Patent Application
20230014360
One embodiment of the present invention relates to electronic devices.
Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention disclosed in this specification and the like include a semiconductor device, a display device, a light-emitting apparatus, a power storage device, a memory device, an electronic device, a lighting device, an input device, an input/output device, a driving method thereof, and a manufacturing method thereof. A semiconductor device refers to a device that can function by utilizing semiconductor characteristics in general.
As display devices for augmented reality (AR) or virtual reality (VR), wearable display devices and stationary display devices are becoming widespread. Examples of wearable display devices include a head mounted display (HMD) and an eyeglass-type display device. Examples of stationary display devices include a head-up display (HUD).
A technique which obtains information of a body motion or a facial expression of a user with use of a sensor, a camera, or the like provided on a head-mounted display and displays the information has been considered. Patent Document 1 and Patent Document 2 each disclose a structure in which a camera is provided in a head-mounted display to recognize a facial expression of a user.
In the case where an electronic device is provided with a detection device to obtain information on a user's emotion, and the detection device is apart from the user, the detection accuracy is decreased and the emotion of the user is unlikely to be detected with a high accuracy. In addition, when the detection device is protruded from the housing of the electronic device, the reliability of the electronic device might be decreased.
An object of one embodiment of the present invention is to provide an electronic device capable of recognizing a user's emotion with a high accuracy. Another object of one embodiment of the present invention is to provide an electronic device capable of estimating the kind or the degree of a user's emotion with a high accuracy. Another object of one embodiment of the present invention is to provide a highly reliable electronic device. Another object of one embodiment of the present invention is to provide a novel electronic device.
Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not need to achieve all the objects listed above. Note that other objects can be derived from the description of the specification, the drawings, the claims, and the like.
One embodiment of the present invention is an electronic device including a detection device, an arithmetic device, and a housing. The housing includes a space at a position overlapping with a user's nose when the user wears the electronic device. The detection device is located between the housing and the user's nose. The detection device has a function of obtaining user's data on an emotion of the user and outputting the user's data to the arithmetic device. The arithmetic device has a function of generating display data based on the user's data and outputting the display data.
One embodiment of the present invention is an electronic device including a detection device, an arithmetic device, and a housing. The housing includes a space at a position overlapping with a user's nose when the user wears the electronic device. The detection device is located in the inside of the housing to overlap with the user's nose. The detection device has a function of obtaining user's data on an emotion of the user and outputting the user's data to the arithmetic device. The arithmetic device has a function of generating display data based on the user's data and outputting the display data.
One embodiment of the present invention is an electronic device including a detection device, an arithmetic device, a display device, and a housing. The housing includes a space at a position overlapping with a user's nose when the user wears the electronic device. The detection device is located between the housing and the user's nose. The detection device has a function of obtaining user's data on an emotion of the user and outputting the user's data to the arithmetic device. The arithmetic device has a function of generating display data based on the user's data and outputting the display data to the display device.
One embodiment of the present invention is an electronic device including a detection device, an arithmetic device, a display device, and a housing. The housing includes a space at a position overlapping with a user's nose when the user wears the electronic device. The detection device is located in the inside of the housing to overlap with the user's nose. The detection device has a function of obtaining user's data on an emotion of the user and outputting the user's data to the arithmetic device. The arithmetic device has a function of generating display data based on the user's data and outputting the display data to the display device.
In the above-described electronic devices, the detection device preferably includes one or more of a temperature sensor, a humidity sensor, a microphone, and an imaging device.
In the above-described electronic devices, the user's data is preferably one or more of a temperature, a humidity, a sound, and an image.
The above-described electronic devices each further include an adjustment mechanism. The adjustment mechanism has a function of adjusting an angle of the detection device with respect to the housing.
In the above-described electronic devices, the detection device preferably includes an imaging device. The detection device has a function of outputting, to the arithmetic device, a captured image of the user as the user's data. The arithmetic device has a function of estimating an emotion of the user from the user's data and generating the display data based on the estimated emotion.
In the above-described electronic devices, the user's data is preferably an image of a portion including the user's nose.
In the above-described electronic devices, the user's data is preferably an image of a portion including the user's mouth.
In the above-described electronic devices, a neural network is preferably used for the estimation.
One embodiment of the present invention can provide an electronic device which can recognize a user's emotions with a high accuracy. Another embodiment of the present invention can provide an electronic device which can estimate the kind or the degree of a user's emotion with a high accuracy. Another embodiment of the present invention can provide an electronic device with a high reliability. Another embodiment of the present invention can provide a novel electronic device.
Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not need to have all the effects listed above. Other effects can be derived from the description of the specification, the drawings, the claims, and the like.
FIG. 19A1 to FIG. 19A4 and FIG. 19B1 to FIG. 19B4 each illustrate an example of an image of a portion including a mouth.
Embodiments will be described below with reference to the drawings. Note that the embodiments can be implemented with many different modes, and it will be readily understood by those skilled in the art that modes and details thereof can be changed in various ways without departing from the spirit and scope thereof. Therefore, the present invention should not be construed as being limited to the description of embodiments below.
Note that in 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 the description thereof is not repeated. The same hatching pattern is used for portions having similar functions, and the portions are not denoted by specific reference numerals in some cases.
Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for clarity in some case. Therefore, the size, the layer thickness, or the region is not limited to the illustrated scale.
Note that in this specification and the like, ordinal numbers such as “first” and “second” are used in order to avoid confusion among components and do not limit the number of components.
In this specification, terms for describing arrangement, such as “over”, “above”, “under”, “below”, “left”, and “right”, are used for convenience in describing a positional relation between components with reference to drawings. The positional relation between components is changed as appropriate in accordance with the direction from which each component is described. Thus, the positional relation is not limited to the positional relation described with a term used in this specification and can be described with another term as appropriate depending on the situation.
A transistor is a kind of semiconductor elements and can achieve amplification of current and voltage, switching operation for controlling conduction and non-conduction, and the like. A transistor in this specification includes, in its category, an IGFET (Insulated Gate Field Effect Transistor) and a thin film transistor (TFT).
In this specification and the like, a function of a source and a drain of a transistor are sometimes replaced with each other depending on the polarity of the transistor or when the direction of current flow is changed in circuit operation, for example. Therefore, the terms source and drain can be used interchangeably.
In this specification and the like, the expression “electrically connected” includes the case where components are directly connected to each other and the case where components are connected through an “object having any electric function”. There is no particular limitation on an “object having any electric function” as long as electric signals can be transmitted and received between components that are connected through the object. Thus, even when the expression “electrically connected” is used, there is a case where no physical connection is made and a wiring just extends in an actual circuit. In addition, the expression “directly connected” includes the case where different conductors are connected to each other through a contact. Note that a wiring may be formed of conductors that contain one or more of the same elements or may be formed of conductors that contain different elements.
Unless otherwise specified, off-state current in this specification and the like refers to a drain current of a transistor in an off state (also referred to as a non-conducting state or a cutoff state). Unless otherwise specified, the off state of an n-channel transistor means that the voltage between a gate and a source (Vgs) is lower than the threshold voltage (Vth) (the off state of a p-channel transistor means that Vgs is higher than Vth).
In this specification and the like, the term such as “electrode” or “wiring” does not limit the components functionally. For example, an “electrode” is used as part of a wiring in some cases, and vice versa. Furthermore, the term “electrode” or “wiring” can include the case where a plurality of electrodes or wirings are formed in an integrated manner.
In this specification and the like, the resistance value of a “resistor” is sometimes determined depending on the length of a wiring. Alternatively, the resistance value is sometimes determined by connection to a conductor with resistivity different from that of a conductor used for a wiring. Alternatively, the resistance value is sometimes determined by doping a semiconductor with an impurity.
In this specification and the like, a “terminal” in an electric circuit refers to a portion that inputs or outputs current or voltage or receives or transmits a signal. Accordingly, part of a wiring or an electrode functions as a terminal in some cases.
In this specification and the like, a metal oxide means an oxide of metal in a broad sense. Metal oxides are classified into an oxide insulator, an oxide conductor (including a transparent oxide conductor), an oxide semiconductor (also simply referred to as OS), and the like. For example, a metal oxide used in an active layer of a transistor is referred to as an oxide semiconductor in some cases. In other words, an OS FET can be described as a transistor including an oxide or an oxide semiconductor.
In this embodiment, an electronic device of one embodiment of the present invention will be described with reference to drawings.
One embodiment of the present invention is an electronic device including a display device, a detection device, an arithmetic device, and a housing. The detection device has a function of obtaining data on an emotion of a user and outputting the data to the arithmetic device. The arithmetic device has a function of generating display data based on the data and outputting the display data to the display device.
For example, as data on a user's emotion, a temperature or a humidity around the user's nose or mouth or an image thereof can be used. When a user of an electronic device gets excited, the temperature or the humidity around his/her nose or mouth may be increased. The degree of the user's excitement can be estimated by obtaining the temperature or the humidity around the user's nose or mouth. The kind or the degree of the user's emotion can be estimated by obtaining an image of his/her mouth. An estimated emotion of the user is displayed on an electronic device, whereby the user can know his/her state and have a high sense of immersion.
An electronic device of one embodiment of the present invention has a space at a position of a user's nose in its housing and a detection device is located in the space. By providing the detection device close to a user's nose, the user's emotion can be recognized with a higher accuracy. Furthermore, when the detection device is provided in the space and the detection device is not protruded from the housing, interference between the user or another object and the detection device can be inhibited and the reliability of the electronic device can be improved.
Note that in a block diagram attached to this specification, components are classified according to their functions and shown as independent blocks; however, it is practically difficult to completely separate the components according to their functions, and one component may be related to a plurality of functions or a plurality of components may achieve one function.
The electronic device 10 has a function of displaying an image. The electronic device 10 can be used as a head mounted display (HMD). The electronic device 10 can be favorably used as a display device for displaying an image for augmented reality (AR) or virtual reality (VR). Note that the electronic device 10 can also be called a goggle-type electronic device.
The electronic device 10 includes a housing 11 and a detection device 17 as illustrated in
As illustrated in
The display device 13 includes a plurality of pixels and has a function of displaying images. As the display device 13, a display device such as a liquid crystal display device, a light-emitting apparatus (a light-emitting apparatus in which a light-emitting device is provided in each pixel), an electrophoresis display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), or an FED (Field Emission Display) can be used, for example.
As the light-emitting device, an OLED (Organic Light Emitting Diode), QLED (Quantum-Dot Light-Emitting Diode), or the like preferably used. As a light-emitting substance included in the light-emitting device, a substance emitting fluorescent light (a fluorescent material), a substance emitting phosphorescent light (a phosphorescent material), a substance exhibiting thermally activated delayed fluorescence (a thermally activated delayed fluorescent (TADF) material), an inorganic compound (e.g., a quantum dot material), or the like can be used. An LED (Light Emitting Diode) such as a micro-LED can be used as the light-emitting device.
In the case where the electronic device 10 is used as a head-mounted display, the distance between the user's eyes and the display device 13 is short; thus, the user is likely to perceive pixels and strongly feels granularity, whereby the sense of immersion or realistic emotion of AR and VR might be diminished. Therefore, the display device 13 is preferably a high resolution display device so that pixels are not perceived by the user. The use of the display device 13 with high resolution enables a user of the electronic device 10 to view an image displayed on the display device 13 without feeling the granularity. The resolution of the display device 13 is, for example, preferably 1000 ppi or higher, further preferably 2000 ppi or higher, and still further preferably 5000 ppi or higher. In AR applications, an image of a virtual space is displayed, superimposed on a real space; thus, the display device 13 with high luminance is desired in the light usage environment, in particular.
The detection device 17 has a function of obtaining the information on the ambient environment of the electronic device 10 or data on the user's emotion (hereinafter also referred to as user's data) and outputting the information or data to the arithmetic device 19. For example, the user data can be a temperature, a humidity, sound, an image, or the like. As the detection device 17, a temperature sensor, a humidity sensor, a microphone, or an imaging device can be used, for example. As the detection device, a still camera or video camera can be used, for example. Note that as the detection device 17, two or more of these devices may be used in combination.
The arithmetic device 19 has a function of processing arithmetically user's data output from the detection device 17 to generate display data in accordance with the user's feeing and outputting the display data to the display device 13.
As the arithmetic device 19, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a GPU (Graphics Processing Unit), or the like can be used. Furthermore, the arithmetic device 19 may be obtained with a PLD (Programmable Logic Device) such as a FPGA (Field Programmable Gate Array) or a FPAA (Field Programmable Analog Array).
The memory device 18 has a function of holding a program executed by the arithmetic device 19, data input to the arithmetic device 19, data output from the arithmetic device 19, and the like.
As the memory device 18, a memory device including a nonvolatile memory element can be preferably used. Examples of the memory device 18 include a flash memory, a MRAM (Magnetoresistive Random Access Memory), a PRAM (Phase change RAM), a ReRAM (Resistive RAM), and a FeRAM (Ferroelectric RAM).
The electronic device 10 illustrated in
For example, the input/output device 21 can be communicated with a wired or wireless network, and information can be input to and output from a server 23 via the network. Furthermore, in the case where a wireless communication is used for the network, besides near field communication means such as Wi-Fi (registered trademark) and Bluetooth (registered trademark), a variety of communication means such as the third generation mobile communication system (3G)-compatible communication means, LTE (sometimes also referred to as 3.9G)-compatible communication means, the fourth generation mobile communication system (4G)-compatible communication means, and the fifth generation mobile communication system (5G)-compatible communication means can be used.
