a conductive assistant and a binder.

[0295] As the negative electrode active material, an element capable of carrying out a charge / discharge reaction by alloying / dealloying with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4700mAh / g.

[0296] The secondary battery preferably has a separator, which may be made of, for example, cellulose-containing fibers such as paper, nonwoven fabric, glass fiber, ceramics, or synthetic fibers such as nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, or polyurethane.

[0297] 21C illustrates a state in which the power receiving device 724 formed or fixed on a flexible substrate 721 is provided along a side surface of the secondary battery 715. The power receiving device 450 described in the above embodiment can be used as the power receiving device 724. By providing the power receiving device 724 on the flexible substrate 721, the power receiving device 724 can be provided along a curved surface of the cylindrical secondary battery 715. Thus, the space occupied by the power receiving device 724 can be reduced. Thus, electronic devices including the secondary battery 715 and the power receiving device 724 can be miniaturized.

[0298] [Flat-shaped secondary battery]

[0299] Next, an example of the internal configuration of the flat secondary battery 913 will be described.

[0300] 22A shows the configuration of a wound body 950 disposed inside a secondary battery 913. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 sandwiched therebetween, and the laminated sheet is wound. Note that the stack of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked a plurality of times.

[0301] The negative electrode 931 is electrically connected to one of the terminal 951 and the terminal 952 , and the positive electrode 932 is electrically connected to the other of the terminal 951 and the terminal 952 .

[0302] In FIG. 22B, the secondary battery 913 has a wound body 950 in which terminals 951 and 952 are provided inside a housing 930 (also referred to as an "exterior body"). The wound body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 contacts the housing 930, and the terminal 951 does not contact the housing 930 by using an insulating material or the like. Note that in FIG. 22B, the housing 930 is illustrated separately, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (such as aluminum) or a resin material.

[0303] An insulating material such as a metal material or an organic resin can be used for the housing 930. The housing 930 may be made of a film, in which case a charge control circuit formed on a flexible substrate may be provided on the film.

[0304] [Battery pack] Next, a battery pack 901 including a flat-shaped secondary battery 913 will be described. Fig. 23A is an external view of the secondary battery 913. The secondary battery 913 has a terminal 951 and a terminal 952. The terminal 951 is electrically connected to a positive electrode inside the secondary battery 913, and the terminal 952 is electrically connected to a negative electrode inside the secondary battery 913.

[0305] 23B is an external view of the power receiving device 900 and the layer 916. The power receiving device 900 includes a circuit 912 and an antenna 914, and is provided on a flexible substrate. The antenna 914 is electrically connected to the circuit 912. A terminal 971 and a terminal 972 are electrically connected to the circuit 912. The circuit 912 is electrically connected to the terminal 911.

[0306] The secondary battery 913 functions as a battery pack together with the power receiving device 900, the terminal 951, and the terminals 952 and 911.

[0307] The power receiving device 900 corresponds to, for example, the power receiving device 450 described in the above embodiment. The circuit 912 includes a power receiving circuit 451, a charge control circuit 452, a charge and discharge control circuit 453, and the like. The antenna 914 corresponds to the power receiving antenna 403 described in the above embodiment.

[0308] The antenna is not limited to a coil shape, and may be, for example, a wire shape or a plate shape. In addition, a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, a dielectric antenna, or the like may be used.

[0309] The terminal 911 is connected to, for example, a device to which power from the secondary battery is supplied, such as a display device, a sensor, or the like.

[0310] 23B has a function of blocking, for example, an electromagnetic field caused by the secondary battery 913. The layer 916 can be made of, for example, a magnetic material.

[0311] 23C shows a battery pack in which the power receiving device 900 is disposed on the secondary battery 913. The terminal 971 is electrically connected to the terminal 951, and the terminal 972 is electrically connected to the terminal 952. The layer 916 is disposed between the power receiving device 900 and the secondary battery 913.

[0312] It is preferable to provide the power receiving device 900 on a flexible substrate. By using a flexible substrate, it is possible to realize a thin power receiving device 900. In addition, as shown in Fig. 24D described later, the power receiving device 900 can be wound around a secondary battery.

[0313] Next, as another configuration example of the battery pack 901, a battery pack 901A will be described with reference to Fig. 24A to Fig. 24D. Fig. 24A is an external view of a secondary battery 913. The power receiving device 900 shown in Fig. 24B includes a circuit 912 and an antenna 914, similar to the power receiving device 900 shown in Fig. 23B. Fig. 24B also shows a layer 916.

[0314] As shown in FIG. 24C, the power receiving device 900 provided on a flexible substrate is bent to fit the shape of the secondary battery 913 and placed around the secondary battery, so that the power receiving device 900 can be wrapped around the secondary battery as shown in FIG. 24D.

[0315] Next, a battery pack 901B will be described with reference to Figures 25A to 25D as another configuration example of the battery pack 901. A secondary battery 913 shown in Figure 25A has an L-shape when viewed from one side.

[0316] Fig. 25B shows an example in which the flexible substrate on which the power receiving device 900 is provided has a notch. The notch may also be called a slit. The layer 916 shown in Fig. 25B has an L-shape, similar to the secondary battery 913 shown in Fig. 25A.

[0317] 25C and 25D, by having a cutout portion in the flexible substrate, a part of the power receiving device 900 (the area to the right of the cutout portion) can be wrapped around the back side of the L-shaped secondary battery 913. Note that Fig. 25C is a diagram showing a state in the middle of wrapping a part of the power receiving device 900 around the L-shaped secondary battery 913, and Fig. 25D is a diagram showing a state after wrapping.

