JP2018077376A - Display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display with good visibility.SOLUTION: An area with light transmissivity is provided on at least one of a transistor, a capacitive element, and a wire of a pixel circuit. A liquid crystal device is provided on a light emitting device with the pixel circuit therebetween. Light emitted from the light emitting device is emitted to the outside through the pixel circuit and liquid crystal device. External light made incident through the liquid crystal device transmits through the pixel circuit, is reflected on a reflecting electrode of the light emitting device, and is emitted again to the outside through the pixel circuit and liquid crystal device. The transistor is preferably a bottom gate type transistor.SELECTED DRAWING: Figure 17

Description

One embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the invention disclosed in this specification and the like relates to a process, a machine, a manufacture, or a composition (composition of matter). In particular, the present invention relates to a display device or a method for manufacturing the display device.

Note that in this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. A display device (a liquid crystal display device, a light-emitting display device, or the like), a projection device, a lighting device, an electro-optical device, a power storage device, a memory device, a semiconductor circuit, an imaging device, an electronic device, or the like may include a semiconductor device.

Electronic devices typified by mobile devices such as personal computers (PCs), notebook PCs, electronic books, tablets, and smartphones are widespread. Display devices used for electronic devices such as mobile devices are required to perform display suitable for the brightness of the environment used such as outdoor environment or indoor environment.

As a display device that realizes such a requirement, a display device in which a reflective liquid crystal element and an EL (Electro Luminescence) element are provided in one pixel has been proposed (Patent Document 1). Patent Document 1 discloses a configuration in which an opening is provided in a part of a reflective electrode included in a reflective liquid crystal element, and an EL element is provided in a region corresponding to the opening.

JP 2001-66593 A

As disclosed in Patent Document 1, development of a display device having a configuration in which a plurality of display elements (a reflective liquid crystal element and an EL element) are provided is in progress. On the other hand, further improvement in visibility, display quality, power consumption, reliability, or cost is required.

An object of one embodiment of the present invention is to provide a display device, an electronic device, or the like with high visibility. Another object is to provide a display device or an electronic device with high display quality. Another object is to provide a display device or an electronic device with low power consumption. Another object is to provide a display device or an electronic device with favorable productivity. Another object is to provide a display device or an electronic device with favorable reliability. Another object is to provide a novel display device, an electronic device, or the like.

Note that the description of these problems does not disturb the existence of other problems. Note that one embodiment of the present invention does not have to solve all of these problems. Issues other than these will be apparent from the description of the specification, drawings, claims, etc., and other issues can be extracted from the descriptions of the specification, drawings, claims, etc. It is.

A light-transmitting region is provided in at least one of a transistor, a capacitor, and a wiring included in the pixel circuit. A liquid crystal element and a light emitting element are provided so as to overlap each other with a pixel circuit interposed therebetween. The light emitted from the light emitting element is transmitted to the outside through the pixel circuit and the liquid crystal element. External light incident through the liquid crystal element is transmitted through the pixel circuit, reflected by the reflective electrode of the light emitting element, and again passes through the pixel circuit and the liquid crystal element and is emitted to the outside.

One embodiment of the present invention is a display device including a liquid crystal element, a light-emitting element, and a transistor. The transistor is provided between the liquid crystal element and the light-emitting element. The liquid crystal element includes the first electrode. And the second electrode and the liquid crystal layer, the light-emitting element includes the third electrode, the fourth electrode, and the organic layer, and the first electrode and the second electrode are The first electrode has a region that reflects visible light, and light emitted from the light-emitting element passes through the liquid crystal element to the outside. One of the third electrode and the fourth electrode is reflected by external light incident through the liquid crystal element, and the transistor is a bottom-gate display device.

The transistor includes a gate electrode, a source electrode, a drain electrode, and a semiconductor layer. At least one of the gate electrode, the source electrode, the drain electrode, and the semiconductor layer preferably has a region that transmits visible light. For example, it is preferable to use a material containing a metal oxide.

The other of the third electrode and the fourth electrode has a region sandwiched between the one electrode and the liquid crystal element.

One embodiment of the present invention includes a display region and a peripheral circuit region. The display region includes a first transistor, a liquid crystal element, and a light-emitting element. The peripheral circuit region includes a second region. The liquid crystal element and the light-emitting element each include a region overlapping with each other with the first transistor interposed therebetween. At least one of the gate electrode, the source electrode, and the drain electrode included in the first transistor transmits visible light. The gate electrode, the source electrode, and the drain electrode that have a transmitting region and that the second transistor has have a region that blocks visible light, and either one or both of the first transistor and the second transistor Is a bottom gate type display device.

Light emitted from the light-emitting element passes through the first transistor and the liquid crystal element and is extracted to the outside. External light incident through the liquid crystal element is reflected by one of the pair of electrodes included in the light-emitting element.

For example, the gate electrode of the first transistor is preferably formed using a metal oxide. The gate electrode of the second transistor is preferably formed of metal, for example.

According to one embodiment of the present invention, a display device or an electronic device with favorable visibility can be provided. Alternatively, a display device or an electronic device with high display quality can be provided. Alternatively, a display device or an electronic device with low power consumption can be provided. Alternatively, a display device or an electronic device with high productivity can be provided. Alternatively, a display device or an electronic device with favorable reliability can be provided. Alternatively, a novel display device or electronic device can be provided.

Note that the description of these effects does not disturb the existence of other effects. Note that one embodiment of the present invention need not have all of these effects. It should be noted that the effects other than these are naturally obvious from the description of the specification, drawings, claims, etc., and it is possible to extract the other effects from the descriptions of the specification, drawings, claims, etc. It is.

FIG. 6 illustrates an example of a display device. 2A and 2B illustrate a configuration example of a pixel circuit and a transmissive portion and a light shielding portion of the pixel circuit. FIG. 6 illustrates an example of a display device. FIG. 6 illustrates an example of a display device. FIG. 6 illustrates an example of a display device. FIG. 6 illustrates an example of a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. FIG. 6 illustrates an example of a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate an example of a method for manufacturing a display device. 8A and 8B illustrate a structure example of a display device. 8A and 8B illustrate a circuit configuration example of a pixel. 4A and 4B illustrate a circuit configuration example and a planar configuration example of a pixel. 8A and 8B each illustrate a use example of an electronic device for each display mode. 10A and 10B are a schematic diagram and a state transition diagram illustrating a configuration example of a display device. The circuit diagram and timing chart explaining an operation mode. The block diagram and timing chart figure of a touch sensor. The circuit diagram of a touch sensor. The block diagram and timing chart figure of a display apparatus. FIG. 6 illustrates operations of a display device and a touch sensor. FIG. 6 illustrates operations of a display device and a touch sensor. 4A and 4B are a top view and cross-sectional views illustrating an example of a transistor used for a display device. 4A and 4B are a top view and cross-sectional views illustrating an example of a transistor used for a display device. 4A and 4B are a top view and cross-sectional views illustrating an example of a transistor used for a display device. The figure explaining the measurement result of the XRD spectrum of a sample. The figure explaining the TEM image of a sample, and an electron beam diffraction pattern. The figure explaining the EDX mapping of a sample. FIG. 14 illustrates an example of an electronic device.

Embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated.

In addition, the position, size, range, and the like of each component illustrated in the drawings and the like may not represent the actual position, size, range, or the like in order to facilitate understanding of the invention. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like. For example, in an actual manufacturing process, a layer or a resist mask may be unintentionally lost due to a process such as etching, but may be omitted to facilitate understanding of the invention.

In particular, in a top view (also referred to as a “plan view”), a perspective view, and the like, some components may not be described in order to facilitate understanding of the invention. Moreover, description of some hidden lines may be omitted.

In the present specification and the like, ordinal numbers such as “first” and “second” are used to avoid confusion between components, and do not indicate any order or order such as process order or stacking order. In addition, even in terms that do not have an ordinal number in this specification and the like, an ordinal number may be added in the claims to avoid confusion between the constituent elements. In addition, the ordinal numbers given in this specification and the like may differ from the ordinal numbers given in the claims. Even in the present specification and the like, terms with ordinal numbers are sometimes omitted in the claims.

Further, in this specification and the like, the terms “electrode” and “wiring” 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 a case where a plurality of “electrodes” and “wirings” are provided integrally.

Note that the channel length refers to, for example, a region where a semiconductor (or a portion where current flows in the semiconductor when the transistor is on) and a gate electrode overlap with each other in a top view of the transistor, or a region where a channel is formed The distance between the source (source region or source electrode) and the drain (drain region or drain electrode) in FIG. Note that in one transistor, the channel length is not necessarily the same in all regions. That is, the channel length of one transistor may not be fixed to one value. Therefore, in this specification, the channel length is any one of values, the maximum value, the minimum value, or the average value in a region where a channel is formed.

The channel width is, for example, a region in which a semiconductor (or a portion in which a current flows in the semiconductor when the transistor is on) and a gate electrode overlap each other, or a source and a drain in a region where a channel is formed. This is the length of the part. Note that in one transistor, the channel width is not necessarily the same in all regions. That is, the channel width of one transistor may not be fixed to one value. Therefore, in this specification, the channel width is any one of values, the maximum value, the minimum value, or the average value in a region where a channel is formed.

Note that depending on the structure of the transistor, the channel width in a region where a channel is actually formed (hereinafter also referred to as “effective channel width”) and the channel width (hereinafter “apparently” shown in the top view of the transistor). Sometimes referred to as “channel width”). For example, when the gate electrode covers the side surface of the semiconductor layer, the effective channel width may be larger than the apparent channel width, and the influence may not be negligible. For example, in a fine transistor whose gate electrode covers a side surface of a semiconductor, the ratio of a channel formation region formed on the side surface of the semiconductor may increase. In that case, the effective channel width is larger than the apparent channel width.

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

Therefore, in this specification, the apparent channel width may be referred to as “surrounded channel width (SCW)”. In this specification, in the case where the term “channel width” is simply used, it may denote an enclosed channel width or an apparent channel width. Alternatively, in this specification, in the case where the term “channel width” is simply used, it may denote an effective channel width. Note that the channel length, channel width, effective channel width, apparent channel width, enclosed channel width, and the like can be determined by analyzing a cross-sectional TEM image or the like.

Note that in the case where the field-effect mobility of a transistor, the current value per channel width, and the like are calculated and calculated, the calculation may be performed using the enclosed channel width. In that case, the value may be different from that calculated using the effective channel width.

In this specification and the like, when a resist mask is formed by photolithography and an etching process (removal process) is performed thereafter, the resist mask is removed after the etching process is finished unless otherwise specified. And

Note that the terms “film” and “layer” can be interchanged with each other depending on the case or circumstances. For example, the term “conductive layer” may be changed to the term “conductive film”. Alternatively, for example, the term “insulating film” may be changed to the term “insulating layer” in some cases.

In this specification and the like, a transistor is an element having at least three terminals including a gate, a drain, and a source. A channel region is provided between the drain (drain terminal, drain region or drain electrode) and the source (source terminal, source region or source electrode), and a current flows through the drain, channel region, and source. It is something that can be done. Note that in this specification and the like, a channel region refers to a region through which a current mainly flows.

The transistors described in this specification and the like are enhancement-type (normally-off) field-effect transistors unless otherwise specified. The transistors described in this specification and the like are n-channel transistors unless otherwise specified. Therefore, the threshold voltage (also referred to as “Vth”) is greater than 0 V unless otherwise specified.

Note that in this specification and the like, Vth of a transistor having a back gate refers to Vth when the potential of the back gate is the same as that of the source or the gate unless otherwise specified.

In this specification and the like, unless otherwise specified, off-state current refers to drain current when a transistor is off (also referred to as a non-conduction state or a cutoff state). In the n-channel transistor, the potential difference between the gate and the source (hereinafter also referred to as “Vg”) with respect to the source is lower than the threshold voltage Vth unless otherwise specified. A state, a p-channel transistor, refers to a state where the voltage Vg between the gate and the source is higher than the threshold voltage Vth. For example, the off-state current of an n-channel transistor sometimes refers to a drain current when Vg is lower than a threshold voltage (hereinafter also referred to as “Vth”).

The off-state current of the transistor may depend on Vg. Therefore, the off-state current of the transistor being I or less sometimes means that there exists a value of Vg at which the off-state current of the transistor is I or less. The off-state current of a transistor may refer to an off-state current in an off state at a predetermined Vg, an off state at a Vg within a predetermined range, or an off state at Vg at which a sufficiently reduced off current is obtained.

As an example, when Vth is 0.5 V, the drain current when Vg is 0.5 V is 1 × 10 ⁻⁹ A, the drain current when Vg is 0.1 V is 1 × 10 ⁻¹³ A, and Vg is − Assume an n-channel transistor in which the drain current at 0.5 V is 1 × 10 ⁻¹⁹ A and the drain current at Vg is −0.8 V is 1 × 10 ⁻²² A. Since the drain current of the transistor is 1 × 10 ⁻¹⁹ A or less when Vg is −0.5 V or Vg is −0.5 V to −0.8 V, the off-state current of the transistor is 1 It may be said that it is below ^x10 <^-19> A. Since there is Vg at which the drain current of the transistor is 1 × 10 ⁻²² A or less, the off-state current of the transistor may be 1 × 10 ⁻²² A or less.

The off-state current of a transistor may depend on temperature. In this specification, the off-state current may represent an off-state current at room temperature (RT: Room Temperature), 60 ° C., 85 ° C., 95 ° C., or 125 ° C. unless otherwise specified. Alternatively, an off-state current at a temperature at which reliability of the semiconductor device including the transistor is guaranteed, or a temperature at which the semiconductor device including the transistor is used (for example, a temperature of 5 ° C. to 35 ° C.) May be represented. The off-state current of the transistor is I or less means that RT, 60 ° C., 85 ° C., 95 ° C., 125 ° C., the temperature at which the reliability of the semiconductor device including the transistor is guaranteed, or the transistor is included. There may be a case where there is a value of Vg at which the off-state current of a transistor is I or less at a temperature (for example, a temperature of 5 ° C. or more and 35 ° C. or less) at which a semiconductor device or the like is used.

The off-state current of the transistor may depend on a voltage between the drain and the source (hereinafter also referred to as “Vd”) with respect to the source. In this specification, unless otherwise specified, Vd is 0.1 V, 0.8 V, 1 V, 1.2 V, 1.8 V, 2.5 V, 3 V, 3.3 V, 10 V, 12 V, 16 V, unless otherwise specified. Or an off-current at 20V. Alternatively, Vd in which reliability of a semiconductor device or the like including the transistor is guaranteed or an off-current in Vd used in the semiconductor device or the like including the transistor may be represented. The off-state current of the transistor is equal to or less than I means that Vd is 0.1V, 0.8V, 1V, 1.2V, 1.8V, 2.5V, 3V, 3.3V, 10V, 12V, 16V, 20V There is a value of Vg at which the off-state current of the transistor is less than or equal to I in Vd in which the reliability of the semiconductor device including the transistor is guaranteed or Vd used in the semiconductor device or the like including the transistor May be pointed to.

In the description of the off-state current, the drain may be read as the source. That is, the off-state current sometimes refers to a current that flows through the source when the transistor is off.

In this specification and the like, the term “leakage current” may be used in the same meaning as off-state current. In this specification and the like, off-state current may refer to current that flows between a source and a drain when a transistor is off, for example.

In the present specification and the like, the terms “upper” and “lower” do not limit that the positional relationship between the components is directly above or directly below and is in direct contact. For example, in the expression “electrode B on the insulating layer A”, the electrode B does not need to be provided directly on the insulating layer A, and another configuration is provided between the insulating layer A and the electrode B. Do not exclude things that contain elements.

Further, in this specification, “parallel” means a state in which two straight lines are arranged at an angle of −10 ° to 10 °, unless otherwise specified. Therefore, the case of −5 ° to 5 ° is also included. In addition, “substantially parallel” means a state in which two straight lines are arranged at an angle of −30 ° to 30 °, unless otherwise specified. “Vertical” and “orthogonal” refer to a state in which two straight lines are arranged at an angle of 80 ° or more and 100 ° or less, unless otherwise specified. Therefore, the case of 85 ° to 95 ° is also included. In addition, “substantially vertical” refers to a state in which two straight lines are arranged at an angle of 60 ° or more and 120 ° or less, unless otherwise specified.

In addition, in this specification, etc., the terms “same”, “same”, “equal”, “uniform” (including these synonyms), etc. with respect to the count value and the measured value, unless otherwise specified. And an error of plus or minus 20%.

In this specification and the like, “having translucency” means that the transmittance in the visible light region (wavelength 400 nm to 800 nm) is 20% or more.

(Embodiment 1)
A display device 100 of one embodiment of the present invention is described with reference to drawings.

<Configuration example>
FIG. 1A is a schematic perspective view of the display device 100. The display device 100 has a structure in which a substrate 351 and a substrate 361 are attached to each other. In FIG. 1, the substrate 361 is clearly indicated by a broken line.

The display device 100 includes a display area 235, a peripheral circuit area 234, a wiring 365, and the like. FIG. 1 shows an example in which an IC (integrated circuit) 373 and an FPC 372 are mounted on the display device 100. Therefore, the structure illustrated in FIG. 1A can also be referred to as a display module including the display device 100, an IC, and an FPC.

The peripheral circuit area 234 includes a circuit for supplying a signal to the display area 235. Examples of the circuit included in the peripheral circuit region 234 include a scanning line driver circuit and a signal line driver circuit. The generic name of the circuits included in the peripheral circuit region 234 may be referred to as “peripheral drive circuit”.

The wiring 365 has a function of supplying a signal and power to the display region 235 and the peripheral circuit region 234. The signal and power are input to the wiring 365 from the outside through the FPC 372 or from the IC 373.

FIG. 1A illustrates an example in which the IC 373 is provided on the substrate 351 by a COG (Chip On Glass) method, a COF (Chip on Film) method, or the like. For example, an IC having a scan line driver circuit or a signal line driver circuit can be used as the IC 373. Note that the display device 100 and the display module may be configured without an IC. Further, the IC may be mounted on the FPC by a COF method or the like.

FIG. 1A shows an enlarged view of a part of the display area 235. In the display region 235, a plurality of pixels 230 are arranged in a matrix. The pixel 230 includes a light emitting element 170 and a liquid crystal element 180 as display elements. The pixel 230 includes a pixel circuit 236 for driving the display element.

FIG. 1B is a schematic perspective view of the pixel 230. The light emitting element 170 and the liquid crystal element 180 included in the pixel 230 overlap with each other through the pixel circuit 236. The pixel circuit 236 includes a first circuit for driving the light emitting element 170 and a second circuit for driving the liquid crystal element 180.

Light 237 emitted from the light emitting element 170 passes through the pixel circuit 236 and the liquid crystal element 180 and is emitted to the outside. In addition, light 238 incident from the outside passes through the liquid crystal element 180 and the pixel circuit 236 and is reflected by the electrode of the light emitting element 170, passes through the pixel circuit 236 and the liquid crystal element 180 again, and is emitted to the outside as reflected light. .

FIG. 2A illustrates a planar configuration example of the pixel circuit 236. A pixel circuit 236 illustrated in FIG. 2A includes elements such as a transistor 271, a capacitor 272, a transistor 281, a capacitor 282, and a transistor 283. In addition, the pixel circuit 236 includes part of the scan line 273, part of the signal line 274, part of the common potential line 275, part of the scan line 284, part of the signal line 285, and part of the power supply line 286. Including.

Note that a more specific configuration example of the pixel circuit 236 is described in Embodiment 4.

As described above, the light 237 passes through the pixel circuit 236 once. The light 238 passes through the pixel circuit 236 twice. Therefore, the pixel circuit 236 preferably includes a light-transmitting material.

At least one of the transistor 271, the capacitor 272, the transistor 281, the capacitor 282, and the transistor 283 is preferably formed using a light-transmitting conductive material. In addition, it is preferable that the electrodes connected to these in the pixel circuit 236 be formed using a light-transmitting material.

As the conductive material having a light-transmitting property, for example, a conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium is added may be used. In particular, a conductive material having an energy band gap of 2.5 eV or more is preferable because it has a high visible light transmittance.

On the other hand, a light-transmitting conductive material has a higher resistivity than a light-blocking conductive material such as copper or aluminum. Therefore, a bus line such as the scan line 273, the signal line 274, the scan line 284, the signal line 285, and the power supply line 286 is formed using a light-shielding conductive material (metal material) in order to prevent signal delay. It is preferable to form by using. Note that a light-transmitting conductive material may be used for the bus line depending on the size of the display region 235, the width of the bus line, the thickness of the bus line, and the like.

In general, the common potential line 275 is used to give a constant potential in the pixel circuit 236, and no charge is supplied through the common potential line 275. Therefore, the common potential line 275 can be formed using a light-transmitting conductive material with high resistivity. However, in the case where a method of changing the potential of the common potential line 275 is used as a method for driving the display element, it is preferable to use a light-shielding metal material having a low resistivity for the common potential line 275.

FIG. 2B is a plan view showing the transmission region 291 and the light shielding region 292 of the pixel circuit 236. The light 237 and the light 238 are emitted through the transmission region 291. Therefore, in the plan view, the extraction efficiency of the light 237 and the light 238 can be increased as the ratio of the transmission region 291 to the area occupied by the pixel 230 (also referred to as “aperture ratio”) is larger. That is, the power consumption of the display device 100 can be reduced. Further, the visibility of the display device 100 can be improved. Further, the display quality of the display device 100 can be improved.

In the display device 100 of one embodiment of the present invention, the aperture ratio can be 60% or more, further 80% or more by forming elements included in the pixel circuit 236 with a light-transmitting material. In addition, since the light-emitting element 170 and the liquid crystal element 180 can be provided to overlap each other, the total of the light-emitting area of the light-emitting element 170 and the reflective area of the liquid crystal element 180 can be greater than or equal to the area of the pixel 230. In other words, when the occupation area of the pixel 230 is 100%, the total area of the light emission area and the reflection area can be 100% or more. That is, it can be said that the aperture ratio can be 100% or more.

For example, when obtaining a certain light emission luminance (amount of light emission) per pixel, the light emission luminance per unit area can be reduced by increasing the light emission area of the light emitting element 170. Therefore, deterioration of the light emitting element 170 is reduced, and the reliability of the display device 100 can be improved.

[Cross-section configuration example]
3A and 3B, a part of the region including the FPC 372, a part of the region including the peripheral circuit region 234, and a part of the region including the display region 235 of the display device 100 illustrated in FIG. An example of a cross section is shown.

A display device 100 illustrated in FIG. 3 includes a transistor 201, a transistor 203, a transistor 205, a transistor 206, a capacitor 202, a liquid crystal element 180, a light-emitting element 170, an insulating layer 220, a coloring layer 131, and the like between a substrate 351 and a substrate 361. The coloring layer 134 and the like are included. The substrate 361 and the insulating layer 220 are bonded via an adhesive layer 141. The substrate 351 and the insulating layer 220 are bonded through an adhesive layer 142.

The substrate 361 is provided with a coloring layer 131, a light shielding layer 132, an insulating layer 121, an electrode 113 functioning as a common electrode of the liquid crystal element 180, an alignment film 133b, an insulating layer 117, and the like. The insulating layer 121 may function as a planarization layer. Since the surface of the electrode 113 can be substantially flattened by the insulating layer 121, the alignment state of the liquid crystal 112 can be made uniform. The insulating layer 117 functions as a spacer for maintaining the cell gap of the liquid crystal element 180. In the case where the insulating layer 117 transmits visible light, the insulating layer 117 may be overlapped with the display region of the liquid crystal element 180.

Note that a functional member 135 such as an optical member can be disposed on the outer surface of the substrate 361. Examples of the optical member include a polarizing plate, a retardation plate, a light diffusion layer (such as a diffusion film), an antireflection layer (also referred to as “Anti Reflection layer” or “AR layer”), an antiglare layer (“Anti Glare layer”) or And an “AG layer”) and a light collecting film. Examples of the functional member other than the optical member include an antistatic film that suppresses adhesion of dust, a water-repellent film that makes it difficult to adhere dirt, and a hard coat film that suppresses the occurrence of scratches associated with use. A combination of the above members may be used as the functional member 135. For example, you may use the circularly-polarizing plate which combined the linearly-polarizing plate and the phase difference plate.

The AR layer has a function of reducing regular reflection (specular reflection) of external light by utilizing light interference action. In the case where an AR layer is used as the functional member 135, the AR layer is formed using a material having a refractive index different from that of the substrate 361. The AR layer can be formed using a material such as zirconium oxide, magnesium fluoride, aluminum oxide, or silicon oxide, for example.

Further, an antiglare layer (also referred to as “Anti Glare layer” or “AG layer”) may be provided instead of the AR layer. The AG layer has a function of reducing regular reflection (specular reflection) by diffusing incident external light.

As a method for forming the AG layer, a method of providing fine irregularities on the surface, a method of mixing materials having different refractive indexes, a method of combining both, and the like are known. For example, an AG layer can be formed by mixing nanofibers such as cellulose fibers, inorganic beads such as silicon oxide, or resin beads with a light-transmitting resin.

An AG layer may be provided over the AR layer. By providing a stack of the AR layer and the AG layer, it is possible to further enhance the function of preventing reflection or reflection of external light. By using an AR layer and / or an AG layer, the external light reflectance of the surface of the display device may be less than 1%, preferably less than 0.3%.