The housing 11 will be described with reference to
The housing 11 includes a first portion 12a, a second portion 12b, a third portion 12c, a fourth portion 12d, and a fifth portion 12e. Note that
The second portion 12b is connected to the first portion 12a. The third portion 12c is connected to the second portion 12b via the first portion 12a. The third portion 12c includes the space 41 indicated by a dashed-dotted line in
As illustrated in
The positional relationship between the housing 11, the display device 13, the detection device 17, the arithmetic device 19, the memory device 18, the optical component 15L, and the optical component 15R is described with reference to
The detection device 17 is preferably fixed to the third portion 12c. As illustrated in
The space 41 is described. An enlarged view of the space 41 seen from the fourth portion 12d side (the left side of the user) is shown in
As illustrated in
The angle θ1 of the angle between the housing 11 and the bottom portion of the space 41 is preferably larger than or equal to 120° and smaller than or equal to 170°, further preferably larger than or equal to 130° and smaller than or equal to 165°, further preferably larger than or equal to 135° and smaller than or equal to 160°, further preferably larger than or equal to 140° C. and smaller than or equal to 160°, still further preferably larger than or equal to 145° and smaller than or equal to 155°, yet still further preferably larger than or equal to 150° and smaller than or equal to 155°. The length LB of the space 41 is preferably greater than or equal to 30 mm and less than or equal to 100 mm, further preferably greater than or equal to 40 mm and less than or equal to 95 mm, further preferably greater than or equal to 50 mm and less than or equal to 90 mm, still further preferably greater than or equal to 60 mm and less than or equal to 85 mm, and yet still further preferably greater than or equal to 70 mm and less than or equal to 80 mm. The length LH of the space 41 is preferably greater than or equal to 30 mm and less than or equal to 100 mm, further preferably greater than or equal to 40 mm and less than or equal to 95 mm, further preferably greater than or equal to 50 mm and less than or equal to 90 mm, still further preferably greater than or equal to 60 mm and less than or equal to 85 mm, and yet still further preferably greater than or equal to 70 mm and less than or equal to 80 mm. When the space 41 has the above-described shape, the detection device 17 can be provided at a position not interfering with the user's nose. Furthermore, the detection device 17 can be provided at an angle that allows information of a user's nose or mouth to be easily obtained.
Preferably, the housing 11 does not cover a user's mouth as illustrated in
Although the drawings like
The electronic device 10 may include an adjustment mechanism for adjusting the position and the angle of the detection device 17.
The angle θ2 between the housing 11 and the detection device 17 is preferably within the above-described range of the angle θ1. When the angle θ2 is within the above-described range, the detection device 17 can be provided at a position not interfering with the user's nose. Furthermore, the detection device 17 can be provided at an angle that allows information of a user's nose or mouth to be easily obtained. For example, when the angle 2θ is reduced, information on the user's nose can be easily obtained. For example, when the angle 2θ is increased, information of the user's mouth can be easily obtained.
Although the drawings like
For example, in the space 41, the detection device 17L and the detection device 17R can be provided on the left side and the right side of the user, respectively. In that case, the detection device 17L and the detection device 17R can obtain, respectively, information on the left side and the right side of the user's nose. In addition, the angles of the detection device 17L and the detection device 17R may be adjusted so that the detection device 17L and the detection device 17R can obtain information on the right side and the left side of the user's mouth, respectively.
Data obtained by the detection device 17L and the detection device 17R are each output to the arithmetic device 19. With the use of the plurality of detection devices, the user's emotion can be obtained with a higher accuracy.
The arithmetic device 19 and the memory device 18 are positioned between the second portion 12b and the third portion 12c. The arithmetic device 19 and the memory device 18 may be fixed to one or more of the first portion 12a, the second portion 12b, the third portion 12c, the fourth portion 12d, and the fifth portion 12e. Although the example where the arithmetic device 19 and the memory device 18 are positioned on the fifth portion 12e side is illustrated in the drawings like
The optical component 15L and the optical component 15R are positioned between the second portion 12b and the third portion 12c. The optical component 15L and the optical component 15R may be each fixed to one or more of the first portion 12a, the second portion 12b, the third portion 12c, the fourth portion 12d, and the fifth portion 12e.
As illustrated in
When the user gets excited in using the electronic device 10, the temperatures of the nasal breath and breath are sometimes increased with an increase of the body temperature, leading to the increase of the temperature of the surrounding area of the user's nose and mouth. A temperature sensor is used as the detection device 17 to obtain the temperature of the surrounding area of the user's nose or mouth, whereby the degree of the user's excitement can be estimated. For example, it can be estimated that the higher the temperature of the surrounding area of the user's nose or mouth is, the higher the degree of the user's excitement is.
When the user gets excited in using the electronic device 10, the skin temperature of a user's nose or mouth is sometimes increased with an increase of the body temperature. A temperature sensor is used as the detection device 17 to obtain the skin temperature around the user's nose and mouth, whereby the degree of the user's excitement can be estimated. For example, it can be estimated that the higher the skin temperature around the user's nose and mouth is, the higher the degree of the user's excitement is.
When the user gets excited in using the electronic device 10, breathing becomes faster and the humidity of the surrounding area of the user's nose or mouth is sometimes increased by the nasal breath and breath. A humidity sensor is used as the detection device 17 to obtain the humidity of the surrounding area of the user's nose and mouth, whereby the degree of the user's excitement can be estimated. For example, it can be estimated that the higher the humidity of the surrounding area of the user's nose and mouth is, the higher the degree of the user's excitement is.
When the user gets excited in using the electronic device 10, the voice becomes sometimes loud. A microphone is used as the detection device 17 to obtain the voice of the user, whereby the degree of the user's excitement can be estimated. For example, it can be estimated that the larger the volume of the user's voice is, the higher the degree of the user's excitement is.
When the user gets excited in using the electronic device 10, the user sometimes sweats with an increase of the body temperature. An imaging device is used as the detection device 17 to take an image of the user's nose or a portion below the nose and obtain the sweating state of the nose or the portion below the nose, whereby the degree of the user's excitement can be estimated. For example, it can be estimated that the larger the sweat amount of the nose or the portion below the nose is, the higher the degree of the user's excitement is.
While the user is using the electronic device 10, the kind or the degree of the user's emotion may change. An image of the user's mouth is captured by using an imaging device as the detection device 17 to obtain the shape of the mouth, whereby the kind or the degree of the user's emotion can be estimated.
In the case where an imaging device is used as the detection device 17, the detection device 17 may include a light source (not illustrated). With the light source, light emitted from the light source can be reflected by the user's face and the reflected light can be detected by the detection device 17. For example, the light source preferably has a function of emitting red light, and the imaging device preferably has a function of detecting red light. For example, the light source preferably has a function of emitting near-infrared light, and the imaging device preferably has a function of detecting near-infrared light. For example, a light source preferably has a function of emitting mid-infrared light, and the imaging device preferably has a function of detecting mid-red light. For example, the light source preferably has a function of emitting far-infrared light, and the imaging device preferably has a function of detecting far-infrared light.
Thus, the electronic device 10 can obtain the sweating state of the user or the shape of the user's mouth with a high accuracy.
In this specification and the like, infrared light refers to light with a wavelength ranging from 0.7 μm to 1000 μm, inclusive, for example. Near-infrared light refers to light with a wavelength ranging from 0.7 μm to 2.5 μm, inclusive, for example. Mid-infrared light refers to light with a wavelength ranging from 2.5 μm to 4 μm, inclusive, for example. Far-infrared light refers to light with a wavelength ranging from 4 μm to 1000 μm, inclusive, for example. Note that near-infrared light, mid-infrared light, or far-infrared light may be simply referred to as infrared light. In this specification and the like, red light refers to light with a wavelength ranging from 0.6 μm to 0.75 μm, inclusive, for example.
The electronic device 10 of one embodiment of the present invention can obtain the degree of a user's excitement and the kind or the degree of a user's emotion by having the detection device 17. Note that in this specification and the like, the degree of a user's excitement and the kind or the degree of a user's emotion are collectively referred to as a user's emotion. In addition, the electronic device 10 of one embodiment of the present invention can display information corresponding to the user's emotion on the display device 13. A character (also referred to as an avatar) as an alter ego of the user can have a facial expression corresponding to the user's emotion, which can be displayed on the display device 13. The user can know his/her emotion and have a higher sense of immersion. In addition, the user can know his/her emotion and decide to have a break or the like.
As illustrated in
A region on the side opposite to the first portion 12a of the second portion 12b is a portion in contact with a user's forehead. A region on the side opposite to the first portion 12a of the third portion 12c is a portion in contact with a user's cheek. The regions preferably each have a curved shape, specifically, a circular arc shape toward the first portion 12a. With the regions each having a curved shape or a circular arc shape, the second portion 12b can be closely contact with the user's cheek or forehead. Thus, light leakage from the outside of the electronic device 10 is suppressed and the user can feel a higher sense of immersion. The shape of the housing 11 of the electronic device 10 is not limited to the structure illustrated in the drawings like
The optical component 15L and the optical component 15R each include a region overlapping with the display device 13, and are positioned between the display device 13 and the user. The user can view an image displayed on the display device 13 through the optical component 15L and the optical component 15R. The drawings like
For example, plastic or glass can be used as the materials of the optical component 15L and the optical component 15R. For plastic, a material with a high visible-light transmitting property is preferable, for example, a urethane resin, an acrylic resin, a carbon resin, an allylic resin, or the like can be used. In addition, when a material in which a halogen, an aromatic ring, or sulfur with a high atomic refraction is added to such plastics is used, the refractive indices of the optical component 15L and the optical component 15R can be increased. As the halogen, any one or more of chlorine, bromine, and iodine is preferably selected.
Although the drawings like
The electronic device 10a illustrated in
As illustrated in
Although the drawings like
In
As illustrated in
As illustrated in
Note that although
<Estimation of User's Emotion>
A method for estimating a user's emotion is described. Here, an example of an image of a portion including a user's mouth will be described.
The feature-extraction unit 53 has a function of extracting feature points from the image of a portion including a user's mouth output from the detection device 17, obtaining a feature value calculated from the positions of feature points, and outputting the feature value to the estimation unit 54.
In the case where information obtained by the detection device 17 is an image of the portion including the user's mouth, the feature points are, for example, an upper edge of the upper lip, a lower edge of the lower lip, the right corner and the left corner of the mouth.
As a method of feature-extraction by the feature-extraction unit 53, various types of algorithm can be employed. For example, an algorithm such as SIFT (Scaled Invariant Feature Transform), SURF (Speeded Up Robust Features), or HOG (Histograms of Oriented Gradients) can be used in the feature-extraction unit 53.
For the feature-extraction by the feature-extraction unit 53, a neural network can be used.
Data 71 is input to the neural network NN1. Image data captured by the detection device 17 can be used as the data 71, for example. The data 71 includes coordinates and gray-scale values of each pixel. Data 72 is output from the neural network NN1. The data 72 includes the position coordinates of the aforementioned feature point.
The neural network NN1 has learned so as to extract the aforementioned feature point from the data 71 such as image data and output the coordinates of the feature point. The neural network NN1 has learned so that edge computing using various filters or the like in the intermediate layers 62 increases a neuron value of the output layer 63 corresponding to the coordinates of the aforementioned feature point.
The estimation unit 54 has a function of estimating the user's emotion of the electronic device 10 from the information of the feature point, which is input from the feature-extraction unit 53, and outputting the estimated information to the information-generation unit 55. A neural network can be used for the estimation by the estimation unit 54.
The data 72 generated by the feature-extraction unit 53 is input to the neural network NN2. The data 72 includes information on the coordinates of the extracted feature point.
As data input to the neural network NN2, data obtained by processing the data 72 may be used. For example, data obtained by performing calculation of a vector connecting given two feature points on all or some of the feature points may be used as data input to the neural network NN2. Moreover, data obtained by normalizing the calculated vectors may be used. Note that hereinafter, data obtained by processing the data 72 output from the neural network NN1 is also referred to as the data 72.
Data 73 is output from the neural network NN2 to which the data 72 is input. The data 73 corresponds to neuron values output from respective neurons of the output layer 63. Each neuron of the output layer 63 is associated with one emotion. As illustrated in
The neural network NN2 has learned so as to estimate the degree of each emotion from the data 72 and output the estimation as neuron values. Accordingly, the user's emotion can be estimated from the shape of the user's mouth by the neural network NN2.
The degree of interest, which is included in the data 74, can be estimated, for example, by inputting the degrees of emotions such as joy, pleasure, surprise, and hatred, which are included in the data 73, to a predetermined formula. For example, the formula can be set so that the degree of interest increases as the degrees of joy, pleasure, and surprise are higher and the degree of interest decreases as the degree of hatred is higher.
Note that the estimation of emotions can also be estimated without using a neural network. For example, a pattern matching method, a template matching method, or the like in which the image of a portion including the user's mouth obtained by the detection device 17 is compared with a template image and the similarity degree is used, may be employed. In that case, a structure without the feature-extraction unit 53 can also be employed.
The information-generation unit 55 has a function of determining or generating information to be shown to the user on the basis of the emotion, which is estimated by the estimation unit 54, and outputting the information to the display device 13. Accordingly, the display device 13 can show information corresponding to the information generated in the information-generation unit 55.
Note that the data 72 output from the feature-extraction unit 53 may be directly input to the information-generation unit 55 without being input to the estimation unit 54. For example, the user's emotion can be detected by extraction of feature points with the feature-extraction unit 53 without estimation by the estimation unit 54. In such a case, the data 72 output from the feature-extraction unit 53 is directly input to the information-generation unit 55, whereby power consumption of the electronic device 10 can be reduced.
FIG. 19A1 to FIG. 19A4 illustrate examples of images of the portions including the user's mouth which can be used as the data 71. FIG. 19A1 to FIG. 19A4 illustrate examples of images of the portions including the user's mouth with a high degree of the user's emotion “joy”, a high degree of “pleasure”, a high degree of “surprise”, and a high degree of “hatred”. FIG. 19B1 to FIG. 19B4 illustrate examples in which feature points of the images of the portions including the mouth illustrated in FIG. 19A1 to FIG. 19A4 are extracted. In examples illustrated in FIG. 19B1 to FIG. 19B4, upper edges of the upper lip, LPTL, LPT, and LPTR; the lower edges of the lower lip, LPBL, LPB, and LPBR, the right corner of the mouth, LPR; and the left corner of the mouth, LPL are extracted as the feature points. The feature-extraction unit 53 extracts these feature points and output the information of the feature points to the estimation unit 54. The estimation unit 54 estimates the user's emotion on the basis of the information of the feature points and outputs the information of the user's emotion to the information-generation unit 55. The information-generation unit determines or generates information to be shown to the user from the information of the user's emotion and outputs the information to be shown to the user to the display device 13. The display device 13 can display the information to be shown to the user.