[0318] By providing the power receiving device 900 on a flexible substrate, the power receiving device 900 can be provided along the shape of the secondary battery 913. Therefore, the space occupied by the power receiving device 900 can be reduced. Therefore, the battery pack can be made smaller. In addition, the battery pack can be made lighter. An electronic device including a battery pack according to one embodiment of the present invention can be made smaller. An electronic device including a battery pack according to one embodiment of the present invention can be made lighter.

[0319] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0320] (Embodiment 6) In this embodiment, a positive electrode active material according to one embodiment of the present invention will be described.

[0321] In this specification and the like, segregation refers to a phenomenon in which a certain element (eg, B) is spatially non-uniformly distributed in a solid composed of a plurality of elements (eg, A, B, C).

[0322] In this specification, the surface layer of a particle of an active material or the like refers to a region from the surface to a depth of about 10 nm. Surfaces caused by cracks or chips may also be called the surface. The region deeper than the surface layer is called the interior.

[0323] In this specification, the layered rock-salt type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock-salt type ion arrangement in which cations and anions are alternately arranged, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. Defects such as deficiencies of cations or anions may also be present. Strictly speaking, the layered rock-salt type crystal structure may have a distorted rock-salt type crystal lattice.

[0324] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately. Note that there may be a deficiency of cations or anions.

[0325] In the present specification and the like, the pseudo-spinel type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure that has a space group of R-3m, is not a spinel type crystal structure, but has ions of cobalt, magnesium, etc. occupying 6-coordination oxygen positions, and has a symmetry of the arrangement of cations similar to that of the spinel type. In the pseudo-spinel type crystal structure, a light element such as lithium may occupy 4-coordination oxygen positions, and in this case, the arrangement of ions also has a symmetry similar to that of the spinel type.

[0326] It can also be said that the pseudo-spinel type crystal structure is similar to the CdCl2 type crystal structure, although it has random Li between the layers. This CdCl2 type-like crystal structure was observed when lithium nickel oxide was charged to a charge depth of 0.94 (Li 0.06 The crystal structure is close to that of lithium cobalt oxide (NiO2), but it is known that pure lithium cobalt oxide or layered rock salt type positive electrode active materials that contain a large amount of cobalt do not usually have this crystal structure.

[0327] The layered rock salt crystal and the anions of the rock salt crystal have a cubic close-packed structure (face-centered cubic lattice structure). It is presumed that the anions of the pseudo-spinel crystal also have a cubic close-packed structure. When they contact, there is a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of the layered rock salt crystal and the pseudo-spinel crystal is R-3m, which is different from the space group Fm-3m (the space group of a general rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry) of the rock salt crystal, so the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt crystal and the pseudo-spinel crystal and the rock salt crystal. In this specification, when the orientation of the cubic close-packed structure formed by the anions is aligned in the layered rock salt crystal, the pseudo-spinel crystal, and the rock salt crystal, it may be said that the crystal orientation is approximately the same.

[0328] A secondary battery has, for example, a positive electrode and a negative electrode. A material constituting the positive electrode is a positive electrode active material. The positive electrode active material is, for example, a material that undergoes a reaction that contributes to the charge / discharge capacity. Note that the positive electrode active material may contain a material that does not contribute to the charge / discharge capacity.

[0329] In this specification etc., the positive electrode active material according to one embodiment of the present invention may be expressed as a positive electrode material, a positive electrode material for secondary batteries, or the like. In this specification etc., the positive electrode active material according to one embodiment of the present invention preferably has a compound. In this specification etc., the positive electrode active material according to one embodiment of the present invention preferably has a composition. In this specification etc., the positive electrode active material according to one embodiment of the present invention preferably has a composite.

[0330] <Cathode active material> By using the positive electrode active material according to one embodiment of the present invention, the capacity of a secondary battery can be increased and a decrease in the discharge capacity due to charge / discharge cycles can be suppressed.

[0331] [Composition of positive electrode active material] The positive electrode active material preferably contains a metal (hereinafter, referred to as element A) that serves as a carrier ion. As element A, for example, alkali metals such as lithium, sodium, potassium, etc., and Group 2 elements such as calcium, beryllium, magnesium, etc. can be used.

[0332] In the positive electrode active material, carrier ions are released from the positive electrode active material as the battery is charged. If the amount of element A released is large, the amount of ions contributing to the capacity of the secondary battery is large, and the capacity is increased. On the other hand, if the amount of element A released is large, the crystal structure of the compound of the positive electrode active material is easily broken. The break in the crystal structure of the positive electrode active material may lead to a decrease in the discharge capacity due to the charge-discharge cycle. When the positive electrode active material according to one embodiment of the present invention contains element X, the break in the crystal structure when carrier ions are released during charging of the secondary battery may be suppressed. For example, a part of element X is substituted at the position of element A. Elements such as magnesium, calcium, zirconium, lanthanum, and barium can be used as element X. For example, elements such as copper, potassium, sodium, and zinc can be used as element X. Two or more of the elements shown above may be used in combination as element X.

[0333] In addition, the positive electrode active material according to one embodiment of the present invention preferably contains a halogen in addition to the element X. It is preferable that the positive electrode active material according to one embodiment of the present invention contains a halogen such as fluorine or chlorine. When the positive electrode active material according to one embodiment of the present invention contains the halogen, the substitution of the element X at the position of the element A may be promoted.

