Display device

Abstract

To provide a high-definition display device, and a display device with high display quality.SOLUTION: The display device includes a substrate, an insulator layer, a plurality of transistors, and a plurality of light-emitting diodes. The plurality of light-emitting diodes is provided on the substrate in matrix. Each of the plurality of transistors is electrically connected to at least one of the plurality of light-emitting diodes. The plurality of light-emitting diodes is positioned closer to the substrate side than the plurality of transistors. The plurality of light-emitting diodes emits light to the substrate side. Each of the plurality of transistors has a metal oxide layer and a gate electrode. The metal oxide layer includes a channel formation region. Height of a top face of the gate electrode is substantially equal to height of a top face of the insulator layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to a display device, a display module, an electronic device, and methods for manufacturing these.

[0002] Note that one aspect of the present invention is not limited to the above technical field. Examples of the technical field of one aspect of the present invention include semiconductor devices, display devices, light-emitting devices, power storage devices, storage devices, electronic devices, lighting devices, input devices (e.g., touch sensors, etc.), input / output devices (e.g., touch panels, etc.), their driving methods, or their manufacturing methods.

Background Art

[0003] In recent years, display devices using micro light-emitting diodes (micro LEDs (Light Emitting Diodes)) as display elements have been proposed (e.g., Patent Document 1). Display devices using micro LEDs as display elements have advantages such as high brightness, high contrast, and long life, and research and development are active as next-generation display devices.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a display device using micro LEDs as display elements, the time required for mounting LED chips is extremely long, and reducing the manufacturing cost is an issue. For example, in the pick-and-place method, red (R), green (G), and blue (B) LEDs are fabricated on different wafers, and each LED is cut out and mounted on a circuit board one by one. Therefore, the larger the number of pixels in the display device, the greater the number of LEDs to be mounted, and the longer the time required for mounting. Also, the higher the fineness of the display device, the higher the difficulty of mounting the LEDs.

[0006] One aspect of the present invention aims to provide a display device with high fineness. One aspect of the present invention aims to provide a display device with high display quality. One aspect of the present invention aims to provide a display device with low power consumption. One aspect of the present invention aims to provide a display device with high reliability.

[0007] One aspect of the present invention aims to reduce the manufacturing cost of a display device using micro LEDs as display elements. One aspect of the present invention aims to manufacture a display device using micro LEDs as display elements with a high yield.

[0008] Note that the description of these problems does not prevent the existence of other problems. One aspect of the present invention does not necessarily need to solve all of these problems. It is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0009] The display device according to one aspect of the present invention includes a substrate, an insulating layer, a plurality of transistors, and a plurality of light-emitting diodes. The plurality of light-emitting diodes are provided in a matrix on the substrate. Each of the plurality of transistors is electrically connected to at least one of the plurality of light-emitting diodes. The plurality of light-emitting diodes are located closer to the substrate side than the plurality of transistors. The plurality of light-emitting diodes emit light toward the substrate side. Each of the plurality of transistors has a metal oxide layer and a gate electrode. The metal oxide layer has a channel formation region. The height of the upper surface of the gate electrode is substantially the same as the height of the upper surface of the insulating layer.

[0010] Alternatively, the display device according to one aspect of the present invention includes a substrate, an insulating layer, a plurality of transistors, and a plurality of light-emitting diodes. The plurality of light-emitting diodes are provided in a matrix on the substrate. Each of the plurality of transistors is electrically connected to at least one of the plurality of light-emitting diodes. The plurality of light-emitting diodes are located closer to the substrate side than the plurality of transistors. The plurality of light-emitting diodes emit light toward the substrate side. Each of the plurality of transistors has a metal oxide layer, a gate insulating layer, a gate electrode, a first conductive layer, and a second conductive layer. The metal oxide layer has a channel formation region. The metal oxide layer has a first region overlapping with the first conductive layer, a second region overlapping with the second conductive layer, and a third region between the first region and the second region. The first conductive layer and the second conductive layer are spaced apart from each other on the metal oxide layer. The insulating layer is located on the first conductive layer and the second conductive layer. The insulating layer has an opening overlapping with the third region. The gate insulating layer is located inside the opening and overlaps with the side surface of the insulating layer and the upper surface of the third region. The gate electrode is located inside the opening and overlaps with the side surface of the insulating layer and the upper surface of the third region through the gate insulating layer.

[0011] At least one of the plurality of light-emitting diodes is preferably a micro light-emitting diode.

[0012] The plurality of light-emitting diodes may include a first light-emitting diode and a second light-emitting diode that exhibit lights of different colors. At this time, a first transistor electrically connected to the first light-emitting diode and a second transistor electrically connected to the second light-emitting diode may have a structure in which one or both of the channel length and the channel width are different from each other.

[0013] Alternatively, the plurality of light-emitting diodes may all exhibit lights of the same color.

[0014] The display device according to one aspect of the present invention preferably further includes a driving circuit. The driving circuit includes a plurality of circuit transistors. Each of the plurality of circuit transistors has a channel formation region on a semiconductor substrate. The insulating layer, the plurality of transistors, and the plurality of light-emitting diodes are each located between the substrate and the semiconductor substrate. The plurality of transistors are located closer to the substrate side than the plurality of circuit transistors.

[0015] The display device according to one aspect of the present invention preferably further includes a functional layer. The functional layer is located between the substrate and at least one of the plurality of light-emitting diodes. At least one of the plurality of light-emitting diodes emits light toward the substrate side through the functional layer. The functional layer includes one or both of a coloring layer and a color conversion layer.

[0016] The display device according to one aspect of the present invention preferably further includes a touch sensor. The light-emitting diode emits light toward the touch sensor side through the substrate.

[0017] One aspect of the present invention is a module having the display device configured as described above, a module to which a connector such as a flexible printed circuit (hereinafter referred to as FPC) or a TCP (Tape Carrier Package) is attached, or a module in which an integrated circuit (IC) is mounted by a method such as a COG (Chip On Glass) method or a COF (Chip On Film) method.

[0018] One aspect of the present invention is an electronic device having the above-described module and at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button.

[0019] One aspect of the present invention is a method for manufacturing a display device, including forming a plurality of transistors in a matrix on a first substrate, forming a plurality of light-emitting diodes in a matrix on a second substrate, forming a first conductor on the first substrate or the second substrate to electrically connect at least one of the plurality of transistors or at least one of the plurality of light-emitting diodes, bonding the first substrate and the second substrate so that at least one of the plurality of transistors and at least one of the plurality of light-emitting diodes are electrically connected via the first conductor, and using at least one planarization process in the step of forming the plurality of transistors. It is preferable that at least one of the plurality of light-emitting diodes is a micro light-emitting diode. It is preferable that at least one of the plurality of transistors has a metal oxide in a channel formation region.

[0020] In the method for manufacturing a display device according to one aspect of the present invention, by forming the first conductor on the first substrate, the first conductor and at least one of the plurality of transistors are electrically connected, a second conductor that is electrically connected to at least one of the plurality of light-emitting diodes is formed on the second substrate, and the first substrate and the second substrate may be bonded so that the first conductor and the second conductor are in contact with each other.

[0021] In the method for manufacturing a display device according to one aspect of the present invention, at least one of a coloring layer, a color conversion layer, and a touch sensor is formed on a third substrate, after bonding the first substrate and the second substrate, the second substrate is peeled off, and the third substrate may be bonded to the surface exposed by peeling off the second substrate.

[0022] Alternatively, in the method for manufacturing a display device according to one aspect of the present invention, at least one of a coloring layer, a color conversion layer, and a touch sensor is formed on a third substrate, and after bonding the first substrate and the second substrate, the second substrate is polished to reduce the thickness of the second substrate, and the third substrate may be bonded to the polished surface of the second substrate.

Advantages of the Invention

[0023] According to one aspect of the present invention, a display device with high definition can be provided. According to one aspect of the present invention, a display device with high display quality can be provided. According to one aspect of the present invention, a display device with low power consumption can be provided. According to one aspect of the present invention, a highly reliable display device can be provided.

[0024] According to one aspect of the present invention, the manufacturing cost of a display device using micro LEDs as display elements can be reduced. According to one aspect of the present invention, a display device using micro LEDs as display elements can be manufactured with a high yield.

[0025] Note that the description of these effects does not preclude the existence of other effects. One aspect of the present invention does not necessarily have to have all of these effects. It is possible to extract other effects from the descriptions in the specification, drawings, and claims.

Brief Description of the Drawings

[0026]

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[0027] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art can easily understand that the form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below.

[0028] In the configuration of the invention described below, the same reference numerals are commonly used for the same parts or parts having the same function among different drawings, and the repeated description thereof will be omitted. In addition, when referring to the same function, the hatch pattern may be the same, and there may be cases where no particular reference numeral is given.

[0029] In addition, the positions, sizes, ranges, etc. of the respective components shown in the drawings may not represent the actual positions, sizes, ranges, etc. for the sake of simplicity of understanding. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, ranges, etc. disclosed in the drawings.

[0030] Note that the terms "film" and "layer" can be interchanged with each other depending on the case or according to the situation. 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".

[0031] (Embodiment 1) In this embodiment, a display device according to one aspect of the present invention will be described with reference to FIGS. 1 to 9.

[0032] [Outline of the display device] The display device of this embodiment includes a plurality of light-emitting diodes as display elements and a plurality of transistors for driving the display elements. The plurality of light-emitting diodes are provided in a matrix on a substrate having transparency to visible light. Each of the plurality of transistors is electrically connected to at least one of the plurality of light-emitting diodes. The plurality of light-emitting diodes are located closer to the substrate side than the plurality of transistors. The plurality of light-emitting diodes emit light toward the substrate side.

[0033] The display device of this embodiment is formed by bonding a plurality of transistors and a plurality of light-emitting diodes formed on different substrates to each other.

[0034] In the manufacturing method of the display device of this embodiment, since a plurality of light-emitting diodes and a plurality of transistors are bonded together at once, even when manufacturing a display device with a large number of pixels or a high-definition display device, compared with the method of mounting light-emitting diodes one by one on a circuit board, the manufacturing time of the display device can be shortened, and the manufacturing difficulty can be reduced.

[0035] The display device according to this embodiment has a function of displaying images using light-emitting diodes. Since a light-emitting diode is a self-luminous element, when a light-emitting diode is used as a display element, a backlight is not required for the display device, and a polarizing plate may not be provided. Therefore, the power consumption of the display device can be reduced, and the display device can be made thinner and lighter. In addition, a display device using a light-emitting diode as a display element can obtain high display quality because it has high contrast and a wide viewing angle. Also, by using an inorganic material as a light-emitting material, the lifespan of the display device can be extended and the reliability can be enhanced.

[0036] In this embodiment, in particular, an example in the case of using a micro LED as a light-emitting diode will be described. In this embodiment, a micro LED having a double heterojunction will be described. However, the light-emitting diode is not particularly limited, and for example, a micro LED having a quantum well junction, an LED using a nanocolumn, etc. may be used.

[0037] The area of the region that emits light from the light-emitting diode is preferably 1 mm 2 or less, more preferably 10000 μm 2 or less, even more preferably 3000 μm 2 or less, even more preferably 700 μm 2 or less. In this specification etc., a light-emitting diode with an area of the light-emitting region of 10000 μm 2 or less may sometimes be referred to as a micro LED.

[0038] The transistor included in the display device preferably has a metal oxide in the channel formation region. A transistor using a metal oxide can reduce power consumption. Therefore, by combining it with a micro LED, a display device with extremely low power consumption can be realized.

[0039] In particular, it is preferable that the display device according to this embodiment has a transistor in which the height of the upper surface of the gate electrode substantially coincides with the height of the upper surface of the insulating layer. For example, by performing a planarization process using a method such as CMP (Chemical Mechanical Polishing), the upper surface of the gate electrode and the upper surface of the insulating layer can be planarized, and the height of the upper surface of the gate electrode and the height of the upper surface of the insulating layer can be made uniform.

[0040] For a transistor having such a configuration, it is easy to reduce the size. By reducing the size of the transistor, the size of the pixel can be reduced, so that the fineness of the display device can be increased.

[0041] Since the display device according to this embodiment can increase the fineness, it can be suitably used for an electronic device having a relatively small display unit. Examples of such electronic devices include wristwatch-type or bracelet-type information terminals (wearable devices), VR (Virtual Reality)-oriented devices such as head-mounted displays, AR (Augmented Reality)-oriented devices in the form of glasses, or MR (Mixed Reality)-oriented devices, and other wearable devices that can be worn on the head.

[0042] [Configuration Example 1 of Display Device] FIG. 1 shows a cross-sectional view of a display device 100A. FIG. 2 shows a cross-sectional view of a manufacturing method of the display device 100A.

[0043] The display device 100A shown in FIG. 1 is configured by bonding an LED substrate 150A shown in FIG. 2(A) and a circuit substrate 150B shown in FIG. 2(B) (see FIG. 2(C)).

[0044] FIG. 2(A) shows a cross-sectional view of the LED substrate 150A.

[0045] The LED substrate 150A has a substrate 101, light-emitting diodes 110a, light-emitting diodes 110b, and a protective layer 102.

[0046] The light-emitting diode 110a has an electrode 112a, a semiconductor layer 113a, a light-emitting layer 114a, a semiconductor layer 115a, and an electrode 116a. The light-emitting diode 110b has an electrode 112b, a semiconductor layer 113b, a light-emitting layer 114b, a semiconductor layer 115b, and an electrode 116b.

[0047] The electrode 112a is electrically connected to the semiconductor layer 113a. The electrode 116a is electrically connected to the semiconductor layer 115a. The electrode 112b is electrically connected to the semiconductor layer 113b. The electrode 116b is electrically connected to the semiconductor layer 115b. The protective layer 102 is provided so as to cover the substrate 101, the semiconductor layers 113a and 113b, the light-emitting layers 114a and 114b, and the semiconductor layers 115a and 115b. The protective layer 102 covers the side surfaces of the electrodes 112a and 112b and the side surfaces of the electrodes 116a and 116b, and has openings that overlap the upper surfaces of the electrodes 112a and 112b and the upper surfaces of the electrodes 116a and 116b. In the said openings, the upper surfaces of the electrodes 112a and 112b and the upper surfaces of the electrodes 116a and 116b are exposed.

[0048] The light-emitting layer 114a is sandwiched between the semiconductor layer 113a and the semiconductor layer 115a. The light-emitting layer 114b is sandwiched between the semiconductor layer 113b and the semiconductor layer 115b. In the light-emitting layers 114a and 114b, electrons and holes are combined to emit light. Among the semiconductor layers 113a and 113b and the semiconductor layers 115a and 115b, one is an n-type semiconductor layer and the other is a p-type semiconductor layer.