An example of user's information to be shown in the electronic device is described below.
In
The information 81 illustrated in
The user's data may be shown as the information 81. For example, the temperature of the surrounding area of the user's nose or mouth can be shown as the information 81. For example, the volume of a voice can be shown as the information 81.
The information 82 illustrated in
As described above, the user can know the degree of his/her excitement by showing the degree of the user's excitement to the user, and have a higher sense of immersion. Alternatively, the user can know the degree of his/her excitement and can choose to take a break or the like.
In
In
Although
As described above, a character having a facial expression reflecting the emotion in accordance with the estimated user's emotion is shown to the user, whereby the user can know his/her emotion and have a higher sense of immersion. Alternatively, the user can know an emotion that he/she does not perceive. The method of showing the information of the emotion to the user using a facial expression of a character is described here, but without being limited to this, various methods can be used as long as the kind or degree of emotions can be visualized.
In the electronic device of one embodiment of the present invention, the housing 11 includes the space 41 positioned at the user's nose, and there is no particular limitation on the structure and the shapes of the portions other than the space 41.
The housing 11 can have a structure in which a plurality of housings are connected. Examples of the structure of the housing 11 are illustrated in
In
By connecting a plurality of parts to form the housing 11, it becomes easy to perform loading a component (such as the arithmetic device 19) provided in the electronic device 10. For example, in the housing 11 including the first part 11a to the fifth part 11e, a component is loaded to each of the first part 11a to the fifth part 11e and then the first part 11a to the fifth part 11e can be connected. This case can increase the productivity, as compared with the productivity in the case of loading the components after the first part 11a to the fifth part 11e are connected. Furthermore, one or some of the parts can be detachable from the housing 11, whereby a broken component can be easily replaced, for example.
The shape of the housing 11 is not particularly limited to the shape shown in the drawings like
The electronic device of one embodiment of the present invention may include a fastening 25 as illustrated in
At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification, as appropriate.
In this embodiment, a display device, a light source, an imaging device, and the like that can be used in the electronic device of one embodiment of the present invention will be described.
The circuit 840 is electrically connected to the source driver circuit 822. Note that the circuit 840 may be electrically connected to another circuit or the like.
The pixels 834 in the same row are electrically connected to the gate driver circuit 821 through a wiring 831, and the pixels 834 in the same column are electrically connected to the source driver circuit 822 through a wiring 832. The wiring 831 functions as a scan line and the wiring 832 functions as a data line.
Although
The gate driver circuit 821 has a function of generating a signal for controlling the operation of the pixel 834 and supplying the signal to the pixel 834 through the wiring 831. The source driver circuit 822 has a function of generating an image signal and supplying the signal to the pixel 834 through the wiring 832. The circuit 840 has a function of receiving image data that serves as a base for an image signal generated by the source driver circuit 822 and supplying the received image data to the source driver circuit 822, for example. The circuit 840 also has a function of a control circuit that generates a start pulse signal, a clock signal, and the like. In addition, the circuit 840 can have a function that the gate driver circuit 821 and the source driver circuit 822 do not have.
The pixel array 833 has a function of displaying an image corresponding to image signals supplied to the pixels 834 from the source driver circuit 822. Specifically, light with luminance corresponding to the image signals is emitted from the pixels 834, whereby an image is displayed on the pixel array 833.
In
In the display device 810, the gate driver circuit 821 and the source driver circuit 822, which are provided in the layer 820, each include a region overlapping with the pixel array 833. For example, the gate driver circuit 821 and the source driver circuit 822 each include a region overlapping with some of the pixels 834. Stacking the gate driver circuit 821 and the source driver circuit 822 with the pixel array 833 to have an overlap region allows the display device 810 to have a narrower bezel and a smaller size.
The gate driver circuit 821 and the source driver circuit 822 have an overlap region where they are not strictly separated from each other. The region is referred to as a region 823. With the region 823, the area occupied by the gate driver circuit 821 and the source driver circuit 822 can be reduced. Accordingly, even when the area of the pixel array 833 is small, the gate driver circuit 821 and the source driver circuit 822 can be provided without extending beyond the pixel array 833. Alternatively, the area of the region where the gate driver circuit 821 and the source driver circuit 822 do not overlap with the pixel array 833 can be reduced. In the above manner, the bezel and size can be further reduced, compared to the structure without the region 823.
The circuit 840 can be provided not to overlap with the pixel array 833. Note that the circuit 840 may be provided to have a region overlapping with the pixel array 833.
Although
Although
Alternatively, as illustrated in
Providing the pixel 834 having a function of emitting white light (W) in the display device 810 as illustrated in
As illustrated in
EL devices are classified according to whether a light-emitting material is an organic compound or an inorganic compound. In general, the former is referred to as an organic EL device, and the latter is referred to as an inorganic EL device.
In an organic EL device, by voltage application, electrons are injected from one electrode to the EL layer and holes are injected from the other electrode to the EL layer. Then, the carriers (electrons and holes) are recombined, and thus, a light-emitting organic compound is excited. The light-emitting organic compound returns to a ground state from the excited state, thereby emitting light. Owing to such a mechanism, this light-emitting device is referred to as a current-excitation light-emitting device.
In addition to the light-emitting compound, the EL layer may further include any of a substance with a high hole-injection property, a substance with a high hole-transport property, a hole-blocking material, a substance with a high electron-transport property, a substance with a high electron-injection property, a substance with a bipolar property (a substance with a high electron- and hole-transport properties), and/or the like.
The EL layer can be formed by an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, or the like.
The inorganic EL devices are classified according to their device structures into a dispersion-type inorganic EL device and a thin-film inorganic EL device. A dispersion-type inorganic EL device includes a light-emitting layer where particles of a light-emitting material are dispersed in a binder, and its light emission mechanism is donor-acceptor recombination type light emission that utilizes a donor level and an acceptor level. A thin-film inorganic EL device has a structure where a light-emitting layer is positioned between dielectric layers, which are further positioned between electrodes, and its light emission mechanism is localization type light emission that utilizes inner-shell electron transition of metal ions.
In order to extract light emitted from the light-emitting device, at least one of the pair of electrodes is preferably transparent. The light-emitting device that is formed over a substrate together with a transistor can have any of a top emission structure in which emitted light is extracted through the surface opposite to the substrate; a bottom emission structure in which emitted light is extracted through the surface on the substrate side; and a dual emission structure in which emitted light is extracted through both sides.
Note that an element similar to the light-emitting device 572 can be used as light-emitting devices other than the light-emitting device 572.
One of a source and a drain of the transistor 552 is electrically connected to the wiring 832. The other of the source and the drain of the transistor 552 is electrically connected to one electrode of the capacitor 562 and a gate of the transistor 554. The other electrode of the capacitor 562 is electrically connected to a wiring 835a. A gate of the transistor 552 is electrically connected to the wiring 831. One of a source and a drain of the transistor 554 is electrically connected to the wiring 835a. The other of the source and the drain of the transistor 554 is electrically connected to one electrode of the light-emitting device 572. The other electrode of the light-emitting device 572 is electrically connected to a wiring 835b. The potential VSS is supplied to the wiring 835a, and the potential VDD is supplied to the wiring 835b. The wiring 835a and the wiring 835b function as power supply lines.
In the pixel 834 having the configuration illustrated in
One of a source and a drain of the transistor 511 is electrically connected to the wiring 832_1. The other of the source and the drain of the transistor 511 is electrically connected to one electrode of the capacitor 515. A gate of the transistor 511 is electrically connected to the wiring 831_1. One of a source and a drain of the transistor 513 is electrically connected to the wiring 832_2. The other of the source and the drain of the transistor 513 is electrically connected to the other electrode of the capacitor 515. A gate of the transistor 513 is electrically connected to the wiring 831_2. The other electrode of the capacitor 515 is electrically connected to one electrode of the capacitor 517. The one electrode of the capacitor 517 is electrically connected to a gate of the transistor 521. One of a source and a drain of the transistor 521 is electrically connected to one electrode of the light-emitting device 572. The other electrode of the capacitor 517 is electrically connected to a wiring 535. The other of the source and the drain of the transistor 521 is electrically connected to a wiring 537. The other electrode of the light-emitting device 572 is electrically connected to a wiring 539.
In this specification and the like, a voltage supplied to a light-emitting device indicates a difference between a potential supplied to one electrode of the light-emitting device and a potential supplied to the other electrode of the light-emitting device.
A node where the other of the source and the drain of the transistor 511 and the one electrode of the capacitor 515 are electrically connected to each other is referred to as a node N1. A node where the other of the source and the drain of the transistor 513, the one electrode of the capacitor 517, and the gate of the transistor 521 are electrically connected to each other is referred to as a node N2. In
The wiring 535 can be shared by all pixels 834 provided in the display device 810, for example. In that case, a potential supplied to the wiring 535 is a common potential. Constant potentials can be supplied to the wiring 537 and the wiring 539. For example, a high potential can be supplied to the wiring 537, and a low potential can be supplied to the wiring 539. The wirings 537 and 539 function as power supply lines.
The transistor 521 has a function of controlling a current to be supplied to the light-emitting device 572. The capacitor 517 functions as a storage capacitor. The capacitor 517 may be omitted.
Note that
In the pixel 834, turning off the transistor 511 enables retention of the potential of the node N1. Turning off the transistor 513 enables retention of the potential of the node N2. Furthermore, by turning off the transistor 513 and then writing a predetermined potential to the node N1 through the transistor 511, the potential of the node N2 can be changed in accordance with a change in the potential of the node N1 by capacitive coupling through the capacitor 515.
A transistor containing a metal oxide in a channel formation region (hereinafter also referred to as OS transistor) can be used as the transistor 511 and the transistor 513. A metal oxide can have a band gap of 2 eV or more, or 2.5 eV or more. Thus, an OS transistor exhibits an extremely low leakage current (off-state current) in an off state. Accordingly, the use of OS transistors as the transistor 511 and the transistor 513 enables the potentials of the node N1 and the node N2 to be held for a long time.
The metal oxide can be, for example, an In-M-Zn oxide (the element M is one or more of aluminum, gallium, yttrium, tin, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like). In particular, aluminum, gallium, yttrium, or tin is preferably used for the element M. Alternatively, indium oxide, zinc oxide, an In—Ga oxide, an In—Zn oxide, a Ga—Zn oxide, or gallium oxide may be used as the metal oxide.
Next, an example of an operation method for the pixel 834 having the configuration in
In the operation shown in
In the period T1, a potential for turning on the transistor is supplied to both the wiring 831_1 and the wiring 831_2. In addition, a potential Vref that is a fixed potential is supplied to the wiring 832_1, and a potential Vw is supplied to the wiring 832_2.
The potential \Tref is supplied from the wiring 832_1 to the node N1 through the transistor 511. The potential Vw is supplied from the wiring 832_2 to the node N2 through the transistor 513. Thus, a potential difference Vw−Vref is retained in the capacitor 515.
Then, in the period T2, a potential for turning on the transistor 511 is supplied to the wiring 831_1, and a potential for turning off the transistor 513 is supplied to the wiring 831_2. A potential Vdata is supplied to the wiring 832_1, and a predetermined constant potential is supplied to the wiring 832_2. Note that the potential of the wiring 832_2 may be floating.
The potential Vdata is supplied to the node N1 through the transistor 511. At this time, owing to capacitive coupling through the capacitor 515, the potential of the node N2 is changed by a potential dV in accordance with the potential Vdata. That is, a potential that is the sum of the potential Vw and the potential dV is input to the circuit 401. Note that although the potential dV is shown as having a positive value in
Here, the potential dV is roughly determined by the capacitance of the capacitor 515 and the capacitance of the circuit 401. When the capacitance of the capacitor 515 is sufficiently larger than the capacitance of the circuit 401, the potential dV becomes close to a potential difference Vdata−Vref.
As described above, the pixel 834 can generate the potential supplied to the node N2 in combination with two kinds of data signals; thus, an image displayed on the pixel array 833 can be corrected inside the pixel 834. Here, one of the two kinds of data signals can be the aforementioned image signal, and the other can be a correction signal, for example. For example, when the potential Vw corresponding to a correction signal is supplied to the node N2 in the period T1 and then the potential Vdata corresponding to an image signal is supplied to the node N1 in the period T2, an image based on the image signal corrected by the correction signal can be displayed on the pixel array 833. Note that not only image signals but also correction signals and the like can be generated by the source driver circuit 822 included in the display device 810.
In the pixel 834 having the configuration in
Note that the pixel configuration is not limited to that illustrated in
In the circuit 401 with the configuration illustrated in
Like the circuit 401 with the configuration illustrated in
In the circuit 401 with the configuration illustrated in
In the pixel 834 including the circuit 401 with the configuration illustrated in
The wiring 543 can be electrically connected to a supply source of a certain potential such as a reference potential. That is, the wiring 543 has a function of a power supply line. Supplying a certain potential from the wiring 543 to the other of the source and the drain of the transistor 521 enables stable writing of an image signal to the pixel 834.
The wiring 543 can be electrically connected to a circuit 520. The circuit 520 can have at least one of a function of a supply source of the certain potential, a function of obtaining electrical characteristics of the transistor 521, and a function of generating a correction signal.
The circuit 401 having the configuration illustrated in
In the circuit 401 with the configuration illustrated in
The other electrode of the capacitor 517 is electrically connected to the other of the source and the drain of the transistor 521. The other of the source and the drain of the transistor 521 is electrically connected to the other of the source and the drain of the transistor 529. The other of the source and the drain of the transistor 529 is electrically connected to one electrode of the light-emitting device 572.
