Method for manufacturing a display device

Abstract

Provided is a novel method for producing a display device. A positive electrode is formed on an insulation layer, an EL layer is formed on the positive electrode, and a negative electrode is formed on the EL layer. Without providing a partition wall, a plurality of light-emitting elements are formed by selectively removing part of each of the positive electrode, the EL layer, and the negative electrode. A translucent electrically conductive layer is formed so as to cover the plurality of light-emitting elements. The negative electrode of each of the plurality of light-emitting elements is electrically connected to the electrically conductive layer.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a method for manufacturing a display 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 pixel aperture ratios and achieve high definition when forming light-emitting layers using metal masks. 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] (1) One embodiment of the present invention is a method for manufacturing a display device, the method including the steps of forming an anode over an insulating layer, forming an EL layer over the anode, forming a cathode over the EL layer, selectively removing parts of the anode, the EL layer, and the cathode to form a plurality of light-emitting elements, and forming a conductive layer to cover the plurality of light-emitting elements, wherein the cathode of each of the plurality of light-emitting elements is electrically connected to the conductive layer and the conductive layer has light-transmitting properties.

[0012] (2) Another embodiment of the present invention is a method for manufacturing a display device, the method including the steps of forming an anode on an insulating layer, forming an EL layer on the anode, forming a cathode on the EL layer, selectively removing portions of the anode, the EL layer, and the cathode to form a plurality of light-emitting elements, and forming a conductive layer on the plurality of light-emitting elements, wherein, in at least some of the plurality of light-emitting elements, the cathode of each adjacent light-emitting element is electrically connected to the conductive layer.

[0013] Another embodiment of the present invention is a method for manufacturing a display device, in (1) or (2), including a step of forming a plurality of transistors over a substrate and a step of forming an insulating layer over the plurality of transistors, wherein the insulating layer has a surface on which the insulating layer is formed with reduced unevenness.

[0014] The transistor preferably includes an oxide semiconductor in a semiconductor layer in which a channel is formed, and the oxide semiconductor preferably includes at least one of indium and zinc. [Effects of the Invention]

[0015] 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 highly productive display device, a semiconductor device, or the like can be provided. Alternatively, a novel display device, a semiconductor device, or the like can be provided.

[0016] 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]

[0017] 1A to 1C are diagrams illustrating an example of the configuration of a display device. 2A to 2C are diagrams illustrating an example of a method for manufacturing a first element substrate. 3A and 3B are diagrams illustrating an example of a method for manufacturing the first element substrate. 4A and 4B are diagrams illustrating an example of a method for manufacturing the first element substrate. 5A and 5B are diagrams illustrating an example of a method for manufacturing the first element substrate. 6A and 6B are diagrams illustrating an example of a method for manufacturing the first element substrate. 7A1, 7A2, and 7B are diagrams illustrating an example of a method for manufacturing a first element substrate. 8A and 8B are diagrams illustrating an example of a method for manufacturing the first element substrate. 9A and 9B are diagrams illustrating modified examples of the first element substrate. FIG. 10 is a diagram illustrating a modified example of the first element substrate. 11A to 11C are diagrams illustrating an example of a method for manufacturing a second element substrate. 12A to 12C are diagrams illustrating an example of a method for manufacturing a display device. FIG. 13 is a diagram illustrating a modified example of the display device. Figure 14A is a diagram explaining the classification of crystal structures, Figure 14B is a diagram explaining the XRD spectrum of a CAAC-IGZO film, and Figure 14C is a diagram explaining the electron microbeam diffraction pattern of a CAAC-IGZO film. FIG. 15A and FIGS. 15B1 to 15B5 are diagrams illustrating an example of the configuration of a display device. FIG. 16 is a diagram illustrating an example of the configuration of a pixel circuit. 17A to 17C are diagrams illustrating configuration examples of light-emitting elements. 18A to 18F are diagrams showing an example of an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] 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.).

[0020] 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.

[0021] 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.

[0022] 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).

[0023] 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.).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Furthermore, in this specification, the term "capacitive element" refers 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" refers not only to a circuit element including a pair of electrodes and a dielectric between the electrodes, but also to 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] "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) accompanying 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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" can be interchanged with the term "conductive film." Or, for example, the term "insulating film" can be interchanged with the term "insulating layer." Or, in some cases or depending on the situation, terms such as "film" and "layer" can be omitted and replaced with other terms. For example, the terms "conductive layer" or "conductive film" can be interchanged with the term "conductor." Or, for example, the terms "insulating layer" and "insulating film" can be interchanged with the term "insulator."

[0037] 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.

[0038] Furthermore, in this specification and the like, terms such as "wiring," "signal line," and "power line" can be interchanged depending on the situation or circumstances. For example, the term "wiring" can be changed to the term "signal line." For example, the term "wiring" can be changed to the term "power line." Vice versa, terms such as "signal line" and "power line" can be changed to the term "wiring." A term such as "power line" can be changed to the term "signal line." Vice versa, terms such as "signal line" can be changed to the term "power line." Furthermore, the term "potential" applied to a wiring can be changed to the term "signal" depending on the situation or circumstances. Vice versa, terms such as "signal" can be changed to the term "potential."

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 in which a channel of a transistor is formed, the metal oxide may be referred to as an oxide semiconductor. In other words, when a metal oxide is used in a semiconductor layer in which a channel of a transistor having at least one of an amplifying function, a rectifying function, and a switching function is formed, the metal oxide can be referred to as a metal oxide semiconductor. Furthermore, in this specification and the like, a transistor in which a semiconductor layer in which a channel is formed includes a metal oxide or an oxide semiconductor can be referred to as an "OS transistor."

[0045] 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.

[0046] The embodiments described in this specification will be described with reference to the drawings. However, those skilled in the art will readily understand 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. Furthermore, to make the drawings easier to understand, the illustration of some components may be omitted in perspective views, top views, etc.

[0047] 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.

[0048] 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]," "[m,n]," etc. For example, one of multiple colored layers 131 may be referred to as colored layer 131R, and another may be referred to as colored layer 131G.

[0049] In this specification, etc., a device fabricated using a metal mask or FMM (fine metal mask, high-resolution metal mask) may be referred to as a device with an MM (metal mask) structure. Also, in this specification, etc., a device fabricated without using a metal mask or FMM may be referred to as a device with an MML (metal maskless) structure.

[0050] (Embodiment 1) A display device 100 according to one embodiment of the present invention will be described with reference to the drawings.

[0051] <<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.

[0052] 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.

[0053] 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.

[0054] 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 .

[0055] 1A also includes an enlarged view of a portion of display region 235. In display region 235, a plurality of pixels 240 are arranged in a matrix. Pixels 240 include pixel 230R, pixel 230G, and pixel 230B. 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."

[0056] [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.

[0057] 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.

[0058] Each of the pixels 230R, 230G, and 230B includes a transistor 251 for driving a display element. The peripheral circuit region 232 and the peripheral circuit region 233 each include a plurality of transistors. In FIG. 1B, the transistor 252 is shown as an example of a transistor included in the peripheral circuit region 233.

[0059] The display device 100 has a transistor 251, a transistor 252, a light-emitting element 170, a colored layer 131 (a colored layer 131R, a colored layer 131G, and a colored layer 131B), a light-shielding layer 132, etc. between a substrate 111 and a substrate 121. The substrate 111 and the substrate 121 are bonded together via an adhesive layer 142.

[0060] 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.

[0061] The substrate 121 is provided with an insulating layer 122, a colored layer 131, a light-shielding layer 132, an insulating layer 133, and the like. The insulating layer 133 may also function as a planarizing layer. The term "planarizing layer" refers to a layer having a surface that reduces the irregularities of the surface on which it is formed.

[0062] 1C is an enlarged view of the transistor 252. Note that the transistor 251 can have a structure similar to that of the transistor 252.

[0063] The transistor 252 has an electrode 221, a semiconductor layer 231, an electrode 224a, an electrode 224b, and an electrode 226. The electrode 221 is provided over the insulating layer 113, and an insulating layer 211 is provided to cover the electrode 221. The semiconductor layer 231 is provided over the insulating layer 211. The electrode 224a and the electrode 224b are provided over the insulating layer 211, and the electrode 224a has a region in contact with part of the semiconductor layer 231, and the electrode 224b has a region in contact with another part of the semiconductor layer 231. One of the electrode 224a and the electrode 224b can function as a source electrode. The other of the electrode 224a and the electrode 224b can function as a drain electrode.

