Light-emitting element, display device, and electronic device

Abstract

A novel light-emitting element is provided. Specifically provided is a light-emitting element comprising a positive electrode, an electroluminescent layer on the positive electrode, and a negative electrode on the electroluminescent layer, wherein a first layer is adjacent to a side surface of the electroluminescent layer, and a first region is adjacent to a side surface of the first layer. The electroluminescent layer and the first region are adjacent with the first layer therebetween. The refraction index of the first region is lower than the refraction index of the first layer. The angle θ formed by the bottom surface and the side surface of the electroluminescent layer is greater than 90°.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a light-emitting element, a display device, and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof. [Background technology]

[0003] Known display devices include active matrix display devices having transistors for driving display elements in each pixel, such as active matrix liquid crystal display devices (also called "liquid crystal displays") that use liquid crystal elements as display elements, and active matrix light emitting display devices (also called "organic EL displays") that use light emitting elements such as organic EL elements as display elements.

[0004] Organic EL displays are self-luminous display devices, and therefore have a wider viewing angle and higher responsiveness than liquid crystal displays. In addition, organic EL displays do not require a backlight, making it easier to realize lighter, thinner, and less power-consuming display devices, and have been the subject of active research in recent years. Organic EL elements that function as pixels have a configuration in which an anode and a cathode overlap with an emitting layer interposed between them. In addition, in organic EL displays, a partition is provided between adjacent pixels to prevent electrical interference between adjacent emitting layers (Patent Document 1).

[0005] Furthermore, when an organic EL layer such as a light-emitting layer is formed from a low-molecular-weight material, a method of performing the method by vacuum deposition using a metal mask is known (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-123527 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-157973 Summary of the Invention [Problem to be solved by the invention]

[0007] Partition walls (also called "embankments" or "banks") provided between pixels have the effect of improving the display quality of display devices and reducing power consumption. However, a certain amount of partition wall is required to achieve sufficient effects, making it difficult to reduce the area occupied by the partition wall, and thus making it difficult to improve pixel aperture ratio, achieve higher definition, and reduce the size of the display.

[0008] Furthermore, because metal masks have lower dimensional accuracy than resist masks, it has been difficult to improve the pixel aperture ratio and achieve high definition when forming the light-emitting layer for each pixel using a metal mask. Another problem with metal masks is that they are easily deformed by the heat generated in the evaporation source.

[0009] An object of one embodiment of the present invention is to provide a display device, a semiconductor device, or the like with high display quality.Another object is to provide a highly reliable display device, a semiconductor device, or the like.Another object is to provide a display device, a semiconductor device, or the like with low power consumption.Another object is to provide a lightweight display device, a semiconductor device, or the like.Another object is to provide a display device, a semiconductor device, or the like with high productivity.Another object is to provide a novel display device, a semiconductor device, or the like.

[0010] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these will become apparent from the description of the specification, drawings, claims, etc., and it is possible to extract other problems from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0011] One embodiment of the present invention is a light-emitting element having an anode, an EL layer on the anode, and a cathode on the EL layer, a first layer adjacent to a side surface of the EL layer, and a first portion adjacent to the side surface of the EL layer via the first layer, wherein the angle θ between the bottom surface and the side surface of the EL layer is greater than 90 degrees, and the refractive index of the first portion is smaller than the refractive index of the first layer.

[0012] Moreover, the angle θ is preferably greater than 90 degrees and equal to or less than 135 degrees.

[0013] The first moiety may include a Group 18 element, nitrogen, oxygen, or fluorine.

[0014] Another embodiment of the present invention is a display device including a plurality of the light-emitting elements and a plurality of transistors. When the light-emitting elements have a function of emitting light from the cathode side, the display device functions as a top-emission display device.

[0015] Another embodiment of the present invention is an electronic device including the display device described above and at least one of an antenna, a battery, and a sensor. [Effects of the Invention]

[0016] According to one embodiment of the present invention, a display device, a semiconductor device, or the like with high display quality can be provided. Alternatively, a highly reliable display device, a semiconductor device, or the like can be provided. Alternatively, a display device, a semiconductor device, or the like with low power consumption can be provided. Alternatively, a lightweight display device, a semiconductor device, or the like can be provided. Alternatively, a display device, a semiconductor device, or the like with high productivity can be provided. Alternatively, a novel display device, a semiconductor device, or the like can be provided.

[0017] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc. [Brief explanation of the drawings]

[0018] 1A and 1B are diagrams illustrating an example of the configuration of a display device. FIG. 2 is a diagram illustrating an example of the configuration of the display device. FIG. 3 is a diagram illustrating an example of the configuration of a display device. FIG. 4 is a diagram illustrating an example of the configuration of a display device. FIG. 5 is a diagram illustrating an example of the configuration of a display device. FIG. 6 is a diagram illustrating an example of the configuration of a display device. 7A to 7D are diagrams illustrating an example of a method for manufacturing an element substrate. 8A to 8D are diagrams illustrating an example of a method for manufacturing an element substrate. 9A to 9C are diagrams illustrating an example of a method for manufacturing an element substrate. 10A to 10C are diagrams illustrating an example of a method for manufacturing an element substrate. 11A to 11C are diagrams illustrating an example of a method for manufacturing an element substrate. 12A to 12C are diagrams illustrating an example of a method for manufacturing an element substrate. 13A to 13C are diagrams illustrating an example of a method for manufacturing an element substrate. 14A and 14B are diagrams illustrating modified examples of the element substrate. 15A to 15C are diagrams illustrating modified examples of the element substrate. 16A to 16C are diagrams illustrating an example of a method for manufacturing an element substrate. 17A to 17D are diagrams illustrating modified examples of the element substrate. Figure 18A is a diagram explaining the classification of crystal structures, Figure 18B is a diagram explaining the XRD spectrum of a CAAC-IGZO film, and Figure 18C is a diagram explaining the micro-electron beam diffraction pattern of a CAAC-IGZO film. FIG. 19A and FIGS. 19B1 to 19B5 are diagrams illustrating configuration examples of a display device. 20A to 20C are diagrams illustrating configuration examples of pixel circuits. 21A to 21D are diagrams illustrating configuration examples of light-emitting elements. 22A to 22C illustrate examples of the structure of a transistor. 23A to 23C are diagrams illustrating examples of the structure of a transistor. 24A to 24C illustrate examples of the structure of a transistor. 25A and 25B are diagrams illustrating an example of the configuration of a display device. FIG. 26 is a diagram illustrating an example of the configuration of a display device. 27A to 27F are diagrams illustrating an example of an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0019] In this specification, a semiconductor device is a device that utilizes semiconductor characteristics, and refers to a circuit including a semiconductor element (transistor, diode, photodiode, etc.), a device having such a circuit, etc. It also refers to any device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip including an integrated circuit, or an electronic component that houses a chip in a package are examples of semiconductor devices. Furthermore, memory devices, display devices, light-emitting devices, lighting devices, electronic devices, etc. are themselves semiconductor devices and may include semiconductor devices.

[0020] Furthermore, when it is stated in this specification that X and Y are connected, it is understood that the following cases are disclosed in this specification: when X and Y are electrically connected, when X and Y are functionally connected, and when X and Y are directly connected. Therefore, it is not limited to a predetermined connection relationship, for example, a connection relationship shown in a figure or text, and it is understood that connections other than those shown in a figure or text are also disclosed in a figure or text. X and Y are understood to be objects (e.g., devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

[0021] As an example of a case where X and Y are electrically connected, one or more elements (e.g., switches, transistors, capacitance elements, inductors, resistance elements, diodes, display devices, light-emitting devices, loads, etc.) that enable the electrical connection between X and Y can be connected between X and Y. The on and off states of the switches are controlled. In other words, the switches have the function of being in a conductive state (on state) or a non-conductive state (off state), and controlling whether or not a current flows.

[0022] As an example of a case where X and Y are functionally connected, one or more circuits that enable the functional connection between X and Y (for example, logic circuits (inverters, NAND circuits, NOR circuits, etc.), signal conversion circuits (digital-analog conversion circuits, analog-digital conversion circuits, gamma correction circuits, etc.), potential level conversion circuits (power supply circuits (boost circuits, step-down circuits, etc.), level shifter circuits that change the potential level of signals, etc.), voltage sources, current sources, switching circuits, amplifier circuits (circuits that can increase the signal amplitude or current amount, operational amplifiers, differential amplifier circuits, source follower circuits, buffer circuits, etc.), signal generation circuits, memory circuits, control circuits, etc.) can be connected between X and Y. As an example, even if another circuit is sandwiched between X and Y, X and Y are considered to be functionally connected if a signal output from X is transmitted to Y.

[0023] When it is explicitly stated that X and Y are electrically connected, this includes the case where X and Y are electrically connected (i.e., the case where X and Y are connected with another element or circuit between them) and the case where X and Y are directly connected (i.e., the case where X and Y are connected without another element or circuit between them).

[0024] Furthermore, for example, it can be expressed as follows: "X, Y, and the source (or first terminal, etc.) and drain (or second terminal, etc.) of the transistor are electrically connected to each other, and are electrically connected in the order of X, the source (or first terminal, etc.) of the transistor, the drain (or second terminal, etc.) of the transistor, and Y." Or, it can be expressed as follows: "The source (or first terminal, etc.) of the transistor is electrically connected to X, and the drain (or second terminal, etc.) of the transistor is electrically connected to Y, and X, the source (or first terminal, etc.) of the transistor, the drain (or second terminal, etc.) of the transistor, and Y are electrically connected in this order." Or, it can be expressed as follows: "X is electrically connected to Y via the source (or first terminal, etc.) and drain (or second terminal, etc.) of the transistor, and X, the source (or first terminal, etc.) of the transistor, the drain (or second terminal, etc.) of the transistor, and Y are provided in this connection order." By using expressions similar to these examples to define the order of connections in a circuit configuration, the source (or first terminal, etc.) and drain (or second terminal, etc.) of a transistor can be distinguished and the technical scope can be determined. Note that these expressions are merely examples and are not limiting. Here, X and Y are assumed to be objects (e.g., devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

[0025] Note that even when independent components are shown electrically connected in a circuit diagram, one component may have the functions of multiple components. For example, if part of a wiring also functions as an electrode, one conductive film has the functions of both a wiring and an electrode. Therefore, in this specification, the term "electrically connected" also includes such cases where one conductive film has the functions of multiple components.

[0026] Furthermore, in this specification and the like, the term "resistance element" can refer to, for example, a circuit element, wiring, or the like having a resistance value higher than 0 Ω. Therefore, in this specification and the like, the term "resistance element" includes wiring having a resistance value, a transistor in which a current flows between the source and drain, a diode, a coil, and the like. Therefore, the term "resistance element" can be replaced with terms such as "resistance," "load," or "region having a resistance value," and conversely, the terms "resistance," "load," or "region having a resistance value" can be replaced with terms such as "resistance element." The resistance value can be, for example, preferably 1 mΩ or more and 10 Ω or less, more preferably 5 mΩ or more and 5 Ω or less, and even more preferably 10 mΩ or more and 1 Ω or less. Furthermore, for example, the resistance value can be, for example, 1 Ω or more and 1×10 9 It may be set to Ω or less.

[0027] When a wiring is used as a resistor, the resistance value may be determined by the length of the wiring, or a conductor having a different resistivity from that of the wiring may be used as the resistor, or the resistance value may be determined by doping impurities into a semiconductor.

[0028] Furthermore, in this specification, the term "capacitive element" can refer to, for example, a circuit element having a capacitance value greater than 0 F, a region of wiring having a capacitance value greater than 0 F, parasitic capacitance, or the gate capacitance of a transistor. Therefore, in this specification, the term "capacitive element" includes not only a circuit element including a pair of electrodes and a dielectric between the electrodes, but also parasitic capacitance occurring between wiring and one of the source or drain of a transistor and the gate, and the like. Furthermore, terms such as "capacitive element," "parasitic capacitance," and "gate capacitance" can be replaced with terms such as "capacitance," and conversely, the term "capacitance" can be replaced with terms such as "capacitive element," "parasitic capacitance," and "gate capacitance." Furthermore, the term "pair of electrodes" in "capacitance" can be replaced with "pair of conductors," "pair of conductive regions," or "pair of regions." The capacitance value can be, for example, 0.05 fF or more and 10 pF or less. It can also be, for example, 1 pF or more and 10 μF or less.

[0029] In this specification, a transistor has three terminals called a gate, a source, and a drain. The gate is a control terminal that controls the conduction state of the transistor. The two terminals that function as a source or a drain are the input / output terminals of the transistor. One of the two input / output terminals becomes a source and the other becomes a drain depending on the transistor's conductivity type (n-channel or p-channel) and the level of the potential applied to the three terminals of the transistor. Therefore, in this specification, the terms source and drain are interchangeable. In addition, in this specification, when describing the connection relationship of a transistor, the terms "one of the source or drain" (or first electrode or first terminal) and "the other of the source or drain" (or second electrode or second terminal) are used. Note that, depending on the transistor structure, a backgate may be included in addition to the three terminals described above. In this case, in this specification, one of the gate or backgate of the transistor may be referred to as the first gate, and the other of the gate or backgate of the transistor may be referred to as the second gate. Furthermore, for the same transistor, the terms "gate" and "backgate" may be interchangeable. Furthermore, when a transistor has three or more gates, the gates may be referred to as a first gate, a second gate, a third gate, and so on in this specification and the like.

[0030] Furthermore, in this specification and the like, the term "node" can be rephrased as a terminal, wiring, electrode, conductive layer, conductor, impurity region, etc., depending on the circuit configuration, device structure, etc. Furthermore, the term "node" can be rephrased as a terminal, wiring, etc.

[0031] Furthermore, in this specification and the like, the terms "voltage" and "potential" can be interchanged as appropriate. "Voltage" refers to the potential difference from a reference potential. For example, if the reference potential is the ground potential (earth potential), then "voltage" can be interchanged with "potential." Note that ground potential does not necessarily mean 0 V. Furthermore, potential is relative, and as the reference potential changes, the potential applied to wiring, the potential applied to a circuit, etc., the potential output from a circuit, etc. also changes.

[0032] Furthermore, in this specification and the like, the terms "high-level potential (also referred to as "high-level potential," "H potential," or "H")" and "low-level potential (also referred to as "low-level potential," "L potential," or "L")" do not refer to specific potentials. For example, when two wirings are both described as "functioning as wirings that supply high-level potentials," the high-level potentials provided by both wirings do not have to be equal to each other. Similarly, when two wirings are both described as "functioning as wirings that supply low-level potentials," the low-level potentials provided by both wirings do not have to be equal to each other.

[0033] "Current" refers to the phenomenon of charge transfer (electrical conduction). For example, a statement that "electrical conduction of a positively charged body is occurring" can be rephrased as "electrical conduction of a negatively charged body is occurring in the opposite direction." Therefore, in this specification, unless otherwise specified, "current" refers to the phenomenon of charge transfer (electrical conduction) associated with the movement of carriers. The carriers referred to here include electrons, holes, anions, cations, complex ions, etc., and the carriers differ depending on the system through which the current flows (e.g., semiconductor, metal, electrolyte, vacuum, etc.). Furthermore, the "direction of current" in wiring, etc., refers to the direction in which positive carriers move and is expressed as a positive current amount. In other words, the direction in which negative carriers move is opposite to the direction of current and is expressed as a negative current amount. Therefore, in this specification, etc., unless otherwise specified regarding the positive / negative sign of the current (or the direction of current), a statement such as "current flows from element A to element B" can be rephrased as "current flows from element B to element A," etc. Furthermore, statements such as "current is input to element A" can be rephrased as "current is output from element A" or the like.

[0034] Furthermore, in this specification, the ordinal numbers "first," "second," and "third" are used to avoid confusion between components. Therefore, they do not limit the number of components. Furthermore, they do not limit the order of the components. For example, a component referred to as "first" in one embodiment of this specification may be a component referred to as "second" in another embodiment, in the claims, etc. Furthermore, for example, a component referred to as "first" in one embodiment of this specification, etc. may be omitted in another embodiment, in the claims, etc.

[0035] Furthermore, in this specification, terms indicating position, such as "above," "below," "upward," or "belowward," may be used for convenience in describing the positional relationship between components with reference to the drawings. Furthermore, the positional relationship between components changes as appropriate depending on the direction in which each component is depicted. Therefore, the terms are not limited to those used in the specification, and can be rephrased appropriately depending on the situation. For example, the expression "an insulator located on the upper surface of a conductor" can be rephrased as "an insulator located on the lower surface of a conductor" by rotating the orientation of the drawing 180 degrees.

[0036] Furthermore, the terms "above" and "below" do not limit the positional relationship of components to being directly above or below and in direct contact with each other. For example, the expression "electrode B on insulating layer A" does not require that electrode B be formed on insulating layer A in direct contact with it, and does not exclude the inclusion of other components between insulating layer A and electrode B.

[0037] Furthermore, in this specification, the terms "adjacent" and "close to" do not limit the state in which multiple components are in direct contact with each other. For example, the expression "electrode B adjacent to insulating layer A" includes not only the state in which insulating layer A and electrode B are in direct contact with each other, but also the state in which there is a space or another component between insulating layer A and electrode B.

[0038] Furthermore, in this specification and the like, terms such as "film" and "layer" can be interchanged depending on the situation. For example, the term "conductive layer" may be interchanged with the term "conductive film." Or, for example, the term "insulating film" may be interchanged with the term "insulating layer." Or, in some cases or depending on the situation, terms such as "film" and "layer" may not be used and may be interchanged with other terms. For example, the terms "conductive layer" or "conductive film" may be interchanged with the term "conductor." Or, for example, the terms "insulating layer" and "insulating film" may be interchanged with the term "insulator."

[0039] Furthermore, in this specification and the like, terms such as "electrode," "wiring," and "terminal" do not functionally limit these components. For example, an "electrode" may be used as part of a "wiring," and vice versa. Furthermore, the terms "electrode" and "wiring" include cases where multiple "electrodes" or "wirings" are integrally formed. Furthermore, for example, a "terminal" may be used as part of a "wiring" or "electrode," and vice versa. Furthermore, the term "terminal" includes cases where multiple "electrodes," "wirings," "terminals," etc. are integrally formed. Therefore, for example, an "electrode" can be part of a "wiring" or "terminal," and a "terminal" can be part of a "wiring" or "electrode." Furthermore, terms such as "electrode," "wiring," and "terminal" may be replaced with terms such as "region" in some cases.

[0040] Furthermore, in this specification and the like, terms such as "wiring," "signal line," and "power line" may be interchangeable depending on the circumstances. For example, the term "wiring" may be changed to the term "signal line." For example, the term "wiring" may be changed to the term "power line." Vice versa, terms such as "signal line" and "power line" may be changed to the term "wiring." A term such as "power line" may be changed to the term "signal line." Vice versa, terms such as "signal line" may be changed to the term "power line." Furthermore, the term "potential" applied to a wiring may be changed to the term "signal" depending on the circumstances. Vice versa, terms such as "signal" may be changed to the term "potential."

[0041] In this specification and the like, the term "impurities" in semiconductors refers to, for example, elements other than the main components constituting the semiconductor layer. For example, an element with a concentration of less than 0.1 atomic % is an impurity. The presence of impurities can cause, for example, an increase in the defect level density of the semiconductor, a decrease in carrier mobility, and a decrease in crystallinity. When the semiconductor is an oxide semiconductor, impurities that change the semiconductor characteristics include, for example, Group 1 elements, Group 2 elements, Group 13 elements, Group 14 elements, Group 15 elements, and transition metals other than the main components, particularly, for example, hydrogen (also contained in water), lithium, sodium, silicon, boron, phosphorus, carbon, and nitrogen. Specifically, when the semiconductor is a silicon layer, impurities that change the semiconductor characteristics include, for example, oxygen, Group 1 elements excluding hydrogen, Group 2 elements, Group 13 elements, and Group 15 elements.