A gate of the transistor 529 is electrically connected to the wiring 831_1. The other electrode of the light-emitting device 572 is electrically connected to the wiring 539.
The gate driver circuit 821 is electrically connected to the pixels 834 through wirings 831-1. The gate driver circuit 821 is electrically connected to the pixels 834 through wirings 831-2. The wirings 831-1 and the wirings 831-2 function as scan lines.
The source driver circuit 822 is electrically connected to an input terminal of the demultiplexer circuit 824. A first output terminal of the demultiplexer circuit 824 is electrically connected to the pixel 834 through a wiring 832-1. A second output terminal of the demultiplexer circuit 824 is electrically connected to the pixel 834 through a wiring 832-2. The wiring 832-1 and the wiring 832-2 function as data lines.
Note that the source driver circuit 822 and the demultiplexer circuits 824 may be collectively referred to as a source driver circuit. In other words, the demultiplexer circuits 824 may be included in the source driver circuit 822.
In the display device 810 having the structure in
Here, when the display device 810 having the structure in
When the potential Vw is supplied to the node N2 and then the potential Vdata is supplied to the node N1 as shown in
The level of the potential Vdata corresponding to the image signal S1 and the level of the potential Vw corresponding to the image signal S2 are limited by the withstand voltage of the source driver circuit 822, for example. In view of this, superimposing the image signal S1 and the image signal S2 enables an image corresponding to an image signal having a potential higher than a potential that the source driver circuit 822 can output, to be displayed on the pixel array 833. Thus, a large amount of current can flow through the light-emitting device 572; hence, the pixel array 833 can display a high-luminance image. Moreover, the dynamic range, which is the range of luminance of images that the pixel array 833 can display, can be enlarged.
An image corresponding to the image signal S1 and an image corresponding to the image signal S2 may be the same or different from each other. When an image corresponding to the image signal S1 and an image corresponding to the image signal S2 are the same, the pixel array 833 can display an image with higher luminance than the luminance of the image corresponding to either the image signal S1 or the image signal S2.
Here, to rewrite the potential Vw corresponding to the image signal S2, the potential Vdata corresponding to the image signal S1 needs to be written again as described above. On the other hand, to rewrite the potential Vdata, the potential Vw does not need to be rewritten. Therefore, the image P2 is preferably an image that needs to be rewritten less frequently than the image P1.
As the substrate 701, a single crystal semiconductor substrate such as a single crystal silicon substrate can be used. Note that a semiconductor substrate other than a single crystal semiconductor substrate may be used as the substrate 701.
A transistor 441 and a transistor 601 are provided on the substrate 701. The transistor 441 can be a transistor provided in the circuit 840. The transistor 601 can be a transistor provided in the gate driver circuit 821 or a transistor provided in the source driver circuit 822. That is, the transistor 441 and the transistor 601 can be provided in the layer 820 illustrated in the drawings like
The transistor 441 is formed of a conductor 443 functioning as a gate electrode, an insulator 445 functioning as a gate insulator, and part of the substrate 701 and includes a semiconductor region 447 including a channel formation region, a low-resistance region 449a functioning as one of a source region and a drain region, and a low-resistance region 449b functioning as the other of the source region and the drain region. The transistor 441 can be a p-channel transistor or an n-channel transistor.
The transistor 441 is electrically isolated from other transistors by an element isolation layer 403.
Here, in the transistor 441 illustrated in
A transistor having a projecting semiconductor region, like the transistor 441, can be referred to as a fin-type transistor because a projecting portion of a semiconductor substrate is used. An insulator functioning as a mask for forming a projecting portion may be provided in contact with the top surface of the projecting portion. Although
Note that the structure of the transistor 441 illustrated in
The transistor 601 can have the same structure as the transistor 441.
An insulator 405, an insulator 407, an insulator 409, and an insulator 411 are provided over the substrate 701, in addition to the element isolation layer 403, the transistor 441, and the transistor 601. A conductor 451 is embedded in the insulator 405, the insulator 407, the insulator 409, and the insulator 411. Here, the top surface of the conductor 451 and the top surface of the insulator 411 can be substantially level with each other.
An insulator 413 and an insulator 415 are provided over the conductor 451 and the insulator 411. A conductor 457 is embedded in the insulator 413 and the insulator 415.
An insulator 417 and an insulator 419 are provided over the conductor 457 and the insulator 415. A conductor 459 is embedded in the insulator 417 and the insulator 419.
An insulator 421 and an insulator 214 are provided over the conductor 459 and the insulator 419. A conductor 453 is embedded in the insulator 421 and the insulator 214. Here, the top surface of the conductor 453 and the top surface of the insulator 214 can be substantially level with each other.
An insulator 216 is provided over the conductor 453 and the insulator 214. A conductor 455 is embedded in the insulator 216. Here, the top surface of the conductor 455 and the top surface of the insulator 216 can be substantially level with each other.
An insulator 222, an insulator 224, an insulator 254, an insulator 244, an insulator 280, an insulator 274, and an insulator 281 are provided over the conductor 455 and the insulator 216. A conductor 305 is embedded in the insulator 222, the insulator 224, the insulator 254, the insulator 244, the insulator 280, the insulator 274, and the insulator 281. Here, the top surface of the conductor 305 and the top surface of the insulator 281 can be substantially level with each other.
An insulator 361 is provided over the conductor 305 and the insulator 281. A conductor 317 and a conductor 337 are embedded in the insulator 361. Here, the top surface of the conductor 337 and the top surface of the insulator 361 can be substantially level with each other.
An insulator 363 is provided over the conductor 337 and the insulator 361. A conductor 347, a conductor 353, a conductor 355, and a conductor 357 are embedded in the insulator 363. Here, the top surfaces of the conductor 353, the conductor 355, and the conductor 357 and the top surface of the insulator 363 can be substantially level with each other.
A connection electrode 760 is provided over the conductor 353, the conductor 355, the conductor 357, and the insulator 363. An anisotropic conductor 780 is provided to be electrically connected to the connection electrode 760. A flexible printed circuit (FPC) 716 is provided to be electrically connected to the anisotropic conductor 780. A variety of signals and the like are supplied to the display device 810 from the outside of the display device 810 through the FPC 716.
As illustrated in
A transistor 750 is provided over the insulator 214. The transistor 750 can be a transistor provided in the pixel 834. That is, the transistor 750 can be provided in the layer 830 illustrated in the drawings like
A conductor 301a and a conductor 301b are embedded in the insulator 254, the insulator 244, the insulator 280, the insulator 274, and the insulator 281. The conductor 301a is electrically connected to one of the source and the drain of the transistor 750, and the conductor 301b is electrically connected to the other of the source and the drain of the transistor 750. Here, the top surfaces of the conductor 301a and the conductor 301b and the top surface of the insulator 281 can be substantially level with each other.
A conductor 311, a conductor 313, a conductor 331, a capacitor 790, a conductor 333, and a conductor 335 are embedded in the insulator 361. The conductor 311 and the conductor 313 are electrically connected to the transistor 750 and serve as wirings. The conductor 333 and the conductor 335 are electrically connected to the capacitor 790. Here, the top surfaces of the conductor 331, the conductor 333, and the conductor 335 and the top surface of the insulator 361 can be substantially level with each other.
A conductor 341, a conductor 343, and a conductor 351 are embedded in the insulator 363. Here, the top surface of the conductor 351 and the top surface of the insulator 363 can be substantially level with each other.
The insulator 405, the insulator 407, the insulator 409, the insulator 411, the insulator 413, the insulator 415, the insulator 417, the insulator 419, the insulator 421, the insulator 214, the insulator 280, the insulator 274, the insulator 281, the insulator 361, and the insulator 363 function as an interlayer film and may also function as a planarization film that covers unevenness thereunder. For example, the top surface of the insulator 363 may be planarized by planarization treatment using a chemical mechanical polishing (CMP) method or the like to increase the level of planarity.
As illustrated in
In the example illustrated in
The display device 810 illustrated in
The light-emitting device 572 includes a conductor 772, an EL layer 786, and a conductor 788. The conductor 788 is provided on the substrate 705 side and functions as a common electrode. The conductor 772 is electrically connected to the other of the source and the drain of the transistor 750 through the conductor 351, the conductor 341, the conductor 331, the conductor 313, and the conductor 301b. The conductor 772 is formed over the insulator 363 and functions as a pixel electrode. The EL layer 786 contains an organic compound or an inorganic compound such as a quantum dot.
Examples of materials that can be used for an organic compound include a fluorescent material and a phosphorescent material. Examples of materials that can be used for a quantum dot include a colloidal quantum dot material, an alloyed quantum dot material, a core-shell quantum dot material, and a core quantum dot material.
In the display device 810 illustrated in
The light-emitting device 572 can have a microcavity structure, which will be described later in detail. Thus, light of predetermined colors (e.g., RGB) can be extracted without a coloring layer, and the display device 810 can perform color display. The structure without a coloring layer can prevent light absorption due to the coloring layer. As a result, the display device 810 can display high-luminance images, and power consumption of the display device 810 can be reduced. Note that a structure without a coloring layer can be employed even when the EL layer 786 is formed into an island shape for each pixel or formed into a stripe shape for each pixel column, i.e., the EL layers 786 are formed separately for respective colors.
A light-blocking layer 738 is provided to include a region overlapping with the insulator 730. The light-blocking layer 738 is covered with an insulator 734. A space between the light-emitting device 572 and the insulator 734 is filled with a sealing layer 732.
A component 778 is provided between the insulator 730 and the EL layer 786. Another component 778 is provided between the insulator 730 and the insulator 734. The component 778 is a columnar spacer and has a function of controlling the distance (cell gap) between the substrate 701 and the substrate 705. Note that a spherical spacer may be used as the component 778.
The light-blocking layer 738 and the insulator 734 that is in contact with the light-blocking layer 738 are provided on the substrate 705 side. The light-blocking layer 738 has a function of blocking light emitted from adjacent regions. Alternatively, the light-blocking layer 738 has a function of preventing external light from reaching the transistor 750 or the like.
Although
An insulator 613 and an insulator 614 are provided over the substrate 701, and the transistor 602 and the transistor 603 are provided over the insulator 614. Note that a transistor or the like may be provided between the substrate 701 and the insulator 613. For example, a transistor having a structure similar to that of the transistor 441 and the transistor 601 illustrated in
The transistor 602 can be a transistor provided in the circuit 840. The transistor 603 can be a transistor provided in the gate driver circuit 821 or a transistor provided in the source driver circuit 822. That is, the transistor 602 and the transistor 603 can be provided in the layer 820 illustrated in the drawings like
The transistor 602 and the transistor 603 can have a structure similar to that of the transistor 750. Note that the transistor 602 and the transistor 603 may be OS transistors having a structure different from that of the transistor 750.
An insulator 616, an insulator 622, an insulator 624, an insulator 654, an insulator 644, an insulator 680, an insulator 674, and an insulator 681 are provided over the insulator 614, in addition to the transistor 602 and the transistor 603. A conductor 461 is embedded in the insulator 654, the insulator 644, the insulator 680, the insulator 674, and the insulator 681. Here, the top surface of the conductor 461 and the top surface of the insulator 681 can be substantially level with each other.
An insulator 501 is provided over the conductor 461 and the insulator 681. A conductor 463 is embedded in the insulator 501. Here, the top surface of the conductor 463 and the top surface of the insulator 501 can be substantially level with each other.
An insulator 503 is provided over the conductor 463 and the insulator 501. A conductor 465 is embedded in the insulator 503. The top surface of the conductor 465 and the top surface of the insulator 503 can be substantially level with each other.
An insulator 505 is provided over the conductor 465 and the insulator 503. A conductor 467 is embedded in the insulator 505.
An insulator 507 is provided over the conductor 467 and the insulator 505. A conductor 469 is embedded in the insulator 507. Here, the top surface of the conductor 469 and the top surface of the insulator 507 can be substantially level with each other.
An insulator 509 is provided over the conductor 469 and the insulator 507. A conductor 471 is embedded in the insulator 509.
The insulator 421 and the insulator 214 are provided over the conductor 471 and the insulator 509. The conductor 453 is embedded in the insulator 421 and the insulator 214. Here, the top surface of the conductor 453 and the top surface of the insulator 214 can be substantially level with each other.
As illustrated in
The insulator 613, the insulator 614, the insulator 680, the insulator 674, the insulator 681, the insulator 501, the insulator 503, the insulator 505, the insulator 507, and the insulator 509 function as interlayer films and may also function as planarization films that cover unevenness thereunder.
When the display device 810 has the structure illustrated in
The EL layer 786 has a structure in which a hole-injection layer 721, a hole-transport layer 722, a light-emitting layer 723, an electron-transport layer 724, and an electron-injection layer 725 are stacked in this order over the conductor 772. Note that the order of the stacked layers is reversed when the conductor 772 functions as a cathode and the conductor 788 functions as an anode.
The light-emitting layer 723 contains a light-emitting material and a plurality of materials in appropriate combination, so that fluorescence or phosphorescence of a desired emission color can be obtained. The light-emitting layer 723 may have a stacked-layer structure having different emission colors. In that case, the light-emitting substance and other substances may be different between the stacked light-emitting layers.
For example, when the light-emitting device 572 has a micro optical resonator (microcavity) structure with the conductor 772 and the conductor 788 in
Note that when the conductor 772 of the light-emitting device 572 is a reflective electrode having a stacked-layer structure of a reflective conductive material and a light-transmitting conductive material (transparent conductive film), optical adjustment can be performed by controlling the thickness of the transparent conductive film. Specifically, when the wavelength of light from the light-emitting layer 723 is X, the interelectrode distance between the conductor 772 and the conductor 788 is preferably adjusted to around mλ/2 (m is a natural number).
