Electronic device

Abstract

A purpose of one embodiment of the present invention is to provide a novel display device or display system. A purpose of another embodiment of the present invention is to provide a display device or display system which is able to be produced at a low cost, while being capable of offering various functions to the users. According to the present invention, a pixel comprises light emitting elements having different emission colors, a light emitting element IR, a light receiving element PS, and an infrared light sensor IRS. Photographing of an ocular fundus is performed by taking an image of the ocular fundus by means of the light receiving element IRS, while using a light emitting element, which emits infrared light, as a light source. A substrate for a display panel is produced using a single crystal Si substrate which is able to be micromachined and highly integrated.

Description

electronic equipment

[0001] BACKGROUND OF THE INVENTION 1. Field of the Invention One embodiment of the present invention particularly relates to an electronic device and a display system utilizing an organic electroluminescence (hereinafter also referred to as EL) phenomenon.

[0002] In this specification, the term "semiconductor device" refers to any device that can function by utilizing semiconductor characteristics, and electro-optical devices, semiconductor circuits, and electronic devices are all included in the category of semiconductor devices.

[0003] A variety of display devices are available on the market, ranging from large display devices such as television sets to small display devices such as wristwatches. In recent years, information terminal devices such as mobile phones such as smartphones, tablet information terminals, and notebook PCs (personal computers) have become widely used. In addition, head-mounted or eyeglass-type display devices have also been developed (see Patent Document 1).

[0004] Furthermore, light-emitting elements utilizing the EL phenomenon are known. These light-emitting elements are self-luminous, and therefore have high contrast and a fast response speed to input signals. Display devices that utilize these light-emitting elements are known, which have reduced power consumption, simple manufacturing processes, and can easily accommodate higher definition and larger substrates (Patent Document 2).

[0005] JP 2016-110117 A JP 2011-238908 A

[0006] An object of one embodiment of the present invention is to provide a novel display device or display system. Another object of one embodiment of the present invention is to provide a display device or display system that can be manufactured at low cost and can provide a variety of multifunctions to a user. Another object of one embodiment of the present invention is to provide a display device or display system that can obtain information about the user's eyes.

[0007] The configuration disclosed in this specification is an electronic device that is worn on a user's head, and has a display device that has a transistor, a light-emitting element, and a light-receiving element on the same substrate or on the same substrate, and the display device has a function of displaying an image and a function of capturing an image of the user's fundus.

[0008] In the above-described configuration, the light-emitting element is an organic light-emitting element that emits visible light, and the light emitted by the organic light-emitting element is red, green, blue, or white.

[0009] In the above configuration, the light-emitting element is an organic light-emitting element that emits invisible light, for example, an organic light-emitting element that emits infrared light.

[0010] In each of the above structures, the semiconductor layer of the transistor is made of single crystal silicon. When the semiconductor layer of the transistor is made of single crystal silicon, a single crystal Si substrate is used and a low resistance region is formed by doping an n-type or p-type impurity element using a known method.

[0011] In each of the above structures, an oxide semiconductor is used for the semiconductor layer of the transistor. In the case where the oxide semiconductor is used for the semiconductor layer of the transistor, the oxide semiconductor is formed over a substrate by a sputtering method.

[0012] In each of the above configurations, the electronic device has a light-emitting element and a light-receiving element, and can obtain a fundus image by picking up an image of the user's eye, thereby making a diagnosis.

[0013] In this specification, a device fabricated using a metal mask or an FMM (fine metal mask, high-resolution metal mask) may be referred to as a device with an MM (metal mask) structure. In addition, in this specification, a device fabricated without using a metal mask or an FMM may be referred to as a device with an MML (metal maskless) structure.

[0014] In this specification, a structure in which different light-emitting layers are formed or different light-emitting layers are painted for each color light-emitting device (here, blue (B), green (G), and red (R)) may be referred to as an SBS (Side By Side) structure. In this specification, a light-emitting device that can emit white light may be referred to as a white light-emitting device. In addition, a white light-emitting device can be combined with a colored layer (for example, a color filter) to realize a light-emitting device that displays full color.

[0015] Furthermore, light-emitting devices can be broadly divided into single structures and tandem structures. A single-structure device has one light-emitting unit between a pair of electrodes, and the light-emitting unit preferably includes one or more light-emitting layers. To obtain white light emission, two or more light-emitting layers may be selected so that the light emitted from each of the two or more light-emitting layers has a complementary color relationship. For example, by making the emission color of the first light-emitting layer and the emission color of the second light-emitting layer complementary, a configuration in which the entire light-emitting device emits white light can be obtained. The same applies to light-emitting devices having three or more light-emitting layers.

[0016] A tandem-structure device preferably has two or more light-emitting units between a pair of electrodes, and each light-emitting unit preferably includes one or more light-emitting layers. To obtain white light emission, light from the light-emitting layers of the light-emitting units may be combined to obtain white light emission. The configuration for obtaining white light emission is the same as that of the single-structure device. In a tandem-structure device, it is preferable to provide an intermediate layer of a charge-generating layer between the light-emitting units.

[0017] Furthermore, when comparing the above-described white light-emitting device (single structure or tandem structure) with a light-emitting device having an SBS structure, the light-emitting device having an SBS structure can reduce power consumption compared to the white light-emitting device. When it is desired to reduce power consumption, it is preferable to use a light-emitting device having an SBS structure. On the other hand, the manufacturing process of a white light-emitting device is simpler than that of a light-emitting device having an SBS structure, and therefore the manufacturing cost can be reduced or the manufacturing yield can be increased, making it preferable.

[0018] According to one embodiment of the present invention, an electronic device capable of accurately recognizing information about a user's eyes can be provided. Alternatively, according to one embodiment of the present invention, a novel electronic device can be provided.

[0019] FIG. 1A is a conceptual cross-sectional view of a display device and an eye illustrating one embodiment of the present invention, FIG. 1B is a schematic diagram illustrating a retinal pattern, and FIG. 1C is a perspective view of a display panel. FIG. 2A is a perspective view of a display panel illustrating one embodiment of the present invention, and FIGS. 2B and 2C are schematic top views illustrating an example of a pixel arrangement. FIG. 3A is a schematic cross-sectional view illustrating one embodiment of the present invention, and FIGS. 3B and 3C are schematic external views of an electronic device. FIGS. 4A, 4B, and 4C are schematic cross-sectional views of a display panel illustrating one embodiment of the present invention. FIGS. 5A, 5B, and 5C are schematic diagrams of a display panel illustrating one embodiment of the present invention. FIG. 6 is a perspective view of an electronic device illustrating one embodiment of the present invention. FIG. 7A is a top view illustrating an example of a pixel arrangement illustrating one embodiment of the present invention, and FIG. 7B is a schematic cross-sectional view of a display panel. FIG. 8 is a schematic top view illustrating one embodiment of the present invention. FIG. 9 is a cross-sectional view illustrating a structural example of a semiconductor device. FIG. 10 is a cross-sectional view illustrating a structural example of a semiconductor device. FIG. 11 is a cross-sectional view illustrating a structural example of a semiconductor device. FIG. 12 is a cross-sectional view showing a configuration example of a semiconductor device. FIG. 13 is a cross-sectional view showing a configuration example of a semiconductor device. FIG. 14 is a cross-sectional view showing a configuration example of a semiconductor device. FIGS. 15A to 15D are views explaining a configuration example of a light-emitting element. FIGS. 16A to 16D are views explaining a configuration example of a display device. FIGS. 17A to 17D are views explaining a configuration example of a display device. FIG. 18A is a top view showing a configuration example of a transistor. FIGS. 18B and 18C are cross-sectional views showing configuration examples of a transistor. FIG. 19A is a view explaining classification of IGZO crystal structures. FIG. 19B is a view explaining an XRD spectrum of a CAAC-IGZO film. FIG. 19C is a view explaining a microelectron beam diffraction pattern of a CAAC-IGZO film.

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various modifications can be made to the embodiments and details. Furthermore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0021] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and repeated explanations thereof will be omitted. In addition, when referring to similar functions, the same hatch pattern may be used and no particular reference numeral may be assigned.

[0022] In the drawings described in this specification, the size of each component, the thickness of a layer, or an area may be exaggerated for clarity, and therefore, the drawings are not necessarily limited to the scale.

[0023] In this specification, the ordinal numbers "first" and "second" are used to avoid confusion of components and are not intended to limit the number.

[0024] Furthermore, in this specification, the terms "above," "below," "to the left," and "to the right" indicating the position of components are used for convenience in describing the positional relationship between components with reference to the drawings. Furthermore, the positional relationship between components changes as appropriate depending on the direction in which each component is depicted. Therefore, the terms are not limited to those described in the specification, and can be rephrased appropriately depending on the situation.

[0025] A transistor is a type of semiconductor element that can perform a switching operation to control current or voltage amplification, conduction, or non-conduction. The term "transistor" as used herein includes an insulated gate field effect transistor (IGFET) or a thin film transistor (TFT).

[0026] In this specification, the functions of the source and drain of a transistor may be interchanged when the polarity of the transistor or the direction of current flow changes during circuit operation, and therefore the terms source and drain may be used interchangeably.

[0027] Furthermore, in this specification, "electrically connected" includes both direct connection and connection via "something that has some kind of electrical action." Here, "something that has some kind of electrical action" is not particularly limited as long as it allows for the exchange of electrical signals between the connected objects. Therefore, even when the expression "electrically connected" is used, in an actual circuit, there may be no physical connection and only an extending wiring. Furthermore, even when the expression "directly connected" is used, it also includes cases where different conductors are connected via contacts. Note that in wiring, there are cases where different conductors contain one or more of the same elements and cases where they contain different elements.

[0028] In this specification, unless otherwise specified, the off-state current refers to the drain current when a transistor is in an off state (also referred to as a non-conducting state or a cut-off state). Unless otherwise specified, the off-state current refers to the drain current when a transistor is in an off state (also referred to as a non-conducting state or a cut-off state) when a voltage V between the gate and the source of an n-channel transistor is applied. ｇｓ is the threshold voltage V ｔｈ (For p-channel transistors, V ｔｈ This refers to a state of being (higher than)

[0029] Furthermore, the terms "electrode" and "wiring" used in this specification do not limit the functionality of these components. For example, an "electrode" may be used as part of a "wiring," and vice versa. Furthermore, the terms "electrode" and "wiring" also include cases where multiple "electrodes" or "wirings" are integrally formed.

[0030] In this specification, the resistance value of a "resistor" may be determined by the length of the wiring, or by connecting a conductor having a different resistivity from the conductor used in the wiring, or by doping an impurity into a semiconductor.

[0031] In this specification, the term "terminal" in an electric circuit refers to a portion where a current or voltage is input or output, or a signal is received or transmitted. Therefore, a part of a wiring or an electrode may function as a terminal.

[0032] In this specification, metal oxide refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), and oxide semiconductors (also referred to as oxide semiconductors or simply as OS). For example, when a metal oxide is used in an active layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. In other words, an OS FET can be rephrased as a transistor including a metal oxide or an oxide semiconductor.

[0033] Embodiment 1 In this embodiment, an electronic device of one embodiment of the present invention will be described with reference to drawings.

[0034] FIG. 1A is a schematic diagram showing the positional relationship between the display panel 280 and the user's eyes. The display panel 280 has multiple light-emitting elements and multiple light-receiving elements. Light 951 from the light-emitting elements of the display panel 280 is irradiated onto the eye via the optical system 950, and the reflected light is received by the light-receiving elements to capture images of the periphery of the eye, the surface of the eye, or the interior of the eye (fundus). For example, because the display panel 280 shown in FIG. 1A has light-emitting elements and light-receiving elements, it is possible to capture an image of the fundus via the optical system 950 and obtain image data of the retinal pattern. However, adjusting the focus of the optical system 950 makes it difficult to capture images of other areas. For example, when focusing on the fundus, the periphery of the eye is out of focus, making it almost impossible to capture an image.

[0035] The user's eye is composed of a lens 942, a retina 941, an optic nerve 943, a vitreous body 947, a choroid 948, and a cornea. The pupil is located between the cornea and the lens, but for simplicity, the cornea and pupil are not shown. The ciliary body is a tissue that continues from the iris, and the choroid 948 is a tissue that continues from the ciliary body. The iris and pupil function like a camera aperture to adjust the light that is irradiated onto the retina 941. The pattern of the retina 941, known as the retinal pattern, is said to basically remain unchanged from birth to death, and personal authentication can be performed using the retinal pattern. The retinal pattern obtained on the display panel 280 can be used to perform eye diagnoses even in remote locations.

[0036] FIG. 1B shows an example of the obtained retinal pattern for a right eye. In the retina 941, an optic disc 944, a vein 945, an artery 946, a macula, and a fovea can be observed. The optic disc 944 refers to the boundary between the optic nerve 943 and the retina 941, and the vein 945 and the artery 946 are arranged to extend from the optic disc 944. The fundus refers to the part behind the eyeball and is a collective term for the retina 941, vitreous body 947, choroid 948, and optic disc 944. In the case of a left eye, the optic disc 944 is located on the left side of the retinal pattern, resulting in a retinal pattern that is a left-right inversion of the retinal pattern for the right eye in FIG. 1B.

[0037] In order to capture the retinal pattern of the fundus using the light receiving elements of the display panel 280, the pupil needs to be dilated. To dilate the pupil and capture an image of the fundus, the display is changed in the following procedure: The display screen of the display panel 280 is gradually darkened to allow the user's eyes to adapt to the dark. The display screen is brightened for a short period of time, less than 16.7 ms, and then the image is captured. After that, the display screen is gradually returned to its original brightness.

[0038] The degree of eye fatigue of the user can also be detected using the display panel 280. When capturing an image with the display screen brightened for a certain period of time, if the user blinks, the image cannot be captured. Therefore, by detecting the number of blinks, the timing, or the length of time the eyes are closed, the degree of eye fatigue can be estimated using a system that utilizes AI (Artificial Intelligence) from the frequency of blinks, the interval between blinks, or the length of time the eyes are closed.

[0039] Alternatively, multiple images may be captured while the display screen of the display panel 280 is dark. By capturing multiple images, the pulsation of retinal blood vessels can be detected, and a system utilizing AI can be used to determine whether the user is in a relaxed or stressed state. Furthermore, a system utilizing AI can also be used to diagnose high blood pressure or diabetes using various data obtained by the display panel 280. When a system utilizing AI is used, a control circuit is mounted on the display panel 280. The control circuit uses a CPU (Central Processor Unit) or a GPU (Graphics Processing Unit). The control circuit can also use an APU (Accelerated Processing Unit), which is a chip that integrates a CPU and a GPU. An IC incorporating an AI system (also called an inference chip) may also be used. An IC incorporating an AI system is sometimes called a circuit (microprocessor) that performs neural network calculations.

[0040] Furthermore, while the display screen of the display panel 280 is darkened, an eye-catching pattern may be displayed on the display screen of the display panel 280 to control the orientation of the eyeballs.

[0041] The distance between the display panel 280 and the surface of the eye (for example, the cornea) is preferably about 2 cm or less. To achieve this positional relationship, an optical system 950 with a short focal length is placed between the display panel 280 and the eye.

[0042] When the screen is enlarged by 10 times using the optical system 950, for example, when the display screen size of the display panel 280 is approximately 1 inch diagonally, the sensor pixel pitch is approximately 10.4 μm, but the blood vessel diameter of each of the retinal veins 945 and arteries 946 is smaller than approximately 100 μm, so images can be captured.

[0043] 1C shows a perspective view of the display panel 280. The display panel 280 includes a display device 400C and an FPC 290. The display panel 280 can also be called a system display.

[0044] The display panel 280 includes a substrate 291 and a substrate 292. The display panel 280 includes a pixel portion 284. The pixel portion 284 is a region that displays an image on the display panel 280, and is a region where light from each pixel provided in the pixel portion 284, which will be described later, can be viewed.

[0045] 2A is a perspective view schematically illustrating the configuration on the substrate 291 side. A circuit portion 282, a pixel circuit portion 283 on the circuit portion 282, and a pixel portion 284 on the pixel circuit portion 283 are stacked on the substrate 291. A terminal portion 285 for connecting to an FPC 290 is provided in a portion of the substrate 291 that does not overlap with the pixel portion 284. The terminal portion 285 and the circuit portion 282 are electrically connected by a wiring portion 286 composed of a plurality of wirings.