[0049] The laminated structure including the semiconductor layer 113a, the light-emitting layer 114a, and the semiconductor layer 115a, and the laminated structure including the semiconductor layer 113b, the light-emitting layer 114b, and the semiconductor layer 115b are each formed so as to exhibit light such as red, yellow, green, or blue. It is preferable that the two laminated structures exhibit light of different colors. For these laminated structures, for example, gallium-phosphorus compounds, gallium-arsenic compounds, gallium-aluminum-arsenic compounds, aluminum-gallium-indium-phosphorus compounds, gallium nitrides, indium-gallium nitride compounds, selenium-zinc compounds, etc. can be used.

[0050] By forming the light-emitting diodes 110a and 110b to exhibit lights of different colors from each other, the step of forming the color conversion layer becomes unnecessary. Therefore, the manufacturing cost of the display device can be suppressed.

[0051] Also, the two stacked structures may exhibit light of the same color. At this time, the light emitted from the light-emitting layers 114a and 114b may be taken out to the outside of the display device through one or both of the color conversion layer and the coloring layer. Note that a configuration in which each pixel of each color has a light-emitting diode that exhibits light of the same color will be described later as Configuration Example 2 of the display device.

[0052] Also, the display device of the present embodiment may include a light-emitting diode that exhibits infrared light. The light-emitting diode that exhibits infrared light can be used, for example, as a light source of an infrared light sensor.

[0053] As the substrate 101, for example, single crystal substrates such as a sapphire (Al 2 O 3 ) substrate, a silicon carbide (SiC) substrate, a silicon (Si) substrate, and a gallium nitride (GaN) substrate can be used.

[0054] As shown in FIG. 1, the lights of the light-emitting diodes 110a and 110b are emitted toward the substrate 101 side. Therefore, the substrate 101 preferably has transparency to visible light. For example, the transparency of the substrate 101 to visible light can be enhanced by reducing the thickness by polishing or the like.

[0055] FIG. 2(B) shows a cross-sectional view of the circuit board 150B.

[0056] The circuit board 150B includes a substrate 151, an insulating layer 152, transistors 120a and 120b, conductive layers 184a, 184b, 187, 189, insulating layers 186, 188, and conductive layers 190a, 190b, 190c, and 190d. The circuit board 150B further includes insulating layers such as an insulating layer 162, insulating layers 181, 182, 183, and 185. One or more of these insulating layers may be regarded as components of the transistor, but in this embodiment, they will be described without including them as components of the transistor.

[0057] As the substrate 151, an insulating substrate such as a glass substrate, a quartz substrate, a sapphire substrate, or a ceramic substrate, or a semiconductor substrate such as a single crystal semiconductor substrate made of silicon, silicon carbide, a compound semiconductor substrate such as silicon germanium, or an SOI substrate can be used.

[0058] The substrate 151 preferably blocks visible light (is non-transmissive to visible light). By the substrate 151 blocking visible light, it is possible to suppress external light from entering the transistors 120a and 120b formed on the substrate 151. However, one aspect of the present invention is not limited to this, and the substrate 151 may have permeability to visible light.

[0059] An insulating layer 152 is provided on the substrate 151. The insulating layer 152 functions as a barrier layer that prevents impurities such as water and hydrogen from diffusing from the substrate 151 into the transistors 120a and 120b, and prevents oxygen from desorbing from the metal oxide layer 165 to the insulating layer 152 side. As the insulating layer 152, for example, a film such as an aluminum oxide film, a hafnium oxide film, or a silicon nitride film, in which hydrogen and oxygen diffuse less easily than a silicon oxide film, can be used.

[0060] The transistors 120a and 120b include a conductive layer 161, insulating layers 163 and 164, a metal oxide layer 165, a pair of conductive layers 166, an insulating layer 167, a conductive layer 168, and the like.

[0061] The metal oxide layer 165 has a channel formation region. The metal oxide layer 165 has a first region overlapping with one of the pair of conductive layers 166, a second region overlapping with the other of the pair of conductive layers 166, and a third region between the first region and the second region.

[0062] The conductive layer 161 and the insulating layer 162 are provided on the insulating layer 152, and the insulating layers 163 and 164 are provided so as to cover the conductive layer 161 and the insulating layer 162. The metal oxide layer 165 is provided on the insulating layer 164. The conductive layer 161 functions as a gate electrode, and the insulating layers 163 and 164 function as gate insulating layers. The conductive layer 161 overlaps with the metal oxide layer 165 via the insulating layers 163 and 164. Similar to the insulating layer 152, the insulating layer 163 preferably functions as a barrier layer. For the insulating layer 164 in contact with the metal oxide layer 165, it is preferable to use an oxide insulating film such as a silicon oxide film.

[0063] Here, the height of the upper surface of the conductive layer 161 is substantially the same as the height of the upper surface of the insulating layer 162. For example, after forming an opening in the insulating layer 162 and forming the conductive layer 161 so as to fill the opening, a planarization process is performed using a CMP method or the like, whereby the height of the upper surface of the conductive layer 161 and the height of the upper surface of the insulating layer 162 can be made the same. Thereby, the sizes of the transistors 120a and 120b can be reduced.

[0064] A pair of conductive layers 166 are provided spaced apart on the metal oxide layer 165. The pair of conductive layers 166 function as a source and a drain. An insulating layer 181 is provided to cover the metal oxide layer 165 and the pair of conductive layers 166, and an insulating layer 182 is provided on the insulating layer 181. Openings reaching the metal oxide layer 165 are provided in the insulating layer 181 and the insulating layer 182, and an insulating layer 167 and a conductive layer 168 are embedded inside the openings. The openings overlap with the third region. The insulating layer 167 overlaps with the side surfaces of the insulating layer 181 and the insulating layer 182. The conductive layer 168 overlaps with the side surfaces of the insulating layer 181 and the insulating layer 182 via the insulating layer 167. The conductive layer 168 functions as a gate electrode, and the insulating layer 167 functions as a gate insulating layer. The conductive layer 168 overlaps with the metal oxide layer 165 via the insulating layer 167.

[0065] Here, the height of the upper surface of the conductive layer 168 is substantially the same as the height of the upper surface of the insulating layer 182. For example, by providing an opening in the insulating layer 182 and forming the insulating layer 167 and the conductive layer 168 so as to fill the opening, and then performing a planarization process, the height of the upper surface of the conductive layer 168 and the height of the upper surface of the insulating layer 182 can be made the same. Thereby, the sizes of the transistors 120a and 120b can be reduced.

[0066] Then, an insulating layer 183 and an insulating layer 185 are provided to cover the upper surfaces of the insulating layer 182, the insulating layer 167, and the conductive layer 168. The insulating layer 181 and the insulating layer 183 preferably function as barrier layers in the same manner as the insulating layer 152. By covering the pair of conductive layers 166 with the insulating layer 181, it is possible to suppress the pair of conductive layers 166 from being oxidized by the oxygen contained in the insulating layer 182.

[0067] One of the pair of conductive layers 166 and a plug electrically connected to the conductive layer 187 are embedded in an opening provided in the insulating layer 181, the insulating layer 182, the insulating layer 183, and the insulating layer 185. The plug preferably has a conductive layer 184b that contacts the side surface of the opening and the upper surface of one of the pair of conductive layers 166, and a conductive layer 184a embedded more inward than the conductive layer 184b. At this time, as the conductive layer 184b, it is preferable to use a conductive material in which hydrogen and oxygen hardly diffuse.

[0068] In addition, in FIG. 1, a conductive layer 187 is provided on the insulating layer 185, and an insulating layer 186 is provided on the conductive layer 187. The insulating layer 186 is provided with an opening reaching the conductive layer 187, and a conductive layer 189 is embedded inside the opening. On the other hand, as shown in FIG. 2(B), a conductive layer 187 and an insulating layer 186 may be provided on the insulating layer 185, and an insulating layer 188 may be provided on the conductive layer 187. Here, the height of the upper surface of the conductive layer 187 is the same as or approximately the same as the height of the upper surface of the insulating layer 186. For example, after forming an opening in the insulating layer 186 and forming the conductive layer 187 so as to fill the opening, a planarization process is performed using a CMP method or the like, so that the height of the upper surface of the conductive layer 187 and the height of the upper surface of the insulating layer 186 can be made uniform. In FIG. 2(B), the insulating layer 188 is provided with an opening reaching the conductive layer 187, and a conductive layer 189 is embedded inside the opening. The conductive layer 189 functions as a plug that electrically connects the conductive layer 187 and the conductive layer 190a or the conductive layer 190c.

[0069] One of the pair of conductive layers 166 of the transistor 120a is electrically connected to the conductive layer 190a via the conductive layer 184a, the conductive layer 184b, the conductive layer 187, and the conductive layer 189.

[0070] Similarly, one of the pair of conductive layers 166 of the transistor 120b is electrically connected to the conductive layer 190c via the conductive layer 184a, the conductive layer 184b, the conductive layer 187, and the conductive layer 189.

[0071] In addition, examples of materials that can be used for various conductive layers constituting the display device of the present embodiment include metals such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten, or alloys mainly composed of these metals. Further, films containing these materials can be used as a single layer or in a laminated structure. For example, a single-layer structure of an aluminum film containing silicon, a two-layer structure in which an aluminum film is laminated on a titanium film, a two-layer structure in which an aluminum film is laminated on a tungsten film, a two-layer structure in which a copper film is laminated on a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is laminated on a titanium film, a two-layer structure in which a copper film is laminated on a tungsten film, a three-layer structure in which a titanium film or a titanium nitride film is provided, an aluminum film or a copper film is laminated thereon, and a titanium film or a titanium nitride film is further formed thereon, a three-layer structure in which a molybdenum film or a molybdenum nitride film is provided, an aluminum film or a copper film is laminated thereon, and a molybdenum film or a molybdenum nitride film is further formed thereon, and the like. Note that oxides such as indium oxide, tin oxide, or zinc oxide may be used. Further, using copper containing manganese is preferable because the controllability of the shape by etching is enhanced.

[0072] In addition, examples of materials that can be used for various insulating layers constituting the display device of the present embodiment include resins such as acrylic, polyimide, epoxy, and silicone, and inorganic insulating materials such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminum oxide.

[0073] Note that the circuit board 150B may have one or both of a reflective layer that reflects light from the light-emitting diode and a light-shielding layer that blocks the light.

[0074] As shown in FIG. 1, the electrodes 112a, 112b, 116a, and 116b provided on the LED substrate 150A are electrically connected to the conductive layers 190a, 190b, 190c, and 190d provided on the circuit board 150B, respectively.

[0075] For example, the electrode 116a and the conductive layer 190a are electrically connected via the conductor 117a. Thereby, the transistor 120a and the light emitting diode 110a can be electrically connected. The electrode 116a functions as a pixel electrode of the light emitting diode 110a.

[0076] Also, the electrode 112a and the conductive layer 190b are electrically connected via the conductor 117b. The electrode 112a functions as a common electrode of the light emitting diode 110a.

[0077] Similarly, the electrode 116b and the conductive layer 190c are electrically connected via the conductor 117c. Thereby, the transistor 120b and the light emitting diode 110b can be electrically connected. The electrode 116b functions as a pixel electrode of the light emitting diode 110b.

[0078] Also, the electrode 112b and the conductive layer 190d are electrically connected via the conductor 117d. The electrode 112b functions as a common electrode of the light emitting diode 110b.

[0079] For the conductors 117a to 117d, for example, conductive pastes such as silver, carbon, and copper, or bumps such as gold and solder can be preferably used. Further, for the electrodes 112a, 112b, 116a, 116b and the conductive layers 190a to 190d connected to the conductors 117a to 117d, it is preferable to use conductive materials with low contact resistance with the conductors 117a to 117d respectively. For example, when silver paste is used for the conductors 117a to 117d, it is preferable that the conductive materials connected to these are aluminum, titanium, copper, an alloy of silver (Ag), palladium (Pd), and copper (Cu) (Ag-Pd-Cu (APC)), etc., because the contact resistance is low.

[0080] FIG. 2(C) shows an example in which the conductors 117a to 117d are provided on the circuit board 150B side and the LED board 150A and the circuit board 150B are bonded together. Alternatively, the conductors 117a to 117d may be provided on the LED board 150A side and the LED board 150A and the circuit board 150B may be bonded together.

[0081] Note that a plurality of light-emitting diodes may be electrically connected to one transistor.

[0082] Next, FIG. 3 shows a cross-sectional view of the display device 100B.

[0083] The display device 100B shows an example in which the channel lengths of the transistors 120a and 120b are different from each other. Other configurations are the same as those of the display device 100A.

[0084] At least one of the size, channel length, channel width, and structure of the transistor 120a that drives the light-emitting diode 110a and the transistor 120b that drives the light-emitting diode 110b may be different from each other. For example, when the light-emitting diodes 110a and 110b exhibit light of different colors, the configuration of the transistor may be changed for each color. Specifically, one or both of the channel length and the channel width of the transistor may be changed for each color according to the current amount necessary to emit light with a desired luminance.

[0085] Next, FIG. 4 shows a cross-sectional view of the display device 100C.

[0086] The display device 100C includes a transistor having a channel formation region on a substrate (transistors 130a and 130b) and a transistor having a channel formation region in a metal oxide (transistors 120a and 120b) stacked thereon.

[0087] As the substrate 131, a single crystal silicon substrate is suitable. The transistors 130a and 130b have a conductive layer 135, an insulating layer 134, an insulating layer 136, and a pair of low resistance regions 133. The conductive layer 135 functions as a gate. The insulating layer 134 is located between the conductive layer 135 and the substrate 131 and functions as a gate insulating layer. The insulating layer 136 is provided to cover the side surface of the conductive layer 135 and functions as a sidewall. The pair of low resistance regions 133 are regions in the substrate 131 doped with impurities, one of which functions as the source of the transistor and the other functions as the drain of the transistor.

[0088] Also, an element isolation layer 132 is provided between two adjacent transistors so as to be embedded in the substrate 131.

[0089] An insulating layer 139 is provided to cover the transistors 130a and 130b, and a conductive layer 138 is provided on the insulating layer 139. Through the conductive layer 137 embedded in the opening of the insulating layer 139, the conductive layer 138 is electrically connected to one of the pair of low resistance regions 133. Also, an insulating layer 141 is provided to cover the conductive layer 138, and a conductive layer 142 is provided on the insulating layer 141. The conductive layer 138 and the conductive layer 142 each function as a wiring. Also, an insulating layer 143 and an insulating layer 152 are provided to cover the conductive layer 142, and transistors 120a and 120b are provided on the insulating layer 152. Since the laminated structure from the insulating layer 152 to the substrate 101 is the same as that of the display device 100A, detailed description thereof is omitted.

[0090] The transistors 120a and 120b can be used as the transistors constituting the pixel circuit. Also, the transistors 130a and 130b can be used as the transistors constituting the pixel circuit or the transistors constituting a driving circuit (one or both of a gate driver and a source driver) for driving the pixel circuit. Also, the transistors 120a, 120b, 130a, and 130b can be used as the transistors constituting various circuits such as an arithmetic circuit and a memory circuit.