[0042] In this specification, a switch refers to a device that can be in a conductive state (on state) or a non-conductive state (off state) and has the function of controlling whether or not a current flows. Alternatively, a switch refers to a device that has the function of selecting and switching a path through which a current flows. Examples include electrical switches and mechanical switches. In other words, the switch is not limited to a specific type as long as it can control a current.

[0043] Examples of electrical switches include transistors (e.g., bipolar transistors, MOS transistors, etc.), diodes (e.g., PN diodes, PIN diodes, Schottky diodes, MIM (Metal Insulator Metal) diodes, MIS (Metal Insulator Semiconductor) diodes, diode-connected transistors, etc.), and logic circuits combining these. When a transistor is used as a switch, the "conductive state" of the transistor refers to a state in which the source electrode and drain electrode of the transistor can be considered to be electrically short-circuited. The "non-conductive state" of the transistor refers to a state in which the source electrode and drain electrode of the transistor can be considered to be electrically disconnected. When a transistor is operated simply as a switch, the polarity (conductivity type) of the transistor is not particularly limited.

[0044] An example of a mechanical switch is a switch that uses MEMS (Micro Electro Mechanical Systems) technology. This switch has a mechanically movable electrode, and the movement of the electrode controls conduction and non-conduction.

[0045] As used herein, "parallel" refers to a state in which two straight lines are arranged at an angle of -10° or more and 10° or less. This therefore includes cases in which the angle is -5° or more and 5° or less. "Substantially parallel" or "roughly parallel" refers to a state in which two straight lines are arranged at an angle of -30° or more and 30° or less. "Perpendicular" refers to a state in which two straight lines are arranged at an angle of 80° or more and 100° or less. This therefore includes cases in which the angle is 85° or more and 95° or less. "Substantially perpendicular" or "approximately perpendicular" refers to a state in which two straight lines are arranged at an angle of 60° or more and 120° or less.

[0046] In this specification and the like, a metal oxide refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as oxide semiconductors or simply as OSs), and the like. For example, when a metal oxide is used in a semiconductor layer of a transistor, the metal oxide may be referred to as an oxide semiconductor or a metal oxide semiconductor. In other words, when a channel of a transistor having at least one of an amplifying function, a rectifying function, and a switching function is formed in a metal oxide, the metal oxide can be referred to as an oxide semiconductor or a metal oxide semiconductor. Furthermore, the term "OS transistor" can be rephrased as a transistor having a metal oxide or an oxide semiconductor.

[0047] In this specification and the like, nitrogen-containing metal oxides may also be collectively referred to as metal oxides. Nitrogen-containing metal oxides may also be referred to as metal oxynitrides.

[0048] In this specification and the like, the configurations shown in each embodiment can be combined as appropriate with the configurations shown in other embodiments to form one aspect of the present invention. In addition, when multiple configuration examples are shown in one embodiment, the configuration examples can be combined as appropriate with each other.

[0049] The embodiments described in this specification will be described with reference to the drawings. However, it will be readily understood by those skilled in the art that the embodiments can be implemented in many different ways, and that various changes in form and details can be made without departing from the spirit and scope of the invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments. Note that in the configuration of the invention of the embodiments, the same reference numerals are used in different drawings for the same parts or parts having similar functions, and repeated description thereof may be omitted. Also, to make the drawings easier to understand, some components may be omitted in perspective views, top views, etc. Also, to make the drawings easier to understand, notations such as hatching may be omitted.

[0050] In addition, in the drawings of this specification, the size, layer thickness, or region may be exaggerated for clarity. Therefore, the size or aspect ratio is not necessarily limited. Note that the drawings are schematic illustrations of ideal examples and are not limited to the shapes or values ​​shown in the drawings. For example, variations in signal, voltage, or current due to noise, or variations in signal, voltage, or current due to timing deviations may be included.

[0051] In this specification, when the same reference numeral is used for multiple elements, and particularly when it is necessary to distinguish between them, the reference numeral may be suffixed with an identifying character such as "A," "a," "_1," "[i]," or "[m,n]." For example, multiple pixels 230 may be referred to as pixel 230R, pixel 230G, or pixel 230B. In other words, when describing matters common to pixel 230R, pixel 230G, and pixel 230B, or when there is no need to distinguish between them, they may be simply referred to as "pixel 230."

[0052] In this specification, etc., a device that uses a metal mask or an FMM (fine metal mask, high-resolution metal mask) may be referred to as an MM (metal mask) structure. In addition, in this specification, etc., a device that does not use a metal mask or an FMM may be referred to as an MML (metal maskless) structure. Because a display device with an MML structure is fabricated without using a metal mask, it has a higher degree of design freedom in terms of pixel arrangement, pixel shape, etc. than a display device with an FMM structure or an MM structure.

[0053] In the manufacturing method of a display device with an MML structure, the island-shaped EL layer is not formed using a metal mask pattern, but is formed by processing the EL layer after it has been deposited over the entire surface. This makes it possible to realize high-definition display devices or display devices with a high aperture ratio, which have been difficult to achieve until now. Furthermore, since the EL layer can be made separately for each color, it is possible to realize display devices with extremely vivid images, high contrast, and high display quality. In addition, by providing a sacrificial layer on the EL layer, damage to the EL layer during the display device manufacturing process can be reduced, improving the reliability of the light-emitting device.

[0054] When a display device is formed using a fine metal mask (FMM) structure, there are cases where restrictions are imposed on the pixel arrangement configuration, etc. Here, the FMM structure will be described below.

[0055] The FMM structure involves placing a metal mask (also called an FMM) with openings facing the substrate so that EL is deposited in the desired area during EL deposition. EL deposition is then performed through the FMM, resulting in EL deposition in the desired area. As the substrate size increases during EL deposition, the FMM also increases in size and weight. Furthermore, heat and other factors are applied to the FMM during EL deposition, which can cause deformation of the FMM. Alternatively, a method can be used in which a certain tension is applied to the FMM during EL deposition, so the weight and strength of the FMM are important parameters.

[0056] Therefore, when designing a pixel arrangement configuration using FMM, the above parameters and other factors must be taken into consideration, and consideration must be given under certain limitations. On the other hand, a display device according to one embodiment of the present invention is fabricated using an MML structure, which provides an excellent effect of allowing greater freedom in pixel arrangement configuration and the like compared to an FMM structure. Note that this configuration is highly compatible with, for example, flexible devices, and allows various circuit arrangements for either or both of the pixels and the drive circuits.

[0057] (Embodiment 1) A display device 100 according to one embodiment of the present invention will be described with reference to the drawings.

[0058] <<Configuration example>> 1A is a perspective schematic diagram of a display device 100. The display device 100 has a configuration in which a substrate 111 and a substrate 121 are bonded together. The display device 100 has a display area 235, a peripheral circuit area 232, a peripheral circuit area 233, and the like. FIG. 1 shows an example in which an FPC 124 is mounted on the display device 100. Therefore, the configuration shown in FIG. 1A can also be said to be a display module having the display device 100 and the FPC 124.

[0059] The peripheral circuit region 232 and the peripheral circuit region 233 include circuits for supplying signals to the display region 235. The circuits included in the peripheral circuit region 232 and the peripheral circuit region 233 are sometimes collectively referred to as a "peripheral driving circuit." Examples of circuits included in the peripheral driving circuit include a scanning line driving circuit and a signal line driving circuit.

[0060] A part or all of the peripheral driving circuit may be implemented as an IC (integrated circuit). For example, an IC including a part or all of the peripheral driving circuit may be provided on the substrate 111 by a COG (chip on glass) method or a COF (chip on film) method. The IC may also be mounted on the FPC 124 by a COF method or the like.

[0061] Signals and power supplied to the display area 235, the peripheral circuit area 232, and the peripheral circuit area 233 are input from the outside via the FPC .

[0062] 1A also includes an enlarged view of a portion of display region 235. A plurality of pixels 240 are arranged in a matrix in display region 235. Pixels 240 include pixel 230R, pixel 230G, and pixel 230B. As mentioned above, in this specification and the like, when describing matters common to pixel 230R, pixel 230G, and pixel 230B, or when there is no need to distinguish between the three, they may be simply referred to as "pixel 230."

[0063] [Cross-sectional structure example] 1B is a cross-sectional view of the portion indicated by the dashed line A1-A2 in FIG. 1A, showing a cross section of a part of the display region 235, a part of the peripheral circuit region 233, and a part of the region including the FPC 124.

[0064] Each of the pixels 230R, 230G, and 230B has a light-emitting element 170 as a display element. The light-emitting element 170 has an electrode 171 that functions as an anode, an EL layer 172, and an electrode 173 that functions as a cathode. In FIG. 1B, the light-emitting element 170 in the pixel 230R is indicated as light-emitting element 170R, the light-emitting element 170 in the pixel 230G is indicated as light-emitting element 170G, and the light-emitting element 170 in the pixel 230B is indicated as light-emitting element 170B.

[0065] In this specification and the like, the electrode 171, the EL layer 172, and the electrode 173 of the light-emitting element 170R may be referred to as the electrode 171R, the EL layer 172R, and the electrode 173R. The electrode 171, the EL layer 172, and the electrode 173 of the light-emitting element 170G may be referred to as the electrode 171G, the EL layer 172G, and the electrode 173G. The electrode 171, the EL layer 172, and the electrode 173 of the light-emitting element 170B may be referred to as the electrode 171B, the EL layer 172B, and the electrode 173B.

[0066] The light emitting element 170R has a function of emitting light 175R. The light emitting element 170G has a function of emitting light 175G. The light emitting element 170B has a function of emitting light 175B. For example, the light 175R is red light, the light 175G is green light, and the light 175B is blue light.

[0067] Each of the pixels 230R, 230G, and 230B includes a transistor 251 for driving a display element. The transistor 251 is a transistor that controls a current flowing through the light-emitting element 170 (also referred to as a driving transistor).

[0068] 1B, a transistor 252 is shown as an example of a transistor included in the peripheral circuit region 233.

[0069] The display device 100 includes a transistor 251, a transistor 252, a light-emitting element 170, and the like between a substrate 111 and a substrate 121. The substrate 111 and the substrate 121 overlap with each other with an adhesive layer 142 interposed therebetween.

[0070] The adhesive layer 142 can be made of various curable adhesives, such as a photo-curable adhesive (e.g., an ultraviolet curable adhesive), a reactive curable adhesive, a thermosetting adhesive, or an anaerobic adhesive. Examples of such adhesives include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. In particular, a material with low moisture permeability, such as epoxy resin, is preferable. Alternatively, a two-component resin may be used. Alternatively, an adhesive sheet or the like may be used.

[0071] The transistor 251 and the transistor 252 are provided over the substrate 111 with an insulating layer 112 interposed therebetween. The transistor 251 and the transistor 252 are covered with an insulating layer 210 and an insulating layer 213. An insulating layer 114 is provided over the insulating layer 213. The insulating layer 114 preferably functions as a planarizing layer. Note that the "planarizing layer" refers to a layer having a surface on which unevenness is reduced.

[0072] The number of insulating layers covering the transistors is not limited and may be a single layer or two or more layers. It is preferable to use a material that is resistant to the diffusion of impurities such as water and hydrogen for at least one of the insulating layers covering each transistor. This allows the insulating layer to function as a barrier film. This configuration effectively prevents impurities from diffusing into the transistors from the outside, thereby realizing a highly reliable display device.

[0073] In the pixel 230, an electrode 171 is provided over the insulating layer 114. The electrode 171 is electrically connected to one of the source and the drain of the transistor 251 through an opening provided in the insulating layer 114.

[0074] An EL layer 172 is provided over the electrode 171, and an electrode 173 is provided over the EL layer 172. The electrode 173 has a region that overlaps with the electrode 171 with the EL layer 172 interposed therebetween. A protective layer 126 is provided over the electrode 173. An insulating layer 115 is provided to cover the light-emitting element 170 and the protective layer 126. The insulating layer 115 preferably covers the side surfaces of the light-emitting element 170. The insulating layer 115 is preferably formed from a material that is difficult for hydrogen and moisture to permeate.

[0075] An insulating layer 116 is provided over the insulating layer 115. The insulating layer 116 preferably functions as a planarization layer. A conductive layer 118 is provided over the insulating layer 116. The conductive layer 118 is electrically connected to an electrode 173 through an electrode 117 that is embedded in the insulating layer 116, the insulating layer 115, and the protective layer 126. The conductive layer 118 is electrically connected to the multiple electrodes 173 and functions as a common electrode.

[0076] 1B also includes an electrode 228 and an electrode 229. The electrode 228 is provided on the insulating layer 211. The electrode 229 is electrically connected to the electrode 228 through an opening provided in the insulating layer 210.

[0077] Furthermore, the FPC 124 is electrically connected to the electrodes 229 via the connection layer 138. The electrodes 229 are electrically connected to the peripheral drive circuitry.

[0078] The connection layer 138 may be made of an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like.

[0079] The light-emitting element 170 is, for example, a top-emission light-emitting element. When the light-emitting element 170 is a top-emission light-emitting element, the electrode 171 has a function of reflecting visible light, and the electrode 173 has a function of transmitting visible light. Therefore, light 175 is emitted from the electrode 173 side. In addition, the conductive layer 118 also has a function of transmitting visible light.

[0080] The EL layer 172 includes at least a light-emitting layer. The EL layer 172 may include, as a layer other than the light-emitting layer, a layer containing a substance with a high hole-injecting property, a substance with a high hole-transporting property, a hole-blocking material, an electron-blocking material, a substance with a high electron-transporting property, a substance with a high electron-injecting property, or a bipolar substance (a substance with high electron-transporting property and hole-transporting property).

[0081] The color of light emitted from the light emitting element 170 can be white, red, green, blue, cyan, magenta, yellow, or the like, depending on the material that makes up the EL layer 172 .

[0082] There are two methods for achieving color display: combining a light-emitting element 170 that emits white light with a colored layer (color filter), and providing light-emitting elements 170 that emit different colors for each pixel. The former method is more productive than the latter. On the other hand, the latter method requires the creation of a separate EL layer 172 for each pixel, making it less productive than the former method. However, the latter method can produce an emitted color with higher color purity than the former method.

[0083] In addition to the latter method, color purity can be further improved by providing a micro-optical resonator (microcavity) structure to light-emitting element 170. To provide a microcavity structure to light-emitting element 170, the product (optical path length) of distance d between electrode 171 and electrode 173 and refractive index n of EL layer 172 should be configured to be m times half the wavelength λ (m is an integer equal to or greater than 1). Therefore, distance d can be calculated using Equation 1.

[0084]

number

[0085] According to Equation 1, in light emitting element 170 with a microcavity structure, distance d is determined according to the wavelength (emission color) of light 175 (light 175R, light 175G, light 175B). Distance d corresponds to the thickness of EL layer 172. Therefore, EL layer 172G may be provided thicker than EL layer 172B, and EL layer 172R may be provided thicker than EL layer 172G.

[0086] Strictly speaking, distance d is the distance from the reflective area of ​​electrode 171, which functions as a reflective electrode, to the reflective area of ​​electrode 173, which functions as a semi-transmissive and semi-reflective electrode. However, it may be difficult to precisely determine the positions of the reflective areas of electrode 171 and electrode 173. In this case, it is possible to obtain a sufficient microcavity effect by assuming that any position of electrode 171 or electrode 173 is the reflective area.

[0087] The light-emitting element 170 is composed of a hole transport layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, etc. Detailed configuration examples of the light-emitting element 170 will be described in other embodiments. In order to increase the extraction efficiency of light 175 in the microcavity structure, it is preferable to set the optical distance from the electrode 171 functioning as a reflective electrode to the light-emitting layer to an odd multiple of λ / 4. To achieve this optical distance, it is preferable to appropriately adjust the thickness of each layer that constitutes the light-emitting element 170.

[0088] Furthermore, when light 175 is emitted from the electrode 173 side, it is preferable that the reflectance of electrode 173 is greater than the transmittance. The transmittance of electrode 173 for light 175 is preferably 2% to 50%, more preferably 2% to 30%, and even more preferably 2% to 10%. By reducing the transmittance of electrode 173 (increasing the reflectance), the effect of the microcavity can be enhanced.

[0089] Both low molecular weight compounds and high molecular weight compounds, and inorganic compounds may be used for the EL layer 172. The layers constituting the EL layer 172 can be formed by methods such as vapor deposition (including vacuum deposition), transfer, printing, inkjet, and coating.

[0090] The EL layer 172 may contain inorganic compounds such as quantum dots. For example, quantum dots can be used in the light-emitting layer to function as a light-emitting material.

[0091] Color display can be achieved by controlling the brightness of light 175 (light 175R, light 175G, and light 175B) for each pixel. The hues of the emitted colors combined to achieve color display can be not only a combination of red, green, and blue, but also a combination of yellow, cyan, and magenta. The hues of the emitted colors to be combined can be set appropriately depending on the purpose or application.

[0092] [substrate] There are no significant limitations on the materials used for the substrate 111 and the substrate 121. The materials may be determined depending on the purpose, taking into consideration the presence or absence of light transmittance and the heat resistance sufficient to withstand heat treatment. For example, a glass substrate such as barium borosilicate glass or aluminoborosilicate glass, a ceramic substrate, a quartz substrate, or a sapphire substrate may be used. Alternatively, a semiconductor substrate, a flexible substrate, a laminated film, a base film, or the like may also be used.

[0093] Examples of semiconductor substrates include semiconductor substrates made of silicon or germanium, or compound semiconductor substrates made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, or gallium oxide. The semiconductor substrate may be a single-crystal semiconductor or a polycrystalline semiconductor.

[0094] In order to increase the flexibility of the display device 100, the substrates 111 and 121 may be made of flexible substrates, laminated films, base films, or the like.

[0095] Materials that can be used for flexible substrates, laminated films, base films, etc. include, for example, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyacrylonitrile resin, acrylic resin, polyimide resin, polymethyl methacrylate resin, polycarbonate (PC) resin, polyethersulfone (PES) resin, polyamide resin (nylon, aramid, etc.), polysiloxane resin, cycloolefin resin, polystyrene resin, polyamideimide resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, and cellulose nanofiber.

[0096] By using the above materials for the substrate, it is possible to provide a lightweight display device. Also, by using the above materials for the substrate, it is possible to provide a display device that is resistant to impact. Also, by using the above materials for the substrate, it is possible to provide a display device that is less likely to break.

[0097] The lower the linear expansion coefficient of the flexible substrate used for the substrate 111 and the substrate 121, the more preferable it is, since deformation due to the environment is suppressed. For example, the linear expansion coefficient of the flexible substrate used for the substrate 111 and the substrate 121 is 1×10 -3 / K or less, 5×10 -5 / K or less, or 1×10 -5 / K or less. Aramid is particularly suitable as a flexible substrate because of its low linear expansion coefficient.

[0098] [Conductive layer] Conductive materials that can be used for conductive layers such as the gate, source, and drain of a transistor, as well as various wiring and electrodes that constitute a display device, include metal elements selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium (Hf), vanadium (V), niobium (Nb), manganese, magnesium, zirconium, and beryllium, alloys containing the above metal elements, and alloys combining the above metal elements. Semiconductors, such as polycrystalline silicon containing impurity elements such as phosphorus, and silicides such as nickel silicide may also be used. The method for forming the conductive material is not particularly limited, and various formation methods, such as vapor deposition, CVD, sputtering, and spin coating, can be used.

[0099] In addition, examples of conductive materials that can be used for the conductive layer include conductive materials containing oxygen, such as indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, and indium tin oxide to which silicon oxide has been added. Also, conductive materials containing nitrogen, such as titanium nitride, tantalum nitride, and tungsten nitride, can be used. A layered structure can also be formed by appropriately combining conductive materials containing oxygen, conductive materials containing nitrogen, and materials containing the above-mentioned metal elements.