[0046] The pixel section 284 has a plurality of periodically arranged pixels 284a. An enlarged view of one pixel 284a is shown on the right side of FIG. 2A . The pixel 284a has light-emitting elements 430a, 430b, and 430c, each emitting a different color, a light-emitting element 430IR, a light-receiving element 430PS, and an infrared light sensor 430IRS. The light-emitting elements 430a, 430b, and 430c are arranged in a stripe pattern as shown in FIG. 2A , but this arrangement is not particularly limited. FIG. 2B also shows an example of the arrangement of the pixel 284a. FIG. 2B shows an example in which a green (G) light-emitting element, a blue (B) light-emitting element, a red (R) light-emitting element, a light-emitting element 430IR, a light-receiving element 430PS, and an infrared light sensor 430IRS are arranged.

[0047] As the light-emitting elements 430a, 430b, 430c and the light-emitting element 430IR, it is preferable to use an EL element typified by an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode). Examples of light-emitting materials contained in the EL elements include fluorescent materials (fluorescent materials), phosphorescent materials (phosphorescent materials), inorganic compounds (quantum dot materials), and materials that exhibit thermally activated delayed fluorescence (thermally activated delayed fluorescence (TADF) materials). Furthermore, an LED typified by a micro LED (light-emitting diode) can also be used as the light-emitting element.

[0048] The light-emitting element 430IR emits invisible light. In this example, the light-emitting element 430IR emits infrared light IR. The light-receiving element 430PS is a photoelectric conversion element that is sensitive to at least the infrared light emitted by the light-emitting element 430IR.

[0049] The light receiving element 430PS may have sensitivity in a wavelength range of, for example, 700 nm to 900 nm. Furthermore, the light receiving element 430PS is preferably sensitive not only to infrared light but also to the light emitted by the light emitting element 430IR and the light emitting elements 430a, 430b, and 430c. When the light receiving element 430PS is sensitive to visible light and infrared light, it is preferably sensitive to, for example, a wavelength range of 500 nm to 1000 nm, a wavelength range of 500 nm to 950 nm, or a wavelength range of 500 nm to 900 nm.

[0050] The light-receiving element 430PS can be, for example, a pn-type or pin-type photodiode. The light-receiving element functions as a photoelectric conversion element that detects light incident on the light-receiving element and generates electric charge. The amount of electric charge generated by the photoelectric conversion element is determined according to the amount of incident light. In particular, it is preferable to use an organic photodiode (OPD: Organic Photo Diode) having a layer containing an organic compound as the light-receiving element 430PS. This allows for the production equipment, manufacturing devices, and materials used for manufacturing the first light-emitting element, the second light-emitting element, and the light-receiving element to be partially common, thereby reducing manufacturing costs. Furthermore, the manufacturing process can be simplified, thereby improving manufacturing yield. Organic photodiodes can be easily made thin, lightweight, and large-area, and have a high degree of freedom in shape and design, making them applicable to a variety of display devices.

[0051] The pixel circuit section 283 has a plurality of pixel circuits 283a arranged periodically.

[0052] One pixel circuit 283a is a circuit that controls the light emission of three light-emitting elements included in one pixel 284a. One pixel circuit 283a may be configured to have three circuits that control the light emission of one light-emitting element. For example, the pixel circuit 283a may be configured to have at least one selection transistor, one current control transistor (drive transistor), and a capacitor for each light-emitting element. In this case, a gate signal is input to the gate of the selection transistor, and a source signal is input to either the source or the drain. This realizes an active matrix display device.

[0053] The circuit portion 282 includes a circuit for driving each pixel circuit 283 a of the pixel circuit portion 283. For example, the circuit portion 282 preferably includes one or both of a gate line driver circuit and a source line driver circuit. In addition, the circuit portion 282 may include at least one of an arithmetic circuit, a memory circuit, a control circuit, and a power supply circuit.

[0054] The FPC 290 functions as wiring for supplying a video signal or a power supply potential from the outside to the circuit portion 282. An IC may be mounted on the FPC 290.

[0055] The display panel 280 can be configured such that one or both of the pixel circuit portion 283 and the circuit portion 282 are stacked below the pixel portion 284, thereby enabling the aperture ratio (effective display area ratio) of the pixel portion 284 to be extremely high. For example, the aperture ratio of the pixel portion 284 can be set to 40% or more and less than 100%, preferably 50% or more and 95% or less, and more preferably 60% or more and 95% or less. Furthermore, the pixels 284a can be arranged at an extremely high density, enabling the resolution of the pixel portion 284 to be extremely high. For example, it is preferable that the pixels 284a be arranged in the pixel portion 284 at a resolution of 2000 ppi or more, preferably 3000 ppi or more, more preferably 5000 ppi or more, and even more preferably 6000 ppi or more, and 20000 ppi or less, or 30000 ppi or less.

[0056] 2C shows an example of a pixel portion 284b that is different from the pixel portion 284a of FIG. 2C shows an example in which a white (W) light-emitting element is provided in addition to a green (G) light-emitting element, a blue (B) light-emitting element, and a red (R) light-emitting element.

[0057] 3A shows an example of a cross-sectional view of an electronic device 80 including a display device of one embodiment of the present invention. FIG. 3C shows an example of the electronic device 80 in the form of glasses, and FIG. 3B shows an example of the electronic device 80 worn by a user. Although not shown in FIG. 3B, the electronic device 80 includes a secondary battery for driving the display panel 280.

[0058] The display panel 280 shown in Fig. 3A corresponds to the cross-sectional structure between the dashed dotted line A1-A2 in Fig. 2B. The electronic device 80 shown in Fig. 3A has the display panel 280 between the housing 103 and the protective member 105. The display panel 280 has a plurality of light-emitting elements and a plurality of light-receiving elements between the substrate 291 and the substrate 292. Here, Figs. 3A and 3B are schematic diagrams explaining the function of the electronic device 80 as a display device and the function of capturing an image of an object (the fundus of the user 81).

[0059] The electronic device 80 uses a light-emitting element 130R that emits red light 951R, a light-emitting element 130G that emits green light 951G, and a light-emitting element 130B that emits blue light 951B for full-color display, and photographs the fundus using a light-emitting element that emits infrared light 951IR as a light source and capturing an image with a light-receiving element IRS.

[0060] The light receiving element PS can receive reflected light or external light, which is RGB, and can detect the brightness around the eye, allowing the user to check whether it is dark before photographing the fundus. If this check is not necessary, the light receiving element PS does not need to be provided.

[0061] An optical system is installed in the area where the light emitting element that emits infrared light 951IR and the light receiving element IRS overlap so that the focus is on the fundus.

[0062] In FIG. 3A , the substrate 291 of the display panel 280 may be a glass substrate or a plastic substrate on which switching elements are formed, and on which organic EL elements (OEL) or light-receiving elements electrically connected to the switching elements are formed. However, it is preferable to fabricate the display panel 280 using a single-crystal Si substrate, which is capable of fine processing and high integration.

[0063] 4A, 4B, and 4C show configuration examples of a display panel 280 mounted on the electronic device 80. Note that Fig. 4A, 4B, and 4C correspond to Fig. 1A, and the same reference numerals are used for the same parts.

[0064] FIG. 4A shows an example in which switching elements using an oxide semiconductor (OS) are formed on a single-crystal Si substrate on which a display panel driver circuit is built, and organic light-emitting diode (OEL) elements are electrically connected to the switching elements. For high-resolution displays, the current flowing through the driver transistor of each pixel is at the nanoampere level, and silicon-based transistors would flow too much current, making OS transistors suitable. Furthermore, for black display, a low off-state current is preferable, and OS transistors with low off-state current are suitable. Furthermore, when using organic EL elements, a breakdown voltage of 10 V or more is desirable, making OS transistors more suitable than silicon-based transistors. Light emission 951 from the organic EL element (OEL) can be used to display an image. Furthermore, by forming a light-emitting element IR emitting infrared light and a light-receiving element OPD on the layer containing the organic EL element, fundus photography can be performed by emitting infrared light and receiving the light reflected by the user's fundus with the OPD. Alternatively, fundus photography may be performed by fabricating a light receiving element on a single crystal Si substrate, emitting infrared light, and receiving the light reflected from the user's fundus with a photodiode containing silicon in the light receiving region.

[0065] 4B shows an example in which two single-crystal Si substrates are bonded together. A first single-crystal Si substrate incorporating a drive circuit or control circuit and a second single-crystal Si substrate incorporating a switching element electrically connected to an organic EL element (OEL) are bonded together using a known technique. A light-receiving element may be incorporated into the second single-crystal Si substrate, and fundus photography may be performed by emitting infrared light and receiving the light reflected by the user's fundus with a photodiode containing silicon in its light-receiving region.

[0066] In Fig. 4B, the outside world is displayed as an image captured by an external camera 91 provided in the electronic device 80 shown in Fig. 3C. Although it is difficult to align the display position in the AR system, it is possible to augment reality by recognizing the image captured by the external camera 91. Furthermore, a battery 92 may be provided in the temples of the glasses in the electronic device 80. The battery 92 has the function of supplying power to the external camera 91 or the display panel 280.

[0067] 4C shows an example in which a single-crystal Si substrate is thinned. The single-crystal Si substrate in FIG. 4C has a light-receiving element and a switching element electrically connected to an organic EL element (OEL) fabricated therein, and a driving circuit or a control circuit is attached externally.

[0068] 4A and 4C, if the single crystal Si substrate is thin, it can also transmit visible light, and therefore it can also be used as an AR type electronic device that transmits external light.

[0069] 5A, 5B, and 5C show examples of variations in size of the display panel 280. Note that although the peripheral shape of the display panel 280 in Fig. 5A, 5B, and 5C is rectangular, this is not particularly limited and may be circular or elliptical.

[0070] FIG. 5A shows an example in which the display panel 280, when attached to the user's head, overlaps only one of the user's eyes, making it a monocular device. Note that, when photographing the fundus of both eyes, two electronic devices, one for the right eye and one for the left eye, are prepared. In FIG. 5A , when a single-crystal Si substrate is used to construct the display panel 280, the small size reduces manufacturing costs. As shown in FIG. 8A , multiple chips can be obtained from a single silicon wafer. For example, when a 12-inch silicon wafer is used and the chip size is 26 mm × 16.5 mm, 142 chips can be obtained from one wafer. A display panel with a screen size of 19.9 mm × 14.9 mm (0.99 inches diagonal) can be fabricated on one chip, with a pixel count of 1920 × 1440 and a resolution of 2449 ppi. Furthermore, when the display panel 280 is attached to the user's head, the entire electronic device can be made lightweight.

[0071] FIG. 5B shows an example of a glasses system in which a display panel 280R for the right eye and a display panel 280L for the left eye are separately provided.

[0072] 5C shows an example in which one display panel 280 overlaps both eyes and has a larger screen area than the other examples. Because the area of ​​display panel 280 is large, there is a wide margin for aligning the eyes, making it possible to accommodate individual differences among users.

[0073] In the examples shown in FIGS. 5A, 5B, and 5C, it is possible to achieve a significant reduction in size and weight compared to conventional ophthalmic diagnostic devices.

[0074] The eye has aberrations, so the image displayed on the display screen is not projected perfectly onto the retina. The brain constructs an image through learning. Conversely, the retinal pattern does not project a clear pattern onto the sensor like a conventional ophthalmic diagnostic device. Furthermore, AI-based systems can be used for authentication or health monitoring.

[0075] When using a system that utilizes AI, the calculation processing may be performed inside the electronic device, the captured image data may be sent externally via a network and calculations may be performed on an external calculation device, or a combination of these may be used.

[0076] When performing part or all of the arithmetic processing inside an electronic device, a control circuit needs to be provided in the single-crystal Si substrate shown in Figures 4A, 4B, and 4C. When performing part of the arithmetic processing, the arithmetic circuit may be formed using a transistor including an oxide semiconductor (OS).

[0077] When transmitting data externally, a data transmission / reception circuit is installed in the electronic device and a system using AI is used.

[0078] It may also be possible to enable short-range communication with a mobile information terminal owned by the user. If the mobile information terminal has downloaded an application that uses an AI-based system, authentication or health monitoring can be performed by exchanging data with the mobile information terminal.

[0079] As an example of health monitoring, eye health monitoring can be performed using the display panel 280.

[0080] The fundus is periodically imaged when the user is wearing an electronic device with a display panel 280. When photographing the fundus, there is a period in which the display is dimmed to allow the user's eyes to adapt to the dark, and since the time during which images cannot be taken is when the user is blinking or when the eyes are closed, data on the number or duration of blinks during that period is acquired and stored. In addition, the user can input the degree of subjective symptoms of eye fatigue when acquiring data to create training data, and eye fatigue or eye abnormalities can be detected using an AI-based system based on the accumulated data.

[0081] 3B shows an example of a glasses-type electronic device 80, but there is no particular limitation as long as it is worn on the head, and the display panel 280 of the electronic device 80 may be mounted on a head-mounted display (HMD) as shown in FIG. 6. The electronic device 80 can also be called a goggle-type electronic device.

[0082] FIG. 6 shows an example in which a display panel 280 that overlaps both eyes is used as shown in FIG. 5C.

[0083] The electronic device 80 includes a housing 31, a display panel 280, a fixture 34, a battery 37, a pair of optical members (optical members 35a and 35b), and a pair of frames (frames 36a and 36b). The battery 37 for driving the electronic device 80 supplies power to each component of the electronic device 80 via a cable built into or connected to the fixture 34. While the battery 37 may be provided in the housing 31, providing the battery 37 in the fixture 34 is preferable because it allows the center of gravity of the electronic device 80 to be positioned rearward, improving the wearing comfort for the user. In addition to the battery 37, a drive circuit for operating the display panel 280 may be provided in the fixture 34 to adjust the center of gravity of the electronic device 80.

[0084] The electronic device 80 is also provided with an opening 32, and optical members 35a and 35b and frames 36a and 36b are provided in contact with the opening 32. The frames 36a and 36b are provided in contact with the side surfaces of the optical members 35a and 35b and surround the optical members 35a and 35b, respectively. The display panel 280 can be provided inside the housing 31.

[0085] The display panel 280 has a function of displaying images. Images displayed on the display panel 280 can be viewed by a user of the electronic device 80 through the optical members 35a and 35b. The display panel 280 preferably has a function of displaying high-definition images. For example, when the size of the display area is 8 inches, the display panel 280 preferably has a function of displaying images with a resolution of 8K / 4K.

[0086] A user of the electronic device 80 can view the image displayed on the display panel 280 through the optical members 35a and 35b. The electronic device 80 can be an electronic device capable of VR display.

[0087] The display panel 280 also has a function of detecting light, and is provided with a light receiving element, which is a photoelectric conversion element.

[0088] Light emitted by the light-emitting elements of the display panel 280 is irradiated onto, for example, the face of the user of the electronic device 80, and the reflected light can be detected by the light-receiving elements of the display panel 280. For example, the display panel 280 can have a function to detect the eyes of the user wearing the electronic device 80 and the condition of the surrounding area. Therefore, the electronic device 80 can have a function to recognize the user's facial expressions and facial features, and can therefore have a function to estimate, for example, the user's fatigue level and emotions. The electronic device 80 can, for example, detect teary eyes, blinking, or gaze.

[0089] The display panel 280 preferably has a light-emitting element, such as an element that emits infrared light or near-infrared light, separate from the light-emitting element for display. In this case, the light-receiving element of the display panel 280 preferably has a function of detecting infrared light or near-infrared light. This allows the electronic device 80 to capture an image of the user's fundus.

[0090] Second Embodiment In this embodiment, an example is shown in which a light emitting diode (LED) is used as the light source 104 instead of an OPD.

[0091] 7A shows an example of a pixel portion 284c that is different from the pixel portion 284a in Fig. 2B. Fig. 7A shows an example in which an infrared light sensor IRS is provided in addition to a green (G) light-emitting element, a blue (B) light-emitting element, and a red (R) light-emitting element.

