Display device and electronic apparatus

Abstract

Provided is a display device having a high display quality. Provided is a high-definition display device. Provided is a mobile body having a display device and a camera. Provided is an electronic apparatus having a display device and a camera. Provided is a display device having pixels including first sub-pixels and second sub-pixels. The first sub-pixels display a first color and have a first dielectric multilayer film, a first electrode on the first dielectric multilayer film, a first EL layer on the first electrode, and a common electrode on the first EL layer. The second sub-pixels display a second color different from the first color, and have a second electrode, a second EL layer on the second electrode, and a common electrode on the second EL layer. The first sub-pixels have the function of transmitting light including the second color.

Description

Display device and electronic device

[0001] One aspect of the present invention relates to a display device.

[0002] One embodiment of the present invention is not limited to the above technical field, and examples of the technical field of one embodiment of the present invention include semiconductor devices, display devices, light-emitting devices, power storage devices, memory devices, electronic devices, lighting devices, input devices (e.g., touch sensors), input / output devices (e.g., touch panels), driving methods thereof, and manufacturing methods thereof.

[0003] In recent years, display devices have been applied to a variety of purposes, and are widely used in smartphones, tablet terminals, and the like. Many mobile terminals, such as smartphones, are equipped with a front camera (on the display surface side) and a rear camera (on the opposite side of the display surface). The front camera is often used to take photos of the user himself / herself as the subject.

[0004] Until now, front cameras have generally been installed outside the display unit, but due to the demand for narrower bezels on mobile devices, they are increasingly being installed near or within the display unit. For example, known methods include the notch method, in which a camera is placed over an area cut out of a part of the display unit, the punch-hole method, in which a hole is made in the display unit and the camera is placed over the hole, and the under-display camera method, in which the camera is placed over the display unit.

[0005] In the under-display camera method, images are captured by taking in light that passes through between pixels. For example, Patent Literature 1 discloses a method of obtaining high-quality images by providing hole regions between pixels that allow external light to pass through and processing low-quality images obtained through the hole regions.

[0006] JP 2022-41886 A

[0007] Takashi Koida, "High Mobility Transparent Conductive Film," National Institute of Advanced Industrial Science and Technology, AIST Photovoltaic Power Generation Research Results Report 2019, Internet <URL: https: / / unit.aist.go.jp / rpd-envene / PV / ja / results / 2019 / oral / T13.pdf>

[0008] An object of one embodiment of the present invention is to provide a display device with high display quality. Alternatively, an object of one embodiment of the present invention is to provide a display device with high definition.

[0009] Another object of one embodiment of the present invention is to provide a display device suitable for an under-display camera system. Another object is to provide a display device in which a region of a display unit overlapping with a camera is less visible. Another object is to provide a display device with low power consumption. Another object is to provide a display device with high luminance. Another object is to provide a display device with high reliability. Another object is to provide a novel display device. Another object is to provide an electronic device including the display device. Another object is to provide a mobile object including the display device. Another object is to provide an electronic device including a display device and a camera with high imaging sensitivity. Another object is to provide a mobile object including a display device and a camera with high imaging sensitivity. Another object is to provide a novel electronic device. Another object is to provide a novel mobile object.

[0010] Note that the description of these problems does not preclude the existence of other problems. One embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than these can be extracted from the description in the specification, drawings, and claims.

[0011] One embodiment of the present invention is a display device including a pixel having a first subpixel that displays a first color and a second subpixel that displays a second color, the second color being different from the first color; the first subpixel having a first dielectric multilayer film, a first electrode on the first dielectric multilayer film, a first EL layer on the first electrode, and a common electrode on the first EL layer; the second subpixel having a second electrode, a second EL layer on the second electrode, and a common electrode on the second EL layer; and the first subpixel having a function of transmitting light including the second color.

[0012] In the above aspect, it is preferable that the second subpixel has a second dielectric multilayer film, the second electrode is located on the second dielectric multilayer film, and the second subpixel has a function of transmitting light including the first color.

[0013] In addition, in the above aspect, it is preferable that the pixel has a third sub-pixel that displays a third color, the third color being different from both the first color and the second color, and the first sub-pixel has a function of transmitting light including the third color.

[0014] In the above aspect, it is preferable that the pixel has a third sub-pixel that displays a third color, the third color being different from each of the first color and the second color, the second sub-pixel has a second dielectric multilayer film, the second electrode is located on the second dielectric multilayer film, and the second sub-pixel has a function of transmitting light containing one or more of the first color and the third color.

[0015] In the above aspect, it is preferable that the first color is one selected from red, green, and blue, the second color is one selected from red, green, and blue, and the third color is one selected from red, green, and blue.

[0016] In the above embodiment, the first electrode and the second electrode are preferably conductive layers that transmit visible light.

[0017] In the above aspect, it is preferable that the pixel has a third subpixel that emits infrared light, the second subpixel has a second dielectric multilayer film, the second electrode is located on the second dielectric multilayer film, and one or more of the first subpixel and the second subpixel have a function of transmitting infrared light.

[0018] In addition, in the above aspect, it is preferable that the first dielectric multilayer film has a first layer, a second layer on the first layer, a third layer on the second layer, and a fourth layer on the third layer, the first layer and the third layer having a first material, the second layer and the fourth layer having a second material different from the first material, and the first layer and the third layer having a higher refractive index than the second layer and the fourth layer.

[0019] In the above aspect, the first material preferably includes one or more selected from titanium oxide, aluminum oxide, zirconium oxide, hafnium oxide, tantalum oxide, and silicon nitride.

[0020] In the above aspect, the second material preferably includes one or more selected from silicon oxide, magnesium fluoride, lithium fluoride, sodium fluoride, calcium fluoride, aluminum fluoride, strontium fluoride, and fluorides containing sodium and aluminum.

[0021] In the above aspect, the thickness of the first dielectric multilayer film is preferably 100 nm or more and 3000 nm or less.

[0022] In the above aspect, each of the first subpixel and the second subpixel preferably includes a transistor having a metal oxide in a semiconductor layer.

[0023] Alternatively, one embodiment of the present invention includes a first display portion and a second display portion, the second display portion being surrounded by the first display portion, the first display portion including a first pixel, and the second display portion including a second pixel, the first pixel including a first subpixel that displays a first color and a second subpixel that displays a second color, the second color being different from the first color, the second pixel including a third subpixel that displays the first color and a fourth subpixel that displays the second color, the third subpixel having a function of transmitting light including the second color, and the first subpixel including a first electrode. a first subpixel having a first electrode, a first EL layer on the first electrode, and a common electrode on the first EL layer; a second subpixel having a second electrode, a second EL layer on the second electrode, and a common electrode on the second EL layer, the first electrode and the second electrode having a function of reflecting visible light; a third subpixel having a first dielectric multilayer film, a third electrode on the first dielectric multilayer film, a third EL layer on the third electrode, and a common electrode on the third EL layer; and a fourth subpixel having a fourth electrode, a fourth EL layer on the fourth electrode, and a common electrode on the fourth EL layer.

[0024] In the above embodiment, the third electrode and the fourth electrode are preferably conductive layers that transmit visible light.

[0025] In the above embodiment, each of the first to fourth subpixels preferably includes a transistor having a metal oxide in a semiconductor layer.

[0026] Another embodiment of the present invention is an electronic device including the above-described display device and a camera, in which a second display portion and a lens of the camera overlap with each other, and the camera has a function of capturing an image using light that transmits through the third subpixel.

[0027] Alternatively, one embodiment of the present invention includes a display device and a camera. The display device includes a first display portion and a second display portion. The second display portion is surrounded by the first display portion. The first display portion includes a first pixel. The second display portion includes a second pixel. The first pixel includes a first sub-pixel that displays a first color, a second sub-pixel that displays a second color, and a third sub-pixel that displays a third color. The second color is different from the first color, and the third color is different from the first color and the second color. The second pixel displays the first color. the fourth sub-pixel has a function of transmitting light containing one or more of the second color and the third color, the fifth sub-pixel has a function of transmitting light containing one or more of the first color and the third color, and the sixth sub-pixel has a function of transmitting light containing one or more of the first color and the second color; and the camera has a function of capturing an image using light transmitted through the fourth sub-pixel, the fifth sub-pixel, and the sixth sub-pixel.

[0028] Alternatively, one embodiment of the present invention is an electronic device including a display device and a camera. The display device includes a first display portion and a second display portion. The second display portion is surrounded by the first display portion. The first display portion includes a first pixel. The second display portion includes a second pixel. The first pixel includes a first subpixel that displays a first color and a second subpixel that displays a second color. The second color is different from the first color. The second pixel includes a third subpixel that displays the first color, a fourth subpixel that displays the second color, and a fifth subpixel that emits infrared light. One or more of the third subpixel and the fourth subpixel have a function of transmitting infrared light. The camera has a function of capturing an image using infrared light that transmits through one or more of the third subpixel and the fourth subpixel.

[0029] According to one embodiment of the present invention, a display device with high display quality can be provided.Furthermore, according to one embodiment of the present invention, a display device with high definition can be provided.

[0030] According to one embodiment of the present invention, a display device suitable for an under-display camera system can be provided. Furthermore, a display device in which an area of ​​a display unit overlapping with a camera is less visible can be provided. Furthermore, a display device with low power consumption can be provided. Furthermore, a display device with high luminance can be provided. Furthermore, a display device with high reliability can be provided. According to one embodiment of the present invention, a novel display device can be provided. Furthermore, an electronic device including the display device can be provided. Furthermore, a mobile object including the display device can be provided. According to one embodiment of the present invention, an electronic device including a display device and a camera with high imaging sensitivity can be provided. According to one embodiment of the present invention, a mobile object including a display device and a camera with high imaging sensitivity can be provided. According to one embodiment of the present invention, a novel electronic device can be provided. According to one embodiment of the present invention, a novel mobile object can be provided.

[0031] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims.

[0032] FIG. 1A is a diagram illustrating a display device. FIG. 1B is a diagram illustrating a display unit. FIGS. 2A to 2M are diagrams illustrating pixels. FIGS. 3A to 3C are diagrams illustrating pixels. FIGS. 4A to 4C are diagrams illustrating pixels. FIGS. 5A and 5B are diagrams illustrating pixels. FIG. 5C is a diagram illustrating a display device. FIG. 6A is a block diagram illustrating a display device. FIGS. 6B and 6C are diagrams illustrating a pixel circuit. FIGS. 7A to 7C are cross-sectional views illustrating an example of a transistor. FIGS. 8A and 8B are cross-sectional views illustrating an example of a display device. FIG. 9 is a cross-sectional view illustrating an example of a display device. FIG. 10 is a cross-sectional view illustrating an example of a display device. FIGS. 11A and 11B are diagrams illustrating an example of an electronic device. FIG. 11C is a diagram illustrating a camera module. FIGS. 12A to 12E are diagrams illustrating an example of an electronic device. FIG. 12F is a diagram illustrating an example of a moving object. FIGS. 13A and 13B are calculation results showing the characteristics of a dielectric multilayer film. FIGS. 14A and 14B are diagrams illustrating an example of a transistor configuration. 15A to 15C are diagrams illustrating examples of transistor configurations, 16A and 16B are diagrams illustrating the carrier concentration dependence of Hall mobility, and 16C is a cross-sectional view illustrating an indium oxide film.

[0033] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes can be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0034] 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. Furthermore, when referring to similar functions, the same hatching pattern may be used and no particular reference numeral may be assigned.

[0035] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0036] In this specification, the ordinal numbers "first" and "second" are used for convenience and do not limit the number of components or the order of the components (for example, the order of processes or the order of stacking). Furthermore, the ordinal numbers assigned to components in one part of this specification may not match the ordinal numbers assigned to the same components in other parts of this specification or in the claims.

[0037] A transistor is a type of semiconductor element that can amplify current or voltage, and perform a switching operation to control conduction or non-conduction. The term "transistor" as used herein includes an insulated gate field effect transistor (IGFET) and a thin film transistor (TFT).

[0038] In this specification and the like, a transistor using an oxide semiconductor or a metal oxide for a semiconductor layer and a transistor having an oxide semiconductor or a metal oxide for a channel formation region may be referred to as an OS transistor. A transistor having silicon for a channel formation region may be referred to as a Si transistor.

[0039] In this specification and the like, a transistor is an element having at least three terminals including a gate, a drain, and a source. A transistor has a region (also referred to as a channel formation region) where a channel is formed between the drain (drain terminal, drain region, or drain electrode) and the source (source terminal, source region, or source electrode), and current can flow between the source and the drain through the channel formation region. Note that in this specification and the like, the channel formation region refers to a region through which current mainly flows.

[0040] Furthermore, the functions of "source" and "drain" may be interchangeable when transistors of different polarities are used, or when the direction of current flow changes during circuit operation, etc. For this reason, the terms "source" and "drain" may be used interchangeably in this specification.

[0041] Note that impurities in a semiconductor refer to, for example, elements other than the main components constituting the semiconductor. For example, an element with a concentration of less than 0.1 atomic % can be considered an impurity. The presence of impurities can, for example, increase the defect state density of the semiconductor or reduce the crystallinity. When the semiconductor is an oxide semiconductor, impurities that change the characteristics of the semiconductor include, for example, Group 1 elements, Group 2 elements, Group 13 elements, Group 14 elements, Group 15 elements, and transition metals other than the main components of the oxide semiconductor. Specific examples include hydrogen, lithium, sodium, silicon, boron, phosphorus, carbon, and nitrogen. Note that water can also function as an impurity. Furthermore, for example, the inclusion of impurities can form oxygen vacancies (also referred to as VO) in the oxide semiconductor.

[0042] In this specification and the like, an oxynitride refers to a material having a composition in which oxygen atoms are more abundant than nitrogen atoms, and a nitride oxide refers to a material having a composition in which nitrogen atoms are more abundant than oxygen atoms.

[0043] To analyze the content of elements such as hydrogen, oxygen, carbon, or nitrogen contained in a film, for example, secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS) can be used. XPS is suitable when the content of the target element is high (e.g., 0.5 atomic% or more, or 1 atomic% or more). On the other hand, SIMS is suitable when the content of the target element is low (e.g., 0.5 atomic% or less, or 1 atomic% or less). When comparing the content of elements, it is more preferable to perform a combined analysis using both SIMS and XPS analytical techniques.

[0044] Note that in this specification and the like, the term "content" refers to the proportion of a component contained in a film. For example, when an oxide semiconductor layer contains metal element X, metal element Y, and metal element Z, and the numbers of atoms of metal element X, metal element Y, and metal element Z contained in the oxide semiconductor layer are AX, AY, and AZ, respectively, the content of metal element X can be expressed as AX / (AX+AY+AZ). Furthermore, when the ratio of the numbers of atoms of metal element X, metal element Y, and metal element Z in the oxide semiconductor layer (atomic ratio) is expressed as BX:BY:BZ, the content of metal element X can be expressed as BX / (BX+BY+BZ).

[0045] The terms "film" and "layer" can be interchangeable depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film." Or, for example, the term "insulating film" can be changed to the term "insulating layer."

[0046] Furthermore, in this specification, "parallel" refers to a state in which two straight lines are arranged at an angle of -10 degrees or more and 10 degrees or less. Therefore, it also includes cases in which the angle is -5 degrees or more and 5 degrees or less. Furthermore, "substantially parallel" refers to a state in which two straight lines are arranged at an angle of -20 degrees or more and 20 degrees or less. Furthermore, "perpendicular" refers to a state in which two straight lines are arranged at an angle of 80 degrees or more and 100 degrees or less. Therefore, it also includes cases in which the angle is 85 degrees or more and 95 degrees or less. Furthermore, "substantially perpendicular" refers to a state in which two straight lines are arranged at an angle of 70 degrees or more and 110 degrees or less.

[0047] In this specification, "connection" includes, as an example, "electrical connection." Note that the term "electrical connection" is sometimes used to define the connection relationship between circuit elements as an object. Furthermore, "electrical connection" includes "direct connection" and "indirect connection." "A and B are directly connected" means that A and B are connected without the intervention of a circuit element (e.g., a transistor, a switch, etc.; note that wiring is not a circuit element). On the other hand, "A and B are indirectly connected" means that A and B are connected via one or more circuit elements. Note that A and B represent objects such as elements, circuits, wiring, electrodes, terminals, semiconductor layers, and conductive layers.

[0048] For example, assuming that a circuit including A and B is operating, if there is a time during the operation of the circuit when an electrical signal is exchanged or an interaction of electrical potential occurs between A and B, then it can be defined that "A and B are indirectly connected" as objects. Note that even if there is a time during the operation of the circuit when no electrical signal is exchanged or an interaction of electrical potential occurs between A and B, it can still be defined that "A and B are indirectly connected" as long as there is a time during the operation of the circuit when an electrical signal is exchanged or an interaction of electrical potential occurs between A and B.

[0049] An example of a case where "A and B are indirectly connected" is when A and B are connected via the source and drain of one or more transistors. On the other hand, an example of a case where it cannot be said that "A and B are indirectly connected" is when an insulator is present in the path from A to B. Specifically, there are cases where a capacitive element is connected between A and B, and cases where a gate insulating film of a transistor is present between A and B. Therefore, it cannot be said that "the gate (A) of a transistor and the source or drain (B) of the transistor are indirectly connected."

[0050] Another example of a case where it cannot be said that "A and B are indirectly connected" is when multiple transistors are connected via their sources and drains to the path from A to B, and a constant potential V is supplied to a node between one transistor and another transistor from a power supply, GND, etc.

[0051] Unless otherwise specified, in this specification, the off-state current refers to a leakage current between the source and drain 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 refers to a state in which the gate-source voltage Vgs is lower than the threshold voltage Vth for an n-channel transistor (higher than Vth for a p-channel transistor).

[0052] In this specification, the term "normally-on" refers to a state in which a channel exists and a current flows through a transistor even when no voltage is applied to the gate, whereas the term "normally-off" refers to a state in which no current flows through a transistor when no potential is applied to the gate or when a ground potential is applied to the gate.

[0053] In this specification, a tapered shape refers to a shape in which at least a portion of the side surface of a structure is inclined relative to the substrate surface or the surface to be formed. For example, it is preferable to have a region in which the angle (also called the taper angle) between the inclined side surface and the substrate surface or the surface to be formed is greater than 0 degrees and less than 90 degrees. The side surface of the structure, the substrate surface, and the surface to be formed do not necessarily need to be completely flat, and may be approximately planar with a slight curvature or approximately planar with a slight unevenness.

[0054] In this specification, when it is stated that A is located on B, at least a portion of A is located on B. Therefore, for example, it can be rephrased as "A has a region located on B." Similarly, when it is stated that A contacts B or A overlaps B, at least a portion of A contacts B or overlaps B. Therefore, it can be rephrased as "A has a region contacting B" or "A has a region overlapping B," respectively. Similarly, in this specification, when it is stated that A covers B, at least a portion of A covers B. Therefore, for example, it can be rephrased as "A has a region covering B."

[0055] In this specification, etc., 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. Also, in this specification, etc., a device fabricated without using a metal mask or an FMM may be referred to as a device with an MML (metal maskless) structure.

[0056] In this specification and the like, a structure in which different light-emitting layers are formed for light-emitting elements (also referred to as light-emitting devices) with different emission wavelengths is sometimes referred to as an SBS (Side By Side) structure. The SBS structure allows the materials and configuration to be optimized for each light-emitting element, increasing the degree of freedom in selecting materials and configurations and making it easier to improve brightness and reliability.

[0057] In this specification and the like, holes or electrons may be referred to as "carriers." Specifically, a hole injection layer or an electron injection layer may be referred to as a "carrier injection layer," a hole transport layer or an electron transport layer may be referred to as a "carrier transport layer," and a hole block layer or an electron block layer may be referred to as a "carrier block layer." Note that the above-mentioned carrier injection layer, carrier transport layer, and carrier block layer may not be clearly distinguishable. Furthermore, one layer may have two or three functions among the carrier injection layer, carrier transport layer, and carrier block layer.

[0058] In this specification and the like, a light-emitting element has an EL layer between a pair of electrodes. The EL layer has at least a light-emitting layer. Here, examples of layers (also referred to as functional layers) included in the EL layer include a light-emitting layer, a carrier injection layer (a hole injection layer and an electron injection layer), a carrier transport layer (a hole transport layer and an electron transport layer), and a carrier block layer (a hole block layer and an electron block layer). In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode, and the other may be referred to as a common electrode.

[0059] In this specification and the like, the sacrificial layer (which may also be referred to as a mask layer) is located above at least the light-emitting layer (more specifically, the layer that is processed into an island shape among the layers that make up the EL layer), and has the function of protecting the light-emitting layer during the manufacturing process.

[0060] In this specification and the like, a step disconnection refers to a phenomenon in which a layer, a film, or an electrode is separated due to the shape of the surface on which it is formed (for example, a step or the like).

