Semiconductor relay and semiconductor device

Abstract

Provided is a semiconductor relay having good electrical characteristics. The semiconductor relay has a first circuit and a second circuit. The first circuit has a first light-emitting element. The second circuit has a first light-reception element, a memory, and a first switch. The memory has a second switch. The second switch includes a second semiconductor layer. The first switch and the first light-emitting element are formed using a first semiconductor layer. The first semiconductor layer and the second semiconductor layer include gallium and the second semiconductor layer also includes oxygen. The lighting and extinguishing of the first light-emitting element is controlled by a first signal applied to the first circuit. First data generated by the first light-reception element converting light emitted from the first light-emitting element to voltage is applied to the memory. The first switch is controlled to be conductive or non-conductive by the first data stored in the memory.

Description

[Technical field]

[0001] One embodiment of the present invention relates to a semiconductor relay, a latching type semiconductor relay, and a semiconductor device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention disclosed in this specification and the like include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, an electronic device, a lighting device, an input device, and an input / output device.

[0003] In this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. A transistor, a semiconductor circuit, an arithmetic device, a memory device, and the like are examples of semiconductor devices. In addition, communication devices, imaging devices, electro-optical devices, power generation devices (including thin-film solar cells, organic thin-film solar cells, and the like), and electronic devices may include semiconductor devices. [Background technology]

[0004] The semiconductor relay has a first circuit and a second circuit. The second circuit has a first terminal and a second terminal. By applying a signal to the first circuit, a switch in the second circuit is controlled, and the conduction or non-conduction between the first terminal and the second terminal is controlled. Specifically, by applying a signal to the first circuit, the light-emitting element is turned on, and an electromotive force is generated in the light-receiving element in the second circuit. The electromotive force controls the switch, and the conduction or non-conduction of the switch is controlled. Therefore, a contactless semiconductor relay that transmits signals using a light-emitting element and a light-receiving element is more reliable than a reed relay having mechanical contacts.

[0005] One type of semiconductor relay is a latching type semiconductor relay. A latching type semiconductor relay requires power when changing the conductive or non-conductive state of the switch, but does not require power when maintaining the state. This makes it possible to reduce the power consumption of the semiconductor relay. The following Patent Document 1 describes a non-contact semiconductor relay with a latching function. Also, the latching function discloses a semiconductor relay that uses a memory using a transistor having a metal oxide in the semiconductor layer to store the state. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-126986 A Summary of the Invention [Problem to be solved by the invention]

[0007] Electronic devices tend to consume more power as the amount of calculation increases. Semiconductor relays are used to achieve power gating of functional modules or integrated circuits with the aim of reducing the power consumption of electronic devices. Compared to reed relays that have mechanical contacts, semiconductor relays have a problem in that the switch has a large resistance value, and the switch becomes a resistance component and consumes power. In particular, when the switch is used to control the conduction or non-conduction of wiring that supplies a power supply potential to a functional module or an integrated circuit, the resistance component of the switch becomes a factor of power loss.

[0008] Semiconductor relays used in electronic devices are required to reduce their mounting area and weight. In particular, when handling large amounts of power in mobile devices, robots, in-vehicle devices, and the like, there is a problem that it is difficult to use reed relays due to limitations on mounting area or weight. Therefore, semiconductor relays are required to be low-resistance switches that can supply large amounts of power, and to be compact and lightweight.

[0009] The semiconductor relay has a light-emitting element in a first circuit and a light-receiving element in a second circuit. The light-emitting element is formed in a process different from that of the light-receiving element. Therefore, the semiconductor relay has the first circuit having the light-emitting element and the second circuit having the light-receiving element housed in a single housing. In other words, since the first circuit and the second circuit are formed in different processes, lamination or molding is required, which increases the manufacturing cost.

[0010] An object of one embodiment of the present invention is to provide a semiconductor relay with a novel structure. Another object of one embodiment of the present invention is to provide a semiconductor relay with favorable electrical characteristics. Another object of one embodiment of the present invention is to provide a miniaturized semiconductor relay. Another object of one embodiment of the present invention is to provide a highly reliable semiconductor relay.

[0011] An object of one embodiment of the present invention is to provide a semiconductor device having a novel structure.An object of one embodiment of the present invention is to provide a semiconductor device with favorable electrical characteristics.An object of one embodiment of the present invention is to provide a miniaturized semiconductor device.An object of one embodiment of the present invention is to provide a highly reliable semiconductor device.

[0012] 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 necessarily solve all of these problems. Note that problems other than these can be extracted from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0013] One embodiment of the present invention is a semiconductor relay having a first circuit and a second circuit. The first circuit has a first light-emitting element. The second circuit has a first light-receiving element, a memory, and a first switch. The first switch and the first light-emitting element are formed using a first semiconductor layer. The first semiconductor layer contains gallium. The first light-emitting element is turned on or off by a first signal provided to the first circuit. Light emitted from the first light-emitting element by the first signal is provided to a first light-receiving element, and the first light-receiving element generates first data by converting the light into a voltage. The memory stores the first data, and the first switch is controlled to be conductive or non-conductive by the first data, in this semiconductor relay.

[0014] One embodiment of the present invention is a semiconductor relay having a first circuit and a second circuit. The first circuit has a first light-emitting element and a second light-emitting element. The second circuit has a first light-receiving element, a second light-receiving element, a memory, and a first switch. The first switch, the first light-emitting element, and the second light-emitting element are formed using a first semiconductor layer. The first semiconductor layer contains gallium. The first light-emitting element is turned on or off by a first signal provided to the first circuit. The second light-emitting element is turned on or off by a second signal provided to the first circuit. Light emitted from the first light-emitting element by the first signal is provided to the first light-receiving element, and the first light-receiving element generates first data by converting the light into a voltage. The first data is stored in the memory via the second switch, and the first switch is controlled to be conductive or non-conductive by the first data. The first switch is controlled to be conductive by the first data stored in the memory. The light emitted by the second light-emitting element by the second signal is provided to the second light-receiving element, which generates the second data by converting the light into a voltage. The first data stored in the memory is initialized by the second data. The first switch is a semiconductor relay that is controlled to be non-conductive by initializing the first data stored in the memory.

[0015] In the above, the memory has a second switch, a third switch, and a capacitance. The second switch and the third switch are formed above the first switch using a second semiconductor layer. The capacitance is formed above the second semiconductor layer. The memory stores first data in the capacitance by controlling the second switch, and the third switch is turned on by the second data. It is preferable that the first data stored in the capacitance is initialized by turning on the third switch.

[0016] In the above, it is preferable that the first semiconductor layer contains nitrogen and the second semiconductor layer contains oxygen.

[0017] In the above, it is preferable that the first semiconductor layer contains nitrogen or oxygen, and the second semiconductor layer contains indium, zinc, and oxygen.

[0018] In the above, it is preferable that a part of the first light receiving element is disposed at a position overlapping with the first light emitting element.

[0019] In the above, the semiconductor relay has a phosphor. The phosphor is disposed between the first light-emitting element and the first light-receiving element. The phosphor is preferably a semiconductor relay that converts the wavelength of light emitted by the first light-emitting element to a wavelength longer than that of the light emitted by the first light-emitting element.

[0020] In the above, the first light receiving element has an active layer, which is preferably a semiconductor relay having an organic compound.

[0021] One embodiment of the present invention is a semiconductor relay having a first circuit and a second circuit. The first circuit has a first light-emitting element, a second light-emitting element, a first terminal, a second terminal, and a third terminal. The second circuit has a first transistor, a second transistor, a third transistor, a first light-receiving element, a second light-receiving element, a capacitance, a fourth terminal, and a fifth terminal. The first terminal is electrically connected to one of the electrodes of the first light-emitting element, the third terminal is electrically connected to one of the electrodes of the second light-emitting element, the second terminal is electrically connected to the other of the electrodes of the first light-emitting element and the other of the electrodes of the second light-emitting element, and the gate of the first transistor is electrically connected to one of the source or drain of the second transistor, one of the source or drain of the third transistor, and one of the electrodes of the capacitance. The other of the source or drain of the second transistor is electrically connected to the gate of the second transistor and one of the electrodes of the first light-receiving element. The gate of the third transistor is electrically connected to one of the electrodes of the second light receiving element. The fourth terminal is electrically connected to one of the source or drain of the first transistor. The fifth terminal is electrically connected to the other of the source or drain of the first transistor, the other of the source or drain of the third transistor, the other of the electrode of the capacitance, the other of the electrode of the first light receiving element, and the other of the electrode of the second light receiving element. The light emitted by the first light emitting element is given to the first light receiving element, and the light emitted by the second light emitting element is given to the second light receiving element. The wiring electrically connecting the gate of the first transistor, one of the source or drain of the second transistor, and one of the source or drain of the third transistor is a semiconductor relay provided at a position that blocks light so that the light emitted by the first light emitting element is not incident on the second light receiving element, and is provided at a position that blocks light so that the light emitted by the second light emitting element is not incident on the first light receiving element.

[0022] In the above, one embodiment of the present invention is a semiconductor device including a semiconductor relay and a processor. The first circuit is provided with a first signal or a second signal by the processor. The first light-emitting element is turned on or off by the first signal provided to the first circuit. The second light-emitting element is turned on or off by the second signal provided to the first circuit. The light emitted by the first light-emitting element is provided to the first light-receiving element by the first signal. The first light-receiving element generates first data by converting the light into a voltage, and the first data is stored in the capacitance via the second transistor. The first transistor is controlled to be conductive by the first data stored in the capacitance. The light emitted by the second light-emitting element is provided to the second light-receiving element by the second signal. The second light-receiving element generates second data by converting the light into a voltage, and the first data stored in the capacitance is initialized by the third transistor being turned on by the second data. The first transistor is controlled to be non-conductive by initializing the first data stored in the capacitance. In the semiconductor device, a voltage range of the fourth terminal applied with respect to the fifth terminal is larger than a voltage range of the first signal applied by the processor. Effect of the Invention

[0023] According to one embodiment of the present invention, it is possible to provide a semiconductor relay having a novel structure. Alternatively, it is possible to provide a semiconductor relay having good electrical characteristics. Alternatively, it is possible to provide a miniaturized semiconductor relay. Alternatively, it is possible to provide a semiconductor relay having high reliability.

[0024] According to one embodiment of the present invention, a semiconductor device having a novel structure can be provided. According to one embodiment of the present invention, a semiconductor device having favorable electrical characteristics can be provided. Alternatively, a miniaturized semiconductor device can be provided. Alternatively, a semiconductor device having high reliability can be provided.

[0025] The effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not preclude the existence of other effects. The other effects are described below and are not mentioned in this section. The effects not mentioned in this section can be derived by a person skilled in the art from the description of the specification or drawings, etc., and can be appropriately extracted from these descriptions. One embodiment of the present invention has at least one of the effects listed above and / or other effects. Therefore, one embodiment of the present invention may not have the effects listed above in some cases. [Brief description of the drawings]

[0026] FIG. 1 is a block diagram illustrating a semiconductor relay. FIG. 2 is a circuit diagram illustrating a semiconductor relay. 3A and 3B are circuit diagrams illustrating a semiconductor relay. FIG. 4 is a circuit diagram illustrating a semiconductor relay. Fig. 5A is a cross-sectional view of a semiconductor relay, and Fig. 5B is a cross-sectional view of a light receiving element. 6A and 6B are cross-sectional views of a semiconductor relay. 7A and 7B are cross-sectional views of a semiconductor relay. Fig. 8A is a top view illustrating an example of the configuration of a transistor, and Fig. 8B and Fig. 8C are cross-sectional views illustrating an example of the configuration of a transistor. Fig. 9A is a diagram explaining the classification of IGZO crystal structures. Fig. 9B is a diagram explaining the XRD spectrum of silica glass. Fig. 9C is a diagram explaining the XRD spectrum of crystalline IGZO. Fig. 9D is a diagram explaining the ultrafine electron beam diffraction pattern of crystalline IGZO. FIG. 10 is a diagram illustrating an example of an electronic device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Furthermore, 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" and "wirings" are integrally formed. Furthermore, when describing a circuit, "wiring" may include a resistor.

[0031] In addition, in this specification and the like, the resistance of a "resistance" may be determined by the length of the wiring. Alternatively, the resistance may be formed by connecting a conductive layer having a resistivity different from that of the conductive layer used in the wiring via a contact. Alternatively, the resistance may be determined by doping an impurity into a semiconductor layer.

[0032] In addition, in this specification, a "terminal" in an electric circuit refers to a portion where a current or a charging voltage is input or output, and / or a signal is received or transmitted. Therefore, a part of a wiring or an electrode may function as a terminal.

[0033] 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.

[0034] 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.

[0035] In addition, in this specification, "electrically connected" includes a direct connection and a connection via "something having some electrical action". Here, "something having some electrical action" is not particularly limited as long as it allows the transmission and reception of electrical signals between the connection objects. Therefore, even when it is expressed as "electrically connected", in an actual circuit, there may be no physical connection and only wiring extending therethrough. Also, even when it is expressed as "directly connected", it includes a case where wiring formed by different conductive layers is formed as one wiring via a contact.

[0036] 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.

[0037] 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.

[0038] In addition, in this specification, when an etching process is performed after forming a resist mask, the resist mask is removed after the etching process is completed, unless otherwise specified.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] In this specification, the term "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 term "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").

[0044] 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.

[0045] In this specification and the like, high power supply potential VDD (hereinafter simply referred to as "VDD" or "H potential") refers to a power supply potential that is higher than the low power supply potential VSS. Also, low power supply potential VSS (hereinafter simply referred to as "VSS" or "L potential") refers to a power supply potential that is lower than the high power supply potential VDD. Also, the ground potential can 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.

[0046] 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.

[0047] 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.

[0048] 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 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.

[0049] (Embodiment 1) In this embodiment, a semiconductor relay according to one embodiment of the present invention will be described. First, a brief description of the relay will be given. There are contact relays having mechanical contacts (hereinafter, referred to as movable contacts) and contactless relays. Either type of relay has a first circuit and a second circuit. The second circuit has a first terminal, a second terminal, and a switch. The switch of the second circuit is controlled by a first signal given to the first circuit. The switch can control the conduction or non-conduction between the first terminal and the second terminal. Note that a transistor or a diode can be used as the switch. In addition, the switch can control a DC signal or an AC signal.

[0050] Next, a relay having a movable contact will be described in detail. As an example, a reed relay having a movable contact generates an electromagnetic force by giving a signal to an electromagnetic coil in a first circuit. The voltage generated by the electromagnetic force controls the conduction or non-conduction of a switch in a second circuit. Note that reed relays have an operational problem called chattering. Chattering is a phenomenon in which a mechanical vibration occurs when a movable contact comes into contact, causing the movable contact to rapidly repeat conduction or non-conduction. Therefore, chattering is considered to be one of the factors that cause malfunctions in electronic devices. In addition, when controlling the conduction or non-conduction of wiring that supplies a power supply potential using a reed relay, there is a problem that a timing design that takes into account the period during which chattering occurs or the addition of electronic components such as a low-pass filter is required.

[0051] A reed relay can control a large current, for example, 1 ampere or more, depending on the type or configuration of the electrodes of the movable contact. However, when a reed relay is used to handle a large amount of power, sparks may occur when the movable contacts make contact. Therefore, the movable contacts may have poor contact due to oxidation of the movable contact surface, or short circuits due to fusion between adjacent movable contacts. In addition, a reed relay requires components such as a movable contact or an electromagnetic coil, making it difficult to miniaturize the reed relay. Therefore, when a reed relay is used, it is difficult to miniaturize electronic devices such as mobile devices, robots, and in-vehicle devices.