[0092] The display panel 280 shown in FIG. 7B corresponds to the cross-sectional structure between the dashed dotted line A3-A4 in FIG. 7A . The display panel 280 is located between the housing 103 and the protective member 105. Here, the display panel 280 shown in FIG. 7B functions as a display device and captures an image of an object (the face, iris, or fundus of the user 81). Also, FIGS. 7A and 7B use a light-emitting diode (LED) as the light source 104. FIG. 7B shows an example in which the light source 104 is positioned so as not to overlap with the display panel 280. In this case, light emitted from the light source 104 (951IR) is emitted to the outside of the electronic device via the protective member 105. The display panel 280 has multiple light-emitting devices and multiple light-receiving devices between the substrate 106 and the substrate 102. The subpixel (R) has a light-emitting device 130R that emits red light 951R. The sub-pixel (G) has a light-emitting device 130G that emits green light 951G. The sub-pixel (B) has a light-emitting device 130B that emits blue light 951B. By using these sub-pixels, a full-color image can be displayed on the display panel 280. The sub-pixel (PS) has a light-receiving device 150PS that receives light 32RGB. The infrared light 951IR emitted by the light source 104 is reflected by the object (here, the fundus), and the reflected light 32IR from the object is incident on the light-receiving device 150IRS. Although the object is not in contact with the electronic device, the object can be detected using the light-receiving device 150IRS.

[0093] When the display panel 280 shown in FIG. 7B is used, full-color photography uses light-emitting element 130R that emits red light 951R, light-emitting element 130G that emits green light 951G, and light-emitting element 130B that emits blue light 951B as light sources, and infrared light photography uses light-emitting element 130R that emits infrared light 951IR as a light source.

[0094] By making the optical system of the electronic device detachable, it is possible to switch between full-color display and fundus imaging.

[0095] This embodiment mode can be freely combined with other embodiment modes.

[0096] Embodiment 3 In this embodiment, a cross-sectional configuration example of a semiconductor device 100A that constitutes a display panel 280 corresponding to FIG. 4A will be described.

[0097] 9 is a cross-sectional view showing an example of the configuration of the semiconductor device 100A, illustrating a portion of the semiconductor device 100A. As described above, the semiconductor device 100A is composed of the layer 10, the layer 20, the layer 30, the layer 60, and the sealing substrate 40.

[0098] [Layer 10] The layer 10 includes a substrate 701, and a transistor 431 is provided over the substrate 701. The transistor 431 is, for example, a transistor included in a memory cell.

[0099] A single crystal semiconductor substrate typified by a single crystal silicon substrate can be used as the substrate 701. Note that a semiconductor substrate other than a single crystal semiconductor substrate may also be used as the substrate 701.

[0100] The transistor 431 includes a conductor 443 that functions as a gate electrode, an insulator 445 that functions as a gate insulator, and a part of a substrate 701. The part of the substrate 701 functions as a region including a channel formation region (semiconductor region 447), a source region (one of the low-resistance region 449a and the low-resistance region 449b), and a drain region (the other of the low-resistance region 449a and the low-resistance region 449b) of the transistor 431. The transistor 431 may be a p-channel transistor or an n-channel transistor.

[0101] When a single crystal semiconductor substrate typified by a single crystal silicon substrate is used as the substrate 701, the transistor 431 is a transistor containing silicon in a channel formation region (also referred to as a "Si transistor").

[0102] The transistor 431 is electrically isolated from other transistors by an element isolation layer 403. Fig. 9 shows a case where the transistor 431 is electrically isolated from other transistors by the element isolation layer 403. The element isolation layer 403 can be formed by a local oxidation of silicon (LOCOS) method or a shallow trench isolation (STI) method.

[0103] Here, the transistor 431 has a semiconductor region 447 that has a convex shape. The conductor 443 is provided to cover the side surface and the top surface of the semiconductor region 447 with the insulator 445 interposed therebetween. Note that the conductor 443 covering the side surface of the semiconductor region 447 is not illustrated in FIG. The conductor 443 can be formed using a material that adjusts the work function.

[0104] A transistor having a convex semiconductor region such as the transistor 431 can be called a fin transistor because it utilizes the convex portion of a semiconductor substrate. Note that an insulator that is in contact with the upper portion of the convex portion and functions as a mask for forming the convex portion may be provided. Although FIG. 9 shows a structure in which the convex portion is formed by processing a part of the substrate 701, a semiconductor having a convex portion may be formed by processing an SOI substrate.

[0105] 9 is just an example, and the transistor 431 is not limited to this configuration and may have an appropriate configuration depending on the circuit configuration or the operation method of the circuit. For example, the transistor 431 may be a planar transistor.

[0106] In addition to the element isolation layer 403 and the transistor 431, an insulator 405, an insulator 407, an insulator 409, and an insulator 411 are provided on the substrate 701. A conductor 451 is embedded in the insulator 405, the insulator 407, the insulator 409, and the insulator 411. Here, the height of the top surface of the conductor 451 and the height of the top surface of the insulator 411 can be made approximately the same.

[0107] An insulator 421 and an insulator 422 are provided on the conductor 451 and the insulator 411. A conductor 453 is embedded in the insulator 421 and the insulator 422. Here, the height of the top surface of the conductor 453 and the height of the top surface of the insulator 422 can be made approximately the same.

[0108] An insulator 423 is provided over the conductor 453 and the insulator 422. A conductor 455 is embedded in the insulator 423. Here, the height of the top surface of the conductor 455 and the height of the top surface of the insulator 423 can be made approximately the same.

[0109] If necessary, the layer 10 may have a multi-layer wiring structure by stacking insulators and conductors.

[0110] [Layer 20] The layer 20 includes a substrate 702 over which a transistor 441 and a transistor 442 are provided. The transistor 441 is, for example, a transistor included in a display unit driver circuit. The transistor 442 is, for example, a transistor included in a memory unit driver circuit.

[0111] As the substrate 702, a single crystal semiconductor substrate typified by a single crystal silicon substrate can be used, similarly to the substrate 701. Note that a semiconductor substrate other than a single crystal semiconductor substrate may also be used as the substrate 702. The layer 20 can have a structure similar to that of the layer 10. Therefore, detailed description of the layer 20 will be omitted.

[0112] 9, the transistor 442 included in the layer 20 and the transistor 431 included in the layer 10 are electrically connected to each other through a conductor 456. The conductor 456 functions as a TSV. Note that the layer 10 and the layer 20 may be electrically connected to each other through a bump.

[0113] The layer 20 includes a conductor 760. The conductor 760 is a conductor included in a terminal portion. In FIG. 9, the conductor 760 is electrically connected to a flexible printed circuit (FPC) 716 via an anisotropic conductor 780. Various signals are supplied to the semiconductor device 100A via the FPC 716.

[0114] Furthermore, the conductor 760 is electrically connected to the conductor 347 included in the layer 20 via the conductor 353, the conductor 355, and the conductor 357. Although Figure 9 shows three conductors, the conductor 353, the conductor 355, and the conductor 357, as conductors that electrically connect the conductor 760 and the conductor 347, one embodiment of the present invention is not limited thereto. The number of conductors that electrically connect the conductor 760 and the conductor 347 may be one, two, or four or more. By providing a plurality of conductors that electrically connect the conductor 760 and the conductor 347, contact resistance can be reduced.

[0115] [Layer 30] The layer 30 is provided over the layer 20. The layer 30 includes an insulator 214, and a transistor 750 is provided over the insulator 214. The transistor 750 is, for example, a transistor included in a pixel circuit. An OS transistor can be preferably used as the transistor 750. An OS transistor has an extremely low off-state current. Therefore, the retention time of image data can be extended, and therefore the frequency of refresh operations can be reduced. Therefore, the power consumption of the semiconductor device 100A can be reduced.

[0116] Conductors 301a and 301b are embedded in the insulators 254, 279, 274, and 281. The conductor 301a is electrically connected to one of the source and the drain of the transistor 750, and the conductor 301b is electrically connected to the other of the source and the drain of the transistor 750. Here, the height of the top surfaces of the conductors 301a and 301b can be made approximately the same as the height of the top surface of the insulator 281.

[0117] The conductors 311, 313, 331, the capacitor 790, the conductor 333, and the conductor 335 are embedded in the insulator 361. The conductors 311 and 313 are electrically connected to the transistor 750 and function as wirings. The conductors 333 and 335 are electrically connected to the capacitor 790. Here, the height of the top surfaces of the conductors 331, 333, and 335 can be made approximately the same as the height of the top surface of the insulator 361.

[0118] The conductors 341, 343, and 351 are embedded in the insulator 363. Here, the height of the top surface of the conductor 351 and the height of the top surface of the insulator 363 can be made to be approximately the same.

[0119] The insulators 405, 407, 409, 411, 421, 422, 423, 214, 279, 274, 281, 361, and 363 may function as interlayer films and may also function as planarizing films that cover uneven shapes below them. For example, the top surface of the insulator 363 may be planarized by planarization treatment using chemical mechanical polishing (CMP) to improve planarity.

[0120] 9, the capacitor 790 has a lower electrode 321 and an upper electrode 325. An insulator 323 is provided between the lower electrode 321 and the upper electrode 325. That is, the capacitor 790 has a layered structure in which the insulator 323, which functions as a dielectric, is sandwiched between a pair of electrodes. Note that while FIG. 9 shows an example in which the capacitor 790 is provided on the insulator 281, the capacitor 790 may be provided on an insulator different from the insulator 281.

[0121] 9 shows an example in which conductors 301a and 301b are formed in the same layer. Also, an example in which conductors 311, 313, and a lower electrode 321 are formed in the same layer is shown. Also, an example in which conductors 331, 333, and 335 are formed in the same layer is shown. Also, an example in which conductors 341 and 343 are formed in the same layer is shown. Furthermore, an example in which conductors 353, 355, and 357 are formed in the same layer is shown. Forming multiple conductors in the same layer simplifies the manufacturing process of the semiconductor device 100A, thereby reducing the manufacturing cost of the semiconductor device 100A. These may be formed in different layers and may be made of different types of materials.

[0122] [Layer 60] The layer 60 is provided over the layer 30. The layer 60 includes a light-emitting element 61. The light-emitting element 61 includes a conductor 772, an EL layer 786, and a conductor 788. The EL layer 786 includes an organic compound or an inorganic compound such as quantum dots.

[0123] Materials that can be used for the organic compounds include fluorescent materials and phosphorescent materials, and materials that can be used for the quantum dots include colloidal quantum dot materials, alloy quantum dot materials, core-shell quantum dot materials, and core quantum dot materials.

[0124] The conductor 772 is electrically connected to the other of the source and the drain of the transistor 750 through the conductors 351, 341, 331, 313, and 301b. The conductor 772 is formed over the insulator 363 and functions as a pixel electrode.

[0125] A material that is transparent to visible light or a material that is reflective to visible light can be used for the conductor 772. Examples of light-transmitting materials include oxide materials containing indium and zinc, oxide materials containing indium, gallium, and zinc (also referred to as "IGZO"), oxide materials containing indium, zinc, and tin (also referred to as "ITO"), and materials to which indium, zinc, tin, and silicon are added (also referred to as "ITSO"). Examples of reflective materials include materials containing aluminum or silver.

[0126] For example, when light emitted from the light-emitting element 61 is emitted from the conductor 788 side, the conductor 772 preferably contains a reflective material. The conductor 772 may have a single-layer structure or a stacked structure of multiple layers. For example, when the conductor 772 is used as an anode, it may have a three-layer structure in which silver is sandwiched between two ITO layers.

[0127] When silicon nitride is contained in the surface to be formed that is in contact with the conductor 772, the conductor 772 may have a three-layer structure in which aluminum, titanium oxide, and ITO (or ITSO) are stacked in this order from the surface to be formed. When silicon nitride is contained in the surface to be formed that is in contact with the conductor 772, the conductor 772 may have a two-layer structure in which aluminum and IGZO are stacked in this order from the surface to be formed.

[0128] Note that conductor 301a, conductor 301b, conductor 331, conductor 351, conductor 353, conductor 355, conductor 357, conductor 453, conductor 456, and conductor 760 may have the same structure as conductors 245a and 245b described in other embodiments. For example, conductor 351 electrically connected to light-emitting element 61 may be a conductor containing tungsten and titanium nitride. More specifically, a structure may be used in which tungsten is adjacent to the sidewall of insulator 363 via titanium nitride.

[0129] Although not shown in FIG. 9, the semiconductor device 100A may be provided with optical members (optical substrates) such as a polarizing member, a phase difference member, and an anti-reflection member.

[0130] 9, the insulator 730 is provided over the insulator 363. Here, the insulator 730 can be configured to cover part of the conductor 772. Furthermore, by using a light-transmitting material for the conductor 788, the light-emitting element 61 can be configured as a top-emission light-emitting element that emits light toward the conductor 788. Note that the light-emitting element 61 may have a bottom-emission structure that emits light toward the conductor 772, or a dual-emission structure that emits light toward both the conductor 772 and the conductor 788. Furthermore, a structure body 778 is provided between the insulator 730 and the EL layer 786.

[0131] [Sealing Substrate 40] The sealing substrate 40 covers the display portion and the layer 60 and is provided above the layer 30. The sealing substrate 40 is attached to the layer 30 with a sealant 712 (also referred to as a "sealing material"). When the light-emitting element 61 has a top-emission structure or a dual-emission structure, a light-transmitting material is used for the sealing substrate 40.

[0132] By providing the sealing substrate 40, it is possible to prevent impurities from entering the layer 60, thereby improving the reliability of the semiconductor device 100A.

[0133] A light-shielding layer 738 is provided on the layer 60 side. The light-shielding layer 738 has a function of blocking light emitted from an adjacent region. The light-shielding layer 738 also has a function of preventing external light from reaching the transistor 750. In FIG. 9 , the light-shielding layer 738 is provided to have a region overlapping with the insulator 730.

[0134] The light-shielding layer 738 is covered with an insulator 734. The insulator 734 may be provided as needed. Although this embodiment shows a solid sealing structure in which a filling layer 732 is provided between the light-emitting element 61 and the insulator 734, a hollow sealing structure without the filling layer 732 may also be used. When the semiconductor device 100A has a hollow sealing structure, an inert gas containing a Group 18 element (a rare gas (noble gas)) and / or nitrogen may be sealed in a portion corresponding to the filling layer 732. When light emitted by the light-emitting element 61 is emitted toward the sealing substrate 40, it is preferable to use a light-transmitting material for the filling layer 732.

[0135] <Modification 1> FIG. 10 shows a modification of the semiconductor device 100A shown in FIG. 9 . The semiconductor device 100A shown in FIG. 10 differs from the semiconductor device 100A shown in FIG. 9 in that a colored layer 736 is provided. Note that the colored layer 736 is provided so as to have a region overlapping with the light-emitting element 61. By providing the colored layer 736, the color purity of the light extracted from the light-emitting element 61 can be improved. This allows the semiconductor device 100A to display a high-quality image. Furthermore, since, for example, all of the light-emitting elements 61 of the semiconductor device 100A can be light-emitting elements that emit white light, it is not necessary to form the EL layer 786 by coloring, and the semiconductor device 100A can have high definition.

[0136] The light-emitting element 61 can have a micro-optical resonator (microcavity) structure. This allows light of a predetermined color (e.g., RGB) to be extracted without providing a colored layer, and the semiconductor device 100A can perform color display. By configuring the semiconductor device 100A without providing a colored layer, light absorption by the colored layer can be suppressed. This allows the semiconductor device 100A to display high-brightness images and reduce power consumption of the semiconductor device 100A. Note that even when the EL layer 786 is formed in an island shape for each pixel or in a striped shape for each pixel column, i.e., formed by coloring, a configuration without providing a colored layer can be used. Note that the luminance of the semiconductor device 100A can be, for example, 500 cd / m ２ More than 20000cd / m ２ Below 1000 cd / m ２ More than 20000cd / m ２ or less, more preferably 5000 cd / m ２ More than 20000cd / m ２ You can do the following:

[0137] 11 shows an example of a cross-sectional configuration of a semiconductor device 100B, which is a modification of the semiconductor device 100A. In the example of the cross-sectional configuration of the semiconductor device 100B shown in FIG. 11, a conductor 348 is provided on an insulator 361 of the layer 30, instead of the conductor 347.