[0334] The positive electrode active material according to an embodiment of the present invention has a metal (hereinafter, element M) whose valence changes with charging and discharging of the secondary battery. The element M is, for example, a transition metal. The positive electrode active material according to an embodiment of the present invention has, for example, one or more of cobalt, nickel, and manganese as the element M, and particularly has cobalt. In addition, an element that does not change valence and can have the same valence as the element M, such as aluminum, may be present at the position of the element M, more specifically, for example, a trivalent typical element. The aforementioned element X may be substituted at the position of the element M, for example. In addition, when the positive electrode active material according to an embodiment of the present invention is an oxide, the element X may be substituted at the position of oxygen.

[0335] As the positive electrode active material according to one embodiment of the present invention, for example, a lithium composite oxide having a layered rock salt crystal structure is preferably used. More specifically, for example, as the lithium composite oxide having a layered rock salt crystal structure, lithium cobalt oxide, lithium nickel oxide, lithium composite oxide having nickel, manganese, and cobalt, lithium composite oxide having nickel, cobalt, and aluminum, etc. can be used. In addition, these positive electrode active materials are preferably represented by the space group R-3m.

[0336] In a positive electrode active material having a layered rock salt crystal structure, the crystal structure may collapse when the charge depth is increased. Here, the collapse of the crystal structure may be, for example, a shift in the layers. If the collapse of the crystal structure is irreversible, the capacity of the secondary battery may decrease with repeated charging and discharging.

[0337] For example, even if the charge depth is deep, the above-mentioned layer shift is suppressed by the positive electrode active material according to one embodiment of the present invention having the element X. By suppressing the shift, the volume change during charging and discharging can be reduced. Therefore, the positive electrode active material according to one embodiment of the present invention can realize excellent cycle characteristics. In addition, the positive electrode active material according to one embodiment of the present invention can have a stable crystal structure in a high-voltage charged state. Therefore, the positive electrode active material according to one embodiment of the present invention may be less likely to cause a short circuit when a high-voltage charged state is maintained. In such a case, safety is further improved, which is preferable.

[0338] In the positive electrode active material according to one embodiment of the present invention, the change in crystal structure and the difference in volume per the same number of transition metal atoms between a fully discharged state and a high-voltage charged state are small.

[0339] The positive electrode active material according to one embodiment of the present invention has the chemical formula AM y O Z (y>0, z>0). For example, lithium cobalt oxide may be represented as LiCoO2. For example, lithium nickel oxide may be represented as LiNiO2.

[0340] In the positive electrode active material according to one embodiment of the present invention, which has an element X, when the charge depth is 0.8 or more, it is represented by the space group R-3m, and although it is not a spinel type crystal structure, ions of element M (e.g., cobalt), element X (e.g., magnesium), etc. occupy oxygen 6-coordination positions, and the arrangement of cations may have a symmetry similar to that of the spinel type. This structure is referred to as a pseudo-spinel type crystal structure in this specification. In addition, in the pseudo-spinel type crystal structure, a light element such as lithium may occupy oxygen 4-coordination positions, and in this case, the arrangement of ions also has a symmetry similar to that of the spinel type.

[0341] The structure of the positive electrode active material becomes unstable due to the elimination of carrier ions during charging. The pseudo-spinel crystal structure can be said to be a structure that can maintain high stability even when carrier ions are eliminated.

[0342] In the case where the charge depth of the present invention is high, by using the positive electrode active material having a pseudo-spinel structure in a secondary battery, the structure of the positive electrode active material is stable, for example, at a voltage of about 4.6 V based on the potential of lithium metal, more preferably at a voltage of about 4.65 V to 4.7 V, and capacity loss due to charging and discharging can be suppressed. Note that, in the case where graphite is used as the negative electrode active material in the secondary battery, the structure of the positive electrode active material is stable, for example, at a voltage of the secondary battery of 4.3 V to 4.5 V, more preferably at a voltage of 4.35 V to 4.55 V, and capacity loss due to charging and discharging can be suppressed.

[0343] It can also be said that the pseudo-spinel type crystal structure is similar to the CdCl2 type crystal structure, although it has random Li between the layers. This CdCl2 type-like crystal structure was observed when lithium nickel oxide was charged to a charge depth of 0.94 (Li 0.06 The crystal structure is close to that of lithium cobalt oxide (NiO2), but it is known that pure lithium cobalt oxide or layered rock salt type positive electrode active materials that contain a large amount of cobalt do not usually have this crystal structure.

[0344] The layered rock salt crystal and the anions of the rock salt crystal have a cubic close-packed structure (face-centered cubic lattice structure). It is presumed that the anions of the pseudo-spinel crystal also have a cubic close-packed structure. When they contact, there is a crystal plane where the orientation of the cubic close-packed structure formed by the anions is aligned. However, the space group of the layered rock salt crystal and the pseudo-spinel crystal is R-3m, which is different from the space group Fm-3m (the space group of a general rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry) of the rock salt crystal, so the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt crystal and the pseudo-spinel crystal and the rock salt crystal. In this specification, when the orientation of the cubic close-packed structure formed by the anions is aligned in the layered rock salt crystal, the pseudo-spinel crystal, and the rock salt crystal, it may be said that the crystal orientation is approximately the same.

[0345] The pseudospinel crystal structure can be expressed as the coordinates of cobalt and oxygen in the unit cell Co(0,0,0.5), O(0,0,x), with 0.20≦x≦0.25.

[0346] In the positive electrode active material according to one embodiment of the present invention, the difference between the volume of a unit cell at a charge depth of 0 and the volume per unit cell of a pseudo-spinel crystal structure at a charge depth of 0.82 is preferably 2.5% or less, more preferably 2.2% or less.

[0347] In the pseudospinel crystal structure, diffraction peaks appear at 2θ=19.30±0.20° (19.10° to 19.50°) and 2θ=45.55±0.10° (45.45° to 45.65°). More specifically, sharp diffraction peaks appear at 2θ=19.30±0.10° (19.20° to 19.40°) and 2θ=45.55±0.05° (45.50° to 45.60°).