[0064] Furthermore, an insulating layer 210 is provided to cover the electrode 224a, the electrode 224b, and the semiconductor layer 231. An electrode 226 is provided over the insulating layer 210. The electrode 226 has a region overlapping with the semiconductor layer 231. An insulating layer 213 is provided to cover the electrode 226.

[0065] 1B illustrates bottom-gate transistors as the transistor 251 and the transistor 252. The transistor 251 is a transistor that controls current flowing through the light-emitting element 170 (also referred to as a driving transistor).

[0066] An insulating layer 114 is provided over the insulating layer 213. The insulating layer 114 functions as a planarization layer. The transistors 251 and 252 are covered with the insulating layer 213 and the insulating layer 114. The number of insulating layers covering the transistors is not limited, and may be a single layer or two or more layers.

[0067] It is preferable that at least one insulating layer covering each transistor is made of a material that is resistant to the diffusion of impurities such as water and hydrogen. This allows the insulating layer to function as a barrier film. With this configuration, it is possible to effectively prevent impurities from diffusing into the transistors from the outside, thereby realizing a highly reliable display device.

[0068] In the pixel 230, the 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.

[0069] In addition, 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 overlapping with the electrode 171 with the EL layer 172 interposed therebetween.

[0070] The light emitting element 170 is covered with an insulating layer 115 and an insulating layer 116. The insulating layer 116 functions as a planarizing layer.

[0071] A conductive layer 118 is provided on the insulating layer 116. The conductive layer 118 is electrically connected to an electrode 173 via an electrode 117 provided so as to be embedded in the insulating layer 115 and the insulating layer 116. The conductive layer 118 is electrically connected to the multiple electrodes 173 and functions as a common electrode.

[0072] 1B also includes a wiring 125, an electrode 228, and an electrode 229. The wiring 125 and the electrode 228 are provided on an insulating layer 211. The electrode 229 is electrically connected to the electrode 228 through an opening provided in the insulating layer 210 that overlaps with the electrode 228. The wiring 125 and the electrode 228 can be formed simultaneously in the same process as the electrodes 224a and 224b. The electrode 229 can be formed simultaneously in the same process as the electrode 226.

[0073] 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.

[0074] The connection layer 138 may be made of an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like.

[0075] The light-emitting element 170 is, for example, a top-emission light-emitting element and has a layered structure in which an electrode 171 functioning as an anode, an EL layer 172, and an electrode 173 functioning as a cathode are layered in this order from the insulating layer 114 side.

[0076] 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. In addition, the conductive layer 118 also has a function of transmitting visible light.

[0077] 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, a substance with a high electron-injecting property, a substance with a high electron-transporting property, an electron-blocking material, or a bipolar substance (a substance with high electron-transporting property and high hole-transporting property).

[0078] 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 .

[0079] There are two methods for achieving color display: combining a white-emitting light-emitting element 170 with a colored layer, and providing light-emitting elements 170 with different emitting 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 luminescent colors with higher color purity than the former method. In addition to the latter method, the color purity can be further improved by providing a microcavity structure to the light-emitting element 170.

[0080] 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 a deposition method (including vacuum deposition), a transfer method, a printing method, an inkjet method, a coating method, or the like.

[0081] 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.

[0082] In this embodiment, a light emitting element 170 that emits white light is used. Light 175 emitted by the light emitting element 170 is emitted toward the substrate 121 side through the colored layer 131. The wavelength range of the light 175 that has passed through the colored layer 131 changes depending on the material that makes up the colored layer 131. In other words, by passing the light 175 through the colored layer 131, it is possible to change the hue of the light 175 to red, green, blue, cyan, magenta, yellow, or the like.

[0083] In this embodiment, light 175R having a changed hue after passing through the colored layer 131R is emitted from the pixel 230R. Light 175G having a changed hue after passing through the colored layer 131G is emitted from the pixel 230G. Light 175B having a changed hue after passing through the colored layer 131B is emitted from the pixel 230B.

[0084] A color display can be achieved by changing the hue of the light controlled by the pixel. To achieve a color display, the colors of the colored layers to be combined with the light-emitting colors of the light-emitting elements 170 may be not only a combination of red, green, and blue, but also a combination of yellow, cyan, and magenta. The colors of the colored layers to be combined may be appropriately selected depending on the purpose or application.

[0085] [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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] By using the above materials for the substrate, a lightweight display device can be provided.Furthermore, by using the above materials for the substrate, a display device that is resistant to impact can be provided.Furthermore, by using the above materials for the substrate, a display device that is less likely to break can be provided.

[0090] 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.

[0091] [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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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 and / or alloys. Furthermore, the conductive material may be formed using alloys containing aluminum (aluminum alloys), such as an alloy of aluminum and titanium, an alloy of aluminum and nickel, and 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.

[0096] When the light-emitting element 170 is a light-emitting element having a bottom emission structure (a bottom emission structure), a conductive material that transmits visible light may be used for the electrode 171, and a conductive material that reflects visible light may be used for the electrode 173. Alternatively, when the light-emitting element 170 is used in a display device having a dual emission structure (a double-sided emission structure), a conductive material that transmits visible light may be used for both the electrode 171 and the electrode 173.

[0097] 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, and alloy materials containing these metal materials can be used. Alternatively, nitrides of these 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.

[0098] 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.

[0099] [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.

[0100] 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).

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] In addition, chemical mechanical polishing (CMP) may be performed on the surface of the insulating layer, etc. By performing CMP, the unevenness of the sample surface can be reduced, and the coverage of the insulating layer and conductive layer formed later can be improved.

[0106] [Colored layer] Materials that can be used for the colored layer include metal materials, resin materials, and resin materials containing pigments or dyes.

[0107] [Light blocking layer] Materials that can be used for the light-shielding layer include carbon black, titanium black, metals, metal oxides, and composite oxides containing solid solutions of multiple metal oxides. The light-shielding layer may be a film containing a resin material or a thin film of an inorganic material such as a metal. The light-shielding layer may also be a laminated film of films containing the material of the colored layer. For example, a laminated structure may be used in which a film containing the material used for a colored layer that transmits light of one color and a film containing the material used for a colored layer that transmits light of another color. Using a common material for the colored layer and the light-shielding layer is preferred because it allows for the use of common equipment and simplifies the process.

[0108] [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.

[0109] 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.

[0110] When one of the gate electrodes provided above and below the channel is referred to as a "gate electrode," the other is referred to as a "back gate electrode." When one of the gate electrodes provided above and below the channel is referred to as a "gate," the other is referred to as a "back gate." The gate electrode is sometimes referred to as a "front gate electrode." Similarly, the gate is sometimes referred to as a "front gate."

[0111] For example, the electrode 221 of the transistor 252 can function as a gate electrode, and the electrode 226 of the transistor 252 can function as a back gate electrode. Thus, both the insulating layer 210 and the insulating layer 211 can function as gate insulating layers.

[0112] By providing a gate electrode and a back gate electrode, the semiconductor layer of the transistor can be electrically surrounded by the electric field generated from the gate electrode and the electric field generated from the back gate electrode. A transistor structure in which the electric field generated from the gate electrode and the back gate electrode electrically surrounds the semiconductor layer in which the channel is formed can be called a surrounded channel (S-channel) structure.

[0113] The back gate electrode can function in the same manner as the gate electrode. The potential of the back gate electrode may be the same as that of the gate electrode, or may be ground potential or any other potential. In addition, the threshold voltage of the transistor can be changed by changing the potential of the back gate electrode independently of the gate electrode.

[0114] By providing the gate electrode and the back gate electrode, and by setting both to the same potential, the region through which carriers flow in the semiconductor layer becomes larger in the film thickness direction, and the amount of carrier movement increases, resulting in an increase in the on-state current of the transistor and an increase in field-effect mobility.

[0115] Therefore, the transistor can have a large on-state current relative to the area it occupies. That is, the area occupied by the transistor can be reduced relative to the required on-state current. Therefore, a highly integrated semiconductor device can be realized.

[0116] Furthermore, by using a transistor with a large on-state current in a display device, even if the number of wirings increases when the display device is made larger or has higher resolution, it is possible to reduce signal delays in each wiring, thereby suppressing deterioration in display quality.