A liquid crystal element 180 described in this embodiment is a reflective liquid crystal element in which the conductive layer 193 of the light-emitting element 170 is used as a reflective electrode. The liquid crystal element 180 has a stacked structure in which the electrode 311, the liquid crystal 112, and the electrode 113 are stacked. The electrode 311 and the electrode 113 transmit visible light. An alignment film 133 a is provided between the liquid crystal 112 and the electrode 311. An alignment film 133 b is provided between the liquid crystal 112 and the electrode 113.

By using the reflective electrode of the liquid crystal element 180 also as the conductive layer 193 of the light emitting element 170, the reflective electrode dedicated to the liquid crystal element 180 can be reduced. Thus, the manufacturing cost of the display device is reduced. In addition, productivity of the display device can be increased.

In this embodiment, a circularly polarizing plate is used as the functional member 135. Light incident from the substrate 361 side is polarized by the functional member 135 (circular polarizing plate), passes through the electrode 113, the liquid crystal 112, and the electrode 311, and is reflected by the conductive layer 193. Then, the light passes through the liquid crystal 112 and the electrode 113 again and reaches the functional member 135 (circularly polarizing plate). At this time, the orientation of the liquid crystal can be controlled by the voltage applied between the electrode 311 and the electrode 113, and the optical modulation of light can be controlled. That is, the intensity of light emitted through the functional member 135 (circularly polarizing plate) can be controlled. In addition, when the light other than the specific wavelength region is absorbed by the colored layer 131, the extracted light is, for example, red light.

In the connection portion 207, the electrode 311 is electrically connected to the conductive layer 222b included in the transistor 206 through the conductive layer 221b. The transistor 206 has a function of controlling driving of the liquid crystal element 180.

A connection portion 252 is provided in a part of the region where the adhesive layer 141 is provided. In the connection portion 252, a conductive layer obtained by processing the same conductive film as the electrode 311 and a part of the electrode 113 are electrically connected by a connection body 243. Therefore, a signal or a potential input from the FPC 372 can be supplied to the electrode 113 formed on the substrate 361 side through the connection portion 252.

As the connection body 243, for example, conductive particles can be used. As the conductive particles, those obtained by coating the surface of particles such as organic resin or silica with a metal material can be used. It is preferable to use nickel or gold as the metal material because the contact resistance can be reduced. In addition, it is preferable to use particles in which two or more kinds of metal materials are coated in layers, such as further coating nickel with gold. Further, it is preferable to use a material that is elastically deformed or plastically deformed as the connection body 243. At this time, the connection body 243, which is a conductive particle, may have a shape crushed in the vertical direction as shown in FIG. By doing so, the contact area between the connection body 243 and the conductive layer electrically connected to the connection body 243 can be increased, the contact resistance can be reduced, and the occurrence of problems such as connection failure can be suppressed. For example, the connection body 243 may be dispersed in the adhesive layer 141 before curing.

The connection body 243 is preferably disposed so as to be covered with the adhesive layer 141. For example, the connection body 243 may be dispersed in the adhesive layer 141 before curing.

The light emitting element 170 is a bottom emission type light emitting element. The light-emitting element 170 has a stacked structure in which a conductive layer 191, an EL layer 192, and a conductive layer 193 are stacked in this order from the insulating layer 220 side. The conductive layer 191 is connected to the conductive layer 222 b included in the transistor 205 through an opening provided in the insulating layer 214. The transistor 205 has a function of controlling driving of the light-emitting element 170. An insulating layer 216 covers an end portion of the conductive layer 191. The conductive layer 193 has a function of reflecting visible light, and the conductive layer 191 has a function of transmitting visible light. An insulating layer 194 is provided so as to cover the conductive layer 193. Light emitted from the light-emitting element 170 is emitted to the substrate 361 side through the insulating layer 220, the electrode 311, the colored layer 131, and the like.

The emission color of the light-emitting element 170 can be changed to white, red, green, blue, cyan, magenta, yellow, or the like depending on the material forming the EL layer 192. The reflected light controlled by the liquid crystal element 180 can be changed to white, red, green, blue, cyan, magenta, yellow, or the like depending on the material forming the colored layer 131. The light emitting element 170 and the liquid crystal element 180 can realize color display by changing the color of light controlled by a pixel.

Alternatively, the EL layer 192 that emits white light may be used for the light-emitting element 170 and the coloring layer 131 may be used for coloring.

In order to realize color display, the emission color of the light emitting element 170 and the color of the colored layer combined with the liquid crystal element 180 are not only combinations of red, green, and blue, but also combinations of yellow, cyan, and magenta. Good. What is necessary is just to set the color of the colored layer to combine suitably according to the objective or a use.

The transistor 201, the transistor 203, the transistor 205, the transistor 206, and the capacitor 202 are all formed over the surface of the insulating layer 220 on the substrate 351 side. In FIG. 3, top-gate transistors are illustrated as the transistor 201, the transistor 203, the transistor 205, and the transistor 206.

The transistor 203 is a transistor (also referred to as a switching transistor or a selection transistor) that controls pixel selection / non-selection. The transistor 205 is a transistor (also referred to as a drive transistor) that controls a current flowing through the light-emitting element 170.

Insulating layers such as an insulating layer 211, an insulating layer 212, an insulating layer 213, and an insulating layer 214 are provided on the substrate 351 side of the insulating layer 220. The insulating layer 212 and the insulating layer 213 are provided so as to cover the gate electrodes and the like of the transistor 201, the transistor 203, the transistor 205, and the transistor 206. The insulating layer 214 functions as a planarization layer. Note that the number of insulating layers covering the transistor is not limited, and may be a single layer or two or more layers.

It is preferable to use a material in which impurities such as water and hydrogen hardly diffuse for at least one of the insulating layers covering each transistor. Thereby, the insulating layer can function as a barrier film. With such a structure, impurities can be effectively prevented from diffusing from the outside with respect to the transistor, and a highly reliable display device can be realized.

The capacitor 202 includes a conductive layer 217 and a conductive layer 218 having regions overlapping with each other with the insulating layer 211 interposed therebetween. The conductive layer 217 can be formed using a material and a method similar to those of the conductive layer 225. The conductive layer 218 can be formed using a material and a method similar to those of the conductive layer 223.

The transistor 203, the transistor 205, and the transistor 206 are formed using a light-transmitting material. As described above, a light-transmitting conductive material has a higher resistivity than a light-blocking conductive material such as copper or aluminum. Therefore, a conductive layer used for the transistor 201 included in the peripheral circuit region 234, which is required to operate at high speed, is formed using a light-blocking conductive material (metal material) with low resistivity.

The transistor 203, the transistor 205, and the transistor 206 include a conductive layer 223 functioning as a gate, an insulating layer 224 functioning as a gate insulating layer, conductive layers 222a and 222b functioning as a source and a drain, and a semiconductor layer 231. . Here, the same hatching pattern is given to a plurality of layers obtained by processing the same conductive film. In addition, the transistor 205 includes a conductive layer 225 that can function as a gate.

Similarly, the transistor 201 includes a conductive layer functioning as a gate, an insulating layer functioning as a gate insulating layer, conductive layers and conductive layers functioning as a source and a drain, and a semiconductor layer. In addition, the transistor 205 includes a conductive layer 221a that can function as a gate. The conductive layer 221a and the conductive layer 221b can be obtained by processing the same conductive film.

A structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates is applied to the transistor 201 and the transistor 205. With such a structure, the threshold voltage of the transistor can be controlled. The transistor may be driven by connecting two gates and supplying the same signal thereto. Such a transistor can have higher field-effect mobility than other transistors, and can increase on-state current. As a result, a circuit that can be driven at high speed can be manufactured. Furthermore, the area occupied by the circuit portion can be reduced. By applying a transistor with a large on-state current, even if the number of wirings increases when the display device is enlarged or high-definition, signal delay in each wiring can be reduced, and display unevenness is suppressed. can do.

Alternatively, the threshold voltage of the transistor can be controlled by applying a potential for controlling the threshold voltage to one of the two gates and applying a potential for driving to the other of the two gates.

There is no limitation on the structure of the transistor included in the display device. The transistor included in the peripheral circuit region 234 and the transistor included in the display region 235 may have the same structure or different structures. The plurality of transistors included in the peripheral circuit region 234 may all have the same structure, or two or more kinds of structures may be used in combination. Similarly, the plurality of transistors included in the display region 235 may have the same structure, or two or more structures may be used in combination.

A conductive material containing an oxide may be used for the conductive layer functioning as a gate. By forming the conductive layer in an atmosphere containing oxygen, oxygen can be supplied to the gate insulating layer. The proportion of oxygen gas in the film forming gas is preferably in the range of 90% to 100%. Oxygen supplied to the gate insulating layer is supplied to the semiconductor layer by a later heat treatment, so that oxygen vacancies in the semiconductor layer can be reduced.

A connection portion 204 is provided in a region of the substrate 351 that does not overlap with the substrate 361. In the connection portion 204, the wiring 365 is electrically connected to the FPC 372 through the connection layer 242. The connection unit 204 has the same configuration as the connection unit 207. On the upper surface of the connection portion 204, a conductive layer obtained by processing the same conductive film as the electrode 311 is exposed. Accordingly, the connection unit 204 and the FPC 372 can be electrically connected via the connection layer 242.

As the liquid crystal element 180, for example, a liquid crystal element to which a vertical alignment (VA) mode is applied can be used. As the vertical alignment mode, an MVA (Multi-Domain Vertical Alignment) mode, a PVA (Patterned Vertical Alignment) mode, an ASV (Advanced Super View) mode, or the like can be used.

As the liquid crystal element 180, liquid crystal elements to which various modes are applied can be used. For example, in addition to the VA mode, a TN (Twisted Nematic) mode, an IPS (In-Plane-Switching) mode, a VA-IPS mode, an FFS (Fringe Field Switching) mode, an ASM (Axial Symmetrical Aligned MicroB) mode A liquid crystal element to which an Optically Compensated Birefringence (FLC) mode, an FLC (Ferroelectric Liquid Crystal) mode, an AFLC (Anti-Ferroelectric Liquid Crystal) mode, a guest-host mode, or the like can be used.

The liquid crystal element is an element that controls transmission or non-transmission of light by an optical modulation action of liquid crystal. The optical modulation action of the liquid crystal is controlled by an electric field applied to the liquid crystal (including a horizontal electric field, a vertical electric field, or an oblique electric field). As the liquid crystal used in the liquid crystal element, a thermotropic liquid crystal, a low-molecular liquid crystal, a polymer liquid crystal, a polymer dispersed liquid crystal (PDLC), a ferroelectric liquid crystal, an antiferroelectric liquid crystal, or the like can be used. . These liquid crystal materials exhibit a cholesteric phase, a smectic phase, a cubic phase, a chiral nematic phase, an isotropic phase, and the like depending on conditions.

As the liquid crystal material, either a positive type liquid crystal or a negative type liquid crystal may be used, and an optimal liquid crystal material may be used according to an applied mode or design.

In order to control the alignment of the liquid crystal, an alignment film can be provided. Note that in the case of employing a horizontal electric field mode, liquid crystal exhibiting a blue phase for which an alignment film is unnecessary may be used. The blue phase is one of the liquid crystal phases. When the temperature of the cholesteric liquid crystal is increased, the blue phase appears immediately before the transition from the cholesteric phase to the isotropic phase. Since the blue phase appears only in a narrow temperature range, a liquid crystal composition mixed with several percent by weight or more of a chiral agent is used for the liquid crystal in order to improve the temperature range. A liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent has a short response speed and is optically isotropic. In addition, a liquid crystal composition including a liquid crystal exhibiting a blue phase and a chiral agent does not require alignment treatment and has a small viewing angle dependency. Further, since it is not necessary to provide an alignment film, a rubbing process is not required, so that electrostatic breakdown caused by the rubbing process can be prevented, and defects or breakage of the liquid crystal display device during the manufacturing process can be reduced. .

Note that by using a liquid crystal material that operates in the guest-host mode for the liquid crystal element 180, functional members such as a light diffusion layer and a polarizing plate can be omitted. Thus, productivity of the display device can be increased. Further, by not providing a functional member such as a polarizing plate, the reflection luminance of the liquid crystal element 180 can be increased. Therefore, the visibility of the display device can be increased.

In addition, the reflective liquid crystal display device using a circularly polarizing plate is switched between the on state and the off state (switching between the bright state and the dark state) by aligning the major axis of the liquid crystal molecules in a direction substantially perpendicular to the substrate, It is done by aligning in a substantially horizontal direction. In general, a liquid crystal element that operates in a lateral electric field mode such as an IPS mode is difficult to use in a reflective liquid crystal display device because the major axis of liquid crystal molecules is aligned in a direction substantially horizontal to the substrate in both the on state and the off state.

A liquid crystal element that operates in the VA-IPS mode operates in a lateral electric field mode, and switches between an on state and an off state so that the major axis of the liquid crystal molecules is aligned in a direction substantially perpendicular to the substrate, or is substantially horizontal to the substrate. It is done by aligning the direction. Therefore, when a liquid crystal element that operates in a horizontal electric field mode is used for a reflective liquid crystal display device, a liquid crystal element that operates in a VA-IPS mode is preferably used.

A front light may be provided outside the functional member 135. As the front light, an edge light type front light is preferably used. It is preferable to use a front light including an LED (Light Emitting Diode) because power consumption can be reduced.

As the adhesive layer, various curable adhesives such as an ultraviolet curable photocurable adhesive, a reactive curable adhesive, a thermosetting adhesive, and an anaerobic adhesive can be used. Examples of these adhesives include epoxy resins, acrylic resins, silicone resins, phenol resins, polyimide resins, imide resins, PVC (polyvinyl chloride) resins, PVB (polyvinyl butyral) resins, EVA (ethylene vinyl acetate) resins, and the like. In particular, a material with low moisture permeability such as epoxy resin is preferable. Alternatively, a two-component mixed resin may be used. Further, an adhesive sheet or the like may be used.

As the connection layer 242, an anisotropic conductive film (ACF: Anisotropic Conductive Film), an anisotropic conductive paste (ACP: Anisotropic Conductive Paste), or the like can be used.

Examples of the light emitting element include a top emission type, a bottom emission type, and a dual emission type. A conductive film that transmits visible light is used for the electrode from which light is extracted. In addition, a conductive film that reflects visible light is preferably used for the electrode from which light is not extracted. The light-emitting element 170 can be referred to as a bottom emission type light-emitting element.

The EL layer 192 includes at least a light-emitting layer. The EL layer 192 is a layer other than the light-emitting layer and is a substance having a high hole-injecting property, a substance having a high hole-transporting property, a hole blocking material, a substance having a high electron-transporting property, a substance having a high electron-injecting property, or a bipolar property A layer containing a substance (a substance having a high electron transporting property and a high hole transporting property) or the like may be further included.

The emission color of the light-emitting element 170 can be changed to white, red, green, blue, cyan, magenta, yellow, or the like depending on the material forming the EL layer 192.

As a method for realizing color display, there are a method in which a light emitting element 170 having a white emission color and a colored layer are combined, and a method in which a light emitting element 170 having a different emission color is provided for each subpixel. The former method is more productive than the latter method. On the other hand, in the latter method, since it is necessary to create the EL layer 192 separately for each subpixel, productivity is inferior to the former method. However, in the latter method, it is possible to obtain an emission color with higher color purity than in the former method. In addition to the latter method, the color purity can be further increased by providing the light emitting element 170 with a microcavity structure.

Either a low molecular compound or a high molecular compound can be used for the EL layer 192, and an inorganic compound may be included. The layers constituting the EL layer 192 can be formed by a method such as a vapor deposition method (including a vacuum vapor deposition method), a transfer method, a printing method, an ink jet method, or a coating method.

The EL layer 192 may include an inorganic compound such as a quantum dot. For example, a quantum dot can be used for a light emitting layer to function as a light emitting material.

In the display device 100 of one embodiment of the present invention, a substrate is not provided between the light-emitting element 170 and the liquid crystal element 180. Therefore, the distance in the thickness direction between the light emitting element 170 and the liquid crystal element 180 can be less than 30 μm, preferably less than 10 μm, and more preferably less than 5 μm. Thereby, in the display using the light emitting element 170 and the liquid crystal element 180 simultaneously or alternately, the parallax generated between them can be reduced. Alternatively, the weight of the display device 100 can be reduced. Alternatively, the thickness of the display device 100 can be reduced. Alternatively, the display device 100 can be easily bent.

[substrate]
There is no particular limitation on the materials used for the substrate 351 and the substrate 361. Depending on the purpose, it may be determined in consideration of the presence or absence of translucency and heat resistance enough to withstand heat treatment. For example, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a ceramic substrate, a quartz substrate, a sapphire substrate, or the like can be used. Further, a semiconductor substrate, a flexible substrate (flexible substrate), a bonded film, a base film, or the like may be used.

Examples of the semiconductor substrate include a single semiconductor substrate made of silicon or germanium, or a compound semiconductor substrate made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, or gallium oxide. is there. The semiconductor substrate may be a single crystal semiconductor or a polycrystalline semiconductor.

Note that a flexible substrate (flexible substrate), a bonded film, a base film, or the like may be used for the substrate 351 and the substrate 361 in order to increase the flexibility of the display device 110.

Examples of materials such as a flexible substrate, a laminated film, and a base film include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyacrylonitrile resins, acrylic resins, polyimide resins, and 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, polychlorinated resin Vinylidene resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, cellulose nanofiber, and the like can be used.

By using the above material as the substrate, a lightweight display device can be provided. In addition, by using the above material as the substrate, a display device that is resistant to impact can be provided. In addition, by using the above material for the substrate, a display device which is not easily damaged can be provided.

As the flexible substrate used for the substrate 351 and the substrate 361, a lower linear expansion coefficient is preferable because deformation due to the environment is suppressed. The flexible substrate used for the substrate 351 and the substrate 361 is made of, for example, a material whose linear expansion coefficient is 1 × 10 ⁻³ / K or less, 5 × 10 ⁻⁵ / K or less, or 1 × 10 ⁻⁵ / K or less. Use it. In particular, since aramid has a low coefficient of linear expansion, it is suitable as a flexible substrate.

[Conductive layer]
In addition to the gate, source, and drain of a transistor, materials that can be used for conductive layers such as various wirings and electrodes that constitute a display device include aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, A metal such as tantalum or tungsten, or an alloy containing the same as a main component can be given. A film containing any of these materials can be used as a single layer or a stacked structure.

As the light-transmitting conductive material, conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium is added, or graphene can be used. Alternatively, an oxide conductor can be used as the light-transmitting conductive material. Alternatively, a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium, or an alloy material containing the metal material can be used. Alternatively, a nitride (eg, titanium nitride) of the metal material may be used. Note that in the case where a metal material or an alloy material (or a nitride thereof) is used, it may be thin enough to have a light-transmitting property. In addition, a stacked film of the above materials can be used as a conductive layer. For example, it is preferable to use a laminated film of an alloy of silver and magnesium and indium tin oxide because the conductivity can be increased. These can also be used for conductive layers such as various wirings and electrodes constituting the display device and conductive layers (conductive layers functioning as pixel electrodes and common electrodes) included in the display element.

Here, the oxide conductor will be described. In this specification and the like, the oxide conductor may be referred to as OC (Oxide Conductor). As an oxide conductor, for example, when an oxygen vacancy is formed in a metal oxide and hydrogen is added to the oxygen vacancy, a donor level is formed in the vicinity of the conduction band. As a result, the metal oxide becomes highly conductive and becomes a conductor. The conductive metal oxide can be referred to as an oxide conductor. In general, an oxide semiconductor has a large energy gap and thus has a light-transmitting property with respect to visible light. On the other hand, an oxide conductor is a metal oxide having a donor level near the conduction band. Therefore, the oxide conductor is less influenced by absorption due to the donor level, and has a light-transmitting property similar to that of an oxide semiconductor with respect to visible light.

[Insulation layer]
Examples of the insulating material that can be used for each insulating layer include resin materials such as acrylic and epoxy, and inorganic insulating materials such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminum oxide.

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

[Shading layer]
Examples of the material that can be used for the light-shielding layer include carbon black, titanium black, metal, metal oxide, and composite oxide containing a solid solution of a plurality of 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. Alternatively, a stacked film of a film containing a material for the colored layer can be used for the light shielding layer. For example, a stacked structure of a film including a material used for a colored layer that transmits light of a certain color and a film including a material used for a colored layer that transmits light of another color can be used. It is preferable to use a common material for the coloring layer and the light-shielding layer because the apparatus can be shared and the process can be simplified.

[Modification 1]

A cross section of a display device 100B, which is a modification of the display device 100, is shown in FIG. The display device 100B is different from the display device 100 in that the display device 100B does not include the coloring layer 131, the light shielding layer 132, and the insulating layer 121. Since other configurations are the same as those of the display device 100, detailed description thereof is omitted.

In the display device 100B, the liquid crystal element 180 exhibits white. Since the colored layer 131 is not provided, the display device 100 can perform display in black and white or gray scale using the liquid crystal element 180.

[Modification 2]
A cross section of a display device 100A, which is a modification of the display device 100, is shown in FIG. The display device 100 </ b> A includes a touch sensor 370 between the substrate 361 and the coloring 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.

The conductive layers 376a, 376b, and 377 are preferably formed using a light-transmitting conductive material. However, in general, a conductive material having a light-transmitting property has a higher resistivity than a metal material having no light-transmitting property. Therefore, the conductive layer 376a, the conductive layer 376b, and the conductive layer 377 may be formed using a metal material with low resistivity in order to increase the size and definition of the touch sensor.

In the case where the conductive layer 376a, the conductive layer 376b, and the conductive layer 377 are formed using a metal material, it is preferable to reduce external light reflection. In general, a metal material is a material having a high reflectivity. However, the reflectivity can be reduced by performing an oxidation treatment or the like to make a dark color.

Alternatively, the conductive layer 376a, the conductive layer 376b, and the conductive layer 377 may be a stack of a metal layer and a layer with low reflectance (also referred to as a “dark color layer”). Since the dark color layer has high resistivity, it is preferable to form a stack of a metal layer and a dark color layer. Examples of the dark color layer include a layer containing copper oxide and a layer containing copper chloride or tellurium chloride. In addition, the dark color layer is made of metal particles such as Ag particles, Ag fibers, and Cu particles, nanocarbon particles such as carbon nanotubes (CNT) or graphene, and conductive polymers such as PEDOT, polyaniline, or polypyrrole. May be formed.

Further, as the touch sensor 370, an optical touch sensor using a photoelectric conversion element may be used in addition to a resistive film type or capacitive type touch sensor. Examples of the electrostatic capacity method include a surface electrostatic capacity method and a projection electrostatic capacity method. As the projected capacitance method, there are a self-capacitance method, a mutual capacitance method, etc. mainly due to a difference in driving method. The mutual capacitance method is preferable because simultaneous multipoint detection is possible.

Since other configurations are the same as those of the display device 100, detailed description thereof is omitted.

Alternatively, the touch sensor may be provided so as to overlap the substrate 361 of the display device 100 without providing the touch sensor 370 between the substrate 361 and the coloring layer 131. For example, a sheet-like touch sensor 176 may be provided over the display area 235 (see FIG. 6).

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

Note that 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 may be referred to as “front gate electrode”. Similarly, the gate may be referred to as a “front gate”.

By providing the gate electrode and the 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 structure of a transistor that electrically surrounds a semiconductor layer in which a channel is formed by an electric field generated from the gate electrode and the back gate electrode can be referred to as a surround channel (S-channel) structure.

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 a ground potential or an arbitrary 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.

By providing the gate electrode and the back gate electrode, and further by setting both to the same potential, the carrier flow region in the semiconductor layer becomes larger in the film thickness direction, so that the amount of carrier movement increases. As a result, the on-current of the transistor increases and the field effect mobility increases.

Therefore, the transistor can be a transistor having a large on-state current with respect to the occupied area. That is, the area occupied by the transistor can be reduced with respect to the required on-state current. Therefore, a highly integrated semiconductor device can be realized.

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

Since each of the gate electrode and the back gate electrode has a function of shielding an electric field from the outside, charges such as charged particles generated above and below the transistor do not affect the channel formation region of the semiconductor layer. As a result, deterioration of a stress test (for example, NGBT (Negative Gate Bias-Temperature) stress test (also referred to as “NBT” or “NBTS”) in which a negative charge is applied to the gate is suppressed. The back gate electrode can block the electric field generated from the drain electrode so as not to act on the semiconductor layer, and thus can suppress fluctuations in the rising voltage of the on-current due to fluctuations in the drain voltage. This effect is remarkable when a potential is supplied to the gate electrode and the back gate electrode.

In addition, a transistor having a back gate electrode has a variation in threshold voltage before and after a PGBT (Positive Gate Bias-Temperature) stress test (also referred to as “PBT” or “PBTS”) in which a positive charge is applied to the gate. Smaller than a transistor without a back gate electrode.

Note that a BT stress test such as NGBT and PGBT is a kind of accelerated test, and a transistor characteristic change (aging) caused by long-term use can be evaluated in a short time. In particular, the amount of change in the threshold voltage of the transistor before and after the BT stress test is an important index for examining reliability. Before and after the BT stress test, the smaller the variation amount of the threshold voltage, the higher the reliability of the transistor.

In addition, since the gate electrode and the back gate electrode are provided and both have the same potential, the amount of fluctuation in the threshold voltage is reduced. For this reason, variation in electrical characteristics among a plurality of transistors is also reduced at the same time.

In addition, when light enters from the back gate electrode side, the back gate electrode is formed using a light-shielding conductive film, whereby light can be prevented from entering the semiconductor layer from the back gate electrode side. Therefore, light deterioration of the semiconductor layer can be prevented, and deterioration of electrical characteristics such as shift of the threshold voltage of the transistor can be prevented.