[0348] In addition, the positive electrode active material according to one embodiment of the present invention has a pseudo-spinel crystal structure when charged at a high voltage, but not all of the particles may have a pseudo-spinel crystal structure. Other crystal structures may be included, or a part may be amorphous. However, when Rietveld analysis is performed on the XRD pattern, the pseudo-spinel crystal structure is preferably 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more. If the pseudo-spinel crystal structure is 50 wt% or more, more preferably 60 wt% or more, and even more preferably 66 wt% or more, the positive electrode active material can have sufficiently excellent cycle characteristics.

[0349] The number of atoms of element X is preferably 0.001 to 0.1 times the number of atoms of element M, more preferably greater than 0.01 and less than 0.04, and even more preferably about 0.02. The concentration of element X shown here may be a value obtained by performing elemental analysis of the entire particles of the positive electrode active material using, for example, ICP-MS or the like, or may be based on the value of the composition of raw materials in the process of producing the positive electrode active material.

[0350] When the element M contains cobalt and nickel, the ratio Ni / (Co+Ni) of the number of nickel atoms (Ni) to the sum of the numbers of cobalt and nickel atoms (Co+Ni) is preferably less than 0.1, and more preferably 0.075 or less.

[0351] The positive electrode active material according to one embodiment of the present invention is not limited to the above-mentioned materials.

[0352] For example, a composite oxide having a spinel-type crystal structure can be used as the positive electrode active material. For example, a polyanion-based material can be used as the positive electrode active material. For example, a material having an olivine-type crystal structure, a Nasicon-type material, etc. can be used as the polyanion-based material. For example, a material having sulfur can be used as the positive electrode active material.

[0353] As a material having a spinel type crystal structure, for example, a composite oxide represented by LiM2O4 can be used. It is preferable to have Mn as the element M. For example, LiMn2O4 can be used. Furthermore, 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.

[0354] An example of a polyanion-based material that can be used is a composite oxide having oxygen, an element X, a metal A, and a metal M. The metal M is one or more of Fe, Mn, Co, Ni, Ti, V, and Nb, the metal A is one or more of Li, Na, and Mg, and the element X is one or more of S, P, Mo, W, As, and Si.

[0355] 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), Ni(II))) can be used. Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, 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 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e PO4 (c + d + e is 1 or less, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (f + g + h + i is 1 or less, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1), etc., lithium compounds can be used.

[0356] In addition, composite materials such as the 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. Representative examples of the general formula Li (2-j) MSiO4 include 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) Fek Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k Mn l SiO4 (k + l is 1 or less, 0 < k < 1, 0 < l < 1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (m + n + q is 1 or less, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u Lithium compounds such as SiO4 (r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. can be used as materials.

[0357] 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.

[0358] 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, etc. can be used.

[0359] In addition, as the positive electrode active material, a borate-based material represented by the general formula LiMBO3 (M is Fe(II), Mn(II), or Co(II)) can be used.

[0360] Examples of materials containing sodium include NaFeO2 and 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, and other sodium-containing oxides can be used as positive electrode active materials.

[0361] In addition, lithium-containing metal sulfides such as Li2TiS3 and Li3NbS4 can be used as the positive electrode active material.

[0362] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0363] (Embodiment 7) In this embodiment, an example of a material and a structure that can be used for a secondary battery will be described.

[0364] A secondary battery according to an embodiment of the present invention has a positive electrode, a negative electrode, and an electrolyte. The secondary battery according to an embodiment of the present invention has, for example, an electrolytic solution containing the electrolyte, and a separator sandwiched between the positive electrode and the negative electrode. Alternatively, the secondary battery according to an embodiment of the present invention has, for example, a solid electrolyte sandwiched between the positive electrode and the negative electrode. It is preferable that the positive electrode, the negative electrode, and the electrolyte are enclosed in an exterior body.

[0365] [Positive electrode] The positive electrode has a positive electrode active material layer. The positive electrode active material layer has at least a positive electrode active material, and may contain other materials such as a coating on the active material surface, a conductive assistant, or a binder in addition to the positive electrode active material. The positive electrode may have a current collector, and the positive electrode active material layer may be formed on the current collector.

[0366] The conductive assistant may be a carbon material, a metal material, a conductive ceramic material, or the like. A fibrous material may also be used as the conductive assistant. The content of the conductive assistant relative to the total amount of the active material layer is preferably 1 wt% to 10 wt%, more preferably 1 wt% to 5 wt%.

[0367] As the conductive assistant, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fiber, etc. can be used. As the carbon fiber, for example, mesophase pitch carbon fiber, isotropic pitch carbon fiber, etc. can be used. As the carbon fiber, carbon nanofiber, carbon nanotube, etc. can be used. As the conductive assistant, for example, carbon materials such as carbon black (acetylene black (AB) etc.), graphite (graphite) particles, graphene, fullerene, etc. can be used. As the conductive assistant, for example, metal powder or metal fiber such as copper, nickel, aluminum, silver, gold, etc., conductive ceramic material, etc. can be used.

[0368] A graphene compound may be used as the conductive assistant. As the graphene compound, it is particularly preferable to use, for example, graphene, multi-graphene, or RGO. Here, RGO refers to a compound obtained by reducing, for example, graphene oxide (GO).

[0369] As the binder, it is preferable to use materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose.

[0370] As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer. As the binder, it is also preferable to use fluororubber. As the binder, it is also preferable to use a water-soluble polymer. As the water-soluble polymer, for example, polysaccharides can be used. As the polysaccharide, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, and starch can be used. It is even more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.