[0091] With such a configuration, not only the pixel circuit but also the drive circuit and the like can be formed directly under the light-emitting diode. Therefore, compared with the case where the drive circuit is provided outside the display unit, the display device can be miniaturized. In addition, a display device with a narrow bezel (narrow non-display area) can be realized.

[0092] [Configuration Example 2 of Display Device] FIG. 5(A) shows a cross-sectional view of the display device 100D, and FIG. 5(B) shows a cross-sectional view of the display device 100E.

[0093] In the display device 100D and the display device 100E, each pixel has a light-emitting diode that emits light of the same color.

[0094] The display device 100D and the display device 100E have a substrate 191 provided with a colored layer CFR and a color conversion layer CCMR.

[0095] Specifically, the substrate 191 has a colored layer CFR and a color conversion layer CCMR in a region overlapping with the light-emitting diode 110a included in the red pixel. The color conversion layer CCMR has a function of converting blue light into red light.

[0096] In FIGS. 5(A) and 5(B), the light emitted from the light-emitting diode 110a included in the red pixel is converted from blue to red by the color conversion layer CCMR, and the purity of the red light is enhanced by the colored layer CFR, and then emitted to the outside of the display device 100D or the display device 100E.

[0097] Although not shown, similarly, the substrate 191 has a green colored layer and a color conversion layer that converts blue light into green in a region overlapping with the light-emitting diode included in the green pixel. Thereby, the light emitted from the light-emitting diode included in the green pixel is converted from blue to green by the color conversion layer, and the purity of the green light is enhanced by the colored layer, and then emitted to the outside of the display device.

[0098] On the other hand, the substrate 191 does not have a color conversion layer in the region overlapping with the light-emitting diode 110b included in the blue pixel. The substrate 191 may have a blue coloring layer in the region overlapping with the light-emitting diode 110b included in the blue pixel. When a blue coloring layer is provided, the purity of the blue light can be enhanced. When the blue coloring layer is not provided, the manufacturing process can be simplified.

[0099] The blue light emitted from the light-emitting diode 110b is emitted to the outside of the display device 100D or the display device 100E through the adhesive layer 192 and the substrate 191.

[0100] In the production of a display device having light-emitting diodes with the same configuration for each color pixel, only one type of light-emitting diode needs to be produced on the substrate. Therefore, compared with the case of producing a plurality of types of light-emitting diodes, the manufacturing apparatus and process can be simplified.

[0101] Since the substrate 191 is located on the side for extracting light from the light-emitting diode, it is preferable to use a material having high transmittance for visible light. Examples of the material that can be used for the substrate 191 include glass, quartz, sapphire, resin, and the like. A film such as a resin film may be used for the substrate 191. This enables the display device to be made lighter and thinner.

[0102] As the color conversion layer, it is preferable to use a phosphor or quantum dots (QD: Quantum dot). In particular, quantum dots have a narrow peak width of the emission spectrum and can obtain light emission with good color purity. Thereby, the display quality of the display device can be enhanced.

[0103] The color conversion layer can be formed using a droplet discharge method (for example, an inkjet method), a coating method, an imprint method, various printing methods (screen printing, offset printing), etc. Also, a color conversion film such as a quantum dot film may be used.

[0104] The materials constituting the quantum dots are not particularly limited. For example, they include group 14 elements, group 15 elements, group 16 elements, compounds composed of a plurality of group 14 elements, compounds of elements belonging to groups 4 to 14 and group 16 elements, compounds of group 2 elements and group 16 elements, compounds of group 13 elements and group 15 elements, compounds of group 13 elements and group 17 elements, compounds of group 14 elements and group 15 elements, compounds of group 11 elements and group 17 elements, iron oxides, titanium oxides, chalcogenide spinels, various semiconductor clusters, and the like.

[0105] Specifically, cadmium selenide, cadmium sulfide, cadmium telluride, zinc selenide, zinc oxide, zinc sulfide, zinc telluride, mercury sulfide, mercury selenide, mercury telluride, indium arsenide, indium phosphide, gallium arsenide, gallium phosphide, indium nitride, gallium nitride, indium antimonide, gallium antimonide, aluminum phosphide, aluminum arsenide, aluminum antimonide, lead selenide, lead telluride, lead sulfide, indium selenide, indium telluride, indium sulfide, gallium selenide, arsenic sulfide, arsenic selenide, arsenic telluride, antimony sulfide, antimony selenide, antimony telluride, bismuth sulfide, bismuth selenide, bismuth telluride, silicon, silicon carbide, germanium, tin, selenium, tellurium, boron, carbon, phosphorus, boron nitride, boron phosphide, boron arsenide, aluminum nitride, aluminum sulfide, barium sulfide, barium selenide, barium telluride, calcium sulfide, calcium selenide, calcium telluride, beryllium sulfide, beryllium selenide, beryllium telluride, magnesium sulfide, magnesium selenide, germanium sulfide, germanium selenide, germanium telluride, tin sulfide, tin selenide, tin telluride, lead oxide, copper fluoride, copper chloride, copper bromide, copper iodide, copper oxide, copper selenide, nickel oxide, cobalt oxide, cobalt sulfide, iron oxide, iron sulfide, manganese oxide, molybdenum sulfide, vanadium oxide, tungsten oxide, tantalum oxide, titanium oxide, zirconium oxide, silicon nitride, germanium nitride, aluminum oxide, barium titanate, a compound of selenium, zinc, and cadmium, a compound of indium, arsenic, and phosphorus, a compound of cadmium, selenium, and sulfur, a compound of cadmium, selenium, and tellurium, a compound of indium, gallium, and arsenic, a compound of indium, gallium, and selenium, a compound of indium, selenium, and sulfur, a compound of copper, indium, and sulfur, and combinations thereof, etc. are mentioned. Also, so-called alloy-type quantum dots with an arbitrarily expressed composition ratio may be used.

[0106] Examples of the structure of quantum dots include core type, core-shell type, core-multi-shell type, etc. Also, since quantum dots have a high proportion of surface atoms, they are highly reactive and prone to aggregation. Therefore, it is preferable that a protective agent is attached to or a protecting group is provided on the surface of the quantum dots. By attaching the protective agent or providing the protecting group, aggregation can be prevented and the solubility in a solvent can be increased. It is also possible to reduce the reactivity and improve the electrical stability.

[0107] Since the bandgap of quantum dots increases as their size decreases, the size of the quantum dots is appropriately adjusted so as to obtain light of a desired wavelength. As the size of the crystal decreases, the emission of the quantum dots shifts toward the blue side, that is, toward the high-energy side. Therefore, by changing the size of the quantum dots, the emission wavelength can be adjusted over the wavelength regions of the spectra in the ultraviolet region, visible region, and infrared region. The size (diameter) of the quantum dots is, for example, 0.5 nm or more and 20 nm or less, preferably 1 nm or more and 10 nm or less. The narrower the size distribution of the quantum dots, the narrower the emission spectrum becomes, and light emission with good color purity can be obtained. Also, the shape of the quantum dots is not particularly limited, and may be spherical, rod-shaped, disk-shaped, or other shapes. A quantum rod, which is a rod-shaped quantum dot, has a function of exhibiting light with directivity.

[0108] The colored layer is a colored layer that transmits light in a specific wavelength range. For example, a color filter that transmits light in the wavelength range of red, green, blue, or yellow can be used. Examples of materials that can be used for the colored layer include metal materials, resin materials, and resin materials containing pigments or dyes.

[0109] The display device 100D can be manufactured by first bonding a circuit board and an LED board as in the display device 100A, then peeling off the board 101 of the LED board, and bonding a board 191 provided with a colored layer CFR, a color conversion layer CCMR, etc. using an adhesive layer 192 to the surface exposed by the peeling.

[0110] The method of peeling the substrate 101 is not limited. For example, as shown in FIG. 6(A), a method of irradiating the entire surface of the substrate 101 with a laser beam can be mentioned. Thereby, the substrate 101 can be peeled off, and the protective layer 102 and the light-emitting diodes 110a and 110b can be exposed (FIG. 6(B)).

[0111] As the laser, an excimer laser, a solid-state laser, etc. can be used. For example, a diode-pumped solid-state laser (DPSS) may be used.

[0112] A peeling layer may be provided between the substrate 101 and the light-emitting diodes 110a and 110b.

[0113] The peeling layer can be formed using an organic material or an inorganic material.

[0114] Examples of the organic material that can be used for the peeling layer include polyimide resin, acrylic resin, epoxy resin, polyamide resin, polyimide amide resin, siloxane resin, benzocyclobutene-based resin, phenol resin, etc.

[0115] Examples of the inorganic material that can be used for the peeling layer include metals containing elements selected from tungsten, molybdenum, titanium, tantalum, niobium, nickel, cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium, iridium, silicon, alloys containing the element, or compounds containing the element. The crystal structure of the layer containing silicon may be amorphous, microcrystalline, or polycrystalline.

[0116] For the adhesive layer 192, various curable adhesives such as ultraviolet curable type and other light curable adhesives, reaction curable adhesives, thermosetting adhesives, anaerobic adhesives, etc. can be used. Also, an adhesive sheet or the like may be used.

[0117] Also, as shown in the display device 100E, a substrate 191 provided with a colored layer CFR, a color conversion layer CCMR, etc. may be bonded to the substrate 101 using an adhesive layer 192. That is, it may not be necessary to peel the substrate 101.

[0118] At this time, it is preferable to reduce the thickness of the substrate 101 by polishing or the like. Thereby, the extraction efficiency of the light emitted by the light emitting diode can be increased. Also, the display device can be made thinner and lighter.

[0119] The display device 100E can be manufactured by first bonding a circuit board and an LED board as in the display device 100A, then polishing the substrate 101 included in the LED board, and bonding a substrate 191 provided with a colored layer CFR, a color conversion layer CCMR, etc. to the polished surface of the substrate 101 using an adhesive layer 192.

[0120] [Configuration Example 3 of Display Device] FIG. 7 shows a cross-sectional view of the display device 100F.

[0121] A display device according to an aspect of the present invention may be a display device (also referred to as an input / output device or a touch panel) equipped with a touch sensor. The configurations of the above-described display devices can be applied to the touch panel. The display device 100F is an example in which a touch sensor is mounted on the display device 100A.

[0122] There is no limitation on the detection element (also referred to as a sensor element) included in a touch panel according to an aspect of the present invention. Various sensors capable of detecting the proximity or contact of a detected object such as a finger or a stylus can be applied as the detection element.

[0123] As the sensor method, for example, various methods such as a capacitance method, a resistive film method, a surface acoustic wave method, an infrared method, an optical method, and a pressure-sensitive method can be used.

[0124] In the present embodiment, a touch panel having a capacitance-type detection element will be described as an example.

[0125] As capacitance methods, there are surface capacitance methods, projection capacitance methods, etc. Also, as projection capacitance methods, there are self-capacitance methods, mutual-capacitance methods, etc. Using the mutual-capacitance method is preferable because it enables simultaneous multi-point detection.

[0126] The touch panel according to one aspect of the present invention can adopt various configurations, such as a configuration in which a separately manufactured display device and a detection element are bonded together, or a configuration in which electrodes and the like constituting the detection element are provided on one or both of the substrate supporting the display element and the counter substrate.

[0127] In the display device 100F, the laminated structure from the substrate 151 to the substrate 101 is the same as that of the display device 100A, so detailed description thereof is omitted.

[0128] The conductive layer 187b is electrically connected to the FPC1 via the conductive layer 189b, the conductive layer 190e, and the conductor 195. Signals and power are supplied to the display device 100F via the FPC1.

[0129] The conductive layer 187b can be formed of the same material and in the same process as the conductive layer 187a. The conductive layer 189b can be formed of the same material and in the same process as the conductive layer 189a. The conductive layer 190e can be formed of the same material and in the same process as the conductive layers 190a to 190d.

[0130] As the conductor 195, for example, an anisotropic conductive film (ACF: Anisotropic Conductive Film) or an anisotropic conductive paste (ACP: Anisotropic Conductive Paste) can be used.

[0131] A touch sensor is provided on the substrate 171. The substrate 171 and the substrate 101 are bonded together by an adhesive layer 179 with the surface of the substrate 171 on which the touch sensor is provided facing the substrate 101 side.

[0132] On the side of the substrate 171 facing the substrate 101, electrodes 177 and 178 are provided. Electrodes 177 and 178 are formed on the same plane. For electrodes 177 and 178, a material that transmits visible light is used. The insulating layer 173 is provided so as to cover electrodes 177 and 178. The electrode 174 is electrically connected to two electrodes 178 provided so as to sandwich the electrode 177 through an opening provided in the insulating layer 173.

[0133] A wiring 172 obtained by processing the same conductive layer as electrodes 177 and 178 is connected to a conductive layer 175 obtained by processing the same conductive layer as the electrode 174. The conductive layer 175 is electrically connected to the FPC2 through a connector 176.

[0134] [Configuration Example of Transistor] The transistor that can be used in the display device according to one aspect of the present invention is not limited to the configurations of the transistors 120a and 120b shown in FIG. 1 and the like. Hereinafter, with reference to FIGS. 8 and 9, a configuration example of a transistor that can be used in the display device according to one aspect of the present invention will be described.

[0135] FIG. 8(A) shows a top view of the transistor 300. In FIG. 8(A), for clarity of the drawing, illustration of some elements is omitted. FIG. 8(B) shows a cross-sectional view taken along the dashed line A1 - A2 in FIG. 8(A). FIG. 8(B) can be said to be a cross-sectional view of the transistor 300 in the channel length direction. FIG. 8(C) shows a cross-sectional view taken along the dashed line A3 - A4 in FIG. 8(A). FIG. 8(C) can be said to be a cross-sectional view of the transistor 300 in the channel width direction.

[0136] FIG. 9(A) shows a top view of the transistor 300A. In FIG. 9(A), for clarity of the drawing, illustration of some elements is omitted. FIG. 9(B) shows a cross-sectional view taken along the dashed line A1 - A2 in FIG. 9(A). FIG. 9(B) can be said to be a cross-sectional view of the transistor 300A in the channel length direction. FIG. 9(C) shows a cross-sectional view taken along the dashed line A3 - A4 in FIG. 9(A). FIG. 9(C) can be said to be a cross-sectional view of the transistor 300A in the channel width direction.

[0137] Note that the transistor 300A shown in FIG. 9 is a modified example of the transistor 300 shown in FIG. 8. The oxide layer 330c, the insulating layer 354, and the insulating layer 380 are each a single-layer structure in FIG. 8 and each a stacked structure in FIG. 9. Other configurations are the same in FIGS. 8 and 9.