[0061] In the drawings and the like relating to this specification, arrows indicating the X direction, Y direction, and Z direction may be used. In this specification and the like, the "X direction" refers to the direction along the X axis, and there may be no distinction between the forward direction and the reverse direction unless explicitly stated. The same applies to the "Y direction" and the "Z direction." The X direction, Y direction, and Z direction are directions that intersect with each other. For example, the X direction, Y direction, and Z direction are directions that are perpendicular to each other.

[0062] Embodiment 1 In this embodiment, a display device according to one embodiment of the present invention will be described with reference to drawings.

[0063] One embodiment of the present invention is a display device that can be used for an under-display camera type electronic device. The display device includes a first display portion and a second display portion, and the second display portion is surrounded by the first display portion.

[0064] The first pixel included in the first display unit has a plurality of sub-pixels. Each of the plurality of sub-pixels can display a different color. The first pixel has, for example, three sub-pixels, and performs full-color display using red, green, and blue light. The second pixel included in the second display unit has a plurality of sub-pixels. Each of the plurality of sub-pixels can display a different color. The second pixel has, for example, three sub-pixels, and performs full-color display using red, green, and blue light.

[0065] The second display unit is provided so as to overlap with a camera lens. Since one or more sub-pixels of the second pixel have light-transmitting properties, light incident on the second pixel can pass through the light-transmitting sub-pixels and reach the camera. The camera can capture an image via the light-transmitting sub-pixels.

[0066] FIG. 1A is a schematic diagram illustrating the positional relationship between a display device of one embodiment of the present invention and a camera corresponding to a front camera, in which a right side view is shown on the right side of the front view and a plan view (top side view) is shown on the upper side.

[0067] The display device has a display unit 20 between a substrate 41 and a substrate 42. Note that the substrate 42 is not shown in the front view. The display unit 20 has a display unit a and a display unit b, and the display unit b is arranged so as to be surrounded by the display unit a. The display unit b has a configuration that allows light to easily pass through, and has an area that overlaps with the camera 30 via the substrate 41. The display unit b has a configuration that is more translucent than the display unit a.

[0068] The camera 30 is a camera module for a front camera, and has a configuration in which a lens 31 is provided on an image sensor. In order to allow a large amount of light to enter the camera 30, the display unit b is preferably large enough to overlap the entire lens 31 when viewed from the display unit 20 side. In addition, since the lens 31 is circular, it is preferable that the display unit b also be circular or approximately circular.

[0069] An enlarged view of the vicinity of the boundary between display section a and display section b is shown on the left side of the front view, and an example of the pixel configuration is shown in FIG. 1B as a further enlarged view of that view.

[0070] The display unit a has a pixel 10. The pixel 10 has three subpixels: a subpixel that emits red light (R), a subpixel that emits green light (G), and a subpixel that emits blue light (B). In FIG. 1B , the colors of light emitted by each subpixel (R, G, B) are indicated. Within the pixel 10, the colors of light emitted by each subpixel can be interchanged as appropriate. The pixel 10 may also be configured to have three subpixels of yellow (Y), cyan (C), and magenta (M). The pixel 10 may also be configured to have four subpixels of four colors. Examples of the four subpixels of four colors include R, G, B, and white (W) subpixels, and R, G, B, and Y subpixels. The pixel 10 may also have an infrared (IR) subpixel instead of any of the above colors. Alternatively, the pixel 10 may have an IR subpixel in addition to the above subpixels of the above colors.

[0071] In the following description, a subpixel that emits red light (R) may be referred to as subpixel R, a subpixel that emits green light (G) as subpixel G, and a subpixel that emits blue light (B) as subpixel B.

[0072] The display unit b has a pixel 11. The pixel 11 has three sub-pixels: sub-pixel R, sub-pixel G, and sub-pixel B. Note that within the pixel 11, the colors of light emitted by each sub-pixel can be switched as appropriate. The pixel 11 may also be configured to have three sub-pixels of Y, C, and M. The pixel 11 may also be configured to have four sub-pixels of four colors. Examples of the four sub-pixels of four colors include sub-pixels of R, G, B, and white (W), and sub-pixels of R, G, B, and Y.

[0073] One or more of the sub-pixels included in the pixel 11 are translucent. In FIG. 1B , the sub-pixels having translucency are marked with the letter (t). While FIG. 1B shows an example in which the sub-pixels R, G, and B of the pixel 11 are translucent, it is sufficient that at least one of the sub-pixels is translucent. Furthermore, the color of the translucent sub-pixels may differ depending on the pixel.

[0074] In the display device of one embodiment of the present invention, the subpixel R(t) preferably has a function of displaying red and a function of transmitting a complementary color of red (e.g., green and blue, which are complementary colors). Similarly, the subpixel G(t) preferably has a function of displaying green and a function of transmitting a complementary color of green (e.g., red and blue, which are complementary colors). Similarly, the subpixel B(t) preferably has a function of displaying blue and a function of transmitting a complementary color of blue (e.g., red and green, which are complementary colors). When the subpixels R(t), G(t), and B(t) have the above functions, the pixel 11 can have a function of displaying R, G, and B, respectively, and a function of transmitting light corresponding to R, G, and B, respectively, to the camera.

[0075] Here, it is preferable that the number and types of colors used in pixel 11 match the number and types of colors used in pixel 10. It is also preferable that the external size and pitch (the distance between pixels) of pixel 10 and pixel 11 are the same. This allows the display section a and display section b to have the same pixel occupation area and pixel density.

[0076] As described above, the entire display unit 20 can be made to have the same resolution, and the image can be acquired by the camera 30 by utilizing the fact that the display unit b has translucency.

[0077] In this specification, the occupied area of ​​a pixel refers to the area of ​​a region required for appropriately arranging the elements that make up one pixel (e.g., sub-pixels, light-transmitting regions, wiring, etc.), and the pixel density refers to the number of pixels per unit area or unit length.

[0078] 1B shows an example in which the sub-pixels are arranged in a stripe pattern, but the arrangement of the sub-pixels is not particularly limited, and various arrangements can be applied, such as a stripe pattern, an S-stripe pattern, a matrix pattern, a delta pattern, a Bayer pattern, and a pentile pattern.

[0079] Examples of the top surface shape of the subpixel include a triangle, a quadrangle (including a rectangle and a square), a polygon such as a pentagon, a polygon with rounded corners, an ellipse, and a circle.

[0080] 2A to 2M are diagrams each showing an example of an arrangement of sub-pixels.

[0081] 2A is composed of three subpixels: subpixel R, subpixel G, and subpixel B. Subpixel B is arranged across two rows in one column on the left side, and subpixels R and G are arranged in the first and second rows in one column on the right side, respectively.

[0082] 2B includes subpixel R having a generally trapezoidal or triangular top surface shape with rounded corners, subpixel G having a generally trapezoidal or triangular top surface shape with rounded corners, and subpixel B having a generally rectangular or hexagonal top surface shape with rounded corners. Subpixel B has a larger light-emitting area than subpixel G. Subpixel G also has a larger light-emitting area than subpixel R. In this manner, the shape and size of each subpixel can be determined independently. For example, the more reliable the light-emitting device a subpixel has, the smaller its size can be.

[0083] The pixels 10a and 10b shown in Fig. 2C are arranged in a Pentile arrangement, in which pixels 10a having subpixels R and G and pixels 10b having subpixels G and B are arranged alternately.

[0084] 2D are arranged in a delta configuration. Pixel 10a has two subpixels (subpixel R and subpixel G) in the top row (first row) and one subpixel (subpixel B) in the bottom row (second row). Pixel 10b has one subpixel (subpixel B) in the top row (first row) and two subpixels (subpixel R and subpixel G) in the bottom row (second row).

[0085] 2E shows an example in which subpixels of each color are arranged in a zigzag pattern. Specifically, when viewed from above, the positions of the upper sides of two subpixels aligned in the row direction (for example, subpixels R and G, or subpixels G and B) are misaligned.

[0086] In photolithography, the finer the pattern to be processed, the more significant the effect of light diffraction becomes. This reduces the fidelity of the photomask pattern when it is transferred by exposure, making it difficult to process the resist mask into the desired shape. Therefore, even if the photomask pattern is rectangular, it is likely to have rounded corners. As a result, the top surface shape of the subpixel may become a polygon with rounded corners, an ellipse, a circle, or the like.

[0087] Furthermore, in a method for manufacturing a display device according to one embodiment of the present invention, an EL layer or an island-shaped layer formed from a portion of an EL layer is processed into an island shape using a resist mask. The resist film formed on the EL layer or the island-shaped layer formed from a portion of the EL layer needs to be cured at a temperature lower than the heat resistance temperature of the EL layer or the island-shaped layer formed from a portion of the EL layer. Therefore, depending on the heat resistance temperature of the material for the EL layer or the island-shaped layer formed from a portion of the EL layer and the curing temperature of the resist material, the resist film may not be sufficiently cured. An insufficiently cured resist film may have a shape different from the desired shape during processing. As a result, the top surface shape of the EL layer or the island-shaped layer formed from a portion of the EL layer may be a polygon with rounded corners, an ellipse, a circle, or the like. For example, when a resist mask with a square top surface shape is formed, a resist mask with a circular top surface shape may be formed, resulting in a circular top surface shape of the EL layer or the island-shaped layer formed from a portion of the EL layer.

[0088] In order to form the desired shape of the top surface of the EL layer or an island-shaped layer made up of a part of the EL layer, a technique for correcting the mask pattern in advance (OPC (Optical Proximity Correction) technique) may be used so that the design pattern and the transfer pattern coincide with each other. Specifically, the OPC technique adds a correction pattern to the corners of figures on the mask pattern.

[0089] As shown in Figures 2F to 2I, a pixel can be configured to have four types of subpixels. Each pixel 10 shown in Figures 2F to 2I has a subpixel R, a subpixel G, a subpixel B, and a subpixel W. Here, the subpixel W is, for example, a subpixel that displays white.

[0090] The pixel 10 shown in FIG. 2F has a stripe arrangement.

[0091] The pixel 10 shown in FIG. 2G is arranged in a matrix.

[0092] 2H and 2I show an example in which one pixel 10 is configured in two rows and three columns.

[0093] The pixel 10 shown in FIG. 2H has three subpixels (subpixel R, subpixel G, and subpixel B) in the top row (first row) and three subpixels (subpixel W) in the bottom row (second row).

[0094] The pixel 10 shown in FIG. 2I has three subpixels (subpixel R, subpixel G, and subpixel B) in the top row (first row) and one subpixel (subpixel W) in the bottom row (second row).

[0095] 2J, 2K, 2L, and 2M show an example in which the subpixel W in Figures 2F to 2I is replaced with the subpixel I. The subpixel I is, for example, a subpixel that displays infrared light.

[0096] The sub-pixels that display infrared light may, for example, have light-emitting elements that emit infrared light.

[0097] In FIG. 1B and FIGS. 2A to 2I, the colors of light emitted by the sub-pixels can be interchanged as appropriate.

[0098] FIG. 3A is an enlarged view of a part of the display unit 20 of the display device shown in FIG. 1B, showing a pixel 10 of the display unit a on the left side and a pixel 11 of the display unit b on the right side.

[0099] A display device according to one embodiment of the present invention includes a light-emitting device in each pixel. The pixel 10 includes subpixels R, G, and B. The pixel 11 also includes subpixels R, G, and B.

[0100] In the following description, cross-sectional views will be used to explain the subpixels R, G, and B of pixel 10, and the light-transmitting subpixels R, G, and B of pixel 11. Note that, although an example is shown in which the subpixels R, G, and B of pixel 11 are each light-transmitting, it is sufficient that one or more subpixels of pixel 11 are light-transmitting.

[0101] 3B shows a cross-sectional view of the pixel 10 shown in FIG. 3A taken along line X1-X2. As shown in FIG. 3B, an insulating layer is provided on the layer 101, and the light-emitting devices 130a, 130b, and 130c are provided on the insulating layer. A protective layer 131 is also provided to cover the light-emitting devices 130a, 130b, and 130c. A plurality of light-emitting elements are provided between opposing substrates 110 and 120, and the layer 101 is provided on the substrate 110. The layer 101 may include transistors that constitute pixel circuits, etc. The layer 101 may also be formed on the substrate 110 without being separated from the substrate 110.

[0102] Furthermore, in the display device, a colored layer may be provided on the protective layer 131 so as to overlap with the light-emitting device. Here, the colored layer has a function of transmitting light emitted from the light-emitting device and light captured by a camera. For example, when the sub-pixel R displays red, a magenta colored layer can be provided over the protective layer 131. For example, when the sub-pixel G displays green, a yellow colored layer can be provided over the protective layer 131. For example, when the sub-pixel B displays blue, a cyan colored layer can be provided over the protective layer 131. The colored layer can function as a reflection suppressing layer in the display portion of the display device. Here, the colored layer provided over the light-emitting device has a function of transmitting light in a wavelength range that includes both the color displayed by the light-emitting device and the light transmitted through the sub-pixel. Therefore, for example, when a magenta colored layer is provided over the sub-pixel R, red is displayed (reflected) in the sub-pixel R, and the non-red region of the magenta color gamut is transmitted. Note that in the light-emitting device of one embodiment of the present invention, the colored layer and the microcavity effect can be combined to further increase the purity of the color displayed by the sub-pixel.

[0103] The display device may also be configured to include a light-shielding layer. The light-shielding layer may be provided, for example, on the protective layer 131 between adjacent subpixels. The use of the light-shielding layer can prevent light from leaking to adjacent subpixels (stray light). This can improve the display quality of the display device. Furthermore, even without using a light-shielding layer, the insulating layer 127 may be configured to have light-shielding properties, thereby preventing stray light and other problems. Furthermore, the insulating layer 127 having light-shielding properties can function as a layer that suppresses reflection in the display portion of the display device. For example, the insulating layer 127 may be made of a material that absorbs visible light.

[0104] FIG. 3B shows an example in which light emitted from the light emitting device 130a, the light emitting device 130b, and the light emitting device 130c is emitted toward the substrate 120.

[0105] In addition, an insulating layer 125 and an insulating layer 127 on the insulating layer 125 are provided in the region between adjacent light-emitting devices (for example, the light-emitting device 130a and the light-emitting device 130b).

[0106] Figure 3C shows a cross-sectional view of pixel 11 shown in Figure 3A taken along line Y1-Y2. As shown in Figure 3C, an insulating layer is provided on layer 101, and light-emitting devices 130at, 130bt, and 130ct are provided on the insulating layer. In addition, a protective layer 131 is provided to cover light-emitting devices 130at, 130bt, and 130ct. A plurality of light-emitting elements are provided between opposing substrates 110 and 120, and layer 101 is provided on substrate 110.

[0107] As described below, the light-emitting device 130at, the light-emitting device 130bt, and the light-emitting device 130ct each have a light-transmitting configuration in which the pixel electrodes 111at, 111bt, and 111ct are light-transmitting. Furthermore, by providing a layer 115at below the pixel electrode 111at, a layer 115bt below the pixel electrode 111bt, and a layer 115ct below the pixel electrode 111ct, the subpixels in which the respective light-emitting devices are provided can reflect light of desired colors. Furthermore, the layers 115at, 115bt, and 115ct can be dielectric multilayer films. Furthermore, by stacking pixel electrodes and dielectric multilayer films in the light-emitting devices, colors outside the wavelength range of the color displayed by the light-emitting device, such as green and blue when displaying red, can be transmitted. In a display device, the light-emitting and transmissive regions can be combined without providing a transmissive region in addition to the light-emitting region. Therefore, light in the desired wavelength range can be transmitted without reducing the area of ​​the light-emitting region. By using the light-emitting device of one embodiment of the present invention, a display device with a high aperture ratio can be realized.

[0108] Furthermore, in the display device of one embodiment of the present invention, only light in the wavelength range of a color displayed by the subpixel is reflected, thereby reducing reflected light from the display portion. By reducing reflected light, the display quality of the display device can be improved.

[0109] The light transmitted through the sub-pixels of the display device is incident on a camera provided over the display device, and the camera can take an image using the light.

[0110] Furthermore, since the display device according to one embodiment of the present invention uses a dielectric multilayer film, it can transmit only light in a desired wavelength range and reflect the color to be displayed, thereby enabling light emitted from the light-emitting device to be efficiently emitted from the light-emitting device.Furthermore, it can prevent the light emitted from the light-emitting device from entering the camera, thereby reducing noise in imaging.

[0111] By using a light-emitting device having the above structure, the display device of one embodiment of the present invention can suppress a decrease in luminance of a displayed color and transmit light in a desired wavelength range, thereby achieving a display device with high display quality and a long lifetime.

[0112] 3C shows an example in which light emitted from the light-emitting device 130at, the light-emitting device 130bt, and the light-emitting device 130ct is emitted toward the substrate 120. Furthermore, of the light incident on the light-emitting device 130at, the light-emitting device 130bt, and the light-emitting device 130ct from the substrate 120 side, the light that has passed through both the pixel electrode 111at, the pixel electrode 111bt, and the pixel electrode 111ct and the layers 115at, 115bt, and 115ct provided below the respective pixel electrodes is emitted toward the substrate 110.

[0113] A light-emitting device will be described. A display device according to one embodiment of the present invention is a top-emission type that emits light in a direction opposite to a substrate on which a light-emitting device is formed.

[0114] The substrate 110 and the layer 101 over the substrate 110 can have a stacked structure including a plurality of transistors provided over the substrate and an insulating layer covering these transistors. The insulating layer over the transistor is not limited to a single-layer structure, and can also have a stacked structure. Figures 3B and 3C show a stack of insulating layers 255a, 255b, and 255c among the insulating layers over the transistor. The reliability of the transistor can be improved by using a stacked structure for the insulating layer over the transistor.

[0115] The insulating layers 255a, 255b, and 255c can each be suitably formed using various inorganic insulating films such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, and a nitride oxide insulating film. The insulating layers 255a and 255c are preferably formed using an oxide insulating film or an oxynitride insulating film such as a silicon oxide film, a silicon oxynitride film, or an aluminum oxide film. The insulating layer 255b is preferably formed using a nitride insulating film or a nitride oxide insulating film such as a silicon nitride film or a silicon nitride oxide film. More specifically, the insulating layers 255a and 255c are preferably formed using silicon oxide films, and the insulating layer 255b is preferably formed using a silicon nitride film. The insulating layer 255b preferably functions as an etching protective film.

[0116] As the light-emitting device, it is preferable to use an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode). Examples of light-emitting materials that the light-emitting device has include fluorescent materials (fluorescent materials), phosphorescent materials (phosphorescent materials), and materials that exhibit thermally activated delayed fluorescence (thermally activated delayed fluorescence (TADF) materials). As the light-emitting material that the EL element has, not only organic compounds but also inorganic compounds (such as quantum dot materials) can be used. Furthermore, LEDs such as micro LEDs (light-emitting diodes) can also be used as the light-emitting device.

[0117] Of the pair of electrodes that a light-emitting device has, one electrode functions as a cathode and the other electrode functions as an anode. In the following, an example in which the pixel electrode functions as the anode and the common electrode functions as the cathode will be described.

[0118] The light-emitting device 130a has a pixel electrode 111a on an insulating layer 255c, an island-shaped layer 113a on the pixel electrode 111a, a common layer 114 on the layer 113a, and a common electrode 117 on the common layer 114. In the light-emitting device 130a, the layer 113a and the common layer 114 can be collectively referred to as an EL layer.

[0119] The light-emitting device 130b has a pixel electrode 111b on an insulating layer 255c, an island-shaped layer 113b on the pixel electrode 111b, a common layer 114 on the layer 113b, and a common electrode 117 on the common layer 114. In the light-emitting device 130b, the layer 113b and the common layer 114 can be collectively referred to as an EL layer.

[0120] The light-emitting device 130c has a pixel electrode 111c on an insulating layer 255c, an island-shaped layer 113c on the pixel electrode 111c, a common layer 114 on the layer 113c, and a common electrode 117 on the common layer 114. In the light-emitting device 130c, the layer 113c and the common layer 114 can be collectively referred to as an EL layer.

[0121] The light-emitting device 130at differs from the light-emitting device 130a in that it has a pixel electrode 111at instead of the pixel electrode 111a, and in that it has a layer 115at between the insulating layer 255c and the pixel electrode 111at.

[0122] The light-emitting device 130bt differs from the light-emitting device 130b in that it has a pixel electrode 111bt instead of the pixel electrode 111b, and in that it has a layer 115bt between the insulating layer 255c and the pixel electrode 111bt.

[0123] The light-emitting device 130ct differs from the light-emitting device 130c in that it has a pixel electrode 111ct instead of the pixel electrode 111c, and in that it has a layer 115ct between the insulating layer 255c and the pixel electrode 111ct.

[0124] The pixel electrodes 111a, 111b, and 111c may each have a reflective electrode. Furthermore, in the pixel electrodes 111a, 111b, and 111c, a light-transmitting electrode may be stacked on the reflective electrode, and the light-transmitting electrode may have a desired thickness, thereby providing a microcavity structure to the light-emitting device. By providing a microcavity structure, the color purity of light emitted from the light-emitting device can be improved.