[0371] The binder may be used in combination of two or more of the above.

[0372] The current collector may be made of a highly conductive material such as a metal such as stainless steel, gold, platinum, aluminum, or titanium, or an alloy thereof. Alternatively, an aluminum alloy to which an element that improves heat resistance such as silicon, titanium, neodymium, scandium, or molybdenum is added may be used. Alternatively, the current collector may be made of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector may be in the form of a foil, plate (sheet), net, punched metal, or expanded metal. The current collector may be made of a material having a thickness of 5 μm or more and 30 μm or less.

[0373] [Negative electrode] The negative electrode has a negative electrode active material layer. The negative electrode active material layer may have a conductive assistant and a binder. The negative electrode may have a current collector, and the negative electrode active material layer may be formed on the current collector.

[0374] As the conductive assistant and binder that the negative electrode active material layer can have, the same materials as the conductive assistant and binder that the positive electrode active material layer can have can be used.

[0375] The negative electrode current collector may be made of a metal such as copper or titanium, or an alloy thereof. It is preferable that the negative electrode current collector is made of a material that does not form an alloy with carrier ions such as lithium.

[0376] <Negative electrode active material> As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0377] As the negative electrode active material, an element capable of carrying out a charge / discharge reaction by alloying / dealloying reaction with lithium can be used. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. Compounds containing these elements may also be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc.

[0378] In this specification, SiO refers to, for example, silicon monoxide. Alternatively, SiO x Here, x preferably has a value close to 1. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0379] Examples of the carbon-based material that can be used include graphite, easily graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0380] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, pitch-based artificial graphite, etc. Examples of natural graphite include flake graphite and spheroidized natural graphite, etc.

[0381] In addition, titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), and other oxides can be used.

[0382] In addition, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not form an alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as the negative electrode active material. Further examples of materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, and CoS 0.89 It also occurs in sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N and Ge3N4, phosphides such as NiP2, FeP2 and CoP3, and fluorides such as FeF3 and BiF3.

[0383] [Electrolyte] The electrolytic solution has a solvent and an electrolyte. The solvent of the electrolytic solution is preferably an aprotic organic solvent, and for example, one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in any combination and ratio.

[0384] In addition, by using one or more ionic liquids (room-temperature molten salts) that are flame-retardant and non-volatile as a solvent for the electrolyte, even if the internal temperature of the secondary battery rises due to an internal short circuit or overcharging, the secondary battery can be prevented from bursting or catching fire. The ionic liquid is composed of a cation and an anion, and includes an organic cation and an anion. Examples of the organic cation used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anion used in the electrolyte include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0385] Examples of the electrolyte to be dissolved in the above-mentioned solvent include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, and Li2B 10 Cl 10 , Li2B 12 Cl 12 Lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. can be used alone or in any combination and ratio of two or more of these.

[0386] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be, for example, 0.1 wt% to 5 wt% of the total solvent.

[0387] Also, a polymer gel electrolyte in which a polymer is swollen with an electrolytic solution may be used. By using a polymer gel electrolyte, safety against leakage and the like is improved. Also, it is possible to make the secondary battery thinner and lighter. As the polymer to be gelled, silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, fluorine-based polymer gel, and the like may be used. As the polymer, for example, a polymer having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing them may be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), may be used. Also, the formed polymer may have a porous shape.

[0388] Also, instead of the electrolyte, sulfide-based solid electrolytes, oxide-based solid electrolytes, halide-based solid electrolytes, etc. can be used. Or, solid electrolytes containing polymeric materials such as PEO (polyethylene oxide) can be used. When using a solid electrolyte, the installation of a separator or spacer becomes unnecessary. Also, since the entire battery can be solidified, there is no risk of leakage, and safety is dramatically improved.

[0389] Sulfide-based solid electrolytes include thiosilicon-based (Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S 30P2S5, 30Li2S 26B2S3 44LiI, 63Li2S 38SiS2 1Li3PO4, 57Li2S 38SiS2 5Li4SiO4, 50Li2S 50GeS2, etc.), sulfide crystallized glass (Li7P3S 11 , Li 3.25 P 0.95 Sulfide-based solid electrolytes have the advantages of being highly conductive, being able to be synthesized at low temperatures, and being relatively soft, making it easy to maintain conductive paths even after charging and discharging.

[0390] Oxide-based solid electrolytes include materials with a perovskite crystal structure (La 2 / 3-x Li 3x TiO3, etc.), materials with NASICON type crystal structure (Li 1-X Al X Ti 2-X (PO4)3, etc.), materials with garnet-type crystal structure (Li7La3Zr2O 12 etc.), materials with LISICON type crystal structure (Li 14 ZnGeO 16 etc.), LLZO(Li7La3Zr2O 12 ), oxide glass (Li3PO4-Li4SiO4, 50Li4SiO4·50Li3BO3, etc.), oxide glass ceramics (Li 1.07 Al 0.69 Ti 1.46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, etc. Oxide-based solid electrolytes have the advantage of being stable in the air.

[0391] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl, LiBr, LiI, etc. Composite materials in which these halide-based solid electrolytes are filled into the pores of porous alumina or porous silica can also be used as solid electrolytes.

[0392] Also, different solid electrolytes may be used in combination.

[0393] Among them, Li with NASICON type crystal structure 1+x Al x Ti 2-x(PO4)3(0 < x < 1) (hereinafter referred to as LATP) contains elements such as aluminum and titanium, which may be included in the positive electrode active material used in the secondary battery 300 according to one aspect of the present invention. Therefore, a synergistic effect can be expected for improving the cycle characteristics, which is preferable. In addition, an improvement in productivity due to the reduction of processes can also be expected. In this specification and the like, the NASICON-type crystal structure refers to a compound represented by M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.), which has a structure in which MO6 octahedra and XO4 tetrahedra share vertices and are three-dimensionally arranged.