[0100] The conductive material that can be used for the conductive layer may have a single-layer structure or a stacked structure of two or more layers. For example, there are a single-layer structure of an aluminum layer containing silicon, a two-layer structure in which a titanium layer is stacked on an aluminum layer, a two-layer structure in which a titanium layer is stacked on a titanium nitride layer, a two-layer structure in which a tungsten layer is stacked on a titanium nitride layer, a two-layer structure in which a tungsten layer is stacked on a tantalum nitride layer, and a three-layer structure in which a titanium layer is stacked on an aluminum layer and a titanium layer is further stacked on the titanium layer. Furthermore, an aluminum alloy containing one or more elements selected from titanium, tantalum, tungsten, molybdenum, chromium, neodymium, and scandium may be used as the conductive material.

[0101] When the light-emitting element 170 is a top-emission light-emitting element, the electrode 171 is preferably formed using a conductive material that efficiently reflects light emitted from the EL layer 172. Note that the structure of the electrode 171 is not limited to a single layer, and it may have a stacked structure of multiple layers. For example, when the electrode 171 is used as an anode, a light-transmitting layer such as indium tin oxide may be provided in contact with the EL layer 172, and a highly reflective layer (such as aluminum, an alloy containing aluminum, or silver) may be provided in contact with the light-transmitting layer.

[0102] Examples of conductive materials that reflect visible light include metal materials such as aluminum, gold, platinum, silver, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, and palladium, as well as alloys containing these metal materials. Lanthanum, neodymium, germanium, and the like may be added to the above metal materials or alloys. Furthermore, the conductive material may be formed using an alloy containing aluminum (aluminum alloy), such as an alloy of aluminum and titanium, an alloy of aluminum and nickel, or an alloy of aluminum and neodymium, or an alloy containing silver, such as an alloy of silver and copper, an alloy of silver, palladium, and copper, or an alloy of silver and magnesium. Silver-copper alloys are preferred because of their high heat resistance. Furthermore, a metal film or alloy film and a metal oxide film may be stacked. For example, stacking a metal film or a metal oxide film in contact with an aluminum alloy film can suppress oxidation of the aluminum alloy film. Other examples of metal films and metal oxide films include titanium and titanium oxide. As described above, a light-transmitting conductive film and a film made of a metal material may be stacked. For example, a laminated film of silver and indium tin oxide, or a laminated film of an alloy of silver and magnesium and indium tin oxide (ITO) can be used.

[0103] Examples of light-transmitting conductive materials include conductive oxides such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, and zinc oxide doped with gallium, or graphene. Alternatively, oxide conductors can be used as light-transmitting conductive materials. Metal materials such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, and titanium, or alloy materials containing such metal materials, can be used. Alternatively, nitrides of such metal materials (e.g., titanium nitride) can be used. When using metal materials or alloy materials (or their nitrides), they should be thin enough to have light-transmitting properties. A stacked film of the above materials can also be used as a conductive layer. For example, a stacked film of an alloy of silver and magnesium and indium tin oxide is preferable because it can enhance conductivity. These can also be used for conductive layers such as various wirings and electrodes constituting a display device, and for conductive layers (conductive layers functioning as pixel electrodes or common electrodes) in display elements.

[0104] Here, oxide conductors, which are a type of metal oxide, will be described. In this specification and the like, oxide conductors may be referred to as OC (Oxide Conductors). For example, when oxygen vacancies are formed in a metal oxide and hydrogen is added to the oxygen vacancies, a donor level is formed near the conduction band of the oxide conductor. As a result, the metal oxide becomes electrically conductive, increasing its conductivity. A metal oxide that has become electrically conductive can be called an oxide conductor. In general, oxide semiconductors have a large energy gap and are therefore transparent to visible light. On the other hand, oxide conductors are metal oxides that have a donor level near the conduction band. Therefore, oxide conductors are less affected by absorption due to the donor level and have the same level of transparency to visible light as oxide semiconductors.

[0105] [Insulating layer] Each insulating layer is made of a single layer or a stack of layers of a material selected from aluminum nitride, aluminum oxide, aluminum nitride oxide, aluminum oxynitride, magnesium oxide, silicon nitride, silicon oxide, silicon nitride oxide, silicon oxynitride, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, tantalum oxide, aluminum silicate, etc. Alternatively, a mixture of two or more materials selected from oxide materials, nitride materials, oxynitride materials, and nitride oxide materials may be used.

[0106] In this specification, "nitride oxide" refers to a compound containing more nitrogen than oxygen. "Oxynitride" refers to a compound containing more oxygen than nitrogen. The content of each element can be measured, for example, by Rutherford Backscattering Spectrometry (RBS).

[0107] In particular, the insulating layer 113 and the insulating layer 213 are preferably formed using an insulating material that is impermeable to impurities. For example, an insulating material containing boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, or tantalum may be used in a single layer or a stacked layer. Examples of insulating materials that are impermeable to impurities include aluminum oxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, tantalum oxide, and silicon nitride.

[0108] By using an insulating material that is impermeable to impurities for the insulating layer 113, it is possible to suppress diffusion of impurities from the substrate 111 side and improve the reliability of the transistor. By using an insulating material that is impermeable to impurities for the insulating layer 213, it is possible to suppress diffusion of impurities from the insulating layer 114 side and improve the reliability of the transistor.

[0109] Furthermore, heat-resistant organic materials such as polyimide, acrylic resin, benzocyclobutene resin, polyamide, and epoxy resin can be used as an insulating layer that can function as a planarization layer. In addition to the above organic materials, low-dielectric-constant materials (low-k materials), siloxane resin, PSG (phosphorus glass), BPSG (borophosphorus glass), and the like can also be used. Note that multiple insulating layers made of these materials may be stacked.

[0110] The siloxane-based resin corresponds to a resin containing Si-O-Si bonds formed using a siloxane-based material as a starting material. The siloxane-based resin may have an organic group (e.g., an alkyl group or an aryl group) or a fluoro group as a substituent. The organic group may also have a fluoro group.

[0111] Furthermore, CMP treatment may be performed on the surface of the insulating layer, etc. By performing CMP treatment, unevenness on the sample surface can be reduced, and the coverage of the insulating layer and conductive layer to be formed subsequently can be improved.

[0112] [About transistors] In one embodiment of the present invention, the structure of a transistor included in a display device is not particularly limited. For example, a planar transistor or a staggered transistor may be used. Furthermore, the transistor may have either a top-gate structure or a bottom-gate structure. Alternatively, gate electrodes may be provided above and below a channel.

[0113] The transistors in the peripheral driving circuit and the transistors in the pixel circuit may have the same structure or different structures. The transistors in the peripheral driving circuit may all have the same structure or two or more types of structures may be combined. Similarly, the transistors in the pixel circuit may all have the same structure or two or more types of structures may be combined.

[0114] [Semiconductor materials] There is no significant limitation on the crystallinity of a semiconductor material used for a semiconductor layer of a transistor. Any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single-crystal semiconductor, or a semiconductor having a crystalline region in part) may be used. Note that the use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0115] For example, semiconductor materials used for semiconductor layers of transistors can include silicon, germanium, silicon carbide, gallium arsenide, metal oxides, compound semiconductors such as nitride semiconductors, and organic semiconductors.

[0116] For example, semiconductor materials used for transistors can be polycrystalline silicon (polysilicon), amorphous silicon, etc. Also, oxide semiconductors, which are a type of metal oxide, can be used for transistors.

[0117] <Metal oxides> Here, metal oxides that can be used as oxide semiconductors will be described.

[0118] The metal oxide used as the oxide semiconductor preferably contains at least indium or zinc. It is particularly preferable that it contains indium and zinc. It is also preferable that it contains aluminum, gallium, yttrium, tin, or the like in addition to these. It may also contain one or more elements selected from boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, cobalt, and the like.

[0119] Here, we consider a case where the metal oxide is an In-M-Zn oxide containing indium, element M, and zinc. The element M is aluminum, gallium, yttrium, or tin. Other elements that can be used for element M include boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and cobalt. However, there are cases where a combination of the aforementioned elements can be used as element M.

[0120] In this specification and the like, nitrogen-containing metal oxides may also be collectively referred to as metal oxides. Nitrogen-containing metal oxides may also be referred to as metal oxynitrides.

[0121] <Classification of crystal structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 18A. Fig. 18A is a diagram illustrating classification of crystal structures of oxide semiconductors, typically IGZO (a metal oxide containing In, Ga, and Zn).

[0122] As shown in FIG. 18A, oxide semiconductors are broadly classified into "amorphous," "crystalline," and "crystal." "Amorphous" includes completely amorphous. "Crystalline" includes c-axis-aligned crystalline (CAAC), nanocrystalline (nc), and cloud-aligned composite (CAC) (excluding single crystal and polycrystal). "Crystalline" excludes single crystal, polycrystal, and completely amorphous. "Crystalline" includes single crystal and polycrystal.

[0123] The structure within the bold frame in Figure 18A is an intermediate state between "Amorphous" and "Crystal" and belongs to a new boundary region (New crystalline phase). In other words, this structure can be said to be completely different from the energetically unstable "Amorphous" and "Crystal."

[0124] The crystalline structure of a film or substrate can be evaluated using X-ray diffraction (XRD) spectroscopy. Figure 18B shows the XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement of a CAAC-IGZO film classified as "Crystalline." The horizontal axis represents 2θ [deg.], and the vertical axis represents intensity [au]. The GIXD method is also known as the thin-film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by GIXD measurement shown in Figure 18B may be simply referred to as the XRD spectrum in this specification. The composition of the CAAC-IGZO film shown in Figure 18B is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. The thickness of the CAAC-IGZO film shown in Figure 18B is 500 nm.

[0125] As shown in Figure 18B, a clear peak indicating crystallinity is detected in the XRD spectrum of the CAAC-IGZO film. Specifically, a peak indicating c-axis orientation is detected near 2θ = 31° in the XRD spectrum of the CAAC-IGZO film. As shown in Figure 18B, the peak near 2θ = 31° is asymmetric with respect to the angle at which the peak intensity is detected.

[0126] The crystalline structure of a film or substrate can be evaluated by the diffraction pattern (also called the nanobeam electron diffraction pattern) observed by nanobeam electron diffraction (NBED). The diffraction pattern of the CAAC-IGZO film is shown in Figure 18C. Figure 18C shows a diffraction pattern observed by NBED, in which an electron beam is incident parallel to the substrate. The composition of the CAAC-IGZO film shown in Figure 18C is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. In the nanobeam electron diffraction method, electron diffraction is performed using a probe diameter of 1 nm.

[0127] As shown in FIG. 18C, multiple spots indicating c-axis orientation are observed in the diffraction pattern of the CAAC-IGZO film.

[0128] <Oxide semiconductor structure> Note that oxide semiconductors may be classified differently from those shown in FIG. 18A when focusing on their crystal structures. For example, oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include the above-mentioned CAAC-OS and nc-OS. Non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, amorphous-like oxide semiconductors (a-like OSs), amorphous oxide semiconductors, and the like.

[0129] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0130] [CAAC-OS] CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction can be the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region can also be a region with a uniform lattice arrangement. Furthermore, CAAC-OS has a region where multiple crystalline regions are connected in the ab-plane direction, and the region may have distortion. Note that distortion refers to a location where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with a different uniform lattice arrangement in the region where multiple crystalline regions are connected. In other words, CAAC-OS is an oxide semiconductor with a c-axis aligned but no clear orientation in the ab-plane direction.

[0131] Each of the multiple crystalline regions is composed of one or more minute crystals (crystals with a maximum diameter of less than 10 nm). When a crystalline region is composed of one minute crystal, the maximum diameter of the crystalline region is less than 10 nm. When a crystalline region is composed of many minute crystals, the size of the crystalline region may be several tens of nm.

[0132] In an In-M-Zn oxide (wherein M is one or more elements selected from aluminum, gallium, yttrium, tin, titanium, etc.), the CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter referred to as an In layer) and a layer containing M, zinc (Zn), and oxygen (hereinafter referred to as an (M, Zn) layer) are stacked. Note that indium and the element M are mutually substituted. Therefore, the (M, Zn) layer may contain indium. The In layer may contain M. The In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution TEM image, for example.

[0133] When the CAAC-OS film is subjected to structural analysis using, for example, an XRD apparatus, a peak indicating c-axis orientation is detected at or near 2θ=31° in out-of-plane XRD measurement using θ / 2θ scan. Note that the position of the peak indicating c-axis orientation (2θ value) may vary depending on the type and composition of the metallic elements constituting the CAAC-OS.

[0134] Furthermore, for example, in the electron diffraction pattern of the CAAC-OS film, multiple bright spots are observed, and the spots are observed at positions that are point-symmetric with respect to the spot of the incident electron beam that has passed through the sample (also called the direct spot).

[0135] When the crystalline region is observed from the specific direction, the lattice arrangement within the crystalline region is basically a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be non-regular hexagonal. Furthermore, the distortion may have a pentagonal, heptagonal, or other lattice arrangement. In the CAAC-OS, no clear grain boundaries are observed even near the distortion. This indicates that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is thought to be because the CAAC-OS can tolerate distortion due to the lack of close-packed oxygen atom arrangement in the ab-plane direction and the change in interatomic bond distance caused by metal atom substitution.

[0136] A crystal structure with clear grain boundaries is called polycrystalline. Grain boundaries act as recombination centers, trapping carriers and potentially causing a decrease in the on-state current and field-effect mobility of a transistor. Therefore, CAAC-OS, which lacks clear grain boundaries, is one of the crystalline oxides with a crystal structure suitable for use in the semiconductor layer of a transistor. Zn is preferred for use in CAAC-OS. For example, In-Zn oxide and In-Ga-Zn oxide are suitable because they can suppress the generation of grain boundaries more effectively than In oxide.

[0137] CAAC-OS is an oxide semiconductor with high crystallinity and no clear grain boundaries. Therefore, it can be said that the decrease in electron mobility due to grain boundaries is unlikely to occur in CAAC-OS. Furthermore, since the crystallinity of oxide semiconductors can be reduced by impurities or defects, CAAC-OS can be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, oxide semiconductors with CAAC-OS have stable physical properties. Therefore, oxide semiconductors with CAAC-OS are heat-resistant and highly reliable. Furthermore, CAAC-OS is stable even under high temperatures (so-called thermal budgets) during the manufacturing process. Therefore, using CAAC-OS for OS transistors enables greater flexibility in the manufacturing process.

[0138] [nc-OS] The nc-OS has periodic atomic arrangement in a microscopic region (e.g., a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has microcrystalline structures. The size of the microcrystalline structures is, for example, 1 nm to 10 nm, particularly 1 nm to 3 nm, and therefore these microcrystalline structures are also called nanocrystalline structures. Furthermore, the nc-OS exhibits no regularity in the crystal orientation between different nanocrystalline structures. Therefore, the entire film lacks orientation. Therefore, depending on the analytical method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor. For example, when a structural analysis of an nc-OS film is performed using an XRD apparatus, no peaks indicating crystallinity are detected in out-of-plane XRD measurements using θ / 2θ scanning. Furthermore, when an nc-OS film is subjected to electron diffraction (also known as selected-area electron diffraction) using an electron beam with a probe diameter larger than that of nanocrystalline structures (e.g., 50 nm or larger), a halo-like diffraction pattern is observed. On the other hand, when electron diffraction (also called nanobeam electron diffraction) is performed on an nc-OS film using an electron beam with a probe diameter close to or smaller than the size of the nanocrystals (for example, 1 nm to 30 nm), an electron diffraction pattern can be obtained in which multiple spots are observed within a ring-shaped region centered on the direct spot.

[0139] [a-like OS] The a-like OS is an oxide semiconductor having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS. Furthermore, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and CAAC-OS.

[0140] <Oxide semiconductor structure> Next, the above-mentioned CAC-OS will be described in detail, which relates to the material composition.

[0141] [CAC-OS] CAC-OS is a material structure in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or a similar size range. Hereinafter, a metal oxide in which one or more metal elements are unevenly distributed and the regions containing the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or a similar size range, is also referred to as a mosaic or patch state.

[0142] Furthermore, CAC-OS has a mosaic structure in which the material is separated into first and second regions, and the first regions are distributed throughout the film (hereinafter also referred to as a cloud structure). That is, CAC-OS is a composite metal oxide having a structure in which the first and second regions are mixed.

[0143] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In-Ga-Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In-Ga-Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0144] Specifically, the first region is a region whose main component is indium oxide, indium zinc oxide, or the like. The second region is a region whose main component is gallium oxide, gallium zinc oxide, or the like. In other words, the first region can be rephrased as a region whose main component is In. The second region can be rephrased as a region whose main component is Ga.

[0145] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0146] For example, in the case of CAC-OS in In-Ga-Zn oxide, EDX mapping obtained using EDX (Energy Dispersive X-ray spectroscopy) confirms that the CAC-OS has a structure in which a region mainly composed of In (first region) and a region mainly composed of Ga (second region) are unevenly distributed and mixed.

[0147] When CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act in a complementary manner, thereby providing the CAC-OS with a switching function (the ability to turn on and off). In other words, CAC-OS has a conductive function in part of the material and an insulating function in part of the material, and the material as a whole functions as a semiconductor. By separating the conductive function from the insulating function, both functions can be maximized. Therefore, by using CAC-OS in a transistor, a high on-current (I on ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0148] Oxide semiconductors have a variety of structures, each with different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0149] <Transistors containing oxide semiconductors> Next, a case where the oxide semiconductor is used in a transistor will be described.

[0150] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0151] An oxide semiconductor with a low carrier concentration is preferably used for a channel formation region of a transistor. For example, the carrier concentration of the channel formation region of an oxide semiconductor is 1×10 17 cm -3 Less than 1 × 10 15 cm -3 or less, more preferably 1 × 10 13 cm -3 Less than 1×10, more preferably 11 cm -3 or less, more preferably 1 × 10 10 cm -3Less than 1 x 10 -9 cm -3 The above is the case. Note that in order to reduce the carrier concentration of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, a semiconductor having a low impurity concentration and a low density of defect states is referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor. Note that an oxide semiconductor having a low carrier concentration may also be referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor.

[0152] Furthermore, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states may also be low.

[0153] Furthermore, charges trapped in the trap states of an oxide semiconductor take a long time to dissipate and may behave like fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0154] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. Furthermore, in order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the adjacent film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0155] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0156] When an oxide semiconductor contains silicon or carbon, which is one of the Group 14 elements, defect levels are formed in the oxide semiconductor. Therefore, the concentrations of silicon and carbon in the channel formation region of the oxide semiconductor and the silicon or carbon near the interface with the channel formation region of the oxide semiconductor (concentrations obtained by secondary ion mass spectrometry (SIMS)) are calculated to be 2×10 18atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0157] Furthermore, when an oxide semiconductor contains an alkali metal or alkaline earth metal, defect states may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or alkaline earth metal is likely to have normally-on characteristics. For this reason, when the concentration of the alkali metal or alkaline earth metal in the channel formation region of the oxide semiconductor obtained by SIMS is set to 1×10 18 atoms / cm 3 Less than or equal to 2 x 10 16 atoms / cm 3 Do the following:

[0158] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Alternatively, when nitrogen is contained in an oxide semiconductor, trap states may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in the channel formation region of an oxide semiconductor obtained by SIMS is set to 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 Less than 1×10, more preferably 18 atoms / cm 3 Less than 5 × 10, more preferably 17 atoms / cm 3 Do the following:

[0159] Furthermore, hydrogen contained in an oxide semiconductor may react with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. Furthermore, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce the amount of hydrogen in the channel formation region of the oxide semiconductor as much as possible. Specifically, the hydrogen concentration measured by SIMS in the channel formation region of the oxide semiconductor is 1×10 20 atoms / cm 3 Less than 5 x 10 19 atoms / cm 3 less than 1×10 19 atoms / cm 3 less than 5×10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 Make it less than.

[0160] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0161] <Other semiconductor materials> The semiconductor material that can be used for the semiconductor layer of a transistor is not limited to the above-mentioned metal oxides. A semiconductor material having a band gap (a semiconductor material that is not a zero-gap semiconductor) may also be used for the semiconductor layer. For example, a semiconductor of a simple element such as silicon, a compound semiconductor such as gallium arsenide, or a layered material that functions as a semiconductor (also called an atomic layer material or a two-dimensional material) is preferably used as the semiconductor material. In particular, a layered material that functions as a semiconductor is preferably used as the semiconductor material.