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

For example, silicon, germanium, or the like can be used as a semiconductor material used for a semiconductor layer of the transistor. Alternatively, a compound semiconductor such as silicon carbide, gallium arsenide, metal oxide, or nitride semiconductor, or an organic semiconductor can be used.

For example, polycrystalline silicon (polysilicon), amorphous silicon (amorphous silicon), or the like can be used as a semiconductor material used for the transistor. As a semiconductor material used for the transistor, an oxide semiconductor which is a kind of metal oxide can be used. Typically, an oxide semiconductor containing indium can be used.

In particular, it is preferable to use a semiconductor material with a wider band gap and lower carrier density than silicon because current flowing between the source and the drain in the off state of the transistor can be reduced.

The semiconductor layer is represented by an In-M-Zn-based oxide containing at least indium, zinc, and M (metal such as aluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum, cerium, tin, neodymium, or hafnium). It is preferable to include a material. In addition, in order to reduce variation in electrical characteristics of the transistor including the oxide semiconductor, a stabilizer is preferably included together with the transistor.

Examples of the stabilizer include the metals described in M above, and examples include gallium, tin, hafnium, aluminum, and zirconium. Other stabilizers include lanthanoids such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

As an oxide semiconductor included in the semiconductor layer, for example, an In—Ga—Zn-based oxide, an In—Al—Zn-based oxide, an In—Sn—Zn-based oxide, an In—Hf—Zn-based oxide, an In— La-Zn oxide, In-Ce-Zn oxide, In-Pr-Zn oxide, In-Nd-Zn oxide, In-Sm-Zn oxide, In-Eu-Zn oxide In-Gd-Zn-based oxide, In-Tb-Zn-based oxide, In-Dy-Zn-based oxide, In-Ho-Zn-based oxide, In-Er-Zn-based oxide, In-Tm -Zn oxide, In-Yb-Zn oxide, In-Lu-Zn oxide, In-Sn-Ga-Zn oxide, In-Hf-Ga-Zn oxide, In-Al- Ga-Zn-based oxide, In-Sn-Al-Zn-based oxide, In-Sn-Hf-Zn-based Product, can be used In-Hf-Al-Zn-based oxide.

Note that here, an In—Ga—Zn-based oxide means an oxide containing In, Ga, and Zn as its main components, and there is no limitation on the ratio of In, Ga, and Zn. Moreover, metal elements other than In, Ga, and Zn may be contained.

An oxide semiconductor which is a kind of metal oxide is classified into a single crystal oxide semiconductor and a non-single-crystal oxide semiconductor. As the non-single-crystal oxide semiconductor, a CAAC-OS (c-axis-aligned crystal oxide semiconductor), a polycrystalline oxide semiconductor, an nc-OS (nanocrystalline oxide semiconductor), a pseudo-amorphous oxide semiconductor (a-like oxide semiconductor) : Amorphous-like oxide semiconductor) and amorphous oxide semiconductor.

Alternatively, a CAC-OS (Cloud-Aligned Composite Oxide Semiconductor) may be used for the semiconductor layer of the transistor disclosed in one embodiment of the present invention.

Note that the above-described non-single-crystal oxide semiconductor or CAC-OS is preferably used for the semiconductor layer of the transistor disclosed in one embodiment of the present invention. As the non-single-crystal oxide semiconductor, an nc-OS or a CAAC-OS is preferably used.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 2)
An example of a method for manufacturing the display device 100 will be described with reference to drawings. In particular, a manufacturing method will be described focusing on the transistors included in the peripheral circuit region 234 and the transistors included in the display region 235.

Note that an insulating layer, a semiconductor layer, a conductive layer, and the like included in the display device are formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulse laser deposition (PLD) method, It can be formed using an atomic layer deposition (ALD) method or the like. The CVD method may be a plasma enhanced chemical vapor deposition (PECVD) method or a thermal CVD method. As an example of the thermal CVD method, a metal organic chemical vapor deposition (MOCVD) method may be used.

Insulating layers, semiconductor layers, conductive layers, etc. constituting the display device are spin coating, dip, spray coating, ink jet, dispensing, screen printing, offset printing, slit coating, roll coating, curtain coating, knife coating, etc. Can be formed.

When a layer (thin film) included in the display device is processed, the layer can be processed using a photolithography method or the like. Alternatively, the island-shaped layer may be formed by a film formation method using a shielding mask. Alternatively, the layer may be processed by a nanoimprint method, a sand blast method, a lift-off method, or the like. As a photolithography method, a resist mask is formed over a layer (thin film) to be processed, a part 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 of forming a layer having photosensitivity and then performing exposure and development to process the layer into a desired shape.

When light is used in the photolithography method, light used for exposure can be, for example, i-line (wavelength 365 nm), g-line (wavelength 436 nm), h-line (wavelength 405 nm), or light obtained by mixing these. In addition, ultraviolet light, KrF laser light, ArF laser light, or the like can be used. Further, exposure may be performed by an immersion exposure technique. Further, extreme ultraviolet light (EUV: Extreme Ultra-violet) or X-rays may be used as light used for exposure. Further, an electron beam can be used instead of the light used for exposure. It is preferable to use extreme ultraviolet light, X-rays, or an electron beam because extremely fine processing is possible. Note that a photomask is not necessary when exposure is performed by scanning a beam such as an electron beam.

For removal (etching) of the layer (thin film), a dry etching method, a wet etching method, a sand blasting method, or the like can be used. Moreover, you may use combining these etching methods.

<Example of production method>
The display device 100 described in this embodiment is manufactured by combining a counter substrate 171 (see FIG. 7D) and a transistor substrate 181 (see FIG. 15B).

[Counter substrate 171]
First, a method for manufacturing the counter substrate 171 is described.

[Step A1]
A colored layer 131 and a light-blocking layer 132 are formed over the substrate 361 (see FIG. 7A). The substrate 361 preferably has a light-transmitting property.

In this embodiment, a glass substrate is used as the support substrate 331. The substrate 361 preferably has mechanical strength that can withstand the manufacturing process of the display device 100. In other words, it is preferable that the substrate 361 has rigidity to an extent that the substrate 361 can be easily transported and has heat resistance with respect to the temperature required for the manufacturing process.

The colored layer 131 can be processed into an island shape by a photolithography method or the like by being formed using a photosensitive material. The coloring layer 131 and the light shielding layer 132 may be provided as necessary. Therefore, there may be a case where at least one of the colored layer 131 and the light shielding layer 132 is not provided. In the display device 100, a light shielding layer 132 is provided so as to overlap with the peripheral circuit region 234 and the like.

[Step A2]
Next, the insulating layer 121 is formed over the coloring layer 131 and the light-blocking layer 132 (see FIG. 7B).

The insulating layer 121 preferably functions as a planarization layer. For the insulating layer 121, a resin such as acrylic or epoxy can be preferably used. An inorganic insulating layer may be used as the insulating layer 121.

[Step A3]
Next, the electrode 113 is formed (see FIG. 7C). The electrode 113 can be formed by forming a conductive film, then forming a resist mask, etching the conductive film, and then removing the resist mask. The electrode 113 is formed using a conductive material that transmits visible light.

[Step A8]
Next, the insulating layer 117 is formed over the electrode 113 (see FIG. 7C). The insulating layer 117 is preferably formed using an organic resin material.

[Step A9]
Next, an alignment film 133b is formed over the electrode 113 and the insulating layer 117 (see FIG. 7D). The alignment film 133b can be formed by performing alignment treatment (rubbing treatment, photo-alignment treatment, or the like) after forming a thin film of resin or the like.

In this manner, the counter substrate 171 can be manufactured.

[Transistor substrate 181]
Next, a method for manufacturing the transistor substrate 181 will be described.

[Step B1]
A separation layer 335 is formed over the supporting substrate 334, and a layer 336 is formed over the separation layer 335 (see FIG. 8A). As the support substrate 334, a material similar to that of the substrate 351 and the substrate 361 can be used. The support substrate 334 preferably has a function of transmitting ultraviolet light.

In this embodiment, a glass substrate is used as the supporting substrate 334. The support substrate 334 preferably has mechanical strength that can withstand the manufacturing process of the display device 100. In other words, it is preferable that the support substrate 334 has rigidity to an extent that the support substrate 334 can be easily transported and has heat resistance with respect to the temperature required for the manufacturing process. The thickness of the support substrate 331 is preferably 0.5 mm or more and 5 mm or less, and more preferably 0.7 mm or more and 5 mm or less.

The release layer 335 preferably has a function of absorbing light to be irradiated later. As the separation layer 335, a metal layer, a metal oxide layer, or the like can be used. For example, as the separation layer 335, titanium oxide (TiO _x ), molybdenum oxide, aluminum oxide, tungsten oxide, indium tin oxide containing silicon (ITSO), indium zinc oxide, In—Ga—Zn oxide, or the like is used. Can do.

There is no particular limitation on the method for forming the release layer 335. For example, it can be formed using a sputtering method, a plasma CVD method, a vapor deposition method, a sol-gel method, an electrophoresis method, a spray method, or the like.

In the case where a metal oxide is used for the separation layer 335, the separation layer 335 can be formed by introducing oxygen into the metal layer after the metal layer is formed. At this time, only the surface of the metal layer or the entire metal layer is oxidized. In the former case, a laminated structure of a metal layer and a metal oxide layer is formed by introducing oxygen into the metal layer.

Alternatively, the metal layer may be oxidized by heating the metal layer in an atmosphere containing oxygen. In this case, it is preferable to heat the metal layer while flowing a gas containing oxygen. The temperature for heating the metal layer is preferably 100 ° C. or higher and 500 ° C. or lower, more preferably 100 ° C. or higher and 450 ° C. or lower, more preferably 100 ° C. or higher and 400 ° C. or lower, and further preferably 100 ° C. or higher and 350 ° C. or lower.

The temperature for heating the metal layer is preferably equal to or lower than the maximum temperature in the manufacture of the transistor. Thereby, it can prevent that the maximum temperature in manufacture of a display apparatus becomes high. By setting the temperature to be equal to or lower than the maximum temperature in manufacturing a transistor, it is possible to divert a manufacturing apparatus or the like in a transistor manufacturing process, and thus it is possible to suppress additional equipment investment. Therefore, a display device with reduced production costs can be obtained. For example, when the manufacturing temperature of the transistor is up to 350 ° C., the temperature of the heat treatment is preferably 350 ° C. or lower.

A release layer 335 may be formed by forming a metal layer and performing radical treatment on the surface of the metal layer. In the radical treatment, it is preferable to expose the surface of the metal layer to an atmosphere containing at least one of oxygen radicals and hydroxy radicals. For example, plasma treatment is preferably performed in an atmosphere containing one or both of oxygen and water vapor (H ₂ O).

The radical treatment can be performed using a plasma generator or an ozone generator. For example, oxygen plasma treatment, hydrogen plasma treatment, water plasma treatment, ozone treatment, or the like can be performed. The oxygen plasma treatment can be performed by generating plasma in an atmosphere containing oxygen. The hydrogen plasma treatment can be performed by generating plasma in an atmosphere containing hydrogen. The water plasma treatment can be performed by generating plasma in an atmosphere containing water vapor (H ₂ O). In particular, water plasma treatment is preferable because a large amount of moisture can be contained in the surface or inside of the release layer 335.

Alternatively, plasma treatment may be performed in an atmosphere containing two or more of oxygen, hydrogen, water (water vapor), and an inert gas (typically argon). Examples of the plasma treatment include plasma treatment in an atmosphere containing oxygen and hydrogen, plasma treatment in an atmosphere containing oxygen and water, plasma treatment in an atmosphere containing water and argon, and oxygen and argon. Or a plasma treatment in an atmosphere containing oxygen, water, and argon. Using argon gas as one of the plasma treatment gases is preferable because the plasma treatment can be performed while damaging the peeling layer 335.

Two or more plasma treatments may be performed continuously without exposure to the atmosphere. For example, the water plasma treatment may be performed after the argon plasma treatment.

Accordingly, hydrogen, oxygen, a hydrogen radical (H ^* ), an oxygen radical (O ^* ), a hydroxy radical (OH ^* ), or the like can be included in the surface or inside of the peeling layer 335. Moreover, it is heated by heat treatment or light irradiation, the H 2 _O.

The thickness of the release layer 335 is preferably 1 nm to 200 nm, more preferably 5 nm to 100 nm, and more preferably 5 nm to 50 nm. Note that in the case where the release layer 335 is formed by oxidizing the metal layer, the thickness of the release layer 335 finally formed may be larger than the thickness of the formed metal layer.

By supplying a liquid containing water to the interface between the release layer 335 and the layer 336 before or during the separation between the release layer 335 and the layer 336, which is performed later, the force required for the separation can be reduced. As the contact angle between the release layer 335 and the liquid is smaller, the force required for separation can be reduced. Specifically, the contact angle between the release layer 335 and the liquid containing water is preferably greater than 0 ° and 60 ° or less, and more preferably greater than 0 ° and 50 ° or less. In addition, when the wettability with respect to the liquid containing water is very high (for example, when a contact angle is about 20 degrees or less), acquisition of the exact value of a contact angle may be difficult. Since the peeling layer 335 is more suitable as the wettability with respect to the liquid containing water is higher, the wettability with respect to the liquid containing water may be higher as the accurate value of the contact angle cannot be obtained.

For the peeling layer 335, titanium oxide, tungsten oxide, or the like is preferable. When titanium oxide is used, cost can be reduced as compared with tungsten oxide, which is preferable.

The release layer 335 may have a photocatalytic function. By irradiating light to the metal oxide layer having a photocatalytic function, a photocatalytic reaction can be caused. Thereby, the bond strength between the metal oxide layer and the resin layer may be weakened and may be easily separated. The release layer 335 can be appropriately irradiated with light having a wavelength that activates the release layer 335. For example, the release layer 335 is irradiated with ultraviolet light. For example, after the release layer 335 is formed, the release layer 335 may be directly irradiated with ultraviolet light without passing through another layer. For irradiation with ultraviolet light, an ultraviolet light lamp can be suitably used. Examples of the ultraviolet lamp include a mercury lamp, a mercury xenon lamp, and a metal halide lamp. Alternatively, the peeling layer 335 may be activated by a laser irradiation process performed before separation.

As the separation layer 335, titanium oxide to which a metal element or nitrogen is added may be used. When the separation layer 335 is formed using titanium oxide to which these elements are added, the separation layer 335 and the layer 336 can be separated by visible light instead of ultraviolet light.

The layer 336 can be formed using various resin materials (including a resin precursor). The layer 336 is preferably formed using a thermosetting material. The layer 336 may be formed using a photosensitive material or a non-photosensitive material (also referred to as a non-photosensitive material).

When a photosensitive material is used, a part of the layer 336 can be removed and a layer 336 having a desired shape can be formed by a photolithography method using light.

The layer 336 is preferably formed using a material containing a polyimide resin or a polyimide resin precursor. The layer 336 can be formed using, for example, a material containing a polyimide resin and a solvent, or a material containing a polyamic acid and a solvent. Since polyimide is a material that is suitably used for a planarizing film or the like of a display device, the film forming device and the material can be shared. Therefore, no new device or material is required to realize the structure of one embodiment of the present invention.

In addition, examples of the resin material that can be used for forming the layer 336 include acrylic resins, epoxy resins, polyamide resins, polyimide amide resins, siloxane resins, benzocyclobutene resins, phenol resins, and precursors of these resins. Is mentioned.

The layer 336 is preferably formed using a slit coater or a spin coater. By using the spin coating method, a thin film can be uniformly formed on a large substrate.

The layer 336 is preferably formed using a solution having a viscosity of 5 cP or more and less than 500 cP, preferably 5 cP or more and less than 100 cP, more preferably 10 cP or more and 50 cP or less. The lower the viscosity of the solution, the easier the application. In addition, the lower the viscosity of the solution, the more air bubbles can be prevented and the better quality layer can be formed.

Alternatively, the layer 336 may be formed using an inorganic material that releases hydrogen by heating. For example, the layer 336 may be formed using amorphous silicon containing hydrogen.

Next, heat treatment is performed on the layer 336 to cure the layer 336. The heat treatment can be performed, for example, while flowing a gas containing one or more of oxygen, nitrogen, and a rare gas (such as argon) inside the chamber of the heating device. Alternatively, the heat treatment can be performed using a chamber of a heating device, a hot plate, or the like in an air atmosphere.

When heat treatment is performed in an air atmosphere or a gas containing oxygen, the layer 336 may be colored by oxidation, and the visible light permeability may be reduced. Therefore, it is preferable to perform heating while flowing nitrogen gas. Thereby, the visible light transmittance of the layer 336 can be increased.

The temperature of the heat treatment is preferably equal to or lower than the maximum temperature in manufacturing the transistor. For example, when the manufacturing temperature of the transistor is up to 350 ° C., the temperature of the heat treatment is preferably 350 ° C. or lower.

The heat treatment time is preferably, for example, 5 minutes to 24 hours, more preferably 30 minutes to 12 hours, and further preferably 1 hour to 6 hours. Note that the heat treatment time is not limited thereto. For example, when the heat treatment is performed using an RTA (Rapid Thermal Annealing) method, it may be less than 5 minutes.

As the heating device, various devices such as an electric furnace and a device for heating an object to be processed by heat conduction or heat radiation from a heating element such as a resistance heating element can be used. For example, an RTA apparatus such as a GRTA (Gas Rapid Thermal Anneal) apparatus or an LRTA (Lamp Rapid Thermal Anneal) apparatus can be used. The LRTA apparatus is an apparatus that heats an object to be processed by radiation of light (electromagnetic waves) emitted from a lamp such as a halogen lamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp, a high pressure sodium lamp, or a high pressure mercury lamp. The GRTA apparatus is an apparatus that performs heat treatment using a high-temperature gas. Since the processing time can be shortened by using an RTA apparatus, it is preferable for mass production. Further, the heat treatment may be performed using an in-line heating apparatus.

Prior to heat treatment, heat treatment (also referred to as pre-bake treatment) for removing the solvent contained in the layer 336 may be performed. The pre-baking temperature can be appropriately determined according to the material used. For example, it can be performed at 50 ° C. or higher and 180 ° C. or lower, 80 ° C. or higher and 150 ° C. or lower, or 90 ° C. or higher and 120 ° C. or lower. Alternatively, the heat treatment may also serve as a prebake treatment, and the solvent contained in the layer 336 may be removed by the heat treatment.

The thickness of the layer 336 is preferably 0.01 μm or more and less than 10 μm, more preferably 0.1 μm or more and 5 μm or less, and further preferably 0.5 μm or more and 3 μm or less. By forming the layer 336 thin, a display device can be manufactured at low cost.

The thermal expansion coefficient of the layer 336 is preferably 0.1 ppm / ° C. or more and 50 ppm / ° C. or less, more preferably 0.1 ppm / ° C. or more and 20 ppm / ° C. or less, and 0.1 ppm / ° C. or more and 10 ppm / ° C. or less. More preferably, it is as follows. As the thermal expansion coefficient of the layer 336 is lower, it is possible to suppress the generation of cracks in the layer included in the transistor or the like, or the damage of the transistor or the like due to heating.

The separation of the separation layer 335 and the layer 336 includes a physical separation method other than the above-described separation method by light irradiation.

In the case where the separation layer 335 and the layer 336 are physically separated, for example, a layer containing a refractory metal material such as tungsten and a layer containing an oxide of the metal material are stacked and used as the separation layer 335. A metal layer containing a refractory metal material may be formed, and the surface of the metal layer may be oxidized by oxygen plasma treatment or the like.

In the case where the separation layer 335 and the layer 336 are physically separated, for example, an inorganic insulating material containing oxygen such as silicon oxide, silicon oxynitride, or silicon nitride oxide is used as the layer 336.

For example, the peeling layer 335 and the layer 336 can be separated by applying a pulling force in the vertical direction to the supporting substrate 331 on which the peeling layer 335 is formed.

In the physical separation method as well as the separation method by light irradiation, at the time of separation, a liquid containing water such as water or an aqueous solution is added to the separation interface, and separation is performed so that the liquid penetrates the separation interface. Thus, separation can be easily performed. In addition, static electricity generated at the time of separation can be prevented from adversely affecting a functional element such as a transistor (a semiconductor element is destroyed by static electricity).

Examples of the liquid to be supplied include water (preferably pure water), a neutral, alkaline, or acidic aqueous solution, and an aqueous solution in which a salt is dissolved. Moreover, ethanol, acetone, etc. are mentioned. Various organic solvents may be used.

Note that the separation layer 335 is not necessarily formed when a separation method by light irradiation is used. However, by forming the release layer 335, absorption of light to be irradiated can be increased. In addition, by forming the separation layer 335, the yield of the separation process can be increased. Thus, productivity of the display device can be increased.

Further, a water-soluble resin material may be used for the layer 336. By using a water-soluble resin material for the layer 336, for example, the separation process of the support substrate 334 can be combined with the cleaning process. Therefore, the light irradiation process, the physical peeling process, and the like can be reduced. In addition, a subsequent step of removing the layer 336 can be reduced.

[Step B2]
Next, the insulating layer 337 is formed over the layer 336, and the electrode 311 is formed over the insulating layer 337 (see FIG. 8B). The electrode 311 can be formed by forming a conductive film, forming a resist mask, etching the conductive film, and then removing the resist mask. The electrode 311 is formed using a conductive material that transmits visible light. In this embodiment mode, the electrode 311 is not provided over the peripheral circuit region 234, but the electrode 311 may be provided over the peripheral circuit region 234. Note that the insulating layer 337 may be provided as necessary. Therefore, the insulating layer 337 may not be provided.

[Step B3]
Next, the insulating layer 220 is formed, and the conductive layer 225 is provided over the insulating layer 220 in the display region 235 (see FIG. 8C). The conductive layer 225 can be formed by forming a conductive film, then forming a resist mask, etching the conductive film, and then removing the resist mask. The conductive layer 225 is formed using a conductive material that transmits visible light.

The insulating layer 220 can be used as a barrier layer which prevents impurities from diffusing from the support substrate 334 side to a transistor or a display element which will be formed later. For example, in the case where an organic resin material is used for the layer 336, the insulating layer 220 preferably prevents diffusion of moisture or the like contained in the layer 336 to the transistor or the display element when the layer 336 is heated. Therefore, the insulating layer 220 is preferably formed using a material with a high barrier property against impurities.

[Step B4]
Next, an opening reaching the electrode 311 is provided in the insulating layer 220 (see FIG. 8D).

[Step B5]
Next, a conductive layer 221a is provided over the insulating layer 220 in the peripheral circuit region 234, and a conductive layer 221b is provided over the insulating layer 220 in the display region 235 (see FIG. 8D). The conductive layer 221a and the conductive layer 221b can be obtained by processing the same conductive film.

The conductive layers 221a and 221b are formed using a light-blocking conductive material (metal material) with low resistivity.

[Step B6]
Next, an insulating layer 211 is provided (see FIG. 9A). As the insulating layer 211, 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. 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, a neodymium oxide film, or the like may be used. Two or more of the above insulating films may be stacked.

The inorganic insulating film is denser and has a higher barrier property as the deposition temperature is higher, and thus it is preferable to form the inorganic insulating film at a high temperature. The substrate temperature during the formation of the inorganic insulating film is preferably room temperature (25 ° C.) or higher and 350 ° C. or lower, more preferably 100 ° C. or higher and 300 ° C. or lower.

In the case where an oxide semiconductor is used for the semiconductor layer 231, in particular, the insulating layer having a region in contact with the semiconductor layer 231 is also referred to as an insulating layer from which oxygen is released by heating (hereinafter referred to as an “insulating layer containing excess oxygen”). .). Therefore, the insulating layer 211 is preferably an insulating layer containing excess oxygen.

Note that in this specification and the like, oxygen released from the layer by heating is referred to as “excess oxygen”. The insulating layer containing excess oxygen has a surface temperature of the insulating layer of 100 ° C. or higher and 700 ° C. or lower, preferably 100 ° C. or higher and 500 ° C. or lower. May be 1.0 × 10 ¹⁸ atoms / cm ³ or more, 1.0 × 10 ¹⁹ atoms / cm ³ or more, or 1.0 × 10 ²⁰ atoms / cm ³ or more.

[Step B7]
Next, the semiconductor layer 231 is formed (see FIG. 9A). In this embodiment, an oxide semiconductor layer is formed as the semiconductor layer 231. The oxide semiconductor layer can be formed by forming an oxide semiconductor film, forming a resist mask, etching the oxide semiconductor film, and then removing the resist mask.

The substrate temperature at the time of forming 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.

The oxide semiconductor film can be formed using either an inert gas or an oxygen gas. Note that there is no particular limitation on the oxygen flow rate ratio (oxygen partial pressure) in forming the oxide semiconductor film. However, in the case of obtaining a transistor with high field-effect mobility, the flow rate ratio of oxygen (oxygen partial pressure) during formation of the oxide semiconductor film is preferably 0% or more and 30% or less, and is preferably 5% or more and 30% or less. Is more preferably 7% or more and 15% or less.

The oxide semiconductor film preferably contains at least indium or zinc. In particular, it is preferable to contain indium and zinc.

The oxide semiconductor preferably has an energy gap of 2 eV or more, and more preferably 2.5 eV or more. More preferably, it is 3 eV or more. In this manner, off-state current of a transistor can be reduced by using an oxide semiconductor with a wide energy gap.

In particular, a semiconductor material with an energy gap of 2.5 eV or more is preferable because it has a high visible light transmittance.