[0138] The conductor 348 is electrically connected to the conductor 760 via the conductors 353, 355, and 357. The conductor 348 functions in the same manner as the conductor 347.

[0139] <Modification 3> Fig. 12 shows a cross-sectional configuration example in which layer 30 overlaps layer 10 via layer 20. Fig. 12 shows a cross-sectional configuration example of a semiconductor device 100C, which is a modification of semiconductor device 100B. In Fig. 12, layer 20 is provided overlapping layer 10 so that the transistors provided in layer 20 and the transistors provided in layer 10 face each other. Therefore, layer 30 is provided on the substrate 702 side of layer 20.

[0140] The conductors included in the layer 10 and the conductors included in the layer 20 can be electrically connected by, for example, a Cu-Cu bond. In FIG. 12 , for example, the conductor 455 included in the layer 10 and the conductor 465 included in the layer 20 are electrically connected by a Cu-Cu bond. In this case, the conductors 455 and 465 are formed of a conductor containing Cu (copper). Furthermore, the insulator 423 provided to be embedded in the conductor 455 and the insulator 424 provided to be embedded in the conductor 465 preferably contain the same element. For example, the insulators 423 and 424 may each be silicon oxide or silicon oxynitride. Using the insulators 423 and 424 containing the same element increases the bonding strength between the layer 10 and the layer 20. Furthermore, before bonding the layer 10 and the layer 20, it is preferable to perform CMP treatment on the bonding surfaces of both layers to increase the flatness of both surfaces.

[0141] 12, the conductors included in the layer 10 and the conductors included in the layer 20 may be electrically connected via TSVs. For example, the conductors 461 and 462 included in the layer 20 are both TSVs that penetrate the substrate 702.

[0142] <Modification 4> Fig. 13 shows an example of a cross-sectional configuration of a semiconductor device 100D, which is a modification of the semiconductor device 100C. Fig. 13 shows a semiconductor device corresponding to the display panel 280 of Fig. 4C. In the example of the cross-sectional configuration shown in Fig. 13, the transistors included in the layer 30 are configured as Si transistors.

[0143] Furthermore, as shown in FIG. 14 , a bump 454 and an adhesive layer 457 may be provided between the layer 10 and the layer 20. FIG. 14 shows an example of a cross-sectional configuration of a semiconductor device 100G, which is a modification of the semiconductor device 100D. FIG. 14 shows a semiconductor device corresponding to the display panel 280 of FIG. 4B . The layer 10 and the layer 20 are fixed by an adhesive layer 457 and electrically connected by a bump 454. In FIG. 14 , the conductor 456 and the conductor 455 are electrically connected via the bump 454. Similarly, a bump 458 and an adhesive layer 459 may be provided between the layer 20 and the layer 30. The layer 20 and the layer 30 are fixed by an adhesive layer 459 and electrically connected by the bump 458. Note that the number of bumps 454 electrically connecting the layer 10 and the layer 20 is not limited to one, and may be multiple. The number of bumps 458 electrically connecting the layer 20 and the layer 30 is not limited to one, and may be multiple.

[0144] In the semiconductor device 100A, the semiconductor device 100B, the semiconductor device 100C, the semiconductor device 100D, and the semiconductor device 100G, transistors other than OS transistors (for example, Si transistors) may be used as the transistors included in the layer 30. Various transistors can be used as the transistors included in the layer 10, the layer 20, and the layer 30 depending on the purpose or application.

[0145] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments.

[0146] Embodiment 4 In this embodiment, a light-emitting element 61 (also referred to as a "light-emitting device") will be described.

[0147] 15A , the light-emitting element 61 has an EL layer 786 between a pair of electrodes (a conductor 772 and a conductor 788). The EL layer 786 can be formed of a plurality of layers, including a layer 4420, a light-emitting layer 4411, and a layer 4430. The layer 4420 can have, for example, a layer containing a substance with high electron-injection properties (electron-injection layer) and a layer containing a substance with high electron-transport properties (electron-transport layer). The light-emitting layer 4411 contains, for example, a light-emitting compound. The layer 4430 can have, for example, a layer containing a substance with high hole-injection properties (hole-injection layer) and a layer containing a substance with high hole-transport properties (hole-transport layer).

[0148] A structure having the layer 4420, the light-emitting layer 4411, and the layer 4430 provided between a pair of electrodes can function as a single light-emitting unit, and the structure of FIG. 15A is referred to as a single structure in this specification.

[0149] 15B shows a modified example of the EL layer 786 included in the light-emitting element 61 shown in Fig. 15A. Specifically, the light-emitting element 61 shown in Fig. 15B includes a layer 4430-1 on the conductor 772, a layer 4430-2 on the layer 4430-1, a light-emitting layer 4411 on the layer 4430-2, a layer 4420-1 on the light-emitting layer 4411, a layer 4420-2 on the layer 4420-1, and a conductor 788 on the layer 4420-2. For example, when the conductor 772 serves as an anode and the conductor 788 serves as a cathode, the layer 4430-1 functions as a hole-injection layer, the layer 4430-2 functions as a hole-transport layer, the layer 4420-1 functions as an electron-transport layer, and the layer 4420-2 functions as an electron-injection layer. Alternatively, when the conductor 772 is a cathode and the conductor 788 is an anode, the layer 4430-1 functions as an electron injection layer, the layer 4430-2 functions as an electron transport layer, the layer 4420-1 functions as a hole transport layer, and the layer 4420-2 functions as a hole injection layer. With such a layer structure, carriers can be efficiently injected into the light-emitting layer 4411, and the efficiency of carrier recombination in the light-emitting layer 4411 can be increased.

[0150] Note that a structure in which a plurality of light-emitting layers (light-emitting layer 4411, light-emitting layer 4412, light-emitting layer 4413) are provided between layer 4420 and layer 4430 as shown in FIG. 15C is also an example of a single structure.

[0151] 15D , a configuration in which a plurality of light-emitting units (EL layers 786 a and 786 b) are connected in series via an intermediate layer (charge generation layer) 4440 is referred to as a tandem structure or a stack structure in this specification. Note that the tandem structure makes it possible to realize a light-emitting element that can emit light with high brightness.

[0152] Furthermore, when the light-emitting element 61 has a tandem structure as shown in FIG. 15D , the EL layer 786 a and the EL layer 786 b may emit the same light. For example, the EL layer 786 a and the EL layer 786 b may both emit green light. When the display unit includes three subpixels of R, G, and B, each of which has a light-emitting element, the light-emitting elements of the subpixels may be arranged in a tandem structure. Specifically, the EL layer 786 a and the EL layer 786 b of the R subpixel each contain a material capable of emitting red light, the EL layer 786 a and the EL layer 786 b of the G subpixel each contain a material capable of emitting green light, and the EL layer 786 a and the EL layer 786 b of the B subpixel each contain a material capable of emitting blue light. In other words, the light-emitting layer 4411 and the light-emitting layer 4412 may be made of the same material. By making the EL layers 786a and 786b emit light of the same color, the current density per unit of emitted light luminance can be reduced, thereby improving the reliability of the light-emitting element 61.

[0153] The emission color of the light-emitting element can be red, green, blue, cyan, magenta, yellow, or white depending on the material forming the EL layer 786. In addition, the color purity can be further improved by providing the light-emitting element with a microcavity structure.

[0154] The light-emitting layer may contain two or more light-emitting materials that emit R (red), G (green), B (blue), Y (yellow), or O (orange). A light-emitting element that emits white light (also referred to as a "white-light-emitting device") preferably has a configuration in which the light-emitting layer contains two or more types of light-emitting materials. To obtain white light emission, light-emitting materials may be selected such that the respective emissions of the two or more light-emitting materials are in a complementary color relationship. For example, by making the emission color of the first light-emitting layer and the emission color of the second light-emitting layer complementary to each other, a light-emitting element that emits white light as a whole can be obtained. The same applies to a light-emitting element having three or more light-emitting layers.

[0155] The light-emitting layer preferably contains two or more light-emitting materials that emit R (red), G (green), B (blue), Y (yellow), and O (orange). Alternatively, the light-emitting layer preferably contains two or more light-emitting materials, and the light emitted by each of the light-emitting materials preferably contains spectral components of two or more colors of R, G, and B.

[0156] <Method of Forming Light-Emitting Element 61> A method of forming the light-emitting element 61 will be described below.

[0157] FIG. 16A shows a schematic top view of a light-emitting element 61. The light-emitting element 61 includes a plurality of light-emitting elements 61R that emit red light, a plurality of light-emitting elements 61G that emit green light, and a plurality of light-emitting elements 61B that emit blue light. In FIG. 16A, the symbols R, G, and B are assigned within the light-emitting region of each light-emitting element to easily distinguish between the light-emitting elements. The configuration of the light-emitting element 61 shown in FIG. 16A may be referred to as an SBS (Side By Side) structure. The configuration shown in FIG. 16A illustrates a configuration having three colors, red (R), green (G), and blue (B), but is not limited to this. For example, a configuration having four or more colors may also be used.

[0158] The light-emitting elements 61R, 61G, and 61B are arranged in a matrix. Fig. 16A shows a so-called stripe arrangement in which light-emitting elements of the same color are arranged in one direction. Note that the arrangement of the light-emitting elements is not limited to this, and a delta arrangement, a zigzag arrangement, or a pentile arrangement may also be used.

[0159] As the light-emitting element 61R, the light-emitting element 61G, and the light-emitting element 61B, it is preferable to use an organic EL device represented by an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode). Examples of light-emitting materials contained in the EL elements include fluorescent materials, phosphorescent materials, inorganic compounds (quantum dot materials), and materials that exhibit thermally activated delayed fluorescence (thermally activated delayed fluorescence: TADF materials).

[0160] FIG. 16B is a schematic cross-sectional view corresponding to the dashed-dotted line A5-A6 in FIG. 16A . FIG. 16B shows cross sections of the light-emitting elements 61R, 61G, and 61B. The light-emitting elements 61R, 61G, and 61B are each provided on an insulating layer 251 and include a conductor 772 functioning as a pixel electrode and a conductor 788 functioning as a common electrode. The insulating layer 251 can be an inorganic insulating film or an organic insulating film, or both. It is preferable to use an inorganic insulating film as the insulating layer 251. Examples of inorganic insulating films include oxide insulating films and nitride insulating 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, or a hafnium oxide film.

[0161] The light-emitting element 61R includes an EL layer 786R between a conductor 772 functioning as a pixel electrode and a conductor 788 functioning as a common electrode. The EL layer 786R includes a light-emitting organic compound that emits light having an intensity in at least a red wavelength range. The EL layer 786G included in the light-emitting element 61G includes a light-emitting organic compound that emits light having an intensity in at least a green wavelength range. The EL layer 786B included in the light-emitting element 61B includes a light-emitting organic compound that emits light having an intensity in at least a blue wavelength range.

[0162] The EL layer 786R, the EL layer 786G, and the EL layer 786B may each have one or more of an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer in addition to a layer containing a light-emitting organic compound (light-emitting layer).

[0163] The conductor 772 functioning as a pixel electrode is provided for each light-emitting element. The conductor 788 functioning as a common electrode is provided as a continuous layer common to each light-emitting element. A conductive film that is transparent to visible light is used for either the conductor 772 functioning as a pixel electrode or the conductor 788 functioning as a common electrode, and a conductive film that is reflective is used for the other. By making the conductor 772 functioning as a pixel electrode light-transmitting and the conductor 788 functioning as a common electrode light-reflective, a bottom-emission display device can be obtained. Conversely, by making the conductor 772 functioning as a pixel electrode light-reflective and the conductor 788 functioning as a common electrode light-transmitting, a top-emission display device can be obtained. Note that by making both the conductor 772 functioning as a pixel electrode and the conductor 788 functioning as a common electrode light-transmitting, a dual-emission display device can also be obtained.

[0164] An insulating layer 272 is provided to cover an end portion of the conductor 772 functioning as a pixel electrode. The end portion of the insulating layer 272 preferably has a tapered shape. The insulating layer 272 can be formed using a material similar to that of the insulating layer 251.

[0165] The EL layer 786R, the EL layer 786G, and the EL layer 786B each have a region in contact with the top surface of the conductor 772 that functions as a pixel electrode and a region in contact with the surface of the insulating layer 272. Ends of the EL layer 786R, the EL layer 786G, and the EL layer 786B are located on the insulating layer 272.

[0166] As shown in Figure 16B, a gap is provided between two EL layers between light-emitting elements of different colors. In this manner, it is preferable that the EL layer 786R, the EL layer 786G, and the EL layer 786B are provided so as not to be in contact with each other. This can suitably prevent current from flowing through two adjacent EL layers, which can cause unintended light emission (also known as crosstalk). Therefore, contrast can be increased, and a display device with high display quality can be realized.

[0167] The EL layers 786R, 786G, and 786B can be separately formed by vacuum deposition using a shadow mask, typically a metal mask. Alternatively, they may be separately formed by photolithography. By using photolithography, a high-definition display device can be realized, which is difficult to achieve using a metal mask.

[0168] In addition, a protective layer 271 is provided over the conductor 788 functioning as a common electrode to cover the light-emitting elements 61R, 61G, and 61B. The protective layer 271 has a function of preventing impurities, such as water, from diffusing from above to each light-emitting element.

[0169] The protective layer 271 can have, for example, a single-layer structure or a stacked structure including at least an inorganic insulating film. Examples of inorganic insulating films 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 271 may be made of a semiconductor material such as indium gallium oxide or indium gallium zinc oxide (IGZO). The protective layer 271 may be formed by an ALD method, a CVD method, or a sputtering method. While the protective layer 271 includes an inorganic insulating film, the present invention is not limited to this. For example, the protective layer 271 may have a stacked structure including an inorganic insulating film and an organic insulating film.

[0170] In this specification, "nitride oxide" refers to a compound containing more nitrogen than oxygen. "oxynitride" refers to a compound containing more oxygen than nitrogen. The content of each element can be measured, for example, by Rutherford backscattering spectrometry (RBS).

[0171] When indium gallium zinc oxide is used as the protective layer 271, it can be processed by wet etching or dry etching. For example, when IGZO is used as the protective layer 271, a chemical solution typified by oxalic acid, phosphoric acid, or a mixed chemical solution (for example, a mixed chemical solution of phosphoric acid, acetic acid, nitric acid, and water (also referred to as a mixed acid aluminum etching solution)) can be used. Note that the mixed acid aluminum etching solution can have a volume ratio of phosphoric acid:acetic acid:nitric acid:water of approximately 53.3:6.7:3.3:36.7.

[0172] 16C shows a different example. Specifically, Fig. 16C shows a light-emitting element 61W that emits white light. The light-emitting element 61W includes an EL layer 786W that emits white light between a conductor 772 that functions as a pixel electrode and a conductor 788 that functions as a common electrode.

[0173] The EL layer 786W may be configured by stacking two or more light-emitting layers selected so that the emitted light colors are complementary to each other. Alternatively, a stacked EL layer may be used in which a charge generating layer is sandwiched between light-emitting layers.

[0174] 16C shows three light-emitting elements 61W lined up. A colored layer 264R is provided on the top of the left light-emitting element 61W. The colored layer 264R functions as a bandpass filter that transmits red light. Similarly, a colored layer 264G that transmits green light is provided on the top of the center light-emitting element 61W, and a colored layer 264B that transmits blue light is provided on the top of the right light-emitting element 61W. This allows the display device to display color images.

[0175] Here, the EL layer 786W and the conductor 788 functioning as a common electrode are separated between two adjacent light-emitting elements 61W. This prevents unintended light emission due to current flowing through the EL layer 786W between the two adjacent light-emitting elements 61W. In particular, when a stacked EL layer in which a charge generation layer is provided between two light-emitting layers is used as the EL layer 786W, the higher the resolution, i.e., the smaller the distance between adjacent pixels, the more pronounced the effect of crosstalk becomes, resulting in a decrease in contrast. Therefore, by using such a configuration, a display device that combines high resolution and high contrast can be realized.

[0176] The EL layer 786W and the conductor 788 functioning as a common electrode are preferably separated by photolithography, which allows the distance between light-emitting elements to be narrowed, thereby realizing a display device with a higher aperture ratio than when, for example, a metal shadow mask is used.