[0117] In addition, since the gate electrode and the back gate electrode are formed of conductive layers, they have the function of preventing an electric field generated outside the transistor from acting on the semiconductor layer in which the channel is formed (particularly, an electric field shielding function against static electricity, etc.) Note that the electric field shielding function can be enhanced by forming the back gate electrode larger than the semiconductor layer in a plan view and covering the semiconductor layer with the back gate electrode.

[0118] The gate electrode and back gate electrode each function to shield the external electric field, preventing charges such as charged particles generated above and below the transistor from affecting the channel formation region of the semiconductor layer. As a result, deterioration in stress tests (e.g., Negative Gate Bias-Temperature (NGBT) stress tests (also known as "NBT" or "NBTS"), in which a negative voltage is applied to the gate) is suppressed. Furthermore, the gate electrode and back gate electrode can block the electric field generated by the drain electrode from acting on the semiconductor layer. This suppresses fluctuations in the on-current rise voltage caused by fluctuations in the drain voltage. Note that this effect is particularly pronounced when a potential is applied to the gate electrode and back gate electrode.

[0119] Furthermore, a transistor having a back gate electrode has a smaller threshold voltage change before and after a PGBT (Positive Gate Bias-Temperature) stress test (also referred to as "PBT" or "PBTS") in which a positive voltage is applied to the gate than a transistor without a back gate electrode.

[0120] The BT stress test for NGBT and PGBT is a type of accelerated test that can quickly evaluate the changes in transistor characteristics (aging) that occur over long periods of use. In particular, the amount of change in a transistor's threshold voltage before and after a BT stress test is an important indicator for examining reliability. The smaller the change in threshold voltage before and after a BT stress test, the more reliable the transistor is.

[0121] Furthermore, by providing the gate electrode and the back gate electrode and setting them to the same potential, the amount of variation in threshold voltage is reduced, which also reduces variations in electrical characteristics among a plurality of transistors.

[0122] Furthermore, when light is incident from the back gate electrode side, by forming the back gate electrode using a conductive film having a light-shielding property, the light can be prevented from entering the semiconductor layer from the back gate electrode side, thereby preventing light degradation of the semiconductor layer and deterioration of electrical characteristics such as a shift in the threshold voltage of the transistor.

[0123] [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.

[0124] 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.

[0125] 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.

[0126] <Metal oxides> Here, metal oxides that can be used as oxide semiconductors will be described.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] <Classification of crystal structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 14A, which is a diagram for explaining classification of crystal structures of oxide semiconductors, typically IGZO (metal oxide containing In, Ga, and Zn).

[0131] As shown in FIG. 14A, 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). The "Crystalline" classification excludes single crystal, polycrystal, and completely amorphous (excluding single crystal and polycrystal). "Crystal" includes single crystal and polycrystal.

[0132] The structure within the bold frame in Figure 14A 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."

[0133] The crystalline structure of a film or substrate can be evaluated using X-ray diffraction (XRD) spectroscopy. Figure 14B shows the XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement of a CAAC-IGZO film classified as "Crystalline." 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 14B may be simply referred to as the XRD spectrum in this specification. The composition of the CAAC-IGZO film shown in Figure 14B is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. The thickness of the CAAC-IGZO film shown in Figure 14B is 500 nm.

[0134] In Figure 14(B), the horizontal axis is 2θ [deg.] and the vertical axis is intensity [au]. As shown in Figure 14B, a peak indicating clear crystallinity is detected in the XRD spectrum of the CAAC-IGZO film. Specifically, a peak indicating c-axis orientation is detected near 2θ = 31° in the XRD spectrum of the CAAC-IGZO film. Note that, as shown in Figure 14B, the peak near 2θ = 31° is asymmetrical with respect to the angle at which the peak intensity is detected.

[0135] The crystalline structure of a film or substrate can be evaluated by the diffraction pattern (also called the nanobeam electron diffraction pattern) observed using nanobeam electron diffraction (NBED). Figure 14C shows the diffraction pattern of a CAAC-IGZO film. Figure 14C shows a diffraction pattern observed using NBED, in which an electron beam is incident parallel to the substrate. The composition of the CAAC-IGZO film shown in Figure 14C is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. In nanobeam electron diffraction, electron diffraction is performed using a probe diameter of 1 nm.

[0136] As shown in FIG. 14C, multiple spots indicating c-axis orientation are observed in the diffraction pattern of the CAAC-IGZO film.

[0137] <Oxide semiconductor structure> Note that oxide semiconductors may be classified differently from those shown in FIG. 14A 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.

[0138] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0139] [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.

[0140] 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.

[0141] In addition, in an In-M-Zn oxide (wherein element 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 element M, zinc (Zn), and oxygen (hereinafter referred to as an (M, Zn) layer) are stacked. Note that indium and element M are mutually substituted. Therefore, the (M, Zn) layer may contain indium. Furthermore, the In layer may contain element M. Furthermore, the In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution TEM image, for example.

[0142] 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.

[0143] 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).

[0144] 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. The distortion may also have a pentagonal, heptagonal, or other lattice arrangement. In CAAC-OS, no clear grain boundaries can be identified 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.

[0145] A crystal structure with clear grain boundaries is called polycrystalline. Grain boundaries act as recombination centers, trapping carriers and potentially reducing the on-state current and field-effect mobility of transistors. Therefore, CAAC-OS, which lacks clear grain boundaries, is one of the crystalline oxides with a crystal structure suitable for use in transistor semiconductor layers. 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.

[0146] 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.

[0147] [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.

[0148] [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.

[0149] <Oxide semiconductor structure> Next, the above-mentioned CAC-OS will be described in detail, which relates to the material composition.

[0150] [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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0155] 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.

[0156] 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, giving the CAC-OS 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.

[0157] 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.

[0158] <Transistors containing oxide semiconductors> Next, a case where the oxide semiconductor is used in a transistor will be described.

[0159] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0160] 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 or equal to 1×10 11 cm -3 or less, more preferably 1 × 10 10 cm -3 Less than 1 x 10 -9 cm -3 That is all. 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.

[0161] 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.

[0162] Furthermore, charges trapped in the trap states of an oxide semiconductor take a long time to disappear 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.

[0163] 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.

[0164] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0165] 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 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0166] Furthermore, when an oxide semiconductor contains an alkali metal or alkaline earth metal, defect levels may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or alkaline earth metal is likely to have normally-on characteristics. Therefore, 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:

[0167] 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 3Less than or equal to 1×10 18 atoms / cm 3 Less than 5 × 10, more preferably 17 atoms / cm 3 Do the following:

[0168] 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.

[0169] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0170] <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.

[0171] 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.

[0172] 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.

[0173] 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).

[0174] <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.

[0175] The insulating layers, semiconductor layers, and conductive layers for forming electrodes and wiring that constitute the display device can be formed using methods such as sputtering, chemical vapor deposition (CVD), vacuum evaporation, pulsed laser deposition (PLD), atomic layer deposition (ALD), and plasma enhanced ALD (PEALD). The CVD method may be plasma enhanced chemical vapor deposition (PECVD) or thermal CVD. An example of a thermal CVD method is metal organic chemical vapor deposition (MOCVD).

[0176] 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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] When forming a film by the ALD method, it is preferable to use a gas that does not contain chlorine as a source gas.

[0181] 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 -5 The 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.

[0182] 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.

[0183] When forming an insulating layer, a conductive layer, a semiconductor layer, or the like 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.

[0184] 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.

[0185] When light is used in photolithography, the light used for exposure can 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 can also be performed using immersion exposure technology. Extreme ultraviolet (EUV) light or X-rays can also be used as the light used for exposure. Electron beams can 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.

[0186] The layer (thin film) can be removed (etched) by dry etching, wet etching, etc. These etching methods may also be used in combination.

[0187] The display device 100 described in this embodiment is manufactured by combining a first element substrate 151 (see FIG. 8B) and a second element substrate 152 (see FIG. 11C).

[0188] [First element substrate 151] A method for manufacturing the first element substrate 151 will be described.

[0189] [Process A1] Insulating layers 112 and 113 are formed on substrate 111 (see FIG. 2A). At least one of insulating layers 112 and 113 is preferably made of a material that is difficult for impurities such as hydrogen and water to permeate.

[0190] [Process A2] Next, an electrode 221 is formed over the insulating layer 113. The electrode 221 can be formed in such a manner that a conductive film is formed, a resist mask is formed, the conductive film is etched, and then the resist mask is removed.