The oxide semiconductor film can be formed by a sputtering method. In addition, for example, a PLD method, a PECVD method, a thermal CVD method, an ALD method, a vacuum deposition method, or the like may be used.

[Step B8]
Next, the insulating layer 224 is formed (see FIG. 9B). The insulating layer 224 can be provided using a material and a method similar to those of the insulating layer 211.

[Step B9]
Next, in the display region 235, the conductive layer 223 having a region overlapping with the semiconductor layer 231 is provided over the insulating layer 224. The conductive layer 223 can be formed by forming a conductive film, forming a resist mask, etching the conductive film, and then removing the resist mask. The conductive layer 223 is formed using a light-transmitting conductive material. The conductive layer 223 can be provided using a material and a method similar to those of the conductive layer 225.

[Step B10]
Next, in the peripheral circuit region 234, a conductive layer 226 having a region overlapping with the semiconductor layer 231 is provided over the insulating layer 224 (see FIG. 9C). The conductive layer 226 can be formed by forming a conductive film, then forming a resist mask, etching the conductive film, and then removing the resist mask. The conductive layer 226 is formed using a light-blocking conductive material. The conductive layer 226 can be provided using a material and a method similar to those of the conductive layer 221a.

[Step B11]
Next, part of the insulating layer 224 is selectively removed using the conductive layers 223 and 226 as masks (see FIG. 9D). By performing Step B11, an island-shaped insulating layer 224 is formed. Further, by performing the process B11, a region of the semiconductor layer 231 that does not overlap with the conductive layer 226 is exposed in the peripheral circuit region 234. In the display region 235, a region of the semiconductor layer 231 that does not overlap with the conductive layer 223 is exposed.

[Step B12]
Next, an impurity 227 for increasing conductivity is added to the exposed region of the semiconductor layer 231 in Step B11 (see FIG. 10A). In this embodiment, since an oxide semiconductor is used for the semiconductor layer 231, an impurity for forming an oxygen vacancy and increasing conductivity in the semiconductor layer 231 (oxide semiconductor layer) is added. Examples of impurities that form oxygen vacancies in the oxide semiconductor layer include phosphorus, arsenic, antimony, boron, aluminum, silicon, nitrogen, helium, neon, argon, krypton, xenon, indium, fluorine, chlorine, titanium, zinc, And one or more selected from carbon and carbon can be used. As a method for adding the impurity, a plasma treatment method, an ion implantation method, an ion doping method, a plasma immersion ion implantation method, or the like can be used.

When the above element is added to the oxide semiconductor layer as the impurity element, the bond between the metal element and oxygen in the oxide semiconductor layer is cut, so that an oxygen vacancy is formed. The conductivity of the oxide semiconductor layer can be increased by the interaction between oxygen vacancies contained in the oxide semiconductor layer and hydrogen that remains in the oxide semiconductor layer or is added later.

When hydrogen enters an oxide semiconductor in which oxygen vacancies are formed by addition of an impurity element, hydrogen enters the oxygen vacancy site and a donor level is formed in the vicinity of the conduction band. As a result, the conductivity of the oxide semiconductor can be increased. In other words, the resistivity of the oxide semiconductor can be reduced.

A region whose conductivity is increased by adding the impurity 227 of the semiconductor layer 231 can function as a source region or a drain region of the transistor. In this embodiment, the impurity 227 is added using the conductive layer 223 and the conductive layer 226 as masks. That is, the source region or the drain region of the transistor is formed by self-alignment (self-alignment).

[Step B13]
Next, the insulating layer 212 is provided, and the insulating layer 213 is provided over the insulating layer 212 (see FIG. 10B). The insulating layer 212 can be provided using a material and a method similar to those of the insulating layer 211.

Note that as the insulating layer 212, an insulating film such as a silicon oxide film or a silicon oxynitride film formed in an atmosphere containing oxygen is preferably used. The insulating layer 212 is preferably an insulating layer containing excess oxygen.

The insulating layer 213 is preferably an insulating layer that hardly diffuses and transmits oxygen, such as a silicon nitride film. An insulating layer formed in an atmosphere containing oxygen and an insulating layer containing excess oxygen easily release a large amount of oxygen by heating. Oxygen can be supplied to the channel formation region of the semiconductor layer 231 by performing heat treatment in a state where such an insulating layer from which oxygen is released and an insulating layer that hardly diffuses and transmits oxygen are stacked. As a result, oxygen vacancies in the channel formation region and defects at the interface between the channel formation region and the insulating layer 212 can be repaired, and the defect level can be reduced. Thereby, a highly reliable transistor can be realized. Therefore, a display device with extremely high reliability can be realized.

[Step B14]
Next, part of the insulating layer 211, the insulating layer 212, and the insulating layer 213 is selectively removed to reach the opening reaching the conductive layer 221b, the opening reaching the source region of the semiconductor layer 231, and the drain region of the semiconductor layer 231. An opening is provided (see FIG. 10C).

[Step B15]
Next, a conductive layer 222a and a conductive layer 222b are provided over the insulating layer 213 in the display region 235 (see FIG. 10C). The conductive layer 222a and the conductive layer 222b can be formed using a material and a method similar to those of the conductive layer 225. The conductive layer 222a and the conductive layer 222b can be obtained by processing the same conductive film. The conductive layers 222a and 222b are formed using a conductive material that transmits visible light.

In this manner, transistors (such as the transistor 203 and the transistor 206) in the display region 235 can be provided. Note that one of the conductive layer 222 a and the conductive layer 222 b is electrically connected to one of a source region and a drain region of the semiconductor layer 231. The other of the conductive layer 222 a and the conductive layer 222 b is electrically connected to the other of the source region and the drain region of the semiconductor layer 231.

Thus, one of the conductive layer 222a and the conductive layer 222b can function as a source electrode. The other of the conductive layer 222a and the conductive layer 222b can function as a drain electrode. Note that in FIG. 10C, the conductive layer 222b of the transistor 206 is electrically connected to the conductive layer 221b.

In the transistor included in the display region 235, at least one of the gate electrode, the source electrode, the drain electrode, and the semiconductor layer is formed using a light-transmitting material. Therefore, a region that transmits visible light can be provided in the transistor included in the display region 235. Although not illustrated, the pair of electrodes forming the capacitor in the display region 235 is also formed using a light-transmitting material. Therefore, a region that transmits visible light can be provided in the capacitor included in the display region 235.

[Step B16]
Next, a conductive layer 224a and a conductive layer 224b are provided over the insulating layer 213 in the peripheral circuit region 234 (see FIG. 11A). The conductive layer 224a and the conductive layer 224b can be formed using a material and a method similar to those of the conductive layer 221a. The conductive layer 224a and the conductive layer 224b can be obtained by processing the same conductive film. The conductive layers 224a and 224b are formed using a light-blocking conductive material (metal material) with low resistivity.

In this manner, a transistor (such as the transistor 201) in the peripheral circuit region 234 can be provided. Note that one of the conductive layer 224 a and the conductive layer 224 b is electrically connected to one of a source region and a drain region of the semiconductor layer 231. The other of the conductive layer 224 a and the conductive layer 224 b is electrically connected to the other of the source region and the drain region of the semiconductor layer 231.

Thus, one of the conductive layer 224a and the conductive layer 224b can function as a source electrode. The other of the conductive layer 224a and the conductive layer 224b can function as a drain electrode.

In the transistor included in the peripheral circuit region 234, a gate electrode, a source electrode, and a drain electrode are formed using a light-blocking material. Therefore, the transistor included in the peripheral circuit region 234 can be a light-blocking transistor. Although not shown, the pair of electrodes forming the capacitor in the peripheral circuit region 234 is also formed using a light-shielding material. Therefore, the capacitor included in the display region 235 can be a capacitor having a light shielding property.

[Step B17]
Next, the insulating layer 214 is formed (see FIG. 11B). The insulating layer 214 is a layer to be a formation surface of a display element to be formed later, and thus preferably functions as a planarization layer. As the insulating layer 214, a resin or an inorganic insulating film that can be used for the insulating layer 121 can be used. The insulating layer 214 may be formed using a photosensitive material or a non-photosensitive material (also referred to as a non-photosensitive material).

When a photosensitive material is used for the insulating layer 214, part of the insulating layer 214 can be removed and a desired shape of the insulating layer 214 can be formed by photolithography using light. For example, the opening provided in part of the insulating layer 214 can be formed by a photolithography method. Therefore, a resist mask forming process, an etching process, a resist mask removing process, and the like can be omitted.

[Step B18]
Next, an opening 228 that reaches the conductive layer 222b included in the transistor 205 is formed in part of the insulating layer 214 (see FIG. 11B).

[Step B19]
Next, a conductive layer 191 is formed over the insulating layer 214 in the display region 235 (see FIG. 11C). The conductive layer 191 can be formed by forming a conductive film, forming a resist mask, etching the conductive film, and then removing the resist mask. Here, the conductive layer 222b included in the transistor 205 and the conductive layer 191 are electrically connected. The conductive layer 191 is formed using a light-transmitting conductive material.

[Step B20]
Next, an insulating layer 216 which covers an end portion of the conductive layer 191 is formed (see FIG. 12A). As the insulating layer 216, a resin or an inorganic insulating film that can be used for the insulating layer 121 can be used. The insulating layer 216 has an opening in a portion overlapping with the conductive layer 191.

[Step B21]
Next, an EL layer 192 is formed in the display region 235 (see FIG. 12B). The EL layer 192 can be formed by a method such as an evaporation method, a coating method, a printing method, or a discharge method. In the case where the EL layer 192 is separately formed for each pixel 230, the EL layer 192 can be formed by an evaporation method using a shadow mask such as a metal mask or an ink jet method. In the case where the EL layer 192 is not formed for each pixel, an evaporation method that does not use a metal mask can be used.

For the EL layer 192, either a low molecular compound or a high molecular compound can be used, and an inorganic compound may be included.

Note that each step performed after the formation of the EL layer 192 is performed so that the temperature applied to the EL layer 192 is equal to or lower than the heat resistant temperature of the EL layer 192.

[Step B22]
Next, a conductive layer 193 is formed over the EL layer 192 (see FIG. 12C). Part of the conductive layer 193 functions as a common electrode of the light-emitting element 170. The conductive layer 193 is formed using a conductive material that reflects visible light.

As described above, the light-emitting element 170 can be formed. The light-emitting element 170 has a structure in which a conductive layer 191 partly functioning as a pixel electrode, an EL layer 192, and a conductive layer 193 partly functioning as a common electrode are stacked.

Although an example in which a bottom emission light-emitting element is manufactured as the light-emitting element 170 is described here, one embodiment of the present invention is not limited thereto.

The light emitting element may be any of a top emission type, a bottom emission type, and a dual emission type. A conductive film that transmits visible light is used for the electrode from which light is extracted. In addition, a conductive film that reflects visible light is preferably used for the electrode from which light is not extracted.

[Step B23]
Next, an insulating layer 194 is formed so as to cover the conductive layer 193 (see FIG. 13A). The insulating layer 194 functions as a protective layer that suppresses diffusion of impurities such as water into the light-emitting element 170. The light emitting element 170 is sealed with the insulating layer 194. After the conductive layer 193 is formed, the insulating layer 194 is preferably formed without being exposed to the air. The insulating layer 194 is preferably formed using a material with a high barrier property against impurities.

The substrate temperature when the insulating layer 194 is formed is preferably equal to or lower than the heat resistance temperature of the EL layer 192. The insulating layer 194 can be formed by an ALD method, a sputtering method, or the like. The ALD method and the sputtering method are preferable because they can be formed at a low temperature. Use of the ALD method is preferable because coverage of the insulating layer 194 is favorable.

[Step B24]
Next, the substrate 351 is attached to the insulating layer 194 with the use of the adhesive layer 142 (see FIG. 13B).

For the adhesive layer 142, various curable adhesives such as an ultraviolet curable photocurable adhesive, a reactive curable adhesive, a thermosetting adhesive, and an anaerobic adhesive can be used. Further, an adhesive sheet or the like may be used.

The substrate 351 can be formed using a material similar to that of the substrate 361. For the substrate 351, various materials such as glass, quartz, resin, metal, alloy, and semiconductor having a thickness enough to be flexible may be used.

[Step B25]
Next, the separation layer 335 is irradiated with ultraviolet light from the support substrate 334 side in order to separate the support substrate 334 from the layer 336 together with the separation layer 335 (see FIG. 14A).

Note that there are a separation method of the support substrate 334 by a light irradiation separation method or a physical separation method. In both methods, a separation starting point may be formed by separating a part of the layer 336 from the support substrate 334 or the separation layer 335 before separation. For example, a separation starting point may be formed by inserting a sharp-shaped tool such as a blade between the support substrate 331 and the layer 333. Alternatively, the layer 336 may be cut with a sharp tool from the support substrate 334 side or the substrate 351 side to form the separation starting point. Alternatively, the separation starting point may be formed by a method using a laser such as a laser ablation method.

In this embodiment mode, a separation method by light irradiation will be described. Irradiation with ultraviolet light is preferably performed using a linear laser device. The linear laser device is used in a production line such as low-temperature polysilicon (LTPS (Low Temperature Poly-Silicon)). Therefore, effective use of a production line such as LTPS is possible. A linear laser is a laser beam condensed into a rectangular shape (formed into a linear laser beam).

In this embodiment, a linear laser device is used. Specifically, the support substrate 334 and the linear laser light are relatively moved in a direction perpendicular to the major axis direction of the linear laser light and in a direction parallel to the surface of the support substrate 334. In the region irradiated with the laser light, the bonding force between the peeling layer 335 and the layer 336 is reduced.

The wavelength of the irradiated light is preferably 180 nm or more and 450 nm or less. In particular, the wavelength region preferably includes a wavelength of 308 nm or a vicinity thereof. The energy density of the light is preferably from 250 mJ / cm ² or more 400 mJ / cm ² or less, 250 mJ / cm ² or more 360 mJ / cm ² or less being more preferred.

When irradiating light using a laser device, the number of shots of laser light irradiated to the same location can be 1 shot or more and 50 shots or less, preferably more than 1 shot and 10 shots or less, more than 1 shot. 5 shots or less are more preferable.

At both ends in the minor axis direction of the beam, there are portions where the light intensity is low. Therefore, it is preferable to provide an overlapping portion between one shot and the next shot that is equal to or larger than the width of the portion where the light intensity is low. Therefore, the number of shots of laser light is preferably 1.1 shots or more, and more preferably 1.25 shots or more.

Note that in this specification, the number of shots of laser light refers to the number of times laser light is irradiated to a certain point (region), and is determined by the beam width, scan speed, frequency, overlap rate, or the like. Further, there is an overlapping portion between pulses that move the linear beam in a certain scanning direction, that is, between one shot and the next shot, and the overlapping ratio is the overlap ratio. Note that the closer the overlap rate is to 100%, the larger the number of shots, the farther the distance is, the smaller the number of shots, and the faster the scanning speed, the smaller the number of shots.

When the number of shots of the laser beam is 1.1, it means that there is an overlap of about 1/10 width between two consecutive shots, and it can be said that the overlap rate is 10%. Similarly, a 1.25 shot indicates that there is an overlap with a width of about a quarter of the beam between two consecutive shots, and it can be said that the overlap rate is 25%.

Incidentally, the energy density of the light irradiated in the laser crystallization process of LTPS is high, for example, 350 mJ / cm ² or more and 400 mJ / cm ² or less. Also, a large number of laser shots are required, and examples include 10 shots or more and 100 shots or less.

On the other hand, in this embodiment mode, light irradiation for separating the separation layer 335 and the layer 336 can be performed with an energy density lower than that used in the laser crystallization step or with a smaller number of shots. Therefore, the number of substrates that can be processed by the laser device can be increased. In addition, it is possible to reduce the running cost of the laser device, such as reducing the frequency of maintenance of the laser device. Accordingly, manufacturing cost of a display device and the like can be reduced.

Further, since the light irradiation is performed with an energy density lower than that used in the laser crystallization process or with a smaller number of shots, damage to the substrate due to the laser light irradiation can be reduced. For this reason, even if the substrate is used once, the strength is hardly lowered and the substrate can be reused. Therefore, the cost can be suppressed.

In this embodiment, a separation layer 335 is provided between the support substrate 334 and the layer 336. By using the separation layer 335, light irradiation may be performed with a lower energy density or a smaller number of shots than in the case where the separation layer 335 is not used.

When irradiating light through the manufacturing substrate, if foreign matter such as dust adheres to the light irradiation surface of the manufacturing substrate, light irradiation unevenness occurs, and a portion having low peelability is formed, and the metal oxide layer and The yield of the process of separating the resin layer may be reduced. Therefore, it is preferable to clean the light irradiation surface before irradiating with light or while irradiating with light. For example, the light irradiation surface of the manufacturing substrate can be cleaned using an organic solvent such as acetone, water, or the like. Moreover, you may irradiate light, spraying gas using an air knife. As a result, light irradiation unevenness can be reduced and the separation yield can be improved.

[Step B26]
Subsequently, the support substrate 334 is separated from the layer 336 together with the separation layer 335 (see FIG. 14B).

It is preferable to supply a liquid containing water to the separation interface before or during the separation. The presence of water at the separation interface can further reduce the adhesion or adhesion between the release layer 335 and the layer 336 and reduce the force required for separation. In addition, supplying a liquid containing water to the separation interface may have an effect of weakening or cutting the bond between the peeling layer 335 and the layer 336. Separation can proceed by breaking the bond between the release layer 335 and the layer 336 using a chemical bond with the liquid. For example, in the case where a hydrogen bond is formed between the separation layer 335 and the layer 336, a hydrogen bond is formed between water and the separation layer 335 or the layer 336 by supplying a liquid containing water. It is possible that a hydrogen bond between the release layer 335 and the layer 336 is broken.

The release layer 335 preferably has low surface tension and high wettability with respect to a liquid containing water. The liquid containing water is spread over the entire surface of the release layer 335, and the liquid containing water can be easily supplied to the separation interface. Uniform peeling can be achieved by spreading water throughout the peeling layer 335.

The presence of a liquid containing water at the separation interface can suppress the static electricity generated during the separation from adversely affecting the functional elements included in the layer to be peeled (for example, the semiconductor element is destroyed by static electricity). Further, the surface of the layer to be peeled exposed by separation may be neutralized using an ionizer or the like.

When the liquid is supplied to the separation interface, the surface of the layer to be peeled exposed by the separation may be dried.

[Step B27]
Next, the layer 336 and the insulating layer 337 are removed. For example, the layer 336 and the insulating layer 337 can be removed by a dry etching method or the like. Thus, the electrode 311 is exposed (see FIG. 15A). In FIG. 15A, the removed layer 336 and the insulating layer 337 are indicated by broken lines.

[Step B28]
Next, an alignment film 133a is formed over the exposed surface of the electrode 311 (see FIG. 15B). The alignment film 133a can be formed by performing an alignment process (such as a rubbing process or an optical alignment process) after forming a thin film of resin or the like. In this manner, the transistor substrate 181 can be manufactured.

[Display device 100]
Next, a method for manufacturing the display device 100 using the counter substrate 171 and the transistor substrate 181 will be described.

[Step C1]
The counter substrate 171 and the transistor substrate 181 are attached to each other with the liquid crystal 112 interposed therebetween (see FIG. 16A). Note that although not illustrated in FIG. 16A, the substrate 351 and the substrate 361 are attached to each other with an adhesive layer 141 as illustrated in FIG. A material that can be used for the adhesive layer 142 can be used for the adhesive layer 141.

In addition, the counter substrate 171 and the transistor substrate 181 are attached to each other with the liquid crystal 112 interposed therebetween, whereby the liquid crystal element 180 is formed. The liquid crystal element 180 has a structure in which an electrode 311 that partially functions as a pixel electrode, an alignment film 133a, an alignment film 133b, a liquid crystal 112, and an electrode 113 that partially functions as a common electrode are stacked. In addition, the conductive layer 193 of the light-emitting element 170 functions as a reflective electrode of the liquid crystal element 180.

[Step C2]
Next, the functional member 135 is provided over the substrate 361 (see FIG. 16B). Here, a circularly polarizing plate is provided as the functional member 135.

As described above, the display device 100 can be manufactured. The light-emitting element 170 and the liquid crystal element 180 are provided so as to overlap with the colored layer 131.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 3)
In this embodiment, a display device 150 having a configuration different from that of the display device 100 will be described. In order to reduce the repetition of the description, portions different from the display device 100 will be mainly described.

<Configuration example>
The display device 150 includes a transistor having a structure different from that of the transistor included in the display device 100. FIG. 17 shows an example of a cross section of the display device 150. Similar to the display device 100 illustrated in FIG. 3, the display device 150 illustrated in FIG. 17 includes a transistor 201, a transistor 203, a transistor 205, a transistor 206, a capacitor 202, a liquid crystal element 180, and a light emission between the substrate 351 and the substrate 361. The element 170, the insulating layer 220, the coloring layer 131, the coloring layer 134, and the like are included.

The transistor 201, the transistor 203, the transistor 205, and the transistor 206 included in the display device 150 are bottom-gate transistors.

<Example of production method>
Next, an example of a method for manufacturing the display device 150 will be described.
Similarly to the display device 100, the display device 150 is manufactured by combining the counter substrate 171 and the transistor substrate 181.

[Counter substrate 171]
The counter substrate 171 used for manufacturing the display device 150 may be manufactured similarly to the counter substrate 171 used for manufacturing the display device 100.

[Transistor substrate 181]
A method for manufacturing the transistor substrate 181 used for manufacturing the display device 150 is described. Note that in order to reduce the repetition of the description, portions that are different from the manufacturing method of the transistor substrate 181 used mainly for manufacturing the display device 100 will be described.

First, the process is similarly performed up to step B6 shown in the second embodiment.

[Step D1]
Next, a conductive layer 222a and a conductive layer 222b are provided over the insulating layer 211 in the display region 235 (see FIG. 18A). The conductive layer 222a and the conductive layer 222b can be formed using a material and a method similar to those of the conductive layer 225. The conductive layer 222a and the conductive layer 222b can be obtained by processing the same conductive film. The conductive layers 222a and 222b are formed using a conductive material that transmits visible light.

The conductive layer 222 a has a region in contact with part of the semiconductor layer 231. The conductive layer 222 b includes a region in contact with another part of the semiconductor layer 231. One of the conductive layer 222a and the conductive layer 222b can function as a source electrode. The other of the conductive layer 222a and the conductive layer 222b can function as a drain electrode.

[Step D2]
Next, a conductive layer 224a and a conductive layer 224b are provided over the insulating layer 211 in the peripheral circuit region 234 (see FIG. 18B). The conductive layer 224a and the conductive layer 224b can be formed using a material and a method similar to those of the conductive layer 221a. The conductive layer 224a and the conductive layer 224b can be obtained by processing the same conductive film. The conductive layers 224a and 224b are formed using a light-blocking conductive material (metal material) with low resistivity.

The conductive layer 224 a has a region in contact with part of the semiconductor layer 231. The conductive layer 224 b includes a region in contact with another part of the semiconductor layer 231. One of the conductive layer 224a and the conductive layer 224b can function as a source electrode. The other of the conductive layer 224a and the conductive layer 224b can function as a drain electrode.

[Step D3]
Next, an insulating layer 212 is provided (see FIG. 18C). The insulating layer 212 can be provided using a material and a method similar to those of the insulating layer 211.

Note that as the insulating layer 212, an insulating film such as a silicon oxide film or a silicon oxynitride film formed in an atmosphere containing oxygen is preferably used. The insulating layer 212 is preferably an insulating layer containing excess oxygen.

[Step D4]
Next, in the display region 235, the conductive layer 223 having a region overlapping with the semiconductor layer 231 is provided over the insulating layer 212 (see FIG. 18C). The conductive layer 223 can be formed by forming a conductive film, forming a resist mask, etching the conductive film, and then removing the resist mask. The conductive layer 223 is formed using a light-transmitting conductive material. The conductive layer 223 can be provided using a material and a method similar to those of the conductive layer 225.

[Step D5]
Next, in the peripheral circuit region 234, a conductive layer 226 having a region overlapping with the semiconductor layer 231 is provided over the insulating layer 212 (see FIG. 19A). The conductive layer 226 can be formed by forming a conductive film, then forming a resist mask, etching the conductive film, and then removing the resist mask. The conductive layer 226 is formed using a light-blocking conductive material. The conductive layer 226 can be provided using a material and a method similar to those of the conductive layer 221a.

[Step D6]
Next, an insulating layer 213 is provided (see FIG. 19B). The insulating layer 213 is preferably an insulating layer that hardly diffuses and transmits oxygen, such as a silicon nitride film.

In this manner, a transistor (such as the transistor 201) in the peripheral circuit region 234 can be provided. In addition, transistors (such as the transistor 203 and the transistor 206) in the display region 235 can be provided.

In the transistor included in the peripheral circuit region 234, a gate electrode, a source electrode, and a drain electrode are formed using a light-blocking material. Therefore, the transistor included in the peripheral circuit region 234 can be a light-blocking transistor. Although not shown, the pair of electrodes forming the capacitor in the peripheral circuit region 234 is also formed using a light-shielding material. Therefore, the capacitor included in the display region 235 can be a capacitor having a light shielding property.

In the transistor included in the display region 235, at least one of a gate electrode, a source electrode, a drain electrode, and a semiconductor layer is formed using a light-transmitting material. Therefore, a region that transmits visible light can be provided in the transistor included in the display region 235. Although not illustrated, the pair of electrodes forming the capacitor in the display region 235 is also formed using a light-transmitting material. Therefore, a region that transmits visible light can be provided in the capacitor included in the display region 235.

