Display device, method for operating display device, and electronic apparatus

Abstract

The present invention provides a display device that can write data to a pixel at high speed. In this display device, a transistor capable of controlling a current that flows in response to light irradiation is used as a select transistor. The transistor is turned off by using a portion of a waveguide as a gate electrode and applying an appropriate potential to the waveguide, and is turned on by irradiating the transistor with light via the waveguide. Accordingly, since problems arising from interconnection resistance and interconnection capacitance do not occur, the select transistor can be operated at high speed, contributing to higher frame frequency and lower power consumption.

Description

Display device, display device operation method, and electronic device

[0001] One embodiment of the present invention relates to a display device, a method for operating the display device, and an electronic 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 semiconductor devices, display devices, light-emitting devices, power storage devices, memory devices, imaging devices, electronic devices, lighting devices, input devices, input / output devices, and driving methods thereof or manufacturing methods thereof. A semiconductor device refers to any device that can function by utilizing semiconductor characteristics.

[0003] In recent years, with the increase in the volume of information being transmitted, the development of technologies that combine electrical and optical communications has been progressing rapidly in the field of semiconductor devices. The use of light for the control and communication of semiconductor devices will enable high-capacity, high-speed information transmission and is expected to reduce the power consumption of semiconductor devices.

[0004] Photodiodes, phototransistors, and the like are known as semiconductor devices that utilize light, and by combining a photodiode with a MOSFET, a highly reliable switching device such as a relay without moving parts can be configured. For example, Patent Document 1 discloses a semiconductor relay that uses an organic EL element as a light source and an organic photosensor as a light-receiving element, and controls the operation of a transistor having an oxide in the semiconductor layer using light.

[0005] WO2020 / 212800

[0006] Takashi Koida, "High Mobility Transparent Conductive Film," National Institute of Advanced Industrial Science and Technology, AIST Photovoltaic Power Generation Research Results Report 2019, Internet <URL: https: / / unit.aist.go.jp / rpd-envene / PV / ja / results / 2019 / oral / T13.pdf>

[0007] In an active matrix display device, pixels are arranged near the intersections of gate lines and source lines, and the pixel transistors are made conductive by a signal potential output from a gate driver circuit to the gate lines, and a data potential output from a source driver circuit to the source lines is written to the pixels.

[0008] Although display devices for VR applications are small, they require high definition and a high frame frequency, so data must be written to pixels at high speed. Furthermore, in large display devices such as televisions or digital signage, the resistance and parasitic capacitance of the wiring that transmits signals increases, making it difficult to increase the frame frequency and resulting in increased power consumption.

[0009] Therefore, an object of one embodiment of the present invention is to provide a display device in which data can be written to pixels at high speed. Another object is to provide a display device in which the frame frequency can be easily increased. Another object is to provide a display device with low power consumption. Another object is to provide a method for operating a display device in which data can be written to pixels at high speed. Another object is to provide a novel semiconductor device, a novel display device, a novel electronic device, or the like.

[0010] 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.

[0011] One embodiment of the present invention relates to a display device in which data can be written to a pixel at high speed.

[0012] One embodiment of the present invention is a display device including a gate driver circuit, a source driver circuit, a light source, a pixel, a first wiring, and a second wiring. The pixel includes a first transistor. The light source is a diode light source. An anode of the light source is connected to the gate driver circuit. A cathode of the light source is connected to the first wiring. The second wiring is connected to the source driver circuit and one of a source and a drain of the first transistor. The first wiring has a region overlapping with a semiconductor layer of the first transistor with an insulating layer interposed therebetween. The first wiring includes a light-transmitting conductive layer. The light-transmitting conductive layer functions as a waveguide of light emitted from the light source and irradiated onto the semiconductor layer of the first transistor and also functions as a gate electrode of the first transistor.

[0013] The first wiring can have a function of supplying a fixed potential.

[0014] Another embodiment of the present invention is a display device including a gate driver circuit, a source driver circuit, a light source, a pixel, a first wiring, a second wiring, a third wiring, and a waveguide. The pixel includes a first transistor. The light source is a diode light source. An anode of the light source is connected to the gate driver circuit. A cathode of the light source is connected to the first wiring. The second wiring is connected to the source driver circuit and one of a source and a drain of the first transistor. The third wiring and the waveguide overlap with each other through a semiconductor layer of the first transistor. A first insulating layer is provided between the third wiring and the semiconductor layer. A second insulating layer is provided between the waveguide and the semiconductor layer. The waveguide functions as an optical path for light emitted from the light source and irradiated onto the semiconductor layer of the first transistor. The third wiring functions as a gate electrode of the first transistor.

[0015] Each of the first wiring and the third wiring can have a function of supplying a fixed potential.

[0016] The light emitted by the light source is preferably blue light or light with a wavelength shorter than that of blue light.

[0017] The pixel has a second transistor, a capacitor, and a light-emitting element, and one electrode of the capacitor can be connected to the other of the source or drain of the first transistor and the gate of the second transistor, and the other electrode of the capacitor can be connected to one of the source or drain of the second transistor and the anode of the light-emitting element.

[0018] Each of the first transistor and the second transistor preferably includes a metal oxide in a channel formation region, and the metal oxide is preferably indium oxide.

[0019] Another embodiment of the present invention is a method for operating a display device in which a potential lower than a source of a transistor included in a pixel and which controls writing of data is supplied to a gate of the transistor and data is written to the pixel by current flowing through the transistor when a semiconductor layer of the transistor is irradiated with light.

[0020] Further, an electronic device including the above display device and a catadioptric system is also one embodiment of the present invention.

[0021] According to one embodiment of the present invention, a display device in which data can be written to pixels at high speed can be provided. Alternatively, a display device in which the frame frequency can be easily increased can be provided. Alternatively, a display device with low power consumption can be provided. Alternatively, a method for operating a display device in which data can be written to pixels at high speed can be provided. Alternatively, a novel semiconductor device, a novel display device, a novel electronic device, or the like can be provided.

[0022] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these can be extracted from the description in the specification, drawings, claims, etc.

[0023] FIG. 1A is a block diagram illustrating a display device. FIG. 1B is a top view illustrating a display device. FIG. 1C is a cross-sectional view illustrating a display device. FIGS. 2A and 2B are block diagrams illustrating a display device. FIGS. 3A and 3B are diagrams illustrating the Id-Vg characteristics of a transistor. FIGS. 4A and 4B are circuit diagrams of a pixel. FIG. 4C is a diagram illustrating the operation of a pixel circuit. FIGS. 5A and 5B are diagrams illustrating the operation of a pixel circuit. FIG. 6A is a block diagram illustrating a display device. FIG. 6B is a top view illustrating a display device. FIG. 6C is a cross-sectional view illustrating a display device. FIGS. 7A and 7B are circuit diagrams of a pixel. FIG. 7C is a diagram illustrating the operation of a pixel circuit. FIGS. 8A and 8B are diagrams illustrating the operation of a pixel circuit. FIG. 9A is a block diagram illustrating a display device. FIG. 9B is a top view illustrating a display device. FIG. 9C is a cross-sectional view illustrating a display device. FIGS. 10A to 10E are diagrams illustrating a waveguide and peripheral elements. FIGS. 11A and 11C are diagrams illustrating the connection configuration of a gate driver circuit and a light source. FIG. 11B is a diagram illustrating a light source. FIG. 12 is a diagram illustrating a display device. FIG. 13 is a cross-sectional view illustrating a display device. FIG. 14 is a cross-sectional view illustrating a display device. FIGS. 15A and 15B are diagrams illustrating the carrier concentration dependence of Hall mobility. FIG. 15C is a cross-sectional view illustrating an indium oxide film. FIGS. 16A to 16F are diagrams illustrating an example of an electronic device. FIGS. 17A to 17G are diagrams illustrating an example of an electronic device. FIGS. 18A to 18C are diagrams illustrating an example of an electronic device.

[0024] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that various modifications in form and detail may be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below. In the configuration of the invention described below, the same parts or parts having similar functions will be designated by the same reference numerals in different drawings, and repeated description thereof may be omitted. Hatching of the same elements constituting the drawings may be omitted or changed as appropriate in different drawings.

[0025] Furthermore, even if a circuit diagram shows a single element, that element may be configured as multiple elements as long as there is no functional problem. For example, multiple transistors operating as switches may be connected in series or parallel. Also, a capacitor may be divided and placed in multiple locations.

[0026] Furthermore, one conductor may have multiple functions such as wiring, an electrode, and a terminal, and in this specification, multiple names may be used for the same element. Also, even when elements are shown as being directly connected to each other on a circuit diagram, in reality, the elements may be connected via one or more conductors, and in this specification, such a configuration is also included in the category of direct connection.

[0027] In this specification, "connection" includes, as an example, "electrical connection." Note that the term "electrical connection" is sometimes used to define the connection relationship between circuit elements as an object. Furthermore, "electrical connection" includes "direct connection" and "indirect connection." "A and B are directly connected" means that A and B are connected without the intervention of a circuit element (e.g., a transistor, a switch, etc.; note that wiring is not a circuit element). On the other hand, "A and B are indirectly connected" means that A and B are connected via one or more circuit elements. Note that A and B represent objects such as elements, circuits, wiring, electrodes, terminals, semiconductor layers, and conductive layers.

[0028] For example, assuming that a circuit including A and B is operating, if there is a time during the operation of the circuit when an electrical signal is exchanged or an interaction of electrical potential occurs between A and B, then it can be defined that "A and B are indirectly connected" as objects. Note that even if there is a time during the operation of the circuit when no electrical signal is exchanged or an interaction of electrical potential occurs between A and B, it can still be defined that "A and B are indirectly connected" as long as there is a time during the operation of the circuit when an electrical signal is exchanged or an interaction of electrical potential occurs between A and B.

[0029] An example of a case where "A and B are indirectly connected" is when A and B are connected via the source and drain of one or more transistors. On the other hand, an example of a case where it cannot be said that "A and B are indirectly connected" is when an insulator is present in the path from A to B. Specifically, there are cases where a capacitive element is connected between A and B, and cases where a gate insulating film of a transistor is present between A and B. Therefore, it cannot be said that "the gate (A) of a transistor and the source or drain (B) of the transistor are indirectly connected."

[0030] Another example of a case where it cannot be said that "A and B are indirectly connected" is when multiple transistors are connected via their sources and drains to the path from A to B, and a constant potential V is supplied to a node between one transistor and another transistor from a power supply, GND, etc.

[0031] Embodiment 1 In this embodiment, a display device of one embodiment of the present invention will be described with reference to drawings.

[0032] One embodiment of the present invention is a display device that can write data to pixels at high speed and consumes low power. A transistor that can control current flowing in response to light irradiation is used as a selection transistor in the pixels of the display device.

[0033] The transistor uses a part of a conductive waveguide as a gate electrode. The transistor can be turned off by applying an appropriate potential to the waveguide, and turned on by irradiating the semiconductor layer of the transistor with light through the waveguide, allowing current to flow.

[0034] Typically, the ON / OFF state of a select transistor is controlled by the voltage applied to the gate. Therefore, as display devices become larger and higher resolution, problems such as delays in data writing and increased power consumption due to wiring resistance and capacitance arise.

[0035] In one embodiment of the present invention, the off / on state of the selection transistor can be controlled depending on whether or not light is irradiated, and therefore problems due to wiring resistance and wiring capacitance do not occur, allowing the selection transistor to operate at high speed, which contributes to an improvement in frame frequency and a reduction in power consumption.

[0036] 1A is a block diagram illustrating a display device according to one embodiment of the present invention. FIG. 1B is a schematic top view of some elements included in the display device, illustrating an example of the arrangement and connection of the elements. FIG. 1C is a cross-sectional view taken along line A1-A2 in FIG. 1B.