[0052] In particular, electronic devices such as robots and in-vehicle devices require the control of larger voltages or currents. For example, power semiconductors are known as elements that can control large voltages or currents. Representative power semiconductors include IGBTs (Insulated Gate Bipolar Transistors) and IEGTs (Injection Enhanced Gate Transistors).

[0053] Next, a semiconductor relay according to one embodiment of the present invention will be described. The semiconductor relay uses a first light-emitting element and a first light-receiving element instead of an electromagnetic coil to control the conduction or non-conduction of a switch. The first light-emitting element can be an electroluminescence element such as a light-emitting diode (LED) or an organic light-emitting diode (OLED). The first light-receiving element can be an organic light sensor, a photodiode, or a phototransistor. Therefore, the semiconductor relay can be called a non-contact relay. For example, the semiconductor relay can be a photoMOS relay using a metal-oxide-semiconductor field-effect transistor (MOSFET). Note that this embodiment shows an example in which an organic light sensor is used as the first light-receiving element. By using the organic light sensor, the process temperature for forming the first light-receiving element can be lowered. In addition, when a photodiode is used as the first light-receiving sensor, the wavelength range of light that the first light-receiving element can detect can be set to a wide range from visible light wavelengths to infrared wavelengths.

[0054] Further, the semiconductor relay will be described in detail. The semiconductor relay has a first light-emitting element in a first circuit, and a first light-receiving element, a switch, a memory, a first terminal, and a second terminal in a second circuit. The first light-emitting element is turned on or off by a first signal provided to the first circuit. The light emitted by the first light-emitting element is provided to the first light-receiving element by the first signal, and the first light-receiving element generates first data by converting the light into a voltage. The first data is stored in the memory, and the first switch controls the conduction or non-conduction between the first terminal and the second terminal by the first data. Note that the switch can be called the first switch in other words to distinguish it from the second switch or the third switch that will appear in the following description.

[0055] Compared to reed relays having mechanical contacts, the semiconductor relay uses a semiconductor element such as a transistor for the first switch, so the influence of the resistance component (for example, the conductance component of the transistor) is large. In other words, the first switch may be a factor of power loss in the semiconductor relay. Therefore, when performing power gating control on a functional module or an integrated circuit, a first switch with low loss like a power semiconductor is required when the semiconductor relay is conductive. In addition, by using a transistor for the first switch, the semiconductor relay does not require any measures against chattering. Therefore, the semiconductor relay can be operated at a higher speed than the reed relay. In addition, the semiconductor relay is suitable for miniaturization because it does not use a moving contact. In addition, the semiconductor relay is highly reliable because it does not suffer from oxidation or fusion of the moving contact that occurs in a reed relay.

[0056] Recent electronic devices are consuming more power as the amount of calculations in functional modules or integrated circuits increases due to the hardware implementation of AI (Artificial Intelligence). Functional modules or integrated circuits for robots and the like require a large amount of power to control motors. Therefore, when controlling power gating with a functional module or integrated circuit, it is required to be compact. In addition, a first switch capable of handling a large amount of power like a power semiconductor is required while the semiconductor relay is conducting. In addition, it is required that the semiconductor relay operates without continuously supplying a first signal to the first circuit while it is not conducting.

[0057] In one embodiment of the present invention, the second circuit has a memory. The memory has a second switch and a capacitance. The first data detected by the first light receiving element is stored in the memory via the second switch. Thus, the conduction or non-conduction of the first switch is controlled by the first data stored in the memory.

[0058] In the above-mentioned semiconductor relay, the first circuit further has a second light-emitting element, the second circuit further has a second light-receiving element, and the memory of the second circuit further has a third switch. In the following, for ease of explanation, the first light-emitting element and the second light-emitting element may be called light-emitting elements without ordinal numbers. The first light-receiving element and the second light-receiving element may be called light-receiving elements without ordinal numbers.

[0059] Next, the operation of the semiconductor relay having the above-mentioned configuration will be described. A first signal given to the first circuit controls turning on or off the first light-emitting element. A second signal given to the first circuit controls turning on or off the second light-emitting element. The memory stores first data detected by the first light-receiving element. The first switch is controlled to be conductive by the first data stored in the memory. The first data stored in the memory is initialized by the second data converted into a voltage by the second light-receiving element. The first switch is controlled to be non-conductive by the memory being initialized.

[0060] That is, the semiconductor relay can control the conduction or non-conduction of the first switch by the first signal or the second signal provided to the first circuit. In other words, the first signal or the second signal can switch the conduction or non-conduction of the first switch at any time. Compared to the case where the first signal and the second signal are provided complementarily, the first switch can be switched between conduction and non-conduction at high speed by controlling the first signal so that it partially overlaps with the second signal.

[0061] Next, the first to third switches will be described in detail. Hereinafter, the first to third switches will be referred to as first to third transistors.

[0062] It is preferable that the first transistor is capable of handling a large voltage or a large current. For example, an IGBT, a MESFET, or the like can be used as the first transistor. However, when an IGBT is used as the first transistor, the source terminal corresponds to the emitter terminal, and the drain terminal corresponds to the collector terminal. Also, as the first transistor, a transistor containing a compound semiconductor or an oxide semiconductor in a semiconductor layer in addition to silicon or germanium may be used. In the case of a semiconductor relay that controls a large power, a transistor using a compound semiconductor or an oxide semiconductor has high voltage resistance and can pass a large current, and is therefore suitable for use as the first transistor.

[0063] In one embodiment of the present invention, the first transistor has a first semiconductor layer. For example, the first semiconductor layer can be a compound semiconductor containing gallium nitride (GaN) or silicon nitride (SiC), which is a semiconductor material having a wider band gap than a silicon semiconductor and a lower intrinsic carrier density than silicon, or an oxide semiconductor containing gallium oxide.

[0064] As an example, GaN, which is one of the compound semiconductors, can be produced by epitaxially growing single crystal GaN on a sapphire substrate by providing a low-temperature buffer layer on the sapphire substrate. Note that instead of the sapphire substrate, an SOI (Silicon on Insulator) substrate or a silicon substrate may be used.

[0065] In addition, the compound semiconductor using a nitride may be selected from silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, zinc nitride, magnesium nitride, gallium nitride, tantalum nitride, niobium nitride, bismuth nitride, yttrium nitride, iridium nitride, indium nitride, tin nitride, nickel nitride, hafnium nitride, and the like.

[0066] An oxide semiconductor can be manufactured by a chemical vapor deposition method, a sputtering method, or a wet method, and has an advantage of being highly suitable for mass production. In addition, an oxide semiconductor can be formed into a film even at room temperature, and therefore can be formed on a glass substrate or on an integrated circuit using silicon. In addition, the oxide semiconductor can be adapted to a larger substrate. Thus, among the wide-gap semiconductors described above, an oxide semiconductor has an advantage of being particularly suitable for mass production. In addition, even when a crystalline oxide semiconductor is to be obtained in order to improve the performance (e.g., field-effect mobility) of a transistor, the crystalline oxide semiconductor can be easily obtained by heat treatment at 250° C. to 800° C.

[0067] Note that the oxide semiconductor may be selected from silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, zinc oxide, magnesium oxide, gallium oxide, tantalum oxide, niobium oxide, bismuth oxide, yttrium oxide, iridium oxide, indium oxide, tin oxide, nickel oxide, hafnium oxide, ITO (indium tin oxide), IZO (indium zinc oxide (registered trademark)), aluminum-added zinc oxide, gallium-added zinc oxide, and the like.

[0068] The oxide semiconductor or compound semiconductor may further contain one or more elements selected from aluminum, yttrium, copper, vanadium, cadmium, beryllium, boron, arsenic, phosphorus, silicon, titanium, iron, nickel, zinc, tin, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like.

[0069] Next, the second or third transistor will be described. The second or third transistor is preferably a transistor with a small off-state current. The second or third transistor has a second semiconductor layer. By using a transistor with a small off-state current as the second or third transistor, the first data can be held during a period in which a functional module or an integrated circuit is power-gated. Therefore, power required to keep the first light-emitting element turned on or off can be reduced. For example, when the semiconductor layer of the first transistor is an oxide semiconductor and the semiconductor layer of the second or third transistor is an oxide semiconductor, the second semiconductor layer preferably has an oxide semiconductor different from that of the first semiconductor layer.

[0070] The oxide semiconductor used for the second semiconductor layer contains at least indium (In). In particular, it is preferable that it contains In and zinc (Zn). In addition to the above, it is preferable that it contains gallium (Ga) as a stabilizer for reducing variations in electrical characteristics of a transistor using the oxide semiconductor film. It is preferable that it contains tin (Sn) as a stabilizer. It is preferable that it contains hafnium (Hf) as a stabilizer. It is preferable that it contains aluminum (Al) as a stabilizer. It is preferable that it contains zirconium (Zr) as a stabilizer.

[0071] As another stabilizer, one or more of the lanthanides, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), may be included.

[0072] For example, In-Ga-Zn oxide means an oxide containing In, Ga, and Zn, and the ratio of In, Ga, and Zn does not matter. Metal elements other than In, Ga, and Zn may also be contained. In-Ga-Zn oxide has a sufficiently high resistance in the absence of an electric field, making it possible to sufficiently reduce the off-current, and also has high mobility.

[0073] A transistor having an oxide semiconductor (or metal oxide) for a second semiconductor layer is called an OS transistor.

[0074] In addition, because the energy gap of the semiconductor layer is large, OS transistors can exhibit extremely low off-current characteristics of several yA / μm (current value per 1 μm of channel width). OS transistors also have characteristics different from Si transistors, such as the absence of impact ionization, avalanche breakdown, and short channel effects, and can form highly reliable circuits. In addition, OS transistors are less susceptible to variations in electrical characteristics caused by non-uniformity in crystallinity, which is a problem in Si transistors.

[0075] When the oxide semiconductor constituting the second semiconductor layer is an In-M-Zn oxide, the atomic ratio of the metal elements of the sputtering target used to form the In-M-Zn oxide preferably satisfies In≧M and Zn≧M. As the atomic ratio of the metal elements of such a sputtering target, In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=3:1:2, In:M:Zn=4:2:3, In:M:Zn=4:2:4.1, In:M:Zn=5:1:3, In:M:Zn=5:1:6, In:M:Zn=5:1:7, In:M:Zn=5:1:8, In:M:Zn=10:1:3, etc. are preferable. In addition, when the oxide semiconductor constituting the semiconductor layer is an In-Zn oxide, the atomic ratio of the metal elements of the sputtering target used to form the In-Zn oxide preferably satisfies In≧Zn. The atomic ratio of the metal elements in such a sputtering target is preferably In:Zn=1:1, In:Zn=2:1, In:Zn=5:1, In:Zn=5:3, In:Zn=10:1, In:Zn=10:3, etc.

[0076] The semiconductor layer is made of an oxide semiconductor with a low carrier concentration. For example, the semiconductor layer has a carrier concentration of 1×10 17 / cm 3 Less than or equal to 1×10 15 / cm 3 Less than 1×10, more preferably 13 / cm 3 Less than or equal to 1×10 11 / cm 3 Less than 1×10, more preferably 10 / cm 3 Less than 1 x 10 -9 / cm 3 An oxide semiconductor having a carrier concentration of 1000 or more can be used. Such an oxide semiconductor is called a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor. The oxide semiconductor has a low density of defect states and stable characteristics.

[0077] Note that the present invention is not limited to these, and an appropriate composition may be used depending on the required semiconductor characteristics and electrical characteristics (field-effect mobility, threshold voltage, and the like) of a transistor. In order to obtain the required semiconductor characteristics of a transistor, it is preferable to appropriately set the carrier concentration, impurity concentration, defect density, atomic ratio of metal elements to oxygen, interatomic distance, density, and the like of the semiconductor layer. Note that an OS transistor will be described in detail in Embodiment 2.

[0078] The light-emitting element is preferably formed using the same first semiconductor layer as the first transistor. When the light-emitting element has the first semiconductor layer, the first circuit and the second circuit of the semiconductor relay can be formed on the same substrate.

[0079] The second or third transistor is preferably disposed above the first transistor. Furthermore, the first or second light receiving element is preferably formed above the second or third transistor. The first or second light receiving element has an active layer, and the active layer is preferably an organic compound. The active layer of the first or second light receiving element can detect light of any one of wavelengths in the wavelength range from the visible light region to the infrared region. The wavelength range of the light is preferably 400 nm to 780 nm, or more preferably 380 nm to 1400 nm. The wavelength range that the first or second light receiving element can detect can be limited to different wavelength ranges. The wavelength range can be selected depending on the phosphor, color filter, or material used for the active layer, which will be described later.

[0080] In addition, it is preferable that a part of the first light receiving element is arranged at a position overlapping the first light emitting element, and a part of the second light receiving element is arranged at a position overlapping the second light emitting element. Therefore, it is preferable that the channel formation region of the second transistor is shielded from the light emitted by the first light emitting element by the gate electrode or back gate electrode of the second transistor. In addition, it is preferable that the channel formation region of the third transistor is shielded from the light emitted by the second light emitting element by the gate electrode or back gate electrode of the third transistor. By shielding the channel formation region of the second or third transistor from the light emitted by the second or third light emitting element, it is possible to suppress the generation of leakage current due to the light incident on the second or third transistor.

[0081] Furthermore, the wiring electrically connecting the gate of the first transistor, one of the source or drain of the second transistor, and one of the source or drain of the third transistor may have a light-shielding function. For example, the first light-receiving element can be arranged so that the wiring blocks part or all of the light emitted by the second light-emitting element. Also, the second light-receiving element can be arranged so that the wiring blocks part or all of the light emitted by the first light-emitting element.

[0082] In addition, a part of the light emitted by the first light-emitting element may be incident on the second light-receiving element, so long as the electromotive force generated by the second light-receiving element is applied to the second transistor and no current flows between the source or drain of the second transistor. Also, a part of the light emitted by the second light-emitting element may be incident on the first light-receiving element, so long as the electromotive force generated by the first light-receiving element is applied to the first transistor and no current flows between the source or drain of the first transistor.

[0083] Furthermore, the semiconductor relay can have a phosphor. For example, an insulating layer containing a phosphor can be disposed between the light-emitting element and the light-receiving element. The phosphor can convert the wavelength of the light emitted by the light-emitting element to a longer wavelength than the light emitted by the light-emitting element. More specifically, when the wavelength range of the light emitted by the light-emitting element is shorter than the wavelength range that can be detected by the light-receiving element, the phosphor can convert the wavelength range of the light emitted by the light-emitting element to a wavelength range that can be detected by the light-receiving element (light in a wavelength range from the visible light region to the infrared region). The phosphor can convert the wavelength of the light emitted by the light-emitting element to a wavelength range that can be detected by the light-receiving element. Therefore, the selectivity and transferability of the first signal provided to the first circuit are improved, so that the first signal can be reliably transferred to the second circuit.

[0084] The semiconductor relay may have a color filter instead of the insulating layer containing a phosphor. When the wavelength range of the light emitted by the light-emitting element is wide, the color filter can transmit only light in the wavelength range that the light-receiving element can detect. Therefore, it is preferable to arrange the color filter between the light-emitting element and the light-receiving element. For example, by arranging the color filter, it is possible to limit the wavelength range of light incident on the channel formation regions of the first to third transistors. It is preferable that the provision of the color filter prevents leakage current from occurring in the first to third transistors due to light outside the wavelength range being incident on the channel formation regions of the first to third transistors.