[0125] The pixel electrodes 111at, 111bt, and 111ct may be configured to be light-transmitting. The configurations of the pixel electrodes 111at, 111bt, and 111ct, and applicable materials therefor, will be described later.

[0126] The layers 115at, 115bt, and 115ct may be made of a dielectric multilayer film. The configurations of the layers 115at, 115bt, and 115ct, and the materials that can be used therefor will be described later.

[0127] The EL layer has at least a light-emitting layer. The light-emitting layer contains one or more light-emitting materials. As the light-emitting material, a material that emits light of a color such as blue, purple, blue-purple, green, yellow-green, yellow, orange, or red is appropriately used. Furthermore, a material that emits near-infrared light can also be used as the light-emitting material.

[0128] Examples of the light-emitting material contained in the light-emitting element include fluorescent materials, phosphorescent materials, TADF materials, and quantum dot materials.

[0129] The light-emitting layer may contain one or more organic compounds (host materials, assist materials, etc.) in addition to a light-emitting substance (guest material). As the one or more organic compounds, one or both of a substance with high hole-transport properties (hole-transport material) and a substance with high electron-transport properties (electron-transport material) can be used. Furthermore, as the one or more organic compounds, a bipolar substance (a substance with high electron-transport properties and high hole-transport properties) or a TADF material can be used.

[0130] In addition to the light-emitting layer, the EL layer may include one or more of a layer containing a substance with high hole-injecting properties (hole-injecting layer), a layer containing a hole-transporting material (hole-transporting layer), a layer containing a substance with high electron-blocking properties (electron-blocking layer), a layer containing a substance with high electron-injecting properties (electron-injecting layer), a layer containing an electron-transporting material (electron-transporting layer), and a layer containing a substance with high hole-blocking properties (hole-blocking layer).In addition, the EL layer may include one or both of a bipolar substance and a TADF material.

[0131] The light-emitting element can be made of either a low-molecular-weight compound or a high-molecular-weight compound, and may contain an inorganic compound. The layers constituting the light-emitting element can be formed by a method such as a vapor deposition method (including a vacuum vapor deposition method), a transfer method, a printing method, an inkjet method, or a coating method.

[0132] The light-emitting element may have a single structure (a structure having only one light-emitting unit) or a tandem structure (a structure having multiple light-emitting units). The light-emitting unit has at least one light-emitting layer. The tandem structure is a structure in which multiple light-emitting units are connected in series via a charge-generating layer. When a voltage is applied between a pair of electrodes, the charge-generating layer injects electrons into one of the two light-emitting units and holes into the other. The tandem structure allows the light-emitting element to emit light with high brightness. Furthermore, the tandem structure can reduce the current required to achieve the same brightness compared to a single structure, thereby improving reliability. The tandem structure may also be called a stack structure.

[0133] The tandem-structure light-emitting device may have two or more light-emitting units in each of layers 113a, 113b, 113c, 113at, 113bt, and 113ct, and each light-emitting unit may include one or more light-emitting layers. Each light-emitting unit may have one or more of a hole injection layer, a hole transport layer, a hole blocking layer, an electron blocking layer, an electron transport layer, and an electron injection layer. A charge generation layer is preferably provided between each light-emitting unit. The charge generation layer has at least a charge generation region.

[0134] Tandem light-emitting devices, which emit light from multiple light-emitting units, require a relatively high voltage to emit light, but require a smaller current to achieve the same emission intensity as a single-type light-emitting device (one light-emitting unit configuration). Therefore, the tandem structure can reduce the current stress per light-emitting unit and extend the device life. In other words, the use of tandem light-emitting devices can form highly reliable display devices.

[0135] The common layer 114 may have an electron injection layer or a hole injection layer. Alternatively, the common layer 114 may have a stack of an electron transport layer and an electron injection layer. Alternatively, the common layer 114 may have a stack of a hole transport layer and a hole injection layer. The common layer 114 and the common electrode 117 are shared by the light-emitting devices of each sub-pixel.

[0136] It is preferable that the insulating layer 255a, the insulating layer 255b, the insulating layer 255c, the common layer 114, the common electrode 117, and the protective layer 131 are all formed of materials that have high transmittance to visible light or light with wavelengths ranging from blue light to red light. In addition, in order to increase the transmittance of the light-transmitting region in the pixel 11, a configuration in which one or more of the insulating layer 255a, the insulating layer 255b, the insulating layer 255c, the common layer 114, the common electrode 117, and the protective layer 131 are not provided may be adopted.

[0137] The protective layer 131 is not limited to a single layer structure, and may have a stacked structure of two or more layers. By providing the protective layer 131, the reliability of the light-emitting device can be improved.

[0138] There is no limitation on the conductivity of the protective layer 131. The protective layer 131 can be formed using at least one of an insulating film, a semiconductor film, and a conductive film.

[0139] The protective layer 131 has an inorganic film, which can prevent oxidation of the common electrode 117 and suppress impurities (moisture, oxygen, etc.) from entering the light-emitting device and the light-receiving device, thereby suppressing deterioration of the light-emitting device and the light-receiving device and improving the reliability of the display device.

[0140] For the protective layer 131, for example, an inorganic insulating film such as an insulating oxide film, an insulating nitride film, an insulating oxynitride film, or an insulating nitride oxide film can be used. Specific examples of these inorganic insulating films are as given in the description of the insulating layer 125. In particular, the protective layer 131 preferably has an insulating nitride film or an insulating nitride oxide film, and more preferably has an insulating nitride film.

[0141] Alternatively, an inorganic film containing In—Sn oxide (also referred to as ITO), In—Zn oxide, Ga—Zn oxide, Al—Zn oxide, indium gallium zinc oxide (In—Ga—Zn oxide, also referred to as IGZO), or the like can be used for the protective layer 131. The inorganic film preferably has high resistance, specifically, preferably has higher resistance than the common electrode 117. The inorganic film can also be an inorganic film further containing nitrogen.

[0142] The protective layer 131 preferably has high transparency to visible light. ITO, IGZO, and aluminum oxide are preferable because they are inorganic materials that have high transparency to visible light.

[0143] For example, a stacked structure of an aluminum oxide film and a silicon nitride film on the aluminum oxide film, or a stacked structure of an aluminum oxide film and an IGZO film on the aluminum oxide film can be used as the protective layer 131. By using such a stacked structure, impurities (water, oxygen, etc.) can be prevented from entering the EL layer side.

[0144] Furthermore, the protective layer 131 may include an organic film. The protective layer 131 may also include both an organic film and an inorganic film. Examples of organic materials that can be used for the protective layer 131 include the organic insulating materials that can be used for the insulating layer 127.

[0145] The protective layer 131 may have a two-layer structure formed by using different film formation methods. Specifically, the first layer of the protective layer 131 may be formed by the ALD method, and the second layer of the protective layer 131 may be formed by the sputtering method.

[0146] The adhesive layer 122 can be made of various curable adhesives, such as a photo-curable adhesive (e.g., an ultraviolet curable adhesive), a reactive curable 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. In particular, a material with low moisture permeability, such as epoxy resin, is preferable. A two-component resin can also be used. An adhesive sheet or the like can also be used.

[0147] The substrate 120 and the substrate 110 can be made of glass, quartz, ceramics, sapphire, resin, metal, alloy, semiconductor, or the like. A material that transmits light is used for the substrate on the side from which light from the light-emitting device is extracted. Using a flexible material for the substrate 120 and the substrate 110 can increase the flexibility of the display device. Polarizing plates can also be used for the substrate 120 and the substrate 110.

[0148] The substrate 120 and the substrate 110 can be made of polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyacrylonitrile resin, acrylic resin, polyimide resin, polymethyl methacrylate resin, polycarbonate (PC) resin, polyethersulfone (PES) resin, polyamide resin (nylon, aramid, etc.), polysiloxane resin, cycloolefin resin, polystyrene resin, polyamideimide resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, cellulose nanofiber, etc. The substrate 120 and the substrate 110 can also be made of glass having a thickness sufficient to provide flexibility.

[0149] When a circularly polarizing plate is superimposed on a display device, it is preferable that the display device has a substrate with high optical isotropy. A substrate with high optical isotropy has small birefringence (or a small amount of birefringence).

[0150] The absolute value of the retardation (phase difference) of a substrate having high optical isotropy is preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less.

[0151] Examples of films with high optical isotropy include triacetyl cellulose (TAC, also known as cellulose triacetate) films, cycloolefin polymer (COP) films, cycloolefin copolymer (COC) films, and acrylic resin films.

[0152] Furthermore, when a film is used as a substrate, the film may absorb water, causing deformation such as wrinkles in the display device. Therefore, it is preferable to use a film with low water absorption for the substrate. For example, it is preferable to use a film with a water absorption rate of 1% or less, more preferably 0.1% or less, and even more preferably 0.01% or less.

[0153] Various optical members can be disposed on the outside of the substrate 120 and the substrate 110. Examples of optical members include a polarizing plate, a retardation plate, a light diffusion layer (such as a diffusion film), an anti-reflection layer, and a light-collecting film. In addition, surface protection layers such as an antistatic film that suppresses the adhesion of dust, a water-repellent film that makes it difficult for dirt to adhere, a hard coat film that suppresses the occurrence of scratches during use, and an impact absorbing layer can also be disposed on the outside of the substrate 120 and the substrate 110.

[0154] Providing a glass layer or a silica layer (SiOx layer) as the surface protection layer is preferable because it can suppress the occurrence of surface contamination and scratches. Furthermore, DLC (diamond-like carbon), aluminum oxide (AlOx), polyester-based materials, polycarbonate-based materials, etc. can also be used as the surface protection layer. It is preferable to use a material with high transmittance to visible light for the surface protection layer. It is also preferable to use a material with high hardness for the surface protection layer.

[0155] In a display device according to one embodiment of the present invention, an EL layer is provided in an island shape for each light-emitting device, thereby suppressing leakage current between subpixels. This prevents unintended light emission due to crosstalk, thereby achieving a display device with extremely high contrast. In particular, a display device with high current efficiency at low luminance can be realized. Furthermore, by providing an insulating layer having a tapered edge between adjacent island-shaped EL layers, discontinuities during formation of a common electrode can be suppressed. This suppresses connection defects due to disconnections in the common layer and the common electrode. Therefore, the display device according to one embodiment of the present invention can achieve both high resolution and high display quality.

[0156] In the following, when describing matters common to the pixel electrodes 111a, 111b, and 111c, the pixel electrode may be referred to as the pixel electrode 111. When describing matters common to the pixel electrodes 111at, 111bt, and 111ct, the pixel electrode may be referred to as the pixel electrode 111t.

[0157] When describing matters common to the layer 113a, the layer 113b, and the layer 113c, the layer may be referred to as the layer 113. When describing matters common to the layer 113at, the layer 113bt, and the layer 113ct, the layer may be referred to as the layer 113t.

[0158] 3B, the layer 113 is formed so as to cover the end portion of the pixel electrode 111. In addition, a mask layer 118 is located on the layer 113. The mask layer 118 is a remaining portion of the mask layer that was provided in contact with the upper surface of the layer 113 when the layer 113 was processed.

[0159] In FIG. 3B, the mask layer 118 on the layer 113a is referred to as a mask layer 118a, the mask layer 118 on the layer 113b is referred to as a mask layer 118b, and the mask layer 118 on the layer 113c is referred to as a mask layer 118c.

[0160] In the display device of one embodiment of the present invention, an insulating layer 125 and an insulating layer 127 over the insulating layer 125 are provided in a region between adjacent light-emitting devices.

[0161] The side surfaces of the layer 113 are covered with the insulating layer 125. The insulating layer 127 overlaps the side surfaces of the layer 113 with the insulating layer 125 interposed therebetween.

[0162] A portion of the upper surface of layer 113 is covered with mask layer 118. Insulating layer 125 and insulating layer 127 overlap a portion of the upper surface of layer 113 via mask layer 118. Note that the upper surface of layer 113 is not limited to the upper surface of the flat portion that overlaps the upper surface of the pixel electrode, but may also include the upper surfaces of the inclined portion and flat portion located outside the upper surface of the pixel electrode.

[0163] By covering a part of the upper surface and the side surfaces of the layer 113 with at least one of the insulating layer 125, the insulating layer 127, and the mask layer 118, it is possible to prevent the common layer 114 (or the common electrode 117) from coming into contact with the pixel electrode 111 and the side surfaces of the layer 113. Therefore, it is possible to prevent short-circuiting between the upper and lower layers of the light-emitting device.

[0164] The insulating layer 127 is provided on the insulating layer 125 so as to fill the recess in which the insulating layer 125 is formed. The insulating layer 127 can be configured to overlap a part of the top surface and the side surfaces of the layer 113 with the insulating layer 125 interposed therebetween. The insulating layer 127 preferably covers at least a part of the side surfaces of the insulating layer 125.

[0165] 3C, the layer 113t is formed so as to cover the end portion of the pixel electrode 111t. A mask layer 118 is located on the layer 113t. The mask layer 118 is a remaining portion of the mask layer that was provided in contact with the upper surface of the layer 113t when the layer 113t was processed.

[0166] In FIG. 3B, the mask layer 118 on the layer 113at is denoted as a mask layer 118at, the mask layer 118 on the layer 113bt is denoted as a mask layer 118bt, and the mask layer 118 on the layer 113ct is denoted as a mask layer 118ct.

[0167] The side surface of the layer 113t is covered with an insulating layer 125. The insulating layer 127 overlaps the side surface of the layer 113t with the insulating layer 125 interposed therebetween.

[0168] A portion of the upper surface of layer 113t is covered with mask layer 118. Insulating layer 125 and insulating layer 127 overlap a portion of the upper surface of layer 113t via mask layer 118. Note that the upper surface of layer 113t is not limited to only the upper surface of the flat portion that overlaps the upper surface of the pixel electrode, but may also include the upper surfaces of the inclined portion and flat portion located outside the upper surface of the pixel electrode.

[0169] By covering a part of the upper surface and the side surfaces of the layer 113t with at least one of the insulating layer 125, the insulating layer 127, and the mask layer 118, it is possible to prevent the common layer 114 (or the common electrode 117) from coming into contact with the pixel electrode 111t and the side surfaces of the layer 113t, thereby preventing short-circuiting between the upper and lower layers of the light-emitting device.

[0170] The insulating layer 127 is provided on the insulating layer 125 so as to fill the recess in which the insulating layer 125 is formed. The insulating layer 127 can be configured to overlap a part of the top surface and the side surfaces of the layer 113t via the insulating layer 125. The insulating layer 127 preferably covers at least a part of the side surfaces of the insulating layer 125.

[0171] By providing the insulating layers 125 and 127, the gaps between adjacent island-shaped layers can be filled, which reduces large unevenness in height on the surface on which layers (e.g., a carrier injection layer, a common electrode, etc.) are formed on the island-shaped layers, thereby making the surface flatter, thereby improving the coverage of the carrier injection layer, the common electrode, etc.

[0172] The common layer 114 and the common electrode 117 are provided on the layer 113, the layer 113t, the mask layer 118, the insulating layer 125, and the insulating layer 127. Before the insulating layer 125 and the insulating layer 127 are provided, there is a step between the region where the pixel electrode and the island-shaped EL layer are provided and the region where the pixel electrode and the island-shaped EL layer are not provided (the region between the light-emitting devices).

[0173] In the display device of one embodiment of the present invention, the insulating layers 125 and 127 can planarize the step, thereby improving the coverage of the common layer 114 and the common electrode 117. Therefore, poor connection due to disconnection of the step can be suppressed. Furthermore, an increase in electrical resistance due to local thinning of the common electrode 117 due to the step can be suppressed.

[0174] The upper surface of the insulating layer 127 preferably has a highly flat shape, but may have a convex portion, a convex curved surface, a concave curved surface, or a concave portion.

[0175] 3B , by providing the mask layer 118, the insulating layer 125, and the insulating layer 127, the common layer 114 and the common electrode 117 can be formed with high coverage, and it is possible to prevent the formation of portions where the common layer 114 and the common electrode 117 are separated and portions where the film thickness is locally thin.

[0176] Therefore, between the light-emitting devices, it is possible to prevent poor connection due to the disconnection of the common layer 114 and the common electrode 117 and an increase in electrical resistance due to a locally thin portion of the film thickness in the common layer 114 and the common electrode 117. As a result, the display device according to one embodiment of the present invention can improve the display quality.

[0177] Next, examples of materials for the insulating layer 125 and the insulating layer 127 will be described.

[0178] The insulating layer 125 can be an insulating layer containing an inorganic material. For example, an inorganic insulating film such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used for the insulating layer 125. The insulating layer 125 is not limited to a single-layer structure, and can also have a stacked structure. Examples of oxide insulating films include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, an indium gallium zinc oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide film. Examples of nitride insulating films include a silicon nitride film and an aluminum nitride film. Examples of oxynitride insulating films include a silicon oxynitride film and an aluminum oxynitride film. Examples of nitride oxide insulating films include a silicon nitride oxide film and an aluminum nitride oxide film. Aluminum oxide is particularly preferable because it has a high etching selectivity with respect to the EL layer and protects the EL layer in the formation of the insulating layer 127, which will be described later.

[0179] In particular, by using an inorganic insulating film such as an aluminum oxide film, a hafnium oxide film, or a silicon oxide film formed by atomic layer deposition (ALD) as the insulating layer 125, it is possible to form an insulating layer 125 that has few pinholes and has an excellent function of protecting the EL layer. The insulating layer 125 can also have a stacked structure of a film formed by ALD and a film formed by sputtering. For example, the insulating layer 125 can have a stacked structure of an aluminum oxide film formed by ALD and a silicon nitride film formed by sputtering.

[0180] The insulating layer 125 preferably functions as a barrier insulating layer against at least one of water and oxygen. The insulating layer 125 preferably has a function of suppressing diffusion of at least one of water and oxygen. The insulating layer 125 preferably has a function of capturing or fixing (also referred to as gettering) at least one of water and oxygen.

[0181] In this specification and the like, a barrier insulating layer refers to an insulating layer having barrier properties. Furthermore, in this specification and the like, the term "barrier properties" refers to a function of suppressing the diffusion of a corresponding substance (also referred to as low permeability), or a function of capturing or gettering the corresponding substance.

[0182] The insulating layer 125 has a function as a barrier insulating layer or a gettering function, which makes it possible to suppress the intrusion of impurities (typically, at least one of water and oxygen) that may diffuse into each light-emitting device from the outside. With this configuration, it is possible to provide a highly reliable light-emitting device and further a highly reliable display device.

[0183] The insulating layer 125 and the mask layer 118b may be made of the same material. In this case, the boundary between the mask layer 118b and the insulating layer 125 may become unclear, and the mask layer 118b and the insulating layer 125 may be recognized as a single layer.

[0184] The insulating layer 127 provided on the insulating layer 125 has the function of flattening the unevenness of the insulating layer 125 formed between adjacent light emitting devices.

[0185] An insulating layer containing an organic material can be suitably used as the insulating layer 127. As the organic material, a photosensitive organic resin is preferably used, for example, a photosensitive resin composition containing an acrylic resin. Note that in this specification and the like, the term "acrylic resin" does not refer only to polymethacrylic acid ester or methacrylic resin, but may refer to all acrylic polymers in a broad sense.

[0186] The insulating layer 127 can be made of acrylic resin, polyimide resin, epoxy resin, imide resin, polyamide resin, polyimideamide resin, silicone resin, siloxane resin, benzocyclobutene resin, phenol resin, or precursors of these resins. The insulating layer 127 can be made of organic materials such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or alcohol-soluble polyamide resin. The photosensitive organic resin can be a photoresist. Either a positive-type material or a negative-type material can be used as the photosensitive organic resin.

[0187] <Pixel Electrode, Common Electrode> The pixel electrode and the common electrode can each be made of a light-transmitting conductive material.

[0188] By using a light-transmitting conductive material for the common electrode, light emitted from the light-emitting device can be emitted to the common electrode side.

[0189] Examples of suitable light-transmitting conductive materials include indium tin oxide (In-Sn oxide, also referred to as ITO), indium tin oxide containing titanium oxide, indium tin oxide containing silicon (In-Si-Sn oxide, also referred to as ITSO), and indium zinc oxide (In-Zn oxide, also referred to as IZO (registered trademark)). Conductive oxides such as indium oxide, indium zinc oxide, zinc oxide, and zinc oxide containing gallium, or graphene, can also be used. Metal materials such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, and titanium, or alloy materials containing such metal materials, can also be used. Nitrides of such metal materials (e.g., titanium nitride) can also be used. When using metal materials or alloy materials (or their nitrides), it is preferable to thin the metal materials to ensure light-transmitting properties. A stacked film of the above materials can also be used as the conductive layer. For example, a stacked film of an alloy of silver and magnesium and indium tin oxide can be used because it can increase conductivity.