[0037] A display device according to one embodiment of the present invention includes a pixel array 12 that constitutes a display portion, a light source 25, a gate driver circuit 20, and a source driver circuit 30. The pixel array 12 includes pixels 11 arranged in a matrix. Each pixel 11 includes a transistor Tr1 and a circuit block 10 connected to the transistor Tr1. The transistor Tr1 functions as a selection transistor that selects a pixel to which data is written. The circuit block 10 includes a display element and the like, and will be described in detail later.

[0038] The conductive layer 52, which functions as either the source or drain of the transistor Tr1, is connected to a wiring SL, which functions as an output line of the source driver circuit 30. The conductive layer 53, which functions as the other of the source or drain of the transistor Tr1, is connected to the circuit block 10. A waveguide OWG, which also functions as a wiring that functions as a gate electrode, is used for the gate of the transistor Tr1. Light can be irradiated from the waveguide OWG to the semiconductor layer 51 of the transistor Tr1 through an insulating layer 55. The insulating layer 55 functions as a gate insulating film.

[0039] The waveguide OWG can be connected to the anode of a diode-type light source 25 and a fixed potential line. The cathode of the light source 25 is connected to the output line SOUT of the gate driver circuit 20. Although a GND line is shown as an example of the fixed potential line in FIGS. 1A and 1C, it may also be a line that supplies a fixed potential, such as a low-potential power supply line or a line that supplies a specific potential.

[0040] 1C , light L emitted from the light source 25 can be incident on the waveguide OWG via a light incident portion 41 provided in a part of the waveguide OWG. The light L incident on the waveguide OWG propagates through the waveguide OWG while repeatedly being reflected at the interfaces between the insulating layers 55 and 56, and can be irradiated onto the transistor Tr1 via a light emitting portion 42 provided in a part of the waveguide OWG above the transistor Tr1.

[0041] Although details of the transistor Tr1 will be described later, when a potential lower than that of the source is supplied to the gate and the semiconductor layer is irradiated with light, a current can flow between the source and drain. Therefore, data can be written to the pixel 11 by the current flowing through the transistor Tr1.

[0042] Here, problems with conventional display devices will be described. Fig. 2A is a block diagram for simply explaining a conventional display device, showing an example in which a pixel 11 has a transistor Tr1 as a selection transistor, a transistor Tr2 as a drive transistor, and a light-emitting element (also referred to as a light-emitting device) EL as a display element. Note that the transistor Tr2 and the light-emitting element EL correspond to elements of the circuit block 10 shown in Fig. 1A. Furthermore, the output line SOUT of the gate driver circuit 20 is connected to the wiring GL. The source driver circuit 30 is connected to the wiring SL.

[0043] When the gate driver circuit 20 outputs a signal potential (S1) to the line GL to turn on the transistor Tr1, the transistor Tr1 becomes conductive. As a result, a data potential (Data) output from the source driver circuit 30 to the line SL is written to the gate of the transistor Tr2. A current I according to the data potential (Data) flows through the transistor Tr2 and the light-emitting element EL. Ｄａｔａ flows, causing the light emitting element EL to emit light.

[0044] In a display device, an image is rewritten for each frame, so that a potential that turns on the transistor Tr1 and a potential that turns off the transistor Tr1 are alternately supplied to the wiring GL. In other words, the wiring GL is repeatedly charged and discharged. Therefore, the resistance R and parasitic capacitance C of the wiring GL increase power consumption and hinder improvement of the frame frequency due to delays. Note that the parasitic capacitance C also includes the gate capacitance of the transistor connected to the wiring GL.

[0045] Display devices for VR applications use relatively small display devices, but to enhance the sense of immersion, it is necessary to increase the field of view (FOV) by magnifying it with an optical system. For example, assuming an FOV of 120°, achieving 60 PPD (Pixels Per Degree), equivalent to a visual acuity of 1.0, requires 7,200 pixels in one direction. Furthermore, to reduce the afterimage caused by eye movement, operation at a high frame frequency is also necessary. As the number of pixels and frame frequency increase, the signal volume increases dramatically, and it is necessary to transmit this signal without delay. Furthermore, in television devices or digital signage that use relatively large display devices, the wiring length inevitably becomes longer, resulting in increased wiring resistance and wiring capacitance of the metal wiring that transmits signals.

[0046] 2B is a block diagram illustrating a simplified example of a display device according to one embodiment of the present invention. Fig. 2B differs from Fig. 2A in the manner in which a signal is output from a gate driver circuit 20 to a transistor Tr1. Specifically, the wiring GL is replaced with a light source 25 and a waveguide OWG.

[0047] In a display device according to one embodiment of the present invention, a signal potential output from the gate driver circuit 20 is converted into light by the light source 25 and supplied to the transistor Tr1 via the waveguide OWG. That is, by transmitting the signal from the gate driver circuit 20 to the transistor Tr1 as an optical signal via an optical waveguide rather than as an electrical signal via metal wiring, signal loss can be reduced and the transmission amount can be increased.

[0048] Although a gate voltage is supplied to the transistor Tr1 through the waveguide OWG, the waveguide OWG is connected to a fixed potential line, so there is no charge movement associated with the on / off of the transistor Tr1, and the transistor Tr1 is less susceptible to the effects of the resistance R and the parasitic capacitance C. Therefore, it can be said that the power consumption is low, data can be written to the pixel at high speed, and the frame frequency can be easily increased.

[0049] Next, a specific structure and operation of a pixel in a display device according to one embodiment of the present invention will be described. First, characteristics of a transistor that can be used as the transistor Tr1 will be described.

[0050] 3A and 3B show examples of the Id-Vg characteristics of a transistor having indium oxide, an oxide semiconductor, in a channel formation region. The transistor is a top-gate type with W / L = 50 μm / 6 μm. FIG. 3A shows the characteristics at Vd = 0.1 V, and FIG. 3B shows the characteristics at Vd = 10 V. The drain current (I ｄａｒｋ ), and the drain current under light irradiation (I ｐｈｏｔｏ ) is shown.

[0051] Since the transistor has a structure in which a metal is used for the gate electrode, I ｐｈｏｔｏ The characteristics of (a) and (b) were obtained by irradiating the entire transistor with light from diagonally above, so that the light penetrates into the semiconductor layer. A high-pressure mercury lamp with a dominant wavelength of 365 nm was used as the light source.

[0052] Indium oxide is an oxide semiconductor with a band gap of approximately 3 eV, and when irradiated with light having a wavelength of approximately 410 nm (corresponding to blue light) or a wavelength shorter than blue light, many carriers are excited and can be extracted as photocurrent. For example, as shown in Figures 3A and 3B, by fixing the gate voltage (Vg) to -1 V and depending on whether or not light is irradiated, good switching characteristics can be obtained with an on-off ratio of five or more orders of magnitude at Vd = 0.1 V and an on-off ratio of six or more orders of magnitude at Vd = 10 V. Note that, as shown in Figures 3A and 3B, when Vg is -1 V or less, the I ｄａｒｋ is the lower detection limit of the measuring instrument (1 × 10 −１４ A) The values ​​are around the same value and contain noise. Therefore, the actual I ｄａｒｋ It can be inferred that is even smaller and the on / off ratio is even larger.

[0053] In this way, by applying an appropriate voltage (for example, a voltage lower than that of the source) to the gate and controlling whether or not to irradiate the semiconductor layer (oxide semiconductor) of the transistor with light having a wavelength equivalent to or shorter than blue light, the on / off state of the transistor can be controlled in the same way as when the gate voltage is changed. That is, a transistor having an oxide semiconductor in a channel formation region can be used as a selection transistor. Since the transistor has photosensitivity, there is no need to provide a separate photodiode or the like, and a pixel circuit can be easily configured.

[0054] Although indium oxide is used as an oxide semiconductor here, the present invention is not limited to this. Similar characteristics can be obtained depending on the band gap even when other oxide semiconductors described later are used. Furthermore, the size of the transistor can be appropriately set depending on the type of display device to which it is applied.

[0055] Furthermore, photosensitivity is also exhibited when silicon is used for the semiconductor layer of a transistor. However, because silicon has a band gap of approximately 1.1 eV, carriers are excited even by light of green and red wavelengths. This can cause malfunctions in display devices that have a visible light source for the pixel. Therefore, it is preferable to use an oxide semiconductor with a wide band gap, in which the wavelength component that excites carriers is limited to the wavelength of blue light or less, for the semiconductor layer of the selection transistor of a pixel.

[0056] Next, the circuit configuration of the pixel 11 will be described. Fig. 4A shows an example of a pixel having a light-emitting element, which includes transistors Tr1, Tr2, Tr3, a capacitance element C1, and a light-emitting element EL. The transistors Tr2, Tr3, and the capacitance element C1 correspond to the elements of the circuit block 10 shown in Fig. 1A. The light-emitting element EL can be an organic EL element, an LED element, or the like. The LED element can be, for example, a light-emitting diode such as a micro LED or a mini LED. A micro LED is a light-emitting diode having a chip area of ​​10,000 μm ２The following light-emitting diodes are used: Also, mini LEDs are those with a chip area of ​​10,000 μm ２ Larger than 1mm ２ The following light-emitting diodes:

[0057] Although the pixel circuit using the light-emitting element EL shown in FIG. 4A as a display element will be described as an example here, a pixel circuit using the liquid crystal element LC shown in FIG. 4B as a display element can also be applied.

[0058] As described above, the waveguide OWG is connected to a fixed potential line, and a portion thereof functions as the gate electrode of the transistor Tr1. In the pixel circuit shown in FIG. 4A, another portion of the waveguide OWG also functions as the gate electrode of the transistor Tr3. Like the transistor Tr1, the transistor Tr3 can be irradiated with light via the waveguide OWG, and can be controlled to be turned on or off depending on whether or not light is irradiated. Note that the transistor Tr3 may also be omitted.

[0059] One of the source or drain of transistor Tr1 is connected to wiring SL. The other of the source or drain of transistor Tr1 is connected to the gate of transistor Tr2 and one electrode of capacitor C1. One of the source or drain of transistor Tr2 is connected to wiring AL. One of the source or drain of transistor Tr2 is connected to the other electrode of capacitor C1, the anode of light-emitting element EL, and one of the source or drain of transistor Tr3. The cathode of light-emitting element EL is connected to a fixed potential line. The other of the source or drain of transistor Tr3 is connected to wiring RL.

[0060] A fixed potential is applied to the waveguide OWG. Light propagates through the waveguide OWG as a selection signal. The selection signal has a light-on state that turns the transistor on and a light-off state that turns the transistor off.

[0061] A data potential is applied to the wiring SL. A reset potential is applied to the wiring RL. An anode potential is applied to the wiring AL. A cathode potential is applied to the wiring CL. The anode potential is higher than the cathode potential. The reset potential applied to the wiring RL can be set so that the potential difference between the reset potential and the cathode potential is smaller than the threshold voltage of the light-emitting device EL. The reset potential can be higher than the cathode potential, the same as the cathode potential, or lower than the cathode potential.

[0062] The transistors Tr1 and Tr3 function as switches. The transistor Tr2 functions as a transistor for controlling the current flowing through the light-emitting device EL. For example, it can be said that the transistor Tr1 functions as a selection transistor, the transistor Tr2 functions as a drive transistor, and the transistor Tr3 functions as a reset transistor.

[0063] Here, transistors Tr1 to Tr3 can be transistors having metal oxide in their channel formation regions (hereinafter referred to as OS transistors). Alternatively, OS transistors can be used for the transistors Tr1 to Tr3, and a transistor having silicon (single crystal silicon, polycrystalline silicon (LTPS), microcrystalline silicon, or amorphous silicon) in its channel formation region (hereinafter referred to as a Si transistor) can be used for the transistors Tr2.