[0085] Note that the channel formation regions of the first to third transistors are preferably shielded from light by a gate or a backgate of the second or third transistor, a wiring connecting the transistors, a phosphor, a color filter, or the like.

[0086] Next, the memory included in the second circuit will be described. The memory includes a second or third transistor and a capacitor. The capacitor uses a part of a wiring that electrically connects the gate of the first transistor, one of the source or drain of the second transistor, and one of the source or drain of the third transistor as one of the electrodes of the capacitor. Note that the other electrode of the capacitor can be a part of a wiring that is connected to one of the electrodes of the light receiving element.

[0087] As described above, a semiconductor relay having a novel configuration can be provided by forming the first circuit and the second circuit on the same substrate. In addition, light emitted by the light-emitting element can be blocked by using a gate or back gate of the transistor, a wiring connecting the transistors, a color filter, a phosphor, or the like. Therefore, a semiconductor relay in which the first signal is isolated from the second signal can be provided. In addition, a semiconductor relay having good electrical characteristics that can handle large power with low loss can be provided by using an oxide semiconductor or a compound semiconductor for the first transistor. In addition, a semiconductor relay having a configuration suitable for miniaturization can be provided by forming the first circuit and the second circuit on the same substrate and forming a light-receiving element that is arranged at a position overlapping with the light-emitting element. In addition, by having a light-emitting element and a light-receiving element, a highly reliable semiconductor relay can be provided by configuring the relay without a movable contact.

[0088] The formation area of ​​the light-emitting element includes the anode electrode and the cathode electrode. The formation area of ​​the light-receiving element is the larger of the anode electrode and the cathode electrode. Therefore, when the light-emitting element overlaps with the light-receiving element, it means that a part of the formation area of ​​the light-emitting element overlaps with a part of the formation area of ​​the light-receiving element.

[0089] Next, a semiconductor relay according to one embodiment of the present invention will be described in detail with reference to the drawings.

[0090] 1 is a block diagram illustrating a semiconductor relay. The semiconductor relay 100 has a circuit 101, a circuit 102, a terminal 11, a terminal 12, a terminal 14, and a terminal 15. The circuit 101 has a lighting circuit 110. The lighting circuit 110 has a light-emitting element. The circuit 102 has a detection circuit 120, a memory 130, and a switch circuit 140.

[0091] The terminal 11 is electrically connected to one of the terminals of the lighting circuit 110. The terminal 12 is electrically connected to the other of the terminals of the lighting circuit 110. The detection circuit 120 is electrically connected to the memory 130. The memory 130 is electrically connected to the switch circuit 140. One of the terminals of the switch circuit 140 is electrically connected to the terminal 14. The other terminal of the switch circuit 140 is electrically connected to the terminal 15.

[0092] When a first signal is applied to the terminal 11, the lighting circuit 110 is controlled to be turned on or off. As an example, when a voltage of "H" of the first signal is applied to the terminal 11 and a voltage of "L" of the first signal is applied to the terminal 12, a positive voltage is applied to the terminal 11 with the terminal 12 as a reference. When a positive voltage is applied to the terminal 11 with the terminal 12 as a reference, the light-emitting element is turned on. The light 150 emitted by the lighting circuit 110 is detected by the detection circuit 120. The memory 130 stores the first data detected by the detection circuit 120. Therefore, the switch circuit 140 is controlled to be conductive or non-conductive by the first data stored in the memory 130. Therefore, it can be said that the lighting circuit 110 and the detection circuit 120 correspond to a photocoupler, which is one of the transmission circuits.

[0093] Fig. 2 is a circuit diagram for explaining in detail the semiconductor relay 100 described in Fig. 1. The lighting circuit 110 has a light-emitting element 111 and a light-emitting element 112. The detection circuit 120 has a light-receiving element 121 and a light-receiving element 122, the memory 130 has a second switch, a third switch, and a capacitor 133, and the switch circuit 140 has a first switch. In the following description, the first switch will be referred to as a transistor 141a, the second switch as a transistor 131, and the third switch as a transistor 132.

[0094] The terminal 11 is electrically connected to one of the electrodes of the light-emitting element 111, and the terminal 12 is electrically connected to the other of the electrodes of the light-emitting element 111. In addition, the terminal 12 is electrically connected to one of the electrodes of the light-emitting element 112, and the terminal 11 is electrically connected to the other of the electrodes of the light-emitting element 112.

[0095] A gate of the transistor 141a is electrically connected to one of the source or drain of the transistor 131, one of the source or drain of the transistor 132, and one of the electrodes of the capacitor 133. The other of the source or drain of the transistor 132 is electrically connected to the gate of the transistor 132 and one of the electrodes of the light receiving element 121. The gate of the transistor 132 is electrically connected to one of the electrodes of the light receiving element 122. A terminal 14 is electrically connected to one of the source or drain of the transistor 141a. A terminal 15 is electrically connected to the other of the source or drain of the transistor 141a, the other of the source or drain of the transistor 132, the other electrode of the capacitor 133, the other electrode of the light receiving element 121, and the other electrode of the light receiving element 122.

[0096] Light 150a emitted by the light-emitting element 111 is provided to the light-receiving element 121, and light 150b emitted by the light-emitting element 112 is provided to the light-receiving element 122. Wirings electrically connecting the gate of the transistor 141a, one of the source or drain of the transistor 131, and one of the source or drain of the transistor 132 are provided at positions for blocking light so that the light 150a emitted by the light-emitting element 111 is not incident on the light-receiving element 122, and are provided at positions for blocking light so that the light 150b emitted by the light-emitting element 112 is not incident on the light-receiving element 121.

[0097] It is preferable that a signal that is complementary to the first signal applied to terminal 11 is applied to terminal 12. As an example, while a voltage of "H" is applied to terminal 11, a voltage of "L" is applied to terminal 12. Also, while a voltage of "L" is applied to terminal 11, a voltage of "H" is applied to terminal 12. In other words, an inverted signal of the signal applied to terminal 12 is applied to terminal 11.

[0098] Therefore, during a period when a voltage of "H" is applied to one of the electrodes of light-emitting element 111 and a voltage of "L" is applied to the other electrode of light-emitting element 111, light-emitting element 111 emits light. Specifically, by applying a signal that is complementary to a signal applied to terminal 12 to terminal 11, during a period when light-emitting element 111 is on, light-emitting element 112 is turned off, and during a period when light-emitting element 112 is on, light-emitting element 111 is turned off. Therefore, the conduction or non-conduction of the semiconductor relay can be controlled by a single signal.

[0099] The light receiving element 121 detects light emitted by the light emitting element 111. The light receiving element 121 generates an electromotive force across both ends of the light receiving element 121 by detecting the light. When the electromotive force becomes larger than a threshold voltage of the transistor 131, first data is stored in the capacitance 133 via the transistor 131. That is, the capacitance 133 stores a voltage of "H" which is the first signal applied to the terminal 11. The voltage of "H" stored in the capacitance 133 can make the transistor 141a conductive. Note that the transistor 141a being conductive can be rephrased as the semiconductor relay 100 being conductive.

[0100] The signal stored in the capacitor 133 is initialized when the transistor 132 is turned on by a voltage of "H" applied to the terminal 12. That is, the signal stored in the capacitor 133 can be initialized by the transistor 132 to make the transistor 141a non-conductive. In other words, the transistor 141a becoming non-conductive means that the semiconductor relay 100 becomes non-conductive.

[0101] 2, the gate of the transistor 131 and the other of the source or drain of the transistor 131 are electrically connected to form a diode connection. By forming the diode connection of the transistor 131, even if a small electromotive force is generated in the light receiving element 121 by the reflected light or stray light of the light emitting element 112, the transistor 131 does not turn on and does not affect the signal stored in the capacitor 133. In other words, the diode-connected transistor 131 functions as a switch.

[0102] Furthermore, even if a small electromotive force is generated in the light receiving element 122 due to reflected light or stray light from the light emitting element 111, the transistor 132 does not turn on, and the signal stored in the capacitor 133 is not initialized.

[0103] The transistor 131 or the transistor 132 can each have a backgate. The backgate of the transistor 131 has an effect of suppressing fluctuations in the electrical characteristics of the transistor 131, and the backgate of the transistor 132 has an effect of suppressing fluctuations in the electrical characteristics of the transistor 132.

[0104] Although the details will be described with reference to FIG. 5A, the back gate of the transistor 131 can shield the channel forming portion of the transistor 131 by reflecting the light emitted by the light emitting element 111 or the light emitting element 112. The back gate of the transistor 132 can shield the channel forming portion of the transistor 132 by reflecting the light emitted by the light emitting element 112 or the light emitting element 111. Note that the light shielding preferably means completely blocking the light emitted by the light emitting element 111 or the light emitting element 112. However, the light to be shielded also includes light that has been reduced in intensity, area, and the like of the light emitted by the light emitting element 111 or the light emitting element 112. For example, the light emitted by the light emitting element 111 may be attenuated by an insulating film provided between the light emitting element 111 and the light receiving element 121. As another example, the insulating film may absorb light.

[0105] The semiconductor relay 100 has a period during which the light-emitting element 111 or the light-emitting element 112 transitions from a lit state to an unlit state, or transitions from an unlit state to a lit state. In other words, the response time of the light-emitting element, the response time of the light-receiving element, or the acquisition time caused by the charging and discharging time of the capacitance 133 affects the switching speed of the semiconductor relay 100.

[0106] Fig. 3A is a circuit diagram illustrating the semiconductor relay 100 that improves the switching speed of the semiconductor relay 100. Fig. 3A differs from Fig. 2 in that it has a lighting circuit 110A. The lighting circuit 110A has a light-emitting element 111 and a light-emitting element 112, and the lighting circuit 110A is electrically connected to terminals 11 to 13. The terminal 11 is electrically connected to one of the electrodes of the light-emitting element 111. The terminal 13 is electrically connected to one of the electrodes of the light-emitting element 112. The terminal 12 is electrically connected to the other of the electrodes of the light-emitting element 111 and the other of the electrodes of the light-emitting element 112.

[0107] A first signal is applied to terminal 11, and a second signal is applied to terminal 13. It is preferable that a voltage of "L" or a third signal is applied to terminal 12. As an example, during a period when a voltage of "H" is applied to terminal 11, it is preferable that a voltage of "L" is applied to terminal 13. Also, during a period when a voltage of "H" is applied to terminal 13, it is preferable that a voltage of "L" is applied to terminal 11. A voltage of "H" is applied to capacitance 133 by the first data, and capacitance 133 is initialized by the second data.

[0108] It should be noted that even when a voltage of "H" is applied to the terminal 11, a voltage of "H" can be applied to the terminal 13. In other words, even during a period in which the transistor 141a is in an ON state based on the first data converted into a voltage by the light receiving element 121, the capacitance 133 can be initialized based on the second data converted into a voltage by the light receiving element 122, and the transistor 141a can be in an OFF state. Therefore, the semiconductor relay 100 can provide a high switching speed based on the first signal and the second signal.

[0109] When a voltage of "L" is applied to the first signal and the second signal, the semiconductor relay 100 can maintain the conductive or non-conductive state of the transistor 141a according to the voltage of the first data stored in the capacitor 133. Furthermore, when the transistor 131 or the transistor 132 is an OS transistor, the conductive or non-conductive state of the transistor 141a can be maintained for a long period of time. Therefore, the configuration of FIG. 3A is suitable for power gating because of the excellent switching speed of the semiconductor relay 100 and the ability to maintain the state for a long period of time.

[0110] Fig. 3B is a circuit diagram for explaining Fig. 3A in detail. As an example, in Fig. 3B, the light receiving element 121A of the detection circuit 120 includes a light receiving element 121A, and the light receiving element 122A includes a light receiving element 122A.

[0111] First, the light receiving element 121A will be described. The light receiving element 121A has a plurality of light receiving elements 121B, and the light receiving elements 121B are connected in series. In FIG. 3B, as an example, the light receiving element 121A has three light receiving elements 121B having the same electrical characteristics connected in series. Since the light receiving elements 121B have the same electrical characteristics, the electromotive force generated by the light receiving element 121A is three times as large as the threshold voltage of the light receiving element 121B. It is preferable that the electromotive force generated by the light receiving element 121A is a voltage sufficient to turn on the transistor 141a. In other words, it is preferable that the electromotive force generated by the light receiving element 121A is larger than the threshold voltage of the transistor 141a. It is preferable that the number of light receiving elements 121B connected in series is not limited.

[0112] It is preferable that the electromotive force generated by the light receiving element 122A is a voltage sufficient to turn on the transistor 132. As an example, in FIG. 3B, the light receiving element 122A has one light receiving element 122B. In other words, the light receiving element 122B can control the time for initializing the first data held in the capacitance 133.

[0113] Although not shown in FIG. 3B, as an example, the light receiving element 122A may be connected in parallel to two light receiving elements 122B having the same electrical characteristics. Compared to the case where there is one light receiving element 122B, the charge can be discharged from the capacitance 133 at twice the speed. In other words, the time it takes for the semiconductor relay 100 to transition from the ON state to the OFF state is shortened according to the number of light receiving elements 122B connected in parallel. In other words, the switching characteristics of the semiconductor relay 100 are improved according to the number of light receiving elements 122B.

[0114] In addition, the light receiving element 121A may be connected to a plurality of light receiving elements 121B in series or in parallel. In addition, the light receiving element 122A may be connected to a plurality of light receiving elements 122B in series or in parallel. The number of light receiving elements to be connected can be selected according to the switching characteristics of the semiconductor relay 100.

[0115] Fig. 4 is a circuit diagram illustrating a semiconductor relay 100 different from that in Fig. 3A. Fig. 4 is different in that it includes a switch circuit 140A. The switch circuit 140A includes a transistor 141a, a transistor 141b, and a diode 144. The switch circuit 140A is electrically connected to terminals 14 to 16.

[0116] Note that the description of the switch circuit 140 may be referred to for parts that overlap with those of the switch circuit 140, and therefore the description will be omitted. Here, differences between the switch circuit 140A and the switch circuit 140 will be described. The gate of the transistor 141b is electrically connected to the gate of the transistor 141a. One of the source and the drain of the transistor 141b is electrically connected to the terminal 16. The other of the source and the drain of the transistor 141b is electrically connected to the terminal 15.

[0117] One of the source and drain of the transistor 141a is electrically connected to the gate of the transistor 131 via a diode 144. The cathode terminal of the diode 144 is electrically connected to the terminal 14. The diode 144 can be configured of a transistor. The highest voltage among the voltages applied to the semiconductor relay 100 is applied to the terminal 14. Therefore, the diode 144 functions as a protection diode for the semiconductor relay 100. As an example, when the terminal 14 and the terminal 16 of the semiconductor relay 100 are electrically connected outside the semiconductor relay 100, the diode 144 also functions as a protection diode for the terminal 16.

[0118] Therefore, the voltage width of the terminal 4 given based on the terminal 15 is larger than the voltage width of the first signal given to the first circuit. That is, the operating voltage width of the circuit connected to the second circuit can be larger than the operating voltage of the circuit connected to the first circuit. Or, the operating voltage width of the circuit connected to the second circuit can be different from the operating voltage of the circuit to which the first circuit is connected. For example, the power supply voltage of the second circuit is smaller than the power supply voltage of the first circuit, but the transistor 141a of the second circuit passes a large current. That is, the semiconductor relay 100 has a function as a transmission circuit of signals that operate with different power supply voltages.