[Step D7]
Next, the insulating layer 214 is formed (see FIG. 19C). The insulating layer 214 is a layer to be a formation surface of a display element to be formed later, and thus preferably functions as a planarization layer. As the insulating layer 214, a resin or an inorganic insulating film that can be used for the insulating layer 121 can be used. The insulating layer 214 may be formed using a photosensitive material or a non-photosensitive material (also referred to as a non-photosensitive material).

[Step D8]
Next, an opening 228 that reaches the conductive layer 222b included in the transistor 205 is formed in part of the insulating layer 212, the insulating layer 213, and the insulating layer 214 (see FIG. 19C).

[Step D9]
Next, a conductive layer 191 is formed over the insulating layer 214 in the display region 235 (see FIG. 20A). The conductive layer 191 can be formed by forming a conductive film, forming a resist mask, etching the conductive film, and then removing the resist mask. Here, the conductive layer 222b included in the transistor 205 and the conductive layer 191 are electrically connected. The conductive layer 191 is formed using a light-transmitting conductive material.

The subsequent manufacturing steps may be performed in the same manner as in the step B20 and subsequent steps. In this manner, the transistor substrate 181 used for manufacturing the display device 150 can be manufactured (see FIG. 20B).

[Display device 150]
Similarly to Step C1 and Step C2 in Embodiment 2, the counter substrate 171 and the transistor substrate 181 are attached to each other with the liquid crystal 112 interposed therebetween, and the functional member 135 is provided over the substrate 361, whereby the display device 150 is manufactured. be able to.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 4)
In this embodiment, a configuration example of the display device 100 will be described.

The display device 100 can have various modes or have various display elements. Examples of display elements include EL (electroluminescence) elements (organic EL elements, inorganic EL elements, or EL elements including organic and inorganic substances), LEDs (white LEDs, red LEDs, green LEDs, blue LEDs, etc.), transistors (Transistor that emits light in response to current), electron-emitting device, liquid crystal device, electronic ink, electrophoretic device, GLV (grating light valve), display device using MEMS (micro electro mechanical system), DMD (digital Micromirror device), DMS (digital micro shutter), MIRASOL (registered trademark), IMOD (interferometric modulation) element, shutter type MEMS display element, optical interference type MEMS display element, electrowetting Child, piezoceramic display, display using carbon nanotubes, etc., by electrical or magnetic action, those having contrast, brightness, reflectance, a display medium such as transmittance changes. Further, quantum dots may be used as the display element.

An example of a display device using an EL element is an EL display device. As an example of a display device using an electron-emitting device, there is a field emission display (FED) or a surface-conduction electron-emitting device display (SED: Surface-conduction Electron-Emitter Display). An example of a display device using quantum dots is a quantum dot display device.

As an example of a display device using a liquid crystal element, there is a liquid crystal display device (a transmissive liquid crystal display device, a transflective liquid crystal display device, a reflective liquid crystal display device, a direct view liquid crystal display device, a projection liquid crystal display device), or the like. . An example of a display device using electronic ink, electronic powder fluid (registered trademark), or an electrophoretic element is electronic paper. The display device may be a PDP (Plasma Display Panel). The display device may be a retinal scanning type projection device. Moreover, the display apparatus using micro LED may be sufficient.

Note that in the case of realizing a transflective liquid crystal display device or a reflective liquid crystal display device, a part or all of the pixel electrode may have a function as a reflective electrode. For example, part or all of the pixel electrode may have aluminum, silver, or the like. Further, in that case, a memory circuit such as an SRAM can be provided under the reflective electrode. Thereby, power consumption can be further reduced.

In addition, when using LED, you may arrange | position graphene or graphite under the electrode and nitride semiconductor of LED. Graphene or graphite may be a multilayer film in which a plurality of layers are stacked. Thus, by providing graphene or graphite, a nitride semiconductor, for example, an n-type GaN semiconductor layer having a crystal can be easily formed thereon. Furthermore, a p-type GaN semiconductor layer having a crystal or the like can be provided thereon to form an LED. Note that an AlN layer may be provided between graphene or graphite and an n-type GaN semiconductor layer having a crystal. Note that the GaN semiconductor layer of the LED may be formed by MOCVD. However, by providing graphene, the GaN semiconductor layer of the LED can be formed by a sputtering method.

The display device 100 and the like described in this specification and the like include both a reflective display element and a light-emitting display element (also referred to as a “light-emitting element”), and can display both in a reflective mode and a light-emitting mode. It is a display device that can. More specifically, a reflective liquid crystal element is included as the reflective display element, and an EL element is included as the light emitting display element. Therefore, it can function as an EL display device and can also function as a liquid crystal display device.

A configuration example of the display device 100 will be described. FIG. 21A is a block diagram illustrating a configuration example of the display device 100. The display device 100 includes a display area 235 and a peripheral circuit area 234. The peripheral circuit region 234 includes a circuit 232 and a circuit 233.

Note that in the display device 100 of one embodiment of the present invention, the circuit 233 is provided in the IC 373 (see FIG. 1A).

The display region 235 includes a plurality of pixels 230, a plurality of wirings G1, a plurality of wirings G2, a plurality of wirings ANO, a plurality of wirings CSCOM, a wiring S1, and a plurality of wirings S2 arranged in a matrix (FIG. 21A). reference.). The wiring G1, the wiring G2, the wiring ANO, and the wiring CSCOM are electrically connected to the circuits 232 of the plurality of pixels 230 arranged in the direction R. The wiring S1 and the wiring S2 are electrically connected to the circuits 233 of the plurality of pixels 230 arranged in the direction C.

The wiring G1 corresponds to the scanning line 273. The wiring G2 corresponds to the scanning line 284. The wiring ANO corresponds to the power supply line 286. The wiring CSCOM corresponds to the common potential line 275. The wiring S1 corresponds to the signal line 274. The wiring S2 corresponds to the signal line 285 (see FIGS. 21A and 2A).

Although FIG. 21A illustrates a structure including one circuit 232 and one circuit 233, the circuit 232 and the circuit 233 that drive the liquid crystal element 180 and the circuit 232 and the circuit 233 that drive the light-emitting element 170 are separately provided. May be provided.

Alternatively, part or all of the circuit 232 and the circuit 233 may be formed over another substrate and electrically connected to the display device 100. For example, part or all of the circuit 232 and the circuit 233 may be formed using a single crystal substrate and electrically connected to the display device 100.

The pixel 230 includes a reflective liquid crystal element 180 that functions as a reflective display element, and an EL element that functions as a light-emitting element 170. In the pixel 230, the liquid crystal element 180 and the light emitting element 170 have portions that overlap each other.

The pixel 230 that emits or reflects red light, the pixel 230 that emits or reflects green light, and the pixel 230 that emits or reflects blue light collectively function as one pixel 240, and the amount of light emitted from each pixel 230 (reflection) By controlling (luminance), full color display can be realized. Therefore, each of the three pixels 230 functions as a sub-pixel. That is, each of the three sub-pixels controls the transmittance, reflectance, light emission amount, or the like of red light, green light, or blue light (see FIG. 21B1). The light color controlled by each of the three sub-pixels is not limited to the combination of red (R), green (G), and blue (B), but is cyan (C), magenta (M), and yellow (Y). It may be present (see FIG. 21B2).

Further, the four subpixels may be combined to function as one pixel. For example, a subpixel that controls white light may be added to three subpixels that control red light, green light, and blue light (see FIG. 21B3). By adding a sub-pixel that controls white light, the luminance of the display area can be increased. Further, a sub-pixel that controls yellow light may be added to the three sub-pixels that control red light, green light, and blue light, respectively (see FIG. 21 (B4)). Further, a sub-pixel that controls white light may be added to the three sub-pixels that respectively control cyan light, magenta light, and yellow light (see FIG. 21B5).

Increasing the number of sub-pixels that function as one pixel and expanding the reproducible color gamut by using appropriate combinations of sub-pixels that control light such as red, green, blue, cyan, magenta, and yellow it can. Further, the reproducibility of halftone can be improved. Therefore, display quality can be improved.

In addition, when the pixels 240 are arranged in a 1920 × 1080 matrix, the 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”) is realized. can do. Further, for example, when the pixels 240 are arranged in a 3840 × 2160 matrix, the display device 100 is capable of full-color display at a resolution of so-called ultra high vision (also referred to as “4K resolution”, “4K2K”, or “4K”). Can be realized. Further, for example, when the pixels 240 are arranged in a 7680 × 4320 matrix, the display device 100 is capable of full-color display at a resolution of so-called super high vision (also referred to as “8K resolution”, “8K4K”, or “8K”). Can be realized. By increasing the number of pixels 240, it is possible to realize the display device 100 capable of full-color display at a resolution of 16K or 32K.

Various sequential circuits such as a shift register can be used for the circuit 232. A transistor, a capacitor, or the like can be used for the circuit 232. A transistor included in the circuit 232 can be formed in the same process as the transistor included in the pixel 230.

The circuit 233 is electrically connected to the wiring S1. For the circuit 233, for example, an integrated circuit can be used. Specifically, for the circuit 233, an integrated circuit formed over a silicon substrate can be used.

For example, the circuit 233 can be mounted on a pad electrically connected to the pixel 230 by using a COG (Chip on glass) method, a COF method, or the like. Specifically, an integrated circuit can be mounted on the pad using an anisotropic conductive film.

<Circuit Configuration Example of Pixel 230>
FIG. 22 is a diagram illustrating a circuit configuration example of the pixel 230. In FIG. 22, two adjacent pixels 230 are shown.

The pixel 230 includes a switch SW1, a capacitor C1, a liquid crystal element 180, a switch SW2, a transistor M, a capacitor C2, a light emitting element 170, and the like. In addition, a wiring G1, a wiring G2, a wiring ANO, a wiring CSCOM, a wiring S1, and a wiring S2 are electrically connected to the pixel 230. In FIG. 23, a wiring VCOM1 electrically connected to the liquid crystal element 180 and a wiring VCOM2 electrically connected to the light emitting element 170 are illustrated.

FIG. 22 shows an example in which transistors are used for the switch SW1 and the switch SW2. Note that the switch SW1 corresponds to the transistor 271. The switch SW2 corresponds to the transistor 281. The transistor M corresponds to the transistor 283. The capacitive element C1 corresponds to the capacitive element 272. The capacitor C2 corresponds to the capacitor 282 (see FIGS. 22 and 2A).

The switch SW1 has a gate connected to the wiring G1, one source or drain connected to the wiring S1, and the other source or drain connected to one electrode of the capacitor C1 and one electrode of the liquid crystal element 180. Yes. The other electrode of the capacitor C1 is connected to the wiring CSCOM. The other electrode of the liquid crystal element 180 is connected to the wiring VCOM1.

The switch SW2 has a gate connected to the wiring G2, one of the source and the drain connected to the wiring S2, and the other of the source and the drain connected to one electrode of the capacitor C2 and the gate of the transistor M. The other electrode of the capacitor C2 is connected to one of the source and the drain of the transistor M and the wiring ANO. The other of the source and the drain of the transistor M is connected to one electrode of the light emitting element 170. The other electrode of the light emitting element 170 is connected to the wiring VCOM2.

FIG. 22 shows an example in which the transistor M has two gates sandwiching a semiconductor and these are connected. As a result, the current that can be passed by the transistor M can be increased.

A signal for controlling the switch SW1 to be in a conductive state or a non-conductive state can be supplied to the wiring G1. A predetermined potential can be applied to the wiring VCOM1. A signal for controlling the alignment state of the liquid crystal included in the liquid crystal element 180 can be supplied to the wiring S1. A predetermined potential can be applied to the wiring CSCOM.

A signal for controlling the switch SW2 to be in a conductive state or a non-conductive state can be supplied to the wiring G2. The wiring VCOM2 and the wiring ANO can each be supplied with a potential at which a potential difference generated by the light emitting element 170 emits light. A signal for controlling the conduction state of the transistor M can be supplied to the wiring S2.

For example, when performing display in a reflection mode, the pixel 230 illustrated in FIG. 22 can be driven by a signal supplied to the wiring G1 and the wiring S1 and can display using optical modulation by the liquid crystal element 180. Further, in the case of performing display in the light emission mode, the light emitting element 170 can be driven to display by driving with a signal given to the wiring G2 and the wiring S2. In the case of driving in both modes, the driving can be performed by signals given to the wiring G1, the wiring G2, the wiring S1, and the wiring S2.

Note that although FIG. 22 illustrates an example in which one pixel 230 includes one liquid crystal element 180 and one light emitting element 170, the present invention is not limited thereto. FIG. 23 illustrates an example in which one pixel 230 includes one liquid crystal element 180 and four light emitting elements 170 (light emitting element 170r, light emitting element 170g, light emitting element 170b, and light emitting element 170w). A pixel 230 illustrated in FIG. 23 is a pixel capable of full color display with one pixel, unlike FIG.

In FIG. 23, in addition to the example of FIG. 22, a wiring G3 and a wiring S3 are connected to the pixel 230.

In the example illustrated in FIG. 23, for example, as the four light emitting elements 170, light emitting elements exhibiting red (R), green (G), blue (B), and white (W) can be used. As the liquid crystal element 180, a reflective liquid crystal element exhibiting white can be used. Thereby, when displaying in reflection mode, white display with high reflectance can be performed. In addition, when display is performed in the light emission mode, display with high color rendering properties can be performed with low power.

<Display mode>
The display device 100 can be operated in three display modes. The first display mode (mode 1) is a display mode for displaying an image as a reflective liquid crystal display device. The second display mode (mode 2) is a display mode for displaying an image as a light emitting display device. The third display mode (mode 3) is a display mode in which the first display mode and the second display mode are simultaneously applied.

[First display mode]
Since the first display mode does not require a light source, it is a display mode with extremely low power consumption. For example, it is particularly effective when the illuminance of outside light is sufficiently large and the outside light is white light or light in the vicinity thereof. The first display mode is particularly effective when used in an environment where the illuminance is greater than about 300 lx, for example, in the daytime. However, the display device 100 may be operated in the first display mode even in an environment where the illuminance is smaller than about 300 lx depending on the purpose or application.

The first display mode is a display mode suitable for displaying character information such as books and documents. Since reflected light is used to display an image, it is possible to perform display that is gentle to the eyes, and the effect that the eyes are less tired is achieved.

FIG. 24A1 illustrates a state in which the electronic device 910 is used outdoors during the daytime. In FIG. 24A1, the display device of the electronic device 910 operates in the first display mode. The electronic device 910 is a portable information terminal such as a smartphone, for example. The electronic device 910 includes the display device 100 of one embodiment of the present invention.

FIG. 24A2 illustrates incident light 901 that enters the display device 100 of the electronic device 910 and reflected light 902 that the display device 100 reflects.

[Second display mode]
The second display mode is a display mode in which extremely vivid (high contrast and high color reproducibility) display can be performed regardless of the illuminance and chromaticity of external light. For example, it is effective when the illuminance of outside light is small, such as at night or indoors. The second display mode is particularly effective when used in an environment where the illuminance is less than about 5000 lx. However, the display device 100 may be operated in the second display mode even under an environment where the illuminance is greater than about 5000 lx depending on the purpose or application. In addition, when the illuminance of external light is small, the user may feel dazzled when performing bright display. In order to prevent this, it is preferable to perform display with reduced luminance in the second display mode. Thereby, in addition to suppressing glare, power consumption can also be reduced. The second display mode is a mode suitable for displaying a vivid image or a smooth moving image.

FIG. 24B1 illustrates that the electronic device 910 is used outdoors at night. Moreover, the electronic device 920 in the figure is an electronic device used for digital signage. In FIG. 24B1, the display devices of the electronic device 910 and the electronic device 920 operate in the second display mode. The electronic device 920 includes the display device 100 of one embodiment of the present invention.

FIG. 24B2 illustrates light emission 903 emitted from the display device 100 of the electronic device 910 and light emission 903 emitted from the display device 100 of the electronic device 920.

[Third display mode]
The third display mode is a display mode in which display is performed using both reflected light in the first display mode and light emission in the second display mode. For example, when it is necessary to emit light from the display device 100 that is equal to or higher than the maximum reflection luminance in the first display mode, the necessary light amount can be supplemented by light emission in the second display mode. Further, for example, it is possible to drive to express one color by mixing the reflected light in the first display mode and the light emission in the second display mode.

In the third display mode, it is possible to suppress power consumption more than in the second display mode while displaying more vividly than in the first display mode. For example, it is effective when the illuminance of outside light is relatively low, such as under room lighting or in the morning or evening hours, or when the chromaticity of outside light is not white.

The third display mode is particularly effective when used in an environment where the illuminance is less than about 5000 lx. However, the display device 100 may be operated in the third display mode even in an environment where the illuminance is greater than about 5000 lx depending on the purpose or application.

FIG. 24C1 illustrates a state where the electronic device 910 is used indoors. In addition, an electronic device 930 in the figure is an electronic device that can function as a television or a monitor. Also, the electronic device 940 in the figure is a notebook personal computer. In FIG. 24C1, the display device included in the electronic device 910, the electronic device 930, and the electronic device 940 operates in the third display mode. The electronic device 930 and the electronic device 940 each include the display device 100 of one embodiment of the present invention.

FIG. 24C2 shows light emission 903 emitted from the display device 100 of the electronic device 910, incident light 901 incident on the display device 100 of the electronic device 910, and reflected light 902 reflected by the display device 100 of the electronic device 910. Show. Further, light emission 903 emitted from the display device 100 of the electronic device 930, incident light 901 incident on the display device 100 of the electronic device 930, and reflected light 902 reflected by the display device 100 of the electronic device 930 are shown. The display device 100 of the electronic device 940 can function in the same manner as the other display devices 100.

Note that the display using the third display mode can be said to be a hybrid display mode. Hybrid display is a method of displaying characters or images on one panel by using reflected light and self-light emission in combination with each other to complement color tone or light intensity. Alternatively, the hybrid display is a method for displaying characters and / or images using light from a plurality of display elements in the same pixel or the same sub-pixel. However, when a display device that performs hybrid display (also referred to as “hybrid display device” or “hybrid display”) is viewed locally, pixels or subpixels displayed using any one of a plurality of display elements And a pixel or sub-pixel displayed using two or more of the plurality of display elements.

Note that in this specification and the like, a display that satisfies any one or a plurality of expressions of the above configuration is referred to as a hybrid display.

The hybrid display has a plurality of display elements in the same pixel or the same sub-pixel. Examples of the plurality of display elements include a reflective element that reflects light and a self-luminous element that emits light. Note that the reflective element and the self-luminous element can be controlled independently. The hybrid display has a function of displaying characters and / or images in the display unit using either or both of reflected light and self-light emission.

<Specific examples of first to third display modes>
Here, a specific example in the case where the above-described first to third display modes are used will be described with reference to FIGS.

Hereinafter, a case where the first to third display modes are automatically switched according to the illuminance will be described. In addition, when switching automatically according to illumination intensity, an illumination sensor etc. can be provided in a display apparatus, for example, and a display mode can be switched based on the information from the said illumination intensity sensor.

FIG. 25A, FIG. 25B, and FIG. 25C are schematic diagrams of pixels for describing display modes that can be taken by the display device of one embodiment of the present invention.

In FIGS. 25A, 25B, and 25C, the first display element 501, the second display element 502, the reflected light 504 controlled by the first display element 501, and the first display element 501 are used. The transmitted light 505 emitted from the second display element 502 is clearly shown. 25A is a diagram for explaining the first display mode, FIG. 25B is a diagram for explaining the second display mode, and FIG. 25C is a diagram showing the third display mode. It is a figure explaining.

25A, 25B, and 25C, a reflective liquid crystal element is used as the first display element 501, and a light-emitting element is used as the second display element 502. Suppose.

A first display element 501 described in this embodiment corresponds to the liquid crystal element 180 described in the above embodiment. The first display element 502 corresponds to the light emitting element 170.

In the first display mode illustrated in FIG. 25A, gradation display can be performed by driving a reflective liquid crystal element which is the first display element 501 to adjust the intensity of reflected light.

In the second display mode illustrated in FIG. 25B, gradation display can be performed by adjusting light emission intensity of the light-emitting element which is the second display element 502. Note that light emitted from the second display element 502 passes through the first display element 501 and is extracted to the outside as transmitted light 505.

The third display mode shown in FIG. 25C is a display mode in which the first display mode and the second display mode described above are combined. For example, the first display element 501 performs gradation display by adjusting the intensity of the reflected light 504 using a liquid crystal layer. Further, gradation display is performed by adjusting the light emission intensity of the light-emitting element, which is the second display element 502, in this case, the intensity of the transmitted light 505, within the same period as the period during which the first display element 501 is driven.

<State transition in first to third display modes>
Next, state transition in the first to third display modes will be described with reference to FIG. FIG. 4D is a state transition diagram of the first display mode, the second display mode, and the third display mode. State C1 shown in FIG. 25D corresponds to the first display mode, state C2 corresponds to the second display mode, and state C3 corresponds to the third display mode.

As shown in FIG. 25D, from the state C1 to the state C3, a display mode in any state can be taken depending on the illuminance. For example, when the illuminance is high, such as outdoors, the state C1 can be taken. In addition, when the illuminance is low, such as when moving from outdoors to indoors, the state changes from state C1 to state C2. Further, when the illuminance is low even outdoors, and the gradation display by reflected light is not sufficient, the state C2 is changed to the state C3. Of course, a transition from state C3 to state C1, a transition from state C1 to state C3, a transition from state C3 to state C2, or a transition from state C2 to state C1 also occurs.

In FIG. 25D, a sun symbol is used as the first display mode image, a moon symbol is used as the second display mode image, a cloud symbol is used as the third display mode image, Each is illustrated.

Note that, as illustrated in FIG. 25D, in the state C1 to the state C3, when there is no change in illuminance or when the change in illuminance is small, the original state is continued without changing to another state. Should be maintained.

As described above, by adopting a configuration in which the display mode is switched according to the illuminance, the frequency of gradation display of the second display element 502 with relatively large power consumption can be reduced. Therefore, power consumption of the display device can be reduced. The display device can further switch the operation mode according to the remaining capacity of the battery, the content to be displayed, or the illuminance of the surrounding environment. In the above description, the case where the display mode is automatically switched according to the illuminance is illustrated, but the present invention is not limited to this, and the user may manually switch the display mode.

<Operation mode>
Next, operation modes that can be performed in the first display element and the second display element will be described with reference to FIGS.

In the following, a normal operation mode (Normal mode) that operates at a normal frame frequency (typically 60 Hz to 240 Hz or less) and an idling stop (IDS) drive mode that operates at a low frame frequency will be exemplified. To explain.

Note that the IDS driving mode refers to a driving method in which image data rewriting is stopped after image data writing processing is executed. Once the image data is written and then the interval until the next image data is written is extended, the power consumption required for writing the image data during that time can be reduced. The IDS drive mode can be set to a frame frequency of about 1/100 to 1/10 of the normal operation mode, for example. A still image has the same video signal between consecutive frames. Therefore, the IDS drive mode is particularly effective when displaying a still image. By displaying an image using IDS driving, power consumption is reduced, flickering of the screen is suppressed, and eye strain can be reduced.

FIG. 26A1, FIG. 26A2, FIG. 26B, and FIG. 26C are timing charts illustrating the pixel circuit and the normal drive mode and the IDS drive mode. Note that FIG. 26A1 illustrates a first display element 501 (here, a reflective liquid crystal element) and a pixel circuit 506 electrically connected to the first display element 501. In the pixel circuit 506 illustrated in FIG. 26A1, the signal line SL, the gate line GL, the transistor M1 connected to the signal line SL and the gate line GL, and the capacitor Cs _LC connected to the transistor M1 Is shown.

FIG. 26A2 illustrates a second display element 502 (light-emitting element, for example, an EL element) and a pixel circuit 507 electrically connected to the second display element 502. In the pixel circuit 507 illustrated in FIG. 26A2, the signal line SL, the gate line GL, the transistor M1 connected to the signal line SL and the gate line GL, and the transistor M1 and the second display element 502 are connected. The illustrated transistor M2, the transistor M1, the transistor M2, and the capacitor Cs _EL connected to the second display element 502 are shown.

Transistor M1 may become a leak path data _{D 1.} Therefore, the off-state current of the transistor M1 is preferably as small as possible. As the transistor M1, a transistor including a metal oxide in a semiconductor layer where a channel is formed is preferably used. When a metal oxide has at least one of an amplifying function, a rectifying function, and a switching function, the metal oxide is referred to as a metal oxide semiconductor or an oxide semiconductor, or OS for short. be able to. Hereinafter, as a typical example of a transistor, a transistor in which an oxide semiconductor is used for a semiconductor layer in which a channel is formed (also referred to as an “OS transistor”) is described. The OS transistor has a feature that leakage current (off-state current) in a non-conduction state is extremely lower than that of a transistor using polycrystalline silicon or the like. By using an OS transistor as the transistor M1, the charge supplied to the node ND1 can be held for a long time.

In particular, the EL element used as the second display element 502 has a higher response speed than the liquid crystal element and is sensitive to voltage fluctuations at the node ND1. Therefore, it is preferable to use an OS transistor as the transistor M1 of the pixel circuit 507 because flicker caused by fluctuations in charge at the node ND1 can be reduced. It should be noted that this effect is remarkable when some of the second display elements 502 are IDS-driven in the third display mode.

A transistor used for the transistor M2 is also preferable as the off-state current is small. By using a transistor with low off-state current as the transistor M2, a phenomenon that light is emitted slightly during black display (also referred to as “black floating”) can be reduced. Therefore, an OS transistor is preferably used as the transistor M2 of the pixel circuit 507.