[0064] Alternatively, one or more of the transistors included in the driver circuit may be Si transistors and the remaining transistors may be OS transistors. Alternatively, one or more of the driver circuits may be Si transistors and the remaining transistors may be OS transistors.

[0065] In particular, indium oxide is preferably used for an OS transistor. By using single-crystal or polycrystalline indium oxide, a high-performance transistor having high field-effect mobility, high on-state current, extremely low off-state current, and high reliability can be realized.

[0066] As the OS transistor, a transistor including an oxide semiconductor in a semiconductor layer in which a channel is formed can be used. The semiconductor layer preferably contains, for example, indium. Alternatively, the semiconductor layer preferably contains indium, M (M is one or more selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc.

[0067] A transistor using an oxide semiconductor, which has a wider band gap and a lower carrier concentration than silicon, can achieve an extremely small off-state current. Therefore, due to the small off-state current, charge stored in a capacitor connected in series with the transistor can be held for a long period of time. Therefore, it is preferable to use transistors including oxide semiconductors for the transistors Tr1 and Tr3 connected in series with the capacitor C1. By using transistors including oxide semiconductors as the transistors Tr1 and Tr3, charge held in the capacitor C1 can be prevented from leaking through the transistor Tr1 or the transistor Tr3. Furthermore, because charge held in the capacitor C1 can be held for a long period of time, a still image can be displayed for a long period of time without rewriting pixel data.

[0068] 4A and 4B, the transistors are depicted as n-channel transistors, but p-channel transistors may also be used. In particular, using a p-type transistor for transistor Tr2 is preferable because it allows the source potential to be fixed to the anode potential, thereby enabling stable operation of the circuit.

[0069] Next, the operation of pixel 11 will be described. Fig. 4C is a diagram illustrating a state (holding state) in which data is not written to the pixel circuit of Fig. 4A. Here, the holding state shows a state in which the light-emitting element EL does not emit light (black display).

[0070] A fixed potential line is connected to the waveguide OWG, and for example, a low potential ("L1") is always supplied to it. Therefore, the potential of the cathode of the light source 25 is always the low potential ("L1"). The low potential ("L1") is, for example, a potential lower than the sources of the transistors Tr1 and Tr3. The low potential ("L1") can be, for example, the GND potential.

[0071] In the hold state, the signal potential output to the output line SOUT of the gate driver circuit 20 (see FIG. 1A) is a low potential ("L2"), and the difference between "L1" and "L2" is equal to or less than the forward voltage of the light source 25, i.e., the potential difference at which the diode-type light source 25 does not emit light.

[0072] When no light is incident on the waveguide OWG, the transistors Tr1 and Tr3 are in the off state. Therefore, the data potential written to the gate of the transistor Tr2 is maintained. At this time, if the Vgs (gate-source voltage) of the transistor Tr2 is equal to or lower than the threshold voltage (Vth), the light-emitting element EL does not emit light and displays black.

[0073] Next, a state in which data is written to the pixel circuit (write operation) will be described with reference to Fig. 5A. At the timing of writing data to the pixel, the gate driver circuit 20 outputs a high potential ("H") as a signal potential to the output line SOUT. Here, if the potential difference between the output line SOUT and the fixed potential line is equal to or greater than the forward voltage of the light source 25, a forward current (I Ｆ ) flows. That is, the light source 25 emits light.

[0074] Therefore, light L is incident on the waveguide OWG, and the transistors Tr1 and Tr3 are turned on. At this time, the transistor Tr3 is turned on, so that a reset potential (Vr) is supplied to the source of the transistor Tr2, and the source potential is reset to a low potential. At the same time, the transistor Tr1 is turned on, so that the data potential Vr supplied from the line SL is reset to a low potential. Ｄａｔａ can be written to the gate of transistor Tr2.

[0075] Next, the hold state accompanied by light emission of the light-emitting element EL will be described with reference to Fig. 5B. After the data write operation shown in Fig. 5A, the gate driver circuit 20 outputs a low potential ("L") as a signal potential to the output line SOUT. Therefore, as in Fig. 4C, the light source 25 is turned off, no light is incident on the waveguide OWG, and the transistors Tr1 and Tr3 are turned off.

[0076] Here, the data potential written to the gate of the transistor Tr2 is maintained. Therefore, if the Vgs (gate-source voltage) of the transistor Tr2 is equal to or higher than the threshold voltage (Vth), a current I Ｄａｔａ The operation of the pixel shown in FIG.

[0077] Next, a configuration different from that shown in FIGS. 1A to 1C will be described with reference to FIGS. 6A to 6C. FIG. 6A is a block diagram illustrating a display device. FIG. 6B is a schematic diagram showing some elements of the display device as viewed from above. FIG. 6C corresponds to a cross-sectional view taken along line B1-B2 shown in FIG. 6B.

[0078] The display device shown in FIGS. 6A to 6C differs from the display device shown in FIGS. 1A to 1C in that the waveguide OWG does not also serve as the gate electrode of the transistor Tr1, and a separate wiring GL is provided.

[0079] 6A to 6C , the wiring GL and the waveguide OWG have an overlapping region with the semiconductor layer 51 of the transistor interposed therebetween. A part of the wiring GL functions as a gate electrode, and an insulating layer 57 is provided between the wiring GL and the semiconductor layer 51. The insulating layer 57 functions as a gate insulating film. An insulating layer 55 is provided between the waveguide OWG and the semiconductor layer 51. The insulating layer 55 functions as an interlayer insulating film.

[0080] A fixed potential line is connected to the wiring GL. On the other hand, the waveguide OWG only needs to have the function of propagating light, and does not need to be conductive. Therefore, it is not necessary to supply a specific potential to the waveguide OWG. However, to prevent noise, the waveguide OWG may be made of a conductive material and a specific potential lower than the source potential of the transistor Tr1 may be supplied to the waveguide OWG.

[0081] In addition, in the configurations shown in FIGS. 1A to 1C, the cathode of the light source 25 is connected to a fixed potential line via the waveguide OWG, but in the configurations shown in FIGS. 6A to 6C, the cathode of the light source 25 can be connected to a fixed potential line at a low potential.

[0082] Next, a configuration of a pixel 11 that can be applied to the configurations shown in Figures 6A to 6C will be described. Figure 7A shows an example of a pixel having a light-emitting element, and differs from the configuration shown in Figure 4A in that the waveguide OWG is not connected to a fixed potential line and that a wiring GL is provided that connects the gate electrodes of transistors Tr1 and Tr3. The wiring GL is connected to a fixed potential line.

[0083] Although the pixel circuit using the light-emitting element EL shown in FIG. 7A as a display element will be described as an example here, a pixel circuit using the liquid crystal element LC shown in FIG. 7B as a display element can also be applied.

[0084] Next, the operation of the pixel 11 shown in Fig. 7A will be described. Fig. 7C is a diagram illustrating a state (holding state) in which data is not written to the pixel circuit of Fig. 7A. Here, the holding state shows a state in which the light-emitting element EL does not emit light.

[0085] A low potential ("L1") is always supplied to the fixed potential line connected to the cathode of the light source 25. Therefore, the potential of the cathode of the light source 25 is always low potential ("L1"). In addition, a low potential ("L2") is always supplied to the fixed potential line connected to the wiring GL. The low potential ("L2") is, for example, a potential lower than the sources of the transistors Tr1 and Tr3. Note that the low potential ("L1") and the low potential ("L2") may be the same potential. The low potential ("L1") and the low potential ("L2") may be, for example, GND potential.

[0086] In the hold state, the signal potential output to the output line SOUT of the gate driver circuit 20 (see FIG. 1A) is a low potential ("L3"), and the difference between "L1" and "L3" is equal to or less than the forward voltage of the light source 25, i.e., a potential difference at which the diode-type light source 25 does not emit light.

[0087] When no light is incident on the waveguide OWG, the transistors Tr1 and Tr3 are in the off state. That is, the data potential written to the gate of the transistor Tr2 is maintained. At this time, if the Vgs (gate-source voltage) of the transistor Tr2 is equal to or lower than the threshold voltage (Vth), the light-emitting element EL does not emit light.

[0088] Next, a state in which data is written to the pixel circuit (write operation) will be described with reference to Fig. 8A. At the timing of writing data to the pixel, the gate driver circuit 20 outputs a high potential ("H") as a signal potential to the output line SOUT. Here, if the potential difference between the potential of the output line SOUT and the fixed potential line connected to the light source 25 is equal to or greater than the forward voltage of the light source 25, a forward current (I Ｆ ) flows. That is, the light source 25 emits light.

[0089] Therefore, light L is incident on the waveguide OWG, and the transistors Tr1 and Tr3 are turned on. At this time, the transistor Tr3 is turned on, so that a reset potential (Vr) is supplied to the source of the transistor Tr2, and the source potential is reset to a low potential. At the same time, the transistor Tr1 is turned on, so that the data potential Vr supplied from the line SL is reset to a low potential. Ｄａｔａ can be written to the gate of transistor Tr2.

[0090] Next, the holding state accompanied by light emission of the light-emitting element EL will be described with reference to Fig. 8B. After the data write operation shown in Fig. 8A, the gate driver circuit 20 outputs a low potential ("L3") as a signal potential to the output line SOUT. Therefore, as in Fig. 7C, the light source 25 is turned off, no light is incident on the waveguide OWG, and the transistors Tr1 and Tr3 are turned off.

[0091] Here, the data potential written to the gate of the transistor Tr2 is maintained. Therefore, if the Vgs (gate-source voltage) of the transistor Tr2 is equal to or higher than the threshold voltage (Vth), a current I Ｄａｔａ The operation of the pixel shown in FIG.

[0092] 8A and 8B show a configuration in which a gate voltage is applied to the transistor Tr1 and the transistor Tr3 using a wiring GL, but as shown in FIGS. 9A to 9C , a configuration without the wiring GL is also possible. FIG. 9A is a block diagram illustrating a display device. FIG. 9B is a schematic diagram of some elements of the display device as seen from above. FIG. 9C corresponds to a cross-sectional view taken along C1-C2 in FIG. 9B .

[0093] 3A and 3B , in one embodiment of the present invention, a potential lower than the source potential is applied to the gate to turn the transistor off. Therefore, a gate wiring is required to apply a gate electric field to the transistor. On the other hand, if the transistor has sufficient off-state characteristics when no electric field is applied to the gate (corresponding to a gate voltage of 0 V), an element for applying an electric field to the semiconductor layer 51 of the transistor can be omitted. For example, this characteristic can be obtained by controlling the amount of fixed charge in the insulating layer 55 in contact with the semiconductor layer 51.

[0094] Therefore, the configurations shown in Figures 9A to 9C can also be used. Note that for the circuit configurations and operations of the pixels shown in Figures 9A to 9C, the descriptions in Figures 7A to 8B can be referred to, except for the description of the gate wiring.

[0095] 10A is a perspective cross-sectional view illustrating the waveguide OWG and its surrounding elements. The waveguide OWG is surrounded by layers 43 and 44. In terms of an optical fiber, the waveguide OWG corresponds to a core layer, and layers 43 and 44 correspond to cladding layers.

[0096] That is, when the refractive index of the waveguide OWG is n1, the refractive index of the layer 43 is n2, and the refractive index of the layer 44 is n3, n1 is configured to be larger than both n2 and n3. This makes it easier for total reflection to occur at the interfaces between the waveguide OWG and the layers 43 and 44, respectively, allowing light to propagate within the waveguide OWG. Note that the layers 43 and 44 may be made of the same material and have the same refractive index.