[0119] When the terminal 14 is connected to the terminal 16, the transistor 141b is connected in parallel to the transistor 141a. Therefore, when the transistor 141a has the same electrical characteristics as the transistor 141b, the resistance component between the terminal 14 and the terminal 16 is halved, so that the amount of current that the semiconductor relay 100 can handle is doubled. This is therefore preferable because the power that the semiconductor relay 100 can handle is doubled. In addition, the transistors 141a and 141b have the same gate capacitance. Therefore, the memory 130 that uses the capacitance 133 and the gate capacitance as a composite capacitance can hold the first data for a longer period of time. In addition, when the transistors are used as switches, the power loss caused by the transistors can be reduced.

[0120] 5 to 7 are diagrams illustrating a part of the cross-sectional structure of the semiconductor relay 100. Fig. 5A illustrates the light-emitting element 111, the light-emitting element 112, the light-receiving element 121, the light-receiving element 122, the transistor 141a, the transistor 131, the transistor 132, and the capacitor 133 in the semiconductor relay 100 described in Fig. 3A.

[0121] As an example, the transistor 141a, the light emitting element 111, and the light emitting element 112 are formed using a semiconductor layer formed on a silicon substrate, a sapphire substrate, or an SOI substrate. The semiconductor layer preferably has a crystal structure containing gallium. Examples of semiconductor layers containing gallium include gallium nitride (hereinafter, GaN) and gallium oxide (GaOx). As a different example, silicon nitride (SiC) may be used for the semiconductor layers.

[0122] Fig. 5A illustrates a semiconductor relay 100 using GaN for the semiconductor layer 212. For example, GaN can be produced by providing a low-temperature buffer layer on the substrate 210 and epitaxially growing single crystal GaN on the low-temperature buffer layer on the substrate 210. In Fig. 5A, the buffer layer is omitted. Fig. 5A also illustrates an example in which a sapphire substrate is used for the substrate 210.

[0123] When forming the transistor 141a, it is preferable to use a semiconductor layer in which the semiconductor layer 214 is epitaxially grown on the semiconductor layer 212. The semiconductor layer 212 is preferably GaN, and the semiconductor layer 214 is preferably AlGaN. For example, aluminum nitride (AlN) is known to have extremely excellent material properties, such as a band gap (6.2 eV) approximately twice that of GaN, an electrostatic breakdown field (12 MV / cm) approximately four times that of GaN, and a thermal conductivity (2.9 W / cmK) approximately 1.5 times that of GaN. Therefore, AlN and AlGaN, which is a mixed crystal of AlN and GaN, are preferable as high-output, high-frequency device materials. A HEMT (High Electron Mobility Transistor) having an AlGaN channel formation region can operate at a higher voltage than a HEMT having a GaN channel formation region. At the interface between GaN and AlGaN, a two-dimensional electron gas (2DEG) is generated due to the polarization effect of GaN and AlGaN. In other words, in a transistor having a HEMT structure, the 2DEG becomes the channel formation region.

[0124] Furthermore, the light emitting element 111 and the light emitting element 112 can be formed in the semiconductor layer 212 and the semiconductor layer 214. As an example, an n-type region 212a or a p-type region 212b is formed by adding a dopant to the semiconductor layer 214 and the semiconductor layer 212. The n-type region 212a comes into contact with the p-type region 212b to form a pn junction, thereby forming the light emitting element 111 or the light emitting element 112. Note that examples of the addition method include an ion doping method, an ion implantation method, and a plasma treatment method.

[0125] As an example, the n-type region 212a is formed by adding silicon (Si), germanium (Ge), or the like as a dopant. The p-type region 212b is formed by adding magnesium (Mg), zinc (Zn), cadmium (Cd), beryllium (Be), or the like as a dopant. The n-type region 212a or the p-type region 212b is preferably formed in a region continuous with the semiconductor layer 212 and the semiconductor layer 214. Alternatively, the n-type region 212a or the p-type region 212b may be formed only in the semiconductor layer 212. For example, when the n-type region 212a or the p-type region 212b is formed by using an ion doping method, the dopant may pass through the semiconductor layer 214 and be added to the semiconductor layer 212.

[0126] Conductive layers 216a to 216f are provided on the semiconductor layer 214. The conductive layer 216a corresponds to the cathode electrode of the light emitting element 111, and the conductive layer 216b corresponds to the anode electrode of the light emitting element 111. The n-type region 212a and the p-type region 212b formed between the conductive layer 216a and the conductive layer 216b form the light emitting element 111. The conductive layer 216e corresponds to the anode electrode of the light emitting element 112, and the conductive layer 216f corresponds to the cathode electrode of the light emitting element 112. The n-type region 212a and the p-type region 212b formed between the conductive layer 216e and the conductive layer 216f form the light emitting element 112. In the light emitting element 111 or the light emitting element 112, the position of the anode electrode or the cathode electrode can be arranged according to the n-type region or the p-type region.

[0127] When the conductive layer 216c is one of the source and drain of the transistor 141a, the conductive layer 216d corresponds to the other of the source and drain of the transistor 141a. Note that the conductive layer 216c functions as part of a wiring connected to the terminal 14, and the conductive layer 216d functions as part of a wiring connected to the terminal 15.

[0128] The insulating layer 218 is sandwiched between the conductive layer 220 and the semiconductor layer 214. The conductive layer 220 may be referred to as a gate electrode, and the insulating layer 218 may be referred to as a first gate insulating layer. The first gate insulating layer may be made of silicon oxide, aluminum oxide, hafnium oxide, or the like. For example, the first gate insulating layer may contain any one of silicon oxide, aluminum oxide, and hafnium oxide, thereby reducing the off-state current of the transistor 141a. To specifically describe the first gate insulating layer, the first gate insulating layer is preferably a SiO2 film, an Al2O3 film, or a HfO2 film. A part of the insulating layer 218 is provided in contact with the upper part of the n-type region 212a or the p-type region 212b. A part of the insulating layer 218 is provided so as to cover a part of the conductive layers 216a to 216f.

[0129] Moreover, the transistor 141a preferably has a recess gate structure. FIG. 5A shows an example in which the transistor 141a has a recess gate structure. The transistor 141a has a recess gate structure, so that the off-current of the transistor 141a is reduced. The recess gate structure is formed by etching a part of the semiconductor layer 214 at a position overlapping with the gate electrode forming the channel formation region, and thinning the semiconductor layer 214. The region of the semiconductor layer 214 thinned by etching is called a recess region. The recess region has the effect of making a high threshold voltage (normally off) because the depletion layer extending under the gate electrode can pinch off the channel formed by the 2DEG when no voltage is applied to the gate electrode (the transistor 141a is in an off state). Moreover, the non-recess region can pass a large current because the concentration of the 2DEG increases.

[0130] Furthermore, when the transistor 141a has a recess region, the recess region of the semiconductor layer 214 of the light emitting element 111 or the light emitting element 112 is formed by etching in the same process. By having the recess region of the light emitting element 111 or the light emitting element 112, the off current can be reduced. Therefore, the light emitting element 111 or the light emitting element 112 can suppress lighting due to leakage current or the like.

[0131] As a different example, the light-emitting element 111 or the light-emitting element 112 may not have a recess region. By not providing a recess region in the light-emitting element 111 or the light-emitting element 112, the responsiveness of the light-emitting element 111 or the light-emitting element 112 is improved. In addition, the signal amplitude of the first signal provided to the circuit 101 can be reduced. By reducing the signal amplitude of the first signal, the power consumption of the circuit that controls the circuit 101 can be reduced.

[0132] An insulating layer 222 is provided over the insulating layer 218. In order to reduce unevenness on a surface on which the transistor 141a, the light-emitting element 111, or the light-emitting element 112 is formed, the insulating layer 222 is preferably subjected to planarization treatment. The planarization treatment is not particularly limited, and can be performed by polishing treatment (for example, chemical mechanical polishing (CMP)) or dry etching treatment.

[0133] Moreover, by forming the insulating layer 222 using an insulating material having a planarizing function, the polishing process can be omitted. An organic insulating film is suitable for the insulating layer 222. Materials that can be used for the organic insulating film include acrylic resin, polyimide resin, epoxy resin, polyamide resin, polyimideamide resin, siloxane resin, benzocyclobutene resin, phenol resin, and precursors of these resins. In addition to the above organic materials, low dielectric constant materials (low-k materials) and the like can be used. Note that the insulating layer 222 may be formed by stacking a plurality of insulating layers made of these materials.

[0134] An insulating layer 224 is laminated on the insulating layer 222. The insulating layer 224 preferably has a function of suppressing diffusion of hydrogen contained in the semiconductor layer 212 or the semiconductor layer 214. Therefore, the insulating layer 224 preferably contains at least nitrogen. Although not shown in FIG. 5A, an insulating layer 224a can be laminated on the insulating layer 224. It is preferable that the insulating layer 224 contains more nitrogen than the insulating layer 224a, and the insulating layer 224a contains more oxygen than the insulating layer 224. The insulating layer 224a can supply oxygen to the semiconductor layer 230a or the semiconductor layer 230b described later.

[0135] The transistor 131, the transistor 132, the capacitor, the light receiving element 121, and the light receiving element 122 are provided over the insulating layer 224. First, the transistor 131 and the transistor 132 will be described.

[0136] A conductive layer 226a is provided over the insulating layer 224. An insulating layer 228 is provided over the conductive layer 226a. A semiconductor layer 230a is provided over the insulating layer 228 at a position overlapping with the conductive layer 226a. Note that the semiconductor layer 230a is a semiconductor layer of the transistor 131. A conductive layer 226b is provided over the insulating layer 224. An insulating layer 228 is provided over the conductive layer 226b. A semiconductor layer 230b is provided over the insulating layer 228 at a position overlapping with the conductive layer 226b. The semiconductor layer 230b is a semiconductor layer of the transistor 132. Therefore, the insulating layer 228 can be referred to as a second gate insulating layer.

[0137] The conductive layer 226a and the conductive layer 226b can be formed using the same material and in the same process. The insulating layer 228 is an insulating layer common to the transistor 131 and the transistor 132. The semiconductor layer 230a and the semiconductor layer 230b can be formed using the same material and in the same process.

[0138] The conductive layer 226a functions as a gate electrode of the transistor 131. The conductive layer 226b functions as a gate electrode of the transistor 131. The conductive layer 226a can prevent light 150c emitted by the light-emitting element 111 from entering the semiconductor layer 230a. The conductive layer 226b can prevent light 150d emitted by the light-emitting element 112 from entering the semiconductor layer 230b.

[0139] A conductive layer 232a and a conductive layer 232b are provided over the semiconductor layer 230a, and a conductive layer 232b and a conductive layer 232c are provided over the semiconductor layer 230b. The conductive layer 232a is provided over the insulating layer 228 provided over the conductive layer 226a. The conductive layer 232c is provided over the insulating layer 228 provided over the conductive layer 226b. The conductive layer 232b is provided over the insulating layer 228 provided over the semiconductor layer 230a and the semiconductor layer 230b, and is in contact with the conductive layer 220.

[0140] A part of the conductive layer 232b is in contact with sidewalls of the insulating layer 222, the insulating layer 224, and the insulating layer 228 that are exposed in a contact hole provided to electrically connect the conductive layer 232b and the conductive layer 220. The insulating layer 234 is provided over the conductive layer 232 and the conductive layers 232a to 232c. A part of the insulating layer 228 is in contact with parts of the conductive layer 232, the insulating layer 224, and the insulating layer 234.

[0141] A conductive layer 236a, a conductive layer 236b, and a conductive layer 236c are provided on the insulating layer 234. A part of the conductive layer 236a contacts the conductive layer 232a and a part of the conductive layer 226a. In addition, a part of the conductive layer 236a contacts a part of a sidewall of the insulating layer 228 exposed in a contact hole formed to electrically connect the conductive layer 232a and the conductive layer 226a, and a part of a sidewall of the insulating layer 234.

[0142] A portion of the conductive layer 236c contacts a portion of the conductive layer 226a. In addition, a portion of the conductive layer 236c contacts a portion of a sidewall of the insulating layer 228 exposed in a contact hole formed to electrically connect the conductive layer 226a and a portion of a sidewall of the insulating layer 234.

[0143] The conductive layer 236a is disposed at a position overlapping the semiconductor layer 230a and the insulating layer 234. Therefore, the conductive layer 236a has a function of the gate electrode of the transistor 131, a function of wiring connecting to the light receiving element 121, and a light blocking function of preventing light emitted by the light emitting element 111 from entering the semiconductor layer 230a.

[0144] The conductive layer 236c is disposed at a position overlapping with the semiconductor layer 230b and the insulating layer 234. Therefore, the conductive layer 236a has a function of a gate electrode or a backgate electrode of the transistor 131, a function of a wiring connecting to the light receiving element 121, and a light blocking function of preventing light emitted by the light emitting element 112 from entering the semiconductor layer 230b.

[0145] The conductive layer 236b is disposed at a position overlapping a portion of the conductive layer 232b, and is further provided so as to sandwich the insulating layer 234. Therefore, the capacitor 133 is formed by arranging the conductive layer 236b and the conductive layer 232b so as to sandwich the insulating layer 234.

[0146] An insulating layer 238 is provided over the conductive layers 236a to 236c. A conductive layer 240a and a conductive layer 240b are provided over the insulating layer 238. The conductive layer 240a corresponds to a pixel electrode of the light receiving element 121. The conductive layer 240b corresponds to a pixel electrode of the light receiving element 122. The conductive layer 240a is in contact with the conductive layer 236a, and the conductive layer 240b is in contact with the conductive layer 236c. Note that the insulating layer 218, the insulating layer 222, the insulating layer 224, the insulating layer 228, the insulating layer 234, and the insulating layer 238 preferably have a light-transmitting property.

[0147] An organic sensor layer 242a is provided on the conductive layer 240a, and a conductive layer 244a is provided on the organic sensor layer 242a. An organic sensor layer 242b is provided on the conductive layer 240b, and a conductive layer 244b is provided on the organic sensor layer 242b.

[0148] Therefore, the light receiving element 121 is composed of a conductive layer 240a, an organic sensor layer 242a, and a conductive layer 244a. The light receiving element 122 is composed of a conductive layer 240b, an organic sensor layer 242b, and a conductive layer 244b. It is preferable to provide an insulating layer 246 on the light receiving element 121 and the light receiving element 122. This can suppress deterioration of the light receiving element due to water, etc.

[0149] The light receiving element will be described with reference to Fig. 5B. In Fig. 5B, the conductive layers 240a and 240b are referred to as the conductive layer 240, the organic sensor layers 242a and 242b are referred to as the organic sensor layer 242, and the conductive layers 244a and 244b are referred to as the conductive layer 244.

[0150] The organic sensor layer 242 includes a buffer layer 242d, an active layer 242e, and a buffer layer 242f. The buffer layer 242d and the buffer layer 242f may each have a single-layer structure or a multilayer structure.

[0151] The buffer layer 242d can have, for example, one or both of a hole injection layer and a hole transport layer. Also, the buffer layer 242f can have, for example, one or both of an electron injection layer and an electron transport layer. Therefore, when the buffer layer 242d has a hole injection layer, the hole injection layer functions as a hole transport layer. Similarly, when the buffer layer 242f has an electron injection layer, the electron injection layer functions as an electron transport layer.