[0394] [Separator] Also, the secondary battery preferably has a separator. As the separator, for example, those formed of paper, non-woven fabric, glass fiber, ceramics, or synthetic fibers using nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, polyurethane, etc. can be used. The separator is preferably processed into an envelope shape and arranged to wrap either the positive electrode or the negative electrode.

[0395] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

[0396] [Outer package] The exterior body of the secondary battery can be made of, for example, a metal material such as aluminum or a resin material. Also, a film-shaped exterior body can be used. As the film, for example, a three-layer structure film can be used in which a thin metal film having excellent flexibility such as aluminum, stainless steel, copper, nickel, etc. is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and an insulating synthetic resin film such as a polyamide-based resin or polyester-based resin is further provided on the thin metal film as the outer surface of the exterior body.

[0397] [Example of secondary battery configuration] As an example of the configuration of the secondary battery, the configuration of a secondary battery using a solid electrolyte layer will be described below.

[0398] In the secondary battery 700 shown in Fig. 26A, a combination of a positive electrode 710, a solid electrolyte layer 720, and a negative electrode 730 is laminated. By laminating a plurality of positive electrodes 710, solid electrolyte layers 720, and negative electrodes 730, the voltage of the secondary battery can be increased. Fig. 26A is a schematic diagram of a case where four combinations of a positive electrode 710, a solid electrolyte layer 720, and a negative electrode 730 are laminated.

[0399] The secondary battery 700 according to an embodiment of the present invention may be a thin-film all-solid-state battery. The thin-film all-solid-state battery can be produced by forming a positive electrode, a solid electrolyte, a negative electrode, a wiring electrode, and the like using a gas phase method (vacuum deposition method, pulsed laser deposition method, aerosol deposition method, sputtering method). For example, as shown in FIG. 26B, after forming a wiring electrode 741 and a wiring electrode 742 on a substrate 740, a positive electrode 710 is formed on the wiring electrode 741, a solid electrolyte layer 720 is formed on the positive electrode 710, and a negative electrode 730 is formed on the solid electrolyte layer 720 and the wiring electrode 742, thereby producing the secondary battery 700. As the substrate 740, a ceramic substrate, a glass substrate, a plastic substrate, a metal substrate, and the like can be used.

[0400] As the solid electrolyte contained in solid electrolyte layer 720, the above-mentioned solid electrolytes can be used.

[0401] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples.

[0402] (Embodiment 8) In this embodiment, electronic devices to which the semiconductor device according to one embodiment of the present invention can be applied will be described.

[0403] The semiconductor device according to one embodiment of the present invention can be mounted on various electronic devices. Examples of electronic devices include electronic devices with relatively large screens, such as television devices, desktop or notebook personal computers, computer monitors, digital signage, large game machines such as pachinko machines, digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, personal digital assistants, and audio playback devices. Mobile objects such as automobiles, motorcycles, ships, and aircraft can also be considered as electronic devices. The semiconductor device according to one embodiment of the present invention can be used as a charge / discharge control device for a battery built into these electronic devices.

[0404] The electronic device may have an antenna. By receiving a signal through the antenna, images, information, and the like can be displayed on the display unit. In addition, when the electronic device has an antenna and a secondary battery, the antenna may be used for contactless power transmission.

[0405] The electronic device may have sensors (including the ability to measure force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemicals, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared light), etc.

[0406] Electronic devices can have various functions, such as a function to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date, or time, a function to execute various software (programs), a wireless communication function, a function to read out programs or data recorded on a recording medium, and the like.

[0407] Examples of electronic devices including a semiconductor device according to one embodiment of the present invention will be described with reference to drawings.

[0408] 27A shows an example of a wristwatch type portable information terminal and an example of a power transmitting device. The portable information terminal 6100 includes a housing 6101, a display unit 6102, a band 6103, an operation button 6105, and the like. The power transmitting device 6200 includes a housing 6201, a power cable 6202, a power transmitting antenna 6203, a driver circuit 6204, and the like. The driver circuit 6204 may include a power transmitting control circuit, a matching circuit, a power radiation circuit, and the like. The portable information terminal 6100 also includes a secondary battery and a power receiving device therein. The power receiving device has a function of receiving power radiated from the power transmitting device 6200 and charging the secondary battery. The power receiving device may be, for example, the power receiving device exemplified in the above embodiment.

[0409] 27B, by stacking the portable information terminal 6100 and the power transmitting device 6200, power can be efficiently supplied to the portable information terminal 6100. The portable information terminal 6100 has a function of transmitting a signal to the power transmitting device 6200 to stop power emission when the built-in secondary battery becomes fully charged.

[0410] The mobile information terminal 6100 may be equipped with various communication means, such as short-range communication means such as Wi-Fi (registered trademark) and Bluetooth (registered trademark), as well as communication means compliant with third-generation mobile communication systems such as LTE, communication means compliant with fourth-generation mobile communication systems (4G), or communication means compliant with fifth-generation mobile communication systems (5G).

[0411] 28A shows an example of a mobile phone. A mobile phone 6300 includes a display unit 6302 incorporated in a housing 6301, operation buttons 6303, a speaker 6304, a microphone 6305, and the like.