[0138] Note that in this specification etc., a transistor is an element having at least three terminals including a gate, a drain, and a source. And it has a region (hereinafter also referred to as a channel formation region) in which a channel is formed between a drain (drain terminal, drain region, or drain electrode) and a 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 etc., the channel formation region refers to a region where current mainly flows.

[0139] Also, the functions of the source and the drain may be interchanged when transistors of different polarities are employed or when the direction of current changes in a circuit operation. For this reason, in this specification etc., the terms source and drain may be used interchangeably in some cases.

[0140] Note that the channel length is, for example, in a top view of a transistor, the region where a semiconductor (or the portion where current flows in the semiconductor when the transistor is in the on state) and the gate electrode overlap each other, or the distance between a source (source region or source electrode) and a drain (drain region or drain electrode) in the channel formation region. Note that in one transistor, the channel length does not necessarily take the same value in all regions. That is, the channel length of one transistor may not be determined to be one value. Therefore, in this specification, the channel length is taken as any one value, the maximum value, the minimum value, or the average value in the channel formation region.

[0141] The channel width refers to, for example, in a top view of a transistor, the length of the channel formation region in the vertical direction with respect to the channel length direction in the region where the semiconductor (or the portion where current flows in the semiconductor when the transistor is in the on state) and the gate electrode overlap each other, or in the channel formation region. Note that in one transistor, the channel width does not necessarily take the same value in all regions. That is, the channel width of one transistor may not be determined by a single value. Therefore, in this specification, the channel width is taken as any one value, the maximum value, the minimum value, or the average value in the channel formation region.

[0142] Note that in this specification and the like, depending on the structure of the transistor, the channel width in the region where the channel is actually formed (hereinafter also referred to as the "effective channel width") may be different from the channel width shown in the top view of the transistor (hereinafter also referred to as the "apparent channel width"). For example, when the gate electrode covers the side surface of the semiconductor, the effective channel width may be larger than the apparent channel width, and the influence may become non-negligible. For example, in a fine transistor in which the gate electrode covers the side surface of the semiconductor, the ratio of the channel formation region formed on the side surface of the semiconductor may increase. In that case, the effective channel width is larger than the apparent channel width.

[0143] In such a case, it may be difficult to estimate the effective channel width by actual measurement. For example, in order to estimate the effective channel width from the design value, it is necessary to assume that the shape of the semiconductor is known. Therefore, when the shape of the semiconductor is not accurately known, it is difficult to accurately measure the effective channel width.

[0144] In this specification, when simply described as the channel width, it may refer to the apparent channel width. Or, in this specification, when simply described as the channel width, it may refer to the effective channel width. Note that the channel length, the channel width, the effective channel width, the apparent channel width, etc. can have their values determined by analyzing a cross-sectional TEM image or the like.

[0145] Transistor 300 is disposed on a substrate (not shown) via an insulating layer 314 and is disposed to be embedded in an insulating layer 316, a conductive layer 305 disposed on the insulating layer 316 and on the conductive layer 305, an insulating layer 322 disposed on the insulating layer 322, an insulating layer 324 disposed on the insulating layer 324, an oxide layer 330 (oxide layer 330a, oxide layer 330b, and oxide layer 330c) disposed on the oxide layer 330, an insulating layer 350 disposed on the oxide layer 330, a conductive layer 360 (conductive layer 360a and conductive layer 360b) disposed on the insulating layer 350, conductive layers 342a and 342b in contact with a part of the upper surface of the oxide layer 330b, and an insulating layer 354 disposed in contact with a part of the upper surface of the insulating layer 324, the side surfaces of the oxide layer 330a, the side surfaces of the oxide layer 330b, the side surfaces and the upper surface of the conductive layer 342a, and the side surfaces and the upper surface of the conductive layer 342b.

[0146] On the transistor 300, an insulating layer 380, an insulating layer 374, and an insulating layer 381 that each function as an interlayer film are provided. Further, the transistor 300 is electrically connected to a conductive layer 340 (conductive layer 340a and conductive layer 340b) that functions as a plug. Note that insulating layers 341 (insulating layer 341a and insulating layer 341b) are provided in contact with the side surfaces of the conductive layer 340.

[0147] The oxide layer 330 preferably has an oxide layer 330a disposed on the insulating layer 324, an oxide layer 330b disposed on the oxide layer 330a, and an oxide layer 330c disposed on the oxide layer 330b and at least partially in contact with the upper surface of the oxide layer 330b. By having the oxide layer 330a under the oxide layer 330b, diffusion of impurities from a structure formed below the oxide layer 330a into the oxide layer 330b can be suppressed. Also, by having the oxide layer 330c on the oxide layer 330b, diffusion of impurities from a structure formed above the oxide layer 330c into the oxide layer 330b can be suppressed.

[0148] Note that, in the transistor 300, an example where the oxide layer 330 has a three-layer structure of the oxide layer 330a, the oxide layer 330b, and the oxide layer 330c is shown, but the present invention is not limited to this. The oxide layer 330 may be, for example, a single layer of the oxide layer 330b, a two-layer structure of the oxide layer 330a and the oxide layer 330b, a two-layer structure of the oxide layer 330b and the oxide layer 330c, or a laminated structure of four or more layers. Further, each of the oxide layer 330a, the oxide layer 330b, and the oxide layer 330c may have a laminated structure.

[0149] On the oxide layer 330b, a conductive layer 342 (the conductive layer 342a and the conductive layer 342b) is provided. The film thickness of the conductive layer 342 can be, for example, 1 nm or more and 50 nm or less, preferably 2 nm or more and 25 nm or less.

[0150] The conductive layer 360 functions as the first gate (also referred to as a top gate) electrode of the transistor 300, and the conductive layer 342a and the conductive layer 342b each function as a source electrode or a drain electrode of the transistor 300.

[0151] It is preferable to use a metal oxide (hereinafter also referred to as an oxide semiconductor) that functions as a semiconductor in the oxide layer 330 having a channel formation region in the transistor 300. By using an oxide semiconductor in the channel formation region of the transistor, a transistor with high field-effect mobility can be realized. Further, a highly reliable transistor can be realized.

[0152] As the above metal oxide, it is preferable to use one having a band gap of 2.0 eV or more, preferably 2.5 eV or more. By using a metal oxide having a large band gap in the oxide layer 330, the off-current of the transistor can be reduced. By using such a transistor, a display device with low power consumption can be provided.

[0153] For example, as the oxide layer 330, a metal oxide such as an In-M-Zn oxide having indium (In), element M, and zinc (Zn) (element M is one or more selected from aluminum, gallium, yttrium, tin, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used. In particular, as element M, aluminum, gallium, yttrium, or tin may be used. Further, as the oxide layer 330, an In-M oxide, an In-Zn oxide, or an M-Zn oxide may be used.

[0154] For the transistor 300, it is preferable to use a metal oxide with a low carrier density. When reducing the carrier density of the metal oxide, the impurity concentration in the metal oxide may be lowered, and the density of defect levels may be lowered. In this specification and the like, a low impurity concentration and a low density of defect levels are referred to as high-purity intrinsic or substantially high-purity intrinsic. Note that examples of impurities in the metal oxide include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0155] In particular, since hydrogen contained in the metal oxide reacts with oxygen bonded to the metal atom to form water, oxygen vacancies may be formed in the metal oxide. If the channel formation region in the metal oxide contains oxygen vacancies, the transistor may have normally-on characteristics. Further, defects in which hydrogen enters the oxygen vacancies may function as donors, and electrons serving as carriers may be generated. Also, a part of hydrogen may bond with oxygen bonded to the metal atom to generate electrons serving as carriers. Therefore, a transistor using a metal oxide containing a large amount of hydrogen is likely to have normally-on characteristics.

[0156] Therefore, when using a metal oxide for the oxide layer 330, it is preferable that hydrogen in the metal oxide is reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is 20 atoms / cm 3 less than 1×10 19 atoms / cm 3 , preferably less than 1×10 18 atoms / cm 3 , more preferably less than 5×10 18 atoms / cm 3 , and even more preferably less than 1×10 18 atoms / cm 3 . By using a metal oxide with sufficiently reduced impurities such as hydrogen in the channel formation region of the transistor, stable electrical characteristics can be imparted.

[0157] When using a metal oxide for the oxide layer 330, since the conductive layer 342 (conductive layer 342a and conductive layer 342b) is in contact with the oxide layer 330, oxygen in the oxide layer 330 may diffuse into the conductive layer 342, causing the conductive layer 342 to oxidize. When the conductive layer 342 oxidizes, there is a high probability that the conductivity of the conductive layer 342 will decrease. Note that the diffusion of oxygen in the oxide layer 330 into the conductive layer 342 can be rephrased as the conductive layer 342 absorbing oxygen in the oxide layer 330.

[0158] When oxygen in the oxide layer 330 diffuses into the conductive layer 342 (conductive layer 342a and conductive layer 342b), layers may be formed between the conductive layer 342a and the oxide layers 330b and 330c, and between the conductive layer 342b and the oxide layers 330b and 330c, respectively. Since the layer contains more oxygen than the conductive layer 342, it is presumed to have insulating properties. At this time, the three-layer structure of the conductive layer 342, the layer, and the oxide layer 330b or 330c can be regarded as a three-layer structure composed of a metal-insulator-semiconductor, and may be referred to as a MIS (Metal-Insulator-Semiconductor) structure.

[0159] Therefore, it is preferable that the conductive layer 342 (conductive layer 342a and conductive layer 342b) is made of a conductive material having the property that hydrogen in the oxide layer 330 easily diffuses into the conductive layer 342 and oxygen in the oxide layer 330 hardly diffuses into the conductive layer 342. Thereby, when hydrogen in the oxide layer 330 diffuses into the conductive layer 342, the hydrogen concentration in the oxide layer 330 is reduced, and stable electrical characteristics can be imparted to the transistor 300. In this specification and the like, the fact that hydrogen in the oxide easily diffuses into the conductive layer may be expressed as the conductive layer easily extracts (easily absorbs) hydrogen in the oxide. Further, the fact that oxygen in the oxide hardly diffuses into the conductive layer may be expressed as the conductive layer is hardly oxidized, the conductive layer has oxidation resistance, and the like.

[0160] Examples of the conductive material include conductors containing tantalum (Ta), titanium (Ti), and the like. In particular, it is preferable to use a conductor containing tantalum for the conductive layer 342. The conductor containing tantalum may contain nitrogen or oxygen. Therefore, the conductor containing tantalum preferably satisfies the composition formula TaN x O y (where x is a real number greater than 0 and less than or equal to 1.67, and y is a real number greater than or equal to 0 and less than or equal to 1.0). The conductor containing tantalum includes metallic tantalum, tantalum oxide, tantalum nitride, tantalum oxynitride, oxynitride tantalum, and the like. Therefore, in this specification and the like, the conductor containing tantalum may be denoted as TaN x O y .

[0161] TaN x O y In TaN x O y , it is preferable that the ratio of tantalum is higher. Or, it is preferable that the ratios of nitrogen and oxygen are lower, and it is preferable that the values of x and y are smaller. By increasing the ratio of tantalum, the resistivity of TaN x O y is lowered, and good electrical characteristics can be imparted to the transistor 300 using the TaN x O y for the conductive layer 342.

[0162] Also, TaNx O y In O, it is preferable that the ratio of nitrogen is higher and the value of x is larger. TaN with a higher nitrogen ratio x O y By using it for the conductive layer 342, oxidation of the conductive layer 342 can be suppressed. Also, the film thickness of the layer formed between the conductive layer 342 and the oxide layer 330 can be reduced.

[0163] Note that the hydrogen diffused into the conductive layer 342 may remain in the conductive layer 342. In other words, the hydrogen in the oxide layer 330 may be absorbed by the conductive layer 342. Also, the hydrogen in the oxide layer 330 may permeate through the conductive layer 342 and be released to the structure provided around the conductive layer 342 or outside the transistor 300.

[0164] To reduce the hydrogen concentration in the oxide layer 330 and suppress the formation of a layer between the conductive layer 342 and the oxide layer 330, it is preferable that the conductive layer 342 is made of a conductive material having a property that hydrogen in the oxide layer 330 easily diffuses into the conductive layer 342, and a layer having a function of suppressing oxidation of the conductive layer 342 is provided between the conductive layer 342 and the oxide layer 330. By providing such a layer, the conductive layer 342 and the oxide layer 330 are not in contact with each other, so that it is possible to suppress the conductive layer 342 from absorbing oxygen in the oxide layer 330.

[0165] Hereinafter, the detailed configuration of the transistor 300 will be described.

[0166] The insulating layer 314 preferably functions as an insulating barrier film that suppresses the diffusion of impurities such as water and hydrogen from the substrate side into the transistor 300. Therefore, it is preferable to use an insulating material for the insulating layer 314 that has a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N 2 O, NO, NO 2 etc.), and copper atoms. Or, it is preferable to use an insulating material that has a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0167] In this specification, the function of suppressing the diffusion of impurities or oxygen means the function of suppressing the diffusion of any one or all of the impurities or the oxygen. Further, a film having the function of suppressing the diffusion of hydrogen or oxygen may be referred to as a film through which hydrogen or oxygen hardly permeates, a film having low permeability to hydrogen or oxygen, a film having a barrier property against hydrogen or oxygen, a barrier film against hydrogen or oxygen, or the like. Further, when the barrier film has conductivity, the barrier film may be referred to as a conductive barrier film.

[0168] For example, as the insulating layer 314, it is preferable to use an aluminum oxide film, a silicon nitride film, or the like. Thereby, it is possible to suppress the diffusion of impurities such as water and hydrogen from the substrate side to the transistor 300 side rather than the insulating layer 314. Or, it is possible to suppress the diffusion of oxygen contained in the insulating layer 324 or the like to the substrate side rather than the insulating layer 314. Note that the insulating layer 314 may have a laminated structure of two or more layers. In that case, it is not limited to a laminated structure made of the same material, and a laminated structure made of different materials may also be used. For example, a laminate of an aluminum oxide film and a silicon nitride film may be used.

[0169] Further, for example, as the insulating layer 314, it is preferable to use a silicon nitride film formed by a sputtering method. Thereby, the hydrogen concentration in the insulating layer 314 can be lowered, and the diffusion of impurities such as water and hydrogen from the substrate side to the transistor 300 side rather than the insulating layer 314 can be further suppressed.

[0170] The insulating layer 316 that functions as an interlayer film preferably has a lower dielectric constant than the insulating layer 314. By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance generated between wirings can be reduced. For example, as the insulating layer 316, a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a silicon nitride film, a silicon oxide film added with fluorine, a silicon oxide film added with carbon, a silicon oxide film added with carbon and nitrogen, a silicon oxide film having pores, or the like may be appropriately used.