Note that in the circuit diagram shown in FIG. 26 (A1), the liquid crystal element LC is the leak path of the data _{D 1.} Therefore, in order to appropriately perform IDS driving, it is preferable that the resistivity of the liquid crystal element LC is 1.0 × 10 ¹⁴ Ω · cm or more.

Note that an In—Ga—Zn oxide, an In—Zn oxide, or the like can be preferably used for the channel region of the OS transistor, for example. As the In—Ga—Zn oxide, a composition in the vicinity of In: Ga: Zn = 4: 2: 4.1 [atomic ratio] can be typically used.

FIG. 26B is a timing chart showing waveforms of signals supplied to the signal line SL and the gate line GL in the normal drive mode. In the normal drive mode, it operates at a normal frame frequency (for example, 60 Hz). When one frame period is represented by periods T ₁ to T ₃ , an operation of applying a scanning signal to the gate line GL and writing data D ₁ from the signal line SL to the node ND ₁ in each frame period is performed. This operation is the same even when writing the same data D ₁ in the period T ₁ to T ₃ or writing different data.

On the other hand, FIG. 26C is a timing chart showing waveforms of signals supplied to the signal line SL and the gate line GL in the IDS driving mode, respectively. In the IDS drive, it operates at a low frame frequency (for example, 1 Hz). Represents one frame period in the period T _1, representing the period T _W a write period of data _therein, the data retention period in the period T _RET. IDS drive mode gives a scanning signal to the gate line GL in a period _{T W,} write data _{D 1} of the signal line SL, and a gate line GL is fixed to the low level of the voltage in the period _{T RET,} nonconductive transistor M1 It performs an operation of holding temporarily the data D ₁ written as. In addition, what is necessary is just to set it as 0.1 Hz or more and less than 60 Hz as a low-speed frame frequency, for example.

The IDS drive mode is effective because it can further reduce power consumption by combining with the first display mode, the second display mode, or the third display mode described above.

As described above, the display device of this embodiment can perform display by switching between the first display mode to the third display mode. Therefore, it is possible to realize a display device or an all-weather display device that is highly visible and convenient regardless of the surrounding brightness.

The display device described in this embodiment preferably includes a plurality of first pixels each including a first display element and a plurality of second pixels each including a second display element. In addition, the first pixel and the second pixel are preferably arranged in a matrix.

Each of the first pixel and the second pixel can include one or more subpixels. The display device described in this embodiment can have a structure in which both the first pixel and the second pixel perform full color display. Alternatively, the display device described in this embodiment can have a structure in which the first pixel performs monochrome display or grayscale display, and the second pixel performs full color display. The monochrome display or gray scale display using the first pixel is suitable for displaying information that does not require color display, such as document information.

The display device of one embodiment of the present invention can reproduce color gamuts of various standards. For example, sRGB (standard RGB) widely used in electronic devices such as PAL (Phase Alternating Line) standards and NTSC (National Television System Committee) standards used in television broadcasting, personal computers, digital cameras, printers, etc. ITU-R BT., Which is used in the standard, Adobe RGB standard, HDTV (also known as High Definition Television). 709 (International Telecommunication Union Radiocommunication Sector Broadcasting Service (Television) 709) Standard, DCI-P3 (Digital CinitiitiPUU standard used in digital cinema projection) R BT. A color gamut such as 2020 (REC. 2020 (Recommendation 2020)) standard can be reproduced.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 5)
In this embodiment, an example of a touch sensor driving method will be described with reference to the drawings.

[Example of sensor detection method]
FIG. 27A is a block diagram illustrating a structure of a mutual capacitive touch sensor. FIG. 27A shows a pulse voltage output circuit 551 and a current detection circuit 552. Note that in FIG. 27A, an electrode 521 to which a pulse voltage is applied and an electrode 522 that detects a change in current are illustrated as six wirings of X1-X6 and Y1-Y6, respectively. FIG. 27A illustrates a capacitor 553 which is formed by overlapping the electrode 521 and the electrode 522. Note that the functions of the electrode 521 and the electrode 522 may be interchanged.

The pulse voltage output circuit 551 is a circuit for sequentially applying a pulse voltage to the X1-X6 wirings. When a pulse voltage is applied to the wiring of X1-X6, an electric field is generated between the electrode 521 and the electrode 522 forming the capacitor 553. By utilizing the fact that the electric field generated between the electrodes causes a change in the mutual capacitance of the capacitor 553 due to shielding or the like, it is possible to detect the proximity or contact of the detection object.

The current detection circuit 552 is a circuit for detecting a change in current in the wirings Y1 to Y6 due to a change in mutual capacitance in the capacitor 553. In the wirings Y1 to Y6, there is no change in the current value detected when there is no proximity or contact with the detected object, but the current value when the mutual capacitance decreases due to the proximity or contact with the detected object. Detect changes that decrease. Note that current detection may be performed using an integration circuit or the like.

Note that one or both of the pulse voltage output circuit 551 and the current detection circuit 552 may be formed over the counter substrate 171 or the transistor substrate 181. For example, it is preferable to form the pixel circuit 236 and the circuit 364 at the same time because the number of components used for driving the touch sensor can be reduced in addition to simplifying the process. One or both of the pulse voltage output circuit 551 and the current detection circuit 552 may be mounted on the IC 373.

In particular, when a transistor formed over the transistor substrate 181 uses crystalline silicon such as polycrystalline silicon or single crystal silicon, an oxide semiconductor, or the like for a semiconductor layer in which a channel is formed, the pulse voltage output circuit 551 or the current The driving capability of a circuit such as the detection circuit 552 is improved, and the sensitivity of the touch sensor can be improved.

Next, FIG. 27B shows a timing chart of input / output waveforms in the mutual capacitive touch sensor shown in FIG. In FIG. 27B, it is assumed that the detection target is detected in each matrix in one frame period. FIG. 27B shows two cases, that is, a case where the detected object is not detected (non-touch) and a case where the detected object is detected (touch). In addition, about the wiring of Y1-Y6, the waveform made into the voltage value corresponding to the detected electric current value is shown.

A pulse voltage is sequentially applied to the X1-X6 wiring, and the waveform of the Y1-Y6 wiring changes according to the pulse voltage. When there is no proximity or contact of the detection object, the waveform of Y1-Y6 changes uniformly according to the change of the voltage of the wiring of X1-X6. On the other hand, since the current value decreases at the location where the detection object is close or in contact, the waveform of the voltage value corresponding to this also changes.

In this way, by detecting the change in mutual capacitance, the proximity or contact of the detection target can be detected.

FIG. 27A illustrates a structure of a passive matrix touch sensor in which only a capacitor 553 is provided at a wiring intersection as a touch sensor. However, the touch sensor is an active matrix touch sensor including a transistor and a capacitor. It may be. FIG. 28 shows an example of one sensor circuit included in an active matrix touch sensor.

The sensor circuit includes a capacitor 553, a transistor 561, a transistor 562, and a transistor 563. In the transistor 563, the signal S2 is supplied to the gate, the voltage VRES is supplied to one of the source and the drain, and the other is electrically connected to one electrode of the capacitor 553 and the gate of the transistor 561. One of a source and a drain of the transistor 561 is electrically connected to one of a source and a drain of the transistor 562, and the voltage VSS is supplied to the other. In the transistor 562, a signal S1 is supplied to a gate, and the other of the source and the drain is electrically connected to the wiring ML. The voltage VSS is applied to the other electrode of the capacitor 553.

Next, the operation of the sensor circuit will be described. First, a potential for turning on the transistor 563 is applied as the signal S2, so that a potential corresponding to the voltage VRES is applied to the node n to which the gate of the transistor 561 is connected. Next, a potential for turning off the transistor 563 is supplied as the signal S2, so that the potential of the node n is held.

Subsequently, as the mutual capacitance of the capacitor 553 changes due to the proximity or contact of a detection target such as a finger, the potential of the node n changes from VRES.

In the reading operation, a potential for turning on the transistor 562 is applied to the signal S1. The current flowing through the transistor 561, that is, the current flowing through the wiring ML changes in accordance with the potential of the node n. By detecting this current, the proximity or contact of the detection object can be detected.

As the transistor 561, the transistor 562, and the transistor 563, a transistor in which an oxide semiconductor is used for a semiconductor layer in which a channel is formed is preferably used. In particular, when an oxide semiconductor is used for a semiconductor layer which forms a channel of the transistor 563, the potential of the node n can be held for a long time, and an operation of supplying VRES again to the node n (refresh operation) Can reduce the frequency.

[Example of display device driving method]
FIG. 29A is a block diagram illustrating a structure example of a display device. FIG. 29A shows a display portion having a gate driving circuit GD (scanning line driving circuit), a source driving circuit SD (signal line driving circuit), and a plurality of pixels pix. Note that in FIG. 29A, gate lines x_1 to x_m (m is a natural number) electrically connected to the gate driver circuit GD, and source lines y_1 to y_n (n is a natural number) electrically connected to the source driver circuit SD. ) Corresponding to (1, 1) to (n, m) in the pixel pix.

Next, FIG. 29B is a timing chart of signals supplied to the gate line and the source line in the display device illustrated in FIG. FIG. 29B shows a case where the data signal is rewritten every frame period and a case where the data signal is not rewritten. Note that in FIG. 29B, a period such as a blanking period is not considered.

When the data signal is rewritten every frame period, scanning signals are sequentially applied to the gate lines x_1 to x_m. In the horizontal scanning period 1H in which the scanning signal is at the H level, the data signal D is supplied to the source lines y_1 to y_n of each column.

When the data signal is not rewritten every frame period, the scanning signal applied to the gate lines x_1 to x_m is stopped. In the horizontal scanning period 1H, the data signal applied to the source lines y_1 to y_n in each column is stopped.

A driving method in which a data signal is not rewritten every frame period is particularly effective when an oxide semiconductor is applied to a semiconductor layer in which a channel is formed as a transistor included in the pixel pix. A transistor to which an oxide semiconductor is applied can have extremely low off-state current compared to a transistor to which a semiconductor such as silicon is applied. Therefore, the data signal written in the previous period can be held without rewriting the data signal every frame period. For example, the gradation of the pixel is held for 1 second or more, preferably 5 seconds or more. You can also.

Further, in the case where polycrystalline silicon or the like is applied to a semiconductor layer in which a channel is formed as a transistor included in the pixel pix, it is preferable that the size of the storage capacitor included in the pixel is increased in advance. The larger the storage capacity, the longer the pixel gradation can be stored. The size of the storage capacitor may be set according to the leakage current of a transistor or a display element electrically connected to the storage capacitor. For example, the storage capacitor per pixel is 5 fF or more and 5 pF or less, preferably 10 fF or more and 5 pF. In the following, more preferably 20 fF or more and 1 pF or less, the data signal written in the previous period can be held without rewriting the data signal every frame period. For example, in a period of several frames or several tens frames It is possible to maintain the gradation of the pixels throughout.

[Example of display and touch sensor drive method]
30A to 30D show an example in which the touch sensor described in FIGS. 27A and 27B and the display unit described in FIGS. 29A and 29B are 1 sec. It is a figure explaining the operation | movement of a continuous frame period when driving (for 1 second). FIG. 30A shows a case where one frame period of the display portion is 16.7 ms (frame frequency: 60 Hz) and one frame period of the touch sensor is 16.7 ms (frame frequency: 60 Hz).

In the display device of one embodiment of the present invention, the operation of the display portion and the operation of the touch sensor are independent from each other, and the touch detection period can be provided in parallel with the display period. Therefore, as shown in FIG. 30A, one frame period of the display portion and the touch sensor can both be set to 16.7 ms (frame frequency: 60 Hz). Further, the frame frequency of the touch sensor and the display unit may be different. For example, as shown in FIG. 30B, one frame period of the display unit is set to 8.3 ms (frame frequency: 120 Hz), and one frame period of the touch sensor is set to 16.7 ms (frame frequency: 60 Hz). You can also. Although not shown, the frame frequency of the display unit may be 33.3 ms (frame frequency: 30 Hz).

In addition, the frame frequency of the display unit can be switched, the frame frequency is increased (for example, 60 Hz or more or 120 Hz or more) when displaying a moving image, and the frame frequency is decreased (for example, 60 Hz) when displaying a still image. The power consumption of the display device can be reduced by adjusting the frequency to 30 Hz or lower or 1 Hz or lower. In addition, the frame frequency of the touch sensor may be switched, and the frame frequency may be different depending on whether the touch sensor detects a touch.

In addition, in the display device of one embodiment of the present invention, the data signal rewritten in the previous period is held without rewriting the data signal in the display portion, so that one frame period of the display portion is longer than 16.7 ms. It can be a period. Therefore, as shown in FIG. 30C, one frame period of the display portion is 1 sec. (Frame frequency: 1 Hz) can be set, and one frame period of the touch sensor can be set to 16.7 ms (frame frequency: 60 Hz).

Note that the IDS driving mode described above can be referred to for a configuration in which the data signal rewritten in the previous period is held without rewriting the data signal in the display portion. Note that the IDS drive mode may be a partial IDS drive mode in which the data signal in the display unit is rewritten only in a specific area. The partial IDS drive mode is a configuration in which the data signal is rewritten only in a specific area in the display portion, and the data signal rewritten in the previous period is held in other areas.

Further, according to the touch sensor driving method disclosed in this embodiment, when the driving illustrated in FIG. 30C is performed, the touch sensor can be continuously driven. Therefore, as shown in FIG. 30D, the data signal of the display portion can be rewritten at the timing when the proximity or contact of the detection target in the touch sensor is detected.

Here, if the rewriting operation of the data signal of the display unit is performed during the sensing period of the touch sensor, noise generated during the rewriting of the data signal is transmitted to the touch sensor, which may reduce the sensitivity of the touch sensor. Therefore, it is preferable to drive so that the data signal rewriting period of the display unit is shifted from the sensing period of the touch sensor.

FIG. 31A shows an example in which rewriting of the data signal of the display portion and sensing of the touch sensor are alternately performed. FIG. 31B shows an example in which sensing of the touch sensor is performed once every time the data signal rewriting operation of the display portion is performed twice. Note that the present invention is not limited to this, and the touch sensor may be sensed once every time the rewrite operation is performed three times or more.

In addition, when an oxide semiconductor is used for a semiconductor layer in which a channel is formed in a transistor applied to the pixel pix, off-state current can be extremely reduced, and thus the frequency of data signal rewriting can be sufficiently reduced. Can do. Specifically, it is possible to provide a sufficiently long pause period after the data signal is rewritten until the next data signal is rewritten. The pause period can be, for example, 0.5 seconds or more, 1 second or more, or 5 seconds or more. The upper limit of the rest period is limited by the capacitance connected to the transistor and the leakage current of the display element, etc., and can be, for example, 1 minute or less, 10 minutes or less, 1 hour or less, or 1 day or less.

FIG. 31C shows an example in which the data signal of the display portion is rewritten at a frequency of once every 5 seconds. In FIG. 31C, the display portion has a pause period during which the rewrite operation is stopped after the rewrite of the data signal until the next rewrite operation of the data signal. In the rest period, the touch sensor can be driven at a frame frequency iHz (i is equal to or higher than the frame frequency of the display device, here 0.2 Hz or higher). In addition, as shown in FIG. 31C, it is preferable that the sensing of the touch sensor be performed during the pause period and not during the rewriting period of the data signal of the display portion, because the sensitivity of the touch sensor can be improved. In addition, as shown in FIG. 31D, when rewriting of the data signal of the display portion and sensing of the touch sensor are performed at the same time, a signal for driving can be simplified.

Further, in the idle period when the data signal rewriting operation of the display portion is not performed, not only the supply of the data signal to the display portion is stopped, but also the operation of one or both of the gate driving circuit GD and the source driving circuit SD is stopped. May be. Further, power supply to one or both of the gate drive circuit GD and the source drive circuit SD may be stopped. By doing so, noise can be further reduced and the sensitivity of the touch sensor can be further improved. In addition, power consumption of the display device can be further reduced.

When the hybrid display described above is used as the display device, the above-described IDS drive mode or partial IDS drive mode can be combined with the above-described touch sensor drive method. In the case of using a hybrid display, the plurality of display elements can independently perform the IDS drive mode or the partial IDS drive mode. When a hybrid display is used, the following driving method can be realized.

For example, when the hybrid display includes a reflective element and a self-luminous element, a black and white image is displayed on the reflective element. Thereafter, the reflective element is set to the IDS drive mode, and power supply to one or both of the gate drive circuit GD and the source drive circuit SD is stopped. Thereafter, sensing of the touch sensor is performed, and the reflective element in the area where the sensing is not performed is shifted to the partial IDS drive mode. Thereafter, the self-light emitting element in the region where the partial IDS drive mode is not performed is caused to emit light. Thereafter, the power supply to one or both of the gate drive circuit GD and the source drive circuit SD driving the self-light-emitting element is stopped, and the self-light-emitting element is shifted to the partial IDS drive mode.

By performing the driving method as described above, it is possible to realize an excellent display device in which power consumption is reduced and detection sensitivity of the touch sensor is increased.

The display device of one embodiment of the present invention has a structure in which a display portion and a touch sensor are sandwiched between two substrates. Therefore, the distance between the display unit and the touch sensor can be extremely reduced. At this time, noise at the time of driving the display unit easily propagates to the touch sensor, and the sensitivity of the touch sensor may be reduced. By applying the driving method exemplified in this embodiment, a display device having a touch sensor that achieves both reduction in thickness and high detection sensitivity can be realized.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 6)
In this embodiment, structural examples of transistors that can be used for the display device according to one embodiment of the present invention will be described with reference to FIGS.

<Configuration Example 1 of Transistor>
First, as an example of the structure of the transistor, a transistor 3200a will be described with reference to FIGS. FIG. 32A is a top view of the transistor 3200a. 32B corresponds to a cross-sectional view of a cross section taken along the dashed-dotted line X1-X2 in FIG. 32A, and FIG. 32C is between the dashed-dotted line Y1-Y2 shown in FIG. This corresponds to a cross-sectional view of the cut surface in FIG. Note that in FIG. 32A, some components (such as an insulating layer having a function of a gate insulating layer) are omitted in order to avoid complexity. In the following description, the alternate long and short dash line X1-X2 direction may be referred to as a channel length direction, and the alternate long and short dash line Y1-Y2 direction may be referred to as a channel width direction. Note that in the top view of the transistor, in the following drawings, some components may be omitted as in FIG.

The transistor 3200a includes a conductive layer 3221 over the insulating layer 3224, an insulating layer 3211 over the insulating layer 3224 and the conductive layer 3221, a metal oxide layer 3231 over the insulating layer 3211, and a conductive layer 3222a over the metal oxide layer 3231. A conductive layer 3222b over the metal oxide layer 3231, an insulating layer 3212 over the metal oxide layer 3231, a conductive layer 3222a, and a conductive layer 3222b, a conductive layer 3223 over the insulating layer 3212, an insulating layer 3212, and a conductive layer. An insulating layer 3213 over the layer 3223.

In addition, the insulating layer 3211 and the insulating layer 3212 have an opening 3235. The conductive layer 3223 is electrically connected to the conductive layer 3221 through the opening 3235.

Here, the insulating layer 3211 functions as the first gate insulating layer of the transistor 3200a, the insulating layer 3212 functions as the second gate insulating layer of the transistor 3200a, and the insulating layer 3213 includes: The transistor 3200a functions as a protective insulating layer. In the transistor 3200a, the conductive layer 3221 functions as a first gate, the conductive layer 3222a functions as one of a source and a drain, and the conductive layer 3222b serves as the other of the source and the drain. It has the function of. In the transistor 3200a, the conductive layer 3223 functions as a second gate.

Note that the transistor 3200a is a so-called channel etch transistor and has a dual-gate structure.

The transistor 3200a can be formed without the conductive layer 3223. In this case, the transistor 3200a is a so-called channel etch transistor and has a bottom gate structure.

As shown in FIGS. 32B and 32C, the metal oxide layer 3231 is positioned so as to face the conductive layer 3221 and the conductive layer 3223, and is sandwiched between conductive layers having two gate functions. . The length of the conductive layer 3223 in the channel length direction and the length of the conductive layer 3223 in the channel width direction are longer than the length of the metal oxide layer 3231 in the channel length direction and the length of the metal oxide layer 3231 in the channel width direction. Each of the metal oxide layers 3231 is covered with a conductive layer 3223 with an insulating layer 3212 interposed therebetween.

In other words, the conductive layer 3221 and the conductive layer 3223 have a region which is connected to the opening 3235 provided in the insulating layer 3211 and the insulating layer 3212 and is located outside the side end portion of the metal oxide layer 3231.

With such a structure, the metal oxide layer 3231 included in the transistor 3200a can be electrically surrounded by the electric fields of the conductive layers 3221 and 3223. A device structure of a transistor that electrically surrounds a metal oxide layer in which a channel region is formed by an electric field of a first gate and a second gate as in the transistor 3200a is called a surround channel (S-channel) structure. be able to.

Since the transistor 3200a has an S-channel structure, an electric field for inducing a channel by the conductive layer 3221 having the function of the first gate can be effectively applied to the metal oxide layer 3231. Therefore, the transistor 3200a Current driving capability is improved, and high on-current characteristics can be obtained. Further, since the on-state current can be increased, the transistor 3200a can be miniaturized. In addition, since the transistor 3200a has a structure surrounded by the conductive layer 3221 having a first gate function and the conductive layer 3223 having a second gate function, the mechanical strength of the transistor 3200a can be increased.

For example, the metal oxide layer 3231 includes In and M (M is gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, and cerium. , Neodymium, hafnium, tantalum, tungsten, or magnesium) and Zn.

The metal oxide layer 3231 preferably includes a region where the atomic ratio of In is larger than the atomic ratio of M. As an example, the ratio of the number of In, M, and Zn atoms in the metal oxide layer 3231 is preferably in the vicinity of In: M: Zn = 4: 2: 3. Here, in the vicinity, when In is 4, M is 1.5 or more and 2.5 or less, and Zn is 2 or more and 4 or less. Alternatively, the ratio of the number of In, M, and Zn atoms in the metal oxide layer 3231 is preferably in the vicinity of In: M: Zn = 5: 1: 6.

The metal oxide layer 3231 is preferably a CAC-OS or a CAC-metal oxide. The metal oxide layer 3231 has a region where the atomic ratio of In is larger than the atomic ratio of M and is a CAC-OS or a CAC-metal oxide, so that the field-effect mobility of the transistor 3200a is increased. Can do. Note that details of the CAC-OS or the CAC-metal oxide will be described later.

In addition, since the transistor 3200a having an s-channel structure has high field-effect mobility and high driving capability, the transistor 3200a is used for a driver circuit, typically a gate driver that generates a gate signal. A narrow display device (also referred to as a narrow frame) can be provided. In addition, when the transistor 3200a is used for a source driver (particularly, a demultiplexer connected to an output terminal of a shift register included in the source driver) that supplies a signal from a signal line included in the display device, the transistor 3200a is connected to the display device. A display device with a small number of wirings can be provided.

Further, since each of the transistors 3200a is a channel-etched transistor, the number of manufacturing steps is smaller than that of a transistor using low-temperature polysilicon. In addition, since the transistor 3200a uses a metal oxide layer for a channel, a laser crystallization step is not required unlike a transistor using a low-temperature polysilicon. Therefore, manufacturing cost can be reduced even in a display device using a large-area substrate. Furthermore, high resolution such as Ultra Hi-Vision (“4K resolution”, “4K2K”, “4K”), Super Hi-Vision (“8K resolution”, “8K4K”, “8K”), and transistors in large display devices Using a transistor with high field-effect mobility such as 3200a for a driver circuit and a display portion is preferable because writing in a short time can be performed and display defects can be reduced.

The insulating layer 3211 and the insulating layer 3212 in contact with the metal oxide layer 3231 are preferably oxide insulating films, and have a region containing excess oxygen (excess oxygen region) than the stoichiometric composition. Is more preferable. In other words, the insulating layer 3211 and the insulating layer 3212 are insulating films capable of releasing oxygen. Note that in order to provide an excess oxygen region in the insulating layer 3211 and the insulating layer 3212, for example, the insulating layer 3211 and the insulating layer 3212 are formed in an oxygen atmosphere, or the insulating layer 3211 and the insulating layer 3212 after film formation are oxygenated. Heat treatment may be performed in an atmosphere.

As the metal oxide layer 3231, an oxide semiconductor which is a kind of metal oxide can be used.

In the case where the metal oxide layer 3231 is an In-M-Zn oxide, the atomic ratio of the metal elements of the sputtering target used for forming the In-M-Zn oxide preferably satisfies In> M. As the atomic ratio of the metal elements of such a sputtering target, In: M: Zn = 2: 1: 3, In: M: Zn = 3: 1: 2, In: M: Zn = 4: 2: 4. 1, In: M: Zn = 5: 1: 6, In: M: Zn = 5: 1: 7, In: M: Zn = 5: 1: 8, In: M: Zn = 6: 1: 6, In: M: Zn = 5: 2: 5 etc. are mentioned.

In the case where the metal oxide layer 3231 is formed using In-M-Zn oxide, a target including polycrystalline In-M-Zn oxide is preferably used as the sputtering target. By using a target including a polycrystalline In-M-Zn oxide, the metal oxide layer 3231 having crystallinity can be easily formed. Note that the atomic ratio of the metal oxide layer 3231 to be formed includes a variation of plus or minus 40% of the atomic ratio of the metal element included in the sputtering target. For example, when the composition of the sputtering target used for the metal oxide layer 3231 is In: Ga: Zn = 4: 2: 4.1 [atomic ratio], the composition of the metal oxide layer 3231 to be formed is In: It may be in the vicinity of Ga: Zn = 4: 2: 3 [atomic ratio].