[0152] The hole injection layer is a layer that injects holes from the anode to the light emitting element and contains a material with high hole injection properties, such as an aromatic amine compound or a composite material containing a hole transport material and an acceptor material (electron accepting material).

[0153] The hole transport layer is a layer that transports holes generated in the active layer based on incident light to the anode. The hole transport layer is a layer that contains a hole transport material. -6 cm 2 A material having a hole mobility of 100 / Vs or more is preferable. Note that other materials can also be used as long as they have a higher hole transporting property than electron transporting property. As the hole transporting material, a material having a high hole transporting property such as a π-electron-rich heteroaromatic compound (e.g., a carbazole derivative, a thiophene derivative, a furan derivative, etc.) or an aromatic amine (a compound having an aromatic amine skeleton) is preferable.

[0154] The electron transport layer is a layer that transports electrons generated in the active layer based on incident light to the cathode. The electron transport layer is a layer that contains an electron transporting material. The electron transporting material is, for example, 1×10 -6 cm 2 A substance having an electron mobility of 100 / Vs or more is preferable. Note that, other substances may be used as long as they have a higher electron transporting property than holes. As the electron transporting material, a metal complex having a quinoline skeleton, a metal complex having a benzoquinoline skeleton, a metal complex having an oxazole skeleton, a metal complex having a thiazole skeleton, and the like, as well as oxadiazole derivatives, triazole derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, phenanthroline derivatives, quinoline derivatives having a quinoline ligand, benzoquinoline derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, and other materials having a high electron transporting property such as π-electron deficient heteroaromatic compounds including nitrogen-containing heteroaromatic compounds may be used.

[0155] The electron injection layer is a layer that injects electrons from the cathode to the light-emitting element, and is a layer that contains a material with high electron injection properties. As the material with high electron injection properties, an alkali metal, an alkaline earth metal, or a compound thereof can be used. As the material with high electron injection properties, a composite material containing an electron transport material and a donor material (electron donor material) can also be used.

[0156] The active layer 242e includes an organic compound. For example, the active layer 242e includes an n-type semiconductor material such as fullerene (e.g., C 60 , C 70 Examples of the p-type semiconductor material of the active layer 242e include organic semiconductor materials with electron-accepting properties, such as phthalocyanine (Pt) or derivatives thereof. Examples of the p-type semiconductor material of the active layer 242e include organic semiconductor materials with electron-accepting properties, such as copper (II) phthalocyanine (CuPc) or tetraphenyldibenzoperiflanthene (DBP). The active layer 242e is preferably formed by co-evaporation of an n-type semiconductor and a p-type semiconductor.

[0157] Therefore, the light receiving element 121 can be arranged above the light emitting element 111, and the light receiving element 122 can be arranged above the light emitting element 112. Therefore, the semiconductor relay 100 can form the light emitting element and the light receiving element on one substrate 210, so that the process of bonding the circuit 101 having the light emitting element and the circuit 102 having the light receiving element and the switch can be eliminated. Alternatively, the process of fixing the circuit 101 and the circuit 102 to an IC case can be eliminated.

[0158] Moreover, the conductive layer 232b has a function of isolating the light emitting element 111 and the light emitting element 112. Therefore, the conductive layer 232b can prevent the light 150c emitted by the light emitting element 111 from entering the light receiving element 122. Furthermore, the conductive layer 232b can prevent the light 150d emitted by the light emitting element 112 from entering the light receiving element 121. Note that the distance between the light emitting element 111 and the light receiving element 121 is preferably within 3 μm, and more preferably within 1 μm.

[0159] FIG. 6A is a diagram illustrating a semiconductor relay different from that in FIG. 5A.

[0160] FIG. 6A differs from FIG. 5A in that a conductive layer 215 is provided between the semiconductor layer 214 and the conductive layers 216a to 216f in order to improve the ohmic properties between the semiconductor layer 214 and the conductive layers 216a to 216f. Note that the conductive layer 215 may be referred to as an ohmic electrode. It is preferable to use a conductive oxide for the ohmic electrode. As an example, a zinc oxide film can be used as the conductive oxide. Note that a zinc oxide film has characteristics of an n-type semiconductor in an undoped state and is characterized by being easy to dope. As an example, a zinc oxide film can have a resistivity of 10 -3 〜10 -4 The resistivity is about Ω·cm. In addition, zinc oxide films can be formed by sputtering.

[0161] FIG. 6B is a diagram for explaining a semiconductor relay different from FIG. 6A. FIG. 6B is different from FIG. 6A in that an insulating layer 248 containing a phosphor is provided on the insulating layer 238. By disposing a phosphor between the light-emitting element and the light-receiving element, the light (light 150a, 150b) emitted from the light-emitting element is converted by the phosphor into light having a longer wavelength than the wavelength of the light. It is preferable that the wavelength range that the light-receiving element can detect is a longer wavelength range than the wavelength range of the light emitted by the light-emitting element. In addition, the insulating layer 248 containing a phosphor can function as a planarizing film. Therefore, the planarity of the area where the light-receiving element receives light is improved. In other words, the variation of the light-receiving element is improved.

[0162] Furthermore, the conductive layer 244 is preferably in contact with the conductive layer 236b, the insulating layer 238, and the insulating layer 248. Although not shown in FIG. 5A or FIG. 6A, in order to connect the conductive layer 244 and the conductive layer 236b, a processing step is required because the connection must be made through a contact hole. By directly connecting the conductive layer 244 and the conductive layer 236b, the wiring distance can be shortened and the processing steps can be reduced. Therefore, the chip size of the semiconductor relay 100 can be reduced and the productivity can be improved, and the processing cost can be reduced by reducing the processing steps of the semiconductor relay 100. In addition, the conductive layer 244 can be arranged so as to cover the organic sensor layer 242, thereby protecting the organic sensor layer 242 from moisture entering from the outside.

[0163] FIG. 7A is a diagram for explaining a semiconductor relay 100 different from FIG. 6B. FIG. 7A is different from FIG. 6B in that the light emitting element 111A and the light emitting element 112A are formed on the semiconductor layer 214. In the light emitting element 111A, a light emitting layer 213a epitaxially grown on the semiconductor layer 114 is provided, a semiconductor layer 215a epitaxially grown on the light emitting layer 213a is further provided, and a conductive layer 217a epitaxially grown on the semiconductor layer 215a is further provided. A conductive layer 216a is provided on the semiconductor layer 217a. The semiconductor layer 214 is n-type GaN, the light emitting layer 213a is GaN containing indium, and the semiconductor layer 215a is p-type GaN. As an example, the n-type GaN contains silicon or germanium, and the p-type GaN contains magnesium, zinc, cadmium, or beryllium. The conductive layer 217a is a conductive layer having light transmissivity.

[0164] In the light-emitting element 111A and the light-emitting element 112A, the light-emitting layer 213a and the light-emitting layer 213b, the semiconductor layer 215a and the semiconductor layer 215b, or the conductive layer 217a and the conductive layer 217b can be formed of the same material and in the same process. Note that the light-emitting element 111A and the light-emitting element 112A can be separated by dry etching.

[0165] In the semiconductor relay 100, the transistor 141a is preferably formed in a region provided for element isolation between the light-emitting element 111A and the light-emitting element 112A. The conductive layers 216a to 216f functioning as the anode or cathode electrodes of the light-emitting element 111A and the light-emitting element 112A, or the source or drain of the transistor 141a, can be formed of the same material and in the same process.

[0166] Fig. 7B is a diagram illustrating a semiconductor relay 100 different from Fig. 7A. Fig. 7B differs from Fig. 7A in that the transistor 141a, the light emitting element 111, and the light emitting element 112 are formed on a substrate 250. The substrate 250 is preferably made of gallium oxide.

[0167] In the light emitting element 111A, a semiconductor layer 252 epitaxially grown on a substrate 250 is provided, a light emitting layer 213a epitaxially grown on the semiconductor layer 252 is provided, a semiconductor layer 215a epitaxially grown on the light emitting layer 213a is further provided, and a conductive layer 217a epitaxially grown on the semiconductor layer 215a is further provided. A conductive layer 216a is provided on the semiconductor layer 217a. The substrate 250 is, for example, gallium oxide containing magnesium. The semiconductor layer 252 is, for example, n-type gallium oxide containing tin, the light emitting layer 213a is GaN containing indium, and the semiconductor layer 215a is p-type GaN.

[0168] In the semiconductor relay 100, the transistor 141c is preferably formed in a region provided for element isolation between the light-emitting element 111A and the light-emitting element 112A. Note that the transistor 141c has a MESFET structure containing gallium oxide in a channel formation region. Furthermore, the conductive layers 216a to 216f functioning as the anode or cathode electrodes of the light-emitting element 111A and the light-emitting element 112A, or the source or drain of the transistor 141a, can be formed of the same material and in the same process.

[0169] As described above, the circuit 101 and the circuit 102 are formed on the same substrate, thereby providing a semiconductor relay 100 with a novel configuration. In addition, the light emitted by the light-emitting element can be blocked by using the gate or back gate of the transistor 131 and the transistor 132, the conductive layer 232b connecting the transistors, the insulating layer 248 containing a phosphor, or the like. Therefore, the semiconductor relay 100 in which the first signal is well isolated from the second signal can be provided. In addition, the semiconductor relay 100 with good electrical characteristics that can handle low loss and large power can be provided by using an oxide semiconductor or a compound semiconductor for the transistor 104a or the transistor 104c. In addition, the semiconductor relay 100 with a configuration suitable for miniaturization can be provided by forming the circuit 101 and the circuit 102 on the same substrate and forming a light-receiving element that is arranged at a position overlapping with the light-emitting element. In addition, by having a light-emitting element and a light-receiving element, a highly reliable semiconductor relay 100 can be provided by having a configuration without a movable contact.

[0170] The formation area of ​​the light-emitting element includes the anode electrode and the cathode electrode. The formation area of ​​the light-receiving element is the larger of the anode electrode and the cathode electrode. Therefore, when the light-emitting element overlaps with the light-receiving element, it means that a part of the formation area of ​​the light-emitting element overlaps with a part of the formation area of ​​the light-receiving element.

[0171] As described above, the semiconductor relay 100 can be formed using a semiconductor process, and therefore can be called a semiconductor device.

[0172] This embodiment mode can be implemented by appropriately combining at least a part of it with other embodiment modes described in this specification.

[0173] (Embodiment 2) In this embodiment, a transistor that can be used for a semiconductor relay which is one embodiment of the present invention will be described.

[0174] <Transistor configuration example 1> 8A, 8B, and 8C are a top view and a cross-sectional view of a transistor 300 that can be used in a display device of one embodiment of the present invention and a periphery of the transistor 300. The transistor 300 can be used as the transistor 131 or the transistor 132 described in Embodiment 1 or the like.

[0175] FIG. 8A is a top view of the transistor 300. Also, FIG. 8B and FIG. 8C are cross-sectional views of the transistor 300. Here, FIG. 8B is a cross-sectional view of a portion indicated by a dashed line A1-A2 in FIG. 8A, and is also a cross-sectional view of the transistor 300 in the channel length direction. Also, FIG. 8C is a cross-sectional view of a portion indicated by a dashed line A3-A4 in FIG. 8A, and is also a cross-sectional view of the transistor 300 in the channel width direction. Note that in the top view of FIG. 8A, some elements are omitted for clarity.

[0176] The transistor 300 includes a metal oxide 330a disposed on a substrate (not shown), a metal oxide 330b disposed on the metal oxide 330a, a conductor 342a and a conductor 342b disposed spaced apart from each other on the metal oxide 330b, an insulator 380 disposed on the conductor 342a and the conductor 342b and having an opening formed between the conductor 342a and the conductor 342b, a conductor 360 disposed in the opening, an insulator 350 disposed among the metal oxide 330b, the conductor 342a, the conductor 342b, the insulator 380, and the conductor 360, and a metal oxide 330c disposed among the metal oxide 330b, the conductor 342a, the conductor 342b, the insulator 380, and the insulator 350. 8B and 8C, it is preferable that the top surface of the conductor 360 approximately coincides with the top surfaces of the insulator 350, the insulator 354, the metal oxide 330c, and the insulator 380. In the following, the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c may be collectively referred to as the metal oxide 330. Furthermore, the conductor 342a and the conductor 342b may be collectively referred to as the conductor 342.

[0177] As shown in Fig. 8B, in the transistor 300, the side surfaces of the conductor 342a and the conductor 342b facing the conductor 360 have a substantially vertical shape. Note that the transistor 300 shown in Fig. 8 is not limited to this, and the angle formed between the side surface and the bottom surface of the conductor 342a and the conductor 342b may be 10° or more and 80° or less, preferably 30° or more and 60° or less. Furthermore, the opposing side surfaces of the conductor 342a and the conductor 342b may have multiple surfaces.

[0178] 8B and 8C, it is preferable that an insulator 354 is disposed between the insulator 324, the metal oxide 330a, the metal oxide 330b, the conductor 342a, the conductor 342b, and the metal oxide 330c and the insulator 380. Here, it is preferable that the insulator 354 has an area in contact with the side surface of the metal oxide 330c, the top surface and side surface of the conductor 342a, the top surface and side surface of the conductor 342b, the side surface of the metal oxide 330a, the side surface of the metal oxide 330b, and the top surface of the insulator 324, as shown in FIG.

[0179] Note that, in the transistor 300, a three-layer structure of the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c is illustrated in a region where a channel is formed (hereinafter also referred to as a channel formation region) and in the vicinity thereof; however, the present invention is not limited thereto. For example, a two-layer structure of the metal oxide 330b and the metal oxide 330c or a four-layer or more layer structure may be provided. In addition, in the transistor 300, the conductor 360 is illustrated as having a two-layer structure, but the present invention is not limited thereto. For example, the conductor 360 may have a single-layer structure or a three-layer or more layer structure. In addition, each of the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c may have a two-layer or more layer structure.

[0180] For example, when metal oxide 330c has a layered structure consisting of a first metal oxide and a second metal oxide on the first metal oxide, it is preferable that the first metal oxide has a similar composition to metal oxide 330b, and the second metal oxide has a similar composition to metal oxide 330a.

[0181] Here, the conductor 360 functions as a gate electrode of the transistor, and the conductors 342a and 342b function as a source electrode and a drain electrode, respectively. As described above, the conductor 360 is formed so as to be embedded in the opening of the insulator 380 and in the region sandwiched between the conductors 342a and 342b. Here, the arrangement of the conductors 360, 342a, and 342b is selected in a self-aligned manner with respect to the opening of the insulator 380. That is, in the transistor 300, the gate electrode can be arranged between the source electrode and the drain electrode in a self-aligned manner. Therefore, the conductor 360 can be formed without providing a margin for alignment, so that the area occupied by the transistor 300 can be reduced. This allows the display device to have high resolution. In addition, the display device can have a narrow frame.

[0182] As shown in FIG. 8, the conductor 360 preferably includes a conductor 360a provided inside the insulator 350 and a conductor 360b provided so as to be embedded inside the conductor 360a.

[0183] 8A, 8B, and (C), the transistor 300 preferably has an insulator 314 arranged on a substrate (not shown), an insulator 316 arranged on the insulator 314, a conductor 305 arranged so as to be embedded in the insulator 316, an insulator 322 arranged on the insulator 316 and the conductor 305, and an insulator 324 arranged on the insulator 322. Also, it is preferable that a metal oxide 330a is arranged on the insulator 324.