[0171] The insulating layer 316 preferably has a region with a low hydrogen concentration and an excess of oxygen relative to the stoichiometric composition (hereinafter also referred to as the excess oxygen region) or oxygen that is released by heating (hereinafter also referred to as excess oxygen). For example, as the insulating layer 316, it is preferable to use a silicon oxide film formed by a sputtering method. Thereby, the mixing of hydrogen into the oxide layer 330 can be suppressed, or oxygen can be supplied to the oxide layer 330 to reduce oxygen deficiencies in the oxide layer 330. Therefore, it is possible to provide a transistor that suppresses fluctuations in electrical characteristics, has stable electrical characteristics, and has improved reliability.

[0172] The insulating layer 316 may have a laminated structure. For example, in the insulating layer 316, a configuration may be adopted in which an insulating layer similar to the insulating layer 314 is provided at least in a portion that contacts the side surface of the conductive layer 305. By adopting such a configuration, oxidation of the conductive layer 305 by the oxygen contained in the insulating layer 316 can be suppressed. Alternatively, it is possible to suppress a decrease in the amount of oxygen contained in the insulating layer 316 due to the conductive layer 305.

[0173] The conductive layer 305 may function as a second gate (also referred to as a bottom gate) electrode. In that case, by changing the potential applied to the conductive layer 305 independently without linking it to the potential applied to the conductive layer 360, the threshold voltage (V th ) of the transistor 300 can be controlled. In particular, by applying a negative potential to the conductive layer 305, it is possible to increase the V th of the transistor 300 and reduce the off-current. Therefore, applying a negative potential to the conductive layer 305 can make the drain current smaller when the potential applied to the conductive layer 360 is 0 V than when no potential is applied.

[0174] The conductive layer 305 is arranged so as to overlap the oxide layer 330 and the conductive layer 360. Further, the conductive layer 305 is preferably provided so as to be embedded in the insulating layer 314 or the insulating layer 316.

[0175] As shown in FIG. 8(B), the conductive layer 305 may be provided to be larger than the channel formation region in the oxide layer 330. In particular, as shown in FIG. 8(C), it is preferable that the conductive layer 305 extends also in a region outside the end portion intersecting with the channel width direction of the oxide layer 330. That is, it is preferable that the conductive layer 305 and the conductive layer 360 overlap via an insulating layer outside the side surface in the channel width direction of the oxide layer 330. By having such a configuration, the channel formation region of the oxide layer 330 can be electrically surrounded by the electric field of the conductive layer 360 functioning as the first gate electrode and the electric field of the conductive layer 305 functioning as the second gate electrode.

[0176] As shown in FIG. 8(C), the conductive layer 305 is extended to also function as a wiring. However, the present invention is not limited to this, and a configuration may be adopted in which a conductive layer functioning as a wiring is provided under the conductive layer 305. Also, the conductive layer 305 does not necessarily have to be provided one by one for each transistor. For example, a configuration may be adopted in which the conductive layer 305 is shared by a plurality of transistors.

[0177] In the transistor 300, an example is shown in which the conductive layer 305 has a two-layer stacked structure (the first conductive layer on the insulating layer 314 and the second conductive layer on the first conductive layer), but the present invention is not limited to this. For example, the conductive layer 305 may have a single layer or a stacked structure of three or more layers. When the structure has a stacked structure, ordinal numbers may be assigned in the formation order for distinction.

[0178] Here, for the first conductive layer of the conductive layer 305, it is preferable to use a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N 2 O, NO, NO 2 etc.), and copper atoms. Alternatively, it is preferable to use a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0179] By using a conductive material having a function of suppressing oxygen diffusion for the first conductive layer of the conductive layer 305, it is possible to suppress the oxidation of the second conductive layer of the conductive layer 305 and the decrease in conductivity. As the conductive material having a function of suppressing oxygen diffusion, for example, tantalum, tantalum nitride, ruthenium, ruthenium oxide, etc. are preferably used. Therefore, the first conductive layer of the conductive layer 305 is preferably a single-layer structure or a laminated structure using the above conductive material. For example, the first conductive layer of the conductive layer 305 may be a laminate of a tantalum film, a tantalum nitride film, a ruthenium film, or a ruthenium oxide film and a titanium film or a titanium nitride film.

[0180] For the second conductive layer of the conductive layer 305, it is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum. In FIG. 8(B) etc., the second conductive layer of the conductive layer 305 is shown as a single layer, but it may also be a laminated structure. For example, it may be a laminate of a titanium film or a titanium nitride film and a film containing the conductive material.

[0181] The insulating layer 322 and the insulating layer 324 function as a gate insulating layer.

[0182] The insulating layer 322 preferably has a function of suppressing the diffusion of hydrogen (for example, at least one of a hydrogen atom, a hydrogen molecule, etc.). Further, the insulating layer 322 preferably has a function of suppressing the diffusion of oxygen (for example, at least one of an oxygen atom, an oxygen molecule, etc.). For example, it is preferable that the insulating layer 322 can suppress the diffusion of one or both of hydrogen and oxygen more than the insulating layer 324.

[0183] As the material of the insulating layer 322, an insulator containing one or both oxides of aluminum and hafnium, which are insulating materials, may be used. As the insulator, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), etc. When the insulating layer 322 is formed using such a material, the insulating layer 322 functions as a layer that suppresses the release of oxygen from the oxide layer 330 to the substrate side and the diffusion of impurities such as hydrogen from the peripheral portion of the transistor 300 to the oxide layer 330. Therefore, by providing the insulating layer 322, the diffusion of impurities such as hydrogen into the inside of the transistor 300 can be suppressed, and the generation of oxygen vacancies in the oxide layer 330 can be suppressed. Also, it is possible to suppress the reaction of the conductive layer 305 with the oxygen contained in the insulating layer 324 and the oxide layer 330.

[0184] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, zirconium oxide may be added to the above insulator. Alternatively, these insulators may be nitrided. Also, the insulating layer 322 may be used by laminating a silicon oxide film, a silicon oxynitride film, or a silicon nitride film on an insulating film containing these insulators.

[0185] The insulating layer 322 may be formed in a single-layer structure or a laminated structure using an insulating material containing a so-called high-k material such as aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO 3 )、(Ba,Sr)TiO 3 (BST). As the miniaturization and high integration of transistors progress, problems such as leakage current may occur due to the thinning of the gate insulating layer. By using a high-k material for the insulating layer that functions as the gate insulating layer, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0186] The insulating layer 324 in contact with the oxide layer 330 preferably desorbs oxygen upon heating. For example, as the insulating layer 324, a silicon oxide film, a silicon oxynitride film, or the like may be appropriately used. By providing an insulating layer containing oxygen in contact with the oxide layer 330, oxygen vacancies in the oxide layer 330 can be reduced, and the reliability of the transistor 300 can be improved.

[0187] Specifically, as the insulating layer 324, it is preferable to use an oxide material that desorbs some oxygen upon heating. An oxide layer that desorbs oxygen upon heating means that, in TDS (Thermal Desorption Spectroscopy) analysis, the desorption amount of oxygen molecules is 1.0×10 18 molecules / cm 3 or more, preferably 1.0×10 19 molecules / cm 3 or more, more preferably 2.0×10 19 molecules / cm 3 or more, or 3.0×10 20 molecules / cm 3 or more. The surface temperature of the film during the above TDS analysis is preferably in the range of 100°C or more and 700°C or less, or 100°C or more and 400°C or less.

[0188] The insulating layer 324 preferably has a low hydrogen concentration and an excess oxygen region or contains excess oxygen. For example, it may be provided using the same material as the insulating layer 316.

[0189] The insulating layer 322 and the insulating layer 324 may have a laminated structure of two or more layers. In that case, it is not limited to a laminated structure made of the same material, and a laminated structure made of different materials may also be used.

[0190] The oxide layer 330 preferably has a laminated structure with oxides having different chemical compositions. Specifically, in the metal oxide used for the oxide layer 330a, the atomic ratio of element M to the metal element that is the main component is preferably larger than the atomic ratio of element M to the metal element that is the main component in the metal oxide used for the oxide layer 330b. Also, in the metal oxide used for the oxide layer 330a, the atomic ratio of element M to In is preferably larger than the atomic ratio of element M to In in the metal oxide used for the oxide layer 330b. Further, in the metal oxide used for the oxide layer 330b, the atomic ratio of In to element M is preferably larger than the atomic ratio of In to element M in the metal oxide used for the oxide layer 330a. Also, the oxide layer 330c can use a metal oxide that can be used for the oxide layer 330a or the oxide layer 330b.

[0191] The oxide layer 330b and the oxide layer 330c preferably have crystallinity. For example, it is preferable to use CAAC-OS (c-axis aligned crystalline oxide semiconductor) described later. Oxides having crystallinity such as CAAC-OS have a dense structure with few impurities and defects (such as oxygen deficiencies) and high crystallinity. Therefore, it is possible to suppress the extraction of oxygen from the oxide layer 330b by the source electrode or the drain electrode. As a result, even when heat treatment is performed, the extraction of oxygen from the oxide layer 330b can be reduced, so the transistor 300 is stable against a high temperature (so-called thermal budget) in the manufacturing process.

[0192] It is preferable to use CAAC-OS as the oxide layer 330c, and it is preferable that the c-axis of the crystal included in the oxide layer 330c faces a direction substantially perpendicular to the formation surface or the upper surface of the oxide layer 330c. CAAC-OS has a property of easily moving oxygen in a direction perpendicular to the c-axis. Therefore, the oxygen included in the oxide layer 330c can be efficiently supplied to the oxide layer 330b.

[0193] The energy levels of the lower conduction band edges of the oxide layer 330a and the oxide layer 330c are preferably higher than the energy level of the lower conduction band edge of the oxide layer 330b. In other words, the electron affinities of the oxide layer 330a and the oxide layer 330c are preferably smaller than the electron affinity of the oxide layer 330b. In this case, it is preferable to use a metal oxide that can be used for the oxide layer 330a for the oxide layer 330c. At this time, the main path of the carriers becomes the oxide layer 330b.

[0194] Here, at the junction of the oxide layer 330a, the oxide layer 330b, and the oxide layer 330c, the energy levels of the lower conduction band edges change smoothly. In other words, the energy levels of the lower conduction band edges at the junction of the oxide layer 330a, the oxide layer 330b, and the oxide layer 330c can also be said to change continuously or be continuously joined. To do this, it is preferable to lower the density of defect levels in the mixed layers formed at the interfaces between the oxide layer 330a and the oxide layer 330b and between the oxide layer 330b and the oxide layer 330c.

[0195] Specifically, by having a common element other than oxygen as the main component in the oxide layer 330a and the oxide layer 330b and the oxide layer 330c, a mixed layer with a low defect level density can be formed. For example, when the oxide layer 330b is an In-Ga-Zn oxide, an In-Ga-Zn oxide, a Ga-Zn oxide, gallium oxide, etc. may be used for the oxide layer 330a and the oxide layer 330c.

[0196] Specifically, as the oxide layer 330a, a metal oxide with an In:Ga:Zn = 1:3:4 [atomic ratio] or 1:1:0.5 [atomic ratio] may be used. Also, as the oxide layer 330b, a metal oxide with an In:Ga:Zn = 1:1:1 [atomic ratio] or In:Ga:Zn = 4:2:3 [atomic ratio] may be used. Also, as the oxide layer 330c, a metal oxide with an In:Ga:Zn = 1:3:4 [atomic ratio], In:Ga:Zn = 4:2:3 [atomic ratio], Ga:Zn = 2:1 [atomic ratio], or Ga:Zn = 2:5 [atomic ratio] may be used.

[0197] In addition, when forming a metal oxide film by sputtering, the above atomic ratio is not limited to the atomic ratio of the formed metal oxide, and may be the atomic ratio of the sputtering target used for forming the metal oxide.

[0198] By configuring the oxide layer 330a and the oxide layer 330c as described above, the density of defect levels at the interface between the oxide layer 330a and the oxide layer 330b and at the interface between the oxide layer 330b and the oxide layer 330c can be reduced. Therefore, the influence on carrier conduction due to interface scattering is reduced, and the transistor 300 can obtain a high on-current and high frequency characteristics.

[0199] The oxide layer 330c may have a laminated structure of two or more layers. For example, the oxide layer 330c may have a first oxide layer and a second oxide on the first oxide layer.

[0200] The first oxide layer of the oxide layer 330c preferably contains at least one of the metal elements constituting the metal oxide used for the oxide layer 330b, and more preferably contains all of the metal elements. For example, an In-Ga-Zn oxide film may be used as the first oxide layer of the oxide layer 330c, and an In-Ga-Zn oxide film, a Ga-Zn oxide film, or a gallium oxide film may be used as the second oxide layer of the oxide layer 330c. Thereby, the density of defect levels at the interface between the oxide layer 330b and the first oxide layer of the oxide layer 330c can be reduced. Further, the second oxide layer of the oxide layer 330c preferably suppresses the diffusion or permeation of oxygen more than the first oxide layer of the oxide layer 330c. By providing the second oxide layer of the oxide layer 330c between the insulating layer 350 and the first oxide layer of the oxide layer 330c, it is possible to suppress the oxygen contained in the insulating layer 380 from diffusing into the insulating layer 350. Therefore, the oxygen is more likely to be supplied to the oxide layer 330b through the first oxide layer of the oxide layer 330c.

[0201] Further, it is preferable that the energy level of the lower end of the conduction band of the second oxide layer of the oxide layer 330a and the oxide layer 330c is higher than the energy level of the lower end of the conduction band of the first oxide layer of the oxide layer 330b and the oxide layer 330c. In other words, it is preferable that the electron affinity of the second oxide layer of the oxide layer 330a and the oxide layer 330c is smaller than the electron affinity of the first oxide layer of the oxide layer 330b and the oxide layer 330c. In this case, it is preferable that the second oxide layer of the oxide layer 330c uses a metal oxide that can be used for the oxide layer 330a, and the first oxide layer of the oxide layer 330c uses a metal oxide that can be used for the oxide layer 330b. At this time, the main path of the carriers may be not only the oxide layer 330b but also the first oxide layer of the oxide layer 330c.

[0202] As the conductive layer 342, the above-mentioned TaN x O y is preferably used. Note that TaN x O y may contain aluminum. Further, for example, titanium nitride, a nitride containing titanium and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, etc. may be used. These materials are preferable because they are conductive materials that are difficult to oxidize or materials that maintain conductivity even when they absorb oxygen.

[0203] As shown in FIG. 8(B), the insulating layer 354 preferably contacts the upper surface and the side surface of the conductive layer 342a, the upper surface and the side surface of the conductive layer 342b, the side surfaces of the oxide layer 330a and the oxide layer 330b, and a part of the upper surface of the insulating layer 324. With such a configuration, the insulating layer 380 is separated from the insulating layer 324, the oxide layer 330a, and the oxide layer 330b by the insulating layer 354.