To amplify desired light (wavelength: λ) obtained from the light-emitting layer 723, the optical path length from the conductor 772 to a region where desired light is obtained in the light-emitting layer (light-emitting region) and the optical path length from the conductor 788 to the region where desired light is obtained in the light-emitting layer 723 (light-emitting region) are preferably adjusted to around (2m′+1)λ/4 (m′ is a natural number). Here, the light-emitting region means a region where holes and electrons are recombined in the light-emitting layer 723.
By such optical adjustment, the spectrum of specific monochromatic light emitted from the light-emitting layer 723 can be narrowed and light emission with high color purity can be obtained.
In the above case, the optical path length between the conductor 772 and the conductor 788 is, to be exact, the total thickness between a reflective region in the conductor 772 and a reflective region in the conductor 788. However, it is difficult to precisely determine the reflection region in the conductor 772 and the conductor 788; hence, it is assumed that the above effect is adequately obtained wherever the reflective region is placed in the conductor 772 and the conductor 788. Furthermore, the optical path length between the conductor 772 and the light-emitting layer emitting desired light is, to be exact, the optical path length between the reflective region in the conductor 772 and the light-emitting region where desired light is obtained in the light-emitting layer. However, it is difficult to precisely determine the reflective region in the conductor 772 and the light-emitting region where desired light is obtained in the light-emitting layer; thus, it is assumed that the above effect is adequately obtained wherever the reflective region and the light-emitting region are placed in the conductor 772 and the light-emitting layer emitting desired light.
The light-emitting device 572 illustrated in
Note that the light-emitting device 572 illustrated in
At least one of the conductors 772 and 788 can be a light-transmitting electrode (e.g., a transparent electrode or a transflective electrode). In the case where the light-transmitting electrode is a transparent electrode, the transparent electrode has a visible light transmittance of higher than or equal to 40%. In the case where the light-transmitting electrode is a transflective electrode, the transflective electrode has a visible light reflectance of higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%. These electrodes preferably have a resistivity of 1×10−2 Ωcm or less.
When the conductor 772 or the conductor 788 is an electrode having reflectivity (reflective electrode), the visible light reflectance of the reflective electrode is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 70% and lower than or equal to 100%. This electrode preferably has a resistivity of 1×10−2 Ωcm or less.
The light-emitting device 572 may have a structure illustrated in
The charge generation layer 792 has a function of injecting electrons into one of the EL layer 786a and the EL layer 786b and injecting holes to the other of the EL layer 786a and the EL layer 786b when a voltage is supplied between the conductor 772 and the conductor 788. Accordingly, when a voltage is supplied such that the potential of the conductor 772 becomes higher than the potential of the conductor 788, electrons are injected into the EL layer 786a from the charge generation layer 792 and holes are injected into the EL layer 786b from the charge generation layer 792.
Note that in terms of light extraction efficiency, the charge generation layer 792 preferably transmits visible light (specifically, the visible light transmittance of the charge generation layer 792 is preferably 40% or higher). The conductivity of the charge generation layer 792 may be lower than that of the conductor 772 or the conductor 788.
The light-emitting device 572 may have a structure illustrated in
The light-emitting device 572 may have a structure illustrated in
<Materials for Light-Emitting Device>
Next, materials that can be used for the light-emitting device 572 will be described.
<<Conductor 772 and Conductor 788>>
For the conductor 772 and the conductor 788, any of the following materials can be used in an appropriate combination as long as the a function of the anode and the cathode can be fulfilled. For example, a metal, an alloy, an electrically conductive compound, a mixture of these, and the like can be appropriately used. Specifically, an In—Sn oxide (also referred to as ITO), an In—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, or an In—W—Zn oxide can be used. In addition, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals. It is also possible to use a Group 1 element or a Group 2 element in the periodic table, which is not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca), or strontium (Sr)), a rare earth metal such as europium (Eu) or ytterbium (Yb), an alloy containing an appropriate combination of any of these elements, graphene, or the like.
<<Hole-Injection Layer 721 and Hole-Transport Layer 722>>
The hole-injection layer 721 injects holes to the EL layer 786 from the conductor 772, which is an anode, or the charge generation layer 792 and contains a material with a high hole-injection property. Here, the EL layer 786 includes the EL layer 786a, the EL layer 786b, the EL layer 786c, and the EL layer 786(1) to the EL layer 786(n).
Examples of the material with a high hole-injection property include transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Alternatively, it is possible to use a phthalocyanine-based compound, an aromatic amine compound, a high molecular compound, or the like.
Alternatively, as the material with a high hole-injection property, a composite material containing a hole-transport material and an acceptor material (electron-accepting material) can be used. In that case, the acceptor material extracts electrons from the hole-transport material, so that holes are generated in the hole-injection layer 721 and the holes are injected into the light-emitting layer 723 through the hole-transport layer 722. Note that the hole-injection layer 721 may be formed to have a single-layer structure using a composite material containing a hole-transport material and an acceptor material (electron-accepting material), or a stacked-layer structure in which a layer containing a hole-transport material and a layer containing an acceptor material (electron-accepting material) are stacked.
The hole-transport layer 722 transports the holes, which are injected from the conductor 772 by the hole-injection layer 721, to the light-emitting layer 723. Note that the hole-transport layer 722 contains a hole-transport material. It is preferable that the HOMO level of the hole-transport material used for the hole-transport layer 722 be equal or close to that of the hole-injection layer 721, in particular.
Examples of the acceptor material used for the hole-injection layer 721 include oxides of a metal belonging to any of Group 4 to Group 8 of the periodic table. Specific examples include molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide. Among these oxides, especially, molybdenum oxide is preferable since it is stable in the air, has a low hygroscopic property, and is easy to handle. Alternatively, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be used.
The hole-transport materials used for the hole-injection layer 721 and the hole-transport layer 722 are preferably substances with a hole mobility of greater than or equal to 10−6 cm2/Vs. Note that other substances can also be used as long as the substances have a hole-transport property higher than an electron-transport property.
As the hole-transport material, a π-electron rich heteroaromatic compound (e.g., a carbazole derivative or an indole derivative), an aromatic amine compound, or the like can be favorably used. As the hole-transport material, a compound having an aromatic amine skeleton, a compound having a carbazole skeleton, a compound having a thiophene skeleton, a compound having a furan skeleton, or the like can be used. In addition, as the hole-transport material, a high molecular compound can be used.
Note that the hole-transport material is not limited to the above examples, and one of various known materials or a combination of some of various known materials can be used as the hole-transport material for the hole-injection layer 721 and the hole-transport layer 722. Note that the hole-transport layer 722 may be formed of a plurality of layers. That is, for example, the hole-transport layer 722 may have a stacked-layer structure of a first hole-transport layer and a second hole-transport layer.
<<Light-Emitting Layer 723>>
The light-emitting layer 723 is a layer containing a light-emitting substance. As the light-emitting substance, a substance whose emission color is blue, violet, bluish violet, green, yellowish green, yellow, orange, red, or the like is appropriately used. Here, when the light-emitting device 572 includes a plurality of EL layers as illustrated in
The light-emitting layer 723 may contain one or more kinds of organic compounds (a host material and an assist material) in addition to a light-emitting substance (guest material). As one or more kinds of the organic compounds, one or both of the hole-transport material and the electron-transport material can be used.
When the light-emitting device 572 has the structure illustrated in
There is no particular limitation on the light-emitting substance that can be used for the light-emitting layer 723, and it is possible to use a light-emitting substance that converts singlet excitation energy into light in the visible light range or a light-emitting substance that converts triplet excitation energy into light in the visible light range. Examples of the light-emitting substance are given below.
Examples of the light-emitting substance that converts singlet excitation energy into light include substances that exhibit fluorescence (fluorescent materials). Specific examples include a pyrene derivative, an anthracene derivative, a triphenylene derivative, a fluorene derivative, a carbazole derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, a pyridine derivative, a pyrimidine derivative, a phenanthrene derivative, and a naphthalene derivative. A pyrene derivative is particularly preferable because it has a high emission quantum yield. The pyrene derivative is a compound effective for meeting the chromaticity of blue in one embodiment of the present invention.
Examples of the light-emitting substance that converts triplet excitation energy into light include a substance that exhibits phosphorescence (phosphorescent material) and a thermally activated delayed fluorescence (TADF) material that exhibits thermally activated delayed fluorescence.
Examples of a phosphorescent material include an organometallic complex, a metal complex (platinum complex), and a rare earth metal complex. These substances exhibit the respective different emission colors (emission peaks) and thus, any of them is selected appropriately as needed.
Examples of a phosphorescent material which emits blue or green light and whose emission spectrum has a peak wavelength at greater than or equal to 450 nm and less than or equal to 570 nm include an organometallic complex having a 4H-triazole skeleton, an organometallic complex having a 1H-triazole skeleton, an organometallic complex having an imidazole skeleton, and an organometallic complex in which a phenylpyridine derivative having an electron-withdrawing group is a ligand.
Examples of a phosphorescent material which emits green or yellow light and whose emission spectrum has a peak wavelength at greater than or equal to 495 nm and less than or equal to 590 nm include an organometallic iridium complex having a pyrimidine skeleton, an organometallic iridium complex having a pyrazine skeleton, an organometallic iridium complex having a pyridine skeleton, an organometallic complex and a rare earth metal complex.
Among the above, organometallic iridium complexes having a pyridine skeleton (particularly, a phenylpyridine skeleton) or a pyrimidine skeleton are compounds effective for meeting the chromaticity of green in one embodiment of the present invention.
Examples of a phosphorescent material which emits yellow or red light and whose emission spectrum has a peak wavelength at greater than or equal to 570 nm and less than or equal to 750 nm include an organometallic complex having a pyrimidine skeleton, an organometallic complex having a pyrazine skeleton, an organometallic complex having a pyridine skeleton, a platinum complex, and a rare earth metal complex.
Among the above, organometallic iridium complexes having a pyrazine skeleton are compounds effective for meeting the chromaticity of red in one embodiment of the present invention. In particular, organometallic iridium complexes having a cyano group (e.g., [Ir(dmdppr-dmCP)2(dpm)]) are preferable because of their high stability.
Note that as the blue-light-emitting substance, a substance whose photoluminescence peak wavelength is greater than or equal to 430 nm and less than or equal to 470 nm, preferably greater than or equal to 430 nm and less than or equal to 460 nm can be used. As the green-light-emitting substance, a substance whose photoluminescence peak wavelength is greater than or equal to 500 nm and less than or equal to 540 nm, preferably greater than or equal to 500 nm and less than or equal to 530 nm can be used. As the red-light-emitting substance, a substance whose photoluminescence peak wavelength is greater than or equal to 610 nm and less than or equal to 680 nm, preferably greater than or equal to 620 nm and less than or equal to 680 nm is used. Note that the photoluminescence may be measured with either a solution or a thin film.
With the parallel use of such compounds and the microcavity effect, the above chromaticity can be achieved more easily. Here, a transflective electrode (a metal thin film portion) that is needed for obtaining the microcavity effect has a thickness of preferably greater than or equal to 20 nm and less than or equal to 40 nm, further preferably greater than 25 nm and less than or equal to 40 nm. Note that the thickness greater than 40 nm possibly reduces the efficiency.
As the organic compounds (the host material and the assist material) used in the light-emitting layer 723, one or more kinds of substances having a larger energy gap than the light-emitting substance (the guest material) can be used. Note that the hole-transport materials listed above and the electron-transport materials given below can be used as the host material and the assist material, respectively.
When the light-emitting substance is a fluorescent material, it is preferable to use, as the host material, an organic compound that has a high energy level in a singlet excited state and has a low energy level in a triplet excited state. For example, an anthracene derivative or a tetracene derivative is preferably used.
When the light-emitting substance is a phosphorescent material, an organic compound having triplet excitation energy (energy difference between a ground state and a triplet excited state) higher than that of the light-emitting substance can be selected as the host material. In that case, it is possible to use a zinc- or aluminum-based metal complex, an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a pyrimidine derivative, a triazine derivative, a pyridine derivative, a bipyridine derivative, a phenanthroline derivative, an aromatic amine, a carbazole derivative, or the like.
When a plurality of organic compounds are used for the light-emitting layer 723, compounds that form an exciplex are preferably mixed with a light-emitting substance. In that case, any of various organic compounds can be used in an appropriate combination; to form an exciplex efficiently, it is particularly preferable to combine a compound that easily accepts holes (hole-transport material) and a compound that easily accepts electrons (electron-transport material). As the hole-transport material and the electron-transport material, specifically, any of the materials described in this embodiment can be used.
The TADF material enables up-conversion of a triplet excited state into a singlet excited state (i.e., reverse intersystem crossing) using a little thermal energy and efficiently emits light from the singlet excited state (efficiently exhibits fluorescence). Thermally activated delayed fluorescence is efficiently obtained under the condition where the energy difference between the triplet excitation level and the singlet excitation level is greater than or equal to 0 eV and less than or equal to 0.2 eV, preferably greater than or equal to 0 eV and less than or equal to 0.1 eV. Note that delayed fluorescence exhibited by the TADF material refers to light emission having the same spectrum as normal fluorescence and an extremely long lifetime. The lifetime is 1×10−6 seconds or longer, preferably 1×10−3 seconds or longer.
Examples of the TADF material include fullerene, a derivative thereof, an acridine derivative such as proflavine, and eosin. Other examples include a metal-containing porphyrin such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (PtCl2OEP). As the TADF material, a heterocyclic compound including a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring can also be used. Note that a substance in which a π-electron rich heteroaromatic ring is directly bonded to a π-electron deficient heteroaromatic ring is particularly preferable because both the donor property of the π-electron rich heteroaromatic ring and the acceptor property of the π-electron deficient heteroaromatic ring are improved and the energy difference between the singlet excited state and the triplet excited state becomes small.
Note that a TADF material can also be used in combination with another organic compound.