[0162] In this specification and the like, a layered material is a general term for a group of materials having a layered crystal structure. A layered crystal structure is a structure in which layers formed by covalent or ionic bonds are stacked via bonds weaker than covalent or ionic bonds, such as van der Waals forces. A layered material has high electrical conductivity within a unit layer, that is, high two-dimensional electrical conductivity. By using a material that functions as a semiconductor and has high two-dimensional electrical conductivity in the channel formation region, a transistor with a large on-current can be provided.

[0163] Layered materials include graphene, silicene, and chalcogenides. Chalcogenides are compounds containing chalcogen. Chalcogen is a general term for elements in Group 16, including oxygen, sulfur, selenium, tellurium, polonium, and livermorium. Chalcogenides also include transition metal chalcogenides and Group 13 chalcogenides.

[0164] For example, it is preferable to use a transition metal chalcogenide that functions as a semiconductor as the semiconductor layer of the transistor.Specific examples of transition metal chalcogenides that can be used as the semiconductor layer include molybdenum sulfide (typically MoS2), molybdenum selenide (typically MoSe2), molybdenum tellurium (typically MoTe2), tungsten sulfide (typically WS2), tungsten selenide (typically WSe2), tungsten tellurium (typically WTe2), hafnium sulfide (typically HfS2), hafnium selenide (typically HfSe2), zirconium sulfide (typically ZrS2), and zirconium selenide (typically ZrSe2).

[0165] [Variation 1] 2 shows a cross section of a display device 100A, which is a modified example of the display device 100. The display device 100A has an insulating layer 122, colored layers 131 (colored layers 131R, 131G, and 131B), a light-shielding layer 132, an insulating layer 133, and the like provided on a substrate 121. The insulating layer 133 may also function as a planarizing layer.

[0166] The colored layer 131R has a function of transmitting the red color gamut, the colored layer 131G has a function of transmitting the green color gamut, and the colored layer 131B has a function of transmitting the blue color gamut. When the colored layer 131 and the light-shielding layer 132 are provided, an area where the colored layer 131 and the light-shielding layer 132 overlap each other is formed around the colored layer 131.

[0167] Furthermore, the colored layer 131R has an area overlapping with the light-emitting element 170R, the colored layer 131G has an area overlapping with the light-emitting element 170G, and the colored layer 131B has an area overlapping with the light-emitting element 170B. By providing the colored layer 131 and the light-emitting element 170 overlapping with each other, the color purity of the light 175 can be increased.

[0168] [Variation 2] 3 shows a cross section of a display device 100B, which is a modified example of the display device 100. The display device 100B has a microlens array 245 superimposed on the display device 100. The microlens array 245 condenses light 175 emitted from the light-emitting element 170. This can increase the light extraction efficiency of the display device.

[0169] [Variation 3] 4 shows a cross section of a display device 100C, which is a modified example of the display device 100. The display device 100C has a configuration that combines the display device 100A and the display device 100B. By using both the colored layer 131 and the microlens array 245, a display device with higher display quality can be realized.

[0170] [Variation 4] The display device 100 is not limited to a top-emission type display device, but may also be a bottom-emission type display device. Fig. 5 shows a cross section of a display device 100D, which is a modified example of the display device 100. The display device 100D is a bottom-emission type display device having a light-emitting element 170 with a bottom-emission structure.

[0171] The light emitting element 170 of the bottom emission structure has an electrode 171 made of a conductive material that transmits visible light, and an electrode 173 made of a conductive material that reflects visible light.

[0172] It is also possible to use a light-emitting element with a dual emission structure (dual emission structure) as the light-emitting element 170. When the light-emitting element 170 is a light-emitting element with a dual emission structure, both the electrode 171 and the electrode 173 may be made of a conductive material that transmits visible light.

[0173] [Variation 5] A cross section of a display device 100E, which is a modification of the display device 100, is shown in FIG.

[0174] The display device 100E includes an LDR 180 (Low Dielectric Constant Region) that is a region with a low relative dielectric constant between two adjacent light-emitting elements 170. More specifically, the LDR 180 (also referred to as the "first region") is provided between two adjacent EL layers 172. The LDR 180 is adjacent to a side surface of the EL layer 172 with the insulating layer 115 interposed therebetween. The LDR 180 and the insulating layer 115 are covered with the insulating layer 127.

[0175] In the display device 100E, it is preferable that the side surfaces of the EL layer 172 have an inverse tapered shape. Here, "the side surfaces of the EL layer 172 have an inverse tapered shape" refers to a shape in which the taper angle θ between the bottom surface of the EL layer 172 and the side surfaces of the EL layer 172 exceeds 90 degrees.

[0176] The LDR 180 and the inversely tapered shape of the side surface of the EL layer 172 will be explained later.

[0177] <<Example of manufacturing method>> An example of a manufacturing method of the display device 100 will be described with reference to the drawings. In this embodiment, the manufacturing method will be described with a focus on the display region 235.

[0178] The insulating layers, semiconductor layers, and conductive layers for forming electrodes and wiring that constitute the display device can be formed using a sputtering method, a chemical vapor deposition (CVD) method, a vacuum deposition method, a pulsed laser deposition (PLD) method, an atomic layer deposition (ALD) method, a plasma enhanced ALD (PEALD) method, or the like. The CVD method may be a plasma enhanced chemical vapor deposition (PECVD) method or a thermal CVD method. An example of a thermal CVD method is a metal organic chemical vapor deposition (MOCVD) method.

[0179] Furthermore, insulating layers, semiconductor layers, and conductive layers for forming electrodes and wiring that constitute the display device may be formed by methods such as spin coating, dipping, spray coating, inkjet printing, dispensing, screen printing, offset printing, slit coating, roll coating, curtain coating, and knife coating.

[0180] The PECVD method can produce high-quality films at relatively low temperatures. When using a film formation method that does not use plasma during film formation, such as the MOCVD method, ALD method, or thermal CVD method, damage to the surface on which the film is formed is less likely to occur. For example, wiring, electrodes, elements (transistors, capacitors, etc.) included in a semiconductor device may become charged up by receiving electric charge from the plasma. In this case, the accumulated electric charge may destroy the wiring, electrodes, elements, etc. included in the semiconductor device. On the other hand, film formation methods that do not use plasma do not cause such plasma damage, which can increase the yield of semiconductor devices. Furthermore, since plasma damage does not occur during film formation, films with fewer defects can be obtained.

[0181] Unlike film formation methods in which particles emitted from a target or the like are deposited, CVD and ALD are film formation methods in which a film is formed by a reaction on the surface of the workpiece. Therefore, these film formation methods are less affected by the shape of the workpiece and have good step coverage. In particular, ALD has excellent step coverage and excellent thickness uniformity, making it suitable for coating the surface of openings with high aspect ratios. However, because ALD has a relatively slow film formation rate, it may be preferable to use it in combination with other film formation methods, such as CVD, which has a faster film formation rate.

[0182] The CVD method and the ALD method can control the composition of the resulting film by adjusting the flow rate ratio of the source gases. For example, the CVD method and the ALD method can form a film of any composition by adjusting the flow rate ratio of the source gases. Furthermore, for example, the CVD method and the ALD method can form a film with a continuously changing composition by changing the flow rate ratio of the source gases while forming the film. When forming a film while changing the flow rate ratio of the source gases, the time required for film formation can be shortened by the time required for transport and pressure adjustment compared to when forming a film using multiple film formation chambers. Therefore, the productivity of semiconductor devices can sometimes be improved.

[0183] When forming a film by the ALD method, it is preferable to use a gas that does not contain chlorine as a source gas.

[0184] When forming an oxide semiconductor by sputtering, the chamber of the sputtering device is maintained at a high vacuum (5×10) using an adsorption-type vacuum exhaust pump such as a cryopump to remove water and other impurities that may be present in the oxide semiconductor as much as possible. -7 Pa to 1 x 10 -4 In particular, when the sputtering device is in standby mode, it is preferable to evacuate the chamber to a partial pressure of 1×10 Pa or less of the gas molecules corresponding to HO (gas molecules corresponding to m / z=18). -4 Pa or less, and 5×10 -5The film formation temperature is preferably RT or higher and 500°C or lower, more preferably RT or higher and 300°C or lower, and even more preferably RT or higher and 200°C or lower.

[0185] In addition, the sputtering gas must be highly purified. For example, oxygen gas and argon gas used as sputtering gases must be highly purified to have a dew point of −40° C. or lower, preferably −80° C. or lower, more preferably −100° C. or lower, and even more preferably −120° C. or lower, to prevent moisture and other contaminants from being introduced into the oxide semiconductor film as much as possible.

[0186] When an insulating layer, a conductive layer, a semiconductor layer, or the like is formed by sputtering, oxygen can be supplied to the layer to be formed by using a sputtering gas containing oxygen. The more oxygen contained in the sputtering gas, the more oxygen is likely to be supplied to the layer to be formed.

[0187] When processing a layer (thin film) constituting a display device, it can be processed using a photolithography method or the like. Alternatively, an island-shaped layer may be formed by a film formation method using a masking mask. Alternatively, the layer may be processed by a nanoimprint method, a sandblasting method, a lift-off method or the like. Photolithography methods include a method in which a resist mask is formed on the layer (thin film) to be processed, and a method in which a portion of the layer (thin film) is selectively removed using the resist mask as a mask, and then the resist mask is removed, and a method in which a photosensitive layer is formed, and then the layer is processed into a desired shape by exposure and development.

[0188] When light is used in photolithography, the light used for exposure may be, for example, i-line (wavelength 365 nm), g-line (wavelength 436 nm), h-line (wavelength 405 nm), or a mixture of these. Other light sources that can be used include ultraviolet light, KrF laser light, and ArF laser light. Exposure may also be performed using immersion exposure technology. Extreme ultraviolet (EUV) light or X-rays may also be used as the light used for exposure. Electron beams may also be used instead of light used for exposure. Extreme ultraviolet light, X-rays, or electron beams are preferred because they enable extremely fine processing. When exposure is performed by scanning a beam such as an electron beam, a photomask is not required.

[0189] The layer (thin film) can be removed (etched) by dry etching, wet etching, etc. These etching methods may also be used in combination.

[0190] The display device 100 is fabricated by combining an element substrate 151 (see FIG. 12C) and a substrate 121.

[0191] [Element substrate 151] An example of a method for manufacturing the element substrate 151 will be described.

[0192] [Process 1] An insulating layer 112 is formed over the substrate 111 (see FIG. 7A). The insulating layer 112 may be a stack of multiple insulating layers. For example, the insulating layer 112 may be an inorganic insulating film such as a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, or an aluminum nitride film. Alternatively, an inorganic insulating film such as a hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, or a neodymium oxide film may be used. Alternatively, two or more of the above insulating films may be stacked. For the insulating layer 112, a material that is difficult for impurities such as hydrogen and water to permeate may be used.

[0193] The inorganic insulating film is preferably formed at a high temperature because the higher the film formation temperature, the denser and more highly effective the film becomes. The substrate temperature during film formation of the inorganic insulating film is preferably from room temperature (25°C) to 350°C, more preferably from 100°C to 300°C.

[0194] [Process 2] Next, a transistor 251 is formed on the insulating layer 112 (see FIG. 7B).

[0195] [Process 3] Next, the insulating layer 113, the insulating layer 210, and the insulating layer 213 are formed over the transistor 251 (see FIG. 7C). When the transistor 251 is an OS transistor, the insulating layer 113 and the insulating layer 210 are preferably insulating layers from which oxygen is released by heating (hereinafter also referred to as "insulating layers containing excess oxygen").

[0196] In this specification and elsewhere, oxygen released from a layer due to heating is referred to as "excess oxygen." An insulating layer containing excess oxygen is one in which the amount of desorbed oxygen, converted into oxygen atoms, is 1.0 × 10 or more in TDS analysis performed during heat treatment at a surface temperature of the insulating layer of 100°C or more and 700°C or less, preferably 100°C or more and 500°C or less. 18 atoms / cm 3 That's it, 1.0 x 10 19 atoms / cm 3 or more, or 1.0×10 20 atoms / cm 3 It may be more than that.

[0197] The insulating layer 213 is preferably formed using a material that is impermeable to impurities such as hydrogen and water, similar to the insulating layer 112. When the insulating layer 113 and the insulating layer 210 contain excess oxygen, the insulating layer 213 is preferably formed using an insulating material that is impermeable to oxygen diffusion and permeation.

[0198] When the insulating layer 113 and the insulating layer 210 are insulating layers containing excess oxygen, heat treatment can be performed on the insulating film that does not easily diffuse or transmit oxygen, thereby efficiently supplying oxygen to the oxide semiconductor layer constituting the OS transistor. As a result, oxygen vacancies in the oxide semiconductor layer and defects at the interface between the oxide semiconductor layer and the insulating layer can be repaired, and defect levels can be reduced. This makes it possible to realize a highly reliable transistor. Furthermore, by using the transistor in a display device, the reliability of the display device can be improved.

[0199] [Step 4] Next, the insulating layer 114 is formed (see FIG. 7D). The insulating layer 114 is a layer that will become the surface on which display elements will be formed later, and therefore preferably functions as a planarizing layer.

[0200] [Step 5] Next, an opening 161 is formed in the insulating layer 114, the insulating layer 213, and the insulating layer 210, reaching the transistor 251 (see FIG. 7D).

[0201] [Step 6] Next, electrode 171 is formed on insulating layer 114 (see FIGS. 8A and 8B). FIG. 8A is a schematic perspective view showing a structure provided above insulating layer 114. To facilitate understanding of the description disclosed in this embodiment, some components are omitted from FIG. 8A. For example, components located below electrode 171 are omitted. The same applies to FIGS. 8C, 9B, 11A, 12B, and 13B, which will be described later.

[0202] In addition, in drawings and the like, arrows indicating the X, Y, and Z directions may be used. In this specification and the like, the "X direction" refers to the direction along the X axis, and no distinction is made between the forward and reverse directions unless explicitly stated. The same applies to the "Y direction" and "Z direction." The X, Y, and Z directions are directions that intersect with each other. More specifically, the X, Y, and Z directions are directions that are perpendicular to each other. In this specification and the like, one of the X, Y, and Z directions may be referred to as the "first direction" or "first direction." The other may be referred to as the "second direction" or "second direction." The remaining one may be referred to as the "third direction" or "third direction." In Figure 8 and the like, the direction perpendicular to the surface of the substrate 111 is referred to as the Z direction.

[0203] Fig. 8B is a cross-sectional schematic diagram of the XZ plane overlapping with portions F1 and F2 indicated by dashed dotted lines in Fig. 8A, as viewed in the Y direction. An electrode 171 is electrically connected to one of the source and drain of the OS transistor.

[0204] Since the display device 100 is a top-emission display device, the electrode 171 is formed using a conductive material that reflects visible light. When the electrode 171 is used as an anode, the electrode 171 may have a laminated structure of, for example, ITO and silver. Alternatively, the electrode 171 may have a laminated structure in which silver is sandwiched between two layers of ITO.

[0205] [Step 7] Next, the EL layer 172R is formed. In this embodiment, the EL layer 172R is formed of an organic EL. The EL layer 172R can be formed by a method such as a vapor deposition method, a coating method, a printing method, or a discharge method. It is preferable that the process performed after the formation of the EL layer 172R be performed so that the temperature applied to the EL layer 172R is equal to or lower than the heat resistance temperature of the EL layer 172R.

[0206] [Step 8] Next, the electrode 173R is formed. The electrode 173R is formed using a conductive material that transmits visible light. When the electrode 173R is used as a cathode, the electrode 173R may have a stacked structure of lithium fluoride and ITO, for example.

[0207] [Step 9] Next, the protective layer 126R is formed. The protective layer 126R is formed using a material that transmits visible light. For example, the protective layer 126R can be made of a material such as silicon oxide, silicon nitride, aluminum oxide, or an oxide semiconductor. The protective layer 126R may have a single-layer structure or a stacked-layer structure. For example, the protective layer 126R may have a stacked-layer structure of aluminum oxide and silicon nitride, or a stacked-layer structure of an oxide semiconductor (e.g., IGZO) and aluminum oxide.

[0208] The protective layer 126R can be formed by, for example, sputtering, ALD (thermal ALD, PEALD), or vacuum deposition. It is preferable to form the protective layer 126R by a method that causes less damage to the underlying EL layer. Therefore, it is preferable to form the protective layer 126R by ALD or vacuum deposition rather than sputtering.

[0209] Note that protective layers 126G and 126B, which will be described later, are similar to the protective layer 126R.

[0210] [Step 10] Next, a resist mask 179R is formed on the protective layer 126R (see FIGS. 8C and 8D). Fig. 8C is a schematic perspective view showing the state in which the resist mask 179R is formed on the electrode 173. Fig. 8D is a schematic cross-sectional view of the XZ plane overlapping with the portions F1 and F2 indicated by the dashed dotted lines in Fig. 8C, as viewed in the Y direction.

[0211] [Step 11] Next, using the resist mask as a mask, portions of the protective layer 126R, the electrode 173R, and the EL layer 172R are selectively removed (see FIG. 9A). FIG. 9A is a schematic cross-sectional view showing the state after the etching process. After the etching process is completed, the resist mask 179R is removed. The resist mask 179R may be removed by dry etching, wet etching, or the like. These etching methods may also be used in combination.

[0212] [Step 12] Next, the EL layer 172G is formed (see FIGS. 9B and 9C). FIG. 9B is a schematic perspective view showing a structure provided above the insulating layer 114. FIG. 9C is a schematic cross-sectional view of the XZ plane overlapping with the portions F1 and F2 indicated by the dashed dotted lines in FIG. 9B, viewed in the Y direction. In this embodiment, the EL layer 172G is formed of an organic EL. The EL layer 172G can be formed by a method such as a vapor deposition method, a coating method, a printing method, or a discharge method. It is preferable that the process performed after the formation of the EL layer 172G be performed so that the temperature applied to the EL layer 172G is equal to or lower than the heat resistance temperature of the EL layer 172R and the EL layer 172G.

[0213] [Step 13] Next, the electrode 173G is formed. The electrode 173G is formed using a conductive material that transmits visible light. When the electrode 173G is used as a cathode, the electrode 173G may have a stacked structure of lithium fluoride and ITO, for example.

[0214] [Step 14] Next, the protective layer 126G is formed using a material that transmits visible light.

[0215] [Step 15] Next, a resist mask 179G is formed on the protective layer 126G (see FIG. 10A).

[0216] [Step 16] Next, using a resist mask as a mask, portions of the protective layer 126G, the electrode 173G, and the EL layer 172G are selectively removed (see FIG. 10B). FIG. 10B is a schematic cross-sectional view showing the state after etching. At this time, the etching is performed so as not to etch the electrode 173R and the EL layer 172R. For example, after etching the protective layer 126G, the etching conditions can be switched to those that allow etching of the electrode 173G and the EL layer 172G but do not easily etch the protective layer 126R. After the etching is completed, the resist mask 179G is removed (see FIG. 10C). The resist mask 179G can be removed by dry etching, wet etching, or the like. These etching methods may also be used in combination.

[0217] [Step 17] Next, the EL layer 172B is formed (see FIGS. 11A and 11B). FIG. 11A is a schematic perspective view showing a structure provided above the insulating layer 114. FIG. 11B is a schematic cross-sectional view of the XZ plane overlapping with the portions F1 and F2 indicated by the dashed dotted lines in FIG. 11A, viewed in the Y direction. In this embodiment, the EL layer 172B is formed of an organic EL. The EL layer 172B can be formed by a method such as a vapor deposition method, a coating method, a printing method, or a discharge method. It is preferable that the process performed after the formation of the EL layer 172B be performed so that the temperature applied to the EL layer 172B is equal to or lower than the heat resistance temperature of the EL layer 172R, the EL layer 172G, and the EL layer 172B.