[0204] Similar to the insulating layer 322, the insulating layer 354 preferably has a function of suppressing the diffusion of one or both of hydrogen and oxygen. For example, the insulating layer 354 preferably has a function of suppressing the diffusion of one or both of hydrogen and oxygen more than the insulating layer 324 and the insulating layer 380. Thereby, it is possible to suppress the hydrogen contained in the insulating layer 380 from diffusing into the oxide layers 330a and 330b. Further, by surrounding the insulating layer 324, the oxide layer 330, etc. with the insulating layer 322 and the insulating layer 354, it is possible to suppress impurities such as water and hydrogen from diffusing into the insulating layer 324 and the oxide layer 330 from the outside. Therefore, good electrical characteristics and reliability can be given to the transistor 300.

[0205] As the insulating layer 354, for example, it is preferable to form an insulating film containing one or both of aluminum oxide and hafnium oxide. In this case, the insulating layer 354 is preferably formed by the atomic layer deposition (ALD) method. Since the ALD method is a film formation method with good coverage, it is possible to prevent steps or the like from being formed due to the unevenness of the insulating layer 354.

[0206] As the insulating layer 354, for example, it is preferable to use an insulating film containing aluminum nitride. Thereby, since a film excellent in insulation and heat conductivity can be obtained, the heat dissipation property of the heat generated when driving the transistor 300 can be enhanced. Also, silicon nitride, silicon oxynitride, etc. can be used.

[0207] As the insulating layer 354, for example, an oxide containing gallium may be used. An oxide containing gallium is preferable because it may have a function of suppressing the diffusion of one or both of hydrogen and oxygen. As the oxide containing gallium, gallium oxide, gallium zinc oxide, indium gallium zinc oxide, etc. can be used. When an indium gallium zinc oxide film is used as the insulating layer 354, it is preferable that the atomic ratio of gallium to indium is larger. By increasing the atomic ratio, the insulation of the oxide film can be enhanced.

[0208] The insulating layer 350 functions as a gate insulating layer. The insulating layer 350 is preferably disposed in contact with the upper surface of the oxide layer 330c. As the material of the insulating layer 350, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with added fluorine, silicon oxide with added carbon, silicon oxide with added carbon and nitrogen, silicon oxide having pores, etc. can be used. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

[0209] The insulating layer 350 is preferably formed using an insulating film that releases oxygen upon heating, similar to the insulating layer 324. By providing, as the insulating layer 350, an insulating film that releases oxygen upon heating in contact with the upper surface of the oxide layer 330c, oxygen can be effectively supplied to the channel formation region of the oxide layer 330b, and oxygen deficiency in the channel formation region of the oxide layer 330b can be reduced. Therefore, it is possible to provide a transistor that suppresses fluctuations in electrical characteristics, has stable electrical characteristics, and has improved reliability. Also, similar to the insulating layer 324, it is preferable that the concentration of impurities such as water and hydrogen in the insulating layer 350 is reduced. The film thickness of the insulating layer 350 is preferably 1 nm or more and 20 nm or less.

[0210] The conductive layer 360 preferably has a conductive layer 360a and a conductive layer 360b on the conductive layer 360a. For example, the conductive layer 360a is preferably disposed so as to surround the bottom surface and the side surface of the conductive layer 360b.

[0211] For the conductive layer 360a, it is preferable to use a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules, and copper atoms. Alternatively, it is preferable to use a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms and oxygen molecules).

[0212] Since the conductive layer 360a has a function of suppressing the diffusion of oxygen, it is possible to suppress the oxidation of the conductive layer 360b by the oxygen contained in the insulating layer 350 and the decrease in conductivity. As the conductive material having the function of suppressing the diffusion of oxygen, for example, tantalum, tantalum nitride, ruthenium, ruthenium oxide, etc. are preferably used.

[0213] Since the conductive layer 360 also functions as a wiring, it is preferable to use a conductive material having high conductivity. For example, as the conductive layer 360b, a conductive material mainly composed of tungsten, copper, or aluminum can be used. Further, the conductive layer 360b may have a laminated structure, for example, a laminated structure of a titanium film, a titanium nitride film, and a film containing the above conductive material.

[0214] In FIG. 8, the conductive layer 360 is shown as a two-layer structure of the conductive layer 360a and the conductive layer 360b, but it may have a single-layer structure or a laminated structure of three or more layers.

[0215] In the transistor 300, the conductive layer 360 is self-alignedly formed so as to fill an opening formed in the insulating layer 380 or the like. By forming the conductive layer 360 in this manner, the conductive layer 360 can be surely disposed in the region between the conductive layer 342a and the conductive layer 342b without alignment.

[0216] As shown in FIG. 8(B), the upper surface of the conductive layer 360 substantially coincides with the upper surface of the insulating layer 350 and the upper surface of the oxide layer 330c.

[0217] As shown in FIG. 8(C), in the channel width direction of the transistor 300, with respect to the bottom surface of the insulating layer 322 as a reference, it is preferable that the height of the bottom surface of the conductive layer 360 in the region where the conductive layer 360 and the oxide layer 330b do not overlap is lower than the height of the bottom surface of the oxide layer 330b. By configuring the conductive layer 360 that functions as a gate electrode to cover the side surface and the upper surface of the channel formation region of the oxide layer 330b via the insulating layer 350 or the like, it becomes easier for the electric field of the conductive layer 360 to act on the entire channel formation region of the oxide layer 330b. Therefore, the on-current of the transistor 300 can be increased and the frequency characteristics can be improved.

[0218] The insulating layer 380 is provided on the insulating layer 324, the oxide layer 330, and the conductive layer 342 via the insulating layer 354. Also, the upper surface of the insulating layer 380 may be planarized.

[0219] The insulating layer 380 that functions as an interlayer film preferably has a low dielectric constant. By using a material with a low dielectric constant for the interlayer film, the parasitic capacitance generated between the wirings can be reduced. The insulating layer 380 is preferably provided using, for example, the same material as the insulating layer 316. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, materials such as silicon oxide, silicon oxynitride, and silicon oxide having pores are preferable because they can easily form regions containing oxygen that desorbs by heating.

[0220] It is preferable that the impurity concentration such as water and hydrogen in the insulating layer 380 is reduced. Also, the insulating layer 380 preferably has a low hydrogen concentration and has an excess oxygen region or excess oxygen, and may be provided using, for example, the same material as the insulating layer 316. Note that the insulating layer 380 may have a laminated structure of two or more layers.

[0221] Similar to the insulating layer 314 and the like, the insulating layer 374 preferably functions as an insulating barrier film that suppresses the diffusion of impurities such as water and hydrogen from above into the insulating layer 380. Also, similar to the insulating layer 314 and the like, the insulating layer 374 preferably has a low hydrogen concentration and has a function of suppressing the diffusion of hydrogen.

[0222] As shown in FIG. 8(B), the insulating layer 374 preferably contacts the upper surfaces of the conductive layer 360, the insulating layer 350, and the oxide layer 330c, respectively. Thereby, impurities such as hydrogen contained in the insulating layer 381 or the like can be suppressed from mixing into the insulating layer 350. Therefore, adverse effects on the electrical characteristics of the transistor and the reliability of the transistor can be suppressed.

[0223] It is preferable to provide an insulating layer 381 that functions as an interlayer film on the insulating layer 374. Similar to the insulating layer 316 or the like, the insulating layer 381 preferably has a low dielectric constant. Further, similar to the insulating layer 324 or the like, the insulating layer 381 preferably has a reduced concentration of impurities such as water and hydrogen in the film.

[0224] The conductive layers 340a and 340b are disposed in the openings formed in the insulating layer 381, the insulating layer 374, the insulating layer 380, and the insulating layer 354. The conductive layers 340a and 340b are provided to face each other with the conductive layer 360 interposed therebetween. Note that the height of the upper surfaces of the conductive layers 340a and 340b may be on the same plane as the upper surface of the insulating layer 381.

[0225] Note that an insulating layer 341a is provided in contact with the sidewalls of the openings in the insulating layer 381, the insulating layer 374, the insulating layer 380, and the insulating layer 354, and the conductive layer 340a is formed in contact with the side surface thereof. The conductive layer 342a is located at at least a part of the bottom of the opening, and the conductive layer 340a is in contact with the conductive layer 342a. Similarly, an insulating layer 341b is provided in contact with the sidewalls of the openings in the insulating layer 381, the insulating layer 374, the insulating layer 380, and the insulating layer 354, and the conductive layer 340b is formed in contact with the side surface thereof. The conductive layer 342b is located at at least a part of the bottom of the opening, and the conductive layer 340b is in contact with the conductive layer 342b.

[0226] It is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum for the conductive layers 340a and 340b.

[0227] The conductive layer 340a and the conductive layer 340b may have a laminated structure. In the transistor 300, the configuration in which the conductive layer 340a and the conductive layer 340b are provided as a two-layer laminated structure is shown, but the present invention is not limited thereto. For example, the conductive layer 340 may be a single layer or a laminated structure of three or more layers.

[0228] As the insulating layer 341a and the insulating layer 341b, for example, an insulating film that can be used for the insulating layer 314, the insulating layer 354, etc. can be used. Since the insulating layer 341a and the insulating layer 341b are provided in contact with the insulating layer 354, it is possible to suppress impurities such as water and hydrogen contained in the insulating layer 380 from diffusing into the oxide layer 330 through the conductive layer 340a and the conductive layer 340b. Also, it is possible to prevent oxygen contained in the insulating layer 380 from being absorbed by the conductive layer 340a and the conductive layer 340b.

[0229] Also, although not shown, a conductive layer that functions as a wiring may be disposed in contact with the upper surfaces of the conductive layer 340a and the conductive layer 340b. It is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum for the conductive layer that functions as a wiring. Further, the conductive layer may have a laminated structure, for example, a laminate of a titanium film, a titanium nitride film, and a film containing the above conductive material. Note that the conductive layer may be formed so as to be embedded in an opening provided in the insulating layer.

[0230] Also, although not shown, so as to cover the above conductive layer, the resistivity is 1.0×10 13 Ωcm or more and 1.0×10 15 Ωcm or less, preferably 5.0×10 13 Ωcm or more and 5.0×10 14 Ωcm or less of an insulating layer is preferably provided. By providing an insulating layer having the above resistivity on the above conductive layer, the insulating layer can disperse the charges accumulated between the wirings such as the transistor 300 and the above conductive layer while maintaining insulation, and can suppress characteristic deterioration and electrostatic breakdown of the transistor and the electronic device having the transistor caused by the charges, which is preferable.

[0231] As described above, since the display device according to the present embodiment can bond a plurality of light-emitting diodes and a plurality of transistors at once, it is possible to reduce the manufacturing cost of the display device and improve the yield. Further, by combining a micro LED and a transistor using a metal oxide, a display device with reduced power consumption can be realized.

[0232] Further, since the display device according to the present embodiment can reduce the size of the transistor, it is easy to increase the fineness and apply it to an electronic device having a relatively small display unit.

[0233] The present embodiment can be appropriately combined with other embodiments. Further, in this specification, when a plurality of configuration examples are shown in one embodiment, the configuration examples can be appropriately combined.

[0234] (Embodiment 2) In the present embodiment, the pixel of the display device according to one aspect of the present invention will be described with reference to FIG. 10.

[0235] [Pixel] The display device according to the present embodiment has a plurality of pixels arranged in a matrix of m rows and n columns (m and n are integers of 1 or more). FIG. 10 shows an example of a circuit diagram of a pixel 200(i, j) (i is an integer of 1 or more and m or less, and j is an integer of 1 or more and n or less).

[0236] The pixel 200(i, j) shown in FIG. 10 has a light-emitting element 210, a switch SW21, a switch SW22, a transistor M, and a capacitive element C1.

[0237] In the present embodiment, an example in which a transistor is used as the switch SW21 is shown. The gate of the switch SW21 is electrically connected to the scanning line GL1(i). One of the source and drain of the switch SW21 is electrically connected to the signal line SL(j), and the other is electrically connected to the gate of the transistor M.

[0238] In this embodiment, an example of using a transistor as the switch SW22 is shown. The gate of the switch SW22 is electrically connected to the scanning line GL2(i). One of the source and drain of the switch SW22 is electrically connected to the wiring COM, and the other is electrically connected to the gate of the transistor M.

[0239] The gate of the transistor M is electrically connected to one electrode of the capacitive element C1, the other of the source and drain of the switch SW21, and the other of the source and drain of the switch SW22. One of the source and drain of the transistor M is electrically connected to the wiring CATHODE, and the other is electrically connected to the cathode of the light-emitting element 210.

[0240] The other electrode of the capacitive element C1 is electrically connected to the wiring CATHODE.

[0241] The anode of the light-emitting element 210 is electrically connected to the wiring ANODE.

[0242] The scanning line GL1(i) has a function of supplying a selection signal. The scanning line GL2(i) has a function of supplying a control signal. The signal line SL(j) has a function of supplying an image signal. Constant potentials are supplied to the wiring VCOM, the wiring CATHODE, and the wiring ANODE, respectively. The anode side of the light-emitting element 210 can be set to a high potential, and the cathode side can be set to a potential lower than the anode side.

[0243] The switch SW21 is controlled by a selection signal and functions as a selection transistor for controlling the selection state of the pixel 200.

[0244] The transistor M functions as a driving transistor for controlling the current flowing through the light-emitting element 210 according to the potential supplied to the gate. When the switch SW21 is in the conductive state, the image signal supplied to the signal line SL(j) is supplied to the gate of the transistor M, and the emission luminance of the light-emitting element 210 can be controlled according to the potential.

[0245] Switch SW22 has a function of controlling the gate potential of transistor M based on a control signal. Specifically, switch SW22 can supply a potential that turns transistor M off to the gate of transistor M.

[0246] Switch SW22 can be used, for example, for pulse width control. During a period based on a control signal, current can be supplied from transistor M to light-emitting element 210. Alternatively, light-emitting element 210 can express gradation based on an image signal and a control signal.

[0247] Here, it is preferable to apply a transistor using a metal oxide (oxide semiconductor) to the semiconductor layer in which channels are respectively formed for the transistors included in pixel 200(i,j).

[0248] A transistor using a metal oxide having a wider bandgap and a smaller carrier density than silicon can achieve an extremely small off-current. Therefore, due to its small off-current, it is possible to hold the charge accumulated in the capacitive element connected in series with the transistor for a long period of time. Therefore, it is particularly preferable to use a transistor in which an oxide semiconductor is applied for switches SW21 and SW22 connected in series to capacitive element C1. Also, by using transistors in which an oxide semiconductor is applied in the same manner for other transistors, the manufacturing cost can be reduced.

[0249] Also, a transistor using silicon as the semiconductor in which channels are formed can be used for the transistors included in pixel 200(i,j). In particular, by using highly crystalline silicon such as single-crystalline silicon or polycrystalline silicon, high field-effect mobility can be achieved, and faster operation becomes possible, which is preferable.

[0250] Also, among the transistors included in pixel 200(i,j), a configuration may be adopted in which transistors using an oxide semiconductor are used for one or more of them, and transistors using silicon are used for the others.