[0184] Furthermore, an insulator 374 and an insulator 381 functioning as interlayer films are preferably provided over the transistor 300. Here, the insulator 374 is preferably provided in contact with top surfaces of the conductor 360, the insulator 350, the insulator 354, the metal oxide 330c, and the insulator 380.

[0185] It is preferable that the insulators 322, 354, and 374 have a function of suppressing the diffusion of at least one of hydrogen (e.g., hydrogen atoms, hydrogen molecules, etc.). For example, it is preferable that the insulators 322, 354, and 374 have lower hydrogen permeability than the insulators 324, 350, and 380. It is also preferable that the insulators 322 and 354 have a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.). For example, it is preferable that the insulators 322 and 354 have lower oxygen permeability than the insulators 324, 350, and 380.

[0186] Here, the insulator 324, the metal oxide 330, and the insulator 350 are separated by the insulators 380 and 381, and the insulators 354 and 374. Therefore, impurities such as hydrogen contained in the insulators 380 and 381 and excess oxygen contained in the insulators 324, the metal oxide 330a, the metal oxide 330b, and the insulator 350 can be prevented from being mixed into the insulators 324, the metal oxide 330a, the metal oxide 330b, and the insulator 350.

[0187] Also, it is preferable that a conductor 340 (conductor 340a and conductor 340b) is provided, which is electrically connected to the transistor 300 and functions as a plug. Note that an insulator 341 (insulator 341a and insulator 341b) is provided in contact with the side surface of the conductor 340 that functions as a plug. That is, the insulator 341 is provided in contact with the inner walls of the openings of the insulators 354, 380, 374, and 381. Also, a configuration may be adopted in which a first conductor of the conductor 340 is provided in contact with the side surface of the insulator 341, and a second conductor of the conductor 340 is provided further inside. Here, the height of the top surface of the conductor 340 and the height of the top surface of the insulator 381 can be made approximately the same. Note that, in the transistor 300, a configuration in which the first conductor of the conductor 340 and the second conductor of the conductor 340 are stacked is shown, but the present invention is not limited to this. For example, the conductor 340 may be provided as a single layer or a laminated structure of three or more layers. When the structure has a laminated structure, the layers may be distinguished by giving ordinal numbers in the order of formation.

[0188] In the transistor 300, a metal oxide that functions as an oxide semiconductor (hereinafter also referred to as an oxide semiconductor) is preferably used for the metal oxide 330 (metal oxide 330a, metal oxide 330b, and metal oxide 330c) including a channel formation region. For example, as the metal oxide that serves as the channel formation region of the metal oxide 330, a metal oxide having a band gap of 2 eV or more, preferably 2.5 eV or more, is preferably used as described above.

[0189] 8B, the thickness of the metal oxide 330b in a region not overlapping with the conductor 342 may be thinner than the thickness of the region overlapping with the conductor 342. This is formed by removing a part of the upper surface of the metal oxide 330b when forming the conductors 342a and 342b. When a conductive film that becomes the conductor 342 is formed on the upper surface of the metal oxide 330b, a low-resistance region may be formed near the interface with the conductive film. In this way, by removing the low-resistance region located between the conductors 342a and 342b on the upper surface of the metal oxide 330b, it is possible to suppress the formation of a channel in that region.

[0190] According to one embodiment of the present invention, a display device having a small transistor and high definition can be provided. Alternatively, a display device having a transistor with high on-state current and high luminance can be provided. Alternatively, a display device having a transistor with high speed operation can be provided. Alternatively, a display device having a transistor with stable electrical characteristics and high reliability can be provided. Alternatively, a display device having a transistor with low off-state current and low power consumption can be provided.

[0191] A detailed structure of a transistor 300 that can be used in a display device according to one embodiment of the present invention will be described.

[0192] The conductor 305 is disposed so as to have an overlapping region with the metal oxide 330 and the conductor 360. The conductor 305 is preferably embedded in the insulator 316. Here, it is preferable to improve the flatness of the upper surface of the conductor 305. For example, the average surface roughness (Ra) of the upper surface of the conductor 305 may be set to 1 nm or less, preferably 0.5 nm or less, and more preferably 0.3 nm or less. This can improve the flatness of the insulator 324 formed on the conductor 305 and improve the crystallinity of the metal oxide 330b and the metal oxide 330c.

[0193] Here, the conductor 360 may function as a first gate (also referred to as a top gate) electrode. The conductor 305 may function as a second gate (also referred to as a back gate) electrode. In this case, the threshold voltage of the transistor 300 can be controlled by changing the potential applied to the conductor 305 independently of the potential applied to the conductor 360. In particular, by applying a negative potential to the conductor 305, the threshold voltage of the transistor 300 can be made higher than 0 V, and the off-current can be reduced. Therefore, applying a negative potential to the conductor 305 can reduce the drain current of the transistor 300 when the potential applied to the conductor 360 is 0 V, compared to not applying a negative potential.

[0194] The conductor 305 is preferably provided to be larger than the channel formation region in the metal oxide 330. In particular, as shown in Fig. 8C, the conductor 305 preferably extends also in a region outside the end portion intersecting with the channel width direction of the metal oxide 330. In other words, the conductor 305 and the conductor 360 preferably overlap with each other via an insulator on the outside of the side surface of the metal oxide 330 in the channel width direction.

[0195] With the above structure, the channel formation region of the metal oxide 330 can be electrically surrounded by the electric field of the conductor 360 functioning as a first gate electrode and the electric field of the conductor 305 functioning as a second gate electrode.

[0196] 8C, the conductor 305 is extended to function as wiring. However, the present invention is not limited to this, and a conductor functioning as wiring may be provided below the conductor 305.

[0197] Moreover, it is preferable to use a conductive material containing tungsten, copper, or aluminum as a main component for the conductor 305. Note that although the conductor 305 is illustrated as a single layer, it may have a laminated structure, for example, a laminate of titanium or titanium nitride and the above-mentioned conductive material.

[0198] Also, a conductor having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), copper atoms, etc. (through which the above impurities are difficult to permeate) may be provided under the conductor 305. Alternatively, it is preferable to provide a conductor having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (through which the above oxygen is difficult to permeate). 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 above impurities or the above oxygen.

[0199] By providing a conductor having a function of suppressing oxygen diffusion under the conductor 305, it is possible to suppress a decrease in conductivity due to oxidation of the conductor 305. As a conductor having a function of suppressing oxygen diffusion, for example, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is preferably used. Therefore, the conductor 305 may be a single layer or a multilayer structure of the above-mentioned conductive materials.

[0200] The insulator 314 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the transistor 300 from the substrate side. Therefore, the insulator 314 is preferably made of an insulating material that has a function of preventing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), and copper atoms (through which the above impurities are unlikely to permeate). Alternatively, the insulator 314 is preferably made of an insulating material that has a function of preventing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (through which the above oxygen is unlikely to permeate).

[0201] For example, aluminum oxide, silicon nitride, or the like is preferably used as the insulator 314. This can prevent impurities such as water or hydrogen from diffusing from the substrate side of the insulator 314 to the transistor 300 side. Alternatively, it can prevent oxygen contained in the insulator 324 or the like from diffusing to the substrate side of the insulator 314.

[0202] The insulator 316, the insulator 380, and the insulator 381, which function as interlayer films, preferably have a lower dielectric constant than the insulator 314. By using a material with a low dielectric constant as the interlayer film, parasitic capacitance between wirings can be reduced. For example, 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 the like can be used as appropriate for the insulator 316, the insulator 380, and the insulator 381.

[0203] The insulators 322 and 324 function as gate insulators.

[0204] Here, the insulator 324 in contact with the metal oxide 330 preferably releases oxygen when heated. In this specification and the like, oxygen released by heating is sometimes referred to as excess oxygen. For example, the insulator 324 may be made of silicon oxide, silicon oxynitride, or the like as appropriate. By providing an insulator containing oxygen in contact with the metal oxide 330, oxygen vacancies in the metal oxide 330 can be reduced and the reliability of the transistor 300 can be improved.

[0205] Specifically, it is preferable to use an oxide material from which a portion of oxygen is released by heating as the insulator 324. 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 than 3.0 x 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 higher and 700° C. or lower, or 100° C. or higher and 400° C. or lower.

[0206] 8C , the thickness of the region of insulator 324 that does not overlap with insulator 354 and does not overlap with metal oxide 330b may be thinner than the thickness of the other regions. It is preferable that the thickness of the region of insulator 324 that does not overlap with insulator 354 and does not overlap with metal oxide 330b is a thickness that allows the oxygen to diffuse sufficiently.

[0207] Like the insulator 314 and the like, the insulator 322 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from entering the transistor 300 from the substrate side. For example, the insulator 322 preferably has lower hydrogen permeability than the insulator 324. By surrounding the insulator 324, the metal oxide 330, the insulator 350, and the like with the insulators 322, 354, and 374, impurities such as water or hydrogen can be suppressed from entering the transistor 300 from the outside.

[0208] Furthermore, it is preferable that the insulator 322 has 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). For example, it is preferable that the insulator 322 has lower oxygen permeability than the insulator 324. The insulator 322 is preferable because it has a function of suppressing the diffusion of oxygen and impurities, thereby reducing the diffusion of oxygen contained in the metal oxide 330 toward the substrate side. Furthermore, it is possible to suppress the reaction of the conductor 305 with the oxygen contained in the insulator 324 and the oxygen contained in the metal oxide 330.

[0209] The insulator 322 may be an insulator containing an oxide of one or both of insulating materials, aluminum and hafnium. As the insulator containing an oxide of one or both of aluminum and hafnium, aluminum oxide or hafnium oxide is preferably used. Alternatively, an oxide containing aluminum and hafnium (hafnium aluminate) or the like is preferably used. When the insulator 322 is formed using such a material, the insulator 322 functions as a layer that suppresses release of oxygen from the metal oxide 330 and the intrusion of impurities such as hydrogen from the periphery of the transistor 300 into the metal oxide 330.

[0210] 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.

[0211] The insulator 322 may be a single layer or a multilayer of an insulator containing a so-called high-k material, such as aluminum oxide, hafnium oxide, 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 insulator. By using a high-k material for the insulator that functions as the gate insulator, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0212] The insulator 322 and the insulator 324 may have a stacked structure of two or more layers. In that case, the stacked structure is not limited to a stacked structure made of the same material, and may be a stacked structure made of different materials. For example, an insulator similar to the insulator 324 may be provided under the insulator 322.

[0213] The metal oxide 330 includes a metal oxide 330a, a metal oxide 330b on the metal oxide 330a, and a metal oxide 330c on the metal oxide 330b. By having the metal oxide 330a below the metal oxide 330b, it is possible to suppress the diffusion of impurities from structures formed below the metal oxide 330a to the metal oxide 330b. Furthermore, by having the metal oxide 330c on the metal oxide 330b, it is possible to suppress the diffusion of impurities from structures formed above the metal oxide 330c to the metal oxide 330b.

[0214] The metal oxide 330 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 metal oxide 330a, 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 metal oxide 330b. In addition, in the metal oxide used for the metal oxide 330a, 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 metal oxide 330b. In addition, in the metal oxide used for the metal oxide 330b, 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 metal oxide 330a. In addition, the metal oxide 330c can be a metal oxide that can be used for the metal oxide 330a or the metal oxide 330b.

[0215] The metal oxide 330a, the metal oxide 330b, and the metal oxide 330c are preferably crystalline, and in particular, CAAC-OS is preferably used. Crystalline oxides such as CAAC-OS have few impurities and defects (oxygen vacancies, etc.), and have a dense structure with high crystallinity. This makes it possible to suppress the extraction of oxygen from the metal oxide 330b by the source electrode or the drain electrode. This makes it possible to suppress the extraction of oxygen from the metal oxide 330b even when heat treatment is performed. Therefore, the transistor 300 is stable against high temperatures (so-called thermal budget) in the manufacturing process.

[0216] In addition, it is preferable that the energy of the conduction band minimum of the metal oxide 330a and the metal oxide 330c is higher than the energy of the conduction band minimum of the metal oxide 330b. In other words, it is preferable that the electron affinity of the metal oxide 330a and the metal oxide 330c is smaller than the electron affinity of the metal oxide 330b. In this case, it is preferable that the metal oxide 330c is a metal oxide that can be used for the metal oxide 330a. Specifically, it is preferable that the atomic ratio of the element M among the constituent elements in the metal oxide used for the metal oxide 330c is larger than the atomic ratio of the element M among the constituent elements in the metal oxide used for the metal oxide 330b. It is also preferable that the atomic ratio of the element M to In in the metal oxide used for the metal oxide 330c is larger than the atomic ratio of the element M to In in the metal oxide used for the metal oxide 330b. In addition, in the metal oxide used for the metal oxide 330b, the atomic ratio of In to the element M is preferably larger than the atomic ratio of In to the element M in the metal oxide used for the metal oxide 330c.

[0217] Here, the energy level of the conduction band minimum changes gradually at the junction of the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c. In other words, it can be said that the energy level of the conduction band minimum at the junction of the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c 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 metal oxide 330a and the metal oxide 330b and the interface between the metal oxide 330b and the metal oxide 330c.

[0218] Specifically, the metal oxide 330a and the metal oxide 330b, and the metal oxide 330b and the metal oxide 330c have a common element other than oxygen (as a main component), so that a mixed layer with a low defect level density can be formed. For example, when the metal oxide 330b is an In-Ga-Zn oxide, the metal oxide 330a and the metal oxide 330c may be made of In-Ga-Zn oxide, Ga-Zn oxide, gallium oxide, or the like. The metal oxide 330c may also have a laminated structure. For example, a laminated structure of In-Ga-Zn oxide and Ga-Zn oxide on the In-Ga-Zn oxide, or a laminated structure of In-Ga-Zn oxide and gallium oxide on the In-Ga-Zn oxide can be used. In other words, a laminated structure of In-Ga-Zn oxide and an oxide not containing In may be used as the metal oxide 330c.

[0219] Specifically, the metal oxide 330a may have an atomic ratio of In:Ga:Zn=1:3:4 or 1:1:0.5. The metal oxide 330b may have an atomic ratio of In:Ga:Zn=4:2:3 or 3:1:2. The metal oxide 330c may have an atomic ratio of In:Ga:Zn=1:3:4, In:Ga:Zn=4:2:3, Ga:Zn=2:1, or Ga:Zn=2:5. Specific examples of the metal oxide 330c having a layered structure include a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and Ga:Zn=2:1 [atomic ratio], a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and Ga:Zn=2:5 [atomic ratio], and a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and gallium oxide.

[0220] At this time, the main path of the carriers is the metal oxide 330b. By configuring the metal oxide 330a and the metal oxide 330c as described above, the defect level density at the interface between the metal oxide 330a and the metal oxide 330b and at the interface between the metal oxide 330b and the metal oxide 330c can be reduced. Therefore, the influence of the interface scattering on the carrier conduction is reduced, and the transistor 300 can obtain a high on-current and high frequency characteristics. When the metal oxide 330c has a stacked structure, in addition to the effect of reducing the defect level density at the interface between the metal oxide 330b and the metal oxide 330c, it is expected that the constituent elements of the metal oxide 330c can be suppressed from diffusing to the insulator 350 side. More specifically, the metal oxide 330c has a stacked structure, and an oxide not containing In is positioned above the stacked structure, so that In that may diffuse to the insulator 350 side can be suppressed. Since the insulator 350 functions as a gate insulator, the diffusion of In leads to poor characteristics of the transistor. Therefore, by forming the metal oxide 330c into a laminated structure, a highly reliable display device can be provided.