[0177] In the case of a bottom-emission light-emitting element, a colored layer may be provided between the conductor 772 functioning as a pixel electrode and the insulating layer 251 .

[0178] FIG. 16D shows an example different from the above. Specifically, FIG. 16D shows a structure in which the insulating layer 272 is not provided between the light-emitting element 61R, the light-emitting element 61G, and the light-emitting element 61B. This structure enables a display device with a high aperture ratio. Furthermore, the protective layer 271 covers the side surfaces of the EL layer 786R, the EL layer 786G, and the EL layer 786B. This structure can suppress impurities (typically, water) that may enter from the side surfaces of the EL layer 786R, the EL layer 786G, and the EL layer 786B. Furthermore, in the structure shown in FIG. 16D , the top surfaces of the conductor 772, the EL layer 786R, and the conductor 788 have approximately the same shape. This structure can be formed collectively using a resist mask after the conductor 772, the EL layer 786R, and the conductor 788 are formed. Such a process can also be called self-aligned patterning because the EL layer 786R and the conductor 788 are processed using the conductor 788 as a mask. Note that although the EL layer 786R has been described here, the EL layer 786G and the EL layer 786B can also have a similar structure.

[0179] 16D shows a structure in which a protective layer 273 is further provided on the protective layer 271. For example, the protective layer 271 may be formed using an apparatus (typically, an ALD apparatus) capable of depositing a film with high coverage, and the protective layer 273 may be formed using an apparatus (typically, a sputtering apparatus) capable of depositing a film with lower coverage than the protective layer 271, thereby providing a gap 275 between the protective layer 271 and the protective layer 273. In other words, the gap 275 is located between the EL layer 786R and the EL layer 786G, and between the EL layer 786G and the EL layer 786B.

[0180] The void 275 contains, for example, one or more selected from air, nitrogen, oxygen, carbon dioxide, and Group 18 elements (typically, helium, neon, argon, xenon, and krypton). The void 275 may also contain, for example, a gas used during deposition of the protective layer 273. For example, when the protective layer 273 is deposited by sputtering, the void 275 may contain one or more of the above Group 18 elements. When the void 275 contains a gas, the gas can be identified by gas chromatography. Alternatively, when the protective layer 273 is deposited by sputtering, the gas used during sputtering may also be contained in the protective layer 273. In this case, argon elements may be detected when the protective layer 273 is analyzed by energy dispersive X-ray analysis (EDX analysis).

[0181] Furthermore, if the refractive index of the void 275 is lower than the refractive index of the protective layer 271, light emitted from the EL layer 786R, the EL layer 786G, or the EL layer 786B is reflected at the interface between the protective layer 271 and the void 275. This may prevent the light emitted from the EL layer 786R, the EL layer 786G, or the EL layer 786B from entering an adjacent pixel. This prevents the light of different colors from being mixed in with the light emitted from neighboring pixels, thereby improving the display quality of the display device.

[0182] 16D , the area between light-emitting element 61R and light-emitting element 61G or the area between light-emitting element 61G and light-emitting element 61B (hereinafter simply referred to as the distance between the light-emitting elements) can be narrowed. Specifically, the distance between the light-emitting elements can be set to 1 μm or less, preferably 500 nm or less, and more preferably 200 nm or less, 100 nm or less, 90 nm or less, 70 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less. In other words, the distance between the side surface of EL layer 786R and the side surface of EL layer 786G or the distance between the side surface of EL layer 786G and the side surface of EL layer 786B has an area of ​​1 μm or less, preferably an area of ​​0.5 μm (500 nm) or less, and more preferably an area of ​​100 nm or less.

[0183] 16D can be referred to as an air isolation structure, for example, when the gap 275 contains gas. The air isolation structure can isolate the light emitting elements while suppressing color mixing or crosstalk of light from each light emitting element.

[0184] Alternatively, the gap 275 may be filled with a filler. Examples of the filler include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. Alternatively, a photoresist may be used as the filler. The photoresist used as the filler may be a positive photoresist or a negative photoresist.

[0185] Furthermore, when filling the gap 275 with a filler, it is preferable to combine an inorganic insulating material with an organic insulating material. Specifically, a laminate structure in which aluminum oxide and a photoresist are provided on the aluminum oxide can be used. Note that the aluminum oxide is preferably formed using the ALD method, as this can improve coverage.

[0186] Furthermore, when comparing the above-described white light-emitting device (single structure or tandem structure) with a light-emitting device having an SBS structure, the light-emitting device having an SBS structure can reduce power consumption compared to the white light-emitting device. If it is desired to reduce power consumption, it is preferable to use a light-emitting device having an SBS structure. On the other hand, the manufacturing process of a white light-emitting device is simpler than that of a light-emitting device having an SBS structure, and therefore the manufacturing cost can be reduced or the manufacturing yield can be increased, making it preferable.

[0187] FIG. 17A shows an example different from the above. Specifically, the structure shown in FIG. 17A differs from the structure shown in FIG. 16D in the structure of the insulating layer 251. The insulating layer 251 has a recess formed by removing a portion of its upper surface during processing of the light-emitting elements 61R, 61G, and 61B. A protective layer 271 is formed in the recess. In other words, the insulating layer 251 has a region where the lower surface of the protective layer 271 is located lower than the lower surface of the conductor 772 in a cross-sectional view. By providing this region, impurities (typically, water) that may enter the light-emitting elements 61R, 61G, and 61B from below can be suitably suppressed. Note that the recess can be formed when impurities (also referred to as residue) that may adhere to the side surfaces of the light-emitting elements 61R, 61G, and 61B are removed by wet etching during processing of the light-emitting elements 61R, 61G, and 61B. After removing the residue, the side surfaces of the light-emitting elements are covered with the protective layer 271, thereby achieving a highly reliable display device.

[0188] FIG. 17B also shows a different example. Specifically, the configuration shown in FIG. 17B includes an insulating layer 276 and a microlens array 277 in addition to the configuration shown in FIG. 17A . The insulating layer 276 functions as an adhesive layer. When the refractive index of the insulating layer 276 is lower than that of the microlens array 277, the microlens array 277 can focus the light emitted from the light-emitting elements 61R, 61G, and 61B. This improves the light extraction efficiency of the display device. This is particularly advantageous because it allows a user to view a bright image when viewing the display surface from directly in front of the display surface. The insulating layer 276 can be made of various curing adhesives, such as an ultraviolet-curing photocuring adhesive, a reactive curing adhesive, a thermosetting adhesive, or an anaerobic adhesive. Examples of such adhesives include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. Epoxy resins with low moisture permeability are particularly preferred. Two-component resins may also be used. An adhesive sheet may also be used.

[0189] FIG. 17C also shows an example different from the above. Specifically, the configuration shown in FIG. 17C has three light-emitting elements 61W instead of the light-emitting elements 61R, 61G, and 61B in the configuration shown in FIG. 17A. An insulating layer 276 is provided above the three light-emitting elements 61W, and coloring layers 264R, 264G, and 264B are provided above the insulating layer 276. Specifically, a coloring layer 264R that transmits red light is provided at a position overlapping the left light-emitting element 61W, a coloring layer 264G that transmits green light is provided at a position overlapping the center light-emitting element 61W, and a coloring layer 264B that transmits blue light is provided at a position overlapping the right light-emitting element 61W. This allows the semiconductor device to display a color image. The configuration shown in FIG. 17C is also a variation of the configuration shown in FIG. 16C.

[0190] 17D shows an example different from the above. Specifically, in the configuration shown in FIG. 17D, a protective layer 271 is provided adjacent to the side surfaces of a conductor 772 and an EL layer 786. Furthermore, a conductor 788 is provided as a continuous layer common to each light-emitting element. Furthermore, in the configuration shown in FIG. 17D, it is preferable that the void 275 is filled with a filler material.

[0191] The color purity of the emitted color can be increased by providing a micro-optical resonator (microcavity) structure to the light-emitting element 61. To provide the light-emitting element 61 with a microcavity structure, the product (optical path length) of the distance d between the conductor 772 and the conductor 788 and the refractive index n of the EL layer 786 should be configured to be m times half the wavelength λ (m is an integer of 1 or greater). The distance d can be calculated using Equation 1.

[0192] d = m × λ / (2 × n)... Equation 1.

[0193] According to Equation 1, the distance d of the light-emitting element 61 having the microcavity structure is determined according to the wavelength of the emitted light (emission color). The distance d corresponds to the thickness of the EL layer 786. Therefore, the EL layer 786G may be provided thicker than the EL layer 786B, and the EL layer 786R may be provided thicker than the EL layer 786G.

[0194] Strictly speaking, the distance d is the distance from the reflective region of the conductor 772, which functions as a reflective electrode, to the reflective region of the conductor 788, which functions as a semi-transmissive and semi-reflective electrode. For example, if the conductor 772 is a laminate of silver and ITO, which is a transparent conductive film, and the ITO is on the EL layer 786 side, the distance d can be set according to the emitted color by adjusting the film thickness of the ITO. In other words, even if the thicknesses of the EL layers 786R, 786G, and 786B are the same, the distance d appropriate for the emitted color can be obtained by changing the thickness of the ITO.

[0195] However, it may be difficult to precisely determine the positions of the reflection regions in the conductors 772 and 788. In this case, it is assumed that the microcavity effect can be fully obtained by assuming that any position in the conductors 772 and 788 is the reflection region.

[0196] The light-emitting element 61 is composed of a hole transport layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer. Detailed configuration examples of the light-emitting element 61 will be described in other embodiments. In order to increase the light extraction efficiency in the microcavity structure, it is preferable to set the optical distance from the conductor 772 functioning as a reflective electrode to the light-emitting layer to an odd multiple of λ / 4. To achieve this optical distance, it is preferable to appropriately adjust the thickness of each layer constituting the light-emitting element 61.

[0197] Furthermore, when light is emitted from the conductor 788 side, it is preferable that the reflectance of the conductor 788 be higher than the transmittance. The light transmittance of the conductor 788 is preferably 2% or more and 50% or less, more preferably 2% or more and 30% or less, and even more preferably 2% or more and 10% or less. By reducing the transmittance of the conductor 788 (increasing the reflectance), the effect of the microcavity can be enhanced.

[0198] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments.

[0199] Embodiment 5 In this embodiment, a transistor that can be used for a semiconductor device according to one embodiment of the present invention will be described.

[0200] 18A , 18B , and 18C are a top view and a cross-sectional view of a transistor 200 that can be used in a semiconductor device according to one embodiment of the present invention and a periphery of the transistor 200. The transistor 200 can be applied to a semiconductor device according to one embodiment of the present invention. For example, the transistor 200 can be used as a transistor included in the layer 30.

[0201] FIG. 18A is a top view of the transistor 200. Also, FIGS. 18B and 18C are cross-sectional views of the transistor 200. Here, FIG. 18B is a cross-sectional view of a portion indicated by a dashed dotted line A1-A2 in FIG. 18A and is also a cross-sectional view of the transistor 200 in the channel length direction. Also, FIG. 18C is a cross-sectional view of a portion indicated by a dashed dotted line A3-A4 in FIG. 18A and is also a cross-sectional view of the transistor 200 in the channel width direction. Note that in the top view of FIG. 18A, some elements are omitted for clarity.

[0202] As shown in FIG. 18 , the transistor 200 has a metal oxide 231 a arranged on a substrate (not shown), a metal oxide 231 b arranged on the metal oxide 231 a, a conductor 242 a and a conductor 242 b arranged spaced apart from each other on the metal oxide 231 b, an insulator 279 arranged on the conductors 242 a and 242 b and having an opening formed between the conductors 242 a and 242 b, a conductor 260 arranged in the opening, an insulator 250 arranged among the metal oxide 231 b, the conductors 242 a, the conductors 242 b, the insulator 279, and the conductor 260, and a metal oxide 231 c arranged among the metal oxide 231 b, the conductors 242 a, the conductors 242 b, the insulator 279, and the insulator 250. 18B and 18C, it is preferable that the upper surface of conductor 260 substantially coincides with the upper surfaces of insulators 250, 254, metal oxide 231c, and insulator 279. Note that, hereinafter, metal oxide 231a, metal oxide 231b, and metal oxide 231c may be collectively referred to as metal oxide 231.

[0203] 18 , the side surfaces of the conductors 242a and 242b facing the conductor 260 have a substantially vertical shape. Note that the transistor 200 shown in FIG. 18 is not limited to this, and the angle formed between the side surface and the bottom surface of the conductors 242a and 242b may be 10° to 80°, preferably 30° to 60°. Furthermore, the opposing side surfaces of the conductors 242a and 242b may have multiple surfaces.

[0204] 18 , it is preferable that insulator 254 be disposed between insulator 224, metal oxide 231a, metal oxide 231b, conductor 242a, conductor 242b, and metal oxide 231c and insulator 279. Here, it is preferable that insulator 254 be in contact with the side surface of metal oxide 231c, the top and side surfaces of conductor 242a, the top and side surfaces of conductor 242b, the side surfaces of metal oxide 231a and metal oxide 231b, and the top surface of insulator 224, as shown in FIGS.

[0205] Although the transistor 200 has a three-layer structure of the metal oxide 231a, the metal oxide 231b, and the metal oxide 231c in and around a region where a channel is formed (hereinafter also referred to as a channel formation region), the present invention is not limited to this. For example, a two-layer structure of the metal oxide 231b and the metal oxide 231c or a stacked structure of four or more layers may be provided. Although the transistor 200 has a two-layer structure of the conductor 260, the present invention is not limited to this. For example, the conductor 260 may have a single-layer structure or a stacked structure of three or more layers. Furthermore, each of the metal oxide 231a, the metal oxide 231b, and the metal oxide 231c may have a stacked structure of two or more layers.

[0206] For example, when the metal oxide 231c has a layered structure consisting of a first metal oxide and a second metal oxide on the first metal oxide, it is preferable that the first metal oxide has a composition similar to that of the metal oxide 231b, and the second metal oxide has a composition similar to that of the metal oxide 231a.

[0207] Here, the conductor 260 functions as the gate electrode of the transistor, and the conductors 242a and 242b function as source and drain electrodes, respectively. As described above, the conductor 260 is formed so as to be embedded in the opening of the insulator 279 and in the region sandwiched between the conductors 242a and 242b. Here, the arrangements of the conductors 260, 242a, and 242b are selected in a self-aligned manner with respect to the opening of the insulator 279. That is, in the transistor 200, the gate electrode can be arranged between the source and drain electrodes in a self-aligned manner. Therefore, the conductor 260 can be formed without providing a margin for alignment, thereby reducing the area occupied by the transistor 200. This allows the display device to have high resolution. Furthermore, the display device can have a narrow frame.

[0208] As shown in FIG. 18, the conductor 260 preferably has a conductor 260a provided inside the insulator 250 and a conductor 260b provided so as to be embedded inside the conductor 260a.

[0209] The transistor 200 preferably includes an insulator 214 disposed on a substrate (not shown), an insulator 216 disposed on the insulator 214, a conductor 205 disposed so as to be embedded in the insulator 216, an insulator 222 disposed on the insulator 216 and the conductor 205, and an insulator 224 disposed on the insulator 222. A metal oxide 231a is preferably disposed on the insulator 224.

[0210] An insulator 274 functioning as an interlayer film and an insulator 281 are preferably disposed over the transistor 200. Here, the insulator 274 is preferably disposed in contact with top surfaces of the conductor 260, the insulator 250, the insulator 254, the metal oxide 231c, and the insulator 279.

[0211] It is preferable that the insulators 222, 254, and 274 have the function of suppressing the diffusion of at least one of hydrogen (e.g., hydrogen atoms, hydrogen molecules). For example, it is preferable that the insulators 222, 254, and 274 have lower hydrogen permeability than the insulators 224, 250, and 279. It is also preferable that the insulators 222 and 254 have the function of suppressing the diffusion of at least one of oxygen (e.g., oxygen atoms, oxygen molecules). For example, it is preferable that the insulators 222 and 254 have lower oxygen permeability than the insulators 224, 250, and 279.

[0212] Here, insulator 224, metal oxide 231, and insulator 250 are separated by insulators 279 and 281, and by insulators 254 and 274. This prevents hydrogen impurities and excess oxygen contained in insulators 279 and 281 from being mixed into insulator 224, metal oxide 231, and insulator 250.