[0190] When the pixel electrodes include reflective electrodes, the reflective electrodes can be made of metals, conductive metal nitrides, or the like. These materials can also be stacked. For example, the pixel electrodes 111a, 111b, and 111c each have a reflective electrode.

[0191] Examples of metals that can function as reflective electrodes include metal elements selected from the group consisting of tungsten, copper, aluminum, chromium, silver, gold, platinum, zinc, tantalum, nickel, titanium, iron, cobalt, molybdenum, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, alloys containing the aforementioned metal elements, and alloys combining the aforementioned metal elements. The reflective electrode can also include a metal nitride. Examples of metal nitrides that can be used include titanium nitride.

[0192] Furthermore, it is particularly preferable that the reflective electrode has a function of reflecting visible light. Therefore, it is preferable to use a conductor with high reflectivity for visible light for the reflective electrode. The reflective electrode preferably has, for example, silver, aluminum, an alloy film of silver (Ag), palladium (Pd), and copper (Cu) (Ag-Pd-Cu (APC) film), a laminated film of aluminum sandwiched between a pair of titanium films (a laminated film of Ti, Al, and Ti in this order), or a laminated film of silver sandwiched between a pair of indium tin oxide films (a laminated film of ITO, Ag, and ITO in this order).

[0193] The pixel electrodes can be fabricated by a thin film method, such as sputtering, chemical vapor deposition (CVD), ALD, pulsed laser deposition (PLD), molecular beam epitaxy (MBE), or vacuum evaporation.

[0194] <Dielectric Multilayer Film> A dielectric multilayer film can be used as each of the layer 115at, the layer 115bt, and the layer 115ct.

[0195] The following description will be given of a case where the light-emitting devices 130at, 130bt, and 130ct have the functions of displaying red, green, and blue, respectively, but the following description may be substituted with other colors as appropriate. For example, red, green, and blue may be substituted with yellow, cyan, and magenta, respectively.

[0196] A case will be described in which the light-emitting device 130at has a function of displaying red. The layer 115at preferably has a function of reflecting light in the red wavelength range. The layer 115at also preferably has a function of transmitting light. Here, the light transmitted through the layer 115at is, for example, light including a wavelength range other than red, and preferably includes one or more of light in the green wavelength range and light in the blue wavelength range.

[0197] A case will be described in which the light-emitting device 130bt has a function of displaying green. The layer 115bt preferably has a function of reflecting light in the green wavelength range. The layer 115bt also preferably has a function of transmitting light. Here, the light transmitted through the layer 115bt is, for example, light including a wavelength range other than green, and preferably includes one or more of light in the blue wavelength range and light in the red wavelength range.

[0198] A case will be described in which the light-emitting device 130ct has a function of displaying blue. The layer 115ct preferably has a function of reflecting light in the blue wavelength range. The layer 115ct also preferably has a function of transmitting light. Here, the light transmitted by the layer 115ct is, for example, light including a wavelength range other than blue, and preferably includes one or more of light in the red wavelength range and light in the green wavelength range.

[0199] The light transmitted through the layer 115at, the light transmitted through the layer 115bt, and the light transmitted through the layer 115ct are each incident on a camera disposed below the display unit. It is preferable that a full-color image can be captured by combining the light transmitted through the layer 115at, the light transmitted through the layer 115bt, and the light transmitted through the layer 115ct. Therefore, for example, it is preferable that the combined light transmitted through the layer 115at, the light transmitted through the layer 115bt, and the light transmitted through the layer 115ct each include red, green, and blue wavelength ranges.

[0200] The dielectric multilayer film preferably includes two or more types of films. It is also preferable that each film of the same type (made of the same material) includes two or more layers. For example, when two types of films (hereinafter, type A films and type B films) are used, type A films and type B films are alternately stacked, and a total of two or more type A films and type B films are included.

[0201] In addition, it is preferable that a light-transmitting conductive layer be formed on the dielectric multilayer film. Note that the conductive layer may function as the pixel electrode 111at (pixel electrode 111bt, pixel electrode 111ct) or the layer 115at (layer 115bt, layer 115ct).

[0202] The dielectric multilayer film may contain layers made of, for example, fluorides, oxides, nitrides, or the like.

[0203] For example, metal fluorides can be used.

[0204] In particular, metal fluorides such as magnesium fluoride (MgF), lithium fluoride (LiF), sodium fluoride (NaF), calcium fluoride (CaF), aluminum fluoride (AlF), and strontium fluoride (SrF) can be used. Fluorides containing sodium and aluminum can also be used. These fluorides can be suitably used as materials with low refractive indexes, for example.

[0205] Furthermore, for example, silicon oxide (SiO 2 ) can be suitably used as a material with a low refractive index.

[0206] Further, for example, metal oxides can be used.

[0207] In particular, metal oxides such as aluminum oxide (Al2O3), zirconium oxide (ZrO2), hafnium oxide (HfO2), tantalum oxide (Ta2O5), and titanium oxide (titanium trioxide: Ti2O3, titanium pentoxide: Ti3O5, titanium monoxide: TiO, titanium dioxide: TiO2) can be used. These metal oxides can be suitably used as materials with a high refractive index.

[0208] Furthermore, for example, silicon nitride can be suitably used as a material with a high refractive index.

[0209] In the metal fluorides described above, the composition of metal and fluorine may deviate from the stoichiometric ratio. In the metal oxides described above, the composition of metal and oxygen may deviate from the stoichiometric ratio. In the silicon oxides described above, the composition of silicon and oxygen may deviate from the stoichiometric ratio.

[0210] Dielectric multilayer films can be constructed by stacking materials with different refractive indices. By appropriately selecting the refractive index, film thickness, and number of layers of each layer, the optical path length can be adjusted, and the phase of the light reflected from each layer can be controlled. The resulting optical interference can be used to control the reflectance and transmittance within a desired wavelength range.

[0211] The layers 115at, 115bt, and 115ct have different configurations because they reflect different wavelength ranges of color. The layers 115at, 115bt, and 115ct may be made of the same material or may be made of different materials.

[0212] In the dielectric multilayer film, layers with a high refractive index and layers with a low refractive index can be alternately and repeatedly stacked, for example, layers with a high refractive index, layers with a low refractive index, layers with a high refractive index, and layers with a low refractive index can be alternately and repeatedly stacked.

[0213] The layers 115at, 115bt, and 115ct may have different thicknesses, and may each have a thickness of, for example, 100 nm to 3000 nm.

[0214] Each layer of the dielectric multilayer film can be formed by a thin film method, such as atomic layer deposition (ALD) or sputtering.

[0215] <Example of Dielectric Multilayer Film> For an example of a laminate of a dielectric multilayer film and a conductive layer thereon, the reflectance and transmittance were calculated using thin film calculation software "Essential Macleod (trademark)" (manufactured by Thin Film Center Inc.).

[0216] Calculations were performed on the configuration shown in Table 1, which is an example of a configuration in which the layer 115at and the pixel electrode 111at have the function of reflecting red light. In Table 1 and Tables 2 and 3 described below, "Substrate" refers to the substrate disposed below the layer 115at in the configuration used for the calculations. Furthermore, "Medium" refers to the medium disposed above the pixel electrode 111at in the configuration used for the calculations, and light enters or leaves the interface between the pixel electrode 111at and the medium. The first layer in Table 1 (labeled "1" in Table 1) corresponds to the pixel electrode 111at, and the second to fifteenth layers (labeled "2" to "15" in Table 1) correspond to the films constituting the dielectric multilayer film layer 115at, in order from the top. The materials for ITO, SiO2, and TiO2 are indium tin oxide (ITO), silicon oxide (SiO2), and titanium oxide (TiO2), respectively.

[0217]

[0218] Calculations were performed on the configuration shown in Table 2, which is an example of a configuration in which the layer 115bt and the pixel electrode 111bt have the function of reflecting green color. The first layer in Table 2 (shown as "1" in Table 2) corresponds to the pixel electrode 111at, and the second to fifteenth layers (shown as "2" to "15" in Table 2) correspond to the films that make up the layer 115bt, which is a dielectric multilayer film, in order from the top. The materials for ITO, SiO2, and TiO2 are indium tin oxide (ITO), silicon oxide (SiO2), and titanium oxide (TiO2), respectively.

[0219]

[0220] Calculations were performed on the configuration shown in Table 3, which is an example of a configuration in which the layer 115ct and the pixel electrode 111ct have the function of reflecting blue light. The first layer in Table 3 (shown as "1" in Table 3) corresponds to the pixel electrode 111at, and the second to thirteenth layers (shown as "2" to "13" in Table 3) correspond to the films that make up the layer 115bt, which is a dielectric multilayer film, in order from the top. The materials for ITO, SiO2, and TiO2 are indium tin oxide (ITO), silicon oxide (SiO2), and titanium oxide (TiO2), respectively.

[0221]

[0222] In Tables 1, 2, and 3, the thickness of the multiple ITO layers used was, for example, in the range of 10 nm to 200 nm. Furthermore, the thickness of each of the multiple ITO layers used was different. Furthermore, the thickness of each of the multiple SiO layers used was in the range of 10 nm to 200 nm. Furthermore, the thickness of each of the multiple SiO layers used was different.

[0223] Calculation results for the configurations shown in Tables 1 to 3 are shown in Fig. 13. Fig. 13A shows the calculation results for reflectance, with the horizontal axis representing wavelength and the vertical axis representing reflectance. The R, G, and B symbols in the figure indicate the calculation results for the configurations shown in Tables 1, 2, and 3, respectively.

[0224] 13B shows the calculation results of the transmittance, where the horizontal axis represents wavelength and the vertical axis represents transmittance. The R, G, and B symbols in the figure indicate the calculation results for the configurations in Tables 1, 2, and 3, respectively.

[0225] 13A and 13B, the configuration (R) shown in Table 1 has a function of reflecting the red wavelength range and a function of transmitting the green and blue wavelength ranges. The configuration (G) shown in Table 2 has a function of reflecting the green wavelength range and a function of transmitting the red and blue wavelength ranges. The configuration (B) shown in Table 3 has a function of reflecting the blue wavelength range and a function of transmitting the red and blue wavelength ranges.

[0226] The light that passes through each sub-pixel and is captured by the camera is not limited to visible light, and for example, infrared light may also be captured.

[0227] 4A to 4C show examples of colors displayed by and transmitted through each sub-pixel in the configuration shown in FIG. 3C.

[0228] 4A , subpixels R(t), G(t), and B(t) have the function of emitting the colors R, G, and B, respectively. Subpixel R(t) has the function of transmitting the colors of subpixel G and subpixel B, subpixel G(t) has the function of transmitting the colors of subpixel R and subpixel B, and subpixel B(t) has the function of transmitting the colors of subpixel R and subpixel G.

[0229] In the example shown in FIG. 4B , subpixels R(t), G(t), and B(t) have the function of emitting the colors of subpixels R, G, and B, respectively. Subpixels R(t), G(t), and B(t) also have the function of transmitting infrared light (IR). In such a case, the pixel electrodes and dielectric multilayer films used in subpixels R(t), G(t), and B(t) can have a common configuration. That is, pixel electrodes 111at, 111bt, and 111ct can have a common configuration, and layers 115at, 115bt, and 115ct can have a common configuration. Using a common configuration can simplify the manufacturing process of the display device.

[0230] FIG. 5A also shows an example in which a pixel has a subpixel IR(t) that emits infrared light (IR). For example, the light-emitting device 130dt included in the subpixel IR(t) can emit infrared light IR. The light-emitting device 130dt includes a pixel electrode 111dt, a layer 113dt, and a common electrode 117. The pixel electrode 111dt can be a conductive layer that reflects infrared light. The layer 113dt also includes a light-emitting layer. Images can be captured using the infrared light emitted by the light-emitting device 130dt as a light source. Light that has passed through one or more subpixels other than the subpixel I(t), such as subpixel R(t), subpixel G(t), and subpixel B(t), is incident on the camera. In the example shown in FIG. 5A, the subpixels R(t) and G(t) have the ability to transmit infrared light.

[0231] Alternatively, as shown in FIG. 5B , the subpixel IR(t) may include a layer 115dt. The subpixel IR(t) shown in FIG. 5B emits infrared light IR and can transmit light outside the infrared region, such as visible light. The layer 115dt is a dielectric multilayer film, and the stacked structure of the layer 115dt and the pixel electrode 111dt has the function of reflecting infrared light and the function of transmitting light outside the infrared region, such as visible light (see FIG. 5B ).

[0232] The display device may have two or more cameras 30 in an area overlapping the display unit 20. For example, the display device may have a first camera that captures visible light and a second camera that captures infrared light. FIG. 5C shows an example in which the display device has two cameras 30 (camera 30a, camera 30b) in an area overlapping the display unit 20. The display unit 20 may also have two or more display units b. The pixel configurations of the multiple display units b can be determined independently. The pixels of the multiple display units b can have the same configuration or different configurations. Specifically, the pixel configuration of each display unit b can be determined depending on the light captured by the camera overlapping each display unit b. For example, the configuration shown in FIG. 4A can be used for the display unit b that is provided overlapping the first camera that captures visible light, and the configuration shown in FIG. 4B, 5A, or 5B can be used for the display unit b that is provided overlapping the second camera that captures infrared light.

[0233] The subpixels R(t), G(t), and B(t) may have a function of transmitting both visible light and infrared light. In the example shown in FIG. 4C , the subpixels R(t), G(t), and B(t) have a function of emitting the colors of the subpixels R, G, and B, respectively. The subpixel R(t) has a function of transmitting G, B, and infrared light, the subpixel G(t) has a function of transmitting the colors of the subpixels R, B, and infrared light, and the subpixel B(t) has a function of transmitting the colors of the subpixels R, G, and infrared light. The configuration of FIG. 4C allows both visible light and infrared light to pass through the camera 30 provided in an area overlapping the display unit 20. The camera 30 can also appropriately capture images using visible light and infrared light depending on the application of the display device.

[0234] 4C may be used when the display device has two or more cameras 30. For example, the structure shown in FIG. 4C may be used for both the display portion b provided overlaid with a first camera that captures visible light and the display portion b provided overlaid with a second camera that captures infrared light. By using a common structure for the two display portions b, the manufacturing process may be simplified.

[0235] [Insulating Layer] An inorganic insulating film applicable to a semiconductor device will be described. For example, the inorganic insulating film described below can be used for the layer 101, the insulating layer 255a, the insulating layer 255b, the insulating layer 255c, the insulating layer 125, the protective layer 131, the mask layer 118, etc. The inorganic insulating film described below can also be used for an insulating layer used in a transistor or the like described later.

[0236] Examples of inorganic insulating films include an oxide insulating film, a nitride insulating film, an oxynitride insulating film, and a nitride oxide insulating film. Examples of oxide insulating films include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, a tantalum oxide film, a cerium oxide film, a gallium zinc oxide film, and a hafnium aluminate film. Examples of nitride insulating films include a silicon nitride film and an aluminum nitride film. Examples of oxynitride insulating films include a silicon oxynitride film, an aluminum oxynitride film, a gallium oxynitride film, an yttrium oxynitride film, and a hafnium oxynitride film. Examples of nitride oxide insulating films include a silicon nitride oxide film and an aluminum nitride oxide film. Furthermore, an organic insulating film may be used for the insulating layer of a semiconductor device.

[0237] Furthermore, a high-k material can be used for the gate insulating layer of a transistor and the insulating layer of a capacitor. Examples of the high-k material include aluminum oxide, gallium oxide, hafnium oxide, tantalum oxide, zirconium oxide, hafnium zirconium oxide, oxides containing aluminum and hafnium, oxynitrides containing aluminum and hafnium, oxides containing silicon and hafnium, oxynitrides containing silicon and hafnium, and nitrides containing silicon and hafnium.

[0238] Furthermore, materials with low dielectric constants can be used as interlayer films in semiconductor devices. Examples of materials with low dielectric constants include inorganic insulating materials such as silicon oxide, silicon oxynitride, and silicon nitride oxide, and resins such as polyester, polyolefin, polyamide (nylon, aramid, etc.), polyimide, polycarbonate, and acrylic resin. Examples of other inorganic insulating materials with low dielectric constants include silicon oxide doped with fluorine, silicon oxide doped with carbon, and silicon oxide doped with carbon and nitrogen. Another example is silicon oxide having vacancies. Note that these silicon oxides may contain nitrogen.

[0239] [Conductive Layer] A conductive layer included in a semiconductor device can be formed using a metal element, an alloy containing the metal element, or an alloy combining the above metal elements. For example, the conductive layers described below can be used for the pixel electrode 111, the pixel electrode 111t, the common electrode 117, etc. The conductive layers described below can also be used for conductive layers used in transistors, etc., which will be described later.

[0240] The conductive layer may be made of, for example, a metal element selected from aluminum, chromium, copper, silver, gold, platinum, zinc, tantalum, nickel, titanium, iron, cobalt, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, or lanthanum, or an alloy containing the above metal elements, or an alloy combining the above metal elements. As the alloy containing the above metal elements, nitrides of the alloys or oxides of the alloys may be used. For example, 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. Furthermore, semiconductors with high electrical conductivity, such as polycrystalline silicon containing impurity elements such as phosphorus, or silicides such as nickel silicide may also be used.

[0241] Nitrogen-containing conductive materials, such as nitrides containing tantalum, nitrides containing titanium, nitrides containing molybdenum, nitrides containing tungsten, nitrides containing ruthenium, nitrides containing tantalum and aluminum, or nitrides containing titanium and aluminum; oxygen-containing conductive materials, such as ruthenium oxide, oxides containing strontium and ruthenium, or oxides containing lanthanum and nickel; and materials containing metal elements, such as titanium, tantalum, or ruthenium, are preferred because they are conductive materials that are resistant to oxidation, have the function of suppressing oxygen diffusion, or maintain conductivity even after absorbing oxygen. Examples of oxygen-containing conductive materials include indium oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide (also referred to as ITO), indium tin oxide containing titanium oxide, indium tin oxide with added silicon (also referred to as ITSO), indium zinc oxide (also referred to as IZO (registered trademark)), and indium zinc oxide containing tungsten oxide. In this specification and the like, a conductive layer formed using a conductive material containing oxygen may be referred to as an oxide conductive layer.

[0242] Conductive materials containing tungsten, copper or aluminum as a main component are preferred because of their high conductivity.

[0243] Furthermore, a plurality of conductive layers formed from the above materials may be stacked. For example, a stacked structure may be formed by combining the above-described material containing a metal element and a conductive material containing oxygen. A stacked structure may be formed by combining the above-described material containing a metal element and a conductive material containing nitrogen. A stacked structure may be formed by combining the above-described material containing a metal element, a conductive material containing oxygen, and a conductive material containing nitrogen.

[0244] 6A is a block diagram illustrating a display device according to one embodiment of the present invention. The display device includes a pixel array provided in a display portion 20, a driver circuit 301, a driver circuit 302, and a driver circuit 303. The pixel array includes pixels 10 and 11 arranged in the column and row directions. The pixel 11 is surrounded by the pixel 10.

[0245] The driver circuits 301, 302, and 303 are drivers for driving the pixel array. The driver circuits 301, 302, and 303 may be, for example, shift register circuits that operate at high speed.

[0246] The driver circuits 301 and 302 can function as gate drivers, and the driver circuit 303 can function as a source driver. The driver circuits 301 and 302 are connected to pixels via gate lines GL. The driver circuit 303 is connected to pixels via source lines SL.

[0247] 6A shows an example in which the driver circuits 301 and 302 are provided as gate drivers, but a configuration in which either the driver circuit 301 or the driver circuit 302 is provided is also possible. Although the driver circuits 301 and 302 are connected to the same gate line GL, the driver circuits 301 and 302 may be connected to different gate lines GL. A demultiplexer may be provided between the driver circuit 303 and the pixel.

[0248] 6B shows an example of a pixel circuit that can be applied to a pixel. The pixel circuit includes a transistor M1, a transistor M2, a transistor M3, a capacitor C1, and a light-emitting device EL. The pixel circuit is also connected to a gate line GL and a source line SL (see FIG. 6A).

[0249] The gate of the transistor M1 is connected to the gate line GL, and one of the source or drain is connected to the source line SL, and the other is connected to one electrode of the capacitor C1 and the gate of the transistor M2. The transistor M2 has one of the source or drain connected to the wiring AL, and the other of the source or drain connected to one electrode of the light-emitting device EL, the other electrode of the capacitor C1, and one of the source or drain of the transistor M3. The transistor M3 has the gate connected to the gate line GL, and the other of the source or drain connected to the wiring RL. The other electrode of the light-emitting device EL is connected to the wiring CL.

[0250] A data potential is applied to the source line SL, and a selection signal is applied to the gate line GL. The selection signal includes a potential that turns on a transistor and a potential that turns off a transistor.