[0412] The mobile phone 6300 also includes a fingerprint sensor 6310 in an area overlapping the display unit 6302. The fingerprint sensor 6310 may be an organic light sensor. An example of a fingerprint FP is shown in FIG. 28A. Since fingerprints are different for each individual, a fingerprint pattern can be acquired by the fingerprint sensor 6310 to perform personal authentication. Light emitted from the display unit 6302 can be used as a light source for acquiring the fingerprint pattern by the fingerprint sensor 6310.

[0413] The mobile phone 6300 includes a secondary battery and the power receiving device described in the above embodiment. The power receiving device has a function of receiving power emitted from the power transmitting device 6200 and charging the secondary battery.

[0414] 28B, by stacking the mobile phone 6300 and the power transmitting device 6200, power can be efficiently supplied to the mobile phone 6300. The mobile phone 6300 has a function of transmitting a signal to the power transmitting device 6200 to stop power emission when the built-in secondary battery becomes fully charged.

[0415] The mobile phone 6300 may be equipped with various communication means, such as short-range communication means such as Wi-Fi (registered trademark) and Bluetooth (registered trademark), as well as communication means compliant with third-generation mobile communication systems such as LTE, communication means compliant with fourth-generation mobile communication systems (4G), or communication means compliant with fifth-generation mobile communication systems (5G).

[0416] In addition, a light-emitting element or the like can be used for the display unit 6102 shown in FIG. 27A and the display unit 6302 shown in FIG. 28A. Examples of the light-emitting element include self-luminous light-emitting elements such as LEDs (Light Emitting Diodes), OLEDs (Organic LEDs), QLEDs (Quantum-dot LEDs), and semiconductor lasers. In addition, liquid crystal elements such as transmissive liquid crystal elements, reflective liquid crystal elements, and semi-transmissive liquid crystal elements can also be used as display elements used for the display unit 6102 and the display unit 6302. In addition, a shutter-type or optical interference-type MEMS (Micro Electro Mechanical Systems) element, a microcapsule type, an electrophoresis type, an electrowetting type, or an electronic liquid powder (registered trademark) type display element, or the like can also be used.

[0417] Note that in one embodiment of the present invention, it is particularly suitable to use an organic EL element for the display portion 6102 and the display portion 6302. By using an organic EL element, the display portion 6102 and the display portion 6302 can be provided over a flexible substrate. By using a flexible display portion in the portable information terminal 6100 and the mobile phone 6300, a portable information terminal and a mobile phone with reduced weight and reduced damage to the display portion can be provided.

[0418] The robot 7100 shown in FIG. 29 includes an illuminance sensor, a microphone, a camera, a speaker, a display, various sensors (infrared sensor, ultrasonic sensor, acceleration sensor, piezoelectric sensor, optical sensor, gyro sensor, etc.), and a movement mechanism.

[0419] The microphone has a function of detecting acoustic signals such as the user's voice and environmental sounds. The speaker has a function of emitting audio signals such as voice and warning sounds. The robot 7100 can analyze the audio signal input via the microphone and emit a necessary audio signal from the speaker. The robot 7100 can communicate with the user using the microphone and the speaker.

[0420] The camera has a function of capturing an image of the surroundings of the robot 7100. The robot 7100 also has a function of moving using a moving mechanism. The robot 7100 can capture an image of the surroundings using the camera and detect the presence or absence of an obstacle when moving by analyzing the image. By using a semiconductor device according to one embodiment of the present invention for a secondary battery (battery) of the robot 7100, overvoltage during a charging operation can be detected. Furthermore, the reliability and safety of the robot 7100 can be improved.

[0421] The flying object 7120 has propellers, a camera, a battery, etc., and has the ability to fly autonomously.

[0422] For example, image data captured by a camera is stored in the electronic component 7121. The electronic component 7122 can analyze the image data and detect the presence or absence of an obstacle when moving. The electronic component 7122 can estimate the remaining battery charge from a change in the charge capacity of the battery. By using the semiconductor device according to one embodiment of the present invention for the battery of the flying object 7120, overvoltage during a charging operation can be detected. Thus, the reliability and safety of the flying object 7120 can be improved.

[0423] The cleaning robot 7140 has a display arranged on the top surface, multiple cameras arranged on the sides, a brush, operation buttons, various sensors, etc. Although not shown, the cleaning robot 7140 is equipped with tires, a suction port, etc. The cleaning robot 7140 can move by itself, detect dirt, and suck up the dirt from the suction port arranged on the bottom surface.

[0424] For example, the cleaning robot 7140 can analyze an image captured by a camera and determine whether or not there is an obstacle such as a wall, furniture, or a step. When an object that may become entangled in the brush, such as a wire, is detected by image analysis, the rotation of the brush can be stopped. By using a semiconductor device according to one embodiment of the present invention for the battery of the cleaning robot 7140, overvoltage during charging can be detected. Thus, the reliability and safety of the cleaning robot 7140 can be improved.

[0425] An electric vehicle 7160 is shown as an example of a moving object. The electric vehicle 7160 includes an engine, tires, brakes, a steering device, a camera, and the like. By using a semiconductor device according to one embodiment of the present invention for a battery of the electric vehicle 7160, overvoltage during a charging operation can be detected. Thus, the reliability and safety of the electric vehicle 7160 can be improved.

[0426] Note that, although an electric vehicle has been described above as an example of a moving object, the moving object is not limited to an electric vehicle. For example, moving objects include trains, monorails, ships, and flying objects (helicopters, unmanned aerial vehicles (drones), airplanes, and rockets). By using a semiconductor device according to one embodiment of the present invention in the batteries of these moving objects, overvoltage during a charging operation can be detected. Therefore, the reliability and safety of these moving objects can be improved.