[0221] The metal oxide 330 is preferably a metal oxide that functions as an oxide semiconductor. For example, a metal oxide having a band gap of 2 eV or more, preferably 2.5 eV or more, is preferably used as the metal oxide that serves as a channel formation region of the metal oxide 330. By using a metal oxide having a wide band gap in this manner, the off-state current of the transistor can be reduced. By using such a transistor, a display device with low power consumption can be provided.

[0222] Conductors 342 (conductors 342a and 342b) functioning as a source electrode and a drain electrode are provided on the metal oxide 330b. As the conductor 342, 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 preferred because they are conductive materials that are difficult to oxidize or materials that maintain their conductivity even when they absorb oxygen.

[0223] By providing the conductor 342 so as to be in contact with the metal oxide 330, the oxygen concentration may be reduced in the vicinity of the conductor 342 of the metal oxide 330. Furthermore, a metal compound layer containing a metal contained in the conductor 342 and a component of the metal oxide 330 may be formed in the vicinity of the conductor 342 of the metal oxide 330. In such a case, the carrier density increases in the region of the metal oxide 330 in the vicinity of the conductor 342, and the region becomes a low-resistance region.

[0224] Here, the region between the conductor 342a and the conductor 342b is formed to overlap the opening of the insulator 380. This allows the conductor 360 to be disposed in a self-aligned manner between the conductor 342a and the conductor 342b.

[0225] The insulator 350 functions as a gate insulator. The insulator 350 is preferably disposed in contact with the upper surface of the metal oxide 330c. The insulator 350 can be made of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, or silicon oxide having vacancies. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

[0226] The insulator 350 preferably has a reduced concentration of impurities such as water or hydrogen, similar to the insulator 324. The thickness of the insulator 350 is preferably greater than or equal to 1 nm and less than or equal to 20 nm.

[0227] Furthermore, a metal oxide may be provided between the insulator 350 and the conductor 360. The metal oxide preferably has a function of suppressing oxygen diffusion from the insulator 350 to the conductor 360. This can suppress oxidation of the conductor 360 due to oxygen contained in the insulator 350.

[0228] The metal oxide may function as a part of the gate insulator. Therefore, when silicon oxide, silicon oxynitride, or the like is used for the insulator 350, it is preferable to use a metal oxide that is a high-k material having a high relative dielectric constant. By forming the gate insulator into a stacked structure of the insulator 350 and the metal oxide, the transistor 300 can be made stable against heat and have a high relative dielectric constant. Therefore, it is possible to reduce the gate potential applied during the transistor operation while maintaining the physical thickness of the gate insulator. It is also possible to reduce the equivalent oxide thickness (EOT) of the insulator that functions as the gate insulator.

[0229] Specifically, it is possible to use a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, etc. In particular, it is preferable to use aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate), which is an insulator containing an oxide of either or both of aluminum and hafnium.

[0230] Although the conductor 360 is shown as having a two-layer structure in FIG. 8, it may have a single-layer structure or a laminated structure of three or more layers.

[0231] The conductor 360a is preferably made of a conductor having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), copper atoms, etc. Alternatively, it is preferable to use a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0232] Furthermore, since the conductor 360a has a function of suppressing oxygen diffusion, it is possible to suppress a decrease in the conductivity of the conductor 360b caused by oxidation of the conductor 360b due to oxygen contained in the insulator 350. As a conductive material having a function of suppressing oxygen diffusion, it is preferable to use, for example, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like.

[0233] The conductor 360b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. Since the conductor 360 also functions as wiring, it is preferable to use a conductor having high conductivity. For example, a conductive material containing tungsten, copper, or aluminum as a main component can be used. The conductor 360b may have a layered structure, for example, a layered structure of titanium or titanium nitride and the above conductive material.

[0234] 8A and 8C, in a region of the metal oxide 330b that does not overlap with the conductor 342, in other words, in a channel formation region of the metal oxide 330, the side surface of the metal oxide 330 is arranged to be covered with the conductor 360. This makes it easier for the electric field of the conductor 360, which functions as a first gate electrode, to act on the side surface of the metal oxide 330. This increases the on-current of the transistor 300, and improves the frequency characteristics of the transistor 300.

[0235] Like the insulator 314 and the like, the insulator 354 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from entering the transistor 300 from the insulator 380 side. For example, the insulator 354 preferably has lower hydrogen permeability than the insulator 324. Furthermore, as shown in FIGS. 8B and 8C , the insulator 354 preferably has a region in contact with the side surface of the metal oxide 330c, the top surface and side surface of the conductor 342a, the top surface and side surface of the conductor 342b, the side surface of the metal oxide 330a, the side surface of the metal oxide 330b, and the top surface of the insulator 324. With this configuration, it is possible to suppress hydrogen contained in the insulator 380 from entering the metal oxide 330 from the top surfaces or side surfaces of the conductor 342a, the conductor 342b, the metal oxide 330a, the metal oxide 330b, and the insulator 324.

[0236] Furthermore, it is preferable that the insulator 354 has a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) (i.e., the oxygen is less likely to permeate). For example, it is preferable that the insulator 354 has lower oxygen permeability than the insulator 380 or the insulator 324.

[0237] The insulator 354 is preferably formed by a sputtering method. By forming the insulator 354 by a sputtering method in an atmosphere containing oxygen, oxygen can be added to the insulator 324 near a region in contact with the insulator 354. This allows oxygen to be supplied from the region to the metal oxide 330 through the insulator 324. Here, the insulator 354 has a function of suppressing upward diffusion of oxygen, thereby suppressing diffusion of oxygen from the metal oxide 330 to the insulator 380. In addition, the insulator 322 has a function of suppressing downward diffusion of oxygen, thereby suppressing diffusion of oxygen from the metal oxide 330 to the substrate side. In this manner, oxygen is supplied to the channel formation region of the metal oxide 330. This reduces oxygen vacancies in the metal oxide 330, and suppresses the transistor from becoming normally on.

[0238] For example, an insulator containing one or both of an oxide of aluminum and hafnium may be formed as the insulator 354. Note that as the insulator containing one or both of an oxide of aluminum and hafnium, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like.

[0239] By covering the insulator 324, the insulator 350, and the metal oxide 330 with the insulator 354 having a barrier property against hydrogen, the insulator 380 is separated from the insulator 324, the metal oxide 330, and the insulator 350 by the insulator 354. This can prevent impurities such as hydrogen from entering the transistor 300 from the outside, thereby improving the electrical characteristics and reliability of the transistor 300.

[0240] The insulator 380 is provided over the insulator 324, the metal oxide 330, and the conductor 342 with the insulator 354 interposed therebetween. For example, the insulator 380 preferably includes silicon oxide, silicon oxynitride, silicon nitride oxide, 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 vacancies, or the like. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In addition, materials such as silicon oxide, silicon oxynitride, and silicon oxide having vacancies are preferable because they can easily form a region containing oxygen that is desorbed by heating.

[0241] It is preferable that the concentration of impurities such as water or hydrogen is reduced in the insulator 380. The top surface of the insulator 380 may be flattened.

[0242] Like the insulator 314, the insulator 374 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from entering the insulator 380. As the insulator 374, for example, an insulator that can be used for the insulator 314, the insulator 354, etc. can be used.

[0243] An insulator 381 functioning as an interlayer film is preferably provided over the insulator 374. Like the insulator 324 and the like, the insulator 381 preferably has a reduced concentration of impurities such as water or hydrogen.

[0244] The conductor 340a and the conductor 340b are arranged in openings formed in the insulator 381, the insulator 374, the insulator 380, and the insulator 354. The conductor 340a and the conductor 340b are provided facing each other with the conductor 360 in between. The height of the upper surfaces of the conductor 340a and the conductor 340b may be flush with the upper surface of the insulator 381.

[0245] In addition, insulator 341a is provided in contact with the inner walls of the openings of insulators 381, 374, 380, and 354, and a first conductor of conductor 340a is formed in contact with the side surface of insulator 341a. Conductor 342a is located at least in a part of the bottom of the opening, and conductor 340a is in contact with conductor 342a. Similarly, insulator 341b is provided in contact with the inner walls of the openings of insulators 381, 374, 380, and 354, and a first conductor of conductor 340b is formed in contact with the side surface of insulator 341b. Conductor 342b is located at least in a part of the bottom of the opening, and conductor 340b is in contact with conductor 342b.

[0246] The conductor 340a and the conductor 340b are preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor 340a and the conductor 340b may have a layered structure.

[0247] In addition, when the conductor 340 has a laminated structure, it is preferable to use the above-mentioned conductor having a function of suppressing the diffusion of impurities such as water or hydrogen for the conductor in contact with the metal oxide 330a, the metal oxide 330b, the conductor 342, the insulator 354, the insulator 380, the insulator 374, and the insulator 381. For example, it is preferable to use tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or ruthenium oxide. In addition, the conductive material having a function of suppressing the diffusion of impurities such as water or hydrogen may be used in a single layer or a laminated layer. By using the conductive material, it is possible to suppress the oxygen added to the insulator 380 from being absorbed by the conductor 340a and the conductor 340b. It is also possible to suppress the impurities such as water or hydrogen from the layer above the insulator 381 from being mixed into the metal oxide 330 through the conductor 340a and the conductor 340b.

[0248] As the insulator 341a and the insulator 341b, for example, an insulator that can be used for the insulator 354 or the like can be used. The insulator 341a and the insulator 341b are provided in contact with the insulator 354, and therefore can prevent impurities such as water or hydrogen from the insulator 380 or the like from being mixed into the metal oxide 330 through the conductor 340a and the conductor 340b. In addition, oxygen contained in the insulator 380 can be prevented from being absorbed by the conductor 340a and the conductor 340b.

[0249] Although not shown, a conductor functioning as wiring may be disposed in contact with the upper surface of the conductor 340a and the upper surface of the conductor 340b. The conductor functioning as wiring is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor may have a laminated structure, for example, a laminate of titanium or titanium nitride and the above-mentioned conductive material. The conductor may be formed so as to be embedded in an opening provided in an insulator.

[0250] (Embodiment 3) In this embodiment, a cloud-aligned composite oxide semiconductor (CAC-OS) and a c-axis aligned crystalline oxide semiconductor (CAAC-OS) that are metal oxides that can be used for the OS transistor described in the other embodiments will be described.

[0251] <Metal oxide composition> CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and the material as a whole has a function as a semiconductor. When CAC-OS or CAC-metal oxide is used in the active layer of a transistor, the conductive function is a function of flowing electrons (or holes) that become carriers, and the insulating function is a function of not flowing electrons that become carriers. By making the conductive function and the insulating function act complementarily, it is possible to impart a switching function (on / off function) to CAC-OS or CAC-metal oxide. By separating the respective functions in CAC-OS or CAC-metal oxide, it is possible to maximize both functions.

[0252] 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 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.

[0253] 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.

[0254] Also, 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. Also, 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, that is, a large on-current and a high field effect mobility can be obtained in the on-state of the transistor.

[0255] That is, CAC-OS or CAC-metal oxide can also be called a matrix composite or a metal matrix composite.

[0256] <Metal oxide structure> Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors other than those. Examples of non-single-crystal oxide semiconductors include CAAC-OS, polycrystalline oxide semiconductors, nanocrystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0257] In addition, when focusing on the crystal structure, oxide semiconductors may be classified differently from the above. Here, classification of crystal structures in oxide semiconductors will be described with reference to FIG. 9A. FIG. 9A is a diagram for explaining classification of crystal structures of oxide semiconductors, typically IGZO (metal oxide containing In, Ga, and Zn).

[0258] As shown in Figure 9A, IGZO is broadly classified into Amorphous, Crystalline, and Crystal. Amorphous includes completely amorphous. Crystalline includes c-axis aligned crystalline (CAAC), nanocrystalline (nc), and cloud-aligned composite (CAC). Crystalline excludes single crystal, poly crystal, and completely amorphous. Crystal includes single crystal and poly crystal.

[0259] The structure in the bold frame shown in Fig. 9A is an intermediate state between Amorphous and Crystal, and belongs to a new boundary region (New crystalline phase). This structure is in the boundary region between Amorphous and Crystal. In other words, this structure can be said to be a structure that is completely different from Amorphous, which is energetically unstable, or Crystal.

[0260] The crystal structure of the film or substrate can be evaluated using an X-ray diffraction (XRD) image. Figures 9B and 9C show XRD spectra of quartz glass and IGZO (also called crystalline IGZO) that has a crystal structure classified as Crystalline. Figure 9B shows the XRD spectrum of quartz glass, and Figure 9C shows the XRD spectrum of crystalline IGZO. The composition of the crystalline IGZO shown in Figure 9C is approximately In:Ga:Zn=4:2:3 [atomic ratio]. The thickness of the crystalline IGZO shown in Figure 9C is 500 nm.

[0261] As shown by the arrows in Figure 9B, the shape of the peak in the XRD spectrum of silica glass is almost symmetrical. On the other hand, as shown by the arrows in Figure 9C, the shape of the peak in the XRD spectrum of crystalline IGZO is asymmetrical. The asymmetric shape of the peak in the XRD spectrum clearly indicates the presence of crystals. In other words, if the shape of the peak in the XRD spectrum is not symmetrical, it cannot be said to be amorphous. Note that Figure 9C clearly shows the crystal phase (IGZO crystal phase) at or near 2θ=31°. It is presumed that the reason why the shape of the peak in the XRD spectrum is asymmetrical is due to the crystal phase (microcrystals).

[0262] Specifically, the XRD spectrum of crystalline IGZO shown in FIG. 9C has a peak at or near 2θ=34°. Microcrystals have a peak at or near 2θ=31°. When an oxide semiconductor film is evaluated using an X-ray diffraction pattern, the width of the spectrum on the lower angle side is wider than the peak at or near 2θ=34°, as shown in FIG. 9C. This suggests that the oxide semiconductor film contains microcrystals having a peak at or near 2θ=31°.

[0263] The crystal structure of the film can be evaluated from the diffraction pattern (also called the nanobeam electron diffraction pattern) observed by nanobeam electron diffraction (NBED). Figure 9D shows the diffraction pattern of an IGZO film formed at room temperature on the substrate. The IGZO film shown in Figure 9D was formed by sputtering using an oxide target with an In:Ga:Zn=1:1:1 [atomic ratio]. In the nanobeam electron diffraction method, electron diffraction was performed with a probe diameter of 1 nm.

[0264] As shown in Figure 9D, a spot-like pattern, not a halo, is observed in the diffraction pattern of the IGZO film deposited at room temperature. Therefore, it is presumed that the IGZO film deposited at room temperature is in an intermediate state, neither crystalline nor amorphous, and it cannot be concluded that it is in an amorphous state.

[0265] CAAC-OS has a c-axis orientation and a distorted crystal structure in which multiple nanocrystals are connected in the ab-plane direction. 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.

[0266] Nanocrystals are basically hexagonal, but are not limited to regular hexagonal shapes and may be non-regular hexagonal. In addition, the lattice arrangement of the distortion may be pentagonal, heptagonal, or other shapes. In the CAAC-OS, no clear grain boundary can be confirmed 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 thought to be because the 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.

[0267] A crystal structure in which clear grain boundaries are observed is called polycrystal. The grain boundaries are likely to become recombination centers and capture carriers, causing a decrease in the on-current of a transistor or a decrease in field-effect mobility. Therefore, CAAC-OS, in which clear grain boundaries are not observed, is one of the crystalline oxides having a crystal structure suitable for the semiconductor layer of a transistor. In order to form a CAAC-OS, a structure containing Zn is preferable. For example, In-Zn oxide and In-Ga-Zn oxide are suitable because they can suppress the occurrence of grain boundaries more than In oxide.