[0251] A reset potential is applied to the wiring RL. An anode potential is applied to the wiring AL. A cathode potential is applied to the wiring CL. The anode potential is higher than the cathode potential. The reset potential applied to the wiring RL can be a potential such that the potential difference between the reset potential and the cathode potential is smaller than the threshold voltage of the light-emitting device EL. The reset potential can be a potential higher than the cathode potential, the same as the cathode potential, or a potential lower than the cathode potential.

[0252] The transistors M1 and M3 function as switches. The transistor M2 functions as a transistor for controlling the current flowing through the light-emitting device EL. For example, it can be said that the transistor M1 functions as a selection transistor and the transistor M2 functions as a drive transistor.

[0253] Here, the transistors M1 to M3 can be transistors having metal oxide in their channel formation regions (hereinafter referred to as OS transistors). Alternatively, all of the transistors M1 to M3 can be transistors having silicon (single crystal silicon, polycrystalline silicon, microcrystalline silicon, or amorphous silicon) in their channel formation regions (hereinafter referred to as Si transistors). Alternatively, the transistors M1 and M3 can be OS transistors, and the transistor M2 can be a Si transistor.

[0254] Alternatively, one or more of the transistors included in the driver circuits 301, 302, and 303 may be Si transistors and the remaining transistors may be OS transistors. Alternatively, one or more of the driver circuits 301, 302, and 303 may be Si transistors and the remaining transistors may be OS transistors.

[0255] As the OS transistor, a transistor including an oxide semiconductor for a semiconductor layer in which a channel is formed can be used. A transistor including an oxide semiconductor, which has a wider band gap and a lower carrier concentration than silicon, can achieve an extremely small off-state current. Therefore, due to the small off-state current, charge accumulated in a capacitor connected in series with the transistor can be held for a long period of time. Therefore, it is preferable to use a transistor including an oxide semiconductor for each of the transistors M1 and M3 connected in series with the capacitor C1. By using transistors including an oxide semiconductor as the transistors M1 and M3, charge held in the capacitor C1 can be prevented from leaking through the transistor M1 or the transistor M3. Furthermore, since charge held in the capacitor C1 can be held for a long period of time, a still image can be displayed for a long period of time without rewriting pixel data.

[0256] Although the transistors are shown as n-channel transistors in FIG. 6B, p-channel transistors can also be used.

[0257] Further, as a transistor included in a pixel circuit, a transistor having a pair of gates overlapping with each other with a semiconductor layer interposed therebetween can be used.

[0258] In a transistor having a pair of gates, when the pair of gates are connected to each other and supplied with the same potential, the on-state current of the transistor is increased and the saturation characteristics are improved. Furthermore, a potential for controlling the threshold voltage of the transistor can be applied to one of the pair of gates. Furthermore, applying a constant potential to one of the pair of gates can improve the stability of the electrical characteristics of the transistor. For example, one gate of the transistor can be connected to a wiring to which a constant potential is applied. Alternatively, one gate of the transistor can be connected to a source or a drain.

[0259] 6C is an example in which transistors M1 and M3 each have a pair of gates. The pair of gates of the transistor M1 and the transistor M3 are connected to each other. This configuration can shorten the period for writing data to the pixel circuit.

[0260] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0261] Embodiment 2 In this embodiment, transistors which can be used for the driver circuits 301, 302, and 303, and the pixels 10 and 11 described in Embodiment 1 will be described.

[0262] <Transistor Configuration Example 1> The transistor shown in FIG. 7A includes a conductive layer 221 functioning as a gate, an insulating layer 211 functioning as a gate insulating layer, conductive layers 222a and 222b functioning as a source and a drain, a semiconductor layer 231, an insulating layer 213 functioning as a gate insulating layer, and a conductive layer 223 functioning as a gate. An insulating layer 215 is provided over the transistor. Here, the same hatching pattern is applied to multiple layers obtained by processing the same conductive film. The insulating layer 211 is located over the conductive layer 221. The semiconductor layer 231 has a portion that overlaps with the conductive layer 221 with the insulating layer 211 sandwiched therebetween. The insulating layer 211 is located between the conductive layer 221 and the semiconductor layer 231. The insulating layer 213 is located between the conductive layer 223 and the semiconductor layer 231. The transistor has a structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates. The transistor can be driven by connecting the two gates and supplying the same signal to them. Alternatively, the transistor can be driven by applying a potential for controlling the threshold voltage to one of the two gates and applying a driving potential to the other.

[0263] 7B includes a conductive layer 221 functioning as a gate, an insulating layer 211 functioning as a gate insulating layer, a semiconductor layer 231 including a channel formation region 231i and a pair of low-resistance regions 231n, a conductive layer 222a connected to one of the pair of low-resistance regions 231n, a conductive layer 222b connected to the other of the pair of low-resistance regions 231n, an insulating layer 225 functioning as a gate insulating layer, a conductive layer 223 functioning as a gate, and an insulating layer 215 covering the conductive layer 223. The insulating layer 211 is located over the conductive layer 221. The semiconductor layer 231 has a portion overlapping with the conductive layer 221 with the insulating layer 211 sandwiched therebetween. The insulating layer 211 is located between the conductive layer 221 and the channel formation region 231i. The insulating layer 225 is located at least between the conductive layer 223 and the channel formation region 231i. Furthermore, an insulating layer 218 covering the transistor may be provided.

[0264] 7B shows an example in which the insulating layer 225 covers the top surface and side surfaces of the semiconductor layer 231. The conductive layer 222a and the conductive layer 222b are connected to the low-resistance region 231n through openings provided in the insulating layer 225 and the insulating layer 215, respectively. One of the conductive layer 222a and the conductive layer 222b functions as a source, and the other functions as a drain.

[0265] 7C , the insulating layer 225 overlaps with the channel formation region 231i of the semiconductor layer 231 but does not overlap with the low-resistance region 231n. For example, the insulating layer 225 is processed using the conductive layer 223 as a mask, thereby manufacturing the structure shown in FIG. 7C . In FIG. 7C , the insulating layer 215 is provided to cover the insulating layer 225 and the conductive layer 223, and the conductive layer 222a and the conductive layer 222b are each connected to the low-resistance region 231n through openings in the insulating layer 215.

[0266] 14A is a plan view of a transistor 200C that can be used in a semiconductor device according to one embodiment of the present invention, and FIG. 14B is a cross-sectional view taken along the line A1-A2 indicated by a dashed dotted line in FIG.

[0267] The transistor 200C includes an insulating layer 402 over a substrate 401 and a conductive layer 251 over the insulating layer 402. The transistor 200C also includes an insulating layer 257 over the conductive layer 251, an insulating layer 258 over the insulating layer 257, and an insulating layer 259 over the insulating layer 258. Note that in this specification and the like, the insulating layer 257, the insulating layer 258, and the insulating layer 259 may be collectively referred to as an insulating layer 256 or a spacer layer. The transistor 200C also includes a conductive layer 261 over the insulating layer 259.

[0268] In addition, an opening 262 is provided in the conductive layer 261, the insulating layer 259, the insulating layer 258, and the insulating layer 257 in a region overlapping with part of the conductive layer 251. In addition, a semiconductor layer 263 is provided to cover the opening 262.

[0269] The semiconductor layer 263 has a region overlapping with the bottom of the opening 262 and a region overlapping with the side surface of the opening 262. That is, the semiconductor layer 263 has a region in contact with the insulating layer 256 in the opening 262. The semiconductor layer 263 also has a region in contact with the conductive layer 251 and a region in contact with the conductive layer 261 in the opening 262.

[0270] An insulating layer 264 is provided over the insulating layer 259, the conductive layer 261, and the semiconductor layer 263. A conductive layer 265 is provided over the insulating layer 264. The conductive layer 265 has a region overlapping with the semiconductor layer 263. The conductive layer 265 has a region overlapping with the semiconductor layer 263 with the insulating layer 264 interposed therebetween.

[0271] The insulating layer 264 and the conductive layer 265 each have a region overlapping with the opening 262. The insulating layer 264 and the conductive layer 265 each have a region overlapping with the opening 262. In the opening 262, the semiconductor layer 263 has a region overlapping with the conductive layer 265 with the insulating layer 264 interposed therebetween and a region overlapping with a side surface of the opening 262 (a side surface of the insulating layer 256).

[0272] Furthermore, an insulating layer 266 is provided on the insulating layer 264. Note that the upper surface of the insulating layer 266 is preferably flat. Alternatively, the heights (positions in the Z direction) of the upper surfaces of the insulating layer 266 and the conductive layer 265 may be the same. For example, the flatness of the upper surface of the insulating layer 266 can be improved by performing chemical mechanical polishing (CMP) processing or the like. Furthermore, the heights of the upper surfaces of the insulating layer 266 and the conductive layer 265 can be made the same by performing CMP processing. By performing CMP processing, unevenness on the sample surface can be reduced, and the coverage of the insulating layer and conductive layer to be formed subsequently can be improved.

[0273] When an oxide semiconductor is used for the semiconductor layer 263, it is preferable to use a material that is difficult to oxidize for the conductive layer 251 in contact with the semiconductor layer 263 and the conductive layer 261 in contact with the semiconductor layer 263. For example, it is preferable to use an oxide conductive layer. By using a material that is difficult to oxidize, the resistance information of the conductive layer can be suppressed. It is also preferable to use a conductive material that makes the oxide semiconductor n-type. For example, a conductive material containing nitrogen may be used. For example, a conductive material containing titanium or tantalum and nitrogen may be used. Furthermore, another conductive material may be provided over the conductive material containing nitrogen.

[0274] When an oxide semiconductor is used for the semiconductor layer 263, it is preferable to use a material containing oxygen and having reduced hydrogen for the insulating layer 258. For example, a material containing silicon and oxygen may be used. Specifically, silicon oxide or silicon oxynitride may be used. Since hydrogen is an impurity element in an oxide semiconductor, contact between the semiconductor layer 263, which is an oxide semiconductor, and the insulating layer 258 in which hydrogen is reduced makes it difficult for the semiconductor layer 263 to become n-type. Furthermore, contact between the semiconductor layer 263, which is an oxide semiconductor, and the insulating layer 258 containing oxygen reduces oxygen vacancies in the semiconductor layer 263, thereby stabilizing the characteristics of the transistor and improving its reliability.

[0275] In the case where an oxide semiconductor is used for the semiconductor layer 263, the insulating layer 258 may contain excess oxygen. In this specification and the like, "excess oxygen" refers to oxygen that is desorbed by heating. A material that desorbs oxygen by heating is a material from which the amount of desorbed oxygen, converted into oxygen atoms, is 1.0×10 atoms / cm or more, preferably 1.0×10 atoms / cm or more, more preferably 2.0×10 atoms / cm or more, or 3.0×10 atoms / cm or more, in thermal desorption spectroscopy (TDS) analysis. Note that the surface temperature of the film during the TDS analysis is preferably in the range of 100° C. to 700° C. or 100° C. to 400° C.

[0276] Furthermore, when a material containing excess oxygen is used for the insulating layer 258, a material through which oxygen is not easily transmitted may be used for the insulating layers 257 and 259. Examples of the material through which oxygen is not easily transmitted include an oxide containing one or both of aluminum and hafnium, and a nitride of silicon. By using a material through which oxygen is not easily transmitted for the insulating layers 257 and 259, excess oxygen contained in the insulating layer 258 is not easily released into a lower or upper layer. Therefore, sufficient oxygen can be supplied to the oxide semiconductor. For example, a structure may be used in which an insulating layer containing silicon and oxygen (the insulating layer 258) is provided between two insulating layers containing silicon and nitrogen (the insulating layer 257 and the insulating layer 259).

[0277] When an oxide semiconductor is used for the semiconductor layer 263, by using a material containing hydrogen for the insulating layers 257 and 259, hydrogen is supplied to a region of the semiconductor layer 263 in contact with the insulating layer 257 and a region of the semiconductor layer 263 in contact with the insulating layer 259, and each region of the semiconductor layer 263 becomes n-type. Therefore, the region of the semiconductor layer 263 in contact with the conductive layer 261 and the region of the semiconductor layer 263 in contact with the insulating layer 259 function as one of the source region and the drain region. The region of the semiconductor layer 263 in contact with the conductive layer 251 and the region of the semiconductor layer 263 in contact with the insulating layer 257 function as the other of the source region and the drain region.

[0278] The conductive layer 261 functions as one of the source electrode and the drain electrode of the transistor 200C. The conductive layer 251 functions as the other of the source electrode and the drain electrode of the transistor 200C. The transistor 200C is a transistor in which the source electrode and the drain electrode are arranged in the Z direction. That is, the source and the drain of the transistor 200C are arranged at different heights. In other words, the source and the drain of the transistor 200C are arranged at different positions in the Z direction. Such a transistor is also called a "vertical channel transistor," "vertical channel transistor," "vertical transistor," or "VFET (Vertical Field Effect Transistor)."

[0279] In the above configuration, in the transistor 200C, which is a VFET, the length of the side surface of the insulating layer 158 as viewed in the X direction or the Y direction is the channel length L (channel length L1) (see FIG. 14B). Therefore, the channel length L of the transistor 200C is determined depending on the thickness t1 of the insulating layer 258.

[0280] Alternatively, the insulating layers 257 and 259 may be formed using a material that does not contain hydrogen or contains very little hydrogen. For example, silicon nitride or silicon nitride oxide containing very little hydrogen may be used. In this case, the region of the semiconductor layer 263 in contact with the insulating layer 257 and the region of the semiconductor layer 263 in contact with the insulating layer 259 are not made n-type. Therefore, the region of the semiconductor layer 263 in contact with the conductive layer 261 functions as one of the source region and the drain region. The region of the semiconductor layer 263 in contact with the conductive layer 251 functions as the other of the source region and the drain region. The region of the semiconductor layer 263 in contact with the insulating layer 258 functions as a channel formation region.

[0281] In this case, the sum of the lengths of the side surfaces of the insulating layers 257, 258, and 259 as viewed from the X direction or the Y direction is the channel length L (channel length L2). Therefore, the channel length L of the transistor 200C is determined according to the total thickness t2 of the insulating layers 257, 258, and 259. In this way, the transistor 200C has a channel formation region that extends along the side surface of the insulating layer 256.

[0282] Furthermore, because the semiconductor layer 263 is provided in the opening 262, the perimeter of the opening 262 as viewed from the Z direction is the channel width W of the transistor 200C (see FIG. 14A ). The perimeter can be determined, for example, at a position halfway through the thickness t1 or halfway through the thickness t2 of the insulating layer 258. Note that, as needed, the perimeter of any position on the opening 262 may be used as the channel width W. For example, the perimeter of the bottom of the opening 262 may be used as the channel width W, or the perimeter of the top of the opening 262 may be used as the channel width W. Although FIG. 14A shows the outline (planar shape) of the opening 262 as viewed from the Z direction as a circle, this is not limiting. For example, the outline of the opening 262 as viewed from the Z direction may be an ellipse or a rectangle.

[0283] In the memory device of one embodiment of the present invention, the channel length L is preferably smaller than at least the channel width W. In one embodiment of the present invention, the channel length L is 0.1 to 0.99 times, preferably 0.5 to 0.8 times, the channel width W.

[0284] Furthermore, in order to improve coverage of the semiconductor layer 263, the insulating layer 264, and the conductive layer 265 formed inside the opening 262, the taper angle θ of the side surface of the opening 262, i.e., the taper angle θ of each of the side surfaces of the insulating layer 257, the insulating layer 258, and the insulating layer 259, may be set to 45° or more and 90° or less, preferably 50° or more and 75° or less. Note that the taper angle θ of the side surface of a layer (insulating layer, conductive layer, or semiconductor layer) refers to the angle formed between the bottom surface and the side surface of the layer (see FIG. 14B ).

[0285] A vertical transistor can occupy a smaller area than a transistor (also called a "horizontal transistor") in which a channel formation region, a source region, and a drain region are separately provided on the XY plane. Therefore, by using a vertical channel transistor in a semiconductor device, the area occupied by the semiconductor device can be reduced. Furthermore, by using a vertical channel transistor in a semiconductor device, high integration of the semiconductor device can be achieved.

[0286] Furthermore, in a lateral transistor, the channel length is limited by the exposure limit of photolithography, making further miniaturization difficult. In a vertical channel transistor according to one embodiment of the present invention, the channel length can be set by the thickness of the insulating layer 256 or 258. Therefore, the channel length of the transistor can be made into a very fine structure (e.g., 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less, and 1 nm or more or 5 nm or more) that is equal to or less than the exposure limit of photolithography. This increases the on-state current of the transistor 200C, thereby improving frequency characteristics. By using a vertical channel transistor, a semiconductor device with high operating speed can be provided.

[0287] <Transistor Structure Example 4> Fig. 15A is a plan view of a transistor 200D that can be used for a semiconductor device of one embodiment of the present invention. Fig. 15B is a cross-sectional view taken along the line A1-A2 indicated by a dashed dotted line in Fig. 15A. Fig. 15C is a cross-sectional view taken along the line A3-A4 indicated by a dashed dotted line in Fig. 15A. Note that Fig. 15A is a cross-sectional view of the transistor 200D in the channel length direction, and Fig. 15C is a cross-sectional view of the transistor 200D in the channel width direction.

[0288] 15A to 15C , the transistor 200D includes a semiconductor layer 520 disposed over a substrate 501, conductive layers 542a and 542b spaced apart from each other on the semiconductor layer 520, an insulating layer 580 disposed over the conductive layers 542a and 542b and having an opening formed between the conductive layers 542a and 542b, a conductive layer 560 disposed in the opening, and an insulating layer 550 disposed among the semiconductor layer 520, the conductive layers 542a and 542b, the insulating layer 580, and the conductive layer 560. Note that hereinafter, the conductive layers 542a and 542b may be collectively referred to as the conductive layer 542.

[0289] 15A to 15C , an insulating layer 554 is disposed between the insulating layer 524, the semiconductor layer 520, the conductive layer 542a, the conductive layer 542b, and the insulating layer 580. The insulating layer 554 is in contact with the top surface and side surfaces of the conductive layer 542a, the top surface and side surfaces of the conductive layer 542b, the side surfaces of the semiconductor layer 520, and the top surface of the insulating layer 524.

[0290] Here, the conductive layer 560 functions as the gate electrode of the transistor, and the conductive layers 542a and 542b function as source and drain electrodes, respectively. The conductive layer 560 is formed so as to fill the opening of the insulating layer 580 and the region sandwiched between the conductive layers 542a and 542b. The conductive layers 560, 542a, and 542b are arranged in a self-aligned manner with respect to the opening of the insulating layer 580. That is, in the transistor 200D, the gate electrode can be arranged between the source and drain electrodes in a self-aligned manner. Therefore, the conductive layer 560 can be formed without providing a margin for alignment, thereby reducing the area occupied by the transistor 200D. This reduces the area occupied by the semiconductor device. Furthermore, the integration density of the semiconductor device can be increased.

[0291] 15A to 15C , the conductive layer 560 includes a conductive layer 560a provided inside the insulating layer 550 and a conductive layer 560b provided to be embedded in the conductive layer 560a. Although the conductive layer 560 in the transistor 200D has a two-layer stacked structure, one embodiment of the present invention is not limited to this. For example, the conductive layer 560 may have a single-layer structure or a stacked structure of three or more layers.

[0292] The transistor 200D includes an insulating layer 502 disposed on a substrate 501, an insulating layer 514 disposed on the insulating layer 502, an insulating layer 516 disposed on the insulating layer 514, a conductive layer 505 disposed so as to be embedded in the insulating layer 516, an insulating layer 522 disposed on the insulating layer 516 and the conductive layer 505, and an insulating layer 524 disposed on the insulating layer 522. Furthermore, a semiconductor layer 520 is disposed on the insulating layer 524.

[0293] Further, insulating layers 574 and 581 functioning as interlayer films are provided over the transistor 200D. The insulating layer 574 is provided in contact with top surfaces of the conductive layer 560, the insulating layer 550, and the insulating layer 580.

[0294] When an oxide semiconductor is used for the semiconductor layer 520, the insulating layers 514, 522, 554, and 574 may be insulating layers having a function of suppressing diffusion of hydrogen (for example, at least one of hydrogen atoms, hydrogen molecules, and the like). For example, the insulating layers 514, 522, 554, and 574 may be insulating layers having lower hydrogen permeability than the insulating layers 524, 550, and 580. The insulating layers 514, 522, and 554 may be insulating layers having a function of suppressing diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, and the like). For example, the insulating layers 514, 522, and 554 may be insulating layers having lower oxygen permeability than the insulating layers 524, 550, and 580. When the conductive layer 505 functions as a gate electrode, the insulating layer 522 is preferably formed using a material suitable for a gate insulating layer.

[0295] Here, the insulating layer 524, the semiconductor layer 520, and the insulating layer 550 are separated by the insulating layer 522 and the insulating layer 574. Therefore, impurities such as hydrogen and excess oxygen contained in layers above the insulating layer 574 and below the insulating layer 522 can be prevented from being mixed into the insulating layer 524, the semiconductor layer 520, and the insulating layer 550.