[0218] [Step 18] Next, the electrode 173B is formed. The electrode 173B is formed using a conductive material that transmits visible light. When the electrode 173B is used as a cathode, the electrode 173B may have a stacked structure of lithium fluoride and ITO, for example.

[0219] [Step 19] Next, the protective layer 126B is formed using a material that transmits visible light.

[0220] [Step 20] Next, a resist mask 179B is formed on the protective layer 126B (see FIG. 10C).

[0221] [Step 21] Next, using a resist mask as a mask, portions of the protective layer 126B, the electrode 173B, and the EL layer 172B are selectively removed (see FIG. 12A). FIG. 12A is a schematic cross-sectional view showing the state after etching. At this time, the etching is performed so as not to etch the electrode 173R, the EL layer 172R, the electrode 173G, and the EL layer 172G. For example, after etching the protective layer 126B, the etching conditions can be switched to those that allow etching of the electrode 173B and the EL layer 172B but do not easily etch the protective layer 126R and the protective layer 126G. After the etching is completed, the resist mask 179B is removed. The resist mask 179B can be removed by dry etching, wet etching, or the like. These etching methods may also be used in combination.

[0222] [Step 22] Next, using the protective layer 126 (protective layer 126R, protective layer 126G, protective layer 126B) as a mask, a portion of the electrode 171 is selectively removed. Fig. 12B is a schematic perspective view showing a structure provided above the insulating layer 114. Fig. 12C is a schematic cross-sectional view of the XZ plane overlapping with the portions F1 and F2 indicated by the dashed dotted lines in Fig. 12B, viewed in the Y direction.

[0223] By selectively removing portions of electrode 171 using protective layer 126 as a mask, electrode 171R overlapping protective layer 126R, electrode 171G overlapping protective layer 126G, and electrode 171B overlapping protective layer 126B are formed. When portions of electrode 171 are selectively removed, a portion of insulating layer 114 may also be removed, forming a recess in that portion of insulating layer 114. Note that step 22 may be performed before removing resist mask 179B.

[0224] Furthermore, according to the above-described manufacturing method, it is possible to make the side surfaces of the electrode 171, the EL layer 172, and the electrode 173 approximately coincident with each other. Making the side surfaces of the electrode 171, the EL layer 172, and the electrode 173 approximately coincident with each other is preferable because it improves the coverage of an insulating layer or the like in a later step.

[0225] In this manner, the light emitting elements 170 (light emitting elements 170R, 170G, and 170B) can be formed.

[0226] By forming the light-emitting element 170 by etching using a resist mask, electrical interference between adjacent light-emitting layers can be prevented without using a partition. Therefore, the formation of a partition is unnecessary, and the productivity of the display device can be improved. Furthermore, since the formation of a partition is unnecessary, an improvement in pixel aperture ratio, high definition, and miniaturization can be realized.

[0227] According to one embodiment of the present invention, a light-emitting element that functions as a pixel can be formed separately by selectively removing parts of the electrode 171, the EL layer 172, and the electrode 173 using a resist mask. Therefore, a light-emitting element can be formed without using a metal mask or with a reduced amount of metal mask used, thereby improving the productivity of the display device.

[0228] For example, when the light-emitting elements 170 are formed using a metal mask, it is difficult to make the shortest distance between the light-emitting elements 170 20 μm or less due to constraints on dimensional accuracy. According to one embodiment of the present invention, the shortest distance between adjacent light-emitting elements 170 can be made 20 μm or less. Specifically, the distance between adjacent light-emitting elements 170 can be made 0.1 μm or more and 15 μm or less, preferably 0.1 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less. This makes it possible to achieve an improved pixel aperture ratio, higher definition, and smaller size.

[0229] [Step 23] Next, an insulating layer 115 is formed to cover the light-emitting element 170 (see FIG. 13A). For the insulating layer 115, a material that does not easily diffuse impurities such as water and hydrogen is preferably used. This allows the insulating layer 115 to function as a barrier film. With this configuration, it is possible to effectively prevent impurities from diffusing from the outside into the light-emitting element 170 and the transistor, thereby realizing a highly reliable display device.

[0230] The insulating layer 115 may be, for example, a single layer or a stacked layer of aluminum oxide, aluminum nitride, silicon oxide, silicon nitride, hafnium oxide, zirconium oxide, or the like.

[0231] The insulating layer 115 is preferably formed by an ALD method, which has excellent step coverage. By forming the insulating layer 115 by an ALD method, the side surfaces of the electrode 171, the EL layer 172, and the electrode 173 can be covered with the insulating layer 115.

[0232] [Step 24] Next, an insulating layer 116 is formed over the insulating layer 115. The insulating layer 116 preferably functions as a planarization layer.

[0233] [Step 25] Next, an electrode 117 is formed so as to be embedded in the insulating layer 115 and the insulating layer 116. The electrode 117 is provided for each light-emitting element 170 and is electrically connected to the electrode 173. The number of electrodes 117 provided for each light-emitting element 170 is not limited to one. A plurality of electrodes 117 may be provided for one light-emitting element 170.

[0234] [Step 26] Next, conductive layer 118 is formed on insulating layer 116 and electrode 117 (see FIGS. 13B and 13C). Fig. 13B is a schematic perspective view showing a state in which conductive layer 118 is provided on light-emitting element 170. Fig. 13C is a schematic cross-sectional view of the XZ plane overlapping portions F1 and F2 indicated by dashed dotted lines in Fig. 13B, as viewed in the Y direction.

[0235] The conductive layer 118 is electrically connected to the electrodes 173 of the light-emitting elements 170 and functions as a common electrode. Furthermore, by forming the conductive layer 118 using a light-transmitting conductive material, light 175 emitted from the light-emitting elements 170 can be extracted without being blocked. Therefore, the conductive layer 118 can be provided to cover the light-emitting elements 170. That is, the conductive layer 118 can be provided to cover the entire display region 235.

[0236] The conductive layer 118 can function as a cathode auxiliary conductive layer. By providing the conductive layer 118, the potential variation of the cathode (electrode 173) in the entire display area 235 is reduced, and uniform luminescence intensity is obtained. Therefore, the display quality of the display device can be improved.

[0237] In this manner, the element substrate 151 can be fabricated.

[0238] [Variation 1] Fig. 14 shows a modified example of the element substrate 151. In the element substrate 151, wiring 119 may be provided on the insulating layer 116 and the electrode 117 instead of the conductive layer 118. Fig. 14A is a schematic perspective view showing a state in which wiring 119 is provided on the light-emitting element 170. Fig. 14B is a schematic cross-sectional view of the XZ plane overlapping with the portions F1 and F2 indicated by the dashed dotted lines in Fig. 14A, viewed in the Y direction.

[0239] The wiring 119 can be formed using a conductive material that is light-transmitting or light-blocking. When the wiring 119 is formed using a material that blocks light, it is preferable to arrange the wiring 119 so that the area that overlaps with the light-emitting element 170 is as small as possible. The wiring 119 can function as a cathode auxiliary wiring. By electrically connecting the cathodes of the adjacent light-emitting elements to the wiring 119, it is possible to reduce potential variations in the cathodes. This can improve the display quality of the display device.

[0240] 14, the wiring 119 extends in the X direction and is electrically connected to the electrodes 117 adjacent in the X direction, but the wiring 119 may extend in the Y direction and be electrically connected to the electrodes 117 adjacent in the Y direction. The wiring 119 may also be arranged in a mesh pattern.

[0241] [Variation 2] 15A, an insulating layer 139 may be provided between the insulating layer 114 and the electrode 171. The insulating layer 139 is made of a material that is less susceptible to etching in step 22 than the insulating layer 114. The insulating layer 139 can function as an etching stopper when part of the electrode 171 is etched in step 22.

[0242] In particular, when step 22 is performed by dry etching or is performed mainly by dry etching, it is preferable to provide insulating layer 139. By providing insulating layer 139 that has higher etching resistance than insulating layer 114, the degree of freedom in the process design of step 22 is increased, and productivity and reliability can be improved.

[0243] [Variation 3] 15B, the conductive layer 118 and the electrode 173 may be electrically connected without providing the electrode 117. By not providing the electrode 117, the manufacturing process can be simplified, and the productivity of the display device can be increased.

[0244] [Variation 4] When a microcavity structure is not applied to light emitting element 170, the distance between electrode 171 and electrode 173 of light emitting element 170R, light emitting element 170G, and light emitting element 170B may be set to be approximately the same as each other, as shown in FIG. 15C.

[0245] [Variation 5] Next, a method for manufacturing a display device 100E (see FIG. 6) in which the side surfaces of the EL layer 172 have an inversely tapered shape will be described. After selectively removing a portion of the electrode 171 in step 22, the etching conditions are changed to etch the side surfaces of the EL layer 172 (see FIG. 16A). The etching of the side surfaces of the EL layer 172 is preferably performed by a dry etching method. The side surface shape of the EL layer 172 can be controlled by the dry etching conditions and the distance between adjacent light-emitting elements 170.

[0246] Subsequently, step 23 is performed to form an insulating layer 115 that covers the side surfaces of the electrode 171, the EL layer 172, and the electrode 173 (see FIG. 16B).

[0247] After the insulating layer 115 is formed, an insulating layer 127 is formed on the insulating layer 115 (see FIG. 16C). The insulating layer 127 is formed by sputtering, CVD, or the like under conditions that result in poor coverage. Sputtering is particularly preferred because it is easy to form a film under conditions that result in poor coverage. For example, a silicon nitride layer may be formed by sputtering as the insulating layer 127. By forming the insulating layer 127, an LDR 180 is formed between two adjacent light-emitting elements 170.

[0248] LDR 180 is a gap surrounded by insulating layer 115 and insulating layer 127. Therefore, the relative dielectric constant of LDR 180 can be set to 1 or close to 1. Furthermore, LDR 180 may contain some gas. Furthermore, when insulating layer 127 is formed under reduced pressure, at least a portion of LDR 180 may be in a reduced pressure state. For example, when insulating layer 127 is formed by sputtering, there is a possibility that the LDR 180 may contain elements used in the sputtering gas. For example, it may contain Group 18 elements (rare gases (noble gases)), nitrogen, oxygen, etc.

[0249] The LDR 180 may be left as a gap, or the LDR 180 may be provided with a structure having a refractive index smaller than that of the insulating layer 115. For example, the LDR 180 may be filled with a resin containing fluorine. By providing a structure in the LDR 180, the mechanical strength of the element substrate 151 can be increased.

[0250] By providing the LDR 180 on the side surface of the EL layer 172 via the insulating layer 115, part of the light 175 generated in the EL layer 172 is reflected at the interface between the insulating layer 115 and the LDR 180 (see FIG. 17A). Note that another part of the light 175 may be reflected at the interface between the EL layer 172 and the insulating layer 115.

[0251] By forming the side surfaces of the EL layer 172 in an inverse tapered shape, a part of the light 175 generated in the EL layer 172 can be reflected upward. This increases the extraction efficiency of the light 175, thereby increasing the brightness of the display device 100.

[0252] The taper angle θ between the bottom surface of the EL layer 172 and the side surface of the EL layer 172 is preferably more than 90° and not more than 100°, more preferably more than 90° and not more than 120°, and even more preferably more than 90° and not more than 135°.

[0253] The side surface of the EL layer 172 may be convex as shown in FIG. 17B or concave as shown in FIG. 17C or 17D. In the shapes shown in FIGS. 17B and 17C, the area where the EL layer 172 contacts the electrode 173 is larger than the area where the EL layer 172 contacts the electrode 171. In FIG. 17D, the area where the EL layer 172 contacts the electrode 171 is the same as the area where the EL layer 172 contacts the electrode 173, but part of the side surface of the EL layer 172 is constricted. Therefore, it is sufficient that at least part of the side surface of the EL layer 172 has an inverse tapered shape.

[0254] Specifically, when the EL layer 172 is viewed in the X or Y direction, it is preferable that at least one-third of the side surfaces of the EL layer 172 have a taper angle θ within the above numerical range. It is more preferable that at least half of the side surfaces of the EL layer 172 have a taper angle θ within the above numerical range when the EL layer 172 is viewed in the X or Y direction.

[0255] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes.

[0256] (Embodiment 2) In this embodiment, a more specific configuration example of display device 100 will be described. Fig. 19A is a block diagram illustrating display device 100. As described in the first embodiment, display device 100 has display area 235, peripheral circuit area 232, and peripheral circuit area 233.

[0257] The circuits included in the peripheral circuit region 232 function as, for example, a scanning line driving circuit. The circuits included in the peripheral circuit region 232 function as, for example, a signal line driving circuit. Note that some kind of circuit may be provided at a position facing the peripheral circuit region 232 across the display region 235. Note that some kind of circuit may be provided at a position facing the peripheral circuit region 233 across the display region 235. Note that, as mentioned above, the circuits included in the peripheral circuit region 232 and the peripheral circuit region 233 may be collectively referred to as a "peripheral driving circuit."

[0258] The peripheral driver circuit can include various circuits such as a shift register, a level shifter, an inverter, a latch, an analog switch, and a logic circuit. The peripheral driver circuit can include a transistor, a capacitor, and the like. The transistors included in the peripheral driver circuit can be formed in the same process as the transistors included in the pixel 230.

[0259] The display device 100 also has m wires 236 that are arranged approximately in parallel and whose potential is controlled by a circuit included in the peripheral circuit region 232, and n wires 237 that are arranged approximately in parallel and whose potential is controlled by a circuit included in the peripheral circuit region 233.

[0260] The display region 235 has a plurality of pixels 230 arranged in a matrix. A pixel 230 that controls red light, a pixel 230 that controls green light, and a pixel 230 that controls blue light are collectively configured to function as a single pixel 240, and full-color display can be achieved by controlling the light emission amount (light emission brightness) of each pixel 230. Thus, each of the three pixels 230 functions as a sub-pixel. That is, each of the three sub-pixels controls the light emission amount of red light, green light, or blue light (see FIG. 19B1). Note that the color of light controlled by each of the three sub-pixels is not limited to a combination of red (R), green (G), and blue (B), but may also be cyan (C), magenta (M), or yellow (Y) (see FIG. 19B2).

[0261] Furthermore, four subpixels may be combined to function as one pixel. For example, a subpixel that controls white light may be added to three subpixels that control red, green, and blue light, respectively (see FIG. 19B3). Adding a subpixel that controls white light can increase the brightness of the display area. A subpixel that controls yellow light may be added to three subpixels that control red, green, and blue light, respectively (see FIG. 19B4). A subpixel that controls white light may be added to three subpixels that control cyan, magenta, and yellow light, respectively (see FIG. 19B5).

[0262] By increasing the number of sub-pixels that function as one pixel and by appropriately combining sub-pixels that control red, green, blue, cyan, magenta, and yellow light, it is possible to improve the reproducibility of intermediate tones, thereby improving display quality.

[0263] The display device of one embodiment of the present invention can reproduce color gamuts of various standards, such as the PAL (Phase Alternating Line) standard and the NTSC (National Television System Committee) standard used in television broadcasting, the sRGB (standard RGB) standard and the Adobe RGB standard widely used in display devices used in electronic devices such as personal computers, digital cameras, and printers, the ITU-R BT.709 (International Telecommunication Union Radiocommunication Sector Broadcasting Service (Television) 709) standard used in HDTV (High Definition Television, also called Hi-Vision), the DCI-P3 (Digital Cinema Initiatives P3) standard used in digital cinema projection, and the ITU-R BT.2020 (REC.2020 (Recommendation 2020)) standard used in UHDTV (Ultra High Definition Television, also called Super Hi-Vision).

[0264] Furthermore, by arranging the pixels 240 in a 1920 × 1080 matrix, it is possible to realize a display device 100 capable of full-color display at a resolution of so-called full high-definition (also referred to as "2K resolution," "2K1K," or "2K"). Furthermore, by arranging the pixels 240 in a 3840 × 2160 matrix, it is possible to realize a display device 100 capable of full-color display at a resolution of so-called ultra high-definition (also referred to as "4K resolution," "4K2K," or "4K"). Furthermore, by arranging the pixels 240 in a 7680 × 4320 matrix, it is possible to realize a display device 100 capable of full-color display at a resolution of so-called super high-definition (also referred to as "8K resolution," "8K4K," or "8K"). By increasing the number of pixels 240, it is also possible to realize a display device 100 capable of full-color display at a resolution of 16K or 32K.

[0265] <Circuit configuration example of pixel 230> 20A is a diagram showing an example of the circuit configuration of the pixel 230. The pixel 230 includes a pixel circuit 431 and a display element 432.

[0266] Each wiring 236 is electrically connected to n pixel circuits 431 arranged in any row among the pixel circuits 431 arranged in m rows and n columns in the display region 235. Furthermore, each wiring 237 is electrically connected to m pixel circuits 431 arranged in any column among the pixel circuits 431 arranged in m rows and n columns. Both m and n are integers of 1 or greater.

[0267] The pixel circuit 431 includes a transistor 436, a capacitor 433, a transistor 251, and a transistor 434. The pixel circuit 431 is electrically connected to a display element 432.

[0268] One of the source electrode and the drain electrode of the transistor 436 is electrically connected to a wiring (hereinafter referred to as a signal line DL_n) to which a data signal (also referred to as a "video signal") is applied. Furthermore, a gate electrode of the transistor 436 is electrically connected to a wiring (hereinafter referred to as a scanning line GL_m) to which a gate signal is applied. The signal line DL_n and the scanning line GL_m correspond to the wiring 237 and the wiring 236, respectively.

[0269] The transistor 436 has a function of controlling writing of a data signal to the node 435 .

[0270] One of a pair of electrodes of the capacitor 433 is electrically connected to a node 435, and the other electrode is electrically connected to a node 437. The other of the source electrode and the drain electrode of the transistor 436 is electrically connected to the node 435.

[0271] The capacitor 433 functions as a storage capacitor for holding data written to the node 435 .

[0272] One of the source electrode and the drain electrode of the transistor 251 is electrically connected to the potential supply line VL_a, and the other is electrically connected to a node 437. Furthermore, a gate electrode of the transistor 251 is electrically connected to a node 435.

[0273] One of the source electrode and the drain electrode of the transistor 434 is electrically connected to the potential supply line V0, and the other is electrically connected to a node 437. Furthermore, the gate electrode of the transistor 434 is electrically connected to the scan line GL_m.

[0274] One of the anode or cathode of the display element 432 is electrically connected to the potential supply line VL_b, and the other is electrically connected to a node 437 .

[0275] For example, an organic electroluminescence element (also called an organic EL element) can be used as the display element 432. However, the display element 432 is not limited to this, and for example, an inorganic EL element made of an inorganic material may also be used. Note that "organic EL element" and "inorganic EL element" may be collectively referred to as "EL element."

[0276] The luminescent color of the EL element can be white, red, green, blue, cyan, magenta, yellow, or the like, depending on the material that constitutes the EL element.

[0277] There are two methods for achieving color display: combining a display element 432 that emits white light with a colored layer, and providing a display element 432 that emits a different color for each pixel. The former method is more productive than the latter. On the other hand, the latter method requires a separate display element 432 for each pixel, making it less productive than the former method. However, the latter method can produce an emitted color with higher color purity than the former method. In addition to the latter method, the color purity can be further improved by adding a microcavity structure to the display element 432.

[0278] Both low molecular weight compounds and high molecular weight compounds, and inorganic compounds may be used for the display element 432. The layers constituting the display element 432 can be formed by a deposition method (including a vacuum deposition method), a transfer method, a printing method, an inkjet method, a coating method, or the like.

[0279] The display element 432 may include an inorganic compound such as quantum dots. For example, quantum dots can be used in a light-emitting layer to function as a light-emitting material.

[0280] The power supply potential can be, for example, a relatively high potential or a relatively low potential. The high potential is called a high power supply potential (also called "VDD"), and the low potential is called a low power supply potential (also called "VSS"). Ground potential can also be used as the high power supply potential or the low power supply potential. For example, if the high power supply potential is ground potential, the low power supply potential is a potential lower than the ground potential, and if the low power supply potential is ground potential, the high power supply potential is a potential higher than the ground potential.