[0268] 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.

[0269] The CAAC-OS is an oxide semiconductor with high crystallinity. On the other hand, since no clear crystal grain boundaries can be identified in the CAAC-OS, it can be said that a decrease in electron mobility due to the crystal grain boundaries is unlikely to occur. In addition, since the crystallinity of an oxide semiconductor can be decreased by the inclusion of impurities or the generation of defects, the CAAC-OS can be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, the physical properties of an oxide semiconductor having the CAAC-OS are stable. Therefore, an oxide semiconductor having the CAAC-OS is resistant to heat and has high reliability. In addition, the CAAC-OS is stable against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, the use of the CAAC-OS in an OS transistor can increase the degree of freedom in the manufacturing process.

[0270] 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.

[0271] The a-like OS is an oxide semiconductor having a structure between the nc-OS and an amorphous oxide semiconductor. The a-like OS has a void or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS.

[0272] Oxide semiconductors have a variety of structures and have 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.

[0273] <Transistor Having Oxide Semiconductor> Next, the case where the oxide semiconductor is used for a transistor will be described.

[0274] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0275] In addition, it is preferable to use an oxide semiconductor with a low carrier concentration for the transistor. In order to reduce the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, a semiconductor having a low impurity concentration and a low density of defect states is referred to as a high-purity intrinsic semiconductor or a substantially high-purity intrinsic semiconductor.

[0276] In addition, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states might also be low.

[0277] In addition, charges trapped in the trap states of an oxide semiconductor take a long time to disappear and may behave as if they are fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0278] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. In order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in a nearby film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0279] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0280] When an oxide semiconductor contains silicon or carbon, which is one of the group 14 elements, defect levels are formed in the oxide semiconductor. For this reason, the concentrations of silicon or carbon in the oxide semiconductor and those near the interface with the oxide semiconductor (concentrations obtained by secondary ion mass spectrometry (SIMS)) are calculated as 2×10 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0281] Furthermore, when an oxide semiconductor contains an alkali metal or an alkaline earth metal, defect levels are formed and carriers are generated in some cases. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal is likely to have normally-on characteristics. For this reason, it is preferable to reduce the concentration of the alkali metal or the alkaline earth metal in the oxide semiconductor. Specifically, when the concentration of the alkali metal or the alkaline earth metal in the oxide semiconductor obtained by SIMS is reduced to 1×10 18 atoms / cm 3 Less than or equal to 2 x 10 16 atoms / cm 3 To the following:

[0282] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the oxide semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor is likely to have normally-on characteristics. Therefore, it is preferable that the nitrogen content in the oxide semiconductor is reduced as much as possible. For example, the nitrogen concentration in the oxide semiconductor is less than 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm3 Less than or equal to 1×10 18 atoms / cm 3 Less than 5×10, more preferably 17 atoms / cm 3 The following applies.

[0283] Furthermore, hydrogen contained in an oxide semiconductor reacts with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. In addition, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce hydrogen in the oxide semiconductor as much as possible. Specifically, when the hydrogen concentration in an oxide semiconductor measured by 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 Less than.

[0284] When an oxide semiconductor in which impurities are sufficiently reduced is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0285] This embodiment mode can be implemented by appropriately combining at least a part of it with other embodiment modes described in this specification.

[0286] (Embodiment 4) This embodiment mode will show an example of an electronic component or electronic device in which the semiconductor device or the like described in the above embodiment mode is incorporated.

[0287] <Electronic equipment> Next, an example of an electronic device equipped with the semiconductor relay will be described with reference to FIG.

[0288] 10 shows a perspective view of a semiconductor relay 700 and a perspective view of a functional module 730 in which the semiconductor relay 700, an electronic component 710, and a plurality of electronic components 720 are mounted. FIG. 10 shows an example in which the semiconductor relay 700 is mounted in the functional module 730. As an example, the electronic component 710 is preferably a processor. The electronic component 720 may be a memory, a memory module, or an integrated circuit. As an example, the integrated circuit may be an image processing circuit, a GPU (Graphics Processing Unit), a control circuit, or a drive circuit.

[0289] As an example, the processor can control power gating of each memory or memory module using the semiconductor relay 700. Note that it is preferable to use, as the memory, a dynamic oxide semiconductor random access memory (DOSRAM), a nonvolatile oxide semiconductor RAM (NOSRAM), or a flash memory that uses an OS transistor as a selection switch.

[0290] An example in which the functional module 730 in the above has a semiconductor relay 700 and a processor will be described. Note that the semiconductor relay 700 can be described in detail in the first embodiment, and therefore will not be described in detail. A first signal or a second signal is provided to a first circuit included in the semiconductor relay 700 by the processor. The first light-emitting element is turned on or off by the first signal provided to the first circuit. The second light-emitting element is turned on or off by the second signal provided to the first circuit.

[0291] The first data converted into a voltage by the first light receiving element is provided to the capacitance through the second transistor. The first light receiving element is provided with light emitted by the first light emitting element through the second transistor. The first transistor is controlled to be conductive by the first data stored in the capacitance. The first data stored in the capacitance is initialized by the third transistor being turned on by the second data converted into a voltage by the second light receiving element. The second light receiving element is provided with light emitted by the second light emitting element. The first transistor is controlled to be non-conductive by the first data stored in the capacitance being initialized. Thus, the semiconductor relay 700 can facilitate power gating of a memory or a memory module.

[0292] As a different example, although not shown in FIG. 10, the electronic components of the functional module 730 may include a motor or the like. Alternatively, the functional module 730 may be able to drive a motor or the like. A signal for controlling a motor may require a large amount of power (for example, a voltage of 10V or more, or a voltage of 100V or more, and a current of 1A or more). As an example, when the voltage width of a signal output by the processor is 3.3V, a semiconductor relay 700 may be provided between a wiring for a signal for controlling the motor and a wiring to which a power supply voltage is applied. Therefore, the motor can be directly controlled from the processor without using a driver IC for controlling the motor. Note that the operating voltage of the processor or the motor is shown as an example and is not limited thereto.

[0293] As another example, the semiconductor relay 700, the electronic component 710, or the electronic component 720 may be modularized or integrated into a single chip using a system in package (SiP) or a multi-chip module (MCM).

[0294] To mount the semiconductor relay 700 on another substrate, a mounting method such as BGA (Ball Grid Array), PGA (Pin Grid Array), SPGA (Staggered Pin Grid Array), LGA (Land Grid Array), QFP (Quad Flat Package), QFJ (Quad Flat J-leaded package), or QFN (Quad Flat Non-leaded package) can be used.

[0295] Subsequently, the semiconductor relay 700 or the functional module 730 can be used in various electronic devices.

[0296] As an example, the robot 7100 includes, in addition to the functional module 730, a battery, a microphone module, a camera module, a speaker, a display, various sensors (illuminance sensor, infrared sensor, ultrasonic sensor, acceleration sensor, piezo sensor, light sensor, gyro sensor, etc.), and a moving mechanism. The functional module 730 has a processor and the like, and has a function of controlling these peripheral devices. The functional module 730 can control the above-mentioned sensor group or power gating of a motor that controls the operation of the robot. This can reduce the power consumption of the battery.

[0297] The robot 7100 can communicate with the user using a microphone and a speaker. Therefore, the microphone can detect sound signals such as voice and environmental sound and analyze the contents. It is preferable to use AI for analyzing the contents. Therefore, the amount of calculation and power consumption increases when analyzing voice. It is also preferable to stop the analysis of voice by the microphone while the robot 7100 is stopped. Therefore, the microphone requires a large amount of power while analyzing voice, and it is preferable to perform power gating while the analysis of voice by the microphone is stopped. Therefore, it is preferable to use a semiconductor relay implemented in the functional module 730.

[0298] The camera module has a function of capturing images 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 images of the surroundings using the camera module, analyze the images using AI, identify the user, and detect the presence or absence of obstacles when moving. Therefore, the camera module requires a large amount of power while analyzing the images, and it is preferable to perform power gating while the image analysis of the camera module is stopped. Therefore, it is preferable to use a semiconductor relay implemented in the functional module 730.

[0299] The flying object 7120 has a propeller control module, a camera module, a battery, etc., and has a function of flying autonomously. The functional module 730 has a function of controlling these peripheral devices. The flying object 7120 can capture images of the surroundings using the camera module, and can detect the presence or absence of obstacles when moving by analyzing the images using AI. The propeller module controls the state of the flying object 7120 according to the direction in which the flying object 7120 moves, the wind direction, the wind speed, etc. The propeller module has a motor. The motor requires a large amount of power while it is driven, and it is preferable to power gate the motor while it is stopped. Therefore, it is preferable to use a semiconductor relay implemented in the functional module 730.

[0300] The cleaning robot 7140 has a motor that drives tires for movement, a display on the top surface, multiple cameras on the sides, a brush, operation buttons, various sensors, etc. The cleaning robot 7300 can move by itself, detect dirt, and suck up the dirt from a suction port provided on the bottom surface.

[0301] For example, the function module 730 can analyze images captured by the camera and determine the presence or absence of obstacles such as walls, furniture, or steps. The camera module can capture images of the surroundings and analyze the images using AI to determine the presence or absence of obstacles such as walls, furniture, or steps. In addition, if 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.

[0302] The automobile 7160 has an engine, tires, brakes, a steering device, a camera, etc. For example, the functional module 730 performs control to optimize the driving state of the automobile 7160 based on data such as navigation information, speed, engine state, gear selection state, and frequency of brake use. For example, image data captured by the camera is stored in the electronic component 720.

[0303] The semiconductor relay 700 and / or the functional module 730 can be incorporated into a TV device 7200 (television receiver), a smartphone 7210, a PC (personal computer) 7220, 7230, a game console 7240, a game console 7260, etc.

[0304] For example, the functional module 730 built into the TV device 7200 can function as an image engine. For example, the functional module 730 performs image processing such as noise removal and resolution up-conversion.

[0305] 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. The functional module 730 controls these peripheral devices.

[0306] 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 by 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 by wire. A semiconductor relay 700 and / or a functional module 730 can also be incorporated into the controller 7262.

[0307] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes. [Explanation of symbols]

[0308] 11: terminal, 12: terminal, 13: terminal, 14: terminal, 15: terminal, 16: terminal, 100: semiconductor relay, 101: circuit, 102: circuit, 104a: transistor, 104c: transistor, 110: lighting circuit, 110A: lighting circuit, 111: light-emitting element, 111A: light-emitting element, 112: light-emitting element, 112A: light-emitting element, 114: semiconductor layer, 120: detection circuit, 121: light-receiving element, 121A: light-receiving element, 121B: light-receiving element, 122: light-receiving element, 122A: light-receiving element, 122B: light-receiving element, 130: memory, 131: transistor, 132: transistor , 133: capacitance, 140: switch circuit, 140A: switch circuit, 141a: transistor, 141b: transistor, 141c: transistor, 144: diode, 210: substrate, 212: semiconductor layer, 212a: n-type region, 212b: p-type region, 213a: light-emitting layer, 213b: light-emitting layer, 214: semiconductor layer, 215: conductive layer, 215a: semiconductor layer, 215b: semiconductor layer, 216a: conductive layer, 216b: conductive layer, 216c: conductive layer, 216d: conductive layer, 216e: conductive layer, 216f: conductive layer, 217a: conductive layer, 217b: conductive layer, 218: insulation layer, 220: conductive layer, 222: insulating layer, 224: insulating layer, 224a: insulating layer, 226a: conductive layer, 226b: conductive layer, 228: insulating layer, 230a: semiconductor layer, 230b: semiconductor layer, 232: conductive layer, 232a: conductive layer, 232b: conductive layer, 232c: conductive layer, 234: insulating layer, 236a: conductive layer, 236b: conductive layer, 236c: conductive layer, 238: insulating layer, 240: conductive layer, 240a: conductive layer, 240b: conductive layer, 242: organic sensor layer, 242a: organic sensor layer, 242b: organic sensor layer, 242d: buffer layer, 242e: active layer, 242f: buffer layer, 244: conductive layer, 244a: conductive layer, 244b: conductive layer, 246: insulating layer, 248: insulating layer, 250: substrate, 252: semiconductor layer, 700: semiconductor relay, 710: electronic component, 720: electronic component, 730: functional module, 7100: robot, 7120: flying object, 7140: cleaning robot, 7160: automobile, 7200: TV device, 7210: smartphone, 7220: PC, 7230: PC, 7232: keyboard, 7233: monitor device, 7240: game machine, 7260: game machine, 7262: controller, 7300: cleaning robot

Claims

1. A semiconductor relay having a first circuit and a second circuit on a substrate, the first circuit has a first light-emitting element, a second light-emitting element, a first terminal, a second terminal, and a third terminal; the second circuit has a first transistor, a second transistor, a third transistor, a first light receiving element, a second light receiving element, a capacitance, a fourth terminal, and a fifth terminal; the first light emitting element and the first light receiving element are provided on the substrate; the second light emitting element and the second light receiving element are provided on the substrate; the first light emitting element has an area overlapping with the first light receiving element, the second light emitting element has an area overlapping with the second light receiving element, the first terminal is electrically connected to an anode of the first light-emitting element; the third terminal is electrically connected to an anode of the second light-emitting element; the second terminal is electrically connected to the cathode of the first light-emitting element and the cathode of the second light-emitting element; a gate of the first transistor is electrically connected to one of a source or a drain of the second transistor, one of a source or a drain of the third transistor, and one of the electrodes of the capacitor; the other of the source and the drain of the second transistor is electrically connected to the gate of the second transistor and the anode of the first light receiving element; a gate of the third transistor electrically connected to an anode of the second light receiving element; the fourth terminal is electrically connected to one of the source and the drain of the first transistor; the fifth terminal is electrically connected to the other of the source and the drain of the first transistor, the other of the source and the drain of the third transistor, the other of the electrodes of the capacitance, the cathode of the first light receiving element, and the cathode of the second light receiving element; light emitted from the first light emitting element is provided to the first light receiving element; the light emitted by the second light-emitting element is provided to the second light-receiving element; A semiconductor relay in which wiring electrically connecting the gate of the first transistor, one of the source or drain of the second transistor, and one of the source or drain of the third transistor is provided in a position that blocks light emitted by the first light-emitting element from entering the second light-receiving element, and is provided in a position that blocks light emitted by the second light-emitting element from entering the first light-receiving element.

2. A semiconductor device comprising the semiconductor relay according to claim 1 and a processor, the first circuit is provided with a first signal or a second signal by the processor; The first light emitting element is turned on or off by the first signal provided to the first circuit; the second light-emitting element is turned on or off by the second signal provided to the first circuit; the light emitted from the first light-emitting element in response to the first signal is provided to the first light-receiving element; the first light receiving element converts the light into a voltage to generate first data; the first data is stored in the capacitor via the second transistor; the first transistor is controlled to be conductive by the first data stored in the capacitor; the light emitted from the second light-emitting element in response to the second signal is provided to the second light-receiving element; the second light receiving element converts the light into a voltage to generate second data; the first data stored in the capacitor is initialized by the second data causing the third transistor to be turned on; the first transistor is controlled to be non-conductive by initializing the first data stored in the capacitance; A semiconductor device, wherein a voltage range of the fourth terminal provided with respect to the fifth terminal is greater than a voltage range of the first signal provided by the processor.

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