[0251] In FIG. 10, the transistor is depicted as an n-channel type transistor, but a p-channel type transistor can also be used.

[0252] [Transistor] Next, the transistor that can be used in the display device will be described.

[0253] The structure of the transistor included in the display device is not particularly limited. For example, it may be a planar type transistor, a staggered type transistor, or an inverse staggered type transistor. Also, it may be either a top gate structure or a bottom gate structure transistor. Alternatively, gate electrodes may be provided above and below the channel.

[0254] For the transistor included in the display device, for example, a transistor using a metal oxide in the channel formation region can be used. Thereby, a transistor with an extremely small off-current can be realized.

[0255] Alternatively, a transistor having silicon in the channel formation region may be applied to the transistor included in the display device. Examples of such a transistor include a transistor having amorphous silicon, a transistor having crystalline silicon (typically, low-temperature polysilicon), and a transistor having single-crystalline silicon.

[0256] [Metal oxide] Hereinafter, the metal oxide applicable to the semiconductor layer of the transistor will be described.

[0257] In this specification and the like, a metal oxide having nitrogen may also be collectively referred to as a metal oxide. Also, a metal oxide having nitrogen may be referred to as a metal oxynitride. For example, a metal oxide having nitrogen such as zinc oxynitride (ZnON) may be used for the semiconductor layer.

[0258] In addition, in this specification and the like, CAAC (c-axis aligned crystal) and CAC (Cloud-Aligned Composite) may be described. CAAC represents an example of a crystal structure, and CAC represents an example of the configuration of a function or material.

[0259] For example, CAC (Cloud-Aligned Composite)-OS can be used for the semiconductor layer.

[0260] CAC-OS or CAC-metal oxide has a conductive function in part of the material and an insulating function in part of the material, and has a semiconductor function as a whole for the entire material. When CAC-OS or CAC-metal oxide is used for the semiconductor layer of a transistor, the conductive function is the function of flowing electrons (or holes) serving as carriers, and the insulating function is the function of not flowing electrons serving as carriers. By causing the conductive function and the insulating function to act complementarily, respectively, a switching function (On / Off function) can be imparted to CAC-OS or CAC-metal oxide. In CAC-OS or CAC-metal oxide, by separating the respective functions, both functions can be enhanced to the maximum extent.

[0261] In addition, CAC-OS or CAC-metal oxide has a conductive region and an insulating region. The conductive region has the above-described conductive function, and the insulating region has the above-described insulating function. Also, in the material, the conductive region and the insulating region may be separated at the nanoparticle level. Also, the conductive region and the insulating region may be unevenly distributed in the material, respectively. Also, the conductive region may be observed to be blurred at the periphery and connected in a cloud shape.

[0262] In addition, in CAC-OS or CAC-metal oxide, the conductive regions and the insulating regions may be dispersed in the material with sizes of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less, respectively.

[0263] In addition, CAC-OS or CAC-metal oxide is composed of components having different band gaps. For example, CAC-OS or CAC-metal oxide is composed of a component having a wide band gap due to the insulating region and a component having a narrow band gap due to the conductive region. In such a configuration, when carriers flow, the carriers mainly flow in the component having the narrow band gap. In addition, the component having the narrow band gap acts complementarily to the component having the wide band gap, and carriers also flow in the component having the wide band gap in conjunction with the component having the narrow band gap. Therefore, when the above CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, a high current driving force, that is, a large on-current, and a high field-effect mobility can be obtained in the on-state of the transistor.

[0264] That is, CAC-OS or CAC-metal oxide can also be referred to as a matrix composite or a metal matrix composite.

[0265] Oxide semiconductors (metal oxides) can be divided into single-crystalline oxide semiconductors and other non-single-crystalline oxide semiconductors. Examples of non-single-crystalline oxide semiconductors include CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductors, nc-OS (nanocrystalline oxide semiconductor), pseudo-amorphous oxide semiconductors (a-like OS: amorphous-like oxide semiconductor), and amorphous oxide semiconductors.

[0266] CAAC-OS has a c-axis orientation, and in the a-b plane direction, a plurality of nanocrystals are connected to form a crystal structure with strain. Note that the strain refers to a location where the orientation of the lattice arrangement changes between a region where the lattice arrangement is aligned and another region where the lattice arrangement is aligned in the region where the plurality of nanocrystals are connected.

[0267] The nanocrystals are based on a hexagon, but are not necessarily regular hexagons and may be non-regular hexagons. Also, in the strain, there may be lattice arrangements such as pentagons and heptagons. Note that in CAAC-OS, it is difficult to confirm a distinct grain boundary (also referred to as a grain boundary) even in the vicinity of the strain. That is, it can be seen that the formation of grain boundaries is suppressed by the strain of the lattice arrangement. This is because CAAC-OS can tolerate strain due to the fact that the arrangement of oxygen atoms is not dense in the a-b plane direction and the interatomic bond distance changes due to the substitution of metal elements.

[0268] Also, CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter, In layer) and a layer containing element M, zinc, and oxygen (hereinafter, (M,Zn) layer) are laminated. Note that indium and element M are mutually substitutable, and when element M in the (M,Zn) layer is substituted with indium, it can also be represented as an (In,M,Zn) layer. Also, when indium in the In layer is substituted with element M, it can also be represented as an (In,M) layer.

[0269] CAAC-OS is a highly crystalline metal oxide. On the other hand, since it is difficult to confirm a distinct grain boundary in CAAC-OS, it can be said that a decrease in electron mobility due to grain boundaries is unlikely to occur. Also, since the crystallinity of metal oxides may decrease due to the incorporation of impurities or the generation of defects, CAAC-OS has impurities and defects (oxygen vacancies (V O(Also referred to as oxygen vacancy.) It can also be said to be a metal oxide with few (such as...) Therefore, the metal oxide having CAAC-OS has stable physical properties. Therefore, the metal oxide having CAAC-OS is heat-resistant and highly reliable.

[0270] nc-OS has periodicity in the atomic arrangement in a minute region (for example, a region of 1 nm or more and 10 nm or less, particularly a region of 1 nm or more and 3 nm or less). Also, nc-OS has no regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is observed in the whole film. Therefore, depending on the analysis method, nc-OS may not be distinguishable from a-like OS or an amorphous oxide semiconductor.

[0271] Note that indium-gallium-zinc oxide (hereinafter, IGZO), which is a kind of metal oxide having indium, gallium, and zinc, may take a stable structure by using the above-described nanocrystals. In particular, since IGZO has a tendency that crystal growth is difficult in the air, it may be structurally more stable as a smaller crystal (for example, the above-described nanocrystal) than a large crystal (here, a crystal of several mm or a crystal of several cm).

[0272] a-like OS is a metal oxide having a structure between nc-OS and an amorphous oxide semiconductor. a-like OS has a loose or low-density region. That is, a-like OS has lower crystallinity than nc-OS and CAAC-OS.

[0273] The oxide semiconductor (metal oxide) has various structures and each has different characteristics. The oxide semiconductor according to one aspect of the present invention may have two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, a-like OS, nc-OS, and CAAC-OS.

[0274] The metal oxide film functioning as a semiconductor layer can be formed using either or both of an inert gas and an oxygen gas. Note that there is no particular limitation on the flow rate ratio (oxygen partial pressure) of oxygen during the formation of the metal oxide film. However, when obtaining a transistor with high field-effect mobility, the flow rate ratio (oxygen partial pressure) of oxygen during the formation of the metal oxide film is preferably 0% or more and 30% or less, more preferably 5% or more and 30% or less, and even more preferably 7% or more and 15% or less.

[0275] This embodiment can be appropriately combined with other embodiments.

[0276] (Embodiment 3) In this embodiment, an electronic device according to one aspect of the present invention will be described with reference to FIGS. 11 to 15.

[0277] The electronic device of this embodiment has a display device according to one aspect of the present invention in the display unit. The display device according to one aspect of the present invention has high display quality and low power consumption. In addition, the display device according to one aspect of the present invention is easily capable of high definition and large size. Therefore, it can be used for the display units of various electronic devices.

[0278] Examples of the electronic device include, in addition to electronic devices having a relatively large screen such as a television device, a desktop or notebook personal computer, a monitor for a computer, digital signage, and a large game machine such as a pachinko machine, a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game machine, a portable information terminal, and an audio playback device.

[0279] In particular, since the display device according to one aspect of the present invention can enhance the fineness, it can be suitably used for an electronic device having a relatively small display unit. Examples of such an electronic device include a wristwatch-type or bracelet-type information terminal device (wearable device), a VR device such as a head-mounted display, a glasses-type AR device, or an MR device, and can be suitably used for wearable devices that can be worn on the head.

[0280] The electronic device of this embodiment may have a sensor (including a function of measuring force, displacement, position, velocity, acceleration, angular velocity, rotational 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).

[0281] The electronic device of this embodiment can have various functions. For example, it can have functions such as displaying various information (such as still images, moving images, text images, etc.) on a display unit, a touch panel function, a function of displaying a calendar, date, or time, a function of executing various software (programs), a wireless communication function, and a function of reading programs or data recorded on a recording medium.

[0282] FIG. 11(A) shows a perspective view of the glasses-type electronic device 900. The electronic device 900 has a pair of display panels 901, a pair of housings 902, a pair of optical members 903, a pair of mounting parts 904, etc.

[0283] The electronic device 900 can project the image displayed on the display panel 901 onto the display area 906 of the optical member 903. Since the optical member 903 has translucency, the user can see the image displayed in the display area 906 by overlapping it with the transmitted image visible through the optical member 903. Therefore, the electronic device 900 is an electronic device capable of AR display.

[0284] Preferably, in addition to the function of displaying an image, the display panel 901 included in the electronic device 900 has a function of imaging. At this time, the electronic device 900 can receive the light incident on the display panel 901 through the optical member 903, convert it into an electrical signal, and output it. Thereby, it is possible to image the user's eyes or the eyes and their surroundings and output them as image information to the outside or to an arithmetic unit included in the electronic device 900.

[0285] One housing 902 is provided with a camera 905 capable of imaging the front. Although not shown, one of the housings 902 is provided with a wireless receiver or a connector to which a cable can be connected, and a video signal or the like can be supplied to the housing 902. Further, by arranging an acceleration sensor such as a gyro sensor in the housing 902, the orientation of the user's head can be detected, and an image corresponding to the orientation can be displayed on the display area 906. Further, it is preferable that the housing 902 is provided with a battery, and it is preferable that the battery can be charged wirelessly or by wire.

[0286] Using FIG. 11(B), the method of projecting an image onto the display area 906 of the electronic device 900 will be described. Inside the housing 902, a display panel 901, a lens 911, and a reflector 912 are provided. Further, a portion of the optical member 903 corresponding to the display area 906 has a reflecting surface 913 that functions as a half mirror.

[0287] The light 915 emitted from the display panel 901 passes through the lens 911 and is reflected by the reflector 912 toward the optical member 903 side. Inside the optical member 903, the light 915 repeatedly undergoes total reflection at the end face of the optical member 903 and reaches the reflecting surface 913, where an image is projected onto the reflecting surface 913. As a result, the user can visually recognize both the light 915 reflected by the reflecting surface 913 and the transmitted light 916 transmitted through the optical member 903 (including the reflecting surface 913).

[0288] FIG. 11 shows an example in which the reflector 912 and the reflecting surface 913 each have a curved surface. This can increase the degree of freedom in optical design and reduce the thickness of the optical member 903 compared to the case where they are flat. Note that the reflector 912 and the reflecting surface 913 may be flat.

[0289] As the reflector 912, a member having a mirror surface can be used, and it is preferable that the reflectance is high. Further, as the reflecting surface 913, a half mirror using the reflection of a metal film may be used, but using a prism or the like that uses total reflection can increase the transmittance of the transmitted light 916.

[0290] Here, it is preferable that the electronic device 900 has a mechanism for adjusting one or both of the distance and the angle between the lens 911 and the display panel 901. Thereby, it becomes possible to perform focusing adjustment, image enlargement, reduction, and the like. For example, one or both of the lens 911 and the display panel 901 may be configured to be movable in the optical axis direction.

[0291] It is preferable that the electronic device 900 has a mechanism for adjusting the angle of the reflector 912. By changing the angle of the reflector 912, it becomes possible to change the position of the display area 906 where the image is displayed. Thereby, it becomes possible to arrange the display area 906 at an optimal position according to the position of the user's eyes.

[0292] The display device according to one aspect of the present invention can be applied to the display panel 901. Therefore, the electronic device 900 can have extremely high definition display.

[0293] 12(A) and FIG. 12(B) show perspective views of the goggle-type electronic device 950. FIG. 12(A) is a perspective view showing the front, plane, and left side of the electronic device 950, and FIG. 12(B) is a perspective view showing the back, bottom, and right side of the electronic device 950.

[0294] The electronic device 950 includes a pair of display panels 951, a housing 952, a pair of mounting portions 954, a buffer member 955, a pair of lenses 956, and the like. The pair of display panels 951 are respectively provided at positions inside the housing 952 where they can be visually recognized through the lenses 956.

[0295] The electronic device 950 is an electronic device for VR. A user wearing the electronic device 950 can visually recognize an image displayed on the display panel 951 through the lens 956. Also, by displaying different images on the pair of display panels 951, three-dimensional display using parallax can be performed.

[0296] On the back side of the housing 952, an input terminal 957 and an output terminal 958 are provided. A cable for supplying a video signal from a video output device or the like, or power for charging a battery provided in the housing 952 can be connected to the input terminal 957. The output terminal 958 can function as, for example, an audio output terminal, and earphones, headphones, or the like can be connected thereto. Note that when the configuration is such that audio data can be output by wireless communication or when audio is output from an external video output device, the audio output terminal may not be provided.

[0297] The electronic device 900 preferably has a mechanism capable of adjusting the left and right positions of the lens 956 and the display panel 951 so that they are in optimal positions according to the position of the user's eyes. Further, it preferably has a mechanism for adjusting focus by changing the distance between the lens 956 and the display panel 951.

[0298] The display device according to one aspect of the present invention can be applied to the display panel 951. Thus, the electronic device 950 can be made to have extremely high definition display. Thereby, a high sense of immersion can be given to the user.

[0299] The buffer member 955 is a portion that contacts the user's face (such as the forehead and cheeks). By the buffer member 955 being in close contact with the user's face, light leakage can be prevented and the sense of immersion can be further enhanced. It is preferable to use a soft material for the buffer member 955 so that it closely adheres to the user's face when the user wears the electronic device 950. For example, materials such as rubber, silicone rubber, urethane, and sponge can be used. Also, as the buffer member 955, using a sponge or the like with its surface covered with cloth or leather (natural leather or synthetic leather) can suitably prevent light leakage because a gap is less likely to occur between the user's face and the buffer member 955. It is preferable that members such as the buffer member 955 and the mounting portion 954 that touch the user's skin are configured to be removable because cleaning and replacement become easy.