[0097] 1A to 1C , the waveguide OWG also serves as the gate wiring, and therefore, a transparent conductive layer such as an In oxide, an In—Sn oxide (ITO), or an In—Ga—Zn oxide can be used as the waveguide OWG. These materials have a transmittance of 80% or more even at a wavelength corresponding to violet light (approximately 380 nm), and are therefore suitable for the waveguide OWG.

[0098] 1A to 1C, the layer 43 (insulating layer 55) also functions as a gate insulating film, and the layer 44 (insulating layer 56) also functions as an interlayer insulating film.

[0099] For example, when ITO is used as the waveguide OWG, the refractive index at a wavelength of around 400 nm is 2.0 to 2.1, so that the insulating layers 55 and 56 can be made of aluminum oxide, which has a refractive index at the same wavelength of about 1.8, or silicon oxide, which has a refractive index at the same wavelength of about 1.47.

[0100] 6A to 6C and 9A to 9C, the waveguide OWG does not also function as a gate electrode, so an insulating layer can be used as the waveguide OWG. For example, silicon nitride or aluminum oxide, which has a refractive index of about 2.0 at a wavelength of about 400 nm, can be used as the waveguide OWG, and silicon oxide or the like can be used for the insulating layers 55 and 56. A light-transmitting organic layer can also be used as the waveguide OWG.

[0101] It is preferable to use a diode-type light source with strong directionality as the light source 25. A diode-type light source is a light source that has a pn junction configuration and emits light by passing a current through it, causing electrons and holes to recombine and emitting energy as light. Examples of diode-type light sources include light-emitting diodes (LEDs) and laser diodes.

[0102] 10B, an organic EL element (OLED) can also be used. The organic EL element can be formed directly on the layer 44 or the waveguide OWG, and can also be formed using the same process as the light-emitting element of the pixel. Furthermore, since the organic EL element can be formed as a surface light source, the area of ​​the light incident portion 41 can be increased, and optical connection with the waveguide OWG can be facilitated.

[0103] The upper limit of the wavelength of the light L emitted by the light source 25 varies depending on the band gap of the semiconductor layer of the transistor to be operated, and the wavelength can be selected according to the material. As mentioned above, when indium oxide with a band gap of 3.0 eV is used, the upper limit is a wavelength equivalent to blue light. In principle, the upper limit is a wavelength equivalent to the energy of the band gap, but in actual semiconductor layers, there are various levels between the valence band and the conduction band, and carriers are excited into the conduction band even with energy slightly smaller than the energy of the band gap. Therefore, when indium oxide with a band gap of 3.0 eV (equivalent to 410 nm) is used, the upper limit is a wavelength equivalent to blue light of about 450 nm.

[0104] The lower limit of the wavelength of the light L emitted by the light source 25 varies depending on the transmittance of the material used for the waveguide OWG. When ITO, which is a light-transmitting conductive layer, is used for the waveguide OWG, the transmittance is 10% or less at wavelengths of 300 nm (equivalent to ultraviolet light) or less, so the lower limit is preferably 350 nm or more, and more preferably 370 nm or more.

[0105] When an insulating layer is used for the waveguide OWG, it exhibits high transmittance even for light with a short wavelength, and therefore, in principle, can be used with light with a wavelength of 300 nm or less. However, because high-energy short-wavelength light can cause deterioration of transistors and their peripheral elements, the wavelength is preferably 300 nm or more, and more preferably 350 nm or more.

[0106] In the above, the light L emitted by the light source 25 may be light whose wavelength has been converted using quantum dots or the like.

[0107] 10C, the light L emitted by the light source 25 can be incident on the waveguide OWG via a light incident portion 41 provided in a part of the waveguide OWG. The light incident portion 41 can be a grating formed with minute surface irregularities.

[0108] Furthermore, the light L propagating through the waveguide OWG can be emitted to the outside via the light emitting portion 42. In one aspect of the present invention, the light emitting portion 42 is provided on the selection transistor of the pixel. For the light emitting portion 42, in addition to a grating similar to the light incident portion 41, an object having a refractive index different from that of the waveguide OWG, an object having a high reflectance, or the like can be used.

[0109] It is preferable that the waveguide OWG is provided on a plane as much as possible. Therefore, when the waveguide OWG is provided in a region with a step, it is preferable to provide a planarizing film or the like to eliminate the step. When the waveguide OWG is provided in a region with a step and the shape of the step is reflected in the waveguide OWG, it may function as a light emitting portion in the same way as when a grating is provided.

[0110] Furthermore, light L emitted by the light source 25 can also be incident into the waveguide OWG from the end of the waveguide OWG, as shown in Fig. 10D. Here, if the spot size of the light emitted by the light source 25 is larger than the diameter of the waveguide OWG, the diameter can be gradually increased toward the entrance at the end of the waveguide OWG, as shown in Fig. 10E. Furthermore, a lens 25L can be provided between the exit portion and entrance of the light source 25 to converge the light and make it incident into the waveguide OWG.

[0111] FIG. 11A is an example block diagram of a sequential circuit that can be used as the gate driver circuit 20 shown in FIG. 1A and other figures. Shift register circuits SR corresponding to the number of output lines SOUT are cascaded, with a clock signal CLK[1] input to odd-numbered shift register circuits SR and a clock signal CLK[2] input to even-numbered shift register circuits. The clock signal CLK[2] is an inverted version of the clock signal CLK[1]. A start pulse (SSP) is input to the signal input terminal LIN of the first-stage shift register circuit SR, and an end pulse (SEP) is input to the signal input terminal RIN of the final-stage shift register circuit SR. The SEP can also be generated by providing a dummy-stage shift register circuit SR.

[0112] The output line SOUT can output, for example, a high power supply potential. Therefore, by connecting the anode of a diode-type light source 25 to the output line SOUT and connecting a fixed potential line of low potential to the cathode, the light source 25 can be made to emit light in accordance with the operation of the sequential circuit.

[0113] As shown in FIG. 11B , the light source 25 can be configured by connecting two or more diode-type light sources in series. By using multiple diode-type light sources, the amount of light incident on the waveguide OWG can be increased, compensating for light attenuation within the waveguide OWG and increasing the transistor current. Furthermore, even if the overall light amount of the light source 25 is increased by connecting them in series, the lifetime is equivalent to that of a single diode-type light source if the current density is the same. Therefore, the reliability of the light source 25 can be improved.

[0114] By using a sequential circuit of this configuration and connecting a light source 25 to the output line SOUT, for example, when the display unit has 2560 scanning lines, light that functions as a selection signal can be sequentially output to the waveguides OWG

[0001] to

[2560] .

[0115] 11C , a high-potential wiring AL is connected to the anode of the light source 25, and a low-potential wiring CL is connected to the cathode. A switch that operates in response to the potential of the output line of the sequential circuit can be provided between the light source 25 and the wiring AL or CL.

[0116] Light emitted by the light source 25 is incident on the switch 26. The switch 26 is connected to the output line SOUT and the waveguide OWG of the sequential circuit, and can output the optical signal input from the light source 25 to the waveguide OWG in accordance with the signal potential input from the output line SOUT.

[0117] The switch 26 may be a MEMS optical switch using a micromirror, or a mechanical optical switch that switches optical paths by moving a mirror or optical fiber using an actuator.

[0118] By using the configuration of FIG. 11B, the number of light sources 25 can be reduced to one for a plurality of waveguides OWG, and the manufacturing yield can be improved.

[0119] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0120] In this embodiment, a configuration example of a display device that can be applied to an electronic device of one embodiment of the present invention will be described. The display device is a high-resolution display panel and is suitable for use in a display portion of a VR device such as a head-mounted display and a wearable device that can be worn on a head, such as a glasses-type AR device. The display device can also be applied to a display portion of a high-resolution television, digital signage, or the like.

[0121] 12 shows a perspective view of the display module 280. The display module 280 has a display panel 200A and an FPC 290. Note that the display panel of the display module 280 is not limited to the display panel 200A, and may be any of the other display panels described below.

[0122] The display module 280 has a substrate 291 and a substrate 292. The display module 280 has a display unit 281. The display unit 281 is a region for displaying an image, and has a display element between the substrate 291 and the substrate 292.

[0123] 13 shows a cross-sectional view of a display panel 200A that can be used as the display module 280. The display panel 200A includes a substrate 331, a light-emitting element 110, a capacitor 240, a transistor 320, and a transistor 310. Note that a display device using a light-emitting element as a display element is exemplified here.

[0124] The transistor 320 is a transistor (OS transistor) in which a metal oxide (also referred to as an oxide semiconductor) is used for a semiconductor layer in which a channel is formed.

[0125] The transistor 320 includes a semiconductor layer 321 , an insulating layer 323 , a conductive layer 324 , a pair of conductive layers 325 , an insulating layer 326 , and a conductive layer 327 .

[0126] 12 . An insulating layer 332 is provided over the substrate 331. The insulating layer 332 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the substrate 331 to the transistor 320 and prevents oxygen from being released from the semiconductor layer 321 toward the insulating layer 332. The insulating layer 332 can be, for example, a film through which hydrogen or oxygen is less likely to diffuse than a silicon oxide film, such as an aluminum oxide film, a hafnium oxide film, or a silicon nitride film.

[0127] A conductive layer 327 is provided over the insulating layer 332, and an insulating layer 326 is provided to cover the conductive layer 327. The conductive layer 327 functions as a first gate electrode of the transistor 320, and part of the insulating layer 326 functions as a first gate insulating layer. An oxide insulating film such as a silicon oxide film is preferably used for at least a portion of the insulating layer 326 that is in contact with the semiconductor layer 321. The top surface of the insulating layer 326 is preferably planarized.

[0128] The semiconductor layer 321 is provided over the insulating layer 326. The semiconductor layer 321 preferably includes a metal oxide (also referred to as an oxide semiconductor) film exhibiting semiconductor characteristics. A pair of conductive layers 325 is provided on and in contact with the semiconductor layer 321 and functions as a source electrode and a drain electrode.

[0129] An insulating layer 328 is provided to cover top surfaces and side surfaces of the pair of conductive layers 325 and side surfaces of the semiconductor layer 321, and an insulating layer 264 is provided over the insulating layer 328. The insulating layer 328 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the insulating layer 264 or the like into the semiconductor layer 321 and prevents oxygen from being released from the semiconductor layer 321. The insulating layer 328 can be an insulating film similar to the insulating layer 332.

[0130] An opening reaching the semiconductor layer 321 is provided in the insulating layer 328 and the insulating layer 264. An insulating layer 323 in contact with the top surface of the semiconductor layer 321 and a conductive layer 324 are buried in the opening. The conductive layer 324 functions as a second gate electrode, and the insulating layer 323 functions as a second gate insulating layer.

[0131] The upper surfaces of the conductive layer 324, the insulating layer 323, and the insulating layer 264 are planarized so that their heights are the same or approximately the same, and insulating layers 329 and 265 are provided to cover them.

[0132] The insulating layers 264, 265, and 267 function as interlayer insulating layers. The insulating layer 329 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the insulating layer 265 or the like to the transistor 320. The insulating layer 329 can be formed using an insulating film similar to the insulating layers 328 and 332.

[0133] The plug 274 connected to one of the pair of conductive layers 325 is provided so as to be embedded in the insulating layer 267, the insulating layer 265, the insulating layer 329, and the insulating layer 264. Here, the plug 274 preferably has a conductive layer 274a covering the side surfaces of the openings of the insulating layer 267, the insulating layer 265, the insulating layer 329, the insulating layer 264, and the insulating layer 328 and a part of the upper surface of the conductive layer 325, and a conductive layer 274b in contact with the upper surface of the conductive layer 274a. In this case, the conductive layer 274a is preferably made of a conductive material through which hydrogen and oxygen do not easily diffuse.