[0191] [Process A3] Next, insulating layer 211 is formed on insulating layer 113 and electrode 221. For example, 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 can be used as insulating layer 211. Alternatively, 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 can also be used. Two or more of the above insulating films may be stacked.

[0192] 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.

[0193] When an oxide semiconductor is used for the semiconductor layer 231, an insulating layer having a region in contact with the semiconductor layer 231 is preferably an insulating layer from which oxygen is released by heating (hereinafter also referred to as an "insulating layer containing excess oxygen"). Therefore, when an oxide semiconductor is used for the semiconductor layer 231, the insulating layer 211 is preferably an insulating layer containing excess oxygen.

[0194] 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.

[0195] [Process A4] Next, the semiconductor layer 231 is formed. In this embodiment, an oxide semiconductor layer is formed as the semiconductor layer 231. The oxide semiconductor layer can be formed in such a manner that an oxide semiconductor film is formed, a resist mask is formed, the oxide semiconductor film is etched, and then the resist mask is removed.

[0196] The substrate temperature during deposition of the oxide semiconductor film is preferably 350° C. or lower, more preferably room temperature or higher and 200° C. or lower, and further preferably room temperature or higher and 130° C. or lower.

[0197] The oxide semiconductor film can be formed by sputtering using, for example, either an inert gas or oxygen gas, or both, as a sputtering gas. The flow rate ratio (oxygen partial pressure) of oxygen gas during the formation of the oxide semiconductor film is not particularly limited. However, in order to obtain a transistor with high field-effect mobility, the flow rate ratio (oxygen partial pressure) of oxygen during the formation of the oxide semiconductor film is preferably 0% to 30%, more preferably 5% to 30%, and even more preferably 7% to 15%.

[0198] The oxide semiconductor film preferably contains at least indium or zinc, and particularly preferably contains indium and zinc.

[0199] The oxide semiconductor preferably has an energy gap of 2 eV or more, more preferably 2.5 eV or more, and further preferably 3 eV or more. By using an oxide semiconductor with such a wide energy gap, the off-state current of a transistor can be reduced.

[0200] In particular, semiconductor materials with an energy gap of 2.5 eV or more are preferred because of their high transmittance to visible light.

[0201] The oxide semiconductor film can be formed by sputtering, or by other methods such as PLD, PECVD, thermal CVD, ALD, and vacuum deposition.

[0202] [Process A5] Next, the electrode 224a, the electrode 224b, and the wiring 125 are formed (see FIG. 2B). The electrode 224a, the electrode 224b, and the wiring 125 can be formed by forming a conductive film, forming a resist mask, etching the conductive film, and then removing the resist mask. The electrode 224a and the electrode 224b are each electrically connected to the semiconductor layer 231.

[0203] Note that when the electrodes 224a and 224b are formed, a part of the semiconductor layer 231 that is not covered with the resist mask may be thinned by etching.

[0204] [Process A6] Next, the insulating layer 210 is formed. An oxide insulating layer such as a silicon oxide layer or a silicon oxynitride layer formed in an atmosphere containing oxygen is preferably used as the insulating layer 210. When the oxide insulating layer is formed in an atmosphere containing oxygen, it can be an insulating layer containing excess oxygen.

[0205] [Process A7] Next, an electrode 226 is formed over the insulating layer 210. The electrode 226 has a region overlapping with the semiconductor layer 231. In this manner, the transistor 251 can be formed. Although not shown, the transistor 252 is also formed in a similar manner.

[0206] [Process A8] Next, the insulating layer 213 is formed (see FIG. 2C). The insulating layer 213 is preferably formed from an insulating material that is difficult for oxygen to diffuse or penetrate, such as silicon nitride.

[0207] When the insulating layer 210 contains excess oxygen, oxygen can be efficiently supplied to the oxide semiconductor layer by performing heat treatment on the insulating layer 210 after stacking an insulating film that does not easily diffuse or transmit oxygen. As a result, oxygen vacancies in the oxide semiconductor layer and defects at the interface between the oxide semiconductor layer and the insulating layer 210 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.

[0208] [Process A9] Next, the insulating layer 114 is formed. The insulating layer 114 is a layer on which a display element will be formed later, and therefore preferably functions as a planarizing layer.

[0209] [Process A10] Next, an opening 161 is formed in the insulating layer 114, the insulating layer 213, and the insulating layer 210, reaching the electrode 224a.

[0210] [Process A11] Next, an electrode 171 is formed on the insulating layer 114 (see FIGS. 3A and 3B). FIG. 3A is a schematic perspective view showing a structure provided above the insulating layer 114. To facilitate understanding of the description disclosed in this embodiment, some components are omitted from FIG. 3A. For example, components located below the electrode 171 are omitted. The same applies to FIGS. 4A, 5A, 6A, 7A1, 7A2, 8A, and 9A, which will be described later.

[0211] 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 3 and the like, the direction perpendicular to the surface of the substrate 111 is referred to as the Z direction.

[0212] Fig. 3B is a cross-sectional schematic diagram of the XZ plane overlapping with the portions F1 and F2 indicated by the dashed dotted lines in Fig. 3A, as viewed in the Y direction. The electrode 171 is electrically connected to the electrode 224a.

[0213] 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.

[0214] [Process A12] Next, the EL layer 172 is formed. In this embodiment, the EL layer 172 is formed of an organic EL. The EL layer 172 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 172 be performed so that the temperature applied to the EL layer 172 is equal to or lower than the heat resistance temperature of the EL layer 172.

[0215] [Process A13] Next, the electrode 173 is formed. The electrode 173 is formed using a conductive material that transmits visible light. When the electrode 173 is used as a cathode, the electrode 173 may have a stacked structure of lithium fluoride and ITO, for example.

[0216] [Process A14] Next, a resist mask 179 is formed on the electrode 173 (see FIGS. 4A and 4B). Fig. 4A is a schematic perspective view showing the state in which the resist mask 179 has been formed on the electrode 173. Fig. 4B 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. 4A, as viewed in the Y direction.

[0217] [Process A15] Next, using a resist mask as a mask, portions of electrode 171, EL layer 172, and electrode 173 are selectively removed (see FIGS. 5A and 5B). Fig. 5A is a schematic perspective view showing the state after etching. Fig. 5B is a schematic cross-sectional view of the XZ plane overlapping portions F1 and F2 indicated by the dashed dotted lines in Fig. 5A, viewed in the Y direction.

[0218] The electrode 171, the EL layer 172, and the electrode 173 can be removed (etched) by dry etching, wet etching, or the like. Different etching methods may be used in combination. The electrode 171, the EL layer 172, and the electrode 173 are preferably etched successively (all at once). By successively etching the electrode 171, the EL layer 172, and the electrode 173, it is not necessary to form a resist mask for each layer, which can improve productivity.

[0219] Depending on the etching conditions, 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. By making the side surfaces of the electrode 171, the EL layer 172, and the electrode 173 approximately coincident with each other, it is possible to improve the coverage of an insulating layer or the like in a later step, which is preferable.

[0220] [Process A16] Next, the resist mask 179 is removed (see FIGS. 6A and 6B). In this manner, the light emitting element 170 is formed. FIG. 6A is a schematic perspective view showing the light emitting element 170 formed by etching. FIG. 6B 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. 6A, viewed in the Y direction.

[0221] 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.

[0222] According to one embodiment of the present invention, light-emitting elements that function as pixels can be fabricated separately by selectively and collectively removing parts of the electrode 171 that functions as an anode, the EL layer 172, and the electrode 173 that functions as a cathode. Therefore, light-emitting elements can be fabricated without using a metal mask or with a reduced amount of metal mask used, thereby improving the productivity of display devices.

[0223] For example, when forming the light-emitting elements 170 using a metal mask, it is difficult to make the interval (distance) between two adjacent light-emitting elements 170 20 μm or less due to constraints on dimensional accuracy. According to one embodiment of the present invention, the interval between two adjacent light-emitting elements 170 can be made 20 μm or less. Specifically, the interval between two adjacent light-emitting elements 170 can be made 0.5 μm to 15 μm, preferably 0.5 μm to 10 μm, and more preferably 0.5 μm to 5 μm. This makes it possible to achieve an improved pixel aperture ratio, higher definition, and smaller size.