<<Electron-Transport Layer 724>>
The electron-transport layer 724 transports electrons, which are injected from the conductor 788 by the electron-injection layer 725, to the light-emitting layer 723. Note that the electron-transport layer 724 contains an electron-transport material. The electron-transport material used for the electron-transport layer 724 is preferably a substance with an electron mobility of higher than or equal to 1×cm2/Vs. Note that any other substance can also be used as long as the substance transports electrons more easily than it transports holes.
Examples of the electron-transport material include metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, and a thiazole ligand; an oxadiazole derivative; a triazole derivative; a phenanthroline derivative; a pyridine derivative; and a bipyridine derivative. In addition, a π-electron deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound can also be used.
The electron-transport layer 724 is not limited to a single layer and may be a stack of two or more layers each containing any of the above substances.
<<Electron-Injection Layer 725>>
The electron-injection layer 725 contains a substance having a high electron-injection property. The electron-injection layer 725 can be formed using an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), or lithium oxide (LiOx). A rare earth metal compound like erbium fluoride (ErF3) can also be used. An electride may also be used for the electron-injection layer 725. An example of the electride includes a substance in which electrons are added at high concentration to calcium oxide-aluminum oxide. Any of the above-described substances used for the electron-transport layer 724 can also be used.
A composite material in which an organic compound and an electron donor (donor) are mixed may also be used for the electron-injection layer 725. Such a composite material is excellent in an electron-injection property and an electron-transport property because electrons are generated in the organic compound by the electron donor. The organic compound here is preferably a material excellent in transporting the generated electrons; specifically, for example, the electron-transport material used for the electron-transport layer 724 (e.g., a metal complex or a heteroaromatic compound) can be used. As the electron donor, a substance showing an electron-donating property with respect to the organic compound is used. Specifically, an alkali metal, an alkaline earth metal, and a rare earth metal are preferable, and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like are given. In addition, an alkali metal oxide and an alkaline earth metal oxide are preferable, and lithium oxide, calcium oxide, barium oxide, and the like are given. Alternatively, a Lewis base such as magnesium oxide can be used. Further alternatively, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.
<<Charge Generation Layer 792>>
The charge generation layer 792 has a function of injecting electrons into the EL layer 786 that is closer to the conductor 772 of the two EL layers 786 in contact with the charge generation layer 792 and injecting holes to the other EL layer 786 that is closer to the conductor 788, when a voltage is applied between the conductor 772 and the conductor 788. For example, in the light-emitting device 572 having the structure illustrated in
When the charge generation layer 792 has a structure in which an electron acceptor is added to a hole-transport material, the electron acceptor can be 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, or the like. Other examples include oxides of metals that belong to Group 4 to Group 8 of the periodic table. Specific examples are vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide.
When the charge generation layer 792 has a structure in which an electron donor is added to an electron-transport material, an alkali metal, an alkaline earth metal, a rare earth metal, or a metal that belongs to Group 2 or Group 13 of the periodic table, or an oxide or carbonate thereof can be used as the electron donor. Specifically, lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, or the like is preferably used. An organic compound such as tetrathianaphthacene may be used as the electron donor.
For fabrication of the light-emitting device 572, a vacuum process such as an evaporation method or a solution process such as a spin coating method or an ink-jet method can be used. In the case of employing an evaporation method, it is possible to use a physical vapor deposition method (PVD method) such as a sputtering method, an ion plating method, an ion beam evaporation method, a molecular beam evaporation method, or a vacuum evaporation method, a chemical vapor deposition method (CVD method), or the like. Specifically, the functional layers (the hole-injection layer, the hole-transport layer, the light-emitting layer, the electron-transport layer, and the electron-injection layer) included in the EL layer and the charge generation layer of the light-emitting device can be formed by an evaporation method (e.g., a vacuum evaporation method), a coating method (e.g., a dip coating method, a die coating method, a bar coating method, a spin coating method, or a spray coating method), a printing method (e.g., an ink-jet method, screen printing (stencil), offset printing (planography), flexography (relief printing), gravure printing, or micro-contact printing), or the like.
Note that materials that can be used for the functional layers (the hole-injection layer, the hole-transport layer, the light-emitting layer, the electron-transport layer, and the electron-injection layer) included in the EL layer and the charge generation layer of the light-emitting device described in this embodiment are not limited to the above materials, and other materials can be used in combination as long as the a function of the layers are fulfilled. For example, a high molecular compound (e.g., an oligomer, a dendrimer, and a polymer), a middle molecular compound (a compound between a low molecular compound and a high molecular compound, with a molecular weight of 400 to 4000), or an inorganic compound (e.g., a quantum dot material) can be used. The quantum dot material may be a colloidal quantum dot material, an alloyed quantum dot material, a core-shell quantum dot material, a core quantum dot material, or the like.
The display device 810 described in this embodiment can be used for the light source included in the detection device 17 described in Embodiment 1. With the use of the display device 810 for the light source described in Embodiment 1, the light-sources can be arranged at high density. Thus, the electronic device of one embodiment of the present invention can obtain information of the user of the electronic device with a high accuracy.
An insulator 1002 is provided over the substrate 1001, and the transistor 1003 is provided over the insulator 1002. An insulator 1004 is provided over the transistor 1003, and an insulator 1005 is provided over the insulator 1004. The light-emitting device 572 and the photoelectric conversion device 1010 are provided over the insulator 1005. The coloring layer 993R and the coloring layer 9931R are provided to have a region overlapping with the light-emitting device 572 or the photoelectric conversion device 1010.
The photoelectric conversion device 1010 has a function of receiving light Lex that comes from the outside of the imaging device and converting it into an electric signal corresponding to the illuminance of the received light Lex.
The light-emitting device 572 preferably has a function of emitting white light and infrared light. Accordingly, light emitted from the light-emitting device 572_1 is emitted to the outside of the imaging device through the coloring layer 993R as red light R. Light emitted from the light-emitting device 572_2 is emitted to the outside of the imaging device through the coloring layer 9931R as infrared light IR. The red light R and the infrared light IR, which are emitted to the outside of the imaging device, strike an object and are reflected and applied to the photoelectric conversion devices 1010. For example, when the imaging device having the structure illustrated in
By having the function of detecting both red light and infrared light, the imaging device can detect, for example, the state of the eyes and surrounding areas of the user of the electronic device of one embodiment of the present invention can be detected with a higher accuracy than an imaging device having a function of detecting only one of red light and infrared light. Consequently, a facial feature of the user of the electronic device of one embodiment of the present invention, such as the user's facial expression, can be recognized with a high accuracy, for example; thus, the electronic device of one embodiment of the present invention can have a function of estimating the degree of fatigue or emotions of the user with a high accuracy, for instance.
Note that when the display device of one embodiment of the present invention includes a photoelectric conversion device, the display device can have the structure illustrated in
The light-emitting device 572 is composed of the conductor 772, the EL layer 786, and the conductor 788. The photoelectric conversion device 1010 is composed of the conductor 772, an active layer 1011, and the conductor 788. The transistor 1003 is electrically connected to the conductor 772.
The active layer 1011 can have a stacked-layer structure in which a p-type semiconductor and an n-type semiconductor are stacked to form a PN junction; or a stacked-layer structure in which a p-type semiconductor, an i-type semiconductor, and an n-type semiconductor are stacked to form a PIN junction, for example.
As the semiconductor used for the active layer 1011, an inorganic semiconductor such as silicon or an organic semiconductor containing an organic compound can be used. In particular, the use of an organic semiconductor material is preferable, in which case the EL layer 786 of the light-emitting device 572 and the active layer 1011 are easily formed by the same vacuum evaporation method, and thus the same manufacturing apparatus can be used.
When an organic semiconductor material is used for the active layer 1011, an electron-accepting organic semiconductor material such as fullerene (e.g., C60 or C70) or its derivative can be used as an n-type semiconductor material. As a p-type semiconductor material, an electron-donating organic semiconductor material such as copper(II) phthalocyanine (CuPc) or tetraphenyldibenzoperiflanthene (DBP) can be used. The active layer 1011 may have a stacked-layer structure (a P-N structure) including an electron-accepting semiconductor material and an electron-donating semiconductor material, or a stacked-layer structure (a P-I-N structure) in which a bulk heterostructure layer formed by co-evaporation of an electron-accepting semiconductor material and an electron-donating semiconductor material is provided between the materials of the P-N structure. Furthermore, a layer functioning as a hole blocking layer or a layer functioning as an electron blocking layer may be provided around (above or below) the P-N structure or the P-I-N structure, in order to inhibit dark current without light illumination.
In the light-emitting device 572, the EL layer 786 is provided over the conductor 772. In the photoelectric conversion device 1010, the active layer 1011 is provided over the conductor 772. The conductor 788 is provided to cover the EL layer 786 and the active layer 1011. Accordingly, the conductor 788 can serve as both the electrode of the light-emitting device 572 and the electrode of the photoelectric conversion device 1010.
When the electronic device of one embodiment of the present invention includes the imaging device having the structure in
When the imaging device included in the electronic device of one embodiment of the present invention has the structure illustrated in
At least part of any of the structure examples, the drawings corresponding thereto, and the like described in this embodiment can be implemented in combination with any of the other structure examples, the other drawings, and the like as appropriate.
At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification as appropriate.
In this embodiment, transistors that can be used in the display device of one embodiment of the present invention will be described.
The transistor 200A includes a metal oxide 230a over a substrate (not illustrated); a metal oxide 230b over the metal oxide 230a; a conductor 242a and a conductor 242b that are apart from each other over the metal oxide 230b; the insulator 280 that is positioned over the conductor 242a and the conductor 242b and has an opening between the conductor 242a and the conductor 242b; a conductor 260 in the opening; an insulator 250 between the conductor 260 and the metal oxide 230b, the conductor 242a, the conductor 242b, and the insulator 280; and a metal oxide 230c between the insulator 250 and the metal oxide 230b, the conductor 242a, the conductor 242b, and the insulator 280. Here, as illustrated in
As illustrated in
As illustrated in
In the transistor 200A, three layers of the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c are stacked in and around the region where the channel is formed (hereinafter also referred to as channel formation region); however, the present invention is not limited thereto. For example, a two-layer structure of the metal oxide 230b and the metal oxide 230c or a stacked-layer structure of four or more layers may be employed. Although the conductor 260 has a stacked-layer structure of two layers in the transistor 200A, the present invention is not limited thereto. For example, the conductor 260 may have a single-layer structure or a stacked-layer structure of three or more layers. Furthermore, each of the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c may have a stacked-layer structure of two or more layers.
For example, when the metal oxide 230c has a stacked-layer structure including a first metal oxide and a second metal oxide over the first metal oxide, the first metal oxide preferably has a composition similar to that of the metal oxide 230b and the second metal oxide preferably has a composition similar to that of the metal oxide 230a.
Here, the conductor 260 functions as a gate electrode of the transistor, and the conductor 242a and the conductor 242b function as a source electrode and a drain electrode. As described above, the conductor 260 is formed to be embedded in the opening of the insulator 280 and the region between the conductor 242a and the conductor 242b. Here, the positions of the conductor 260, the conductor 242a, and the conductor 242b with respect to the opening of the insulator 280 are selected in a self-aligned manner. That is, in the transistor 200A, the gate electrode can be positioned between the source electrode and the drain electrode in a self-aligned manner. Thus, the conductor 260 can be formed without an alignment margin, resulting in a reduction in the footprint of the transistor 200A. Consequently, a display device can achieve high resolution and have a narrow bezel.
In addition, as illustrated in
As illustrated in
The insulator 274 and the insulator 281 functioning as interlayer films are preferably provided over the transistor 200A. Here, the insulator 274 is preferably provided in contact with the top surfaces of the conductor 260, the insulator 250, the insulator 254, the metal oxide 230c, and the insulator 280.
The insulator 222, the insulator 254, and the insulator 274 preferably have a function of inhibiting diffusion of hydrogen (e.g., at least one of hydrogen atoms and hydrogen molecules). For example, the insulator 222, the insulator 254, and the insulator 274 preferably have a lower hydrogen permeability than the insulator 224, the insulator 250, and the insulator 280. Moreover, the insulator 222 and the insulator 254 preferably have a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules). For example, the insulators 222 and 254 preferably have a lower oxygen permeability than the insulator 224, the insulator 250, and the insulator 280.
Here, the insulator 224, the metal oxide 230, and the insulator 250 are separated from the insulator 280 and the insulator 281 by the insulator 254 and the insulator 274. This can inhibit entry of impurities such as hydrogen included in the insulator 280 and the insulator 281 and excess oxygen into the insulator 224, the metal oxide 230, and the insulator 250.
A conductor 240 (a conductor 240a and a conductor 240b) that is electrically connected to the transistor 200A and functions as a plug is preferably provided. Note that an insulator 241 (an insulator 241a and an insulator 241b) is provided in contact with the side surface of the conductor 240 functioning as a plug. In other words, the insulator 241 is provided in contact with the inner wall of an opening in the insulator 254, the insulator 280, the insulator 274, and the insulator 281. Alternatively, a first conductor of the conductor 240 may be provided in contact with the side surface of the insulator 241 and a second conductor of the conductor 240 may be provided on the inner side of the first conductor. Here, the top surface of the conductor 240 and the top surface of the insulator 281 can be at substantially the same level. Although the first conductor of the conductor 240 and the second conductor of the conductor 240 are stacked in the transistor 200A, the present invention is not limited thereto. For example, the conductor 240 may have a single-layer structure or a stacked-layer structure of three or more layers. In the case where a stacked-layer structure is employed, the layers are sometimes distinguished by numbers corresponding to the formation order.
In the transistor 200A, a metal oxide functioning as an oxide semiconductor (hereinafter such a metal oxide is also referred to as an oxide semiconductor) is preferably used for the metal oxide 230 including the channel formation region (the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c). For example, the metal oxide to be the channel formation region of the metal oxide 230 has a band gap of preferably 2 eV or higher, further preferably 2.5 eV or higher, as described above.