[0134] Note that the structure of the transistor included in the display panel of this embodiment is not particularly limited. For example, a planar transistor, a staggered transistor, an inverted staggered transistor, or the like can be used. Furthermore, either a top-gate transistor or a bottom-gate transistor structure may be used. Alternatively, gates may be provided above and below a semiconductor layer in which a channel is formed.

[0135] The transistor 320 has a structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates. The two gates may be connected and the transistor may be driven by supplying the same signal to them. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other.

[0136] Further, a transistor 310 is provided over the insulating layer 326. The transistor 310 is a selection transistor, and one of a source electrode and a drain electrode thereof is connected to a gate of a transistor 320, which is a driving transistor, through a conductive layer. The transistor 310 is a transistor whose on / off state is controlled by light guided in a waveguide OWG. For details of the transistor 310, refer to Embodiment 1. The transistors 310 and 320 are both OS transistors, and their semiconductor layers can be manufactured using a common process.

[0137] An insulating layer 267 is provided over the transistor 310 and the transistor 320 , and the capacitor 240 is provided over the insulating layer 267 .

[0138] The capacitor 240 has a conductive layer 241, a conductive layer 245, and an insulating layer 243 located therebetween. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.

[0139] The conductive layer 241 is provided over the insulating layer 267 and is buried in the insulating layer 254. The conductive layer 241 is connected to one of the source and drain of the transistor 310 by a plug 271 buried in the insulating layer 267. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 interposed therebetween.

[0140] An insulating layer 255a is provided to cover the capacitor 240, an insulating layer 255b is provided on the insulating layer 255a, and an insulating layer 255c is provided on the insulating layer 255b. The capacitor 240 and the transistor 310 are connected to a pixel electrode 111, which is one electrode of the light-emitting element, via a plug 256. The plug 256 is provided to be embedded in the insulating layer 243, the insulating layer 255a, the insulating layer 255b, and the insulating layer 255c.

[0141] An inorganic insulating film can be preferably used for each of the insulating layers 255a, 255b, and 255c. For example, it is preferable to use a silicon oxide film for the insulating layer 255a and the insulating layer 255c, and a silicon nitride film for the insulating layer 255b. This allows the insulating layer 255b to function as an etching protection film. In this embodiment, an example is shown in which part of the insulating layer 255c is etched to form a recess, but the insulating layer 255c does not necessarily have to have a recess.

[0142] The light-emitting element 110 is provided on the insulating layer 255c. It is preferable to use, for example, an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode) as the light-emitting element 110. The light-emitting material of the EL element may be an inorganic compound (such as a quantum dot material) as well as an organic compound. Note that, although a display device is provided with a plurality of sub-pixels emitting different light of different colors, such as red (R), green (G), and blue (B), the following describes a light-emitting element in one sub-pixel that emits light of any given color.

[0143] The light-emitting element 110 includes a pixel electrode 111, an organic layer 112, a common layer 114, and a common electrode 113. The organic layer 112 included in the light-emitting element 110 includes a light-emitting organic compound that emits red, green, or blue light. Each of the organic layers 112 can also be called an EL layer, and includes at least a layer containing a light-emitting substance (light-emitting layer).

[0144] The organic layer 112 and the common layer 114 can each independently have one or more of an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer. For example, the organic layer 112 can have a stacked structure of a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer from the pixel electrode 111 side, and the common layer 114 can have an electron injection layer.

[0145] The pixel electrode 111 is provided for each light-emitting element. The common electrode 113 and the common layer 114 are provided as a continuous layer common to each light-emitting element. A conductive film that is translucent to visible light is used for either the pixel electrode or the common electrode 113, and a conductive film that is reflective is used for the other. By making each pixel electrode translucent and the common electrode 113 reflective, a bottom-emission display device can be obtained. Conversely, by making each pixel electrode reflective and the common electrode 113 translucent, a top-emission display device can be obtained. Note that by making both the pixel electrodes and the common electrode 113 translucent, a dual-emission display device can also be obtained.

[0146] A protective layer 121 is provided on the common electrode 113 to cover the light emitting elements 110. The protective layer 121 has a function of preventing impurities such as water from diffusing from above into each light emitting element.

[0147] The edge of the pixel electrode 111 preferably has a tapered shape. When the edge of the pixel electrode 111 has a tapered shape, the organic layer 112 provided along the edge of the pixel electrode 111 can also have an inclined portion. By tapering the edge of the pixel electrode 111, the coverage of the organic layer 112 provided over the edge of the pixel electrode 111 can be improved. Furthermore, by tapering the side surface of the pixel electrode 111, foreign matter (for example, also referred to as dust or particles) during the manufacturing process can be easily removed by a process such as cleaning, which is preferable.

[0148] In this specification and the like, the term "tapered shape" refers to a shape in which at least a part of a side surface of a structure is inclined with respect to a substrate surface. For example, it is preferable that the structure has a region in which the angle between the inclined side surface and the substrate surface (also referred to as the taper angle) is less than 90°.

[0149] The organic layer 112 is processed into an island shape using, for example, a resist mask formed by lithography. As a result, the organic layer 112 has a shape in which the angle between the top surface and the side surface at its edge is close to 90 degrees. On the other hand, an organic film formed using FMM (Fine Metal Mask) or the like tends to be gradually thinner as it approaches the edge. For example, the top surface is formed in a sloped shape over a range of 1 μm to 10 μm from the edge, resulting in a shape in which it is difficult to distinguish between the top surface and the side surface.

[0150] Between two adjacent light emitting elements, an insulating layer 124, an insulating layer 125 and a resin layer 126 are provided.

[0151] Between two adjacent light-emitting elements, the side surfaces of the organic layers 112 face each other with the resin layer 126 sandwiched therebetween. The resin layer 126 is located between the two adjacent light-emitting elements and is provided so as to fill the ends of each organic layer 112 and the region between the two organic layers 112. The resin layer 126 has a smooth, convex upper surface, and a common layer 114 and a common electrode 113 are provided to cover the upper surface of the resin layer 126.

[0152] The resin layer 126 functions as a planarizing film that fills in the step between two adjacent light-emitting elements. By providing the resin layer 126, it is possible to prevent the common electrode 113 from being separated by the step at the end of the organic layer 112 (also called step disconnection), which would otherwise occur and result in insulation of the common electrode on the organic layer 112.

[0153] Furthermore, the resin layer 126 insulates the organic layers 112 of adjacent light-emitting elements 110 from each other. This reduces leakage current between adjacent light-emitting elements via the organic layers 112, thereby suppressing unnecessary light emission due to crosstalk. This improves the color-developing performance of the display device.

[0154] An insulating layer containing an organic material can be suitably used as the resin layer 126. For example, acrylic resin, polyimide resin, epoxy resin, imide resin, polyamide resin, polyimideamide resin, silicone resin, siloxane resin, benzocyclobutene resin, phenolic resin, precursors of these resins, etc. can be used as the resin layer 126. Alternatively, organic materials such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or alcohol-soluble polyamide resin can be used as the resin layer 126.

[0155] Furthermore, a photosensitive resin can be used as the resin layer 126. A photoresist can be used as the photosensitive resin. The photosensitive resin can be a positive-type material or a negative-type material.

[0156] The resin layer 126 may contain a material that absorbs visible light. For example, the resin layer 126 itself may be made of a material that absorbs visible light, or the resin layer 126 may contain a pigment that absorbs visible light. For example, the resin layer 126 may be a resin that can be used as a color filter that transmits red, blue, or green light and absorbs other light, or a resin that contains carbon black as a pigment and functions as a black matrix.

[0157] The resin layer 126 absorbs light emitted from the light emitting element in an oblique direction, thereby suppressing leakage of light (stray light) from the light emitting element to an adjacent light emitting element via the resin layer 126. This improves the display quality of the display device.

[0158] The insulating layer 125 is provided in contact with the side surface of the organic layer 112. The insulating layer 125 is also provided to cover the upper end portion of the organic layer 112.

[0159] The insulating layer 125 is located between the resin layer 126 and the organic layer 112, and functions as a protective film to prevent the resin layer 126 from contacting the organic layer 112. If the organic layer 112 and the resin layer 126 come into contact with each other, the organic layer 112 may be dissolved by an organic solvent or the like used when forming the resin layer 126. Therefore, by providing the insulating layer 125 between the organic layer 112 and the resin layer 126, it is possible to protect the side surfaces of the organic layer 112.

[0160] The insulating layer 125 can be an insulating layer containing an inorganic material. For example, an inorganic insulating film such as an insulating oxide film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used for the insulating layer 125. The insulating layer 125 may have a single-layer structure or a stacked-layer structure. Examples of oxide insulating films include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, an indium gallium zinc oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide film. Examples of nitride insulating films include a silicon nitride film and an aluminum nitride film. Examples of oxynitride insulating films include a silicon oxynitride film and an aluminum oxynitride film. Examples of nitride oxide insulating films include a silicon nitride oxide film and an aluminum nitride oxide film. In particular, by using a metal oxide film such as an aluminum oxide film or a hafnium oxide film formed by an ALD method, or an inorganic insulating film such as a silicon nitride film or a silicon oxide film, as the insulating layer 125, an insulating layer 125 with few pinholes and excellent protection of the EL layer can be formed.

[0161] In this specification and elsewhere, an oxynitride refers to a material whose composition contains more oxygen than nitrogen, and a nitride oxide refers to a material whose composition contains more nitrogen than oxygen. For example, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, and silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0162] The insulating layer 125 can be formed by a sputtering method, a CVD method, a PLD method, an ALD method, or the like. The insulating layer 125 is preferably formed by an ALD method because it has good coverage.

[0163] Furthermore, a reflective film (e.g., a metal film containing one or more selected from silver, palladium, copper, titanium, aluminum, etc.) may be provided between the insulating layer 125 and the resin layer 126, so that the light emitted from the light-emitting layer is reflected by the reflective film, thereby improving the light extraction efficiency.

[0164] The insulating layer 124 is a portion of a protective layer (also referred to as a mask layer or a sacrificial layer) that protects the organic layer 112 when the organic layer 112 is etched. The insulating layer 124 can be made of the same material as can be used for the insulating layer 125. In particular, it is preferable to use the same material for the insulating layer 124 and the insulating layer 125 because this allows the use of common processing equipment and the like.

[0165] In particular, metal oxide films such as aluminum oxide films and hafnium oxide films, or inorganic insulating films such as silicon nitride films and silicon oxide films formed by the ALD method have few pinholes and are therefore excellent in the function of protecting the EL layer, and can be suitably used for the insulating layer 125 and the insulating layer 124.

[0166] The protective layer 121 may have, for example, a single-layer structure or a stacked structure including at least an inorganic insulating film. Examples of the inorganic insulating film include oxide films or nitride films such as a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a silicon nitride film, an aluminum oxide film, an aluminum oxynitride film, and a hafnium oxide film. Alternatively, the protective layer 121 may be made of a semiconductor material or a conductive material such as indium gallium oxide, indium zinc oxide, indium tin oxide, or indium gallium zinc oxide.

[0167] An insulating layer 104 is provided over the protective layer 121. The insulating layer 104 functions as a planarization layer. The insulating layer 104 can be formed using, for example, a material that can be used for the resin layer 126 or a material that can be used for the insulating layer 125. Note that the insulating layer 104 may not be provided.

[0168] A lens 102, which is a plano-convex lens, is provided on the insulating layer 104 so as to overlap the light-emitting element 110. An insulating layer 107 is provided on the lens 102. The lens 102 is provided in a pair with the light-emitting element 110. In other words, one lens 102 is provided for each sub-pixel.