[0281] For example, a high power supply potential VDD is applied to one of the potential supply line VL_a or VL_b, and a low power supply potential VSS is applied to the other.

[0282] In a display device having the pixel circuits 431 , the pixel circuits 431 in each row are sequentially selected by a circuit included in a peripheral driver circuit, and the transistors 436 and 434 are turned on to write a data signal to the node 435 .

[0283] The pixel circuit 431, in which data is written to the node 435, is put into a holding state by turning off the transistor 436 and the transistor 434. Furthermore, the amount of current flowing between the source electrode and the drain electrode of the transistor 251 is controlled in accordance with the potential of the data written to the node 435, and the display element 432 emits light with a luminance corresponding to the amount of current flowing. By performing this process sequentially for each row, an image can be displayed.

[0284] 20B shows a modified example of the circuit configuration of pixel 230 shown in FIG. 20A. The circuit configuration shown in FIG. 20B has a configuration in which transistor 434 and potential supply line V0 are removed from the circuit configuration shown in FIG. 20A. The other components can be understood by referring to the description of the circuit configuration shown in FIG. 20A. Therefore, to avoid repetition, a detailed description of the circuit configuration shown in FIG. 20B will be omitted.

[0285] Alternatively, some or all of the transistors included in the pixel circuit 431 may be transistors having back gates. For example, as shown in FIG. 20C , a transistor having a back gate may be used as the transistor 436, and the back gate and the gate may be electrically connected to each other. Alternatively, the back gate may be electrically connected to either the source or the drain of the transistor, as in the case of a transistor 251 shown in FIG. 20C .

[0286] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes.

[0287] (Embodiment 3) In this embodiment, a light-emitting element (also referred to as a light-emitting device) that can be used for a display device that is one embodiment of the present invention will be described.

[0288] <Configuration example of light-emitting element> As shown in FIG. 21A, the light-emitting element 170 has an EL layer 172 between a pair of electrodes (electrode 171 and electrode 173). The EL layer 172 can be composed of multiple layers such as a layer 4420, a light-emitting layer 4411, and a layer 4430. The layer 4420 can have, for example, a layer containing a substance with high electron-injecting properties (electron-injecting layer) and a layer containing a substance with high electron-transporting properties (electron-transporting layer). The light-emitting layer 4411 contains, for example, a light-emitting compound. The layer 4430 can have, for example, a layer containing a substance with high hole-injecting properties (hole-injecting layer) and a layer containing a substance with high hole-transporting properties (hole-transporting layer).

[0289] A structure having the layer 4420, the light-emitting layer 4411, and the layer 4430 provided between a pair of electrodes can function as a single light-emitting unit, and the structure of FIG. 21A is referred to as a single structure in this specification and the like.

[0290] 21B shows a modified example of the EL layer 172 included in the light-emitting element 170 shown in Fig. 21A. Specifically, the light-emitting element 170 shown in Fig. 21B includes a layer 4430-1 on the electrode 171, a layer 4430-2 on the layer 4430-1, a light-emitting layer 4411 on the layer 4430-2, a layer 4420-1 on the light-emitting layer 4411, a layer 4420-2 on the layer 4420-1, and an electrode 173 on the layer 4420-2. For example, when the electrode 171 is an anode and the electrode 173 is a cathode, the layer 4430-1 functions as a hole injection layer, the layer 4430-2 functions as a hole transport layer, the layer 4420-1 functions as an electron transport layer, and the layer 4420-2 functions as an electron injection layer. Alternatively, when the electrode 171 is used as a cathode and the electrode 173 is used as an anode, the layer 4430-1 functions as an electron injection layer, the layer 4430-2 functions as an electron transport layer, the layer 4420-1 functions as a hole transport layer, and the layer 4420-2 functions as a hole injection layer. By using such a layer structure, it is possible to efficiently inject carriers into the light-emitting layer 4411 and increase the efficiency of carrier recombination in the light-emitting layer 4411.

[0291] Note that a configuration in which a plurality of light-emitting layers (light-emitting layers 4411, 4412, 4413) are provided between layer 4420 and layer 4430 as shown in FIG. 21C is also an example of a single structure.

[0292] 21D, a configuration in which multiple light-emitting units (EL layer 172a, EL layer 172b) are connected in series via an intermediate layer (charge generating layer) 4440 is referred to as a tandem structure or a stack structure in this specification and elsewhere. Note that a tandem structure can realize a light-emitting element capable of emitting light with high brightness.

[0293] The light-emitting element can emit light in red, green, blue, cyan, magenta, yellow, or white, depending on the material of the EL layer 172. Furthermore, the color purity can be further improved by providing the light-emitting element with a microcavity structure.

[0294] The light-emitting layer may contain two or more light-emitting materials that emit light of R (red), G (green), B (blue), Y (yellow), O (orange), etc. It is preferable that a light-emitting element that emits white light has a configuration in which the light-emitting layer contains two or more types of light-emitting materials. To obtain white light emission, light-emitting materials can be selected such that the respective emissions of the two or more light-emitting materials have a complementary color relationship. For example, by making the emission color of the first light-emitting layer and the emission color of the second light-emitting layer complementary colors, a light-emitting element that emits white light as a whole can be obtained. The same applies to a light-emitting element having three or more light-emitting layers.

[0295] The light-emitting layer preferably contains two or more light-emitting materials that emit light of R (red), G (green), B (blue), Y (yellow), O (orange), etc. Alternatively, it is preferable that the light-emitting layer contains two or more light-emitting materials, and the light emitted by each of the light-emitting materials contains spectral components of two or more colors of R, G, and B.

[0296] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes.

[0297] (Fourth embodiment) In this embodiment, a structural example of a transistor that can be used in a display device according to one embodiment of the present invention will be described.

[0298] <Transistor configuration example 1> As an example of the structure of a transistor, a transistor 70A will be described with reference to FIGS. 22A to 22C.

[0299] FIG. 22A is a top view of transistor 70A. FIG. 22B is a cross-sectional view of the portion indicated by the dashed dotted line X1-X2 in FIG. 22A, and is also a cross-sectional view of transistor 70A in the channel length direction. FIG. 22C is a cross-sectional view of the portion indicated by the dashed dotted line Y1-Y2 in FIG. 22A, and is also a cross-sectional view of transistor 70A in the channel width direction. Note that some elements are omitted from the top view of FIG. 22A for clarity.

[0300] As shown in FIG. 22 , the transistor 70A includes a metal oxide 330a disposed on a substrate (not shown), a metal oxide 330b disposed on the metal oxide 330a, a conductor 242a and a conductor 242b disposed spaced apart from each other on the metal oxide 330b, an insulator 280 disposed on the conductors 242a and 242b and having an opening formed between the conductors 242a and 242b, a conductor 260 disposed in the opening, an insulator 250 disposed among the metal oxide 330b, the conductors 242a, 242b, and the insulator 280, and the conductor 260, and a metal oxide 330c disposed among the metal oxide 330b, the conductors 242a, 242b, the insulator 280, and the insulator 250. 22B and 22C, it is preferable that the top surface of the conductor 260 substantially coincides with the top surfaces of the insulators 250, 254, metal oxide 330c, and 280. Note that, hereinafter, the metal oxides 330a, 330b, and 330c may be collectively referred to as metal oxides 330. Furthermore, the conductors 242a and 242b may be collectively referred to as conductors 242.

[0301] In the transistor 70A shown in Fig. 22, the side surfaces of the conductors 242a and 242b facing the conductor 260 have a substantially vertical shape. Note that the transistor 70A shown in Fig. 22 is not limited to this, and the angle formed between the side surface and the bottom surface of the conductors 242a and 242b may be 10° or more and 80° or less, preferably 30° or more and 60° or less. Furthermore, the opposing side surfaces of the conductors 242a and 242b may have multiple surfaces.

[0302] 22, it is preferable that an insulator 254 be disposed between the insulator 224, the metal oxide 330a, the metal oxide 330b, the conductor 242a, the conductor 242b, and the metal oxide 330c and the insulator 280. Here, it is preferable that the insulator 254 be in contact with the side surface of the metal oxide 330c, the top and side surfaces of the conductor 242a, the top and side surfaces of the conductor 242b, the side surfaces of the metal oxide 330a and the metal oxide 330b, and the top surface of the insulator 224, as shown in FIGS.

[0303] Although the transistor 70A has a three-layer structure of the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c in and around a region where a channel is formed (hereinafter also referred to as a channel formation region), the present invention is not limited to this. For example, a two-layer structure of the metal oxide 330b and the metal oxide 330c or a stacked structure of four or more layers may be provided. Furthermore, the transistor 70A has a two-layer structure of the conductor 260, but the present invention is not limited to this. For example, the conductor 260 may have a single-layer structure or a stacked structure of three or more layers. Furthermore, each of the metal oxide 330a, the metal oxide 330b, and the metal oxide 330c may have a stacked structure of two or more layers.

[0304] For example, when metal oxide 330c has a layered structure consisting of a first metal oxide and a second metal oxide on the first metal oxide, it is preferable that the first metal oxide has a composition similar to that of metal oxide 330b, and the second metal oxide has a composition similar to that of metal oxide 330a.

[0305] Here, the conductor 260 functions as the gate electrode of the transistor, and the conductors 242a and 242b function as the source and drain electrodes, respectively. As described above, the conductor 260 is formed so as to be embedded in the opening of the insulator 280 and in the region sandwiched between the conductors 242a and 242b. Here, the arrangement of the conductors 260, 242a, and 242b is selected in a self-aligned manner with respect to the opening of the insulator 280. That is, in the transistor 70A, the gate electrode can be positioned between the source and drain electrodes in a self-aligned manner. Therefore, the conductor 260 can be formed without providing an alignment margin, thereby reducing the area occupied by the transistor 70A. This allows for a high-resolution display device. Furthermore, the display device can have a narrow frame.

[0306] As shown in FIG. 22, the conductor 260 preferably has a conductor 260a provided inside the insulator 250 and a conductor 260b provided so as to be embedded inside the conductor 260a.

[0307] Transistor 70A preferably has an insulator 214 disposed on a substrate (not shown), an insulator 216 disposed on insulator 214, a conductor 205 disposed so as to be embedded in insulator 216, an insulator 222 disposed on insulator 216 and conductor 205, and an insulator 224 disposed on insulator 222. Metal oxide 330a is preferably disposed on insulator 224.

[0308] An insulator 274 functioning as an interlayer film and an insulator 281 are preferably disposed over the transistor 70A. Here, the insulator 274 is preferably disposed in contact with the top surfaces of the conductor 260, the insulator 250, the insulator 254, the metal oxide 330c, and the insulator 280.

[0309] It is preferable that the insulators 222, 254, and 274 have a function of suppressing the diffusion of at least one of hydrogen (e.g., hydrogen atoms, hydrogen molecules, etc.). For example, it is preferable that the insulators 222, 254, and 274 have lower hydrogen permeability than the insulators 224, 250, and 280. It is also preferable that the insulators 222 and 254 have a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.). For example, it is preferable that the insulators 222 and 254 have lower oxygen permeability than the insulators 224, 250, and 280.

[0310] Here, the insulator 224, the metal oxide 330, and the insulator 250 are separated by the insulators 280 and 281, and the insulators 254 and 274. Therefore, impurities such as hydrogen contained in the insulators 280 and 281, or excess oxygen, can be prevented from being mixed into the insulators 224, the metal oxide 330a, the metal oxide 330b, and the insulator 250.

[0311] It is preferable that a conductor 340 (conductor 340a and conductor 340b) electrically connected to the transistor 70A and functioning as a plug is provided. Note that an insulator 241 (insulator 241a and insulator 241b) is provided in contact with the side surface of the conductor 340 functioning as a plug. That is, the insulator 241 is provided in contact with the inner wall of the opening of the insulators 254, 280, 274, and 281. Alternatively, a first conductor of the conductor 340 may be provided in contact with the side surface of the insulator 241, and a second conductor of the conductor 340 may be provided further inward. Here, the height of the top surface of the conductor 340 and the height of the insulator 281 can be made approximately the same. Note that, in the transistor 70A, a configuration in which the first conductor of the conductor 340 and the second conductor of the conductor 340 are stacked is described, but the present invention is not limited to this. For example, the conductor 340 may be provided as a single layer or a laminated structure of three or more layers. When the structure has a laminated structure, it may be distinguished by assigning an ordinal number to the order of formation.

[0312] In the transistor 70A, a metal oxide that functions as an oxide semiconductor (hereinafter also referred to as an oxide semiconductor) is preferably used for the metal oxide 330 (metal oxide 330a, metal oxide 330b, and metal oxide 330c) including the channel formation region. For example, a metal oxide having a band gap of 2 eV or more, preferably 2.5 eV or more, is preferably used for the channel formation region of the metal oxide 330.

[0313] The metal oxide preferably contains at least indium (In) or zinc (Zn). In particular, it is preferable that it contains indium (In) and zinc (Zn). In addition to these, it is preferable that it contains element M. As element M, one or more of aluminum (Al), gallium (Ga), yttrium (Y), tin (Sn), boron (B), titanium (Ti), iron (Fe), nickel (Ni), germanium (Ge), zirconium (Zr), molybdenum (Mo), lanthanum (La), cerium (Ce), neodymium (Nd), hafnium (Hf), tantalum (Ta), tungsten (W), magnesium (Mg), and cobalt (Co) can be used. In particular, element M is preferably one or more of aluminum (Al), gallium (Ga), yttrium (Y), and tin (Sn). Furthermore, it is more preferable that element M contains either or both of Ga and Sn.

[0314] 22B, the film thickness of the metal oxide 330b in the region that does not overlap with the conductor 242 may be thinner than the film thickness of the region that overlaps with the conductor 242. This is formed by removing a portion of the upper surface of the metal oxide 330b when forming the conductors 242a and 242b. When a conductive film that will become the conductor 242 is formed on the upper surface of the metal oxide 330b, a low-resistance region may be formed near the interface with the conductive film. In this way, by removing the low-resistance region located between the conductors 242a and 242b on the upper surface of the metal oxide 330b, it is possible to prevent a channel from being formed in that region.

[0315] According to one embodiment of the present invention, a display device having high definition and a small transistor can be provided. Alternatively, a display device having high luminance and a transistor with high on-state current can be provided. Alternatively, a display device having high-speed operation and a transistor with stable electrical characteristics can be provided. Alternatively, a display device having low power consumption and a transistor with low off-state current can be provided.

[0316] The detailed structure of the transistor 70A that can be used in the display device of one embodiment of the present invention will be described.

[0317] The conductor 205 is disposed so as to have a region overlapping with the metal oxide 330 and the conductor 260. The conductor 205 is preferably embedded in the insulator 216.

[0318] The conductor 205 includes conductor 205a, conductor 205b, and conductor 205c. The conductor 205a is provided in contact with the bottom surface and sidewall of an opening provided in the insulator 216. The conductor 205b is provided so as to be embedded in a recess formed in the conductor 205a. Here, the upper surface of the conductor 205b is lower than the upper surface of the conductor 205a and the upper surface of the insulator 216. The conductor 205c is provided in contact with the upper surface of the conductor 205b and the side surface of the conductor 205a. Here, the height of the upper surface of the conductor 205c is approximately the same as the height of the upper surface of the conductor 205a and the height of the upper surface of the insulator 216. In other words, the conductor 205b is configured to be enclosed by the conductors 205a and 205c.

[0319] The conductors 205a and 205c are preferably made of a conductive material 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 (NO, NO, NO, etc.), copper atoms, etc. Alternatively, it is preferable to use a conductive material that has a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0320] By using a conductive material capable of reducing hydrogen diffusion for the conductor 205a and the conductor 205c, it is possible to prevent impurities such as hydrogen contained in the conductor 205b from diffusing into the metal oxide 330 via the insulator 224 or the like. Furthermore, by using a conductive material capable of suppressing oxygen diffusion for the conductor 205a and the conductor 205c, it is possible to prevent the conductor 205b from being oxidized and its conductivity from decreasing. Examples of conductive materials capable of suppressing oxygen diffusion include titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Therefore, the conductor 205a may be a single layer or a multilayer of the above conductive materials. For example, the conductor 205a may be made of titanium nitride.

[0321] The conductor 205b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component, for example, tungsten.

[0322] Here, the conductor 260 may function as a first gate (also referred to as a top gate) electrode. The conductor 205 may function as a second gate (also referred to as a bottom gate) electrode. In this case, the potential applied to the conductor 205 may be changed independently of the potential applied to the conductor 260, thereby controlling the V th In particular, applying a negative potential to conductor 205 can control the V th It is possible to make the off-state current smaller by making the potential greater than 0 V. Therefore, applying a negative potential to the conductor 205 can make the drain current smaller when the potential applied to the conductor 260 is 0 V than when no potential is applied.

[0323] The conductor 205 is preferably provided to be larger than the channel formation region of the metal oxide 330. In particular, as shown in Fig. 22C, the conductor 205 preferably extends also in a region outside the end portion intersecting with the channel width direction of the metal oxide 330. In other words, the conductor 205 and the conductor 260 preferably overlap with each other with an insulator interposed therebetween on the outside of the side surface of the metal oxide 330 in the channel width direction.

[0324] With the above structure, the channel formation region of the metal oxide 330 can be electrically surrounded by the electric field of the conductor 260 that functions as a first gate electrode and the electric field of the conductor 205 that functions as a second gate electrode.

[0325] 22C, the conductor 205 is extended to function as wiring. However, the present invention is not limited to this, and a conductor that functions as wiring may be provided below the conductor 205.

[0326] The insulator 214 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the transistor 70A from the substrate side. Therefore, the insulator 214 is preferably made of an insulating material that has a function of preventing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), and copper atoms (i.e., the impurities are less likely to permeate through the material). Alternatively, the insulator 214 is preferably made of an insulating material that has a function of preventing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) (i.e., the oxygen is less likely to permeate through the material).

[0327] For example, it is preferable to use aluminum oxide, silicon nitride, or the like as the insulator 214. This can prevent impurities such as water or hydrogen from diffusing from the substrate side of the insulator 214 to the transistor 70A side. Alternatively, it can prevent oxygen contained in the insulator 224, etc. from diffusing from the insulator 214 to the substrate side.

[0328] The insulators 216, 280, and 281, which function as interlayer films, preferably have a lower dielectric constant than the insulator 214. Using a material with a low dielectric constant as the interlayer film can reduce parasitic capacitance between wirings. For example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine has been added, silicon oxide to which carbon has been added, silicon oxide to which carbon and nitrogen have been added, silicon oxide having vacancies, or the like can be used as appropriate for the insulators 216, 280, and 281.

[0329] The insulators 222 and 224 function as gate insulators.

[0330] Here, the insulator 224 in contact with the metal oxide 330 preferably releases oxygen upon heating. In this specification, oxygen released upon heating is sometimes referred to as excess oxygen. For example, the insulator 224 may be made of silicon oxide, silicon oxynitride, or the like as appropriate. By providing an insulator containing oxygen in contact with the metal oxide 330, oxygen vacancies in the metal oxide 330 can be reduced, and the reliability of the transistor 70A can be improved.

[0331] Specifically, it is preferable to use an oxide material from which a portion of oxygen is released by heating as the insulator 224. The oxide material from which oxygen is released by heating is an oxide material from which the amount of released oxygen converted into oxygen atoms is 1.0×10 in TDS (Thermal Desorption Spectroscopy) analysis. 18 atoms / cm 3 or more, preferably 1.0 × 10 19 atoms / cm 3 More preferably, 2.0 × 10 19 atoms / cm 3 or more, or 3.0 x 10 20 atoms / cm 3 The oxide film is one having the above properties. The surface temperature of the film during the TDS analysis is preferably in the range of 100°C or higher and 700°C or lower, or 100°C or higher and 400°C or lower.

[0332] 22C, the thickness of insulator 224 in a region that does not overlap with insulator 254 and metal oxide 330b may be thinner than the thickness of the other regions. It is preferable that the thickness of insulator 224 in a region that does not overlap with insulator 254 and metal oxide 330b is a thickness that allows sufficient diffusion of the oxygen.