As illustrated in
According to one embodiment of the present invention, a display device that includes small-size transistors and has high resolution can be provided. A display device that includes transistors with a high on-state current and achieves high luminance can be provided. A display device that includes fast-response transistors and operates at high speed can be provided. A display device that includes transistors having stable electrical characteristics and is highly reliable can be provided. A display device that includes transistors with a low off-state current and achieves low power consumption can be provided.
The structure of the transistor 200A that can be used in the display device of one embodiment of the present invention will be described in detail.
The conductor 205 is placed so as to include a region overlapped by the metal oxide 230 and the conductor 260. The conductor 205 is preferably embedded in the insulator 216. Here, the top surface of the conductor 205 preferably has favorable planarity. For example, the average surface roughness (Ra) of the top surface of the conductor 205 is less than or equal to 1 nm, preferably less than or equal to 0.5 nm, further preferably less than or equal to 0.3 nm. This achieves favorable planarity of the insulator 224 formed over the conductor 205 and increases the crystallinity of the metal oxide 230b and the metal oxide 230c.
Here, the conductor 260 functions as a first gate (also referred to as top gate) electrode in some cases. The conductor 205 functions as a second gate (also referred to back gate) electrode in some cases. In that case, by changing a potential applied to the conductor 205 independently of a potential applied to the conductor 260, Vth of the transistor 200A can be controlled. In particular, by applying a negative potential to the conductor 205, Vth of the transistor 200A can be higher than 0 V, and its off-state current can be reduced. Thus, a drain current of the transistor 200A at the time when a potential applied to the conductor 260 is 0 V can be smaller in the case where a negative potential is applied to the conductor 205 than in the case where the negative potential is not applied to the conductor 205.
The conductor 205 is preferably larger than the channel formation region of the metal oxide 230. It is particularly preferred that the conductor 205 extend beyond an end portion of the metal oxide 230 that intersects with the channel width direction, as illustrated in
With the above structure, the channel formation region of the metal oxide 230 can be electrically surrounded by electric fields of the conductor 260 functioning as the first gate electrode and electric fields of the conductor 205 functioning as the second gate electrode.
As illustrated in
A conductive material containing tungsten, copper, or aluminum as its main component is preferably used for the conductor 205. Note that the conductor 205 is shown as a single layer but may have a stacked-layer structure, for example, a stack of titanium or titanium nitride and any of the above conductive materials.
In addition, a conductor having a function of inhibiting diffusion of impurities such as a hydrogen atom, a hydrogen molecule, a water molecule, a nitrogen atom, a nitrogen molecule, a nitrogen oxide molecule (e.g., N2O, NO, and NO2), and a copper atom (a conductor through which the above impurities are less likely to pass) may be provided under the conductor 205.
Alternatively, it is preferable to provide a conductor having a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules) (a conductor through which oxygen is less likely to pass). Note that in this specification, a function of inhibiting diffusion of impurities or oxygen means a function of inhibiting diffusion of any one or all of the above impurities and oxygen.
When the conductor having a function of inhibiting oxygen diffusion is provided under the conductor 205, a reduction in conductivity of the conductor 205 due to oxidation of the conductor 205 can be inhibited. As the conductor having a function of inhibiting oxygen diffusion, tantalum, tantalum nitride, ruthenium, or ruthenium oxide is preferably used, for example. The conductor 205 can therefore be a single layer or a stack of the above conductive materials.
The insulator 214 preferably functions as a barrier insulating film for inhibiting impurities such as water or hydrogen from entering the transistor 200A from the substrate side. Accordingly, the insulator 214 is preferably formed using an insulating material having a function of inhibiting diffusion of impurities such as a hydrogen atom, a hydrogen molecule, a water molecule, a nitrogen atom, a nitrogen molecule, a nitrogen oxide molecule (e.g., N2O, NO, and NO2), and a copper atom (an insulating material through which the above impurities are less likely to pass). Alternatively, the insulator 214 is preferably formed using an insulating material having a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules) (an insulating material through which oxygen is less likely to pass).
For example, aluminum oxide or silicon nitride is preferably used for the insulator 214. Accordingly, it is possible to inhibit diffusion of impurities such as water or hydrogen into the transistor 200A from the substrate side through the insulator 214. It is also possible to inhibit diffusion of oxygen contained in the insulator 224 and the like toward the substrate through the insulator 214.
The dielectric constant of each of the insulator 216, the insulator 280, and the insulator 281 functioning as interlayer films is preferably lower than that of the insulator 214. The use of a material having a low dielectric constant for the interlayer film can reduce the parasitic capacitance between wirings. For example, for the insulator 216, the insulator 280, and the insulator 281, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, porous silicon oxide, or the like is used as appropriate.
The insulator 222 and the insulator 224 function as a gate insulator.
Here, it is preferred that the insulator 224 in contact with the metal oxide 230 release oxygen by heating. In this specification and the like, oxygen that is released by heating is referred to as excess oxygen in some cases. For example, silicon oxide or silicon oxynitride can be used as appropriate for the insulator 224. When such an insulator containing oxygen is provided in contact with the metal oxide 230, oxygen vacancies in the metal oxide 230 can be reduced, leading to an improvement in reliability of the transistor 200A.
Specifically, an oxide material that releases some oxygen by heating is preferably used for the insulator 224. An oxide that releases oxygen by heating is an oxide film in which the amount of released oxygen converted into oxygen atoms is greater than or equal to 1.0×1018 atoms/cm3, preferably greater than or equal to 1.0×1019 atoms/cm3, further preferably greater than or equal to 2.0×1019 atoms/cm3 or greater than or equal to 3.0×1020 atoms/cm3 in thermal desorption spectroscopy (TDS) analysis. Note that the temperature of the film surface in the TDS analysis is preferably higher than or equal to 100° C. and lower than or equal to 700° C., or higher than or equal to 100° C. and lower than or equal to 400° C.
As illustrated in
Like the insulator 214 and the like, the insulator 222 preferably functions as a barrier insulating film that inhibits entry of impurities such as water or hydrogen into the transistor 200A from the substrate side. For example, the insulator 222 preferably has a lower hydrogen permeability than the insulator 224. When the insulator 224, the metal oxide 230, the insulator 250, and the like are surrounded by the insulator 222, the insulator 254, and the insulator 274, entry of impurities such as water or hydrogen into the transistor 200A from the outside can be inhibited.
Furthermore, the insulator 222 preferably has a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules) (it is preferred that oxygen is less likely to pass through the insulator 222). For example, the insulator 222 preferably has a lower oxygen permeability than the insulator 224. The insulator 222 preferably has a function of inhibiting diffusion of oxygen and impurities, in which case oxygen contained in the metal oxide 230 is less likely to diffuse toward the substrate. The insulator 222 can also inhibit the conductor 205 from reacting with oxygen contained in the insulator 224 and oxygen contained in the metal oxide 230.
As the insulator 222, an insulator containing one or both of an oxide of aluminum and an oxide of hafnium, which are insulating materials, is preferably used. As the insulator containing one or both of an oxide of aluminum and an oxide of hafnium, aluminum oxide or hafnium oxide is preferably used. Alternatively, an oxide containing aluminum and hafnium (hafnium aluminate) or the like is preferably used. The insulator 222 formed using such a material functions as a layer inhibiting oxygen release from the metal oxide 230 and entry of impurities such as hydrogen into the metal oxide 230 from the periphery of the transistor 200A.
Alternatively, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to the insulator, for example. Alternatively, the insulator may be subjected to nitriding treatment. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked over the insulator.
The insulator 222 may have a single-layer structure or a stacked-layer structure using an insulator containing a high-k material, such as aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As miniaturization and high integration of transistors progress, a problem such as generation of leakage current may arise because of a thinner gate insulator. When a high-k material is used for an insulator functioning as the gate insulator, a gate potential at the time when the transistor operates can be lowered while the physical thickness is maintained.
Note that the insulator 222 and the insulator 224 may each have a stacked-layer structure of two or more layers. In that case, the stacked layers are not necessarily formed of the same material and may be formed of different materials. For example, an insulator similar to the insulator 224 may be provided below the insulator 222.
The metal oxide 230 includes the metal oxide 230a, the metal oxide 230b over the metal oxide 230a, and the metal oxide 230c over the metal oxide 230b. The metal oxide 230a under the metal oxide 230b inhibits diffusion of impurities into the metal oxide 230b from the components formed below the metal oxide 230a. The metal oxide 230c over the metal oxide 230b inhibits diffusion of impurities into the metal oxide 230b from the components formed above the metal oxide 230c.
Note that the metal oxide 230 preferably has a stacked-layer structure of oxide layers with different atomic ratios of metal atoms. Specifically, the atomic ratio of the element Mto the constituent elements in the metal oxide used as the metal oxide 230a is preferably higher than that in the metal oxide used as the metal oxide 230b. The atomic ratio of the element M to In in the metal oxide used as the metal oxide 230a is preferably higher than that in the metal oxide used as the metal oxide 230b. The atomic ratio of In to the element M in the metal oxide used as the metal oxide 230b is preferably higher than that in the metal oxide used as the metal oxide 230a. The metal oxide 230c can be formed using a metal oxide that can be used as the metal oxide 230a or the metal oxide 230b.
The metal oxide 230a, the metal oxide 230b, and the metal oxide 230c preferably have crystallinity, and are particularly preferably formed using CAAC-OS (c-axis-aligned crystalline oxide semiconductor). An oxide having crystallinity, such as a CAAC-OS, has a dense structure with small amounts of impurities and defects (e.g., oxygen vacancies) and high crystallinity. This reduces oxygen extraction from the metal oxide 230b by the source electrode or the drain electrode. Accordingly, oxygen extraction from the metal oxide 230b can be inhibited even when heat treatment is performed. Thus, the transistor 200A is stable against high temperatures in the manufacturing process (i.e., thermal budget).
The energy of the conduction band minimum of each of the metal oxide 230a and the metal oxide 230c is preferably higher than that of the metal oxide 230b. In other words, the electron affinity of each of the metal oxide 230a and the metal oxide 230c is preferably smaller than that of the metal oxide 230b. In that case, the metal oxide 230c is preferably formed using a metal oxide that can be used as the metal oxide 230a. Specifically, the atomic ratio of the element M to the constituent elements in the metal oxide used as the metal oxide 230c is preferably higher than that in the metal oxide used as the metal oxide 230b. The atomic ratio of the element M to In in the metal oxide used as the metal oxide 230c is preferably higher than that in the metal oxide used as the metal oxide 230b. The atomic ratio of In to the element M in the metal oxide used as the metal oxide 230b is preferably higher than that in the metal oxide used as the metal oxide 230c.
Here, the energy level of the conduction band minimum is gradually varied at junction portions of the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c. In other words, the energy level of the conduction band minimum at junction portions of the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c continuously vary or are continuously connected. This can be achieved by decrease in the density of defect states in a mixed layer formed at the interface between the metal oxide 230a and the metal oxide 230b and the interface between the metal oxide 230b and the metal oxide 230c.
Specifically, when the metal oxide 230a and the metal oxide 230b or the metal oxide 230b and the metal oxide 230c contain a common element (as a main component) in addition to oxygen, a mixed layer with a low density of defect states can be formed. For example, in the case where the metal oxide 230b is an In—Ga—Zn oxide, it is preferable to use an In—Ga—Zn oxide, a Ga—Zn oxide, gallium oxide, or the like as each of the metal oxide 230a and the metal oxide 230c. The metal oxide 230c may have a stacked-layer structure. For example, the metal oxide 230c can have a stacked-layer structure of an In—Ga—Zn oxide and a Ga—Zn oxide over the In—Ga—Zn oxide, or a stacked-layer structure of an In—Ga—Zn oxide and gallium oxide over the In—Ga—Zn oxide. In other words, the metal oxide 230c may have a stacked-layer structure of an In—Ga—Zn oxide and an oxide that does not contain In.
Specifically, as the metal oxide 230a, a metal oxide having an atomic ratio of In:Ga:Zn=1:3:4 [atomic ratio] or In:Ga:Zn=1:1:0.5 [atomic ratio] can be used. As the metal oxide 230b, a metal oxide having an atomic ratio of In:Ga:Zn=4:2:3 [atomic ratio] or In:Ga:Zn=3:1:2 [atomic ratio] can be used. As the metal oxide 230c, a metal oxide having an atomic ratio of In:Ga:Zn=1:3:4 [atomic ratio], In:Ga:Zn=4:2:3 [atomic ratio], Ga:Zn=2:1 [atomic ratio], or Ga:Zn=2:5 [atomic ratio] can be used. Specific examples of a stacked-layer structure of the metal oxide 230c include a stacked-layer structure of a layer having an atomic ratio of In:Ga:Zn=4:2:3 [atomic ratio] and a layer having an atomic ratio of Ga:Zn=2:1 [atomic ratio], a stacked-layer structure of a layer having an atomic ratio of In:Ga:Zn=4:2:3 [atomic ratio] and a layer having an atomic ratio of Ga:Zn=2:5 [atomic ratio], and a stacked-layer structure of a layer having an atomic ratio of In:Ga:Zn=4:2:3 [atomic ratio] and gallium oxide.
At this time, the metal oxide 230b serves as a main carrier path. When the metal oxide 230a and the metal oxide 230c have the above structure, the density of defect states at the interface between the metal oxide 230a and the metal oxide 230b and the interface between the metal oxide 230b and the metal oxide 230c can be made low. This reduces the influence of interface scattering on carrier conduction, and the transistor 200A can have a high on-state current and high frequency characteristics. Note that in the case where the metal oxide 230c has a stacked-layer structure, not only the effect of reducing the density of defect state at the interface between the metal oxide 230b and the metal oxide 230c, but also the effect of inhibiting diffusion of the constituent element of the metal oxide 230c toward the insulator 250 can be expected. Specifically, the metal oxide 230c has a stacked-layer structure in which the upper layer is an oxide that does not contain In, whereby the amount of In that would diffuse toward the insulator 250 can be reduced. Since the insulator 250 functions as a gate insulator, the transistor would show poor characteristics when In diffuses into the insulator 250. Thus, the metal oxide 230c having a stacked-layer structure allows the display device to have high reliability.