[0169] The lens 102 is provided above the light-emitting element 110 (in the direction in which light is emitted). The lens 102 has a convex lens shape, and therefore can act in a direction to converge light. In other words, the divergence of light emitted by the light-emitting element can be suppressed, thereby improving the light extraction efficiency of the display device. The lens 102 can be manufactured using the same material and in the same process as the resin layer 126. Note that a configuration without the lens 102 is also possible.

[0170] The insulating layer 107 provided on the lens 102 is an adhesive layer provided between the lens 102 and the substrate 163, and is preferably made of an organic material. For example, an optical adhesive having a refractive index close to that of the glass or film that can be used as the substrate 163 can be used.

[0171] Although the provision of the lens can improve the efficiency of light extraction from the display panel, it is also effective to use a light-emitting element with higher luminous efficiency in order to improve the front brightness of the display panel. In principle, the brightness of tandem organic EL elements improves depending on the number of layers they are stacked in if the current density is the same, and a two-layer tandem organic EL element can achieve twice the brightness of a single-layer light-emitting element.

[0172] Furthermore, because the lifespan of an organic EL element depends on the current density, even if the brightness of a tandem organic EL element is doubled, the lifespan will be equivalent to that of a single organic EL element if the current density is the same. In other words, tandem organic EL elements are an effective technology for increasing the brightness and reliability of organic EL elements.

[0173] [Display Panel 200B] A display panel 200B shown in FIG. 14 has a stacked structure of a transistor 330 in which a channel is formed in a substrate 301 and a transistor 320 in which a channel is formed and a semiconductor layer containing metal oxide is formed.

[0174] The transistor 330 has a channel formation region in a substrate 301. As the substrate 301, for example, a semiconductor substrate such as a single crystal silicon substrate can be used.

[0175] An insulating layer 261 is provided to cover the transistor 330, and a conductive layer 251 is provided over the insulating layer 261. The conductive layer 251 is connected to one of the source and drain of the transistor 330 through a plug 271 embedded in the insulating layer 261.

[0176] An insulating layer 262 is provided to cover the conductive layer 251, and a conductive layer 252 is provided over the insulating layer 262. The conductive layer 251 and the conductive layer 252 each function as a wiring. An insulating layer 263 and an insulating layer 332 are provided to cover the conductive layer 252, and a transistor 310 and a transistor 320 are provided over the insulating layer 332.

[0177] The transistor 330 can be used as a transistor included in a pixel circuit or a driver circuit (gate driver circuit, source driver circuit) for driving the pixel circuit. The transistor 330 can also be used as a transistor included in various circuits such as an arithmetic circuit or a memory circuit.

[0178] With this configuration, not only pixel circuits but also driving circuits etc. can be formed directly below the light-emitting device, which makes it possible to make the display panel smaller than when driving circuits are provided around the periphery of the display area.

[0179] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0180] Embodiment 3 In this embodiment, an indium oxide film that can be used for a semiconductor layer of a transistor included in a display device of one embodiment of the present invention will be described.

[0181] In this specification and the like, indium oxide having at least a crystalline portion or a crystalline region in a film is referred to as crystalline indium oxide (crystal IO) or crystalline indium oxide (crystalline IO). Examples of crystalline IO or crystalline IO include single-crystalline indium oxide, polycrystalline indium oxide, and microcrystalline indium oxide.

[0182] Indium oxide is a semiconductor material having physical properties that are completely different from those of oxide semiconductors such as In—Ga—Zn oxide (hereinafter also referred to as IGZO) and zinc oxide.

[0183] The carrier concentration dependence of the Hall mobility of indium oxide, silicon, and IGZO will be explained. FIG. 15A shows the carrier concentration dependence of the Hall mobility of silicon (Si) and indium oxide (InO Ｘ ) and FIG. 15B is a schematic diagram showing the carrier concentration dependence of the hole mobility for IGZO.

[0184] First, IGZO tends to exhibit higher hole mobility as the carrier concentration increases, as shown by the arrows in Figure 15B. On the other hand, indium oxide tends to exhibit higher hole mobility as the carrier concentration decreases, as shown by the arrows in Figure 15A (see Non-Patent Document 1). This trend is similar to that of silicon; the lower the dopant (impurity) concentration in the material, the less impurity scattering there is and the higher the hole mobility. In other words, the higher the purity and intrinsic indium oxide, the higher the hole mobility. From these results, it can be said that indium oxide, unlike IGZO, is a material with physical properties similar to those of silicon. Note that the characteristics of indium oxide shown in Figure 15A are assumed to be single crystal. Therefore, when indium oxide is non-single crystal (e.g., polycrystalline), the characteristics may differ from those shown in Figure 15A.

[0185] 15A, the range R1 of low carrier concentration has extremely high hole mobility, and therefore can be said to be a range of carrier concentration suitable for, for example, a channel formation region of a transistor. For example, in the case of indium oxide, the range R1 is a range where the carrier concentration value is 1×10 １５ cm −３ The range includes, for example, 1×10 １４ cm −３ That's it, 1 x 10 １８ cm −３ By sufficiently reducing the carrier concentration, the Hall mobility value can be increased to 270 cm ２ It is expected that the resistance can be increased to about / (V·s).

[0186] In addition, in indium oxide, the region where the carrier concentration is in the range R1 may contain an element that lowers the carrier concentration. Examples of elements that lower the carrier concentration include magnesium, calcium, zinc, cadmium, and copper. By substituting these elements for indium, the carrier concentration can be lowered. Examples of elements that lower the carrier concentration include nitrogen, phosphorus, arsenic, and antimony. For example, by substituting nitrogen, phosphorus, arsenic, or antimony for oxygen, the carrier concentration can be lowered.

[0187] On the other hand, the range R2 with a high carrier concentration has a low electrical resistance, and can be said to be a range of carrier concentrations suitable for, for example, the source and drain regions of a transistor, a resistor, or a transparent conductive film. ２０ cm −３ The range includes, for example, 1×10 １９ cm −３ That's it, 1 x 10 ２２ cm −３ By increasing the carrier concentration sufficiently, the resistivity can be reduced to 1×10 −４ It is expected that the resistivity can be reduced to Ω·cm or less.

[0188] In the indium oxide, the region having a carrier concentration in the range R2 may contain an element that increases the carrier concentration. For example, it is preferable that the indium oxide contains an element that is common to the source electrode and the drain electrode of the transistor. Examples of elements that increase the carrier concentration include titanium, zirconium, hafnium, tantalum, tungsten, molybdenum, tin, silicon, and boron. In particular, it is more preferable to use an element whose oxide has conductive or semiconductive properties.

[0189] In this way, indium oxide uses a region with a low carrier concentration as the channel formation region of a transistor, and a region with a high carrier concentration as the source and drain regions of the transistor. In other words, indium oxide can be said to be an oxide capable of valence electron control. Note that IGZO may experience strain in the source and drain regions due to stress from electrodes in contact with the IGZO, resulting in the formation of n-type regions. On the other hand, unlike IGZO, indium oxide is capable of valence electron control, and therefore does not require strain to be formed in the film as with IGZO. Less strain in the film is expected to improve reliability. For example, by separately creating a region with a carrier concentration in the range R1 shown in FIG. 15A and a region with a carrier concentration in the range R2 in the indium oxide film, a so-called n-i-n junction (a junction between an n-type region, an i-type region, and an n-type region) can be created. Note that valence electron control in transistors using silicon is generally known. On the other hand, valence electron control in transistors using indium oxide is a novel technical concept that would not normally be conceived.

[0190] By using the above technical concept, the transistor having indium oxide in this specification and the like has two or more, preferably three or more, more preferably four or more, and most preferably five of the following characteristics (1) to (5): (1) high on-current (in other words, high mobility); (2) low off-current; (3) normally-off operation; (4) high reliability; and (5) high cutoff frequency (fT). For example, the transistor having indium oxide in this specification and the like has high mobility, low off-current, and is normally-off operation. The transistor has high mobility and is different from a normally-on transistor.

[0191] Next, an indium oxide film applied to a transistor will be described. The indium oxide film preferably has crystallinity (i.e., has crystal grains). Examples of films having crystal grains include single-crystal films, polycrystalline films, and amorphous films containing crystal grains (also called microcrystalline films). In particular, the indium oxide film is preferably a polycrystalline film, and more preferably a single-crystal film. A single-crystal film does not have grain boundaries. Impurities (typically, insulating impurities, insulating oxides, etc.) that hinder carrier flow tend to segregate at grain boundaries. The use of a single-crystal film can suppress carrier scattering at grain boundaries, thereby realizing a transistor exhibiting high field-effect mobility. Furthermore, the use of a single-crystal film has the excellent effect of suppressing variations in transistor characteristics due to the grain boundaries.

[0192] Furthermore, polycrystalline films are preferable because they can reduce carrier scattering and exhibit high field-effect mobility compared to microcrystalline or amorphous films. When using a polycrystalline film, it is preferable to use a film with as large a crystal grain size as possible and with few crystal grain boundaries. Note that in a transistor using an indium oxide polycrystalline film, if there is no crystal grain boundary in the channel formation region or no crystal grain boundary is observed, the channel formation region is located within a single crystal region included in the polycrystalline film, and therefore the transistor can be considered to be using single-crystal indium oxide.

[0193] The crystallinity of indium oxide can be analyzed by, for example, X-ray diffraction (XRD), transmission electron microscope (TEM), or electron diffraction (ED). Alternatively, a combination of these methods may be used for analysis.

[0194] In this specification and the like, a semiconductor layer in which no crystal grain boundary is observed in the channel formation region, a semiconductor layer in which the channel formation region is included in one crystal grain, or a semiconductor layer in which the crystal axis direction is the same in at least two regions in the channel formation region can be called a single crystal film. Also, a semiconductor layer in which, in the channel formation region, within one crystal grain, the direction of another crystal axis continuously changes around a certain crystal axis or a certain crystal orientation as the axis of rotation can be called a single crystal film.

[0195] The channel formation region refers to a region of the semiconductor layer that overlaps (or faces) the gate electrode via the gate insulating layer, and is located between the region in contact with the source electrode and the region in contact with the drain electrode. The current path in the channel formation region is the shortest distance between the source electrode and the drain electrode. Therefore, the crystal grains, crystal grain boundaries, crystal axes, crystal orientation, etc. in the channel formation region can be confirmed by observing a cross section including the semiconductor layer, the source electrode, and the drain electrode.

[0196] The indium oxide film in the channel formation region preferably has a lower impurity concentration. Impurities in the indium oxide film in the channel formation region can be a scattering source of carriers, which can lead to a decrease in field-effect mobility. These impurities can also hinder the crystal growth of the indium oxide film. Examples of impurities in the indium oxide film include boron and silicon. The indium oxide film preferably contains these impurities at concentrations of 0.1% or less, and more preferably 0.01% (100 ppm) or less. Carbon, hydrogen, and other elements may be contained in the film-forming gas or precursor during film formation, and may remain in the indium oxide film in greater amounts than the above-mentioned impurities.

[0197] The indium oxide film in the channel formation region may contain an element that can become the same trivalent cation as indium, as long as the crystal maintains a cubic crystal structure (bixbyite type). Examples of such an element include Group 13 elements of the periodic table, such as gallium and aluminum, and Group 3 elements of the periodic table. These elements exist mainly as trivalent cations in oxides, and therefore the carrier concentration of indium oxide can be maintained low.