[0333] Similar to the insulator 214, etc., the insulator 222 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the transistor 70A from the substrate side. For example, the insulator 222 preferably has lower hydrogen permeability than the insulator 224. By surrounding the insulator 224, the metal oxide 330, the insulator 250, etc. with the insulators 222, 254, and 274, it is possible to prevent impurities such as water or hydrogen from entering the transistor 70A from the outside.

[0334] Furthermore, the insulator 222 preferably has a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) (i.e., the oxygen is less likely to permeate). For example, the insulator 222 preferably has lower oxygen permeability than the insulator 224. The insulator 222 preferably has a function of suppressing the diffusion of oxygen or impurities, which can reduce the diffusion of oxygen contained in the metal oxide 330 toward the substrate side. Furthermore, the conductor 205 can be prevented from reacting with oxygen contained in the insulator 224 or oxygen contained in the metal oxide 330.

[0335] The insulator 222 may be an insulator containing an oxide of one or both of aluminum and hafnium, which are insulating materials. Aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used as the insulator containing an oxide of one or both of aluminum and hafnium. When the insulator 222 is formed using such a material, the insulator 222 functions as a layer that suppresses oxygen release from the metal oxide 330 and the intrusion of impurities such as hydrogen into the metal oxide 330 from the periphery of the transistor 70A.

[0336] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the above insulators.

[0337] The insulator 222 may be a single layer or a multilayer of an insulator containing a so-called high-k material, such as aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As transistors become smaller and more highly integrated, thinning of the gate insulator can cause problems such as leakage current. Using a high-k material for the insulator that functions as the gate insulator allows for a reduction in the gate potential during transistor operation while maintaining the physical film thickness.

[0338] The insulator 222 and the insulator 224 may have a stacked structure of two or more layers. In this case, the stacked structure is not limited to the stacked structure made of the same material, and may be a stacked structure made of different materials. For example, an insulator similar to the insulator 224 may be provided below the insulator 222.

[0339] The metal oxide 330 includes a metal oxide 330a, a metal oxide 330b on the metal oxide 330a, and a metal oxide 330c on the metal oxide 330b. By providing the metal oxide 330a below the metal oxide 330b, it is possible to suppress the diffusion of impurities from structures formed below the metal oxide 330a to the metal oxide 330b. Furthermore, by providing the metal oxide 330c on the metal oxide 330b, it is possible to suppress the diffusion of impurities from structures formed above the metal oxide 330c to the metal oxide 330b.

[0340] The metal oxide 330 preferably has a stacked structure of multiple oxide layers with different atomic ratios of each metal atom. For example, when the metal oxide 330 contains at least indium (In) and the element M, the ratio of the number of atoms of the element M contained in the metal oxide 330a to the number of atoms of all elements constituting the metal oxide 330a is preferably higher than the ratio of the number of atoms of the element M contained in the metal oxide 330b to the number of atoms of all elements constituting the metal oxide 330b. The atomic ratio of the element M contained in the metal oxide 330a to In is preferably higher than the atomic ratio of the element M contained in the metal oxide 330b to In. Here, the metal oxide 330c can be the same as the metal oxide 330a or the metal oxide 330b.

[0341] The energy of the conduction band minimum of the metal oxide 330a and the metal oxide 330c is preferably higher than the energy of the conduction band minimum of the metal oxide 330b. In other words, the electron affinity of the metal oxide 330a and the metal oxide 330c is preferably lower than the electron affinity of the metal oxide 330b. In this case, the metal oxide 330c is preferably a metal oxide that can be used for the metal oxide 330a. Specifically, the ratio of the number of atoms of the element M contained in the metal oxide 330c to the number of atoms of all elements constituting the metal oxide 330c is preferably higher than the ratio of the number of atoms of the element M contained in the metal oxide 330b to the number of atoms of all elements constituting the metal oxide 330b. Furthermore, the atomic ratio of the element M contained in the metal oxide 330c to In is preferably higher than the atomic ratio of the element M contained in the metal oxide 330b to In.

[0342] Here, the energy level of the conduction band minimum changes smoothly at the junction between the metal oxides 330a, 330b, and 330c. In other words, the energy level of the conduction band minimum at the junction between the metal oxides 330a, 330b, and 330c changes continuously or forms a continuous junction. To achieve this, it is advisable to reduce the defect level density of the mixed layers formed at the interfaces between the metal oxides 330a and 330b and between the metal oxides 330b and 330c.

[0343] Specifically, the metal oxides 330a and 330b, and the metal oxides 330b and 330c, may have a common element other than oxygen (as a main component), thereby forming a mixed layer with a low density of defect states. For example, when the metal oxide 330b is an In-Ga-Zn oxide, the metal oxides 330a and 330c may be made of In-Ga-Zn oxide, Ga-Zn oxide, gallium oxide, or the like. The metal oxide 330c may also have a stacked structure. For example, a stacked structure of In-Ga-Zn oxide and Ga-Zn oxide on the In-Ga-Zn oxide, or a stacked structure of In-Ga-Zn oxide and gallium oxide on the In-Ga-Zn oxide, may be used. In other words, the metal oxide 330c may have a stacked structure of In-Ga-Zn oxide and an oxide not containing In.

[0344] Specifically, the metal oxide 330a may have an atomic ratio of In:Ga:Zn=1:3:4 or 1:1:0.5. The metal oxide 330b may have an atomic ratio of In:Ga:Zn=4:2:3 or 3:1:2. The metal oxide 330c may have an atomic ratio of In:Ga:Zn=1:3:4, In:Ga:Zn=4:2:3, Ga:Zn=2:1, or Ga:Zn=2:5. Specific examples of the metal oxide 330c having a layered structure include a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and Ga:Zn=2:1 [atomic ratio], a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and Ga:Zn=2:5 [atomic ratio], and a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and gallium oxide.

[0345] In this case, the main carrier path is the metal oxide 330b. The above-described configuration of the metal oxide 330a and the metal oxide 330c can reduce the defect state density at the interface between the metal oxide 330a and the metal oxide 330b and at the interface between the metal oxide 330b and the metal oxide 330c. This reduces the effect of interface scattering on carrier conduction, allowing the transistor 70A to achieve a high on-state current and high frequency characteristics. Note that, when the metal oxide 330c has a stacked structure, in addition to the effect of reducing the defect state density at the interface between the metal oxide 330b and the metal oxide 330c, it is expected to suppress the diffusion of constituent elements of the metal oxide 330c toward the insulator 250. More specifically, the stacked structure of the metal oxide 330c, with an oxide not containing In positioned above the stacked structure, can suppress the diffusion of In toward the insulator 250. Because the insulator 250 functions as a gate insulator, the diffusion of In leads to poor transistor characteristics. Therefore, by forming the metal oxide 330c into a stacked structure, a highly reliable display device can be provided.

[0346] Conductors 242 (conductors 242a and 242b) functioning as a source electrode and a drain electrode are provided on the metal oxide 330b. Conductor 242 is preferably made of a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, or lanthanum, or an alloy containing any of the above metal elements, or an alloy combining any of the above metal elements. For example, tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel is preferably used. In addition, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred because they are conductive materials that are resistant to oxidation or materials that maintain conductivity even when they absorb oxygen.

[0347] By providing the conductor 242 so as to be in contact with the metal oxide 330, the oxygen concentration may decrease in the vicinity of the conductor 242 of the metal oxide 330. Furthermore, a metal compound layer containing the metal contained in the conductor 242 and components of the metal oxide 330 may be formed in the vicinity of the conductor 242 of the metal oxide 330. In such a case, the carrier density increases in the region of the metal oxide 330 in the vicinity of the conductor 242, and this region becomes a low-resistance region.

[0348] Here, the region between the conductor 242a and the conductor 242b is formed so as to overlap the opening of the insulator 280. This allows the conductor 260 to be disposed in a self-aligned manner between the conductor 242a and the conductor 242b.

[0349] The insulator 250 functions as a gate insulator. The insulator 250 is preferably disposed in contact with the upper surface of the metal oxide 330c. The insulator 250 can be made of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, or silicon oxide having vacancies. Silicon oxide and silicon oxynitride are particularly preferred because they are stable against heat.

[0350] The insulator 250 preferably has a reduced concentration of impurities such as water or hydrogen, similar to the insulator 224. The thickness of the insulator 250 is preferably 1 nm or more and 20 nm or less.

[0351] A metal oxide may be provided between the insulator 250 and the conductor 260. The metal oxide preferably suppresses oxygen diffusion from the insulator 250 to the conductor 260. This makes it possible to suppress oxidation of the conductor 260 due to oxygen in the insulator 250.

[0352] The metal oxide may function as part of the gate insulator. Therefore, when silicon oxide or silicon oxynitride is used for the insulator 250, it is preferable to use a metal oxide that is a high-k material with a high dielectric constant. By forming the gate insulator into a stacked structure of the insulator 250 and the metal oxide, it is possible to achieve a stacked structure that is thermally stable and has a high dielectric constant. Therefore, it is possible to reduce the gate potential applied during transistor operation while maintaining the physical thickness of the gate insulator. In addition, it is possible to reduce the equivalent oxide thickness (EOT) of the insulator that functions as the gate insulator.

[0353] Specifically, it is possible to use a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, etc. In particular, it is preferable to use an insulator containing an oxide of either or both of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate).

[0354] Although the conductor 260 is shown as having a two-layer structure in FIG. 22, it may have a single-layer structure or a laminated structure of three or more layers.

[0355] The conductor 260a is preferably made of a conductor having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), copper atoms, etc. Alternatively, it is preferable to use a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0356] The conductor 260a has a function of suppressing oxygen diffusion, which can suppress a decrease in conductivity due to oxidation of the conductor 260b caused by oxygen contained in the insulator 250. As a conductive material having a function of suppressing oxygen diffusion, it is preferable to use, for example, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like.

[0357] The conductor 260b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. Furthermore, since the conductor 260 also functions as wiring, it is preferable to use a conductor with high conductivity. For example, a conductive material containing tungsten, copper, or aluminum as a main component can be used. Furthermore, the conductor 260b may have a layered structure, such as a layered structure of titanium or titanium nitride and the above-mentioned conductive material.

[0358] 22A and 22C, in a region of the metal oxide 330b that does not overlap with the conductor 242, in other words, in the channel formation region of the metal oxide 330, the conductor 260 is arranged to cover the side surface of the metal oxide 330. This makes it easier for the electric field of the conductor 260, which functions as the first gate electrode, to act on the side surface of the metal oxide 330. This increases the on-current of the transistor 70A and improves the frequency characteristics.

[0359] Like the insulator 214, the insulator 254 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the transistor 70A from the insulator 280 side. For example, the insulator 254 preferably has lower hydrogen permeability than the insulator 224. Furthermore, as shown in FIGS. 22B and 22C , the insulator 254 preferably contacts the side surface of the metal oxide 330c, the top and side surfaces of the conductor 242a, the top and side surfaces of the conductor 242b, the side surfaces of the metal oxide 330a and the metal oxide 330b, and the top surface of the insulator 224. This configuration prevents hydrogen contained in the insulator 280 from entering the metal oxide 330 from the top or side surfaces of the conductor 242a, the conductor 242b, the metal oxide 330a, the metal oxide 330b, and the insulator 224.

[0360] Furthermore, it is preferable that the insulator 254 has a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (i.e., the oxygen is less likely to permeate). For example, it is preferable that the insulator 254 has lower oxygen permeability than the insulator 280 or the insulator 224.

[0361] The insulator 254 is preferably formed by sputtering. By forming the insulator 254 by sputtering in an oxygen-containing atmosphere, oxygen can be added to the insulator 224 near the region where the insulator 254 is in contact with the insulator 254. This allows oxygen to be supplied from this region to the metal oxide 330 through the insulator 224. The insulator 254 has a function of suppressing upward oxygen diffusion, thereby preventing oxygen from diffusing from the metal oxide 330 to the insulator 280. The insulator 222 has a function of suppressing downward oxygen diffusion, thereby preventing oxygen from diffusing from the metal oxide 330 toward the substrate. In this way, oxygen is supplied to the channel formation region of the metal oxide 330. This reduces oxygen vacancies in the metal oxide 330 and suppresses the transistor from becoming normally on.

[0362] For example, an insulator containing an oxide of one or both of aluminum and hafnium may be formed as the insulator 254. Note that as the insulator containing an oxide of one or both of aluminum and hafnium, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like.

[0363] The insulator 224, the insulator 250, and the metal oxide 330 are covered with the insulator 254, which has a barrier property against hydrogen, and thus the insulator 280 is separated from the insulator 224, the metal oxide 330, and the insulator 250 by the insulator 254. This makes it possible to prevent impurities such as hydrogen from penetrating from the outside of the transistor 70A, thereby providing the transistor 70A with good electrical characteristics and reliability.

[0364] The insulator 280 is provided over the insulator 224, the metal oxide 330, and the conductor 242 with the insulator 254 interposed therebetween. For example, the insulator 280 preferably includes silicon oxide, silicon oxynitride, silicon nitride oxide, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, silicon oxide having vacancies, or the like. Silicon oxide and silicon oxynitride are particularly preferred because they are thermally stable. Materials such as silicon oxide, silicon oxynitride, and silicon oxide having vacancies are particularly preferred because they can easily form a region containing oxygen that is released by heating.

[0365] It is preferable that the concentration of impurities such as water or hydrogen is reduced in the insulator 280. The top surface of the insulator 280 may be flattened.

[0366] Similar to the insulator 214, the insulator 274 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the insulator 280 from above. As the insulator 274, for example, an insulator that can be used for the insulator 214, the insulator 254, etc. may be used.

[0367] An insulator 281 functioning as an interlayer film is preferably provided over the insulator 274. Like the insulator 224 and the like, the insulator 281 preferably has a reduced concentration of impurities such as water or hydrogen.

[0368] The conductor 340a and the conductor 340b are arranged in openings formed in the insulator 281, the insulator 274, the insulator 280, and the insulator 254. The conductor 340a and the conductor 340b are arranged opposite each other with the conductor 260 interposed therebetween. The height of the upper surfaces of the conductor 340a and the conductor 340b may be flush with the upper surface of the insulator 281.

[0369] Note that insulator 241a is provided in contact with the inner walls of the openings of insulators 281, 274, 280, and 254, and a first conductor of conductor 340a is formed in contact with the side surface of insulator 241a. Conductor 242a is located on at least a portion of the bottom of the openings, and conductor 340a is in contact with conductor 242a. Similarly, insulator 241b is provided in contact with the inner walls of the openings of insulators 281, 274, 280, and 254, and a first conductor of conductor 340b is formed in contact with the side surface of insulator 241b. Conductor 242b is located on at least a portion of the bottom of the openings, and conductor 340b is in contact with conductor 242b.

[0370] The conductors 340a and 340b are preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductors 340a and 340b may have a layered structure.

[0371] When the conductor 340 has a layered structure, the conductors in contact with the metal oxide 330a, the metal oxide 330b, the conductor 242, the insulator 254, the insulator 280, the insulator 274, and the insulator 281 preferably have the aforementioned conductors capable of suppressing the diffusion of impurities such as water and hydrogen. For example, tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or ruthenium oxide is preferably used. Furthermore, the conductive material capable of suppressing the diffusion of impurities such as water and hydrogen may be used in a single layer or a layered structure. The use of such a conductive material can prevent oxygen added to the insulator 280 from being absorbed by the conductors 340a and 340b. Furthermore, it can prevent impurities such as water and hydrogen from entering the metal oxide 330 from layers above the insulator 281 through the conductors 340a and 340b.

[0372] The insulators 241a and 241b may be, for example, insulators that can be used for the insulator 254. The insulators 241a and 241b are provided in contact with the insulator 254, and therefore can prevent impurities such as water or hydrogen from the insulator 280 from entering the metal oxide 330 through the conductors 340a and 340b. Furthermore, oxygen contained in the insulator 280 can be prevented from being absorbed by the conductors 340a and 340b.

[0373] Although not shown, a conductor functioning as wiring may be disposed in contact with the upper surface of the conductor 340a and the upper surface of the conductor 340b. The conductor functioning as wiring is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor may also have a layered structure, for example, a layered structure of titanium or titanium nitride and the above-mentioned conductive material. The conductor may be formed so as to be embedded in an opening provided in an insulator.

[0374] <Transistor configuration example 2> As an example of a transistor structure, a transistor 70B will be described with reference to Figures 23A, 23B, and 23C. Figure 23A is a top view of transistor 70B. Figure 23B is a cross-sectional view of the portion indicated by the dashed dotted line X1-X2 in Figure 23A, and Figure 23C is a cross-sectional view of the portion indicated by the dashed dotted line Y1-Y2 in Figure 23A.

[0375] 23A, 23B, and 23C includes a conductive layer 521 over an insulating layer 524, an insulating layer 511 over the conductive layer 521 and the insulating layer 524, a semiconductor layer 531 over the insulating layer 511, an insulating layer 512 over the semiconductor layer 531, a conductive layer 523 over the insulating layer 512, and an insulating layer 515 over the insulating layer 511, the semiconductor layer 531, and the conductive layer 523. The semiconductor layer 531 includes a channel formation region 531i overlapping with the conductive layer 523, a source region 531s in contact with the insulating layer 515, and a drain region 531d in contact with the insulating layer 515. The semiconductor layer 531 can be, for example, an oxide semiconductor, which is a type of metal oxide. The semiconductor layer 531 may have a stacked structure of two or more layers.

[0376] The insulating layer 515 contains nitrogen or hydrogen. When the insulating layer 515 is in contact with the source region 531s and the drain region 531d, the nitrogen or hydrogen in the insulating layer 515 is added to the source region 531s and the drain region 531d. The addition of nitrogen or hydrogen increases the carrier density of the source region 531s and the drain region 531d.

[0377] The transistor 70B may also include a conductive layer 522a electrically connected to the source region 531s through an opening 536a provided in the insulating layer 515. The transistor 70B may also include a conductive layer 522b electrically connected to the drain region 531d through an opening 536b provided in the insulating layer 515.

[0378] The insulating layer 511 functions as a first gate insulating layer, the insulating layer 512 functions as a second gate insulating layer, and the insulating layer 515 functions as a protective insulating layer.

[0379] The insulating layer 512 has an excess oxygen region. The insulating layer 512 has an excess oxygen region, which allows excess oxygen to be supplied to the channel formation region 531i of the semiconductor layer 531. Therefore, oxygen vacancies that may be formed in the channel formation region 531i can be compensated for by the excess oxygen, and a highly reliable display device can be provided.

[0380] In order to supply excess oxygen into the semiconductor layer 531, excess oxygen may be supplied to the insulating layer 511 formed below the semiconductor layer 531. In this case, the excess oxygen contained in the insulating layer 511 can also be supplied to the source region 531s and the drain region 531d of the semiconductor layer 531. When excess oxygen is supplied into the source region 531s and the drain region 531d, the resistance of the source region 531s and the drain region 531d may increase.

[0381] On the other hand, by configuring the insulating layer 512 formed above the semiconductor layer 531 to contain excess oxygen, it is possible to selectively supply excess oxygen only to the channel formation region 531i. Alternatively, by supplying excess oxygen to the channel formation region 531i, the source region 531s, and the drain region 531d, and then selectively increasing the carrier density in the source region 531s and the drain region 531d, it is possible to prevent the resistance of the source region 531s and the drain region 531d from increasing.

[0382] The source region 531s and the drain region 531d of the semiconductor layer 531 preferably contain an element that forms an oxygen vacancy or an element that bonds with the oxygen vacancy. Typical examples of the element that forms the oxygen vacancy or the element that bonds with the oxygen vacancy include hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, chlorine, titanium, and Group 18 elements. Typical examples of Group 18 elements include helium, neon, argon, krypton, and xenon. When the insulating layer 515 contains one or more of the above-mentioned oxygen vacancy-forming elements, the elements diffuse from the insulating layer 515 to the source region 531s and the drain region 531d, or are added to the source region 531s and the drain region 531d by impurity addition processing.