[0296] 15B shows an example in which a conductive layer 545 that is connected to the transistor 200D and functions as a plug is provided. Note that an example in which an insulating layer 541 is provided in contact with a side surface of the conductive layer 545 that functions as a plug is shown. That is, the insulating layer 541 is provided in contact with inner walls of openings of the insulating layer 554, the insulating layer 580, the insulating layer 574, and the insulating layer 581.

[0297] Here, the height of the top surface of the conductive layer 545 can be made approximately the same as the height of the top surface of the insulating layer 581. Note that although the transistor 200D has a structure in which the first conductive layer of the conductive layer 545 and the second conductive layer of the conductive layer 545 are stacked, one embodiment of the present invention is not limited to this. For example, the conductive layer 545 may have 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.

[0298] Furthermore, the thickness of the semiconductor layer 520 in a region that does not overlap with the conductive layer 542 may be thinner than the thickness of the region that overlaps with the conductive layer 542. This is achieved by removing part of the top surface of the semiconductor layer 520 when forming the conductive layers 542a and 542b. When a conductive film that will become the conductive layer 542 is formed on the top surface of the semiconductor layer 520, a low-resistance region may be formed near the interface with the conductive film. In this way, by removing the low-resistance region located between the conductive layer 542a and the conductive layer 542b on the top surface of the semiconductor layer 520, it is possible to prevent a channel from being formed in the region.

[0299] The conductive layer 505 is arranged to have a region overlapping with the conductive layer 560 with the semiconductor layer 520 interposed therebetween. By providing the conductive layer 505 so as to be embedded in the insulating layer 516, unevenness on the top surfaces of the conductive layer 505 and the insulating layer 516 can be reduced, and coverage with layers formed in later steps can be improved.

[0300] When an oxide semiconductor is used for the semiconductor layer 520, the conductive layer 505 is made of a conductive material that has a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), and copper atoms. Alternatively, a conductive material that has a function of suppressing diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) is used. Examples of conductive materials that have a function of suppressing diffusion of oxygen include titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, and ruthenium oxide. The conductive layer may also contain a conductive material containing tungsten, copper, or aluminum as a main component. When the conductive layer 560 is used as a gate electrode, the conductive layer 505 functions as a backgate electrode.

[0301] The conductive layer 505 may be provided to be larger than the channel formation region in the semiconductor layer 520. In particular, as shown in Fig. 15C, the conductive layer 505 may extend to a region outside the end portion intersecting with the channel width direction of the semiconductor layer 520. In other words, the conductive layer 505 and the conductive layer 560 may overlap with each other with an insulating layer interposed therebetween on the outside of the side surface of the semiconductor layer 520 in the channel width direction.

[0302] With the above structure, the channel formation region of the semiconductor layer 520 can be surrounded by the electric field of the conductive layer 560 functioning as a gate electrode and the electric field of the conductive layer 505 functioning as a back gate electrode.

[0303] For example, the insulating layer 514 can be made of aluminum oxide, silicon nitride, or the like.

[0304] For example, an insulating layer containing an oxide of one or both of aluminum and hafnium, which are insulating materials, can be used as the insulating layer 522. As the insulating layer containing an oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like may be used.

[0305] 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 insulating layers. Alternatively, these insulating layers may be nitrided. Furthermore, silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the insulating layer. For example, the insulating layer 522 may have a three-layer structure in which silicon nitride, silicon oxide, and aluminum oxide are stacked in this order.

[0306] The insulating layer 522 may be a single layer or a multilayer insulating layer containing a so-called high-k material, such as aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As transistors become smaller and more highly integrated, problems such as leakage current may occur due to thinner gate insulating layers. Using a high-k material for the insulating layer that functions as the gate insulating layer makes it possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0307] The insulating layer 516, the insulating layer 580, and the insulating layer 581, which function as interlayer films, can be formed using an insulating material having a lower dielectric constant than the insulating layer 514. For example, the insulating layer 516, the insulating layer 580, and the insulating layer 581 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, silicon oxide having vacancies, or the like as appropriate.

[0308] Silicon oxide, silicon oxynitride, or the like can be used as the insulating layer 524. The insulating layer 524 in contact with the semiconductor layer 520 may contain excess oxygen. By providing an insulating layer containing oxygen in contact with the semiconductor layer 520, oxygen vacancies in the semiconductor layer 520 are reduced, and the reliability of the transistor 200D is improved.

[0309] A conductive layer 542 (a conductive layer 542a and a conductive layer 542b) functioning as a source electrode and a drain electrode is provided over the semiconductor layer 520. When an oxide semiconductor is used for the semiconductor layer 520, the conductive layer 542 may be formed using a conductive material that is not easily oxidized or a conductive material that maintains its conductivity even when it absorbs oxygen.

[0310] A region of the semiconductor layer 520 in contact with the conductive layer 542 functions as a source region or a drain region of the transistor 200D. Here, the region between the conductive layer 542a and the conductive layer 542b is formed to overlap with the opening of the insulating layer 580. This allows the conductive layer 560 to be disposed in a self-aligned manner between the conductive layer 542a and the conductive layer 542b.

[0311] The insulating layer 550 functions as a gate insulating layer. The insulating layer 550 is disposed in contact with the top surface of the semiconductor layer 520.

[0312] Silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine has been added, silicon oxide to which carbon has been added, silicon oxide to which carbon and nitrogen have been added, silicon oxide having vacancies, and the like can be suitably used as the gate insulating layer.

[0313] The insulating layers 524 and 550 preferably have a reduced concentration of impurities such as water or hydrogen.

[0314] Although the conductive layer 560 is shown as having a two-layer structure in FIGS. 15A to 15C, it may have a single-layer structure or a stacked structure of three or more layers.

[0315] The conductive layer 560a may be a conductive layer having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), copper atoms, etc. Alternatively, a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) may be used.

[0316] The conductive layer 560a has a function of suppressing oxygen diffusion, which can suppress a decrease in conductivity due to oxidation of the conductive layer 560b caused by oxygen contained in the insulating layer 550. Examples of conductive materials that can suppress oxygen diffusion include tantalum, tantalum nitride, ruthenium, and ruthenium oxide.

[0317] The conductive layer 560b may be made of a conductive material containing tungsten, copper, or aluminum as a main component. Furthermore, since the conductive layer 560 also functions as a wiring, a conductive layer with high conductivity may be used. For example, a conductive material containing tungsten, copper, or aluminum as a main component may be used. Furthermore, the conductive layer 560b may have a layered structure, for example, a layered structure of titanium or titanium nitride and the above-mentioned conductive material.

[0318] 15B and 15C , in a region of the semiconductor layer 520 that does not overlap with the conductive layer 542, in other words, in a channel formation region of the semiconductor layer 520, the side surface of the semiconductor layer 520 is arranged to be covered with the conductive layer 560. This makes it easier for the electric field of the conductive layer 560, which functions as the gate electrode of the transistor 200D, to act on the side surface of the semiconductor layer 520. This increases the on-state current of the transistor 200D and improves its frequency characteristics.

[0319] A conductive layer 545 is placed in the openings formed in the insulating layer 581, the insulating layer 574, the insulating layer 580, and the insulating layer 554. The conductive layers 545 are provided opposite to each other with the conductive layer 560 interposed therebetween. Note that the height of the top surface of the conductive layer 545 may be flush with the top surface of the insulating layer 581.

[0320] The conductive layer 545 may be made of a conductive material containing tungsten, copper, or aluminum as a main component.

[0321] When the conductive layer 545 has a stacked structure, a conductive layer having a function of suppressing diffusion of impurities such as water or hydrogen may be used as a conductive layer in contact with the semiconductor layer 520, the conductive layer 542, the insulating layer 554, the insulating layer 580, the insulating layer 574, and the insulating layer 581. For example, tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or ruthenium oxide is used. By using such a conductive material, oxygen contained in the insulating layer 580 can be prevented from being absorbed by the conductive layer 545. Furthermore, impurities such as water or hydrogen from above the insulating layer 581 can be prevented from entering the semiconductor layer 520 through the conductive layer 545.

[0322] The insulating layer 541 may be, for example, an insulating layer that can be used for the insulating layer 554. The insulating layer 541 is provided in contact with the insulating layer 554, and therefore can prevent impurities such as water or hydrogen from the insulating layer 580 or the like from being mixed into the semiconductor layer 520 through the conductive layer 545. Furthermore, oxygen contained in the insulating layer 580 can be prevented from being absorbed by the conductive layer 545.

[0323] [Semiconductor Layer] A semiconductor layer included in a transistor of one embodiment of the present invention will be described.

[0324] The semiconductor layer can be formed using an oxide semiconductor, such as a metal oxide.

[0325] Furthermore, the semiconductor layer may be made of a transistor using other semiconductor materials, such as semiconductors made of simple elements or compound semiconductors.

[0326] Examples of semiconductors made of elemental elements that can be used as semiconductor materials include silicon and germanium. Examples of silicon that can be used as semiconductor materials include single-crystal silicon, polycrystalline silicon, microcrystalline silicon, and amorphous silicon. Examples of polycrystalline silicon include low-temperature polysilicon (LTPS).

[0327] Compound semiconductors that can be used for the semiconductor material include silicon carbide, silicon germanium, gallium arsenide, indium phosphide, boron nitride, and boron arsenide. Boron nitride that can be used for the semiconductor layer preferably has an amorphous structure. Boron arsenide that can be used for the semiconductor layer preferably has a cubic crystal structure. Other examples of compound semiconductors include organic semiconductors and nitride semiconductors. The aforementioned metal oxides are also a type of compound semiconductor. These semiconductor materials may contain impurities as dopants.

[0328] Hereinafter, an example in which an oxide semiconductor is used for the semiconductor layer will be described.

[0329] The crystallinity of the semiconductor material used for the oxide semiconductor is not particularly limited, and any of an amorphous semiconductor, a single crystal semiconductor, and a semiconductor having crystallinity other than single crystal (a microcrystalline semiconductor, a polycrystalline semiconductor, or a semiconductor having a crystalline region in part) may be used. The use of a single crystal semiconductor or a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0330] In a transistor using an oxide semiconductor for a channel formation region (hereinafter referred to as an OS transistor), the electrical characteristics may fluctuate and reliability may decrease if oxygen vacancies (VO) and impurities are present in the channel formation region in the metal oxide. Furthermore, defects (hereinafter sometimes referred to as VOH) caused by hydrogen entering the oxygen vacancies may be formed, generating electrons that serve as carriers. Therefore, if the channel formation region in the metal oxide contains oxygen vacancies, the OS transistor is likely to be normally on. Therefore, it is preferable that the oxygen vacancies and impurities are reduced as much as possible in the channel formation region in the metal oxide. In other words, it is preferable that the carrier concentration in the channel formation region in the metal oxide be reduced and the channel formation region in the metal oxide be made i-type (intrinsic) or substantially i-type.

[0331] On the other hand, the source and drain regions of an OS transistor are preferably regions having a higher oxygen vacancy, a higher VOH, or a higher concentration of impurities such as hydrogen, nitrogen, or metal elements than the channel formation region, thereby increasing the carrier concentration and lowering the resistance. That is, the source and drain regions of an OS transistor are preferably n-type regions having a higher carrier concentration and lower resistance than the channel formation region.

[0332] The band gap of a metal oxide functioning as a semiconductor is preferably 2.0 eV or more, more preferably 2.5 eV or more. By using a metal oxide with a wide band gap for an oxide semiconductor layer, the off-state current of a transistor can be reduced. Because the off-state current of an OS transistor is small, the power consumption of a semiconductor device can be sufficiently reduced. Furthermore, because the frequency characteristics of an OS transistor are high, the semiconductor device can operate at high speed.

[0333] For example, examples of metal oxides that can be used for the semiconductor layer of an OS transistor include indium oxide (In oxide, also referred to as indium oxide). Examples of the metal oxide include zinc oxide (Zn oxide, also referred to as zinc oxide), indium zinc oxide (In—Zn oxide), indium tin oxide (In—Sn oxide), indium titanium oxide (In—Ti oxide), indium gallium oxide (In—Ga oxide), indium gallium aluminum oxide (In—Ga—Al oxide), indium gallium tin oxide (In—Ga—Sn oxide), gallium zinc oxide (Ga—Zn oxide, also referred to as “GZO”), aluminum zinc oxide (Al—Zn oxide, also referred to as “AZO”), and indium. Examples of the usable materials include indium aluminum zinc oxide (In-Al-Zn oxide, also referred to as "IAZO"), indium tin zinc oxide (In-Sn-Zn oxide), indium titanium zinc oxide (In-Ti-Zn oxide), indium gallium zinc oxide (In-Ga-Zn oxide, also referred to as "IGZO"), indium gallium tin zinc oxide (In-Ga-Sn-Zn oxide, also referred to as "IGZTO"), and indium gallium aluminum zinc oxide (In-Ga-Al-Zn oxide, also referred to as "IGAZO" or "IAGZO"). Alternatively, silicon-containing indium tin oxide, gallium tin oxide (Ga-Sn oxide), aluminum tin oxide (Al-Sn oxide), and the like can be used.

[0334] Examples of the crystalline structure of metal oxides that function as semiconductors include amorphous (including completely amorphous), c-axis-aligned crystalline line (CAAC), nanocrystalline line (nc), cloud-aligned composite (CAC), single crystal, and polycrystalline.

[0335] Furthermore, by increasing the ratio of the number of zinc atoms to the total number of atoms of the metal elements among the main component elements contained in the metal oxide, the metal oxide can be made highly crystalline, and the diffusion of impurities in the metal oxide can be suppressed, thereby suppressing fluctuations in the electrical characteristics of the transistor and improving its reliability.

[0336] Furthermore, by increasing the ratio of the number of atoms of element M to the sum of the number of atoms of metal elements among the main component elements contained in the metal oxide, the formation of oxygen vacancies in the metal oxide can be suppressed. Therefore, carrier generation due to oxygen vacancies can be suppressed, and a transistor with a small off-state current can be obtained. Furthermore, fluctuations in the electrical characteristics of the transistor can be suppressed, and reliability can be improved.

[0337] By increasing the ratio of the number of indium atoms to the sum of the numbers of atoms of all metal elements contained in the metal oxide, the field-effect mobility of the transistor can be increased. Typically, by using single-crystal or polycrystalline indium oxide for the semiconductor layer, the field-effect mobility of the transistor can be significantly increased. Furthermore, a transistor using single-crystal or polycrystalline indium oxide for the semiconductor layer can achieve good frequency characteristics.

[0338] For example, the oxide semiconductor layer of one embodiment of the present invention includes a crystalline metal oxide. Examples of the structure of the crystalline metal oxide include a CAAC structure, a polycrystalline (poly-crystalline) structure, and an nc structure. By using a crystalline metal oxide for the oxide semiconductor layer, the density of defect states in the oxide semiconductor layer can be reduced. Therefore, the reliability of a transistor including the oxide semiconductor layer of one embodiment of the present invention can be improved, and the reliability of a semiconductor device including the transistor can be improved.

[0339] Indium oxide that can be used for the oxide semiconductor layer of one embodiment of the present invention will be described below.

[0340] In this specification and the like, indium oxide having at least a crystalline portion or a crystalline region in a film is referred to as crystalline indium oxide (crystal IO) or crystalline indium oxide (crystalline IO). Examples of crystalline IO or crystalline IO include single-crystalline indium oxide, polycrystalline indium oxide, and microcrystalline indium oxide.

[0341] Indium oxide is a semiconductor material having physical properties that are completely different from those of oxide semiconductors such as In—Ga—Zn oxide (hereinafter also referred to as IGZO) and zinc oxide.

[0342] The carrier concentration dependence of the Hall mobility of indium oxide, silicon, and IGZO will be described below. Fig. 16A is a schematic diagram showing the carrier concentration dependence of the Hall mobility for silicon (Si) and indium oxide (InOX), and Fig. 16B is a schematic diagram showing the carrier concentration dependence of the Hall mobility for IGZO.

[0343] First, IGZO tends to exhibit higher hole mobility as the carrier concentration increases, as shown by the arrows in Figure 16B. On the other hand, indium oxide tends to exhibit higher hole mobility as the carrier concentration decreases, as shown by the arrows in Figure 16A (see Non-Patent Document 1). This trend is similar to that of silicon; the lower the dopant (impurity) concentration in the material, the less impurity scattering there is and the higher the hole mobility. In other words, the higher the purity and intrinsic indium oxide, the higher the hole mobility. From these results, it can be said that indium oxide, unlike IGZO, is a material with physical properties similar to those of silicon. Note that the characteristics of indium oxide shown in Figure 16A are assumed to be single crystal. Therefore, when indium oxide is non-single crystal (e.g., polycrystalline), the characteristics may differ from those shown in Figure 16A.

[0344] 16A, the low carrier concentration range R1 has extremely high hole mobility, and can therefore be considered a suitable carrier concentration range for, for example, a transistor channel formation region. For example, in the case of indium oxide, range R1 is a range including a carrier concentration value of 1×10 cm −3 , e.g., a range of 1×10 cm −3 or more and 1×10 cm −3 or less. By sufficiently reducing the carrier concentration, it is expected that the hole mobility value can be increased to approximately 270 cm −2 / (V s).

[0345] In addition, in indium oxide, the region where the carrier concentration is in the range R1 may contain an element that lowers the carrier concentration. Examples of elements that lower the carrier concentration include magnesium, calcium, zinc, cadmium, and copper. By substituting these elements for indium, the carrier concentration can be lowered. Examples of elements that lower the carrier concentration include nitrogen, phosphorus, arsenic, and antimony. For example, by substituting nitrogen, phosphorus, arsenic, or antimony for oxygen, the carrier concentration can be lowered.

[0346] On the other hand, the range R2 with a high carrier concentration has a low electrical resistance, and can be said to be a range of carrier concentrations suitable for, for example, the source and drain regions of a transistor, a resistor, or a transparent conductive film. Range R2 is a range in which the carrier concentration value includes 1×10 cm, for example, a range of 1×10 cm or more and 1×10 cm or less. By sufficiently increasing the carrier concentration, it is expected that the resistivity can be reduced to 1×10 Ω cm or less.

[0347] In the indium oxide, the region having a carrier concentration in the range R2 may contain an element that increases the carrier concentration. For example, it is preferable that the indium oxide contains an element that is common to the source electrode and the drain electrode of the transistor. Examples of elements that increase the carrier concentration include titanium, zirconium, hafnium, tantalum, tungsten, molybdenum, tin, silicon, and boron. In particular, it is more preferable to use an element whose oxide has conductive or semiconductive properties.

[0348] In this way, indium oxide uses a region with a low carrier concentration as the channel formation region of a transistor, and a region with a high carrier concentration as the source and drain regions of the transistor. In other words, indium oxide can be said to be an oxide capable of valence electron control. Note that IGZO may experience strain in the source and drain regions due to stress from electrodes in contact with the IGZO, resulting in the formation of n-type regions. On the other hand, unlike IGZO, indium oxide is capable of valence electron control, and therefore does not require strain to be formed in the film as with IGZO. Less strain in the film is expected to improve reliability. For example, by separately creating a region with a carrier concentration in the range R1 shown in FIG. 16A and a region with a carrier concentration in the range R2 in the indium oxide film, a so-called n-i-n junction (a junction between an n-type region, an i-type region, and an n-type region) can be created. Note that valence electron control in transistors using silicon is generally known. On the other hand, valence electron control in transistors using indium oxide is a novel technical concept that would not normally be conceived.

[0349] By using the above technical concept, the transistor having indium oxide in this specification and the like has two or more, preferably three or more, more preferably four or more, and most preferably five of the following characteristics (1) to (5): (1) high on-current (in other words, high mobility); (2) low off-current; (3) normally-off operation; (4) high reliability; and (5) high cutoff frequency (fT). For example, the transistor having indium oxide in this specification and the like has high mobility, low off-current, and is normally-off operation. The transistor has high mobility and is different from a normally-on transistor.

[0350] Next, an indium oxide film applied to a transistor will be described. The indium oxide film preferably has crystallinity (i.e., has crystal grains). Examples of films having crystal grains include single-crystal films, polycrystalline films, and amorphous films containing crystal grains (also called microcrystalline films). In particular, the indium oxide film is preferably a polycrystalline film, and more preferably a single-crystal film. A single-crystal film does not have grain boundaries. Impurities (typically, insulating impurities, insulating oxides, etc.) that hinder carrier flow tend to segregate at grain boundaries. The use of a single-crystal film can suppress carrier scattering at grain boundaries, thereby realizing a transistor exhibiting high field-effect mobility. Furthermore, the use of a single-crystal film has the excellent effect of suppressing variations in transistor characteristics due to the grain boundaries.

[0351] Furthermore, polycrystalline films are preferable because they can reduce carrier scattering and exhibit high field-effect mobility compared to microcrystalline or amorphous films. When using a polycrystalline film, it is preferable to use a film with as large a crystal grain size as possible and with few crystal grain boundaries. Note that in a transistor using an indium oxide polycrystalline film, if there is no crystal grain boundary in the channel formation region or no crystal grain boundary is observed, the channel formation region is located within a single crystal region included in the polycrystalline film, and therefore the transistor can be considered to be using single-crystal indium oxide.