[0224] [Process A17] Next, an insulating layer 115 is formed to cover the light-emitting element 170 (see FIG. 7B). The insulating layer 115 is preferably made of a material that is resistant to the diffusion of impurities such as water and hydrogen. This allows the insulating layer 115 to function as a barrier film. This configuration effectively prevents impurities from diffusing from the outside into the light-emitting element 170 and the transistor, thereby achieving a highly reliable display device.

[0225] The insulating layer 115 may be, for example, a laminated structure of an aluminum oxide (AlOx) film and a silicon nitride (SiNy) film on the aluminum oxide film, or a laminated structure of an oxide semiconductor (e.g., IGZO) and an aluminum oxide (AlOx) film on the IGZO film. The aluminum oxide film, the silicon nitride film, and the oxide semiconductor film may be formed by ALD, CVD, or sputtering, respectively.

[0226] 7A1 and 7A2 are schematic perspective views showing a state in which an electrode 117, which will be described later, is provided on a light emitting element 170. Fig. 7B is a schematic cross-sectional view of an XZ plane overlapping with portions F1 and F2 indicated by dashed dotted lines in Fig. 7A1, viewed in the Y direction.

[0227] [Process A18] Next, an insulating layer 116 is formed over the insulating layer 115. The insulating layer 116 preferably functions as a planarization layer.

[0228] Furthermore, CMP may be performed on the surface of the insulating layer 116. By performing CMP on the surface of the insulating layer 116, the surface irregularities can be reduced and the coverage of the insulating layer and conductive layer formed thereafter can be improved.

[0229] [Process A19] 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. As shown in FIG. 7A2, a plurality of electrodes 117 may be provided for one light-emitting element 170.

[0230] [Process A20] Next, conductive layer 118 is formed on insulating layer 116 and electrode 117 (see FIGS. 8A and 8B). Fig. 8A is a schematic perspective view showing a state in which conductive layer 118 is provided on light-emitting element 170. Fig. 8B is a schematic cross-sectional view of an XZ plane overlapping portions F1 and F2 indicated by dashed dotted lines in Fig. 8A, viewed in the Y direction.

[0231] The conductive layer 118 is electrically connected to the electrodes 173 of the plurality of 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.

[0232] Furthermore, the conductive layer 118 functions as a cathode auxiliary conductive layer. By providing the conductive layer 118, the potential variation of the cathode (electrode 173) in the entire display region 235 is reduced, and uniform light emission intensity is obtained. Therefore, the display quality of the display device can be improved.

[0233] In this manner, the first element substrate 151 can be fabricated.

[0234] [Variation 1] 9 shows a modified example of the first element substrate 151. In the first element substrate 151, wiring 119 may be provided on the insulating layer 116 and the electrode 117 instead of the conductive layer 118. FIG. 9A is a schematic perspective view showing a state in which wiring 119 is provided on the light-emitting element 170. FIG. 9B 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. 9A, viewed in the Y direction.

[0235] 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 where it overlaps with the light-emitting element 170 is as small as possible. The wiring 119 functions 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.

[0236] 9, 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.

[0237] [Variation 2] 10, an insulating layer 139 may be provided between the insulating layer 114 and the electrode 171. The insulating layer 139 functions as an etching stopper when etching a portion of the electrode 171 functioning as an anode, the EL layer 172, and the electrode 173 functioning as a cathode in step A15.

[0238] A material that is difficult to etch in step A15 is used for insulating layer 139. In particular, when step A15 is performed by dry etching or is performed mainly by dry etching, it is preferable to provide insulating layer 139. Providing insulating layer 139 increases the degree of freedom in the process design of step A15, and can improve productivity and reliability.

[0239] [Second element substrate 152] Next, a method for manufacturing the second element substrate 152 will be described.

[0240] [Process B1] An insulating layer 122 is formed on a substrate 121 (see FIG. 11A). The substrate 121 may be made of the same material as the substrate 111.

[0241] [Process B2] Next, a light-shielding layer 132 is provided on the insulating layer 122 (see FIG. 11B).

[0242] [Process B3] Next, the colored layer 131 is provided on the insulating layer 122 and the light-shielding layer 132 .

[0243] The colored layer 131 is formed using a photosensitive material and can be processed into an island shape by photolithography or the like. The colored layer 131 and the light-shielding layer 132 may be provided as needed. Therefore, there may be cases where at least one of the colored layer 131 and the light-shielding layer 132 is not provided. Note that in the display device 100, the light-shielding layer 132 is provided so as to overlap the peripheral circuit region 232, the peripheral circuit region 233, etc.

[0244] In this embodiment, a colored layer 131R that transmits light in the red color gamut, a colored layer 131G that transmits light in the green color gamut, and a colored layer 131B that transmits light in the blue color gamut are provided. 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.

[0245] [Process B4] Next, an insulating layer 133 is formed on the colored layer 131 and the light-shielding layer 132 (see FIG. 11C).

[0246] The insulating layer 133 preferably functions as a planarizing layer. A resin such as an acrylic resin or an epoxy resin can be suitably used for the insulating layer 133. The insulating layer 133 may also be an inorganic insulating layer.

[0247] In this manner, the second element substrate 152 can be fabricated.

[0248] [Display device 100] Next, a method for manufacturing the display device 100 using the first element substrate 151 and the second element substrate 152 will be described.

[0249] The first element substrate 151 and the second element substrate 152 are bonded together with the adhesive layer 142 sandwiched between them so that the colored layer 131 and the light emitting element 170 face each other (see FIG. 12). At this time, they are bonded together so that the light emitting region of the light emitting element 170 overlaps the colored layer 131.

[0250] Various curing adhesives such as a photo-curing adhesive such as an ultraviolet curing adhesive, a reaction curing adhesive, a thermosetting adhesive, an anaerobic adhesive, etc. may be used as the adhesive layer 142. An adhesive sheet or the like may also be used.

[0251] In this manner, the display device 100 can be fabricated.

[0252] [Modification] 13 shows a cross section of a display device 100A, which is a modified example of the display device 100. The display device 100A has a first element substrate 151 and a second element substrate 152A. The second element substrate 152A is a modified example of the second element substrate 152, and differs in that it includes a touch sensor 370 between the substrate 121 and the colored layer 131. In this embodiment, the touch sensor 370 includes a conductive layer 374, an insulating layer 375, a conductive layer 376a, a conductive layer 376b, a conductive layer 377, and an insulating layer 378.

[0253] The conductive layers 376a, 376b, and 377 are preferably formed of a light-transmitting conductive material. However, a light-transmitting conductive material generally has higher resistivity than a non-light-transmitting conductive material (a light-blocking conductive material). Therefore, in order to achieve a larger and more precise touch sensor, the conductive layers 376a, 376b, and 377 may be formed of a metal material with low resistivity.

[0254] Furthermore, it is preferable to reduce external light reflection when the conductive layers 376a, 376b, and 377 are made of a metal material. Generally, metal materials have high reflectivity, but by performing oxidation treatment or the like, the reflectivity can be reduced and the color can be made darker.

[0255] Furthermore, the conductive layer 376a, the conductive layer 376b, and the conductive layer 377 may be a laminate of a metal layer and a layer with low reflectivity (also referred to as a "dark layer"). Because the dark layer has high resistivity, it is preferable to laminate a metal layer and a dark layer. Examples of the dark layer include a layer containing copper oxide, copper chloride, or tellurium chloride. The dark layer may also be formed using metal fine particles such as Ag particles, Ag fibers, or Cu particles, nanocarbon particles such as carbon nanotubes (CNTs) or graphene, and conductive polymers such as PEDOT, polyaniline, or polypyrrole.

[0256] Furthermore, the touch sensor 370 may be a resistive or capacitive touch sensor, or an optical touch sensor using a photoelectric conversion element. Capacitive touch sensors include surface capacitive touch sensors and projected capacitive touch sensors. Projected capacitive touch sensors include self-capacitive touch sensors and mutual capacitive touch sensors, which differ mainly in their driving methods. The mutual capacitive touch sensor is preferred because it enables simultaneous multi-point detection.

[0257] The other configurations are the same as those of the display device 100, and therefore detailed description thereof will be omitted.

[0258] The touch sensor may also be provided on the outside of the substrate 121. For example, a sheet-like touch sensor may be provided over the display area 235.

[0259] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes or the like.

[0260] (Embodiment 2) In this embodiment, a more specific configuration example of display device 100 will be described. Fig. 15A 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.

[0261] 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."

[0262] 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.