[0427] A battery including a semiconductor device of one embodiment of the present invention can be incorporated into a TV device 7200 (television receiver), a smartphone 7210, a PC 7220 (personal computer), a PC 7230, a game console 7240, a game console 7260, or the like.

[0428] The smartphone 7210 is an example of a portable information terminal. The smartphone 7210 includes a microphone, a camera, a speaker, various sensors, and a display unit.

[0429] A PC 7220 and a PC 7230 are examples of a notebook PC and a stationary PC, respectively. A keyboard 7232 and a monitor device 7233 can be connected to the PC 7230 wirelessly or via a wire. A game machine 7240 is an example of a portable game machine. A game machine 7260 is an example of a stationary game machine. A controller 7262 is connected to the game machine 7260 wirelessly or via a wire.

[0430] When an electronic device includes a semiconductor device according to one embodiment of the present invention, its power consumption can be reduced.

[0431] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes and examples. EXAMPLES

[0432] The circuit operation of the voltage detection circuit 100TA shown in Fig. 9 was verified using a circuit simulator. SmartSpice from SILVACO Corporation was used as the circuit simulator.

[0433] As the verification conditions, the channel length, channel width, and threshold voltage of the transistors M1 to M6 were set to 0.36 μm, 0.36 μm, and 0.83 V. The capacitance values ​​of the capacitors C1 and C2 were each set to 1 pF. The capacitance values ​​of the parasitic capacitances generated at the nodes ND1 to ND4 were set to 1 fF. The terminal 111 was supplied with a voltage of 0 V, the terminal 114 with a voltage of 1.5 V, and the terminal 115 with a voltage of 1 V.

[0434] Moreover, the comparator 101 outputs 0V when the voltage of the non-inverting input is equal to or lower than the voltage of the inverting input, and outputs 1V when the voltage of the non-inverting input exceeds the voltage of the inverting input.

[0435] The voltage changes at terminals G1 to G6, nodes ND1 to ND4, terminal 112, and terminal 113 when the voltage at terminal 112 changes from 3.5V to 4.5V were calculated using a circuit simulator. The calculation results are shown in Figures 30A to 30D and Figures 31A to 31C. Figure 31D shows the potential change at terminal 112 used in the calculation. The vertical axis of Figures 30A to 30D and Figures 31A to 31D indicates voltage, and the horizontal axis indicates time.

[0436] FIG. 30A shows the calculation results for terminals G1, G2, G4, and G5. FIG. 30B shows the calculation results for terminals G3 and G6. FIG. 30C shows the calculation results for node ND1. FIG. 30D shows the calculation results for node ND2. FIG. 31A shows the calculation results for node ND3. FIG. 31B shows the calculation results for node ND4. FIG. 31C shows the calculation results for terminal 113.

[0437] In this embodiment, from 0 seconds until 20 μs has elapsed, 10V is supplied to terminals G1, G2, G4, and G5, and 0V is supplied to terminals G3 and G6. During this period, transistors M1, M2, M4, and M5 are in the ON state, and transistors M3 and M6 are in the OFF state. Therefore, node ND1 is 0V, node ND2 is 1.5V, node ND3 is 0V, and node ND4 is 1.5V.

[0438] After 20 μsec has elapsed, 0 V is supplied to terminals G1, G2, G4, and G5, and 10 V is supplied to terminals G3 and G6. Therefore, after 20 μsec has elapsed, transistors M1, M2, M4, and M5 are turned off, and transistors M3 and M6 are turned on. In addition, the voltages of nodes ND1 to ND4 after 20 μsec have elapsed change according to the change in potential of terminal 112.

[0439] 31C and 31D show that the voltage at terminal 113 is 0 V when the voltage at terminal 112 is 4 V or less, and changes to 1 V when the voltage at terminal 112 exceeds 4 V. By using a circuit simulator, it was confirmed that the voltage detection circuit 100TA operates correctly. [Explanation of symbols]

[0440] 100: voltage detection circuit, 101: comparator, 111: terminal, 112: terminal, 113: terminal, 114: terminal, 115: terminal, 201: terminal, 202: terminal, 300: secondary battery

Claims

1. The semiconductor device and the secondary battery are included. the semiconductor device includes a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first capacitance element, a second capacitance element, and a comparator; one of a source and a drain of the first transistor is electrically connected to a first terminal; the other of the source and the drain of the first transistor is electrically connected to one of the source and the drain of the sixth transistor; one of a source and a drain of the second transistor is electrically connected to a second terminal; the other of the source and the drain of the second transistor is electrically connected to one of the source and the drain of the third transistor; the other of the source and the drain of the third transistor is electrically connected to a third terminal; one of a source and a drain of the fourth transistor is electrically connected to the first terminal; the other of the source and the drain of the fourth transistor is electrically connected to the non-inverting input of the comparator; one of a source and a drain of the fifth transistor is electrically connected to the second terminal; the other of the source and the drain of the fifth transistor is electrically connected to the other of the source and the drain of the sixth transistor; the first capacitance element is provided between the other of the source or the drain of the first transistor and the one of the source or the drain of the third transistor; the second capacitance element is provided between the other of the source or the drain of the fourth transistor and the other of the source or the drain of the fifth transistor; The inverting input of the comparator is electrically connected to a fourth terminal; the output of the comparator is electrically connected to a fifth terminal; a negative electrode of the secondary battery electrically connected to the first terminal; the positive electrode of the secondary battery is electrically connected to the third terminal; The battery pack, wherein each of the first to sixth transistors has a channel formed in an oxide semiconductor.

2. 2. The battery pack according to claim 1 , wherein the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor, the sixth transistor, the first capacitance element, the second capacitance element, and the comparator are provided on a flexible substrate.

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