[0352] The crystallinity of indium oxide can be analyzed by, for example, X-ray diffraction (XRD), transmission electron microscopy (TEM), or electron diffraction (ED). Alternatively, the analysis may be performed by combining a plurality of these techniques.

[0353] In this specification and the like, a semiconductor layer in which no crystal grain boundary is observed in the channel formation region, a semiconductor layer in which the channel formation region is included in one crystal grain, or a semiconductor layer in which the crystal axis direction is the same in at least two regions in the channel formation region can be called a single crystal film. Also, a semiconductor layer in which, in the channel formation region, within one crystal grain, the direction of another crystal axis continuously changes around a certain crystal axis or a certain crystal orientation as the axis of rotation can be called a single crystal film.

[0354] The channel formation region refers to a region of the semiconductor layer that overlaps (or faces) the gate electrode via the gate insulating layer, and is located between the region in contact with the source electrode and the region in contact with the drain electrode. The current path in the channel formation region is the shortest distance between the source electrode and the drain electrode. Therefore, the crystal grains, crystal grain boundaries, crystal axes, crystal orientation, etc. in the channel formation region can be confirmed by observing a cross section including the semiconductor layer, the source electrode, and the drain electrode.

[0355] The indium oxide film in the channel formation region preferably has a lower impurity concentration. Impurities in the indium oxide film in the channel formation region can be a scattering source of carriers, which can lead to a decrease in field-effect mobility. These impurities can also hinder the crystal growth of the indium oxide film. Examples of impurities in the indium oxide film include boron and silicon. The indium oxide film preferably contains these impurities at concentrations of 0.1% or less, and more preferably 0.01% (100 ppm) or less. Carbon, hydrogen, and other elements may be contained in the film-forming gas or precursor during film formation, and may remain in the indium oxide film in greater amounts than the above-mentioned impurities.

[0356] The indium oxide film in the channel formation region may contain an element that can become the same trivalent cation as indium, as long as the crystal maintains a cubic crystal structure (bixbyite type). Examples of such an element include Group 13 elements of the periodic table, such as gallium and aluminum, and Group 3 elements of the periodic table. These elements exist mainly as trivalent cations in oxides, and therefore the carrier concentration of indium oxide can be maintained low.

[0357] By using such an indium oxide film for a transistor, the field-effect mobility of the transistor can be made 50 cm / (V s) or more, preferably 100 cm / (V s) or more, more preferably 150 cm / (V s) or more, even more preferably 200 cm / (V s) or more, and still more preferably 250 cm / (V s) or more.

[0358] One of the characteristics of an indium oxide film is its high oxygen permeability (diffusibility) compared to an IGZO film. As shown in FIG. 16C, oxygen (O) diffusing into an indium oxide film (denoted as InOX) passes through the indium oxide film and is released as oxygen molecules (O2). It may also react with hydrogen contained in the film and be released as water molecules (H2O). Furthermore, if an oxygen vacancy (VO) exists in the film, the diffusing oxygen atoms compensate for the oxygen vacancy. Since oxygen easily diffuses into an indium oxide film, it can also be said that oxygen vacancies are more easily compensated for compared to an IGZO film.

[0359] As described above, an indium oxide film can more easily reduce oxygen vacancies in the film than an IGZO film. Therefore, by using such an indium oxide film in a transistor, a transistor exhibiting extremely high reliability can be realized.

[0360] 16C, the indium oxide film diffuses hydrogen. Hydrogen that diffuses into the indium oxide film from the outside passes through the indium oxide film and is released as hydrogen molecules (H). Alternatively, hydrogen reacts with oxygen contained in the film and is released as water molecules.

[0361] A transistor using an indium oxide film is an accumulation-type transistor that uses electrons as majority carriers. Assuming that the carrier relaxation time is constant, the smaller the effective mass of the electrons (carriers), the higher the electron mobility. In other words, by using indium oxide, which has a small effective mass of electrons, for a transistor, the on-state current or field-effect mobility of the transistor can be increased.

[0362] Table 4 shows the effective masses of single-crystal indium oxide (here, In2O3) and single-crystal silicon (Si). As shown in Table 4, indium oxide is characterized by a small effective mass of electrons and a large effective mass of holes. Furthermore, the effective mass of electrons in indium oxide is characterized by being almost independent of the crystal orientation. Therefore, by using crystalline indium oxide in a transistor, a transistor with high field-effect mobility and high frequency characteristics (also referred to as f characteristics) can be realized. Furthermore, because the effective mass of holes is large, a transistor with extremely low off-state current can be realized. For example, by applying an indium oxide film to a vertical transistor, the off-state current per 1 μm of channel width can be 1 fA (1×10-15 A) or less or 1 aA (1×10-18 A) or less at 125° C., and 1 aA (1×10-18 A) or less or 1 zA (1×10-21 A) or less at room temperature (25° C.). Furthermore, as shown in Table 4, indium oxide has a smaller effective mass of electrons and a larger effective mass of holes than silicon, and therefore may be able to realize a transistor with higher field-effect mobility and lower off-state current than a Si transistor.

[0363]

[0364] It is preferable to provide a seed layer so as to be in contact with at least a portion of the crystalline indium oxide film. The seed layer is preferably made of a material containing crystals with a small difference in lattice constant (also called lattice mismatch) with indium oxide. This can improve the crystallinity of the indium oxide film. Note that a substrate (e.g., a single-crystal substrate) may be used as one of the layers in contact with at least a portion of the crystalline indium oxide film.

[0365] One method for evaluating the degree of lattice mismatch is to use the lattice mismatch value shown below. The lattice mismatch Δa [%] of the crystals of the formed film (here, an indium oxide film) with respect to the crystals of the seed layer is calculated by Δa = ((L1 - L2) / L2) × 100. Here, L1 is the length or lattice constant of the unit lattice vector of the crystals of the formed film, and L2 is the length or lattice constant of the unit lattice vector of the crystals of the seed layer.

[0366] The smaller the absolute value of the lattice mismatch Δa between the seed layer and the indium oxide film, the more preferable, and it is most preferably 0. For example, Δa can be set to −5% or more and 5% or less, preferably −4% or more and 4% or less, more preferably −3% or more and 3% or less, and even more preferably −2% or more and 2% or less.

[0367] Here, the indium oxide crystal has a cubic crystal structure (bixbyite type). For example, the crystal of yttria-stabilized zirconia (YSZ) can have a cubic crystal structure (fluorite type). The lattice mismatch of the indium oxide crystal with the cubic YSZ crystal is in the range of −2% to 2%, and a single crystal film of indium oxide can be epitaxially grown on the YSZ substrate.

[0368] Note that the crystal structure of the seed layer and the crystal structure of the indium oxide film may not necessarily have the same crystal system or crystal orientation. For example, a film having hexagonal or trigonal crystal structure can be used under an indium oxide film having cubic crystal structure. For example, by setting the crystal orientation of the surface of the seed layer to

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

[111] , the requirements regarding the crystal orientation necessary for epitaxial growth can be met. Examples of hexagonal or trigonal crystals include wurtzite structure, YbFe2O4 structure, Yb2Fe3O7 structure, and modified structures thereof. An example of a crystal having a YbFe2O4 structure or a Yb2Fe3O7 structure is IGZO.

[0369] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0370] Embodiment 3 In this embodiment, a display device according to one embodiment of the present invention will be described.

[0371] <Structure Example 1 of Display Device> FIG. 8 illustrates a cross-sectional view of a display device that is one embodiment of the present invention.

[0372] 8A shows an example of a cross section of a part of a region including the drive circuit 301, a part of a region including the display unit 20, and a part of a region including the drive circuit 303 in the display device shown in FIG. 6A. In the display unit 20, a pixel 10 having a sub-pixel B that emits blue light and a sub-pixel W that emits white light is shown as an example.

[0373] The display device shown in Figure 8A has, between the substrate 110 and the substrate 120, a transistor 201, a transistor 203, a transistor 204, a transistor 205, a light-emitting device 130b included in the sub-pixel G, a light-emitting device 130c included in the sub-pixel B, a light-emitting device 130at included in the sub-pixel R(t), a light-emitting device 130bt included in the sub-pixel G(t), and the like.

[0374] The light-emitting device 130b includes a conductive layer 142b and a conductive layer 149b on the conductive layer 142b. The conductive layers 142b and 149b may all be referred to as pixel electrodes, or only one of them may be referred to as a pixel electrode.

[0375] Light emitting device 130c includes conductive layer 142c and conductive layer 149c on conductive layer 142c.

[0376] The light-emitting device 130at includes a layer 115at and a conductive layer 149at on the layer 115at. The conductive layer 149at can be called a pixel electrode. The conductive layer 149at covers the layer 115at. The light-emitting device 130bt includes a layer 115bt and a conductive layer 149bt on the layer 115bt. The conductive layer 149bt can be called a pixel electrode. The conductive layer 149bt covers the layer 115bt.

[0377] In FIG. 8A , the conductive layer 149at covers the end of the layer 115at, and the conductive layer 149bt covers the end of the layer 115bt. The layer 113a is provided on the conductive layer 149at. The layer 113b is provided on the conductive layer 149bt. The conductive layer 149at does not need to cover the side surface of the layer 115at, as long as the conductive layer 149at is provided in a region overlapping the light-emitting region of the light-emitting device 130at. In FIG. 8A and other figures, the light-emitting region of the light-emitting device is, for example, the region where the common electrode 117 contacts the upper surface of the EL layer. The conductive layer 149at is provided so as to contact the conductive layer 222d (the conductive layer 142at in FIG. 8B ).

[0378] The light-emitting device 130bt includes a layer 115bt and a conductive layer 149bt on the layer 115bt. The conductive layer 149bt can be called a pixel electrode. The conductive layer 149bt covers the layer 115bt.

[0379] A recess is formed in the conductive layer 149bt so as to cover the opening provided in the insulating layer 214. The recess is filled with a layer 148. A layer 113b is provided over the conductive layer 149bt and the layer 148.

[0380] A protective layer 131 is provided on the light emitting devices 130b, 130c, 130at, and 130bt. An adhesive layer 122 is provided between the protective layer 131 and the substrate 120.

[0381] The display device is a top-emission type. Light emitted by the light-emitting device is emitted toward the substrate 120. The substrate 120 is preferably made of a material that is highly transparent to visible light. The pixel electrodes contain a material that reflects visible light, and the counter electrode (common electrode 117) contains a material that transmits visible light.

[0382] For example, a conductive layer functioning as a reflective electrode can be used as the conductive layers 142b and 142c, and a light-transmitting conductive layer can be used as the conductive layers 149b and 149c.

[0383] 8A , the conductive layer 142b is connected to the conductive layer 222b through an opening provided in the insulating layer 214. The conductive layer 222b is also connected to the semiconductor layer of the transistor 203 through openings provided in the insulating layers 216 and 215. For the conductive layer 142b, a material having low contact resistance with the conductive layer 222b is preferably used. The conductive layer 222b may function as a wiring. Therefore, it is preferable to use a material having low resistance for the conductive layer 222b. For example, the conductive layer 222b and the conductive layer 142b can each include one or more materials selected from a metal, a metal alloy, a metal nitride, and the like.

[0384] 8A , the conductive layer 149at is connected to the conductive layer 222d through an opening provided in the insulating layer 214. The conductive layer 222d is connected to the semiconductor layer of the transistor 204 through openings provided in the insulating layers 216 and 215.

[0385] 8B , a conductive layer 142at may be provided between the conductive layer 222d and the conductive layer 149at. For example, the same material as the conductive layers 142b and 142c can be used for the conductive layer 142at. When the conductive layer 142at has a function of reflecting light, the conductive layer 142at is preferably provided in a region that does not overlap with the light-emitting region of the light-emitting device 130at. In the example shown in FIG. 8B , the conductive layer 142at is not provided on the layer 115at.

[0386] The transistor 201, the transistor 203, the transistor 204, and the transistor 205 are all formed over a substrate 110. The transistors 203 and 204 can be manufactured using the same material and the same process. The transistors 201 and 205 can be manufactured using the same material and the same process.

[0387] 8A , the transistors used as the transistors 201 and 205 have the same structure as the transistors used as the transistors 203 and 204, but different structures may be used. The driver circuits 301, 302, and 303 preferably use transistors suitable for high-speed operation. Therefore, it is preferable to use transistors suitable for high-speed operation as the transistors 201 and 205. For transistors applicable to the transistors 201, 203, 204, and 205, refer to the description in Embodiment 2. In FIG. 8A , the transistor shown in FIG. 7C is used as an example.

[0388] An insulating layer 211, an insulating layer 213, an insulating layer 216, an insulating layer 215, and an insulating layer 214 are provided over the substrate 110 in this order. A part of the insulating layer 211 functions as a gate insulating layer for each transistor. A part of the insulating layer 213 functions as a gate insulating layer for each transistor. The insulating layer 216 and the insulating layer 215 over the insulating layer 216 are provided to cover the transistor. The insulating layer 214 is provided to cover the transistor and functions as a planarization layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited to a single layer and may each be two or more layers.

[0389] At least one insulating layer covering the transistor is preferably made of a material through which impurities such as water and hydrogen do not easily diffuse. For example, the insulating layer 215 can be made of a material through which impurities such as water and hydrogen do not easily diffuse. This allows the insulating layer to function as a barrier layer. With this structure, diffusion of impurities from the outside into the transistor can be effectively suppressed, thereby improving the reliability of the display device.

[0390] It is preferable to use an inorganic insulating film for each of the insulating layers 211, 213, 215, and 216. Examples of the inorganic insulating film that can be used include a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, and an aluminum nitride film. Also usable are a hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, and a neodymium oxide film. Two or more of the above insulating films can also be stacked.

[0391] An organic insulating layer is suitable for the insulating layer 214, which functions as a planarizing layer. Materials that can be used for the organic insulating layer include acrylic resin, polyimide resin, epoxy resin, polyamide resin, polyimideamide resin, siloxane resin, benzocyclobutene-based resin, phenolic resin, and precursors of these resins. The insulating layer 214 can also have a laminated structure of an organic insulating layer and an inorganic insulating layer. The outermost layer of the insulating layer 214 preferably functions as an etching protection layer. This can prevent recesses from being formed in the insulating layer 214 during processing of a conductive layer on the insulating layer 214. Alternatively, recesses may be formed in the insulating layer 214 during processing of the conductive layer.

[0392] The transistor 203 and the transistor 204 each include a conductive layer 221 that functions as a gate, an insulating layer 211 that functions as a gate insulating layer, conductive layers 222a and 222b that function as a source and a drain, a semiconductor layer 231, an insulating layer 213 that functions as a gate insulating layer, and a conductive layer 223 that functions as a gate. Here, the same hatching pattern is applied to multiple layers obtained by processing the same conductive film. The insulating layer 211 is located between the conductive layer 221 and the semiconductor layer 231. The insulating layer 213 is located between the conductive layer 223 and the semiconductor layer 231.

[0393] The structure of the transistor included in the display device of this embodiment is not particularly limited. For example, a vertical transistor, a planar transistor, a fin transistor, a staggered transistor, an inverted staggered transistor, or the like can be used. A bottom-gate transistor structure can also be used instead of a top-gate transistor structure. Alternatively, a gate can be provided only on one side of a semiconductor layer where a channel is formed, instead of both above and below the semiconductor layer.

[0394] The transistors 203 and 204 have a structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates. The two gates are connected and the same signal is supplied to drive the transistors. Alternatively, the transistors can be driven by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other.

[0395] The semiconductor layer of the transistor preferably contains a metal oxide (also referred to as an oxide semiconductor). That is, the display device of this embodiment preferably uses an OS transistor using a metal oxide for a channel formation region. For the metal oxide that can be used for the OS transistor, the description in Embodiment 2 can be referred to.

[0396] All of the transistors included in the display device can be OS transistors, or all of the transistors included in the display device can be Si transistors, or some of the transistors included in the display device can be OS transistors and the rest can be Si transistors.

[0397] Alternatively, an OS transistor can be provided over a Si transistor, or OS transistors can be stacked.

[0398] Examples of silicon include single crystal silicon, polycrystalline silicon, and amorphous silicon. In particular, a transistor having low temperature polysilicon (LTPS) in a semiconductor layer (hereinafter also referred to as an LTPS transistor) can be used. The LTPS transistor has high field-effect mobility and favorable frequency characteristics.

[0399] By using Si transistors such as LTPS transistors, circuits that need to be driven at high frequencies (e.g., source drivers) can be built on the same substrate as the display unit, which simplifies the external circuits mounted on the display device and reduces component and mounting costs.

[0400] For example, by using both an LTPS transistor and an OS transistor in the display portion 20, a display device with low power consumption and high driving capability can be realized. A configuration in which an LTPS transistor and an OS transistor are combined is sometimes referred to as LTPO. As a more preferred example, it is preferable to use an OS transistor as a transistor that functions as a switch for controlling conduction / non-conduction between wirings, and to use an LTPS transistor as a transistor for controlling current.

[0401] For example, one of the transistors included in the display unit 20 functions as a transistor for controlling the current flowing through the light-emitting device, and can also be called a drive transistor. One of the source and drain of the drive transistor is connected to the pixel electrode of the light-emitting device. It is preferable to use an LTPS transistor as the drive transistor. This allows the current flowing through the light-emitting device in the pixel circuit to be increased.

[0402] On the other hand, another transistor included in the display unit 20 functions as a switch for controlling pixel selection / non-selection and can also be called a selection transistor. The gate of the selection transistor is connected to a gate line, and one of the source and drain is connected to a source line (signal line). It is preferable to use an OS transistor as the selection transistor. This allows the gradation of pixels to be maintained even when the frame frequency is significantly low (for example, 1 fps or less), and therefore power consumption can be reduced by stopping the driver when displaying a still image.

[0403] As described above, the display device of one embodiment of the present invention can have a high aperture ratio, high definition, high display quality, and low power consumption.

[0404] A display device according to one embodiment of the present invention includes an OS transistor and a light-emitting device with a metal maskless (MML) structure. This structure significantly reduces leakage current that may flow through the transistor and leakage current that may flow between adjacent light-emitting devices (also referred to as lateral leakage current or side leakage current). Furthermore, when an image is displayed on the display device, the viewer can observe one or more of image clarity, image sharpness, high saturation, and a high contrast ratio. The extremely low leakage current that may flow through the transistor and lateral leakage current between the light-emitting devices significantly reduces light leakage during black display (so-called floating black).

[0405] A connection portion 230 is provided in a region of the substrate 110 where the substrate 120 does not overlap. In the connection portion 230, the wiring 165 is connected to the FPC 119 via a conductive layer 166 and a connection layer 242. The conductive layer 166 has an example of a stacked structure including a conductive film obtained by processing the same conductive film as the conductive layer 142b, a conductive film obtained by processing the same conductive film as the conductive layer 146b, and a conductive film obtained by processing the same conductive film as the conductive layer 149b. The conductive layer 166 is exposed on the top surface of the connection portion 230. This allows the connection portion 230 and the FPC 119 to be connected via the connection layer 242.

[0406] The connection layer 242 may be an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like.

[0407] For example, an SOI substrate, a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, or an organic resin substrate can be used for the substrate 110 and the substrate 120. Furthermore, any of these substrates on which semiconductor elements are provided can also be used as the substrate.

[0408] Furthermore, flexible substrates can be used as the substrate 110 and the substrate 120. By providing a peeling layer between the substrate and a layer on which a transistor is provided, after a semiconductor device is partially or entirely completed on the peeling layer, the semiconductor device can be separated from the substrate and transferred to another substrate. In this case, the transistors and the like can also be transferred to a substrate with poor heat resistance or a flexible substrate. Note that a semiconductor substrate on which an arithmetic circuit, a memory circuit, and the like are formed can also be used as the substrate 110. Furthermore, various optical members such as a circular polarizer can be arranged on the outside of the substrate 120.

[0409] 9, an insulating layer 126 is provided to cover edge portions of the conductive layers 149c, 149at, and the like that function as pixel electrodes. The insulating layer 125, the insulating layer 127, and the mask layer 118 are not provided. The layer 113a, the layer 113b, and the layer 113c are provided over the pixel electrode and the insulating layer 126, respectively. The layer 113a, the layer 113b, and the layer 113c are provided in contact with, for example, the top surface of the insulating layer 126 and a portion of the top surface of the pixel electrode that is not covered with the insulating layer 126, respectively.

[0410] By using an organic resin for the insulating layer 126, the surface can be made gently curved, which can improve the coverage of a film formed on the insulating layer 126.

[0411] 9, for example, the layers 113a, 113b, and 113c can be formed using a shadow mask such as a metal mask. Forming the layers 113a, 113b, and 113c without using lithography can sometimes reduce the cost required for manufacturing a display device.