[0263] The display device 100 also has m (m is an integer greater than or equal to 1) wirings 236 that are arranged approximately in parallel and whose potential is controlled by a circuit included in the peripheral circuit region 232, and n (n is an integer greater than or equal to 1) wirings 237 that are arranged approximately in parallel and whose potential is controlled by a circuit included in the peripheral circuit region 233.

[0264] 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. 15B1). 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. 15B2).

[0265] Furthermore, four subpixels may be combined to function as one pixel. For example, a subpixel that controls white light (W) may be added to three subpixels that control red, green, and blue light, respectively (see FIG. 15B3). 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. 15B4). A subpixel that controls white light may be added to three subpixels that control cyan, magenta, and yellow light, respectively (see FIG. 15B5).

[0266] 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.

[0267] 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).

[0268] Furthermore, by arranging the pixels 240 in a 1920 x 1080 matrix, 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") can be realized. Furthermore, by arranging the pixels 240 in a 3840 x 2160 matrix, for example, 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") can be realized. Furthermore, by arranging the pixels 240 in a 7680 x 4320 matrix, for example, 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") can be realized. By increasing the number of pixels 240, a display device 100 capable of full-color display at a resolution of 16K or 32K can also be realized.

[0269] <Circuit configuration example of pixel 230> 16 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.

[0270] 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.

[0271] 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 light-emitting element 170 that functions as a display element 432.

[0272] 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.

[0273] The transistor 436 has a function of controlling writing of a data signal to the node 435 .

[0274] 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.

[0275] The capacitor 433 functions as a storage capacitor for holding data written to the node 435 .

[0276] 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.

[0277] 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.

[0278] One of the anode or the cathode of the light emitting element 170 is electrically connected to the potential supply line VL_b, and the other is electrically connected to a node 437 .

[0279] For example, an organic electroluminescence element (also called an organic EL element) can be used as the light emitting element 170. However, the light emitting element 170 is not limited to this, and for example, an inorganic EL element made of an inorganic material can also be used.

[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 pixel circuits 431 , pixel circuits 431 in each row are selected sequentially by a circuit included in the peripheral circuit region 232 , and a data signal is written to a node 435 by turning on a transistor 436 and a transistor 434 .

[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 light-emitting element 170 emits light with a luminance that corresponds to the amount of current flowing. By performing this process sequentially for each row, an image can be displayed.

[0284] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes or the like.

[0285] (Embodiment 3) In this embodiment, a light-emitting device that can be used as the light-emitting element 170 will be described.

[0286] 17A shows a diagram of a light-emitting device. The light-emitting device shown in FIG. 17A has a first electrode 181, a second electrode 182, and an EL layer 183. The first electrode 181 corresponds to the electrode 171 shown in the above embodiment, the second electrode 182 corresponds to the electrode 173, and the EL layer 183 corresponds to the EL layer 172.

[0287] The EL layer 183 has a light-emitting layer 193, which contains a light-emitting material. Between the light-emitting layer 193 and the first electrode 181, a hole injection layer 191 and a hole transport layer 192 are provided.

[0288] The light-emitting layer 193 may also contain a host material together with the light-emitting material. The host material is an organic compound having carrier-transporting properties. The host material may contain one or more types of host materials. In this case, it is preferable that the multiple organic compounds include an organic compound having electron-transporting properties and an organic compound having hole-transporting properties, because this allows for the carrier balance in the light-emitting layer 193 to be adjusted. The multiple organic compounds may all have electron-transporting properties, but by varying the electron-transporting properties, it is possible to adjust the electron-transporting properties in the light-emitting layer 193. By appropriately adjusting the carrier balance, a light-emitting device with a long lifetime can be provided. An exciplex may also be formed between the multiple organic compounds serving as host materials or between the host material and the light-emitting material. By forming an exciplex having an appropriate emission wavelength, effective energy transfer to the light-emitting material can be achieved, thereby providing a light-emitting device with high efficiency and a long lifetime.

[0289] 17A illustrates the EL layer 183 including the light-emitting layer 193, the hole injection layer 191, the hole transport layer 192, the electron transport layer 194, and the electron transport layer 195. However, the configuration of the light-emitting device is not limited to these. Any of these layers may not be formed, or a layer having another function may be included.

[0290] Next, detailed structures and examples of materials for the light-emitting device will be described. The first electrode 181 is preferably formed using a metal, alloy, conductive compound, or mixture thereof with a large work function (specifically, 4.0 eV or higher). Specific examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). These conductive metal oxide films are usually formed by sputtering, but they may also be prepared by applying a sol-gel method. Note that by using a composite material (described later) for the layer in contact with the first electrode 181 in the EL layer 183, electrode materials can be selected regardless of the work function.

[0291] The EL layer 183 preferably has a layered structure, but the layered structure is not particularly limited, and various layer structures can be applied, such as a hole injection layer, a hole transport layer, an emitting layer, an electron transport layer, an electron injection layer, a carrier blocking layer, an exciton blocking layer, and a charge generation layer. In this embodiment, two types of structures are described: a structure having an electron transport layer 194 and an electron transport layer 195 in addition to a hole injection layer 191, a hole transport layer 192, and an emitting layer 193, as shown in Figure 17A; and a structure having an electron transport layer 194 and a charge generation layer 196 in addition to a hole injection layer 191, a hole transport layer 192, and an emitting layer 193, as shown in Figure 17B. The materials constituting each layer are specifically described below.

[0292] The hole-injection layer 191 is a layer containing a substance having acceptor properties. As the substance having acceptor properties, either an organic compound or an inorganic compound can be used.

[0293] As the acceptor substance, a compound having an electron-withdrawing group (a halogen group or a cyano group) can be used, and examples thereof include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile.

[0294] In addition to the organic compounds described above, other materials that can be used as acceptors include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. The hole injection layer 191 can also be formed using phthalocyanine complex compounds such as phthalocyanine (abbreviated as HPc) and copper phthalocyanine (abbreviated as CuPc), aromatic amine compounds, or polymers such as poly(3,4-ethylenedioxythiophene) / (polystyrene sulfonate) (abbreviated as PEDOT / PSS). Acceptor materials can extract electrons from the adjacent hole transport layer (or hole transport material) when an electric field is applied.

[0295] Alternatively, a composite material in which the above-described acceptor substance is contained in a material having a hole-transport property can be used for the hole-injection layer 191. Note that by using a composite material in which the acceptor substance is contained in a material having a hole-transport property, a material for forming an electrode can be selected regardless of the work function. That is, not only a material with a high work function but also a material with a low work function can be used for the first electrode 181.

[0296] As a material having hole transport properties to be used in the composite material, various organic compounds such as aromatic amine compounds, carbazole derivatives, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.) can be used. Note that as a material having hole transport properties to be used in the composite material, -6 cm 2 It is preferable that the material has a hole mobility of 1 / Vs or more.

[0297] Note that the material having hole-transporting properties used in the composite material is more preferably a substance having a relatively deep HOMO level of −5.7 eV or more and −5.4 eV or less. When the material having hole-transporting properties used in the composite material has a relatively deep HOMO level, injection of holes into the hole-transport layer 192 becomes easy, and a light-emitting device with a long lifetime can be easily obtained.

[0298] By forming the hole injection layer 191, the hole injection property is improved, and a light-emitting device with a low driving voltage can be obtained. In addition, organic compounds having acceptor properties are easy to use because they can be easily vapor-deposited and formed into films.

[0299] The hole transport layer 192 is formed by including a material having a hole transport property. -6 cm 2 It is preferable that the hole-transport layer 192 has a hole mobility of 1 / Vs or more. Examples of the material having a hole-transport property include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). Note that the substances listed as the materials having a hole-transport property used in the composite material of the hole-injection layer 191 can also be suitably used as the material for forming the hole-transport layer 192.

[0300] The light-emitting layer 193 contains a light-emitting substance and a host material. The light-emitting layer 193 may also contain other materials. The light-emitting layer 193 may also be a stack of two layers with different compositions.

[0301] The light-emitting material may be a fluorescent material, a phosphorescent material, a material that exhibits thermally activated delayed fluorescence (TADF), or any other light-emitting material.

[0302] Examples of materials that can be used as the fluorescent substance in the light-emitting layer 193 include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), etc. Other fluorescent substances can also be used.