[0383] When an impurity element is added to a metal oxide, the bond between the metal element and oxygen in the metal oxide is broken, forming an oxygen vacancy. Alternatively, when an impurity element is added to a metal oxide, oxygen that was bonded to the metal element in the metal oxide bonds with the impurity element, and oxygen is released from the metal element, forming an oxygen vacancy. As a result, the carrier density in the metal oxide increases, and the conductivity becomes higher.

[0384] The conductive layer 521 functions as a first gate, the conductive layer 523 functions as a second gate, the conductive layer 522a functions as a source, and the conductive layer 522b functions as a drain.

[0385] 23C, an opening 537 is provided in the insulating layer 511 and the insulating layer 512. The conductive layer 521 is electrically connected to the conductive layer 523 through the opening 537. Therefore, the same potential is applied to the conductive layer 521 and the conductive layer 523. Note that different potentials may be applied to the conductive layer 521 and the conductive layer 523 without providing the opening 537. Alternatively, the conductive layer 521 may be used as a light-shielding film without providing the opening 537. For example, by forming the conductive layer 521 using a light-shielding material, it is possible to suppress light from below irradiating the channel formation region 531i.

[0386] Also, as shown in Figures 23B and 23C, semiconductor layer 531 is positioned opposite conductive layer 521 having a function as a first gate and conductive layer 523 having a function as a second gate, and is sandwiched between the two conductive layers having a function as gates.

[0387] The transistor 70B also has an S-channel structure like the transistor 70A. With such a structure, the semiconductor layer 531 included in the transistor 70B can be electrically surrounded by the electric fields of the conductive layer 521 functioning as a first gate and the conductive layer 523 functioning as a second gate.

[0388] Because the transistor 70B has an S-channel structure, an electric field for inducing a channel by the conductive layer 521 or the conductive layer 523 can be effectively applied to the semiconductor layer 531. This improves the current driving capability of the transistor 70B, enabling high on-state current characteristics to be obtained. Furthermore, since the on-state current can be increased, the transistor 70B can be miniaturized. Furthermore, because the transistor 70B has a structure in which the semiconductor layer 531 is surrounded by the conductive layers 521 and 523, the mechanical strength of the transistor 70B can be increased.

[0389] The transistor 70B may be called a TGSA (Top Gate Self Align) type FET, based on the position of the conductive layer 523 relative to the semiconductor layer 531 or the method of forming the conductive layer 523.

[0390] Although the insulating layer 512 is provided only in the portion overlapping with the conductive layer 523 in the transistor 70B, the present invention is not limited thereto, and the insulating layer 512 may cover the semiconductor layer 531. Alternatively, the conductive layer 521 may not be provided.

[0391] Alternatively, an aluminum oxide layer may be provided between the insulating layer 512 and the conductive layer 523. By providing the aluminum oxide layer, excess oxygen contained in the insulating layer 512 can be prevented from diffusing toward the conductive layer 523.

[0392] At least a region of the conductive layer 523 in contact with the insulating layer 512 is preferably made of a material through which oxygen does not easily diffuse. Examples of such a material include aluminum and molybdenum. For example, the conductive layer 523 may have a two-layer structure in which aluminum is provided on the insulating layer 512 side and titanium is provided thereon. Alternatively, the conductive layer 523 may have a three-layer structure in which molybdenum is provided on the insulating layer 512 side and aluminum and titanium are provided thereon.

[0393] <Transistor configuration example 3> As an example of a transistor structure, a transistor 70C will be described with reference to FIGS. 24A, 24B, and 24C. FIG. 24A is a top view of the transistor 70C. FIG. 24B is a cross-sectional view of the portion indicated by the dashed-dotted line X1-X2 in FIG. 24A, and FIG. 24C is a cross-sectional view of the portion indicated by the dashed-dotted line Y1-Y2 in FIG. 24A. Note that for ease of understanding, some of the components of the transistor 70C (such as an insulating layer that functions as a gate insulating layer) are omitted in FIG. 24A. Note that the extension direction of the dashed-dotted line X1-X2 may be referred to as the channel length direction, and the extension direction of the dashed-dotted line Y1-Y2 may be referred to as the channel width direction.

[0394] Transistor 70C has a conductive layer 521 on an insulating layer 524, an insulating layer 511 on the insulating layer 524 and on the conductive layer 521, a semiconductor layer 531 on the insulating layer 511, a conductive layer 522a on the semiconductor layer 531 and on the insulating layer 511, a conductive layer 522b on the semiconductor layer 531 and on the insulating layer 511, an insulating layer 512 on the semiconductor layer 531, on the conductive layer 522a, and on the conductive layer 522b, and a conductive layer 523 on the insulating layer 512. Note that the insulating layer 524 may be a substrate.

[0395] Further, for example, any of the semiconductor materials described in the above embodiments can be used for the semiconductor layer 531. For example, the semiconductor layer 531 may be an oxide semiconductor, which is a type of metal oxide.

[0396] The insulating layer 511 and the insulating layer 512 have an opening 535. The conductive layer 523 is electrically connected to the conductive layer 521 through the opening 535.

[0397] Here, the insulating layer 511 functions as a first gate insulating layer of the transistor 70C, and the insulating layer 512 functions as a second gate insulating layer of the transistor 70C. In the transistor 70C, the conductive layer 521 functions as a first gate, the conductive layer 522a functions as one of the source and the drain, and the conductive layer 522b functions as the other of the source and the drain. In the transistor 70C, the conductive layer 523 functions as a second gate.

[0398] The transistor 70C is a so-called channel-etch type transistor and has a dual-gate structure.

[0399] The transistor 70C may also be configured without the conductive layer 523. In this case, the transistor 70C is a so-called channel-etch transistor and has a bottom-gate structure.

[0400] 24B and 24C , semiconductor layer 531 is positioned opposite conductive layer 521 and conductive layer 523, and is sandwiched between the two conductive layers having gate functions. The length of conductive layer 523 in the channel length direction and the length of conductive layer 523 in the channel width direction are longer than the length of semiconductor layer 531 in the channel length direction and the length of semiconductor layer 531 in the channel width direction, respectively, and semiconductor layer 531 is entirely covered with conductive layer 523 with insulating layer 512 interposed therebetween.

[0401] In other words, the conductive layer 521 and the conductive layer 523 are connected to each other through an opening 535 provided in the insulating layer 511 and the insulating layer 512 , and have a region located outside the side edge of the semiconductor layer 531 .

[0402] With this configuration, the semiconductor layer 531 included in the transistor 70C can be formed into an S-channel structure in which the semiconductor layer 531 is electrically surrounded by the electric fields of the conductive layers 521 and 523.

[0403] Since the transistor 70C has an s-channel structure, an electric field for inducing a channel can be effectively applied to the semiconductor layer 531 by the conductive layer 521 functioning as the first gate, thereby improving the current driving capability of the transistor 70C and enabling high on-current characteristics to be obtained. Furthermore, since the on-current can be increased, the transistor 70C can be miniaturized.

[0404] Furthermore, since the transistor 70C has a structure in which the semiconductor layer 531 is surrounded by the conductive layer 521 having a function of the first gate and the conductive layer 523 having a function of the second gate, the mechanical strength of the transistor 70C can be increased.

[0405] The transistor 70A can be used, for example, as the transistor 251. FIG. 25A shows a cross-sectional example of the display device 100 in which the transistor 70A is used as the transistor 251. A single crystal silicon transistor may be used as the transistor 251. FIG. 25B shows a cross-sectional example of the display device 100 in which a single crystal silicon transistor is used as the transistor 251.

[0406] When a single crystal silicon transistor is used as the transistor 251, single crystal silicon is used as the substrate 111. In the single crystal silicon transistor, part of the substrate 111 is used as a channel formation region. When a single crystal silicon transistor is used as the transistor 251, an SOI substrate may be used as the substrate 111.

[0407] 26 , the transistor 252 included in the peripheral circuit region 232 and / or the peripheral circuit region 233 may be formed of a single crystal silicon transistor, and the transistor 251 and the light-emitting element 170 included in the display region 235 may be provided on the single crystal silicon transistor.

[0408] By overlapping the peripheral circuit region and the display region, the display device 100 can be made smaller. Furthermore, if the external dimensions of the display device 100 are constant, the area of ​​the display region can be expanded. This allows for an increase in the resolution of the display device 100. Furthermore, if the pixel resolution is constant, the area occupied by each pixel can be increased. This allows for an increase in the luminance of the display device. Furthermore, the aperture ratio of the pixel can be increased. For example, the aperture ratio of the pixel can be set to 40% or more and less than 100%, preferably 50% or more and 95% or less, and more preferably 60% or more and 95% or less. Furthermore, by increasing the aperture ratio per pixel, the current density supplied to the light-emitting element of the pixel can be reduced. This reduces the load on the light-emitting element, improving the reliability of the display device 100.

[0409] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes.

[0410] (Embodiment 5) In this embodiment, electronic devices to which a display device according to one embodiment of the present invention can be applied will be described.

[0411] The display device of one embodiment of the present invention can be applied to a display portion of an electronic device. Therefore, an electronic device with high display quality, extremely high resolution, or high reliability can be realized.

[0412] Examples of electronic devices using a display device according to one embodiment of the present invention include display devices such as televisions and monitors, lighting devices, desktop or notebook personal computers, word processors, and DVD (Digital Versatile Disc) players. Examples of such equipment include image playback devices that play back still images or videos stored on recording media such as CDs, portable CD players, radios, tape recorders, headphone stereos, stereos, table clocks, wall clocks, cordless telephone handsets, transceivers, car phones, mobile phones, personal digital assistants, tablet terminals, portable game consoles, fixed game consoles such as pachinko machines, calculators, electronic organizers, e-book terminals, electronic translators, voice input devices, video cameras, digital still cameras, electric shavers, high-frequency heating devices such as microwave ovens, air conditioning equipment such as electric rice cookers, electric washing machines, electric vacuum cleaners, water heaters, electric fans, hair dryers, air conditioners, humidifiers, and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, electric freezers, electric refrigerator-freezers, DNA storage freezers, flashlights, tools such as chainsaws, smoke detectors, and medical equipment such as dialysis machines. Other examples include industrial equipment such as emergency lights, traffic lights, conveyor belts, elevators, escalators, industrial robots, power storage systems, and power storage devices for power leveling and smart grids. Mobile vehicles propelled by fuel-powered engines or electric motors powered by power from power storage devices may also be included in the category of electronic devices. Examples of such mobile vehicles include electric vehicles (EVs), hybrid electric vehicles (HEVs) that combine internal combustion engines and electric motors, plug-in hybrid electric vehicles (PHEVs), tracked vehicles in which the tires and wheels of these vehicles have been replaced with tracks, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft, rockets, artificial satellites, space probes, planetary probes, and spaceships.

[0413] An electronic device according to one aspect of the present invention can be incorporated along the curved surface of an inner or outer wall of a house or building, or the interior or exterior of an automobile.

[0414] An electronic device according to one embodiment of the present invention may include a secondary battery (battery), and it is preferable that the secondary battery can be charged using contactless power transmission.

[0415] Examples of secondary batteries include lithium ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries, organic radical batteries, lead-acid batteries, air secondary batteries, nickel-zinc batteries, and silver-zinc batteries.

[0416] An electronic device according to one embodiment of the present invention may include an antenna. By receiving a signal through the antenna, images, information, and the like can be displayed on a display portion. When the electronic device includes an antenna and a secondary battery, the antenna may be used for contactless power transmission.

[0417] An electronic device according to one embodiment of the present invention may have a sensor (including a function to measure force, displacement, position, velocity, 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).

[0418] An electronic device according to one embodiment of the present invention can have various functions, such as a function to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date, or time, a function to execute various software (programs), a wireless communication function, a function to read programs or data recorded on a recording medium, etc.

[0419] Furthermore, electronic devices having multiple display units can have a function of mainly displaying image information on one display unit and mainly displaying text information on another display unit, or a function of displaying a stereoscopic image by displaying an image taking into account parallax on the multiple display units. Furthermore, electronic devices having an image receiving unit can have a function of capturing still images or moving images, a function of automatically or manually correcting the captured images, a function of storing the captured images in a recording medium (external or built in the electronic device), a function of displaying the captured images on the display units, etc. Note that the functions of the electronic devices of one embodiment of the present invention are not limited to these and can have various functions.

[0420] A display device according to one embodiment of the present invention can display high-resolution images. Therefore, the display device can be suitably used in portable electronic devices, wearable electronic devices, e-book readers, etc. The display device can also be suitably used in virtual reality (VR) devices, augmented reality (AR) devices, etc.

[0421] 27A shows the appearance of a head-mounted display 810. The head-mounted display 810 includes a mounting portion 811, a lens 812, a main body 813, a display portion 814, and a cable 815. The mounting portion 811 includes a built-in battery 816. A display device according to one embodiment of the present invention can be used as the display portion 814.

[0422] A cable 815 supplies power from a battery 816 to the main body 813. The main body 813 is equipped with a wireless receiver and the like, and can display received video information such as image data on a display unit 814. Furthermore, a camera provided in the main body 813 captures the movement of the user's eyeball and / or eyelid, and calculates the user's line of sight based on this information, thereby enabling the user's line of sight to be used as an input means.

[0423] Furthermore, the wearing unit 811 may be provided with a plurality of electrodes at positions that come into contact with the user. The main body 813 may have a function of recognizing the user's line of sight by detecting a current flowing through the electrodes in accordance with the movement of the user's eyeballs. Furthermore, the main body 813 may have a function of monitoring the user's pulse by detecting a current flowing through the electrodes. Furthermore, the wearing unit 811 may have various sensors such as a temperature sensor, a pressure sensor, an acceleration sensor, etc., and may have a function of displaying the user's biological information on the display unit 814. Furthermore, the wearing unit 811 may detect the movement of the user's head, etc., and change the image displayed on the display unit 814 in accordance with the movement.

[0424] 27B shows the appearance of head mounted display 820. Head mounted display 820 is a goggle-type information processing device.

[0425] The head-mounted display 820 includes a housing 821, operation buttons 823, a band-shaped fixture 824, and two display units 822. The two display units 822 allow the user to view one display unit per eye. This allows high-resolution images to be displayed even when performing 3D display using parallax. Furthermore, the display unit 822 is curved in an arc shape roughly centered on the user's eye. This allows the distance from the user's eye to the display surface of the display unit to be constant, allowing the user to view more natural images. Even if the brightness and chromaticity of light from the display unit change depending on the viewing angle, this effect can be virtually ignored because the user's eyes are positioned normal to the display surface of the display unit, allowing for the display of more realistic images.

[0426] The operation button 823 has functions such as a power button, etc. In addition to the operation button 823, other buttons may be provided.

[0427] A display device according to one embodiment of the present invention can be applied to the display portion 822. The display device according to one embodiment of the present invention has extremely high definition, making it difficult for a user to see pixels, and can display more realistic images.

[0428] FIG. 27C shows the appearance of camera 830 with viewfinder 840 attached.

[0429] The camera 830 includes a housing 831, a display unit 832, operation buttons 833, a shutter button 834, etc. The camera 830 is also provided with a detachable lens 836 attached thereto.

[0430] Here, camera 830 is configured such that lens 836 can be removed from housing 831 and replaced, but lens 836 and the housing may be integrated.

[0431] The camera 830 can capture an image by pressing a shutter button 834. The display unit 832 also functions as a touch panel, and an image can be captured by touching the display unit 832.

[0432] The housing 831 of the camera 830 has a mount with electrodes, and can be connected to a finder 840 as well as a strobe device and the like.

[0433] The finder 840 includes a housing 841, a display unit 842, a button 843, and the like.

[0434] The housing 841 has a mount that engages with the mount of the camera 830, and the viewfinder 840 can be attached to the camera 830. The mount also has electrodes, and images received from the camera 830 can be displayed on the display unit 842 via the electrodes.

[0435] The button 843 functions as a power button, and the display of the display unit 842 can be switched on and off by the button 843.

[0436] The display device according to one embodiment of the present invention can be applied to the display portion 832 of the camera 830 and the display portion 842 of the finder 840.

[0437] Note that in FIG. 27C, the camera 830 and the finder 840 are separate electronic devices that are detachable; however, a finder including a display device according to one embodiment of the present invention may be built into the housing 831 of the camera 830.

[0438] 27D includes a housing 851, a display portion 852, a microphone 857, a speaker portion 854, a camera 853, and an operation switch 855. A display device according to one embodiment of the present invention can be used for the display portion 852. The display portion 852 has a touch panel function. The information terminal 850 includes an antenna, a battery, and the like inside the housing 851. The information terminal 850 can be used as, for example, a smartphone, a mobile phone, a tablet information terminal, a tablet personal computer, an e-book reader, or the like.

[0439] 27E shows an example of a wristwatch-type information terminal. Information terminal 860 includes a housing 861, a display unit 862, a band 863, a buckle 864, operation switches 865, and an input / output terminal 866. Information terminal 860 also includes an antenna and a battery inside housing 861. Information terminal 860 can execute various applications such as mobile phone calls, e-mail, text browsing and creation, music playback, internet communication, and computer games.

[0440] The display unit 862 also has a touch sensor, and can be operated by touching the screen with a finger or a stylus. For example, an application can be started by touching an icon 867 displayed on the display unit 862. The operation switch 865 can have various functions, such as time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, and power saving mode activation / deactivation. For example, the functions of the operation switch 865 can be set by an operating system built into the information terminal 860.

[0441] The information terminal 860 is also capable of performing short-range wireless communication according to a communication standard. For example, hands-free conversation is also possible by mutual communication with a wirelessly capable headset. The information terminal 860 is also provided with an input / output terminal 866, and can transmit and receive data to and from other information terminals via the input / output terminal 866. Charging can also be performed via the input / output terminal 866. Note that charging may be performed by wireless power supply without using the input / output terminal 866.

[0442] 27F is a perspective view of a television set 870. The television set 870 includes a housing 871, a display unit 872, a speaker 873, operation keys 874 (including a power switch or an operation switch), a connection terminal 875, a sensor 876 (including a function of measuring distance, light, temperature, and the like), and the like. A display device according to one embodiment of the present invention can be applied to the display unit 872. The television set 870 can incorporate a display device having a screen size of, for example, 50 inches or more or 100 inches or more in the display unit 872.

[0443] This embodiment mode can be implemented in appropriate combination with structures described in other embodiment modes. [Explanation of symbols]

[0444] 100: display device, 111: substrate, 112: insulating layer, 113: insulating layer, 114: insulating layer, 115: insulating layer, 116: insulating layer, 117: electrode, 118: conductive layer, 119: wiring, 121: substrate, 122: insulating layer, 124: FPC, 126: protective layer, 131: colored layer, 132: light-shielding layer, 133: insulating layer, 138: connection layer, 139: insulating layer, 142: adhesive layer, 151: element substrate, 161: opening, 170: light-emitting element

Claims

1. an anode, an EL layer on the anode, a cathode on the EL layer, and an insulating layer on the cathode; a first layer adjacent to a side surface of the EL layer and an upper surface of the insulating layer; a first portion adjacent to the side surface via the first layer; the first layer has a region in contact with a top surface of the anode and a region in contact with a side surface of the anode, the angle θ between the bottom surface and the side surface of the EL layer is greater than 90 degrees; the refractive index of the first portion is smaller than the refractive index of the first layer; The insulating layer comprises at least one of silicon oxide, silicon oxynitride, and aluminum oxide.

2. In claim 1, The light-emitting element is such that the angle θ is greater than 90 degrees and is equal to or smaller than 135 degrees.

3. In claim 1 or claim 2, The first portion includes a Group 18 element, nitrogen, oxygen, or fluorine.

4. The light-emitting element according to any one of claims 1 to 3, A light-emitting element that emits light from the cathode side.

5. A light-emitting element according to any one of claims 1 to 4, The display device also includes a plurality of transistors.

6. The display device according to claim 5 ; at least one of an antenna, a battery, or a sensor; An electronic device having:

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