[0198] By using such an indium oxide film in a transistor, the field effect mobility of the transistor can be increased to 50 cm ２ / (V·s) or more, preferably 100 cm ２ / (V·s) or more, more preferably 150 cm ２ / (V·s) or more, more preferably 200 cm ２ / (V·s) or more, more preferably 250 cm ２ / (V·s) or more.

[0199] One of the features of an indium oxide film is that it has higher oxygen permeability (diffusibility) than an IGZO film. As shown in FIG. 15C, an indium oxide film (InO Ｘ Oxygen (O) diffusing into the indium oxide film passes through the indium oxide film and becomes oxygen molecules (O ２ ) and is released as water molecules (H ２ O) may be released in the film. Ｏ In the case where an indium oxide film is present, oxygen atoms diffuse to compensate for the oxygen vacancies. Since oxygen diffuses easily in the indium oxide film, it can be said that oxygen vacancies are more easily compensated for in the indium oxide film than in the IGZO film.

[0200] As described above, an indium oxide film can more easily reduce oxygen vacancies in the film than an IGZO film. Therefore, by using such an indium oxide film in a transistor, a transistor exhibiting extremely high reliability can be realized.

[0201] Furthermore, as shown in FIG. 15C, the indium oxide film diffuses hydrogen. Hydrogen that diffuses into the indium oxide film from the outside passes through the indium oxide film and becomes hydrogen molecules (H ２ ) or reacts with oxygen contained in the membrane and is released as water molecules.

[0202] A transistor using an indium oxide film is an accumulation-type transistor that uses electrons as majority carriers. Assuming that the carrier relaxation time is constant, the smaller the effective mass of the electrons (carriers), the higher the electron mobility. In other words, by using indium oxide, which has a small effective mass of electrons, for a transistor, the on-state current or field-effect mobility of the transistor can be increased.

[0203] Table 1 shows the results of single crystal indium oxide (here, In ２ O ３ ) and single-crystal silicon (Si). As shown in Table 1, indium oxide is characterized by a small effective mass of electrons and a large effective mass of holes. Indium oxide also has the characteristic that the effective mass of electrons is almost independent of the crystal orientation. Therefore, by using crystalline indium oxide in a transistor, a transistor with high field-effect mobility and high frequency characteristics (also called f characteristics) can be realized. Furthermore, since the effective mass of holes is large, a transistor with extremely small off-current can be realized. For example, by applying an indium oxide film to a vertical transistor, the off-current per 1 μm of channel width can be reduced to 1 fA (1×10) in an environment of 125° C. −１５ A) or less, or 1aA (1 x 10 −１８ A) or less, and under room temperature (25°C) conditions, −１８ A) or less, or 1zA (1 x 10 −２１ Furthermore, as shown in Table 1, indium oxide has a smaller effective mass of electrons and a larger effective mass of holes than silicon, and therefore may be able to realize a transistor with higher field-effect mobility and lower off-state current than a Si transistor.

[0204]

[0205] It is preferable to provide a seed layer so as to be in contact with at least a portion of the crystalline indium oxide film. The seed layer is preferably made of a material containing crystals with a small difference in lattice constant (also called lattice mismatch) with indium oxide. This can improve the crystallinity of the indium oxide film. Note that a substrate (e.g., a single-crystal substrate) may be used as one of the layers in contact with at least a portion of the crystalline indium oxide film.

[0206] One method for evaluating the degree of lattice mismatch is to use the value of the lattice mismatch shown below. The lattice mismatch Δa [%] of the crystals of the formed film (here, the indium oxide film) with respect to the crystals of the seed layer is expressed as Δa = ((L １ -L ２ ) / L ２ ) × 100, where L １ is the length or lattice constant of the unit lattice vector of the crystal of the formed film, and L ２ is the length of the unit cell vector or the lattice constant of the crystal of the seed layer.

[0207] The smaller the absolute value of the lattice mismatch Δa between the seed layer and the indium oxide film, the more preferable, and it is most preferably 0. For example, Δa can be set to −5% or more and 5% or less, preferably −4% or more and 4% or less, more preferably −3% or more and 3% or less, and even more preferably −2% or more and 2% or less.

[0208] Here, the indium oxide crystal has a cubic crystal structure (bixbyite type). For example, the crystal of yttria-stabilized zirconia (YSZ) can have a cubic crystal structure (fluorite type). The lattice mismatch of the indium oxide crystal with the cubic YSZ crystal is in the range of −2% to 2%, and a single crystal film of indium oxide can be epitaxially grown on the YSZ substrate.

[0209] It should be noted that the crystal structure of the seed layer and the crystal structure of the indium oxide film may not necessarily have the same crystal system or crystal orientation. For example, a film having crystals of a hexagonal or trigonal structure may be used under an indium oxide film having crystals of a cubic structure. For example, by setting the crystal orientation of the surface of the seed layer to

[001] and the crystal orientation of the underside of the indium oxide film to

[111] , the requirements related to the crystal orientation necessary for epitaxial growth can be satisfied. Examples of hexagonal or trigonal crystals include wurtzite structure, YbFe ２ O ４ Type structure, Yb ２ Fe ３ O ７ YbFeFe alloys have the following structures: ２ O ４ Type structure or Yb ２ Fe ３ O ７ An example of a crystal having a ZnO-type structure is IGZO.

[0210] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0211] Embodiment 4 In this embodiment, electronic devices of one embodiment of the present invention will be described with reference to FIGS.

[0212] The electronic devices of this embodiment include the display device of one embodiment of the present invention in their display portions. The display device of one embodiment of the present invention can easily achieve high definition and high resolution. Therefore, the display device of one embodiment of the present invention can be used in the display portions of various electronic devices.

[0213] Examples of electronic devices include electronic devices with relatively large screens such as television sets, desktop or notebook personal computers, computer monitors, digital signage, large game machines such as pachinko machines, as well as digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, personal digital assistants, and sound playback devices.

[0214] The electronic device 6500 shown in FIG. 16A is a portable information terminal that can be used as a smartphone.

[0215] The electronic device 6500 includes a housing 6501, a display portion 6502, a power button 6503, a button 6504, a speaker 6505, a microphone 6506, a camera 6507, a light source 6508, and the like. The display portion 6502 has a touch panel function.

[0216] The display device of one embodiment of the present invention can be applied to the display portion 6502. The display device of one embodiment of the present invention uses light for writing an image, and therefore, circuits can operate at high speed, and can operate with a high frame frequency and low power consumption even when the display device has high definition and high resolution.

[0217] FIG. 16B is a schematic cross-sectional view including the end of the housing 6501 on the microphone 6506 side.

[0218] A light-transmitting protective member 6510 is provided on the display surface side of the housing 6501, and a display panel 6511, optical members 6512, a touch sensor panel 6513, a printed circuit board 6517, a battery 6518, etc. are arranged in the space surrounded by the housing 6501 and the protective member 6510.

[0219] A display panel 6511, an optical member 6512, and a touch sensor panel 6513 are fixed to the protective member 6510 with an adhesive layer (not shown). The function of the touch sensor panel can also be performed by a light-receiving device included in the display device of one embodiment of the present invention. The light-receiving device included in the display device of one embodiment of the present invention detects light through a lens, has high light sensitivity, and is excellent in the ability to detect a touch position. In addition, the light-receiving device can also acquire an image for fingerprint authentication.

[0220] In a region outside the display portion 6502, a part of the display panel 6511 is folded back, and an FPC 6515 is connected to the folded back part. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to a terminal provided on a printed circuit board 6517.

[0221] 16C shows an example of a television set. A television set 7100 has a display portion 7000 built into a housing 7101. Here, the housing 7101 is supported by a stand 7103.

[0222] The display device of one embodiment of the present invention can be applied to the display portion 7000. The display device of one embodiment of the present invention uses light for writing an image, and therefore, circuits can operate at high speed, and can operate with a high frame frequency and low power consumption even when the display device has high definition and high resolution.

[0223] 16C can be operated using operation switches provided on the housing 7101 and a separate remote control 7111. Alternatively, the display portion 7000 may be provided with a touch sensor, and the television set 7100 may be operated by touching the display portion 7000 with a finger or the like. The remote control 7111 may have a display portion that displays information output from the remote control 7111. Using operation keys or a touch panel provided on the remote control 7111, the channel and volume can be controlled, and an image displayed on the display portion 7000 can be controlled.

[0224] The television device 7100 includes a receiver and a communication device. The receiver can receive general television broadcasts. By connecting to a wired or wireless communication network via the communication device, one-way (from a sender to a receiver) or two-way (between a sender and a receiver, or between receivers) information communication can be performed.

[0225] 16D shows an example of a laptop personal computer 7200. The laptop personal computer 7200 includes a housing 7211, a keyboard 7212, a pointing device 7213, an external connection port 7214, and the like. A display portion 7000 is incorporated in the housing 7211.

[0226] The display device of one embodiment of the present invention can be applied to the display portion 7000. The display device of one embodiment of the present invention uses light for writing an image, and therefore, circuits can operate at high speed, and can operate with a high frame frequency and low power consumption even when the display device has high definition and high resolution.

[0227] 16E and 16F show an example of digital signage.

[0228] 16E includes a housing 7301, a display portion 7000, and a speaker 7303. The digital signage 7300 may further include an LED lamp, operation keys (including a power switch or an operation switch), a connection terminal, various sensors, a microphone, and the like.

[0229] 16F shows a digital signage 7400 attached to a cylindrical pillar 7401. The digital signage 7400 has a display unit 7000 provided along the curved surface of the pillar 7401.

[0230] In Figures 16E and 16F, the display device of one embodiment of the present invention uses light for writing an image to the display portion 7000. Therefore, the circuit can operate at high speed, and the display device can operate at a high frame frequency and with low power consumption even with high definition and high resolution.

[0231] The larger the display unit 7000, the more information can be provided at one time. Also, the larger the display unit 7000, the more easily it will attract people's attention, which can increase the advertising effectiveness of, for example, advertisements.

[0232] Applying a touch panel to the display unit 7000 is preferable because it not only displays images or videos on the display unit 7000 but also allows the user to intuitively operate it. Furthermore, when used to provide information such as route information or traffic information, the intuitive operation can improve usability.

[0233] 16E and 16F , the digital signage 7300 or the digital signage 7400 is preferably capable of wirelessly linking with an information terminal 7311 or an information terminal 7411 such as a smartphone carried by a user. For example, advertising information displayed on the display unit 7000 can be displayed on the screen of the information terminal 7311 or the information terminal 7411. By operating the information terminal 7311 or the information terminal 7411, the display on the display unit 7000 can be switched.

[0234] Furthermore, the digital signage 7300 or the digital signage 7400 can be made to run a game using the screen of the information terminal 7311 or the information terminal 7411 as an operation means (controller), thereby allowing an unspecified number of users to simultaneously participate in and enjoy the game.

[0235] The electronic device shown in Figures 17A to 17G has a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), a connection terminal 9006, a sensor 9007 (including a function to sense, detect or measure force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared rays), a microphone 9008, etc.

[0236] The electronic devices shown in Figures 17A to 17G have various functions. For example, they may have a function to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date, or time, a function to control processing using various software (programs), a wireless communication function, a function to read and process programs or data recorded on a recording medium, etc. Note that the functions of the electronic devices are not limited to these, and they may have various other functions. The electronic devices may have multiple display units. Furthermore, the electronic devices may have a function to include a camera or the like to capture still images or videos and store them on a recording medium (external or built-in to the camera), a function to display the captured images on a display unit, etc.

[0237] 17A to 17G are described in detail below. Note that the display device of one embodiment of the present invention can be applied to these electronic devices. The display device of one embodiment of the present invention uses light for writing an image, and therefore, circuits can operate at high speed. Therefore, the display device of one embodiment of the present invention can operate at a high frame frequency with low power consumption even when the display device has high definition and high resolution.