[0412] <Configuration example 3 of display device> As shown in FIG. 10 , by providing a conductive layer 146b and a conductive layer 146c over the layer 148 and using a conductive layer that functions as a reflective electrode for the conductive layer 146b and the conductive layer 146c, regions that overlap with the recesses of the conductive layer 142b and the conductive layer 142c can also be used as light-emitting regions, and the aperture ratio of the pixel can be increased.

[0413] The conductive layer 146b is provided over the conductive layer 142b, and a conductive layer 149b is provided over the conductive layer 146b. The conductive layer 146c is provided over the conductive layer 142c, and a conductive layer 149c is provided over the conductive layer 146c. The conductive layer 146at is provided over the conductive layer 142at, and a conductive layer 149at is provided over the conductive layer 146at.

[0414] Recesses are formed in the conductive layers 142b, 142c, and 142at so as to cover the openings provided in the insulating layer 214. The recesses are filled with a layer 148. The layer 148 has a function of planarizing the recesses of the conductive layers 142b, 142c, and 142at.

[0415] The layer 148 is not limited to an insulating layer, and a conductive layer can also be used. Various inorganic insulating materials, organic insulating materials, and conductive materials can be used as appropriate for the layer 148. In particular, the layer 148 is preferably formed using an insulating material, and more preferably formed using an organic insulating material.

[0416] 10 , in the light-emitting devices 130b and 130c, the area above the layer 148 is also used as a light-emitting region, and therefore the area of ​​the light-emitting region per subpixel is larger than that of the light-emitting device 130at. This can also be expressed as a high aperture ratio. When the configuration shown in FIG. 10 is applied, the aperture ratio of the light-emitting device included in the pixel 11 may be lower than that of the light-emitting device included in the pixel 10. When the aperture ratio is lower, the luminance per area of ​​the pixel 11 can be increased to match the luminance of the light emitted from the pixel 10.

[0417] When the conductive layer 146at is formed using the same process as the conductive layers 146b and 146c, the same material as the conductive layers 146b and 146c can be used for the conductive layer 146at. When conductive layers functioning as reflective electrodes are used for the conductive layers 146b and 146c, a conductive layer functioning as a reflective electrode may also be used for the conductive layer 146at.

[0418] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0419] Embodiment 4 In this embodiment, an electronic device and a mobile object according to one embodiment of the present invention will be described.

[0420] An electronic device or a mobile object according to one embodiment of the present invention includes a display device according to one embodiment of the present invention and a camera in a housing. The camera can be used as a front camera and is an under-display camera that is provided so as to overlap with a display portion of the display device.

[0421] The display device of one embodiment of the present invention preferably has an extremely high resolution, such as HD (1280 × 720 pixels), FHD (1920 × 1080 pixels), WQHD (2560 × 1440 pixels), WQXGA (2560 × 1600 pixels), 4K (3840 × 2160 pixels), or 8K (7680 × 4320 pixels). A resolution of 4K, 8K, or higher is particularly preferable. Furthermore, the display device of one embodiment of the present invention is not particularly limited in terms of screen ratio (aspect ratio). For example, the display device can support various screen ratios, such as 1:1 (square), 4:3, 16:9, and 16:10.

[0422] In addition, the electronic device and mobile object of this embodiment may also have a sensor (including the function of sensing, detecting, or measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays).

[0423] The electronic device and mobile object according to the present embodiment may have various functions, such as a function to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date, time, etc., a function to execute various software (programs), a wireless communication function, a function to read out programs or data recorded on a recording medium, etc.

[0424] <Electronic Device> An electronic device according to one embodiment of the present invention is a device used as a portable information terminal such as a smartphone or a tablet computer.

[0425] The electronic device 6500 shown in FIG. 11A is a portable information terminal device that can be used as a smartphone.

[0426] The electronic device 6500 includes a housing 6501, a display portion 6502, a power button 6503, a button 6504, a speaker 6505, a microphone 6506, a camera 6507, and the like. The display portion 6502 has a touch panel function.

[0427] The camera 6507 can be used as a front camera and is provided so as to overlap with the display portion 6502. The display device of one embodiment of the present invention can be applied to the display portion 6502. In the display device of one embodiment of the present invention, the entire display portion can have the same resolution, and an initial image can be acquired by the camera 6507 by utilizing a light-transmitting region provided in the display portion 6502.

[0428] In addition, the display device of one embodiment of the present invention can have a high pixel aperture ratio, and thus has high light extraction efficiency and can display a very bright image. Furthermore, the entire display portion 6502 has the same resolution, making it difficult to visually recognize the position of the camera 6507, and therefore, can display a natural image.

[0429] FIG. 11B is a schematic cross-sectional view including the end of the housing 6501 on the camera 6507 side.

[0430] A light-transmitting protective member 6510 is provided on the display surface side of the housing 6501, and a display panel 6511, optical members 6512, a touch panel 6513, a battery 6518, a camera 6507, etc. are arranged in the space surrounded by the housing 6501 and the protective member 6510.

[0431] A display panel 6511, an optical member 6512, and a touch panel 6513 are fixed to the protective member 6510 by adhesive layers (not shown).

[0432] The lens of the camera 6507 is arranged so as to overlap a region 6511T with high transmittance of the display panel 6511. The camera 6507 can be mounted on a printed circuit board 6517 fixed to the housing 6501. An IC 6516 having a computing device or the like can also be mounted on the printed circuit board 6517. The region 6511T corresponds to the display portion b shown in FIG. 1A.

[0433] The initial image captured by the camera 6507 is a low-quality image in which information is lost due to pixel occlusion. The arithmetic device included in the IC 6516 can perform image processing such as restoration of missing parts of the image by inference and noise removal, thereby generating a high-quality image. Note that the display device of one embodiment of the present invention captures an image using a light-transmitting region provided in a pixel and improves the quality of the initial image, thereby enabling a high-quality image to be obtained by image processing. Note that the image processing can also use artificial intelligence trained by deep learning or the like.

[0434] 11C is a perspective view showing an example of a camera module in which an image sensor chip and a lens are combined. The camera module can be used for the camera 6507.

[0435] The package containing the image sensor chip is a CSP (Chip Size Package), which includes an image sensor bare chip 450, a cover glass 440, and an adhesive 430 for bonding the two together.

[0436] Electrode pads 425 provided on the outside of the pixel array 455 are connected to the rear surface electrodes 415 via through electrodes. The electrode pads 425 are electrically connected to the circuits that make up the image sensor by wiring or wires. The bare chip 450 can also be a laminated chip in which circuits having various functions are laminated.

[0437] The back surface electrode 415 is exemplified by a BGA (Ball Grid Array) having a structure in which bumps are formed using solder balls. The back surface electrode 415 is not limited to a BGA, and may be an LGA (Land Grid Array) or a PGA (Pin Grid Array). Alternatively, a package in which the bare chip 450 is mounted on a QFN (Quad Flat No-Lead Package) or a QFP (Quad Flat Package) may be used.

[0438] A lens cover 460, a plurality of lenses 470, and the like are provided on the package. Furthermore, an optical filter 480 that absorbs light of a specific wavelength is provided between the lens 470 and the cover glass 440 as needed. For example, in the case of an image sensor that mainly captures visible light, an infrared cut filter or the like can be used as the optical filter 480.

[0439] 12A is a perspective view of a foldable portable information terminal 9201. The portable information terminal 9201 includes a housing 9000a, a housing 9000b, a display portion 9001, and an operation button 9056.

[0440] The housing 9000a and the housing 9000b are joined by a hinge 9055, and the hinge 9055 allows the device to be folded in half.

[0441] A display portion 9001 included in the portable information terminal 9201 is supported by two housings (a housing 9000 a and a housing 9000 b ) connected by a hinge 9055 .

[0442] 12B to 12D are perspective views showing a foldable portable information terminal 9202. Fig. 12B shows the portable information terminal 9202 in an unfolded state, Fig. 12D shows it in a folded state, and Fig. 12C is a perspective view showing a state in which the portable information terminal 9202 is in the process of changing from one of Fig. 12B and Fig. 12D to the other. In this way, the portable information terminal 9202 can be folded into three.

[0443] A display portion 9001 of the portable information terminal 9202 is supported by three housings 9000 connected by hinges 9055 .

[0444] 12B to 12D, the display device of one embodiment of the present invention can be applied to the display portion 9001. For example, the display portion 9001 can be bent with a curvature radius of 0.1 mm to 150 mm.

[0445] The portable information terminals 9201 and 9202 are each highly portable when folded, and have a seamless, wide display area when unfolded, allowing for excellent display visibility.

[0446] 12E is a perspective view showing a wristwatch-type mobile information terminal 9200. The mobile information terminal 9200 can be used as, for example, a smart watch (registered trademark). The display surface of the display unit 9001 is curved, and display can be performed along the curved display surface. The mobile information terminal 9200 can also perform hands-free calling by communicating with, for example, a headset capable of wireless communication. The mobile information terminal 9200 can also perform data transmission and charging with another information terminal through a connection terminal 9006. Note that charging may be performed by wireless power supply.

[0447] The mobile information terminal 9200 shown in Figure 12E has a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), a connection terminal 9006, a sensor 9007 (including the function of detecting, detecting, or measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), a microphone 9008, etc.

[0448] <Mobile Body> The semiconductor device and the display device according to one embodiment of the present invention can be applied to the area around the driver's seat of an automobile, which is a mobile body.

[0449] Fig. 12F is a diagram illustrating the area around the windshield in the interior of a vehicle, showing display panels 9001a, 9001b, and 9001c attached to the dashboard, and display panel 9001d attached to a pillar.

[0450] The display panels 9001a to 9001c can provide various information by displaying navigation information, a speedometer, a tachometer, mileage, a fuel gauge, gear status, air conditioning settings, etc. Furthermore, the display items and layouts displayed on the display panels can be changed as appropriate to suit the user's preferences, thereby improving the design. The display panels 9001a to 9001c can also be used as lighting devices.

[0451] The display panel 9001d can display an image from an imaging device installed on the vehicle body to complement the view blocked by the pillar (blind spot). In other words, by displaying an image from an imaging device installed on the outside of the vehicle, blind spots can be complemented and safety can be improved. Furthermore, by displaying an image that complements the invisible part, safety confirmation can be performed more naturally and without discomfort. The display panel 9001d can also be used as a lighting device.

[0452] The display device of one embodiment of the present invention can be applied to the display panels 9001a to 9001d. A camera can be provided so as to overlap with a display portion of the display device. The camera is an under-display camera that can be used as a front camera.

[0453] The light emitted from the light-emitting element provided on the display panel can be used as the light source for the camera. Alternatively, the light source for the camera can be provided separately. Furthermore, the light from the display panel and a separately provided light source can be used in combination.

[0454] The camera can be used to take a picture of the driver. By analyzing the captured image, the driver's condition can be inferred. The mobile unit can issue instructions to the driver according to the driver's condition. For example, the system can analyze the driver's line of sight, facial expression, etc., and then display the content on the display panel or emit a voice from the mobile unit.

[0455] A mobile object according to one embodiment of the present invention can display a message to a driver using one or more of the display panels 9001a to 9001d. A voice message can also be output using a speaker provided in the mobile object. Furthermore, the display contents of the display panels 9001a to 9001d can be changed as appropriate to match the driver's line of sight.

[0456] In the mobile object of one embodiment of the present invention, the camera can be placed so as to overlap with the display device, and the camera does not stand out on the display panel, which improves the design. In addition, the camera can be placed at any position without changing the area of ​​the display panel.

[0457] Furthermore, by using infrared light as the camera's light source, it is possible to take pictures even in dark environments such as at night without turning on the interior lights, thereby enabling pictures to be taken without compromising driving safety.

[0458] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0459] AL: wiring, B: subpixel, CL: wiring, G: subpixel, GL: gate line, I: subpixel, IR: infrared light, R: subpixel, RL: wiring, SL: source line, 10: pixel, 10a: pixel, 10b: pixel, 11: pixel, 20: display unit, 30: camera, 30a: camera, 30b: camera, 31: lens, 41: substrate, 42: substrate, 101: layer, 110: substrate, 111a: pixel electrode, 111at: pixel electrode, 111b: pixel electrode, 111bt: pixel electrode, 111c: pixel electrode, 111ct: pixel electrode, 111dt: pixel electrode, 113a: layer, 113at: layer, 113b: layer, 1 13bt: layer, 113c: layer, 113ct: layer, 113dt: layer, 114: common layer, 115at: layer, 115bt: layer, 115ct: layer, 115dt: layer, 117: common electrode, 118a: mask layer, 118at: mask layer, 118b: mask layer, 118bt: mask layer, 118c: mask layer, 118ct: mask layer, 119: FPC, 120: substrate, 122: adhesive layer, 125: insulating layer, 126: insulating layer, 127: insulating layer, 130a: light-emitting device, 130at: light-emitting device, 130b: light-emitting device, 130bt: light-emitting device, 130c: light-emitting device , 130ct: light-emitting device, 130dt: light-emitting device, 131: protective layer, 142at: conductive layer, 142b: conductive layer, 142c: conductive layer, 146at: conductive layer, 146b: conductive layer, 146c: conductive layer, 148: layer, 149at: conductive layer, 149b: conductive layer, 149bt: conductive layer, 149c: conductive layer, 165: wiring, 166: conductive layer, 200C: transistor, 200D: transistor, 201: transistor, 203: transistor, 204: transistor, 205: transistor, 211: insulating layer, 213: insulating layer, 214: insulating layer, 215: insulating layer, 216: insulating layer, 218: insulating layer, 221: conductive layer, 222a: conductive layer, 222b: conductive layer, 222d: conductive layer, 223: conductive layer, 225: insulating layer, 230: connection portion, 231: semiconductor layer, 231i: channel formation region, 231n: low resistance region, 242: connection layer, 251: conductive layer, 255a: insulating layer, 255b: insulating layer, 255c: insulating layer, 256: insulating layer, 257: insulating layer, 258: insulating layer, 259: insulating layer, 261: conductive layer, 262: opening, 263: semiconductor layer, 264: insulating layer, 265: conductive layer, 266: insulating layer, 301: driving circuit, 302: driving circuit,303: driving circuit, 401: substrate, 402: insulating layer, 415: rear electrode, 425: electrode pad, 430: adhesive, 440: cover glass, 450: bare chip, 455: pixel array, 460: lens cover, 470: lens, 480: optical filter, 501: substrate, 502: insulating layer, 505: conductive layer, 514: insulating layer, 516: insulating layer, 520: semiconductor Conductive layer, 522: insulating layer, 524: insulating layer, 541: insulating layer, 542a: conductive layer, 542b: conductive layer, 545: conductive layer, 550: insulating layer, 554: insulating layer, 560: conductive layer, 560a: conductive layer, 560b: conductive layer, 574: insulating layer, 580: insulating layer, 581: insulating layer, 6500: electronic device, 6501: housing, 6502: display unit, 6503: power button , 6504: Button, 6505: Speaker, 6506: Microphone, 6507: Camera, 6510: Protective member, 6511: Display panel, 6511T: Area, 6512: Optical member, 6513: Touch panel, 6516: IC, 6517: Printed circuit board, 6518: Battery, 9000: Housing, 9000a: Housing, 9000b: Housing, 9001: Display unit, 9001a: display panel, 9001b: display panel, 9001c: display panel, 9001d: display panel, 9003: speaker, 9005: operation keys, 9006: connection terminal, 9007: sensor, 9008: microphone, 9055: hinge, 9056: operation button, 9200: mobile information terminal, 9201: mobile information terminal, 9202: mobile information terminal,

Claims

having pixels, The pixel has a first sub-pixel that displays a first color and a second sub-pixel that displays a second color; the second color is different from the first color, the first subpixel includes a first dielectric multilayer film, a first electrode on the first dielectric multilayer film, a first EL layer on the first electrode, and a common electrode on the first EL layer; the second subpixel has a second electrode, a second EL layer on the second electrode, and the common electrode on the second EL layer; The display device, wherein the first subpixel has a function of transmitting light containing the second color. 　 In claim 1, the second subpixel has a second dielectric multilayer film; the second electrode is located on the second dielectric multilayer film; The second subpixel has a function of transmitting light containing the first color. 　 In claim 1, the pixel has a third sub-pixel that displays a third color; the third color is different from each of the first color and the second color, The display device, wherein the first subpixel has a function of transmitting light containing the third color. 　 In claim 1, the pixel has a third sub-pixel that displays a third color; the third color is different from each of the first color and the second color, the second subpixel has a second dielectric multilayer film; the second electrode is located on the second dielectric multilayer film; The second subpixel has a function of transmitting light containing one or more of the first color and the third color. 　 In claim 4, the first color is one selected from red, green, and blue; the second color is selected from red, green, and blue; The display device, wherein the third color is selected from red, green, and blue. 　 In claim 1, The display device, wherein the first electrode and the second electrode are each a conductive layer having a function of transmitting visible light. 　 In claim 1, the pixel has a third sub-pixel that emits infrared light; the second subpixel has a second dielectric multilayer film; the second electrode is located on the second dielectric multilayer film; The display device, wherein one or more of the first subpixel and the second subpixel have a function of transmitting infrared light. 　 In claim 1, the first dielectric multilayer film has a first layer, a second layer on the first layer, a third layer on the second layer, and a fourth layer on the third layer; the first layer and the third layer comprise a first material; the second layer and the fourth layer have a second material different from the first material; A display device, wherein the first layer and the third layer have a refractive index higher than that of the second layer and the fourth layer. 　 In claim 8, The display device, wherein the first material comprises one or more selected from titanium oxide, aluminum oxide, zirconium oxide, hafnium oxide, tantalum oxide, and silicon nitride. In claim 8, The display device, wherein the second material comprises one or more selected from silicon oxide, magnesium fluoride, lithium fluoride, sodium fluoride, calcium fluoride, aluminum fluoride, strontium fluoride, and fluorides containing sodium and aluminum. 　 In claim 1, A display device, wherein the thickness of the first dielectric multilayer film is 100 nm or more and 3000 nm or less. 　 In claim 1, A display device, wherein each of the first subpixel and the second subpixel includes a transistor having a metal oxide in a semiconductor layer. 　 A first display unit and a second display unit are included, the second display unit is surrounded by the first display unit, the first display unit has a first pixel, the second display unit has second pixels, the first pixel has a first sub-pixel that displays a first color and a second sub-pixel that displays a second color; the second color is different from the first color, the second pixel has a third sub-pixel that displays the first color and a fourth sub-pixel that displays the second color; the third subpixel has a function of transmitting light including the second color; the first subpixel has a first electrode, a first EL layer on the first electrode, and a common electrode on the first EL layer; the second subpixel has a second electrode, a second EL layer on the second electrode, and the common electrode on the second EL layer; the first electrode and the second electrode have a function of reflecting visible light, the third subpixel includes a first dielectric multilayer film, a third electrode on the first dielectric multilayer film, a third EL layer on the third electrode, and the common electrode on the third EL layer; a fourth subpixel including a fourth electrode, a fourth EL layer on the fourth electrode, and the common electrode on the fourth EL layer; 　 In claim 13, The display device, wherein the third electrode and the fourth electrode are each a conductive layer having a function of transmitting visible light. 　 In claim 13, A display device in which each of the first to fourth subpixels includes a transistor having a metal oxide in a semiconductor layer. 　 A display device comprising: the display device according to claim 13; and a camera; a region where the second display unit and the camera lens overlap; The camera has a function of capturing an image using light that passes through the third sub-pixel. 　 A display device and a camera are included. the display device has a first display unit and a second display unit, the second display unit is surrounded by the first display unit, the first display unit has a first pixel, the second display unit has second pixels, the first pixel has a first sub-pixel that displays a first color, a second sub-pixel that displays a second color, and a third sub-pixel that displays a third color; the second color is different from the first color, the third color is different from the first color and the second color, the second pixel has a fourth sub-pixel that displays the first color, a fifth sub-pixel that displays the second color, and a sixth sub-pixel that displays the third color; the fourth subpixel has a function of transmitting light containing one or more of the second color and the third color; the fifth subpixel has a function of transmitting light containing one or more of the first color and the third color; the sixth subpixel has a function of transmitting light containing one or more of the first color and the second color; the camera has a function of capturing an image using light transmitted through the fourth sub-pixel, light transmitted through the fifth sub-pixel, and light transmitted through the sixth sub-pixel. 　 A display device and a camera are included. the display device has a first display unit and a second display unit, the second display unit is surrounded by the first display unit, the first display unit has a first pixel, the second display unit has second pixels, the first pixel has a first sub-pixel that displays a first color and a second sub-pixel that displays a second color; the second color is different from the first color, the second pixel has a third sub-pixel that displays the first color, a fourth sub-pixel that displays the second color, and a fifth sub-pixel that emits infrared light; one or more of the third subpixel and the fourth subpixel have a function of transmitting infrared light; The camera has a function of capturing an image using infrared light that passes through one or more of the third sub-pixel and the fourth sub-pixel.

Images