[0303] When a phosphorescent material is used as the light-emitting material in the light-emitting layer 193, usable materials include, for example, organometallic iridium complexes having a 4H-triazole skeleton, organometallic iridium complexes having a 1H-triazole skeleton, organometallic iridium complexes having an imidazole skeleton, and organometallic iridium complexes having a phenylpyridine derivative having an electron-withdrawing group as a ligand. These are compounds that exhibit blue phosphorescence and have an emission wavelength peak in the range of 440 nm to 520 nm.

[0304] Other examples include organometallic iridium complexes having a pyrimidine skeleton, organometallic iridium complexes having a pyrazine skeleton, organometallic iridium complexes having a pyridine skeleton, and rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]). These are compounds that primarily exhibit green phosphorescence, with a peak emission wavelength between 500 nm and 600 nm. Organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because of their outstanding reliability and luminous efficiency.

[0305] Other examples include organometallic iridium complexes having a pyrimidine skeleton, organometallic iridium complexes having a pyrazine skeleton, organometallic iridium complexes having a pyridine skeleton, platinum complexes, and rare earth metal complexes. These are compounds that exhibit red phosphorescence, with an emission peak between 600 nm and 700 nm. Furthermore, organometallic iridium complexes having a pyrazine skeleton can emit red light with good chromaticity.

[0306] In addition to the phosphorescent compounds described above, known phosphorescent light-emitting substances may be selected and used.

[0307] TADF materials include fullerene and its derivatives, acridine and its derivatives, eosin derivatives, etc. Also available are metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd).

[0308] TADF materials are materials with a small difference between the S1 and T1 levels, and have the ability to convert triplet excitation energy to singlet excitation energy through reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy (reverse intersystem crossing) using a small amount of thermal energy, allowing for efficient generation of a singlet excited state. Triplet excitation energy can also be converted into light emission.

[0309] Furthermore, exciplexes (also known as exciplexes), which form an excited state with two types of substances, have an extremely small difference between the S1 and T1 levels and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0310] Note that the T1 level can be measured using a phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K). For a TADF material, when a tangent line is drawn at the base of the fluorescence spectrum on the short wavelength side and the energy of the wavelength of the extrapolated line is taken as the S1 level, and a tangent line is drawn at the base of the phosphorescence spectrum on the short wavelength side and the energy of the wavelength of the extrapolated line is taken as the T1 level, the difference between S1 and T1 is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0311] When a TADF material is used as a light-emitting material, the S1 level of the host material is preferably higher than the S1 level of the TADF material, and the T1 level of the host material is preferably higher than the T1 level of the TADF material.

[0312] As the host material of the light-emitting layer, various carrier transporting materials such as a material having an electron transporting property, a material having a hole transporting property, and the above-mentioned TADF material can be used.

[0313] As a material having hole transport properties, an organic compound having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton is preferred. Examples include a compound having an aromatic amine skeleton, a compound having a carbazole skeleton, a compound having a thiophene skeleton, and a compound having a furan skeleton. Among the above, a compound having an aromatic amine skeleton and a compound having a carbazole skeleton are preferred because they have good reliability, high hole transport properties, and contribute to reducing driving voltage.

[0314] As a material having electron transport properties, for example, a metal complex or an organic compound having a π-electron-deficient heteroaromatic ring skeleton is preferable. Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include heterocyclic compounds having a polyazole skeleton, heterocyclic compounds having a diazine skeleton, heterocyclic compounds having a triazine skeleton, and heterocyclic compounds having a pyridine skeleton. Among the above, heterocyclic compounds having a diazine skeleton, heterocyclic compounds having a triazine skeleton, and heterocyclic compounds having a pyridine skeleton are preferred because of their high reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton have high electron transport properties and contribute to reducing driving voltage.

[0315] The TADF materials that can be used as host materials are the same as those listed above. When a TADF material is used as a host material, the triplet excitation energy generated in the TADF material is converted to singlet excitation energy through reverse intersystem crossing, and the energy is then transferred to the light-emitting material, thereby improving the luminous efficiency of the light-emitting device.

[0316] When a fluorescent emitting substance is used as the emitting substance, a material having an anthracene skeleton is suitable as the host material. When a substance having an anthracene skeleton is used as the host material for the fluorescent emitting substance, an emitting layer having good luminous efficiency and durability can be realized.

[0317] The electron-transporting layer 194 is a layer containing a substance having an electron-transporting property. As the substance having an electron-transporting property, any of the substances exemplified above as the host material having an electron-transporting property can be used.

[0318] The electron transport layer 194 has an electron mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 / Vs or less. By reducing the electron transport property of the electron-transport layer 194, the amount of electrons injected into the light-emitting layer can be controlled, and the light-emitting layer can be prevented from becoming electron-excessive. The electron-transport layer preferably contains a material having electron-transport properties and an alkali metal or an element, compound, or complex of the alkali metal. These configurations are particularly preferable because they improve the lifetime when the hole-injection layer is formed as a composite material and the material having hole-transport properties in the composite material has a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. In this case, the material having electron-transport properties preferably has a HOMO level of -6.0 eV or more.

[0319] Between the electron transport layer 194 and the second electrode 182, a layer containing an alkali metal or alkaline earth metal, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF), or 8-hydroxyquinolinato-lithium (abbreviated as Liq), or a compound thereof, may be provided as the electron transport layer 195. The electron transport layer 195 may be a layer made of a substance having electron transport properties containing an alkali metal or alkaline earth metal or a compound thereof, or may use an electride. Examples of the electride include a substance in which electrons are highly concentrated in a mixed oxide of calcium and aluminum.

[0320] Note that a layer containing a substance having electron transport properties (preferably an organic compound having a bipyridine skeleton) containing a fluoride of the alkali metal or alkaline earth metal at a concentration (50 wt % or more) sufficient to form a microcrystalline state can also be used as the electron-transporting layer 195. Since this layer has a low refractive index, it is possible to provide a light-emitting device with better external quantum efficiency.

[0321] Alternatively, a charge generation layer 196 may be provided instead of the electron transport layer 195 ( FIG. 17B ). The charge generation layer 196 is a layer that can inject holes into a layer in contact with the cathode side of the charge generation layer 196 and electrons into a layer in contact with the anode side of the charge generation layer 196 by applying a potential thereto. The charge generation layer 196 includes at least a P-type layer 197. The P-type layer 197 is preferably formed using the composite material listed above as a material that can form the hole injection layer 191. The P-type layer 197 may also be formed by stacking a film containing an acceptor material and a film containing a hole transport material, both of which are materials that form the composite material. By applying a potential to the P-type layer 197, electrons are injected into the electron transport layer 194 and holes are injected into the second electrode 182, which is the cathode, thereby operating the light-emitting device. Furthermore, since the organic compound according to one embodiment of the present invention has a low refractive index, using the P-type layer 197 can provide a light-emitting device with excellent external quantum efficiency.

[0322] It is preferable that the charge generating layer 196 be provided with either or both of an electron relay layer 198 and an electron injection buffer layer 199 in addition to the P-type layer 197 .

[0323] The electron relay layer 198 contains at least a substance having electron transport properties and has the function of preventing interaction between the electron injection buffer layer 199 and the P-type layer 197 and smoothly transferring electrons. The LUMO level of the substance having electron transport properties contained in the electron relay layer 198 is preferably between the LUMO level of the acceptor substance in the P-type layer 197 and the LUMO level of the substance contained in the layer of the electron transport layer 194 that is in contact with the charge generation layer 196. The specific energy level of the LUMO level of the substance having electron transport properties used in the electron relay layer 198 is −5.0 eV or higher, preferably −5.0 eV or higher and −3.0 eV or lower. Note that the substance having electron transport properties used in the electron relay layer 198 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0324] The electron injection buffer layer 199 can be made of a material with high electron injection properties, such as alkali metals, alkaline earth metals, rare earth metals, and their compounds (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)).

[0325] When the electron-injection buffer layer 199 is formed to contain a substance having electron-transporting properties and a donor substance, examples of the donor substance include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), and rare earth metal compounds (including oxides, halides, and carbonates)), as well as organic compounds such as tetrathianaphthacene (abbreviation: TTN), nickelocene, and decamethylnickelocene. Note that the substance having electron-transporting properties can be formed using the same materials as those constituting the electron-transporting layer 194 described above.