[0213] It is preferable that conductors 245a and 245b, which are electrically connected to the transistor 200 and function as plugs, are provided. Note that insulators (insulators 241a and 241b) are provided in contact with the side surfaces of the conductors 245a and 245b, which function as plugs. That is, the insulators 241a and 241b are provided in contact with the inner walls of the openings of the insulators 254, 279, 274, and 281. Alternatively, a configuration may be adopted in which first conductors of the conductors 245a and 245b are provided in contact with the side surfaces of the insulators 241a and 241b, and second conductors of the conductors 245a and 245b are provided further inward. Here, the height of the top surfaces of the conductors 245a and 245b can be made approximately the same as the height of the top surface of the insulator 281. Note that, although the transistor 200 has a stacked structure including the first conductors 245a and 245b and the second conductors 245a and 245b, the present invention is not limited to this. For example, the conductors 245a and 245b may be provided as a single layer or a stacked structure of three or more layers. When the structure has a stacked structure, the structures may be distinguished by assigning ordinal numbers to the order of formation.

[0214] In the transistor 200, a metal oxide that functions as an oxide semiconductor (hereinafter also referred to as an oxide semiconductor) is preferably used for the metal oxide 231 (the metal oxide 231a, the metal oxide 231b, and the metal oxide 231c) including the channel formation region. For example, a metal oxide that serves as the channel formation region of the metal oxide 231 preferably has a band gap of 2 eV or more, preferably 2.5 eV or more.

[0215] The metal oxide preferably contains at least indium (In) or zinc (Zn). In particular, it is preferable that it contains indium (In) and zinc (Zn). Furthermore, it is preferable that it contains an element M in addition to these. The element M can be one or more of aluminum (Al), gallium (Ga), yttrium (Y), tin (Sn), boron (B), titanium (Ti), iron (Fe), nickel (Ni), germanium (Ge), zirconium (Zr), molybdenum (Mo), lanthanum (La), cerium (Ce), neodymium (Nd), hafnium (Hf), tantalum (Ta), tungsten (W), magnesium (Mg), or cobalt (Co). In particular, it is preferable that the element M is one or more of aluminum (Al), gallium (Ga), yttrium (Y), or tin (Sn). Furthermore, it is even more preferable that the element M contains either or both of gallium (Ga) and tin (Sn).

[0216] 18B , the film thickness of the metal oxide 231b in the region that does not overlap with the conductors 242a and 242b may be thinner than the film thickness of the region that overlaps with the conductors 242a and 242b. This is formed by removing a portion of the upper surface of the metal oxide 231b when forming the conductors 242a and 242b. When a conductive film that will become the conductors 242a and 242b is formed on the upper surface of the metal oxide 231b, a low-resistance region may be formed near the interface with the conductive film. In this way, removing the low-resistance region located between the conductors 242a and 242b on the upper surface of the metal oxide 231b can prevent a channel from being formed in that region.

[0217] According to one embodiment of the present invention, a display device having high definition and a small transistor can be provided. Alternatively, a display device having high luminance and a transistor with high on-state current can be provided. Alternatively, a display device having high-speed operation and a transistor with stable electrical characteristics can be provided. Alternatively, a display device having low power consumption and a transistor with low off-state current can be provided.

[0218] A detailed structure of the transistor 200 that can be used in the display device of one embodiment of the present invention will be described.

[0219] The conductor 205 is arranged to have a region overlapping with the metal oxide 231 and the conductor 260. The conductor 205 is preferably embedded in the insulator 216.

[0220] The conductor 205 includes conductor 205a, conductor 205b, and conductor 205c. The conductor 205a is provided in contact with the bottom surface and sidewall of an opening provided in the insulator 216. The conductor 205b is provided so as to be embedded in a recess formed in the conductor 205a. Here, the top surface of the conductor 205b is lower than the top surface of the conductor 205a and the top surface of the insulator 216. The conductor 205c is provided in contact with the top surface of the conductor 205b and the side surface of the conductor 205a. Here, the height of the top surface of the conductor 205c is approximately the same as the height of the top surface of the conductor 205a and the height of the top surface of the insulator 216. In other words, the conductor 205b is configured to be enclosed by the conductors 205a and 205c.

[0221] The conductors 205a and 205c are made of hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, and nitrogen oxide molecules (N ２ O, NO, NO ２ ), it is preferable to use a conductive material that has a function of suppressing the diffusion of impurities such as copper atoms, or a conductive material that has a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms and oxygen molecules).

[0222] By using a conductive material that has the function of reducing hydrogen diffusion for the conductor 205a and the conductor 205c, it is possible to prevent impurities, such as hydrogen, contained in the conductor 205b from diffusing into the metal oxide 231 via the insulator 224. Furthermore, by using a conductive material that has the function of suppressing oxygen diffusion for the conductor 205a and the conductor 205c, it is possible to prevent the conductor 205b from being oxidized and its conductivity from decreasing. Examples of conductive materials that have the function of suppressing oxygen diffusion include titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Therefore, the conductor 205a may be formed as a single layer or a multilayer of the above conductive materials. For example, the conductor 205a may be made of titanium nitride.

[0223] The conductor 205b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component, for example, tungsten.

[0224] Here, the conductor 260 may function as a first gate (also referred to as a top gate) electrode. The conductor 205 may function as a second gate (also referred to as a bottom gate) electrode. In this case, the potential applied to the conductor 205 may be changed independently of the potential applied to the conductor 260, thereby controlling the V ｔｈ In particular, applying a negative potential to the conductor 205 can control the V ｔｈ Therefore, when a negative potential is applied to the conductor 205, the drain current when the potential applied to the conductor 260 is 0 V can be made smaller than when no negative potential is applied.

[0225] The conductor 205 is preferably provided to be larger than the channel formation region of the metal oxide 231. In particular, as shown in Fig. 18C, it is preferable that the conductor 205 also extends in a region outside the end portion intersecting with the channel width direction of the metal oxide 231. In other words, it is preferable that the conductor 205 and the conductor 260 overlap with each other with an insulator interposed therebetween on the outside of the side surface of the metal oxide 231 in the channel width direction.

[0226] With the above structure, the channel formation region of the metal oxide 231 can be electrically surrounded by the electric field of the conductor 260 that functions as a first gate electrode and the electric field of the conductor 205 that functions as a second gate electrode.

[0227] 18C, the conductor 205 is extended to function as wiring. However, the present invention is not limited to this, and a conductor functioning as wiring may be provided below the conductor 205.

[0228] The insulator 214 preferably functions as a barrier insulating film that prevents impurities, such as water or hydrogen, from entering the transistor 200 from the substrate side. Therefore, the insulator 214 prevents impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, and nitrogen oxide molecules (N ２ O, NO, NO ２ It is preferable to use an insulating material that has a function of suppressing the diffusion of impurities such as copper atoms (i.e., the impurities are less likely to permeate through), or that has a function of suppressing the diffusion of at least one of oxygen (e.g., oxygen atoms and oxygen molecules) (i.e., the oxygen is less likely to permeate through).

[0229] For example, aluminum oxide or silicon nitride is preferably used for the insulator 214. This can prevent impurities such as water or hydrogen from diffusing from the substrate side of the insulator 214 to the transistor 200 side. Alternatively, it can prevent oxygen contained in the insulator 224 from diffusing from the insulator 214 to the substrate side.

[0230] The insulators 216, 279, and 281, which function as interlayer films, preferably have a lower dielectric constant than the insulator 214. Using a material with a low dielectric constant as the interlayer film can reduce parasitic capacitance between wirings. For example, the insulators 216, 279, and 281 can be formed using silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine has been added, silicon oxide to which carbon has been added, silicon oxide to which carbon and nitrogen have been added, or silicon oxide having vacancies, as appropriate.

[0231] The insulators 222 and 224 function as gate insulators.

[0232] Here, the insulator 224 in contact with the metal oxide 231 preferably releases oxygen by heating. In this specification, oxygen released by heating is sometimes referred to as excess oxygen. For example, the insulator 224 may be formed using silicon oxide or silicon oxynitride as appropriate. By providing an insulator containing oxygen in contact with the metal oxide 231, oxygen vacancies in the metal oxide 231 can be reduced, and the reliability of the transistor 200 can be improved.

[0233] Specifically, an oxide material from which some oxygen is released by heating is preferably used as the insulator 224. The oxide from which oxygen is released by heating is an oxide having an oxygen atom release amount of 1.0×10 in terms of oxygen atoms as determined by TDS (Thermal Desorption Spectroscopy) analysis. １８ atoms / cm ３ or more, preferably 1.0 × 10 １９ atoms / cm ３ More preferably, 2.0 × 10 １９ atoms / cm ３ or more, or 3.0 x 10 ２０ atoms / cm ３ The surface temperature of the film during the TDS analysis is preferably in the range of 100°C or higher and 700°C or lower, or 100°C or higher and 400°C or lower.

[0234] 18C , the thickness of the region of insulator 224 that does not overlap with insulator 254 and metal oxide 231b may be thinner than the thickness of the other region. It is preferable that the thickness of the region of insulator 224 that does not overlap with insulator 254 and metal oxide 231b is a thickness that allows sufficient diffusion of the oxygen.

[0235] Like the insulator 214, the insulator 222 preferably functions as a barrier insulating film that prevents impurities, such as water or hydrogen, from entering the transistor 200 from the substrate side. For example, the insulator 222 preferably has lower hydrogen permeability than the insulator 224. By surrounding the insulator 224, the metal oxide 231, and the insulator 250 with the insulators 222, 254, and 274, impurities, such as water or hydrogen, can be prevented from entering the transistor 200 from the outside.

[0236] Furthermore, the insulator 222 preferably has a function of suppressing the diffusion of at least one of oxygen (e.g., oxygen atoms, oxygen molecules) (i.e., the oxygen is less likely to permeate). For example, the insulator 222 preferably has lower oxygen permeability than the insulator 224. The insulator 222 preferably has a function of suppressing the diffusion of oxygen and impurities, which can reduce the diffusion of oxygen contained in the metal oxide 231 toward the substrate side. Furthermore, the conductor 205 can be prevented from reacting with the oxygen contained in the insulator 224 and the metal oxide 231.

[0237] The insulator 222 may be an insulator containing an oxide of one or both of insulating materials, aluminum and hafnium. Aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used as the insulator containing an oxide of one or both of aluminum and hafnium. When the insulator 222 is formed using such a material, the insulator 222 functions as a layer that suppresses oxygen release from the metal oxide 231 and the intrusion of impurities, such as hydrogen, from the periphery of the transistor 200 into the metal oxide 231.

[0238] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the above insulators.

[0239] The insulator 222 may be made of, for example, aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), or strontium titanate (SrTiO ３ ) or (Ba,Sr)TiO ３ Insulators containing so-called high-k materials such as BST may be used in a single layer or a multilayer configuration. As transistors become smaller and more highly integrated, thinning of the gate insulator can lead to problems with leakage current. By using a high-k material as the insulator that functions as the gate insulator, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0240] The insulator 222 and the insulator 224 may have a stacked structure of two or more layers. In this case, the stacked structures are not limited to those made of the same material, and may be those made of different materials. For example, an insulator similar to the insulator 224 may be provided below the insulator 222.

[0241] The metal oxide 231 includes a metal oxide 231a, a metal oxide 231b on the metal oxide 231a, and a metal oxide 231c on the metal oxide 231b. By providing the metal oxide 231a below the metal oxide 231b, it is possible to suppress the diffusion of impurities from structures formed below the metal oxide 231a to the metal oxide 231b. Furthermore, by providing the metal oxide 231c on the metal oxide 231b, it is possible to suppress the diffusion of impurities from structures formed above the metal oxide 231c to the metal oxide 231b.

[0242] Note that the metal oxide 231 preferably has a stacked structure of multiple oxide layers with different atomic ratios of the metal atoms. For example, when the metal oxide 231 contains at least indium (In) and the element M, it is preferable that the ratio of the number of atoms of the element M contained in the metal oxide 231a to the number of atoms of all elements constituting the metal oxide 231a is higher than the ratio of the number of atoms of the element M contained in the metal oxide 231b to the number of atoms of all elements constituting the metal oxide 231b. It is also preferable that the atomic ratio of the element M contained in the metal oxide 231a to In is higher than the atomic ratio of the element M contained in the metal oxide 231b to In. Here, the metal oxide 231c can be the same as the metal oxide 231a or the metal oxide 231b.

[0243] The energy of the conduction band minimum of the metal oxide 231a and the metal oxide 231c is preferably higher than the energy of the conduction band minimum of the metal oxide 231b. In other words, the electron affinity of the metal oxide 231a and the metal oxide 231c is preferably lower than the electron affinity of the metal oxide 231b. In this case, the metal oxide 231c is preferably a metal oxide that can be used for the metal oxide 231a. Specifically, the ratio of the number of atoms of the element M contained in the metal oxide 231c to the number of atoms of all elements constituting the metal oxide 231c is preferably higher than the ratio of the number of atoms of the element M contained in the metal oxide 231b to the number of atoms of all elements constituting the metal oxide 231b. Furthermore, the atomic ratio of the element M contained in the metal oxide 231c to In is preferably higher than the atomic ratio of the element M contained in the metal oxide 231b to In.

[0244] Here, the energy level of the conduction band minimum changes smoothly at the junction between the metal oxide 231a, the metal oxide 231b, and the metal oxide 231c. In other words, the energy level of the conduction band minimum at the junction between the metal oxide 231a, the metal oxide 231b, and the metal oxide 231c changes continuously or forms a continuous junction. To achieve this, it is advisable to reduce the defect level density of the mixed layer formed at the interface between the metal oxide 231a and the metal oxide 231b and the interface between the metal oxide 231b and the metal oxide 231c.

[0245] Specifically, the metal oxide 231a and the metal oxide 231b, and the metal oxide 231b and the metal oxide 231c, have a common element other than oxygen (as a main component), thereby forming a mixed layer with a low density of defect levels. For example, when the metal oxide 231b is an In—Ga—Zn oxide, the metal oxide 231a and the metal oxide 231c may be made of an In—Ga—Zn oxide, a Ga—Zn oxide, or gallium oxide. The metal oxide 231c may also have a stacked structure. For example, a stacked structure of an In—Ga—Zn oxide and a Ga—Zn oxide on the In—Ga—Zn oxide, or a stacked structure of an In—Ga—Zn oxide and a gallium oxide on the In—Ga—Zn oxide, may be used. In other words, a stacked structure of an In—Ga—Zn oxide and an oxide not containing In may be used as the metal oxide 231c.

[0246] Specifically, the metal oxide 231a may have an atomic ratio of In:Ga:Zn=1:3:4 or 1:1:0.5. The metal oxide 231b may have an atomic ratio of In:Ga:Zn=4:2:3 or 3:1:2. The metal oxide 231c may have an atomic ratio of In:Ga:Zn=1:3:4, In:Ga:Zn=4:2:3, Ga:Zn=2:1, or Ga:Zn=2:5. Specific examples of the metal oxide 231c having a stacked structure include a stacked structure of In:Ga:Zn=4:2:3 [atomic ratio] and Ga:Zn=2:1 [atomic ratio], a stacked structure of In:Ga:Zn=4:2:3 [atomic ratio] and Ga:Zn=2:5 [atomic ratio], and a stacked structure of In:Ga:Zn=4:2:3 [atomic ratio] and gallium oxide.

[0247] In this case, the main carrier path is the metal oxide 231b. By configuring the metal oxide 231a and the metal oxide 231c as described above, the defect state density at the interface between the metal oxide 231a and the metal oxide 231b and at the interface between the metal oxide 231b and the metal oxide 231c can be reduced. This reduces the effect of interface scattering on carrier conduction, allowing the transistor 200 to achieve a high on-state current and high frequency characteristics. Note that when the metal oxide 231c has a stacked structure, in addition to the effect of reducing the defect state density at the interface between the metal oxide 231b and the metal oxide 231c, it is expected that the diffusion of constituent elements of the metal oxide 231c toward the insulator 250 can be suppressed. More specifically, since the metal oxide 231c has a stacked structure and an oxide not containing In is located above the stacked structure, it is possible to suppress In that may diffuse toward the insulator 250. The insulator 250 functions as a gate insulator, and diffusion of In causes poor transistor characteristics. Therefore, by forming the metal oxide 231c into a stacked structure, a highly reliable display device can be provided.