[0238] FIG. 17A is a perspective view showing a mobile information terminal 9101. The mobile information terminal 9101 can be used as, for example, a smartphone. Note that the mobile information terminal 9101 may be provided with a speaker 9003, a connection terminal 9006, a sensor 9007, and the like. The mobile information terminal 9101 can display text and image information on multiple surfaces. FIG. 17A shows an example in which three icons 9050 are displayed. Information 9051, indicated by a dashed rectangle, can also be displayed on another surface of the display unit 9001. Examples of the information 9051 include notifications of incoming emails, SNS messages, phone calls, etc., the title of the email or SNS message, the sender's name, the date and time, the remaining battery level, and radio wave intensity. Alternatively, an icon 9050 or the like may be displayed in the position where the information 9051 is displayed.

[0239] 17B is a perspective view showing the mobile information terminal 9102. The mobile information terminal 9102 has a function of displaying information on three or more surfaces of the display unit 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different surfaces. A user can check information 9053 displayed in a position that can be observed from above the mobile information terminal 9102 while the mobile information terminal 9102 is placed in a breast pocket of clothes. The user can check the display and decide whether to answer a call without taking the mobile information terminal 9102 out of the pocket.

[0240] 17C is a perspective view showing a tablet terminal 9103. The tablet terminal 9103 is capable of executing various applications such as mobile phone calls, e-mail, text browsing and creation, music playback, internet communication, and computer games, for example. The tablet terminal 9103 has a display unit 9001, a camera 9002, a microphone 9008, and a speaker 9003 on the front side of a housing 9000, operation keys 9005 as operation buttons on the left side of the housing 9000, and a connection terminal 9006 on the bottom.

[0241] 17D is a perspective view showing a wristwatch-type mobile information terminal 9200. The mobile information terminal 9200 can be used as, for example, a smart watch (registered trademark). The display surface of the display unit 9001 is curved, and display can be performed along the curved display surface. The mobile information terminal 9200 can also perform hands-free calling by communicating with a wireless headset. The mobile information terminal 9200 can also perform data transmission and charging with another information terminal through a connection terminal 9006. Note that charging may be performed by wireless power supply.

[0242] 17E to 17G are perspective views showing a foldable mobile information terminal 9201. Also, FIG. 17E is a perspective view of the mobile information terminal 9201 in an unfolded state, FIG. 17G is a perspective view of the mobile information terminal 9201 in a folded state, and FIG. 17F is a perspective view of a state in the process of changing from one of FIGS. 17E and 17G to the other. The mobile information terminal 9201 is highly portable when folded, and has a seamless, wide display area when unfolded, providing excellent visibility of the display. The display portion 9001 of the mobile information terminal 9201 is supported by three housings 9000 connected by hinges 9055. For example, the display portion 9001 can be bent with a curvature radius of 0.1 mm or more and 150 mm or less.

[0243] 18A is a diagram illustrating an example of a glasses-type device including a display device and an optical device according to one embodiment of the present invention. Here, a combination of a display device 70 and an optical device 71 is indicated by a dashed line as a display unit 60. FIG. 18C is a diagram illustrating elements of the display unit 60. The display device according to one embodiment of the present invention uses light for writing an image, and therefore, circuits can operate at high speed, and can operate at a high frame frequency and with low power consumption even with high definition and high resolution.

[0244] The user can view the image displayed on the display device 70 by bringing their eyes close to the optical device 71 provided on the display surface side of the display device 70. The user can view the image with the viewing angle widened by the optical device 71, which gives the user a sense of immersion and realism.

[0245] A linear polarizer 62 and a retardation film 63 can be attached to the display surface of the display device 70. The optical device 71 can have a configuration including, for example, a half mirror 64, a lens 65, a retardation film 66, a reflective polarizer 67, and a lens 68.

[0246] The optical device 71 converts the light emitted by the display device 70 into linearly polarized light or circularly polarized light and uses it to selectively reflect or transmit light at elements arranged on the optical path. This allows the optical path length to be secured within a limited space, and the focal length of the optical device to be shortened. This type of optical system is called a catadioptric system. It is also sometimes called a pancake lens due to its thin shape.

[0247] The two display units 60 are incorporated into the housing 90 so that the surfaces of the lenses 68 are exposed on the inside. One display unit 60 is for the right eye, and the other display unit 60 is for the left eye, and by displaying images corresponding to the parallax on each display unit 60, the user can feel the three-dimensionality of the image.

[0248] Furthermore, the housing 90 or the holder 95 may be provided with an input terminal and an output terminal. The input terminal can be connected to a cable for supplying a video signal from a video output device or the like, or power for charging the battery. The output terminal, for example, functions as an audio output terminal and can be connected to earphones, headphones, or the like. Note that if the device is configured to be able to output audio data via wireless communication or if audio is output from an external video output device, the audio output terminal need not be provided.

[0249] Furthermore, a wireless communication module and a storage module may be provided inside the housing 90 or the holder 95. The wireless communication module performs wireless communication, and the content to be viewed can be downloaded and stored in the storage module. This allows the user to view the downloaded content offline.

[0250] As shown in FIG. 18B , a line-of-sight detection sensor 91 may be provided within the housing 90. The line-of-sight detection sensor 91 detects the position of the gaze by detecting changes in the reflected light due to iris movement using light emitted from a light source 92 provided within the housing 90. The light emitted by the light source 92 is preferably near-infrared light, which has extremely low visibility. For example, operation buttons such as power on, power off, sleep, volume adjustment, channel change, menu display, selection, decision, and back, as well as operation buttons such as video play, stop, pause, fast forward, and fast rewind, may be displayed, and the respective operations can be performed by visually recognizing the operation buttons. Furthermore, the user's level of fatigue may be detected based on the number of blinks, and an alert may be displayed.

[0251] By using the display device of one embodiment of the present invention for a glasses-type device, the electronic device can have low power consumption and high reliability.

[0252] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0253] AL: wiring, CL: wiring, CLK[1]: clock signal, CLK[2]: clock signal, GL: wiring, IData: current, LC: liquid crystal element, LIN: signal input unit, OWG

[0001] : waveguide, OWG: waveguide, RIN: signal input unit, RL: wiring, SL: wiring, SOUT: output line, SR: shift register circuit, VData: data potential,

[2560] : waveguide, 10: circuit block, 11: pixel, 12: pixel array, 20: gate driver circuit, 25: light source, 25L: lens, 26: switch, 30: source driver circuit, 41: light incident unit, 42: light emitting output portion, 43: layer, 44: layer, 51: semiconductor layer, 52: conductive layer, 53: conductive layer, 55: insulating layer, 56: insulating layer, 57: insulating layer, 60: display unit, 62: linear polarizer, 63: retardation plate, 64: half mirror, 65: lens, 66: retardation plate, 67: reflective polarizer, 68: lens, 70: display device, 71: optical device, 90: housing, 91: line of sight detection sensor, 92: light source, 95: holder, 102: lens, 104: insulating layer, 107: insulating layer, 110: light emitting element, 111: pixel electrode, 112: organic layer, 113: common electrode, 114: common layer, 121: protective layer, 124: Insulating layer, 125: insulating layer, 126: resin layer, 163: substrate, 200A: display panel, 200B: display panel, 240: capacitor, 241: conductive layer, 243: insulating layer, 245: conductive layer, 251: conductive layer, 252: conductive layer, 254: insulating layer, 255a: insulating layer, 255b: insulating layer, 255c: insulating layer, 256: plug, 261: insulating layer, 262: insulating layer, 263: insulating layer, 264: insulating layer, 265: insulating layer, 267: insulating layer, 271: plug, 274: plug, 274a: conductive layer, 274b: conductive layer, 280: display module, 281: display unit, 290: FPC , 291: substrate, 292: substrate, 301: substrate, 310: transistor, 320: transistor, 321: semiconductor layer, 323: insulating layer, 324: conductive layer, 325: conductive layer, 326: insulating layer, 327: conductive layer, 328: insulating layer, 329: insulating layer, 330: transistor, 331: substrate, 332: insulating layer, 6500: electronic device, 6501: housing, 6502: display unit, 6503: power button, 6504: button, 6505: speaker, 6506: microphone, 6507: camera, 6508: light source, 6510: protective member, 6511: display panel, 6512: optical member,6513: Touch sensor panel, 6515: FPC, 6516: IC, 6517: Printed circuit board, 6518: Battery, 7000: Display unit, 7100: Television device, 7101: Housing, 7103: Stand, 7111: Remote control device, 7200: Notebook personal computer, 7211: Housing, 7212: Keyboard, 7213: Pointing device, 7214: External connection port, 7300: Digital signage, 7301: Housing, 7303: Speaker, 7311: Information terminal device, 7400: Digital signage, 7401: Pillar, 7411: Information terminal, 9000: Housing, 9001: Display unit, 9002: Camera, 9003: Speaker, 9005: Operation keys, 9006: Connection terminal, 9007: Sensor, 9008: Microphone, 9050: Icon, 9051: Information, 9052: Information, 9053: Information, 9054: Information, 9055: Hinge, 9101: Portable information terminal, 9102: Portable information terminal, 9103: Tablet terminal, 9200: Portable information terminal, 9201: Portable information terminal,

Claims

a gate driver circuit, a source driver circuit, a light source, a pixel, a first wiring, and a second wiring; the pixel includes a first transistor; the light source is a diode-type light source; an anode of the light source connected to the gate driver circuit; a cathode of the light source connected to the first wiring; the second wiring is connected to the source driver circuit and one of the source and the drain of the first transistor; the first wiring has a region overlapping with a semiconductor layer of the first transistor via an insulating layer; the first wiring has a light-transmitting conductive layer, The light-transmitting conductive layer functions as a waveguide for light emitted from the light source and irradiated onto the semiconductor layer of the first transistor, and also functions as a gate electrode of the first transistor. 　 In claim 1, The first wiring has a function of supplying a fixed potential. a gate driver circuit, a source driver circuit, a light source, a pixel, a first wiring, a second wiring, a third wiring, and a waveguide; the pixel includes a first transistor; the light source is a diode-type light source; an anode of the light source connected to the gate driver circuit; a cathode of the light source connected to the first wiring; the second wiring is connected to the source driver circuit and one of the source and the drain of the first transistor; the third wiring and the waveguide have an overlapping region with a semiconductor layer of the first transistor interposed therebetween; a first insulating layer between the third wiring and the semiconductor layer; a second insulating layer between the waveguide and the semiconductor layer; the waveguide functions as an optical path for light emitted from the light source and irradiated onto a semiconductor layer of the first transistor; The third wiring functions as a gate electrode of the first transistor. 　 In claim 3, The display device has a function of supplying a fixed potential to each of the first wiring and the third wiring. 　 In any one of claims 1 to 4, A display device in which the light emitted from the light source is blue light or light with a wavelength shorter than that of blue light. 　 In any one of claims 1 to 4, the pixel includes a second transistor, a capacitor, and a light-emitting element; one electrode of the capacitance element is connected to the other of the source or the drain of the first transistor and the gate of the second transistor; The other electrode of the capacitor element is connected to one of the source and drain of the second transistor and the anode of the light-emitting element. 　 In claim 6, A display device, wherein each of the first transistor and the second transistor has a metal oxide in a channel formation region. 　 In claim 7, The display device, wherein the metal oxide is indium oxide. 　 A transistor included in a pixel and configured to control writing of data, When a potential lower than that of the source is supplied to the gate of the transistor and light is irradiated onto the semiconductor layer of the transistor, A method for operating a display device in which data is written to the pixel by a current flowing through the transistor. 　 An electronic device comprising the display device according to claim 1 and a catadioptric system.

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