[0300] The electronic device 6500 shown in FIG. 13(A) is a portable information terminal that can be used as a smartphone.

[0301] The electronic device 6500 includes a housing 6501, a display unit 6502, a power button 6503, a button 6504, a speaker 6505, a microphone 6506, a camera 6507, a light source 6508, etc. The display unit 6502 has a touch panel function.

[0302] The display device according to an aspect of the present invention can be applied to the display unit 6502.

[0303] FIG. 13(B) is a schematic cross-sectional view including the end portion on the microphone 6506 side of the housing 6501.

[0304] A protective member 6510 having translucency is provided on the display surface side of the housing 6501, and a display panel 6511, an optical member 6512, a touch sensor panel 6513, a printed circuit board 6517, a battery 6518, etc. are arranged in the space surrounded by the housing 6501 and the protective member 6510.

[0305] The display panel 6511, the optical member 6512, and the touch sensor panel 6513 are fixed to the protective member 6510 by an adhesive layer (not shown).

[0306] In a region outside the display unit 6502, a part of the display panel 6511 is folded back, and an FPC 6515 is connected to the folded-back portion. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to a terminal provided on the printed circuit board 6517.

[0307] The display panel 6511 can be applied with the flexible display of one aspect of the present invention. Therefore, an extremely lightweight electronic device can be realized. Further, since the display panel 6511 is extremely thin, a large-capacity battery 6518 can be mounted while suppressing the thickness of the electronic device. Further, by folding back a part of the display panel 6511 and arranging a connection portion with the FPC 6515 on the back side of the pixel portion, a narrow bezel electronic device can be realized.

[0308] FIG. 14(A) shows an example of a television device. In the television device 7100, a display unit 7000 is incorporated in a housing 7101. Here, a configuration in which the housing 7101 is supported by a stand 7103 is shown.

[0309] The display device of one aspect of the present invention can be applied to the display unit 7000.

[0310] The operation of the television device 7100 shown in FIG. 14(A) can be performed by an operation switch provided in the housing 7101 or a separate remote control operation unit 7111. Alternatively, the display unit 7000 may be provided with a touch sensor, and the television device 7100 may be operated by touching the display unit 7000 with a finger or the like. The remote control operation unit 7111 may have a display unit that displays information output from the remote control operation unit 7111. Channel and volume operations can be performed by operation keys or a touch panel provided in the remote control operation unit 7111, and the video displayed on the display unit 7000 can be operated.

[0311] Note that the television device 7100 has a configuration including a receiver and a modem. General television broadcasts can be received by the receiver. Further, by connecting to a communication network by wire or wirelessly via the modem, one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers) information communication is also possible.

[0312] FIG. 14(B) shows an example of a notebook personal computer. The notebook personal computer 7200 has a housing 7211, a keyboard 7212, a pointing device 7213, an external connection port 7214, etc. A display unit 7000 is incorporated in the housing 7211.

[0313] The display device according to one aspect of the present invention can be applied to the display unit 7000.

[0314] FIGS. 14(C) and 14(D) show an example of digital signage.

[0315] The digital signage 7300 shown in FIG. 14(C) has a housing 7301, a display unit 7000, a speaker 7303, etc. Furthermore, it can have an LED lamp, operation keys (including a power switch or an operation switch), connection terminals, various sensors, a microphone, etc.

[0316] FIG. 14(D) shows a digital signage 7400 attached to a columnar pillar 7401. The digital signage 7400 has a display unit 7000 provided along the curved surface of the pillar 7401.

[0317] In FIGS. 14(C) and 14(D), the display device according to one aspect of the present invention can be applied to the display unit 7000.

[0318] The larger the display unit 7000 is, the more information can be provided at one time. Also, the larger the display unit 7000 is, the easier it is to catch people's eyes, and for example, the advertising effect can be enhanced.

[0319] By applying a touch panel to the display unit 7000, not only can an image or video be displayed on the display unit 7000, but also the user can operate it intuitively, which is preferable. Also, when used for applications such as providing route information or traffic information, the usability can be improved by intuitive operation.

[0320] Also, as shown in FIGS. 14(C) and 14(D), it is preferable that the digital signage 7300 or the digital signage 7400 can be linked with an information terminal 7311 such as a smartphone held by a user or the information terminal 7411 through wireless communication. For example, the information of the advertisement displayed on the display unit 7000 can be displayed on the screen of the information terminal 7311 or the information terminal 7411. Further, by operating the information terminal 7311 or the information terminal 7411, the display on the display unit 7000 can be switched.

[0321] Also, a game can be executed on the digital signage 7300 or the digital signage 7400 with the screen of the information terminal 7311 or the information terminal 7411 as an operation means (controller). As a result, an unspecified number of users can participate in the game and enjoy it at the same time.

[0322] The electronic device shown in FIGS. 15(A) to 15(F) includes a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), connection terminals 9006, a sensor 9007 (including a function of 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.

[0323] The electronic devices shown in FIGS. 15(A) to 15(F) have various functions. For example, they can have functions such as displaying various information (still images, moving images, text images, etc.) on a display unit, a touch panel function, a function of displaying a calendar, date, or time, a function of controlling processing by various software (programs), a wireless communication function, a function of reading and processing programs or data recorded on a recording medium, etc. Note that the functions of the electronic device are not limited to these, and it can have various functions. The electronic device may have a plurality of display units. Also, the electronic device may be provided with a camera or the like, and have functions such as taking still images or moving images and storing them in a recording medium (external or built into the camera), and displaying the taken images on the display unit, etc.

[0324] Details of the electronic devices shown in FIGS. 15(A) to 15(F) will be described below.

[0325] FIG. 15(A) is a perspective view showing a portable information terminal 9101. The portable information terminal 9101 can be used, for example, as a smartphone. Note that the portable information terminal 9101 may be provided with a speaker 9003, connection terminals 9006, a sensor 9007, etc. Also, the portable information terminal 9101 can display character and image information on its plurality of surfaces. FIG. 15(A) shows an example in which three icons 9050 are displayed. Also, information 9051 indicated by a dashed rectangle can be displayed on other surfaces of the display unit 9001. Examples of the information 9051 include notifications of incoming calls such as e-mail, SNS, and phone calls, titles of e-mail and SNS, sender names, dates, times, remaining battery levels, antenna reception strengths, etc. Alternatively, icons 9050 or the like may be displayed at the position where the information 9051 is displayed.

[0326] FIG. 15(B) is a perspective view showing a portable information terminal 9102. The portable information terminal 9102 has a function of displaying information on three or more sides of a display unit 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different surfaces. For example, the user can also check the information 9053 displayed at a position where it can be observed from above the portable information terminal 9102 while the portable information terminal 9102 is stored in the breast pocket of the clothing. The user can check the display without taking the portable information terminal 9102 out of the pocket and can determine, for example, whether to answer a call.

[0327] FIG. 15(C) is a perspective view showing a wristwatch-type portable information terminal 9200. The portable information terminal 9200 can be used, for example, as a smartwatch. Further, the display surface of the display unit 9001 is provided in a curved shape, and display can be performed along the curved display surface. Further, the portable information terminal 9200 can also make a hands-free call by mutually communicating with, for example, a wirelessly communicable headset. Further, the portable information terminal 9200 can also perform data transmission and charging mutually with other information terminals through a connection terminal 9006. Note that the charging operation may be performed by wireless power supply.

[0328] FIGS. 15(D) to 15(F) are perspective views showing a foldable portable information terminal 9201. Further, FIG. 15(D) shows a state where the portable information terminal 9201 is unfolded, FIG. 15(F) shows a folded state, and FIG. 15(E) is a perspective view of a state in the middle of changing from one of FIGS. 15(D) and 15(F) to the other. The portable information terminal 9201 has excellent portability in the folded state and excellent display listability due to a seamless wide display area in the unfolded state. The display unit 9001 included in the portable information terminal 9201 is supported by three housings 9000 connected by a hinge 9055. For example, the display unit 9001 can be bent with a curvature radius of 0.1 mm or more and 150 mm or less.

[0329] This embodiment can be appropriately combined with other embodiments and examples.

Explanation of Signs

[0330] C1: Capacitance element, GL1: Scanning line, GL2: Scanning line, SW21: Switch, SW22: Switch, 100A: Display device, 100B: Display device, 100C: Display device, 100D: Display device, 100E: Display device, 100F: Display device, 101: Substrate, 102: Protective layer, 110a: Light-emitting diode, 110b: Light-emitting diode, 112a: Electrode, 112b: Electrode, 113a: Semiconductor layer, 113b: Semiconductor layer, 114a: Light-emitting layer, 114b: Light-emitting layer, 115a: Semiconductor layer, 115b: Semiconductor layer, 116a: Electrode, 116b: Electrode, 117a: Conductor, 117b: Conductor, 117c: Conductor, 117d: Conductor, 120a: Transistor, 120b: Transistor, 130a: Transistor, 130b: Transistor, 131: Substrate, 132: Element isolation layer, 133: Low-resistance region, 134: Insulating layer, 135: Conductive layer, 136: Insulating layer, 137: Conductive layer, 138: Conductive layer, 139: Insulating layer, 141: Insulating layer, 142: Conductive layer, 143: Insulating layer, 150A: LED substrate, 150B: Circuit board, 151: Substrate, 152: Insulating layer, 161: Conductive layer, 162: Insulating layer, 163: Insulating layer, 164: Insulating layer, 165: Metal oxide layer, 166: Conductive layer, 167: Insulating layer, 168: Conductive layer, 171: Substrate, 172: Wiring, 173: Insulating layer, 174: Electrode, 175: Conductive layer, 176: Connector, 177: Electrode, 178: Electrode, 179: Adhesive layer, 181: Insulating layer, 182: Insulating layer, 183: Insulating layer, 184a: Conductive layer, 184b: Conductive layer, 185: Insulating layer, 186: Insulating layer, 187: Conductive layer, 187a: Conductive layer, 187b: Conductive layer, 188: Insulating layer, 189: Conductive layer, 189a: Conductive layer, 189b: Conductive layer, 190a: Conductive layer, 190b: Conductive layer, 190c: Conductive layer, 190d: Conductive layer, 190e: Conductive layer, 191: Substrate, 192: Adhesive layer, 195: Conductor, 200: Pixel, 210: Light-emitting element, 300: Transistor, 300A: Transistor, 305: Conductive layer, 314: Insulating layer, 316: Insulating layer, 322: Insulating layer, 324: Insulating layer, 330: Oxide layer, 330a: Oxide layer, 330b: Oxide layer, 330c: Oxide layer, 340: Conductive layer, 340a: Conductive layer, 340b: Conductive layer, 341: Insulating layer, 341a: Insulating layer, 341b: Insulating layer, 342: Conductive layer, 342a: Conductive layer, 342b: Conductive layer, 350: Insulating layer, 354: Insulating layer, 360: Conductive layer360a: Conductive layer, 360b: Conductive layer, 374: Insulating layer, 380: Insulating layer, 381: Insulating layer, 900: Electronic device, 901: Display panel, 902: Housing, 903: Optical member, 904: Mounting portion, 905: Camera, 906: Display area, 911: Lens, 912: Reflector, 913: Reflective surface, 915: Light, 916: Transmitted light, 950: Electronic device, 951: Display panel, 952: Housing, 954: Mounting portion, 955: Buffer member, 956: Lens, 957: Input terminal, 958: Output terminal, 6500: Electronic device, 6501: Housing, 6502: Display unit, 6503: Power button, 6504: Button, 6505: Speaker, 6506: Microphone, 6507: Camera, 6508: Light source, 6510: Protection member, 6511: Display panel, 6512: Optical member, 6513: Touch sensor panel, 6515: FPC, 6516: IC, 6517: Printed circuit board, 6518: Battery, 7000: Display unit, 7100: Television device, 7101: Housing, 7103: Stand, 7111: Remote control unit, 7200: Notebook personal computer, 7211: Housing, 7212: Keyboard, 7213: Pointing device, 7214: External connection port, 7300: Digital signage, 7301: Housing, 7303: Speaker, 7311: Information terminal device, 7400: Digital signage, 7401: Column, 7411: Information terminal device, 9000: Housing, 9001: Display unit, 9003: Speaker, 9005: Operation key, 9006: Connection terminal, 9007: Sensor, 9008: Microphone, 9050: Icon, 9051: Information, 9052: Information, 9053: Information, 9054: Information, 9055: Hinge, 9101: Portable information terminal, 9102: Portable information terminal, 9200: Portable information terminal, 9201: Portable information terminal,

Claims

1. A display device in which a first substrate on which a first transistor, a second transistor, first to fifth insulating layers, a first conductive layer, and a second conductive layer are provided, and a second substrate on which a plurality of light-emitting diodes are provided in a matrix are bonded together, the first transistor has a channel formation region containing silicon above the first substrate; the second transistor is provided above the first transistor via the first insulating layer and is electrically connected to at least one of the plurality of light emitting diodes; the second transistor includes a first gate electrode above the first insulating layer, a metal oxide layer provided above the first gate electrode and having a channel formation region, and a second gate electrode above the metal oxide layer; The metal oxide layer contains In, Ga, and Zn. the first gate electrode is provided so as to be embedded in the second insulating layer, and a height of an upper surface of the first gate electrode is approximately equal to a height of an upper surface of the second insulating layer; the second gate electrode has a region provided so as to be embedded in the third insulating layer, and a height of an upper surface of the second gate electrode is approximately equal to a height of an upper surface of the third insulating layer; the fourth insulating layer has a region in contact with an upper surface of the second gate electrode and a region in contact with an upper surface of the third insulating layer, the fifth insulating layer is provided above the fourth insulating layer, each of the first conductive layer and the second conductive layer has a region in contact with an upper surface of the fifth insulating layer; a pixel electrode of each of the plurality of light emitting diodes is electrically connected to the first conductive layer through a first conductive paste; the first conductive layer is electrically connected to the second transistor; a common electrode of the plurality of light emitting diodes is electrically connected to the second conductive layer via a second conductive paste; a width of the first conductive layer is larger than a width of a pixel electrode of the plurality of light-emitting diodes, and a width of the second conductive layer is larger than a width of a common electrode of the plurality of light-emitting diodes, in a cross-sectional view in a channel length direction of the second transistor.

2. In claim 1, The display device, wherein each of the plurality of light emitting diodes has a light emitting region having an area of ​​10000 μm 2 or less.

3. In claim 1 or 2, At least one of the plurality of light emitting diodes is a micro light emitting diode.

4. In any one of claims 1 to 3, the plurality of light emitting diodes includes a first light emitting diode and a second light emitting diode; The display device, wherein the first light emitting diode and the second light emitting diode emit lights of different colors.

5. In any one of claims 1 to 3, A display device, wherein the plurality of light emitting diodes all emit light of the same color.

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