[0248] Conductors 242a and 242b, which function as a source electrode and a drain electrode, are provided on the metal oxide 231b. The conductors 242a and 242b are preferably made of a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, or alloys containing the above metal elements or alloys combining the above metal elements. For example, tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel is preferably used. In addition, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred because they are conductive materials that are resistant to oxidation or materials that maintain their conductivity even when they absorb oxygen.

[0249] By providing the conductors 242a and 242b so as to be in contact with the metal oxide 231, the oxygen concentration may be reduced in the vicinity of the conductors 242a and 242b of the metal oxide 231. Furthermore, a metal compound layer containing the metals contained in the conductors 242a and 242b and components of the metal oxide 231 may be formed in the vicinity of the conductors 242a and 242b of the metal oxide 231. In such a case, the carrier concentration increases in the region of the metal oxide 231 near the conductors 242a and 242b, and the region becomes a low-resistance region.

[0250] Here, the region between the conductor 242a and the conductor 242b is formed to overlap the opening of the insulator 279. This allows the conductor 260 to be arranged in a self-aligned manner between the conductor 242a and the conductor 242b.

[0251] The insulator 250 functions as a gate insulator. The insulator 250 is preferably disposed in contact with the upper surface of the metal oxide 231c. The insulator 250 can be made of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, or silicon oxide having vacancies. Silicon oxide and silicon oxynitride are particularly preferred because they are stable to heat.

[0252] The insulator 250 preferably has a reduced concentration of impurities, such as water or hydrogen, in the insulator 250, similar to the insulator 224. The thickness of the insulator 250 is preferably 1 nm or more and 20 nm or less.

[0253] A metal oxide may be provided between the insulator 250 and the conductor 260. The metal oxide preferably suppresses oxygen diffusion from the insulator 250 to the conductor 260. This makes it possible to suppress oxidation of the conductor 260 due to oxygen in the insulator 250.

[0254] The metal oxide may function as part of the gate insulator. Therefore, when silicon oxide or silicon oxynitride is used for the insulator 250, it is preferable to use a metal oxide that is a high-k material with a high dielectric constant. By forming the gate insulator into a stacked structure of the insulator 250 and the metal oxide, a stacked structure that is stable against heat and has a high dielectric constant can be obtained. Therefore, it is possible to reduce the gate potential applied during transistor operation while maintaining the physical thickness of the gate insulator. In addition, it is possible to reduce the equivalent oxide thickness (EOT) of the insulator that functions as the gate insulator.

[0255] Specifically, metal oxides containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, and magnesium can be used. In particular, it is preferable to use aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate), which is an insulator containing an oxide of either or both aluminum and hafnium.

[0256] Although the conductor 260 is shown as having a two-layer structure in FIG. 18, it may have a single-layer structure or a laminated structure of three or more layers.

[0257] The conductor 260a is a material containing the above-mentioned hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, and nitrogen oxide molecules (N ２ O, NO, NO ２ It is preferable to use a conductor that has the function of suppressing the diffusion of impurities, such as copper atoms, or a conductive material that has the function of suppressing the diffusion of oxygen (oxygen atoms or oxygen molecules).

[0258] The conductor 260a has a function of suppressing oxygen diffusion, which can suppress a decrease in conductivity due to oxidation of the conductor 260b caused by oxygen contained in the insulator 250. As a conductive material having a function of suppressing oxygen diffusion, it is preferable to use, for example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide.

[0259] The conductor 260b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. Furthermore, since the conductor 260 also functions as wiring, it is preferable to use a conductor with high conductivity. For example, a conductive material containing tungsten, copper, or aluminum as a main component can be used. Furthermore, the conductor 260b may have a layered structure, such as a layered structure of titanium or titanium nitride and the above-mentioned conductive material.

[0260] 18A and 18C , in a region of the metal oxide 231b that does not overlap with the conductors 242a and 242b, in other words, in the channel formation region of the metal oxide 231, the side surfaces of the metal oxide 231 are arranged to be covered with the conductor 260. This makes it easier for the electric field of the conductor 260, which functions as the first gate electrode, to act on the side surfaces of the metal oxide 231. This increases the on-state current of the transistor 200 and improves its frequency characteristics.

[0261] Like the insulator 214, the insulator 254 preferably functions as a barrier insulating film that prevents impurities, such as water or hydrogen, from entering the transistor 200 from the insulator 279 side. For example, the insulator 254 preferably has lower hydrogen permeability than the insulator 224. Furthermore, as shown in FIGS. 18B and 18C , the insulator 254 preferably contacts the side surface of the metal oxide 231c, the top and side surfaces of the conductor 242a, the top and side surfaces of the conductor 242b, the side surfaces of the metal oxide 231a and the metal oxide 231b, and the top surface of the insulator 224. This structure prevents hydrogen contained in the insulator 279 from entering the metal oxide 231 from the top or side surfaces of the conductor 242a, the conductor 242b, the metal oxide 231a, the metal oxide 231b, and the insulator 224.

[0262] Furthermore, the insulator 254 preferably has a function of suppressing the diffusion of oxygen (oxygen atoms or oxygen molecules) (i.e., the oxygen is less likely to permeate). For example, the insulator 254 preferably has lower oxygen permeability than the insulator 279 or the insulator 224.

[0263] The insulator 254 is preferably formed by a sputtering method. By forming the insulator 254 by a sputtering method in an oxygen-containing atmosphere, oxygen can be added to the insulator 224 near a region in contact with the insulator 254. This allows oxygen to be supplied from this region into the metal oxide 231 through the insulator 224. The insulator 254 has a function of suppressing upward oxygen diffusion, thereby preventing oxygen from diffusing from the metal oxide 231 to the insulator 279. The insulator 222 has a function of suppressing downward oxygen diffusion, thereby preventing oxygen from diffusing from the metal oxide 231 toward the substrate. In this manner, oxygen is supplied to the channel formation region of the metal oxide 231. This reduces oxygen vacancies in the metal oxide 231 and suppresses the transistor from becoming normally on.

[0264] For example, an insulator containing an oxide of one or both of aluminum and hafnium may be formed as the insulator 254. Note that aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used as the insulator containing an oxide of one or both of aluminum and hafnium.

[0265] The insulator 224, the insulator 250, and the metal oxide 231 are covered with the insulator 254, which has a barrier property against hydrogen, and thus the insulator 279 is separated from the insulator 224, the metal oxide 231, and the insulator 250 by the insulator 254. This prevents impurities, such as hydrogen, from penetrating from the outside of the transistor 200, thereby providing the transistor 200 with good electrical characteristics and reliability.

[0266] The insulator 279 is provided over the insulator 224, the metal oxide 231, the conductor 242a, and the conductor 242b with the insulator 254 interposed therebetween. For example, the insulator 279 preferably includes silicon oxide, silicon oxynitride, silicon nitride oxide, silicon oxide to which fluorine has been added, silicon oxide to which carbon has been added, silicon oxide to which carbon and nitrogen have been added, or silicon oxide having vacancies. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, materials such as silicon oxide, silicon oxynitride, and silicon oxide having vacancies are preferable because they can easily form a region containing oxygen that is released by heating.

[0267] It is preferable to reduce the concentration of impurities, such as water or hydrogen, in the insulator 279. The top surface of the insulator 279 may be planarized.

[0268] Similar to the insulator 214, the insulator 274 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the insulator 279 from above. As the insulator 274, for example, an insulator that can be used for the insulator 214 and the insulator 254 may be used.

[0269] An insulator 281 functioning as an interlayer film is preferably provided over the insulator 274. Like the insulator 224, the insulator 281 preferably has a reduced impurity concentration, typically water or hydrogen.

[0270] The conductor 245a and the conductor 245b are arranged in openings formed in the insulator 281, the insulator 274, the insulator 279, and the insulator 254. The conductor 245a and the conductor 245b are provided opposite each other with the conductor 260 interposed therebetween. Note that the height of the upper surfaces of the conductor 245a and the conductor 245b may be flush with the upper surface of the insulator 281.

[0271] Note that insulator 241a is provided in contact with the inner walls of the openings of insulators 281, 274, 279, and 254, and a first conductor of conductor 245a is formed in contact with the side surface of insulator 241a. Conductor 242a is located on at least a portion of the bottom of the openings, and conductor 245a is in contact with conductor 242a. Similarly, insulator 241b is provided in contact with the inner walls of the openings of insulators 281, 274, 279, and 254, and a first conductor of conductor 245b is formed in contact with the side surface of insulator 241b. Conductor 242b is located on at least a portion of the bottom of the openings, and conductor 245b is in contact with conductor 242b.

[0272] The conductors 245a and 245b are preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductors 245a and 245b may have a layered structure.

[0273] When the conductors 242a and 242b have a layered structure, it is preferable to use the above-mentioned conductors that have the function of suppressing the diffusion of impurities, such as water or hydrogen, for the conductors in contact with the metal oxide 231a, the metal oxide 231b, the conductors 242a and 242b, the insulators 254, 279, 274, and 281. For example, it is preferable to use tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or ruthenium oxide. Furthermore, conductive materials that have the function of suppressing the diffusion of impurities, such as water or hydrogen, may be used in a single layer or a layered structure. Using such conductive materials can suppress the absorption of oxygen added to the insulator 279 by the conductors 245a and 245b. Furthermore, it is possible to suppress the intrusion of impurities, such as water or hydrogen, from layers above the insulator 281 into the metal oxide 231 through the conductors 245a and 245b.

[0274] The insulators 241a and 241b may be, for example, an insulator that can be used for the insulator 254. The insulators 241a and 241b are provided in contact with the insulator 254, and therefore can prevent impurities such as water or hydrogen from the insulator 279 from being mixed into the metal oxide 231 through the conductors 245a and 245b. Furthermore, oxygen contained in the insulator 279 can be prevented from being absorbed by the conductors 245a and 245b.

[0275] Although not shown, a conductor functioning as wiring may be disposed in contact with the upper surface of the conductor 245a and the upper surface of the conductor 245b. The conductor functioning as wiring is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor may also have a layered structure, for example, a layered structure of titanium or titanium nitride and the above-mentioned conductive material. The conductor may be formed so as to be embedded in an opening provided in an insulator.

[0276] <Constituent Materials of Transistor> Constituent materials that can be used for the transistor will be described.

[0277] [Substrate] The substrate on which the transistor 200 is formed may be, for example, an insulating substrate, a semiconductor substrate, or a conductive substrate. Examples of insulating substrates include glass substrates, quartz substrates, sapphire substrates, stabilized zirconia substrates (yttria-stabilized zirconia substrates), and resin substrates. Examples of semiconductor substrates include semiconductor substrates of silicon or germanium, or compound semiconductor substrates made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, and gallium oxide. Examples of semiconductor substrates include those having an insulating region within the semiconductor substrate, such as an SOI (Silicon-On-Insulator) substrate. Examples of conductive substrates include graphite substrates, metal substrates, alloy substrates, and conductive resin substrates. Examples of substrates include substrates having a metal nitride and substrates having a metal oxide. Examples of substrates include an insulating substrate with a conductor or semiconductor provided thereon, a semiconductor substrate with a conductor or insulator provided thereon, and a conductive substrate with a semiconductor or insulator provided thereon. Alternatively, a substrate provided with elements may be used, such as a capacitor element, a resistor element, a switch element, a light-emitting element, and a memory element.

[0278] [Insulator] Examples of insulators include oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, and metal nitride oxides, all of which have insulating properties.

[0279] For example, as transistors become more miniaturized and highly integrated, thinning of the gate insulator can cause leakage current problems. Using a high-k material for the insulator that functions as the gate insulator allows for lower voltage operation of the transistor while maintaining the physical film thickness. On the other hand, using a material with a low dielectric constant for the insulator that functions as the interlayer film can reduce the parasitic capacitance that occurs between wiring. Therefore, it is advisable to select a material depending on the function of the insulator.

[0280] Insulators with a high dielectric constant include gallium oxide, hafnium oxide, zirconium oxide, oxides having aluminum and hafnium, oxynitrides having aluminum and hafnium, oxides having silicon and hafnium, oxynitrides having silicon and hafnium, or nitrides having silicon and hafnium.

[0281] Insulators with a low dielectric constant include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, silicon oxide having voids, and resin.

[0282] The electrical characteristics of a transistor including an oxide semiconductor can be stabilized by surrounding the transistor with insulators (insulator 214, insulator 222, insulator 254, and insulator 274) that have a function of suppressing permeation of impurities (typified by hydrogen) and oxygen. Examples of insulators that have a function of suppressing permeation of impurities (typified by hydrogen) and oxygen include, for example, insulators containing boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, and tantalum, which may be used in a single layer or a stacked layer. Specifically, examples of insulators that have a function of suppressing permeation of impurities (typified by hydrogen) and oxygen include metal oxides typified by aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, and tantalum oxide, and metal nitrides typified by aluminum nitride, aluminum titanium nitride, titanium nitride, silicon nitride oxide, and silicon nitride.

[0283] The insulator functioning as the gate insulator is preferably an insulator having a region containing oxygen that is released by heating. For example, by using a structure in which silicon oxide or silicon oxynitride having a region containing oxygen that is released by heating is in contact with the metal oxide 231, oxygen vacancies in the metal oxide 231 can be compensated for.

[0284] [Conductor] As the conductor, it is preferable to use a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, or an alloy containing the above metal elements as a component, or an alloy combining the above metal elements. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel. Furthermore, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred because they are conductive materials that are resistant to oxidation or maintain conductivity even when absorbing oxygen. Furthermore, a semiconductor with high electrical conductivity, typified by polycrystalline silicon containing an impurity element typified by phosphorus, or a silicide such as nickel silicide may also be used.

[0285] A plurality of conductors formed from the above materials may be stacked. For example, a stacked structure may be formed by combining the above-mentioned material containing a metal element and a conductive material containing oxygen. A stacked structure may also be formed by combining the above-mentioned material containing a metal element and a conductive material containing nitrogen. A stacked structure may also be formed by combining the above-mentioned material containing a metal element, a conductive material containing oxygen, and a conductive material containing nitrogen.

[0286] When a metal oxide is used for the channel formation region of a transistor, a conductor functioning as a gate electrode preferably has a stacked structure of a combination of a material containing the metal element and a conductive material containing oxygen. In this case, the conductive material containing oxygen is preferably provided on the channel formation region side. By providing the conductive material containing oxygen on the channel formation region side, oxygen released from the conductive material is easily supplied to the channel formation region.

[0287] In particular, it is preferable to use a conductive material containing oxygen and the metal element contained in the metal oxide in which the channel is formed as a conductor functioning as a gate electrode. Alternatively, a conductive material containing the aforementioned metal element and nitrogen may be used. For example, titanium nitride or a conductive material containing nitrogen such as titanium nitride may be used. Alternatively, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, or indium tin oxide doped with silicon may be used. Alternatively, indium gallium zinc oxide containing nitrogen may be used. Using such a material may allow hydrogen contained in the metal oxide in which the channel is formed to be captured. Alternatively, hydrogen introduced from an external insulator may be captured.

[0288] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0289] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments.

[0290] Embodiment 6 In this embodiment, a metal oxide (hereinafter also referred to as an oxide semiconductor) that can be used for the OS transistor described in the above embodiment will be described.

[0291] <Classification of Crystal Structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 19A. Fig. 19A is a diagram illustrating classification of crystal structures of oxide semiconductors, typically IGZO (metal oxide containing In, Ga, and Zn).

[0292] As shown in FIG. 19A , oxide semiconductors are broadly classified into "amorphous," "crystalline," and "crystal." Furthermore, "amorphous" includes completely amorphous. Furthermore, "crystalline" includes c-axis-aligned crystalline line (CAAC), nanocrystalline line (nc), and cloud-aligned composite (CAC) (excluding single crystal and polycrystal). The "Crystalline" category excludes single crystal, poly crystal, and completely amorphous. The "Crystal" category includes single crystal and poly crystal.

[0293] The structure within the bold frame shown in Figure 19A is an intermediate state between "Amorphous" and "Crystal" and belongs to a new boundary region (New crystalline phase). In other words, this structure can be described as a structure that is completely different from "Crystal" or the energetically unstable "Amorphous."