The metal oxide layer 3231 has an energy gap of 2 eV or more, preferably 2.5 eV or more. In this manner, off-state current of a transistor can be reduced by using an oxide semiconductor with a wide energy gap.

The metal oxide layer 3231 preferably has a non-single crystal structure. The non-single-crystal structure includes, for example, CAAC (C Axis Aligned Crystalline), a polycrystalline structure, a microcrystalline structure, or an amorphous structure. In a non-single crystal structure, an amorphous structure has the highest defect level density, and CAAC has the lowest defect level density.

As the metal oxide layer 3231, a metal oxide film with a low impurity concentration and a low density of defect states is preferably used because a transistor having excellent electrical characteristics can be manufactured. Here, low impurity concentration and low defect level density (low oxygen deficiency) are referred to as high purity intrinsic or substantially high purity intrinsic. Note that typical examples of impurities in the metal oxide film include water and hydrogen. In this specification and the like, reducing or removing water and hydrogen from a metal oxide film may be referred to as dehydration or dehydrogenation. In addition, the addition of oxygen to a metal oxide film or an oxide insulating film is sometimes referred to as oxygenation, and the oxygenated state includes oxygen in excess of the stoichiometric composition. In some cases, it is expressed as a state.

A metal oxide film that is highly purified intrinsic or substantially highly purified intrinsic has few carrier generation sources, and thus can have a low carrier density. Therefore, a transistor in which a channel region is formed in the metal oxide film rarely has electrical characteristics (also referred to as normally-on) in which the threshold voltage is negative. In addition, since a highly purified intrinsic or substantially highly purified intrinsic metal oxide film has a low defect level density, the trap level density may also be low. In addition, a highly pure intrinsic or substantially highly purified intrinsic metal oxide film has an extremely small off-state current, a channel width of 1 × 10 ⁶ μm, and a channel length L of 10 μm. When the voltage between the drain electrodes (drain voltage) is in the range of 1V to 10V, it is possible to obtain a characteristic that the off-current is less than the measurement limit of the semiconductor parameter analyzer, that is, 1 × 10 ⁻¹³ A or less.

The insulating layer 3213 includes one or both of hydrogen and nitrogen. Alternatively, the insulating layer 3213 includes nitrogen and silicon. The insulating layer 3213 has a function of blocking oxygen, hydrogen, water, alkali metal, alkaline earth metal, or the like. By providing the insulating layer 3213, diffusion of oxygen from the metal oxide layer 3231 to the outside, diffusion of oxygen contained in the insulating layer 3212 to the outside, hydrogen, water, and the like from the outside to the metal oxide layer 3231 Can be prevented from entering.

As the insulating layer 3213, for example, a nitride insulating film can be used. Examples of the nitride insulating film include silicon nitride, silicon nitride oxide, aluminum nitride, and aluminum nitride oxide.

<Configuration Example 2 of Transistor>
Next, as an example of the structure of the transistor, a transistor 3200b will be described with reference to FIGS. FIG. 33A is a top view of the transistor 3200b. 33B corresponds to a cross-sectional view of a cross section taken along the dashed-dotted line X1-X2 in FIG. 33A, and FIG. 33C is between the dashed-dotted line Y1-Y2 shown in FIG. This corresponds to a cross-sectional view of the cut surface in FIG.

The transistor 3200b is different from the transistor 3200a in that the metal oxide layer 3231, the conductive layer 3222a, the conductive layer 3222b, and the insulating layer 3212 have a stacked structure.

The insulating layer 3212 includes a metal oxide layer 3231, an insulating layer 3212a over the conductive layer 3222a and the conductive layer 3222b, and an insulating layer 3212b over the insulating layer 3212a. The insulating layer 3212 has a function of supplying oxygen to the metal oxide layer 3231. That is, the insulating layer 3212 contains oxygen. The insulating layer 3212a is an insulating layer that can transmit oxygen. Note that the insulating layer 3212a also functions as a damage reducing film for the metal oxide layer 3231 when an insulating layer 3212b to be formed later is formed.

As the insulating layer 3212a, silicon oxide, silicon oxynitride, or the like with a thickness of 5 nm to 150 nm, preferably 5 nm to 50 nm can be used.

The insulating layer 3212a preferably has a small amount of defects. Typically, the ESR measurement shows that the spin density of a signal appearing at g = 2.001 derived from a dangling bond of silicon is 3 × 10 ¹⁷ spins / It is preferable that it is cm ³ or less. This is because when the density of defects included in the insulating layer 3212a is large, oxygen is bonded to the defects and oxygen permeability in the insulating layer 3212a is reduced.

Note that in the insulating layer 3212a, not all oxygen that enters the insulating layer 3212a from the outside moves to the outside of the insulating layer 3212a, and some oxygen remains in the insulating layer 3212a. Further, oxygen enters the insulating layer 3212a and oxygen contained in the insulating layer 3212a moves to the outside of the insulating layer 3212a, so that oxygen may move in the insulating layer 3212a. When an oxide insulating layer that can transmit oxygen is formed as the insulating layer 3212a, oxygen released from the insulating layer 3212b provided over the insulating layer 3212a is transferred to the metal oxide layer 3231 through the insulating layer 3212a. Can be made.

The insulating layer 3212a can be formed using an oxide insulating layer having a low level density due to nitrogen oxides. Note that the level density caused by the nitrogen oxide can be formed between the energy (Ev_os) at the upper end of the valence band of the metal oxide film and the energy (Ec_os) at the lower end of the conduction band of the metal oxide film. There is a case. As the oxide insulating layer, a silicon oxynitride film with a low emission amount of nitrogen oxide, an aluminum oxynitride film with a low emission amount of nitrogen oxide, or the like can be used.

Note that a silicon oxynitride film with a small amount of released nitrogen oxide is a film having a larger amount of released ammonia than a released amount of nitrogen oxide in a thermal desorption gas analysis (TDS) method. Specifically, the released amount of ammonia is 1 × 10 ¹⁸ / cm ³ or more and 5 × 10 ¹⁹ / cm ³ or less. Note that the amount of ammonia released is the amount released by heat treatment at a film surface temperature of 50 ° C. to 650 ° C., preferably 50 ° C. to 550 ° C.

Nitrogen oxide (NO _x , x is larger than 0 and 2 or less, preferably 1 or more and 2 or less), typically NO ₂ or NO forms a level in the insulating layer 3212a or the like. The level is located in the energy gap of the metal oxide layer 3231. Therefore, when nitrogen oxide diffuses to the interface between the insulating layer 3212a and the metal oxide layer 3231, the level may trap electrons on the insulating layer 3212a side. As a result, trapped electrons remain in the vicinity of the interface between the insulating layer 3212a and the metal oxide layer 3231, so that the threshold voltage of the transistor is shifted in the positive direction.

Nitrogen oxide reacts with ammonia and oxygen in heat treatment. Since nitrogen oxide contained in the insulating layer 3212a reacts with ammonia contained in the insulating layer 3212b in the heat treatment, nitrogen oxide contained in the insulating layer 3212a is reduced. Therefore, electrons are hardly trapped at the interface between the insulating layer 3212a and the metal oxide layer 3231.

By using the oxide insulating layer as the insulating layer 3212a, a shift in threshold voltage of the transistor can be reduced, and fluctuation in electric characteristics of the transistor can be reduced.

The oxide insulating layer has a nitrogen concentration of 6 × 10 ²⁰ atoms / cm ³ or less as measured by SIMS.

By forming the oxide insulating layer using a PECVD method using silane and dinitrogen monoxide with a substrate temperature of 220 ° C. or higher and 350 ° C. or lower, a dense and high hardness film is formed. be able to.

The insulating layer 3212b is an oxide insulating layer containing more oxygen than oxygen that satisfies the stoichiometric composition. Part of oxygen is released from the oxide insulating layer by heating. Note that in TDS, the above oxide insulating layer has a region where the amount of released oxygen is 1.0 × 10 ¹⁹ atoms / cm ³ or more, preferably 3.0 × 10 ²⁰ atoms / cm ³ or more. The amount of released oxygen is the total amount when the temperature of the heat treatment in TDS is 50 ° C. or higher and 650 ° C. or lower, or 50 ° C. or higher and 550 ° C. or lower. The amount of released oxygen is the total amount in terms of oxygen atoms in TDS.

As the insulating layer 3212b, silicon oxide, silicon oxynitride, or the like with a thickness of 30 nm to 500 nm, preferably 50 nm to 400 nm can be used.

The insulating layer 3212b preferably has a small amount of defects. Typically, the ESR measurement shows that the spin density of a signal appearing at g = 2.001 derived from dangling bonds in silicon is 1.5 × 10 ^18. It is preferably less than spins / cm ³ and more preferably 1 × 10 ¹⁸ spins / cm ³ or less. Note that the insulating layer 3212b is farther from the metal oxide layer 3231 than the insulating layer 3212a, and thus may have a higher defect density than the insulating layer 3212a.

Further, since the insulating layer 3212 can be formed using the same kind of insulating layer, the interface between the insulating layer 3212a and the insulating layer 3212b may not be clearly confirmed in some cases. Therefore, in this embodiment, the interface between the insulating layer 3212a and the insulating layer 3212b is illustrated by a broken line. Note that although a two-layer structure of the insulating layer 3212a and the insulating layer 3212b has been described in this embodiment mode, the present invention is not limited thereto, and for example, a single-layer structure of the insulating layer 3212a or a stacked structure of three or more layers may be used. Good.

In the transistor 3200b, the metal oxide layer 3231 includes a metal oxide layer 3231_1 over the insulating layer 3211 and a metal oxide layer 3231_2 over the metal oxide layer 3231_1. Note that the metal oxide layer 3231_1 and the metal oxide layer 3231_2 each include the same element. For example, the metal oxide layer 3231_1 and the metal oxide layer 3231_2 preferably each independently include the element included in the above-described metal oxide layer 3231.

The metal oxide layer 3231_1 and the metal oxide layer 3231_2 preferably each independently have a region in which the atomic ratio of In is larger than the atomic ratio of M. As an example, the ratio of the number of In, M, and Zn atoms in the metal oxide layer 3231_1 and the metal oxide layer 3231_2 is preferably in the vicinity of In: M: Zn = 4: 2: 3. Here, in the vicinity, when In is 4, M is 1.5 or more and 2.5 or less, and Zn is 2 or more and 4 or less. Alternatively, the ratio of the number of In, M, and Zn atoms in the metal oxide layer 3231_1 and the metal oxide layer 3231_2 is preferably in the vicinity of In: M: Zn = 5: 1: 6. In this manner, the metal oxide layer 3231_1 and the metal oxide layer 3231_2 can be formed using the same sputtering target by using substantially the same composition; thus, manufacturing cost can be suppressed. In the case where the same sputtering target is used, the metal oxide layer 3231_1 and the metal oxide layer 3231_2 can be successively formed in a vacuum in the same chamber; therefore, the metal oxide layer 3231_1 and the metal oxide layer 3231_2 can be formed. Impurities can be prevented from being taken into the interface.

Here, the metal oxide layer 3231_1 may have a region with lower crystallinity than the metal oxide layer 3231_2. Note that the crystallinity of the metal oxide layer 3231_1 and the metal oxide layer 3231_2 can be analyzed using, for example, X-ray diffraction (XRD: X-Ray Diffraction) or a transmission electron microscope (TEM: Transmission Electron Microscope). ) Can be used for analysis.

A region where the crystallinity of the metal oxide layer 3231_1 is low serves as a diffusion path of excess oxygen, and excess oxygen can be diffused also into the metal oxide layer 3231_2 having higher crystallinity than the metal oxide layer 3231_1. In this manner, a highly reliable transistor can be provided by using a stacked structure of metal oxide layers having different crystal structures and using a region with low crystallinity as a diffusion path of excess oxygen.

In addition, since the metal oxide layer 3231_2 includes a region with higher crystallinity than the metal oxide layer 3231_1, impurities that can be mixed into the metal oxide layer 3231 can be suppressed. In particular, by increasing the crystallinity of the metal oxide layer 3231_2, damage when the conductive layers 3222a and 3222b are processed can be suppressed. The surface of the metal oxide layer 3231, that is, the surface of the metal oxide layer 3231_2 is exposed to an etchant or an etching gas used when the conductive layers 3222a and 3222b are processed. However, in the case where the metal oxide layer 3231_2 has a region with high crystallinity, the metal oxide layer 3231_2 has excellent etching resistance as compared with the metal oxide layer 3231_1 with low crystallinity. Therefore, the metal oxide layer 3231_2 functions as an etching stopper.

In addition, the metal oxide layer 3231_1 has a region with lower crystallinity than the metal oxide layer 3231_2, so that the carrier density may be increased.

Further, when the carrier density of the metal oxide layer 3231_1 is increased, the Fermi level may be relatively higher than the conduction band of the metal oxide layer 3231_1. Accordingly, the lower end of the conduction band of the metal oxide layer 3231_1 is lowered, and the energy between the lower end of the conduction band of the metal oxide layer 3231_1 and the trap level that can be formed in the gate insulating film (the insulating layer 3211 in this case). The difference may be large. When the energy difference is increased, the charge trapped in the gate insulating film is reduced, and the variation in the threshold voltage of the transistor may be reduced in some cases. Further, when the carrier density of the metal oxide layer 3231_1 is increased, the field-effect mobility of the metal oxide layer 3231 can be increased.

Note that in the transistor 3200b, the example in which the metal oxide layer 3231 has a two-layer structure is described; however, the present invention is not limited to this, and a structure in which three or more layers are stacked may be employed.

A conductive layer 3222a included in the transistor 3200b includes a conductive layer 3222a_1, a conductive layer 3222a_2 over the conductive layer 3222a_1, and a conductive layer 3222a_3 over the conductive layer 3222a_2. The conductive layer 3222b included in the transistor 3200b includes a conductive layer 3222b_1, a conductive layer 3222b_2 over the conductive layer 3222b_1, and a conductive layer 3222b_3 over the conductive layer 3222b_2.

For example, the conductive layer 3222a_1, the conductive layer 3222b_1, the conductive layer 3222a_3, and the conductive layer 3222b_3 include one or more selected from titanium, tungsten, tantalum, molybdenum, indium, gallium, tin, and zinc. It is preferable. The conductive layer 3222a_2 and the conductive layer 3222b_2 preferably include any one or more selected from copper, aluminum, and silver.

More specifically, an In—Sn oxide or an In—Zn oxide is used for the conductive layer 3222a_1, the conductive layer 3222b_1, the conductive layer 3222a_3, and the conductive layer 3222b_3, and copper is used for the conductive layer 3222a_2 and the conductive layer 3222b_2. it can.

In addition, an end portion of the conductive layer 3222a_1 has a region located outside the end portion of the conductive layer 3222a_2, and the conductive layer 3222a_3 covers a top surface and a side surface of the conductive layer 3222a_2 and is in contact with the conductive layer 3222a_1. Have. The end portion of the conductive layer 3222b_1 has a region located outside the end portion of the conductive layer 3222b_2, and the conductive layer 3222b_3 covers a top surface and side surfaces of the conductive layer 3222b_2 and is in contact with the conductive layer 3222b_1. Have.

The above structure is preferable because wiring resistance of the conductive layers 3222a and 3222b can be reduced and copper diffusion to the metal oxide layer 3231 can be suppressed.

<Configuration Example 3 of Transistor>
Next, as an example of the structure of the transistor, a transistor 3200c will be described with reference to FIGS. FIG. 34A is a top view of the transistor 3200c. 34B corresponds to a cross-sectional view of a cross-sectional surface taken along the dashed-dotted line X1-X2 illustrated in FIG. 34A, and FIG. 34C illustrates the area between the dashed-dotted line Y1-Y2 illustrated in FIG. This corresponds to a cross-sectional view of the cut surface in FIG.

A transistor 3200c illustrated in FIGS. 34A to 34C includes a conductive layer 3221 over the insulating layer 3224, an insulating layer 3211 over the conductive layer 3221, a metal oxide layer 3231 over the insulating layer 3211, a metal The insulating layer 3212 over the oxide layer 3231, the conductive layer 3223 over the insulating layer 3212, the insulating layer 3211, the metal oxide layer 3231, and the insulating layer 3213 over the conductive layer 3223 are included. Note that the metal oxide layer 3231 includes a channel region 3231 i overlapping with the conductive layer 3223, a source region 3231 s in contact with the insulating layer 3213, and a drain region 3231 d in contact with the insulating layer 3213.

The insulating layer 3213 contains nitrogen or hydrogen. When the insulating layer 3213 is in contact with the source region 3231s and the drain region 3231d, nitrogen or hydrogen in the insulating layer 3213 is added to the source region 3231s and the drain region 3231d. In the source region 3231s and the drain region 3231d, carrier density is increased by adding nitrogen or hydrogen.

The transistor 3200c includes an insulating layer 3215 over the insulating layer 3213, a conductive layer 3222a electrically connected to the source region 3231s through the insulating layer 3213 and the opening 3236a provided in the insulating layer 3215, and an insulating layer The conductive layer 3222b electrically connected to the drain region 3231d may be provided through an opening 3236b provided in the layer 3213 and the insulating layer 3215.

As the insulating layer 3215, an oxide insulating film can be used. As the insulating layer 3215, a stacked film of an oxide insulating film and a nitride insulating film can be used. As the insulating layer 3215, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, aluminum oxide, hafnium oxide, gallium oxide, Ga—Zn oxide, or the like may be used. The insulating layer 3215 is preferably a film that functions as an external barrier film such as hydrogen or water.

The insulating layer 3211 has a function as a first gate insulating film, and the insulating layer 3212 has a function as a second gate insulating film. The insulating layers 3213 and 3215 function as protective insulating films.

The insulating layer 3212 has an excess oxygen region. When the insulating layer 3212 includes the excess oxygen region, excess oxygen can be supplied to the channel region 3231i included in the metal oxide layer 3231. Accordingly, oxygen vacancies that can be formed in the channel region 3231i can be filled with excess oxygen, so that a highly reliable semiconductor device can be provided.

Note that in order to supply excess oxygen into the metal oxide layer 3231, excess oxygen may be supplied to the insulating layer 3211 formed below the metal oxide layer 3231. In this case, excess oxygen contained in the insulating layer 3211 can be supplied to the source region 3231s and the drain region 3231d included in the metal oxide layer 3231. When excess oxygen is supplied to the source region 3231s and the drain region 3231d, the resistance of the source region 3231s and the drain region 3231d may be increased.

On the other hand, with the structure in which excess oxygen is included in the insulating layer 3212 formed above the metal oxide layer 3231, excess oxygen can be selectively supplied only to the channel region 3231i. Alternatively, after supplying excess oxygen to the channel region 3231i, the source region 3231s, and the drain region 3231d, the carrier density of the source region 3231s and the drain region 3231d is selectively increased, so that the source region 3231s and the drain region 3231d It can suppress that resistance becomes high.

The source region 3231s and the drain region 3231d included in the metal oxide layer 3231 preferably each include an element that forms oxygen vacancies or an element that combines with oxygen vacancies. As an element that forms oxygen vacancies or an element that combines with oxygen vacancies, typically, hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, chlorine, titanium, a rare gas, or the like can be given. Typical examples of rare gas elements include helium, neon, argon, krypton, and xenon. In the case where one or more of the elements that form oxygen vacancies are included in the insulating layer 3213, the insulating layer 3213 diffuses from the insulating layer 3213 to the source region 3231s and the drain region 3231d, and / or the source region 3231s by the impurity addition treatment It is added into the drain region 3231d.

When the impurity element is added to the oxide semiconductor film, the bond between the metal element and oxygen in the oxide semiconductor film is cut, so that an oxygen vacancy is formed. Alternatively, when an impurity element is added to the oxide semiconductor film, oxygen bonded to the metal element in the oxide semiconductor film is bonded to the impurity element, so that oxygen is released from the metal element and oxygen vacancies are formed. The As a result, the carrier density in the oxide semiconductor film is increased and the conductivity is increased.

The conductive layer 3221 has a function as a first gate electrode, the conductive layer 3223 has a function as a second gate electrode, the conductive layer 3222a has a function as a source electrode, The conductive layer 3222b functions as a drain electrode.

As shown in FIG. 34C, the insulating layer 3211 and the insulating layer 3212 are provided with openings 3237. In addition, the conductive layer 3221 is electrically connected to the conductive layer 3223 through the opening 3237. Therefore, the same potential is applied to the conductive layer 3221 and the conductive layer 3223. Note that different potentials may be applied to the conductive layer 3221 and the conductive layer 3223 without providing the opening 3237. Alternatively, the conductive layer 3221 may be used as the light-blocking film without providing the opening 3237. For example, when the conductive layer 3221 is formed using a light-blocking material, light from below irradiated to the channel region 3231i can be suppressed.

As shown in FIGS. 34B and 34C, the metal oxide layer 3231 is opposite to the conductive layer 3221 functioning as the first gate electrode and the conductive layer 3223 functioning as the second gate electrode. And is sandwiched between conductive films functioning as two gate electrodes.

The transistor 3200c has an S-channel structure similarly to the transistors 3200a and 3200b. With such a structure, the metal oxide layer 3231 included in the transistor 3200c is electrically converted by an electric field of the conductive layer 3221 functioning as the first gate electrode and the conductive layer 3223 functioning as the second gate electrode. Can be surrounded.

Since the transistor 3200c has an S-channel structure, an electric field for inducing a channel by the conductive layer 3221 or the conductive layer 3223 can be effectively applied to the metal oxide layer 3231; thus, the current driving capability of the transistor 3200c Thus, high on-current characteristics can be obtained. In addition, since the on-state current can be increased, the transistor 3200c can be miniaturized. In addition, since the transistor 3200c has a structure surrounded by the conductive layer 3221 and the conductive layer 3223, the mechanical strength of the transistor 3200c can be increased.

Note that the transistor 3200c may be referred to as a TGSA (Top Gate Self Align) FET because of the position of the conductive layer 3223 with respect to the metal oxide layer 3231 or the formation method of the conductive layer 3223.

Note that the transistor 3200c may have a structure in which two or more metal oxide layers 3231 are stacked as in the transistor 3200b.

In the transistor 3200c, the insulating layer 3212 is provided only in a portion overlapping with the conductive layer 3223; however, the present invention is not limited to this, and the insulating layer 3212 can cover the metal oxide layer 3231. Alternatively, the conductive layer 3221 may be omitted.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 7)
<Configuration of CAC-OS>
A structure of a CAC-OS that can be used for the transistor disclosed in one embodiment of the present invention is described below.

In this specification and the like, a metal oxide is a metal oxide in a broad expression. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as oxide semiconductors or simply OS), and the like. For example, when a metal oxide is used for an active layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. That is, in the case of describing as an OS FET, it can be said to be a transistor including a metal oxide or an oxide semiconductor.

In this specification, in the case where a metal oxide has a mixture of a region having a function of a conductor and a region having a function of a dielectric, and the whole metal oxide functions as a semiconductor, a CAC-OS or a CAC-metal It is defined as “oxide”.

In other words, the CAC-OS is one structure of a material in which an element included in an oxide semiconductor is unevenly distributed with a size of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm, or the vicinity thereof. . Note that in the following, in an oxide semiconductor, one or more elements are unevenly distributed, and a region including the element has a size of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm, or the vicinity thereof. The state mixed with is also referred to as a mosaic or patch.

The physical characteristics of a region where a specific element is unevenly distributed are determined by the properties of the element. For example, a region in which elements that tend to become insulators are relatively uneven among the elements constituting the metal oxide is a dielectric region. On the other hand, a region in which elements that tend to be conductors are relatively uneven among the elements constituting the metal oxide is a conductor region. In addition, when the conductor region and the dielectric region are mixed in a mosaic, the material functions as a semiconductor.

That is, the metal oxide in one embodiment of the present invention is a kind of matrix composite or metal matrix composite in which materials having different physical characteristics are mixed.

Note that the oxide semiconductor preferably contains at least indium. In particular, it is preferable to contain indium and zinc. In addition to them, element M (M is gallium, aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum. , One or more selected from tungsten, magnesium, or the like.

For example, a CAC-OS in In-Ga-Zn oxide (In-Ga-Zn oxide among CAC-OSs may be referred to as CAC-IGZO in particular) is an indium oxide (hereinafter referred to as InO). _X1 (X1 is greater real than 0) and.), or indium zinc oxide _{(hereinafter, in X2 Zn Y2 O Z2 (} X2, Y2, and Z2 is larger real than 0) and a.), gallium An oxide (hereinafter referred to as GaO _X3 (X3 is a real number greater than 0)) or a gallium zinc oxide (hereinafter referred to as Ga _X4 Zn _Y4 O _Z4 (where X4, Y4, and Z4 are greater than 0)) to.) and the like, the material becomes mosaic by separate into, mosaic _{InO X1} or _in X2 _Zn Y2 _{O Z2,} is a configuration in which uniformly distributed in the film (hereinafter Also referred to as a cloud-like.) A.

That, CAC-OS includes a region _{GaO X3} is the main _component, and In _{X2 Zn} Y2 _{O Z2,} or _{InO X1} is the main component region is a composite oxide semiconductor having a structure that is mixed. Note that in this specification, for example, the first region indicates that the atomic ratio of In to the element M in the first region is larger than the atomic ratio of In to the element M in the second region. It is assumed that the concentration of In is higher than that in the second region.