[0326] The second electrode 182 can be formed from a metal, alloy, electrically conductive compound, or mixture thereof with a low work function (specifically, 3.8 eV or less). Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing these metals (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these metals. However, by providing an electron injection layer between the second electrode 182 and the electron transport layer, various conductive materials, such as Al, Ag, ITO, and indium tin oxide containing silicon or silicon oxide, can be used for the second electrode 182, regardless of the magnitude of the work function. These conductive materials can be deposited using dry methods such as vacuum deposition or sputtering, inkjet printing, spin coating, or the like. Alternatively, the layer may be formed by a wet method using a sol-gel method, or by a wet method using a paste of a metal material.

[0327] In addition, various methods, whether dry or wet, can be used to form the EL layer 183. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, or spin coating may be used.

[0328] Furthermore, the above-mentioned electrodes or layers may be formed using different film formation methods.

[0329] The configuration of the layers provided between the first electrode 181 and the second electrode 182 is not limited to the above. However, a configuration in which a light-emitting region where holes and electrons recombine is provided at a location away from the first electrode 181 and the second electrode 182 is preferable so as to suppress quenching caused by the proximity of the light-emitting region to the metal used in the electrode or the carrier injection layer.

[0330] Furthermore, the hole transport layer and electron transport layer in contact with the light-emitting layer 193, particularly the carrier transport layer close to the recombination region in the light-emitting layer 193, are preferably made of a material having a band gap larger than the band gap of the light-emitting material constituting the light-emitting layer or the light-emitting material contained in the light-emitting layer, in order to suppress energy transfer from excitons generated in the light-emitting layer.

[0331] Next, an embodiment of a light-emitting device having a configuration in which multiple light-emitting units are stacked (also referred to as a stacked element or a tandem element) will be described with reference to FIG. 17C. This light-emitting device has multiple light-emitting units between an anode and a cathode. One light-emitting unit has a configuration substantially similar to that of the EL layer 183 shown in FIG. 17A. In other words, the light-emitting device shown in FIG. 17C is a light-emitting device having multiple light-emitting units, and the light-emitting device shown in FIG. 17A or 17B can be said to be a light-emitting device having one light-emitting unit.

[0332] 17C, a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between an anode 501 and a cathode 502, and a charge generation layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The anode 501 and the cathode 502 correspond to the first electrode 181 and the second electrode 182 in FIG. 17A, respectively, and the same electrodes as those described in the description of FIG. 17A can be applied to them. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations.

[0333] The charge generation layer 513 has a function of injecting electrons into one light-emitting unit and injecting holes into the other light-emitting unit when a voltage is applied between the anode 501 and the cathode 502. That is, in FIG. 17C , when a voltage is applied so that the potential of the anode is higher than the potential of the cathode, the charge generation layer 513 only needs to inject electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0334] The charge generation layer 513 is preferably formed to have the same structure as the charge generation layer 196 described in FIG. 17B. A composite material of an organic compound and a metal oxide has excellent carrier injection and carrier transport properties, and therefore can achieve low-voltage driving and low-current driving. Note that when the anode side surface of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also serve as the hole injection layer of the light-emitting unit, and therefore the light-emitting unit does not need to be provided with a hole injection layer.

[0335] Furthermore, when the electron injection buffer layer 199 is provided in the charge generation layer 513, the electron injection buffer layer 199 plays the role of an electron injection layer in the light-emitting unit on the anode side, so that it is not necessarily necessary to form an electron injection layer in the light-emitting unit on the anode side.

[0336] 17C illustrates a light-emitting device having two light-emitting units, but the present invention can be applied to a light-emitting device having three or more stacked light-emitting units. By arranging a plurality of light-emitting units between a pair of electrodes and separating them with a charge-generating layer 513, as in the light-emitting device according to the present embodiment, it is possible to realize a device that can emit high-intensity light while maintaining a low current density and has a long life. Furthermore, it is possible to realize a light-emitting device that can be driven at a low voltage and consumes little power.

[0337] Furthermore, by making each light-emitting unit emit a different light color, the light-emitting device as a whole can emit light of a desired color. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as a whole by obtaining red and green light from the first light-emitting unit and blue light from the second light-emitting unit.

[0338] The above-described EL layer 183, the first light-emitting unit 511, the second light-emitting unit 512, the charge generation layer, and the electrodes can be formed by, for example, vapor deposition (including vacuum deposition), droplet discharge (also called ink-jet), coating, gravure printing, etc. They may also contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendrimers), or polymer materials.

[0339] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes or the like.

[0340] (Fourth embodiment) In this embodiment, electronic devices to which a display device according to one embodiment of the present invention can be applied will be described.

[0341] 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.

[0342] 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, hot 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 storage devices may also be included in the category of electronic devices. Examples of such mobile vehicles include electric vehicles (EVs), hybrid vehicles (HVs) that combine internal combustion engines and electric motors, plug-in hybrid vehicles (PHVs), 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, satellites, space probes, planetary probes, and spacecraft.

[0343] 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.

[0344] An electronic device according to one embodiment of the present invention may include a secondary battery, and it is preferable that the secondary battery can be charged using contactless power transmission.

[0345] 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.

[0346] 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.

[0347] 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).

[0348] 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.

[0349] 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.

[0350] A display device according to one embodiment of the present invention can display extremely 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.

[0351] 18A 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, a cable 815, and the like. A battery 816 is built into the mounting portion 811. A display device according to one embodiment of the present invention can be used as the display portion 814.

[0352] 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 eyeballs and / or eyelids, 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.

[0353] 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.

[0354] 18B shows the appearance of head-mounted display 820. Head-mounted display 820 is a goggle-type information processing device.

[0355] The head-mounted display 820 has a housing 821, two display units 822, an operation button 823, and a band-shaped fixture 824. 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 / or chromaticity of light from the display unit changes 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.

[0356] The operation button 823 has functions such as a power button, etc. In addition to the operation button 823, other buttons may be provided.

[0357] 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.

[0358] FIG. 18C shows the appearance of camera 830 with viewfinder 840 attached.

[0359] 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.

[0360] Here, the camera 830 is configured such that the lens 836 can be removed from the housing 831 and replaced, but the lens 836 and the housing may be integrated.

[0361] 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 also be captured by touching the display unit 832.

[0362] 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.

[0363] The finder 840 includes a housing 841, a display unit 842, a button 843, and the like.

[0364] 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.

[0365] 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.

[0366] 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.

[0367] Note that in FIG. 18C, 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.

[0368] 18D 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.

[0369] 18E 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.

[0370] 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.

[0371] 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.

[0372] 18F 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.

[0373] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiment modes or the like. [Explanation of symbols]

[0374] 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, 125: wiring, 131: colored layer, 132: light-shielding layer, 133: insulating layer, 138: connection layer, 139: insulating layer, 142: adhesive layer, 151: element substrate, 152: element substrate

Claims

1. forming an anode on the insulating layer; forming an EL layer on the anode; forming a cathode on the EL layer; selectively removing a portion of each of the anode, the EL layer, and the cathode to form a plurality of light-emitting elements; forming a conductive layer covering the plurality of light-emitting elements; the step of selectively removing a portion of the anode, the EL layer, and the cathode is performed collectively using a resist mask; the cathode of each of the plurality of light-emitting elements is electrically connected to the conductive layer; The method for manufacturing a display device, wherein the conductive layer has light-transmitting properties.

2. forming an anode on the insulating layer; forming an EL layer on the anode; forming a cathode on the EL layer; selectively removing portions of the anode, the EL layer, and the cathode to form a plurality of light-emitting elements; forming a conductive layer on the plurality of light-emitting elements; the step of selectively removing a portion of the anode, the EL layer, and the cathode is performed collectively using a resist mask; The method for manufacturing a display device includes: forming a plurality of light-emitting elements, the cathodes of which are electrically connected to the conductive layer in at least some of the light-emitting elements adjacent to each other;

3. In claim 1 or claim 2, forming a plurality of transistors on a substrate; forming the insulating layer on the plurality of transistors; The method for manufacturing a display device, wherein the insulating layer has a surface on which the insulating layer is formed with reduced irregularities.

4. In claim 3, A method for manufacturing a display device, wherein the transistor includes an oxide semiconductor.

5. In claim 4, The method for manufacturing a display device, wherein the oxide semiconductor contains at least one of indium and zinc.

6. In any one of claims 1 to 5, The method for manufacturing a display device, wherein the distance between two adjacent light-emitting elements is 10 μm or less.

7. In any one of claims 1 to 6, The method for manufacturing a display device, wherein the light-emitting element is a top-emission type.

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