[0294] The crystalline structure of the film or substrate can be evaluated using an X-ray diffraction (XRD) spectrum. Here, FIG. 19B shows an XRD spectrum obtained by GIXD (Grazing-Incident XRD) measurement of a CAAC-IGZO film classified as "Crystalline." The GIXD method is also called the thin film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by GIXD measurement shown in FIG. 19B will be simply referred to as the XRD spectrum. The vertical axis in FIG. 19B represents intensity, and the horizontal axis represents 2θ. The composition of the CAAC-IGZO film shown in FIG. 19B is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. The thickness of the CAAC-IGZO film shown in FIG. 19B is 500 nm.

[0295] As shown in Figure 19B, a peak indicating clear crystallinity is detected in the XRD spectrum of the CAAC-IGZO film. Specifically, a peak indicating c-axis orientation is detected near 2θ = 31° in the XRD spectrum of the CAAC-IGZO film. Note that, as shown in Figure 19B, the peak near 2θ = 31° is asymmetric with respect to the angle at which the peak intensity is detected.

[0296] The crystalline structure of the film or substrate can be evaluated by a diffraction pattern (also referred to as a nanobeam electron diffraction pattern) observed by nanobeam electron diffraction (NBED). The diffraction pattern of the CAAC-IGZO film is shown in FIG. 19C. FIG. 19C is a diffraction pattern observed by NBED, in which an electron beam is incident parallel to the substrate. The composition of the CAAC-IGZO film shown in FIG. 19C is near In:Ga:Zn = 4:2:3 [atomic ratio]. In the nanobeam electron diffraction method, electron beam diffraction is performed using a probe diameter of 1 nm.

[0297] As shown in FIG. 19C, multiple spots indicating c-axis orientation are observed in the diffraction pattern of the CAAC-IGZO film.

[0298] [Structure of Oxide Semiconductor] Note that oxide semiconductors may be classified differently from those shown in FIG. 19A when focusing on their crystal structures. For example, oxide semiconductors are classified into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include the above-mentioned CAAC-OS and nc-OS. Non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, pseudo-amorphous-like oxide semiconductors (a-like OSs), and amorphous oxide semiconductors.

[0299] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0300] [CAAC-OS] A CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction refers to the thickness direction of the CAAC-OS film, the normal direction to the surface where the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region having periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region is also a region with a uniform lattice arrangement. Furthermore, a CAAC-OS has a region where multiple crystalline regions are connected in the a-b plane direction, and the region may have distortion. Note that distortion refers to a portion where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with another uniform lattice arrangement in a region where multiple crystalline regions are connected. In other words, a CAAC-OS is an oxide semiconductor whose c-axes are aligned and whose orientation is not clearly aligned in the a-b plane direction.

[0301] Each of the multiple crystalline regions is composed of one or more minute crystals (crystals with a maximum diameter of less than 10 nm). When a crystalline region is composed of a single minute crystal, the maximum diameter of the crystalline region is less than 10 nm. When a crystalline region is composed of many minute crystals, the size of the crystalline region may be several tens of nanometers.

[0302] In an In-M-Zn oxide (wherein the element M is one or more elements selected from aluminum, gallium, yttrium, tin, and titanium), the CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter referred to as an In layer) and a layer containing the element M, zinc (Zn), and oxygen (hereinafter referred to as an (M, Zn) layer) are stacked. Note that indium and the element M are mutually substituted. Therefore, the (M, Zn) layer may contain indium. The In layer may contain the element M. The In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution TEM image, for example.

[0303] When a CAAC-OS film is subjected to structural analysis using an XRD apparatus, for example, a peak indicating c-axis orientation is detected at or near 2θ = 31° in out-of-plane XRD measurement using θ / 2θ scanning. Note that the position of the peak indicating c-axis orientation (the value of 2θ) may vary depending on the type and composition of metal elements constituting the CAAC-OS.

[0304] For example, multiple bright spots are observed in the electron diffraction pattern of a CAAC-OS film, and the spots are observed at positions that are point-symmetric with respect to a spot of an incident electron beam that has passed through the sample (also referred to as a direct spot).

[0305] When a crystalline region is observed from the specific direction, the lattice arrangement in the crystalline region is basically a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be a non-regular hexagon. The distortion may have a pentagonal or heptagonal lattice arrangement. In the CAAC-OS, no clear grain boundary can be identified even near the distortion. This indicates that the distortion in the lattice arrangement suppresses the formation of grain boundaries. This is thought to be because the CAAC-OS can tolerate distortion due to the lack of close-packed arrangement of oxygen atoms in the a-b plane and the change in interatomic bond distance caused by substitution of metal atoms.

[0306] Note that a crystal structure in which clear grain boundaries are observed is called polycrystalline. The grain boundaries act as recombination centers, and are likely to trap carriers, resulting in a decrease in the on-state current or a decrease in field-effect mobility of a transistor. Therefore, CAAC-OS, in which clear grain boundaries are not observed, is one of the crystalline oxides having a crystal structure suitable for a semiconductor layer of a transistor. Note that a structure containing Zn is preferable for forming a CAAC-OS. For example, In—Zn oxide and In—Ga—Zn oxide are suitable because they can suppress the generation of grain boundaries more effectively than In oxide.

[0307] CAAC-OS is an oxide semiconductor with high crystallinity and no clear crystal grain boundaries. Therefore, it can be said that the CAAC-OS is less susceptible to a decrease in electron mobility due to crystal grain boundaries. Furthermore, since the crystallinity of an oxide semiconductor can be reduced by the inclusion of impurities and / or the generation of defects, the CAAC-OS can also be said to be an oxide semiconductor with few impurities and defects (oxygen vacancies). Therefore, an oxide semiconductor having a CAAC-OS has stable physical properties. Therefore, an oxide semiconductor having a CAAC-OS is heat-resistant and highly reliable. Furthermore, the CAAC-OS is stable even against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, using a CAAC-OS for an OS transistor can increase the flexibility of the manufacturing process.

[0308] [nc-OS] The nc-OS has periodic atomic arrangement in a microscopic region (e.g., a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has microcrystals. Note that the size of the microcrystals is, for example, 1 nm to 10 nm, particularly 1 nm to 3 nm, and therefore the microcrystals are also called nanocrystals. Furthermore, the nc-OS does not exhibit regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is observed throughout the film. Therefore, depending on the analysis method, the nc-OS may be indistinguishable from an a-like OS and an amorphous oxide semiconductor. For example, when a structural analysis of an nc-OS film is performed using an XRD apparatus, no peak indicating crystallinity is detected in out-of-plane XRD measurement using θ / 2θ scanning. When an nc-OS film is subjected to electron diffraction (also referred to as selected-area electron diffraction) using an electron beam with a probe diameter larger than that of a nanocrystal (e.g., 50 nm or more), a diffraction pattern resembling a halo pattern is observed. On the other hand, when an nc-OS film is subjected to electron diffraction (also referred to as nanobeam electron diffraction) using an electron beam with a probe diameter close to or smaller than that of a nanocrystal (e.g., 1 nm to 30 nm), an electron diffraction pattern in which multiple spots are observed within a ring-shaped region centered on a direct spot may be obtained.

[0309] [a-Like OS] The a-like OS is an oxide semiconductor having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and the CAAC-OS. Furthermore, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and the CAAC-OS.

[0310] [Structure of Oxide Semiconductor] Next, the above-described CAC-OS will be described in detail. Note that the CAC-OS relates to a material structure.

[0311] [CAC-OS] CAC-OS is, for example, a material in which elements constituting a metal oxide are unevenly distributed in a size of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof. Note that hereinafter, a state in which one or more metal elements are unevenly distributed in a metal oxide and regions containing the metal elements are mixed in a size of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof, is also referred to as a mosaic or patch state.

[0312] Furthermore, the CAC-OS has a mosaic structure in which a material is separated into a first region and a second region, and the first region is distributed throughout the film (hereinafter also referred to as a cloud structure). That is, the CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed.

[0313] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In—Ga—Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In—Ga—Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0314] Specifically, the first region is a region whose main component is indium oxide or indium zinc oxide. The second region is a region whose main component is gallium oxide or gallium zinc oxide. In other words, the first region can be referred to as a region whose main component is In. The second region can be referred to as a region whose main component is Ga.

[0315] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0316] For example, in the case of CAC-OS in an In—Ga—Zn oxide, EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) can confirm that the CAC-OS has a structure in which a region containing In as a main component (first region) and a region containing Ga as a main component (second region) are unevenly distributed and mixed.

[0317] When a CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act complementarily, thereby providing the CAC-OS with a switching function (a function of turning on / off). That is, a CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and functions as a semiconductor as a whole. By separating the conductive function and the insulating function, both functions can be maximized. Therefore, by using a CAC-OS in a transistor, a high on-current (I ｏｎ ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0318] Oxide semiconductors have a variety of structures, each of which has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0319] <Transistor Having Oxide Semiconductor> Next, a case where the oxide semiconductor is used for a transistor will be described.

[0320] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0321] For the transistor, an oxide semiconductor having a low carrier concentration is preferably used. For example, the carrier concentration of the oxide semiconductor is 1×10 １７ cm −３ Below 1 × 10, preferably １５ cm −３ More preferably, 1×10 １３ cm −３ Less than 1×10, more preferably 1×10 １１ cm −３ More preferably, 1×10 １０ cm −３ is less than 1×10 −９ cm −３The above is the case. Note that in order to reduce the carrier concentration of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification, a semiconductor having a low impurity concentration and a low density of defect states is referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor. Note that an oxide semiconductor having a low carrier concentration may also be referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor.

[0322] A highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore, the density of trap states may also be low.

[0323] Charges trapped in the trap states of an oxide semiconductor take a long time to dissipate and may behave like fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0324] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. Furthermore, in order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the adjacent film. Impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0325] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0326] When an oxide semiconductor contains silicon and / or carbon, which are elements of Group 14, defect levels are formed in the oxide semiconductor. Therefore, the concentrations of silicon and carbon in the oxide semiconductor and those in the vicinity of the interface with the oxide semiconductor (concentrations obtained by SIMS) are calculated to be 2×10 １８ atoms / cm ３ Below 2 × 10, preferably １７ atoms / cm ３ The following applies.

[0327] When an oxide semiconductor contains an alkali metal or an alkaline earth metal, defect levels may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal is likely to have normally-on characteristics. For this reason, when the concentration of the alkali metal or the alkaline earth metal in the oxide semiconductor obtained by SIMS is 1×10 １８ atoms / cm ３ Below 2 × 10, preferably １６ atoms / cm ３ Do the following:

[0328] When nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Alternatively, when nitrogen is contained in an oxide semiconductor, trap states may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in the oxide semiconductor obtained by SIMS is measured to be 5×10 １９ atoms / cm ３ Less than 5×10 １８ atoms / cm ３ Less than 1×10, more preferably 1×10 １８ atoms / cm ３ or less, more preferably 5 × 10 １７ atoms / cm ３ Do the following:

[0329] Hydrogen contained in an oxide semiconductor reacts with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. Hydrogen entering the oxygen vacancy may generate electrons as carriers. Furthermore, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. Therefore, it is preferable to reduce the amount of hydrogen in the oxide semiconductor as much as possible. Specifically, the hydrogen concentration in the oxide semiconductor measured by SIMS is 1×10 ２０ atoms / cm ３ less than 1×10１９ atoms / cm ３ less than 5×10 １８ atoms / cm ３ less than 1×10 １８ atoms / cm ３ Make it less than.

[0330] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0331] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments.

[0332] 10: Layer, 20: Layer, 30: Layer, 31: Housing, 32: Opening, 34: Fixing device, 35a: Optical member, 35b: Optical member, 36a: Frame, 36b: Frame, 37: Battery, 40: Sealing substrate, 60: Layer, 61: Light-emitting element, 61B: Light-emitting element, 61G: Light-emitting element, 61R: Light-emitting element, 61W: Light-emitting element, 80: Electronic device, 81: User, 91: External camera, 92: Battery, 100A: Semiconductor device, 100B: Semiconductor device, 100C: Semiconductor device, 100D: Semiconductor device, 100G: Semiconductor device, 103: Housing, 104: Light source, 105: Protective member, 130 B: light-emitting element, 130G: light-emitting element, 130R: light-emitting element, 200: transistor, 205: conductor, 205a: conductor, 205b: conductor, 205c: conductor, 214: insulator, 216: insulator, 222: insulator, 224: insulator, 231: metal oxide, 231a: metal oxide, 231b: metal oxide, 231c: metal oxide, 241a: insulator, 241b: insulator, 242a: conductor, 242b: conductor, 245a: conductor, 245b: conductor, 250: insulator, 251: insulating layer, 254: insulator, 260: conductor, 260a: conductor, 260b: conductor conductor, 264B: colored layer, 264G: colored layer, 264R: colored layer, 271: protective layer, 272: insulating layer, 273: protective layer, 274: insulator, 275: gap, 276: insulating layer, 277: microlens array, 279: insulator, 280: display panel, 280L: display panel, 280R: display panel, 281: insulator, 282: circuit section, 283: pixel circuit section, 283a: pixel circuit, 284: pixel section, 284a: pixel, 284b: pixel section, 284c: pixel section, 285: terminal section, 286: wiring section, 290: FPC, 291: substrate, 292: substrate, 301a: conductor, 301b: conductor, 311: conductor, 313: conductor, 321: lower electrode, 323: insulator, 325: upper electrode, 331: conductor, 333: conductor, 335: conductor, 341: conductor, 343: conductor, 347: conductor, 348: conductor, 351: conductor, 353: conductor, 355: conductor, 357: conductor, 361: insulator, 363: insulator, 400C: display device, 403: element isolation layer, 405: insulator, 407: insulator, 409: insulator, 411: insulator, 421: insulator, 422: insulator, 423: insulator, 424: insulator, 430a: light emitting element,430b: light-emitting element, 430c: light-emitting element, 431: transistor, 441: transistor, 442: transistor, 443: conductor, 445: insulator, 447: semiconductor region, 449a: low-resistance region, 449b: low-resistance region, 451: conductor, 453: conductor, 454: bump, 455: conductor, 456: conductor, 457: adhesive layer, 458: bump, 459: adhesive layer, 461: conductor, 462: conductor, 465: conductor, 701: substrate, 702: substrate, 712: sealing material, 716: FPC, 730: insulator, 732: filling layer, 734: insulator, 736: colored layer, 738: light-shielding layer, 750: transistor, 760: conductor, 772: conductor Conductor, 778: structure, 780: anisotropic conductor, 786: EL layer, 786a: EL layer, 786b: EL layer, 786B: EL layer, 786G: EL layer, 786R: EL layer, 786W: EL layer, 788: conductor, 790: capacitor, 941: retina, 942: lens, 943: optic nerve, 944: optic disc, 945: vein, 946 : artery, 947: vitreous body, 948: choroid, 950: optical system, 951: luminescence, 951B: light, 951G: light, 951IR: luminescence, 951R: light, 4411: luminescent layer, 4412: luminescent layer, 4413: luminescent layer, 4420: layer, 4420-1: layer, 4420-2: layer, 4430: layer, 4430-1: layer, 4430-2: layer,

Claims

1. An electronic device that is worn on the user's head, a display device in which a plurality of pixels are arranged, each pixel including a transistor, a first light-emitting element, a second light-emitting element having a function of emitting infrared light, a first light-receiving element, and a second light-receiving element having a function of receiving infrared light; the display device has a function of displaying an image by using the first light-emitting element, the display device has a function of detecting brightness around the eye by using the first light receiving element before photographing the fundus of the user, the display device has a function of photographing an image of the fundus of the user by using the second light-emitting element and the second light-receiving element. electronic equipment.

2. In claim 1, The first light-emitting element is an organic light-emitting element. electronic equipment.

3. In claim 1 or 2, The semiconductor layer of the transistor comprises single crystal silicon. electronic equipment.

4. In any one of claims 1 to 3, the semiconductor layer of the transistor contains an oxide semiconductor; electronic equipment.

5. In any one of claims 1 to 4, Diagnosing the eye of the user by imaging the eye. electronic equipment.