Note that IGZO is a common name and may refer to one compound of In, Ga, Zn, and O. As a typical example, InGaO ₃ (ZnO) _m1 (m1 is a natural number) or In _{(1 + x0)} Ga _(1-x0) O ₃ (ZnO) _m0 (−1 ≦ x0 ≦ 1, m0 is an arbitrary number) A crystalline compound may be mentioned.

The crystalline compound has a single crystal structure, a polycrystalline structure, or a CAAC structure. The CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have c-axis orientation and are connected without being oriented in the ab plane.

On the other hand, CAC-OS relates to a material structure of an oxide semiconductor. CAC-OS refers to a nanoparticulate region mainly composed of Ga and partly composed of In, in a material configuration containing In, Ga, Zn, and O. Are observed, each of which is randomly dispersed in a mosaic pattern. Therefore, in the CAC-OS, the crystal structure is a secondary element.

Note that the CAC-OS does not include a stacked structure of two or more kinds of films having different compositions. For example, a structure composed of two layers of a film mainly containing In and a film mainly containing Ga is not included.

Incidentally, a region _{GaO X3} is the main _component, and In _{X2 Zn} Y2 _{O Z2} or _{InO X1} is the main component region, in some cases clear boundary can not be observed.

In addition, instead of gallium, aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium are selected. In the case where one or a plurality of types are included, in the CAC-OS, a nanoparticulate region mainly containing the element is observed in part, and a nanoparticulate region mainly containing In is partly observed. Are observed, each of which is randomly dispersed in a mosaic pattern.

<Analysis of CAC-OS>
Subsequently, the results of measurement of an oxide semiconductor film formed on a substrate using various measurement methods will be described.

[Sample structure and production method]
In the following, nine samples according to one embodiment of the present invention are described. Each sample is manufactured under different conditions for the substrate temperature and the oxygen gas flow rate when the oxide semiconductor film is formed. Note that the sample has a structure including a substrate and an oxide semiconductor over the substrate.

A method for manufacturing each sample will be described.

First, a glass substrate is used as the substrate. Subsequently, an In—Ga—Zn oxide with a thickness of 100 nm is formed as an oxide semiconductor over the glass substrate with a sputtering apparatus. The deposition conditions are such that the pressure in the chamber is 0.6 Pa and an oxide target (In: Ga: Zn = 4: 2: 4.1 [atomic ratio]) is used as the target. In addition, 2500 W AC power is supplied to the oxide target installed in the sputtering apparatus.

Note that the substrate temperature was set to a temperature at which the substrate was not intentionally heated (hereinafter also referred to as room temperature or RT), 130 ° C., or 170 ° C. as a condition for forming the oxide film. In addition, nine samples are manufactured by setting the flow rate ratio of oxygen gas to the mixed gas of Ar and oxygen (hereinafter also referred to as oxygen gas flow rate ratio) to 10%, 30%, or 100%.

[Analysis by X-ray diffraction]
In this item, the results of X-ray diffraction (XRD) measurement on nine samples will be described. Note that Bruker D8 ADVANCE was used as the XRD apparatus. The condition is that the scanning range is 15 deg. In θ / 2θ scanning by the out-of-plane method. To 50 deg. , The step width is 0.02 deg. The scanning speed is 3.0 deg. / Min.

FIG. 35 shows the results of measuring the XRD spectrum using the out-of-plane method. In FIG. 35, the upper part shows the measurement results for the sample whose substrate temperature condition during film formation is 170 ° C., the middle part shows the measurement results for the sample whose substrate temperature condition during film formation is 130 ° C., and the lower part shows the measurement result during film formation. The substrate temperature condition of R.R. T.A. The measurement result in the sample is shown. The left column shows the measurement results for the sample with an oxygen gas flow ratio of 10%, the center column shows the measurement results for a sample with an oxygen gas flow ratio of 30%, and the right column shows the oxygen gas flow rate. The measurement result in the sample whose ratio condition is 100% is shown.

In the XRD spectrum shown in FIG. 35, the peak intensity in the vicinity of 2θ = 31 ° is increased by increasing the substrate temperature during film formation or increasing the ratio of the oxygen gas flow rate ratio during film formation. Note that the peak near 2θ = 31 ° is a crystalline IGZO compound (also referred to as CAAC (c-axis aligned crystalline) -IGZO) oriented in the c-axis with respect to a surface to be formed or an upper surface substantially perpendicular to the surface. Is known to originate from

In the XRD spectrum shown in FIG. 35, a clear peak did not appear as the substrate temperature during film formation was lower or the oxygen gas flow rate ratio was smaller. Therefore, it can be seen that the sample having a low substrate temperature during film formation or a small oxygen gas flow ratio does not show orientation in the ab plane direction and c-axis direction of the measurement region.

[Analysis by electron microscope]
In this item, the substrate temperature R.D. T.A. Samples prepared at a gas flow rate ratio of 10% and HAADF (High-Angle Angular Dark Field) -STEM (Scanning Transmission Electron Microscope) will be described and explained below (hereinafter obtained by HAADF-STEM). The image is also called a TEM image.)

The results of image analysis of a planar image (hereinafter also referred to as a planar TEM image) acquired by HAADF-STEM and a sectional image (hereinafter also referred to as a sectional TEM image) will be described. The TEM image was observed using a spherical aberration correction function. The HAADF-STEM image was taken by irradiating an electron beam with an acceleration voltage of 200 kV and a beam diameter of about 0.1 nmφ using an atomic resolution analytical electron microscope JEM-ARM200F manufactured by JEOL Ltd.

FIG. 36A shows the substrate temperature R.D. T.A. , And a plane TEM image of a sample fabricated at an oxygen gas flow rate ratio of 10%. FIG. 36B shows the substrate temperature R.P. T.A. And a cross-sectional TEM image of a sample manufactured at an oxygen gas flow rate ratio of 10%.

[Analysis of electron diffraction pattern]
In this item, the substrate temperature R.D. T.A. The result of acquiring an electron beam diffraction pattern by irradiating an electron beam having a probe diameter of 1 nm (also referred to as a nanobeam electron beam) to a sample manufactured at an oxygen gas flow rate ratio of 10% will be described.

As shown in FIG. T.A. , And an electron beam diffraction pattern indicated by black spots a1, black spots a2, black spots a3, black spots a4, and black spots a5 in a planar TEM image of a sample prepared at an oxygen gas flow rate ratio of 10%. The observation of the electron beam diffraction pattern is performed while moving at a constant speed from the 0 second position to the 35 second position while irradiating the electron beam. FIG. 36C shows the result of the black point a1, FIG. 36D shows the result of the black point a2, FIG. 36E shows the result of the black point a3, FIG. 36F shows the result of the black point a4, and FIG. As shown in FIG.

From FIG. 36C, FIG. 36D, FIG. 36E, FIG. 36F, and FIG. 36G, a high-luminance region can be observed in a circle (in a ring shape). A plurality of spots can be observed in the ring-shaped region.

In addition, as shown in FIG. T.A. In the cross-sectional TEM image of the sample manufactured at an oxygen gas flow rate ratio of 10%, the electron beam diffraction pattern indicated by black spot b1, black spot b2, black spot b3, black spot b4, and black spot b5 is observed. FIG. 36 (H) shows the result of black point b1, FIG. 36 (I) shows the result of black point b2, FIG. 36 (J) shows the result of black point b3, FIG. 36 (K) shows the result of black point b4, and FIG. As shown in FIG.

From FIG. 36 (H), FIG. 36 (I), FIG. 36 (J), FIG. 36 (K), and FIG. 36 (L), a region with high luminance can be observed in a ring shape. A plurality of spots can be observed in the ring-shaped region.

Here, for example, when an electron beam with a probe diameter of 300 nm is incident on a CAAC-OS having an InGaZnO ₄ crystal in parallel to the sample surface, spots resulting from the (009) plane of the InGaZnO ₄ crystal are included. A diffraction pattern is seen. That is, it can be seen that the CAAC-OS has c-axis orientation and the c-axis is in a direction substantially perpendicular to the formation surface or the top surface. On the other hand, when an electron beam with a probe diameter of 300 nm is incident on the same sample perpendicularly to the sample surface, a ring-shaped diffraction pattern is confirmed. That is, in the CAAC-OS, the a-axis and the b-axis do not have orientation.

Further, when electron beam diffraction using an electron beam with a large probe diameter (for example, 50 nm or more) is performed on an oxide semiconductor having microcrystals (hereinafter referred to as nc-OS), a halo pattern is obtained. A simple diffraction pattern is observed. Further, when nanobeam electron diffraction is performed on the nc-OS using an electron beam with a small probe diameter (for example, less than 50 nm), bright spots (spots) are observed. Further, when nanobeam electron diffraction is performed on the nc-OS, a region with high luminance may be observed so as to draw a circle (in a ring shape). In addition, a plurality of bright spots may be observed in the ring-shaped region.

Substrate temperature R.D. T.A. The electron beam diffraction pattern of a sample manufactured at an oxygen gas flow rate ratio of 10% has a ring-like high luminance region and a plurality of bright spots in the ring region. Therefore, the substrate temperature R.D. T.A. And the sample manufactured at an oxygen gas flow rate ratio of 10% has an electron beam diffraction pattern of nc-OS and has no orientation in the plane direction and the cross-sectional direction.

As described above, an oxide semiconductor with a low substrate temperature or a low oxygen gas flow ratio during deposition has properties that are clearly different from those of an amorphous oxide semiconductor film and a single crystal oxide semiconductor film. Can be estimated.

[Elemental analysis]
In this item, by using energy dispersive X-ray spectroscopy (EDX) and obtaining and evaluating EDX mapping, the substrate temperature R.D. T.A. The results of elemental analysis of a sample prepared at an oxygen gas flow rate ratio of 10% will be described. For EDX measurement, an energy dispersive X-ray analyzer JED-2300T manufactured by JEOL Ltd. is used as an element analyzer. A Si drift detector is used to detect X-rays emitted from the sample.

In the EDX measurement, each point in the analysis target region of the sample is irradiated with an electron beam, and the characteristic X-ray energy and the number of occurrences of the sample generated thereby are measured to obtain an EDX spectrum corresponding to each point. In this embodiment, the peak of the EDX spectrum at each point is represented by the electron transition from the In atom to the L shell, the electron transition from the Ga atom to the K shell, the electron transition from the Zn atom to the K shell, and the K shell from the O atom. And the ratio of each atom at each point is calculated. By performing this for the analysis target region of the sample, EDX mapping showing the distribution of the ratio of each atom can be obtained.

FIG. 37 shows the substrate temperature R.D. T.A. And EDX mapping in a cross section of a sample fabricated at an oxygen gas flow rate ratio of 10%. FIG. 37A is an EDX mapping of Ga atoms (the ratio of Ga atoms to all atoms is in the range of 1.18 to 18.64 [atomic%]). FIG. 37B is an EDX mapping of In atoms (the ratio of In atoms to all atoms is in the range of 9.28 to 33.74 [atomic%]). FIG. 37C is an EDX mapping of Zn atoms (the ratio of Zn atoms to all atoms is in the range of 6.69 to 24.99 [atomic%]). 37A, 37B, and 37C show the substrate temperature R.D. during film formation. T.A. In a cross section of a sample manufactured at an oxygen gas flow rate ratio of 10%, a region in the same range is shown. Note that the EDX mapping shows the ratio of elements in light and dark so that the more measurement elements in the range, the brighter the brightness, and the darker the measurement elements. Also, the magnification of EDX mapping shown in FIG. 37 is 7.2 million times.

In the EDX mapping shown in FIGS. 37A, 37B, and 37C, a relative light / dark distribution is seen in the image, and the substrate temperature R.D. T.A. In the sample prepared at an oxygen gas flow rate ratio of 10%, it can be confirmed that each atom exists in a distributed manner. Here, attention is focused on a range surrounded by a solid line and a range surrounded by a broken line shown in FIGS. 37 (A), 37 (B), and 37 (C).

In FIG. 37A, a range surrounded by a solid line includes many relatively dark regions, and a range surrounded by a broken line includes many relatively bright regions. In FIG. 37B, a range surrounded by a solid line includes many relatively bright areas, and a range surrounded by a broken line includes many relatively dark areas.

That is, the range surrounded by the solid line is a region having a relatively large number of In atoms, and the range surrounded by a broken line is a region having a relatively small number of In atoms. Here, in FIG. 37C, in the range surrounded by the solid line, the right side is a relatively bright area and the left side is a relatively dark area. Therefore, the range surrounded by the solid line is a region mainly composed of In _X2 Zn _Y2 O _Z2 or InO _X1 .

A range surrounded by a solid line is a region with relatively few Ga atoms, and a range surrounded by a broken line is a region with relatively many Ga atoms. In FIG. 37C, in the range surrounded by the broken line, the upper left region is a relatively bright region, and the lower right region is a relatively dark region. Therefore, the range surrounded by the broken line is a region whose main component is GaO _X3 , Ga _X4 Zn _Y4 O _Z4 , or the like.

In addition, from FIGS. 37A, 37B, and 37C, the distribution of In atoms is relatively more uniform than Ga atoms, and InO _X1 is the main component. The regions appear to be connected to each other through a region mainly composed of In _X2 Zn _Y2 O _Z2 . As described above, the region mainly composed of In _X2 Zn _Y2 O _Z2 or InO _X1 is formed so as to spread in a cloud shape.

Thus, the region which is the main component such as _{GaO X3, In X2 Zn Y2 O} Z2 or _{InO X1} there is a region which is a main component, ubiquitously, an In-Ga-Zn oxide having a mixed to have the structure Things can be referred to as CAC-OS.

The crystal structure in the CAC-OS has an nc structure. The nc structure of CAC-OS has several bright spots (spots) in addition to bright spots (spots) caused by IGZO including single crystal, polycrystal, or CAAC structure in the electron diffraction pattern. Have. Alternatively, in addition to several bright spots (spots), a crystal structure is defined as a region having a high brightness in a ring shape.

Further, FIG. 37 (A), FIG. 37 (B), and 37 from (C), such as _{GaO X3} is the main component area, and _In X2 _Zn Y2 _{O Z2} or _{InO X1} is a region which is the main component, The size is observed from 0.5 nm to 10 nm, or from 1 nm to 3 nm. Preferably, in EDX mapping, the diameter of a region in which each element is a main component is 1 nm or more and 2 nm or less.

As described above, the CAC-OS has a structure different from that of the IGZO compound in which the metal elements are uniformly distributed and has properties different from those of the IGZO compound. That is, in the CAC-OS, a region in which GaO _X3 or the like is a main component and a region in which In _X2 Zn _Y2 O _Z2 or InO _X1 is a main component are phase-separated from each other, and a region in which each element is a main component. Has a mosaic structure.

Here, the region containing In _X2 Zn _Y2 O _Z2 or InO _X1 as a main component is a region having higher conductivity than a region containing GaO _X3 or the like as a main component. _That, In _{X2 Zn} Y2 _{O Z2} or _{InO X1,} is an area which is the main component, by carriers flow, expressed the conductivity of the oxide semiconductor. Accordingly, a region where In _X2 Zn _Y2 O _Z2 or InO _X1 is a main component is distributed in a cloud shape in the oxide semiconductor, whereby high field-effect mobility (μ) can be realized.

On the other hand, areas such as _{GaO X3} is the main _component, as compared to the In _{X2 Zn} Y2 _{O Z2} or _{InO X1} is the main component area, it is highly regions insulating. That is, a region containing GaO _X3 or the like as a main component is distributed in the oxide semiconductor, whereby leakage current can be suppressed and good switching operation can be realized.

Therefore, when CAC-OS is used for a semiconductor element, the insulating property caused by GaO _{X3 and the} like and the conductivity caused by In _X2 Zn _Y2 O _Z2 or InO _X1 act in a complementary manner, resulting in high An on-current (I _on ) and high field effect mobility (μ) can be realized.

In addition, a semiconductor element using a CAC-OS has high reliability. Therefore, the CAC-OS is optimal for various semiconductor devices including a display.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

(Embodiment 8)
In this embodiment, examples of electronic devices using the display device and the like disclosed in this specification and the like will be described.

As an electronic device using a semiconductor device according to one embodiment of the present invention, a display device such as a television or a monitor, a lighting device, a desktop or laptop personal computer, a word processor, or a DVD (Digital Versatile Disc) is stored in a recording medium Playback device for playing back still images or moving images, portable CD player, radio, tape recorder, headphone stereo, stereo, table clock, wall clock, cordless telephone cordless handset, transceiver, car phone, mobile phone, personal digital assistant, tablet High-frequency heating of fixed terminals such as portable terminals, portable game machines, pachinko machines, calculators, electronic notebooks, electronic book terminals, electronic translators, voice input devices, video cameras, digital still cameras, electric shavers, microwave ovens, etc. Equipment, electric rice cooker, electric Air washing machine, electric vacuum cleaner, water heater, electric fan, hair dryer, air conditioner, humidifier, dehumidifier, etc., dishwasher, dish dryer, clothes dryer, futon dryer, electric refrigerator, electric freezer , Electric refrigerator-freezers, DNA storage freezers, flashlights, tools such as chainsaws, medical devices such as smoke detectors and dialysis machines. Further examples include industrial equipment such as guide lights, traffic lights, belt conveyors, elevators, escalators, industrial robots, power storage systems, power storage devices for power leveling and smart grids. In addition, an engine using fuel, a moving body driven by an electric motor using electric power from a power storage body, and the like may be included in the category of electronic devices. Examples of the moving body include an electric vehicle (EV), a hybrid vehicle (HEV) having both an internal combustion engine and an electric motor, a plug-in hybrid vehicle (PHEV), a tracked vehicle in which these tire wheels are changed to an endless track, and electric assist. Examples include motorbikes including bicycles, motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft, rockets, artificial satellites, space probes, planetary probes, and space ships.

An information terminal 2910 illustrated in FIG. 38A includes a housing 2911, a display portion 2912, a microphone 2917, a speaker portion 2914, a camera 2913, an external connection portion 2916, an operation switch 2915, and the like. The display portion 2912 includes a display panel using a flexible substrate and a touch screen. In addition, the information terminal 2910 includes an antenna, a battery, and the like inside the housing 2911. The information terminal 2910 can be used as, for example, a smartphone, a mobile phone, a tablet information terminal, a tablet personal computer, an electronic book terminal, or the like.

A laptop personal computer 2920 illustrated in FIG. 38B includes a housing 2921, a display portion 2922, a keyboard 2923, a pointing device 2924, and the like. The laptop personal computer 2920 includes an antenna, a battery, and the like inside the housing 2921.

A video camera 2940 illustrated in FIG. 38C includes a housing 2941, a housing 2942, a display portion 2944, operation switches 2944, a lens 2945, a connection portion 2946, and the like. The operation switch 2944 and the lens 2945 are provided on the housing 2941, and the display portion 2944 is provided on the housing 2942. In addition, the video camera 2940 includes an antenna, a battery, and the like inside the housing 2941. The housing 2941 and the housing 2942 are connected to each other by a connection portion 2946. The angle between the housing 2941 and the housing 2942 can be changed by the connection portion 2946. Depending on the angle of the housing 2942 with respect to the housing 2941, the orientation of the image displayed on the display portion 2943 can be changed, and display / non-display of the image can be switched.

FIG. 38D illustrates an example of a bangle information terminal. The information terminal 2950 includes a housing 2951, a display portion 2952, and the like. In addition, an antenna, a battery, and the like are provided inside the information terminal 2950 and the housing 2951. The display portion 2952 is supported by a housing 2951 having a curved surface. Since the display portion 2952 includes a display panel using a flexible substrate, an information terminal 2950 that is flexible, light, and easy to use can be provided.

FIG. 38E illustrates an example of a wristwatch type information terminal. The information terminal 2960 includes a housing 2961, a display portion 2962, a band 2963, a buckle 2964, an operation switch 2965, an input / output terminal 2966, and the like. Further, an antenna, a battery, and the like are provided inside the information terminal 2960 and the housing 2961. The information terminal 2960 can execute various applications such as mobile phone, e-mail, text browsing and creation, music playback, Internet communication, and computer games.

The display surface of the display portion 2962 is curved, and display can be performed along the curved display surface. The display portion 2962 includes a touch sensor and can be operated by touching the screen with a finger, a stylus, or the like. For example, an application can be started by touching an icon 2967 displayed on the display unit 2962. The operation switch 2965 can have various functions such as time setting, power on / off operation, wireless communication on / off operation, manner mode execution and release, and power saving mode execution and release. . For example, the function of the operation switch 2965 can be set by an operating system incorporated in the information terminal 2960.

In addition, the information terminal 2960 can execute short-range wireless communication that is a communication standard. For example, it is possible to talk hands-free by communicating with a headset capable of wireless communication. Further, the information terminal 2960 includes an input / output terminal 2966, and can directly exchange data with other information terminals. Charging can also be performed via the input / output terminal 2966. Note that the charging operation may be performed by wireless power feeding without using the input / output terminal 2966.

FIG. 38F illustrates a tablet personal computer 5300, which includes a housing 5301, a housing 5302, a display portion 5303, an optical sensor 5304, an optical sensor 5305, a switch 5306, and the like. The display portion 5303 is supported by a housing 5301 and a housing 5302. Since the display portion 5303 is formed using a flexible substrate, the display portion 5303 has a function of flexibly bending the shape. By changing the angle between the housing 5301 and the housing 5302 at the hinges 5307 and 5308, the display portion 5303 can be folded so that the housing 5301 and the housing 5302 overlap with each other. Although not shown, an open / close sensor may be incorporated, and the change in the angle may be used as information on the use condition in the display portion 5303.

FIG. 38G is a perspective view illustrating the television device 9100. A television device 9100 includes a housing 9000, a display portion 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), a connection terminal 9006, a sensor 9007 (a function of measuring distance, light, temperature, and the like). 1), a microphone 9008, and the like. The television device 9100 can incorporate a display device of, for example, 50 inches or more, or 100 inches or more into the display portion 9001.

The display device of one embodiment of the present invention is mounted on the display portion of the electronic device described in this embodiment. By using the display device and the driving method according to one embodiment of the present invention for the display portion of the electronic device, an electronic device with favorable visibility can be realized.

This embodiment can be implemented in appropriate combination with the structures described in the other embodiments.

DESCRIPTION OF SYMBOLS 100 Display apparatus 110 Display apparatus 112 Liquid crystal 113 Electrode 117 Insulating layer 121 Insulating layer 131 Colored layer 132 Light shielding layer 134 Colored layer 135 Functional member 141 Adhesive layer 142 Adhesive layer 170 Light emitting element 171 Opposite substrate 176 Touch sensor 180 Liquid crystal element 181 Transistor substrate 191 Conductive layer 192 EL layer 193 Conductive layer 194 Insulating layer 201 Transistor 203 Transistor 204 Connection portion 205 Transistor 206 Transistor 207 Connection portion

Claims (14)

A display device having a liquid crystal element, a light emitting element, and a transistor,
The transistor is provided between the liquid crystal element and the light emitting element,
The liquid crystal element is
A first electrode, a second electrode, and a liquid crystal layer;
The light emitting element is
A third electrode, a fourth electrode, and an organic layer;
The first electrode and the second electrode have a region that transmits visible light,
One of the third electrode or the fourth electrode has a region that reflects visible light,
Light emitted from the light emitting element passes through the liquid crystal element and is extracted to the outside.
One of the third electrode or the fourth electrode is
Reflects external light incident through the liquid crystal element,
The display device is a bottom-gate transistor. In claim 1,
A display device in which at least one of a gate electrode, a source electrode, a drain electrode, and a semiconductor layer included in the transistor has a region transmitting visible light. In claim 1 or claim 2,
A display device in which light emitted from the light emitting element is extracted to the outside through the transistor and the liquid crystal element. In any one of Claims 1 thru | or 3,
Having a capacitive element,
The capacitive element is provided between the liquid crystal element and the light emitting element,
The capacitive element is a display device having a region that transmits visible light. In claim 4,
A display device in which light emitted from the light emitting element is extracted to the outside through the capacitive element and the liquid crystal element. In any one of Claims 1 thru | or 5,
The other of the third electrode or the fourth electrode has a region sandwiched between one electrode and a liquid crystal element. In any one of Claims 1 thru | or 6,
The liquid crystal element is a display device that operates in a VA-IPS mode. In any one of Claims 1 thru | or 8,
The display device in which the organic layer is an EL layer. A display area and a peripheral circuit area;
The display region includes a first transistor, a liquid crystal element, and a light emitting element.
The peripheral circuit region includes a second transistor,
The liquid crystal element and the light emitting element are:
A region overlapping each other via the first transistor;
At least one of the gate electrode, the source electrode, and the drain electrode included in the first transistor has a region that transmits visible light,
The gate electrode, the source electrode, and the drain electrode of the second transistor have a region that blocks visible light,
One or both of the first transistor and the second transistor is a bottom-gate display device. In claim 9,
The gate electrode of the first transistor is made of a metal oxide,
A display device in which a gate electrode of the second transistor is made of metal. In any one of Claim 9 or Claim 10,
The light emitted from the light emitting element is
A display device which is taken out through the first transistor and the liquid crystal element. In any one of Claim 9 thru | or Claim 11,
The light-emitting element includes a first electrode, a second electrode, and an organic layer,
The organic layer is sandwiched between the first electrode and the second electrode,
One of the first electrode or the second electrode has a region that reflects visible light,
One of the first electrode or the second electrode is
A display device that reflects external light incident through the liquid crystal element. In any one of claims 9 to 14,
The liquid crystal element is a display device that operates in a VA-IPS mode. In any one of claims 9 to 13,
The display device, wherein the light emitting element is an EL element.