The metal oxide 230 is preferably formed using a metal oxide functioning as an oxide semiconductor. For example, the metal oxide to be the channel formation region of the metal oxide 230 has a band gap of preferably 2 eV or higher, further preferably 2.5 eV or higher. The use of a metal oxide having a wide band gap can reduce the off-state current of the transistor. The use of such a transistor can provide a display device with low power consumption.
The conductor 242 (the conductor 242a and the conductor 242b) functioning as the source electrode and the drain electrode is provided over the metal oxide 230b. For the conductor 242, it is preferable to use a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum; an alloy containing any of the above metal elements; an alloy containing a combination of the above metal elements; or the like. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, or the like. Tantalum nitride, titanium nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, and an oxide containing lanthanum and nickel are preferable because they are oxidation-resistant conductive materials or materials that retain their conductivity even after absorbing oxygen.
When the conductor 242 is provided in contact with the metal oxide 230, the oxygen concentration of the metal oxide 230 in the vicinity of the conductor 242 sometimes decreases. In addition, a metal compound layer that contains the metal contained in the conductor 242 and the component of the metal oxide 230 is sometimes formed in the metal oxide 230 in the vicinity of the conductor 242. In such cases, the carrier density of the region in the metal oxide 230 in the vicinity of the conductor 242 increases, and the region becomes a low-resistance region.
Here, the region between the conductor 242a and the conductor 242b is formed to overlap with the opening of the insulator 280. In this manner, the conductor 260 can be formed in a self-aligned manner between the conductor 242a and the conductor 242b.
The insulator 250 functions as a gate insulator. The insulator 250 is preferably in contact with a top surface of the metal oxide 230c. For the insulator 250, any of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and porous silicon oxide can be used. In particular, silicon oxide and silicon oxynitride, which have thermal stability, are preferable.
As in the insulator 224, the concentration of impurities such as water or hydrogen in the insulator 250 is preferably reduced. The thickness of the insulator 250 is preferably greater than or equal to 1 nm and less than or equal to 20 nm.
A metal oxide may be provided between the insulator 250 and the conductor 260. The metal oxide preferably has a function of inhibiting oxygen diffusion from the insulator 250 into the conductor 260. Thus, oxidation of the conductor 260 due to oxygen in the insulator 250 can be inhibited.
Note that the metal oxide has a function of part of the gate insulator in some cases. For that reason, when silicon oxide, silicon oxynitride, or the like is used for the insulator 250, the metal oxide is preferably a high-k material with a high dielectric constant. The gate insulator having a stacked-layer structure of the insulator 250 and the metal oxide enables the transistor 200A to be thermally stable and have a high dielectric constant. Accordingly, a gate potential applied during operation of the transistor can be lowered while the physical thickness of the gate insulator is maintained. In addition, the equivalent oxide thickness (EOT) of the insulator functioning as the gate insulator can be reduced.
Specifically, a metal oxide containing one or more of hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like can be used. It is particularly preferable to use an insulator containing an oxide of one or both of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate).
Although the conductor 260 has a two-layer structure in
The conductor 260a is preferably formed using the aforementioned conductive material having a function of inhibiting diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (e.g., N2O, NO, and NO2), and copper atoms. Alternatively, the conductor 260a is preferably formed using a conductive material having a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules).
When the conductor 260a has a function of inhibiting diffusion of oxygen, the conductivity of the conductor 260b can be prevented from being lowered because of oxidization of the conductor 260b due to oxygen in the insulator 250. As a conductive material having a function of inhibiting oxygen diffusion, tantalum, tantalum nitride, ruthenium, or ruthenium oxide is preferably used, for example.
The conductor 260b is preferably formed using a conductive material containing tungsten, copper, or aluminum as its main component. The conductor 260 also functions as a wiring and thus is preferably a conductor having high conductivity. For example, a conductive material containing tungsten, copper, or aluminum as its main component can be used. The conductor 260b may have a stacked-layer structure, for example, a stacked-layer structure of titanium or titanium nitride and the above conductive material.
As illustrated in
The insulator 254 as well as the insulator 214 and the like preferably functions as a barrier insulating film that inhibits impurities such as water or hydrogen from entering the transistor 200A from the insulator 280 side. For example, it is preferable that the insulator 254 preferably have a lower hydrogen permeability than the insulator 224. Furthermore, as illustrated in
Furthermore, the insulator 254 preferably has a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules) (it is preferable that oxygen is less likely to pass through the insulator 254). For example, the insulator 254 preferably has a lower oxygen permeability than the insulator 280 or the insulator 224.
The insulator 254 is preferably formed by a sputtering method. When the insulator 254 is formed by a sputtering method in an oxygen-containing atmosphere, oxygen can be added to a region of the insulator 224 in contact with the insulator 254 and its vicinity. Thus, oxygen can be supplied from the region to the metal oxide 230 through the insulator 224. Here, with the insulator 254 having a function of inhibiting upward oxygen diffusion, diffusion of oxygen from the metal oxide 230 into the insulator 280 can be inhibited. Moreover, with the insulator 222 having a function of inhibiting downward oxygen diffusion, diffusion of oxygen from the metal oxide 230 toward the substrate can be inhibited. In the above manner, oxygen is supplied to the channel formation region of the metal oxide 230. Accordingly, oxygen vacancies in the metal oxide 230 can be reduced, so that the transistor can be prevented from having normally-on characteristics.
As the insulator 254, an insulator containing an oxide of aluminum and/or hafnium is formed, for example. Note that as the insulator containing an oxide of aluminum and/or hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used.
The insulator 224, the insulator 250, and the metal oxide 230 are covered with the insulator 254 having a barrier property against hydrogen, whereby the insulator 280 is isolated from the insulator 224, the metal oxide 230, and the insulator 250 by the insulator 254. This inhibits entry of impurities such as hydrogen from the outside of the transistor 200A, resulting in favorable electrical characteristics and reliability of the transistor 200A.
The insulator 280 is provided over the insulator 224, the metal oxide 230, and the conductor 242 with the insulator 254 placed therebetween. The insulator 280 preferably includes, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, or porous silicon oxide. Silicon oxide and silicon oxynitride are particularly preferable in terms of high thermal stability. A material such as silicon oxide, silicon oxynitride, or porous silicon oxide is preferably used, in which case a region including oxygen that is released by heating can be easily formed.
The concentration of impurities such as water or hydrogen in the insulator 280 is preferably lowered. The top surface of the insulator 280 may be planarized.
The insulator 274, like the insulator 214 or the like, preferably functions as a barrier insulating film that inhibits entry of impurities such as water and hydrogen into the insulator 280. The insulator 274 can be formed using an insulator that can be used as the insulator 214 or the insulator 254, for example.
The insulator 281 functioning as an interlayer film is preferably provided over the insulator 274. As in the insulator 224 or the like, the concentration of impurities such as water and hydrogen in the insulator 281 is preferably reduced.
The conductor 240a and the conductor 240b are provided in openings formed in the insulator 281, the insulator 274, the insulator 280, and the insulator 254. The conductor 240a and the conductor 240b are positioned to face each other with the conductor 260 therebetween. Note that the top surfaces of the conductor 240a and the conductor 240b may be level with the top surface of the insulator 281.
The insulator 241a is provided in contact with the inner wall of the opening in the insulator 281, the insulator 274, the insulator 280, and the insulator 254, and the first conductor of the conductor 240a is formed in contact with the side surface of the insulator 241a. The conductor 242a is positioned on at least part of the bottom of the opening, and thus the conductor 240a is in contact with the conductor 242a. Similarly, the insulator 241b is provided in contact with the inner wall of another opening in the insulator 281, the insulator 274, the insulator 280, and the insulator 254, and the first conductor of the conductor 240b is formed in contact with the side surface of the insulator 241b. The conductor 242b is positioned on at least part of the bottom of the opening, and thus the conductor 240b is in contact with the conductor 242b.
The conductor 240a and the conductor 240b are preferably formed using a conductive material containing tungsten, copper, or aluminum as its main component. The conductor 240a and the conductor 240b may have a stacked-layer structure.
When the conductor 240 has a stacked-layer structure, the aforementioned conductor having a function of inhibiting diffusion of impurities such as water or hydrogen is preferably used for the conductor in contact with the metal oxide 230a, the metal oxide 230b, the conductor 242, the insulator 254, the insulator 280, the insulator 274, and the insulator 281. For example, tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or ruthenium oxide is preferably used. The conductive material having a function of inhibiting diffusion of impurities such as water or hydrogen can be used as a single layer or stacked layers. The use of the conductive material can prevent oxygen added to the insulator 280 from being absorbed by the conductor 240a and the conductor 240b, and prevent impurities such as water or hydrogen from entering the metal oxide 230 through the conductor 240a and the conductor 240b from the components above the insulator 281.
The insulator 241a and the insulator 241b are formed using any of the insulators that can be used for the insulator 254, for example. Since the insulator 241a and the insulator 241b are provided in contact with the insulator 254, impurities such as water and hydrogen in the insulator 280 or the like can be prevented from entering the metal oxide 230 through the conductor 240a and the conductor 240b. Furthermore, oxygen contained in the insulator 280 can be prevented from being absorbed by the conductor 240a and the conductor 240b.
Although not illustrated, a conductor functioning as a wiring may be provided in contact with the top surface of the conductor 240a and the top surface of the conductor 240b. The conductor functioning as a wiring is preferably formed using a conductive material containing tungsten, copper, or aluminum as its main component. The conductor may have a stacked-layer structure, for example, a stack of titanium or titanium nitride and the above conductive material. Note that the conductor may be formed to be embedded in an opening provided in an insulator.
In the transistor 200B, the conductor 242a and the conductor 242b each have a region overlapping with the metal oxide 230c, the insulator 250, and the conductor 260. Thus, the transistor 200B can have a high on-state current. In addition, the transistor 200B can be a transistor that is easy to control.
The conductor 260 functioning as a gate electrode includes the conductor 260a and the conductor 260b over the conductor 260a. The conductor 260a is preferably formed using a conductive material having a function of inhibiting diffusion of impurities such as a hydrogen atom, a hydrogen molecule, a water molecule, and a copper atom. Alternatively, the conductor 260a is preferably formed using a conductive material having a function of inhibiting diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules).
When the conductor 260a has a function of inhibiting oxygen diffusion, the range of choices for the material of the conductor 260b can be expanded. That is, the conductor 260a inhibits oxidation of the conductor 260b, thereby inhibiting the decrease in conductivity.
The insulator 254 is preferably provided to cover the top surface and the side surface of the conductor 260, the side surface of the insulator 250, and the side surface of the metal oxide 230c. Note that the insulator 254 is preferably formed using an insulating material having a function of inhibiting diffusion of oxygen and impurities such as water or hydrogen.
The insulator 254 can inhibit oxidation of the conductor 260. Moreover, the insulator 254 can inhibit diffusion of impurities such as water and hydrogen contained in the insulator 280 into the transistor 200B.
The transistor 200C includes the insulator 250 over the metal oxide 230c, a metal oxide 252 over the insulator 250, the conductor 260 over the metal oxide 252, an insulator 270 over the conductor 260, and an insulator 271 over the insulator 270.
The metal oxide 252 preferably has a function of inhibiting diffusion of oxygen. When the metal oxide 252 that inhibits oxygen diffusion is provided between the insulator 250 and the conductor 260, diffusion of oxygen into the conductor 260 is inhibited. That is, the reduction in the amount of oxygen supplied to the metal oxide 230 can be inhibited. Furthermore, oxidation of the conductor 260 can be inhibited.
Note that the metal oxide 252 may function as part of a gate electrode. For example, an oxide semiconductor that can be used for the metal oxide 230 can be used for the metal oxide 252. In this case, when the conductor 260 is formed by a sputtering method, the metal oxide 252 can have a reduced electric resistance and become a conductor. Such a conductor can be referred to as an oxide conductor (OC) electrode.
Note that the metal oxide 252 may function as part of a gate insulator. Therefore, when silicon oxide, silicon oxynitride, or the like, which has high thermal stability, is used for the insulator 250, a metal oxide that is a high-k material with a high dielectric constant is preferably used as the metal oxide 252. This stacked-layer structure enables the transistor 200C to be thermally stable and have a high dielectric constant. Accordingly, a gate potential that is applied during operation of the transistor can be lowered while the physical thickness is maintained. In addition, the equivalent oxide thickness (EOT) of the insulator functioning as the gate insulator can be reduced.
Although the metal oxide 252 in the transistor 200C is shown as a single layer, the metal oxide 252 may have a stacked-layer structure of two or more layers. For example, a metal oxide functioning as part of a gate electrode and a metal oxide functioning as part of a gate insulator may be stacked.
When the metal oxide 252 included in the transistor 200C functions as a gate electrode, the on-state current of the transistor 200C can be increased without weakening the influence of electric fields from the conductor 260. When the metal oxide 252 functions as a gate insulator, the distance between the conductor 260 and the metal oxide 230 can be maintained owing to the physical thickness of the insulator 250 and the metal oxide 252. Thus, leakage current between the conductor 260 and the metal oxide 230 can be reduced. Consequently, in the transistor 200C having the stacked-layer structure of the insulator 250 and the metal oxide 252, it is easy to adjust the physical distance between the conductor 260 and the metal oxide 230 and the intensity of electric fields applied from the conductor 260 to the metal oxide 230.
Specifically, for the metal oxide 252, a material obtained by lowering the resistance of an oxide semiconductor that can be used for the metal oxide 230 can be used. Alternatively, a metal oxide containing one or more of hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like can be used.
It is particularly preferable to use an insulator containing an oxide of one or both of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate). In particular, hafnium aluminate is preferable because it has higher heat resistance than hafnium oxide and thus is less likely to be crystallized by heat treatment in a later step. Note that the metal oxide 252 is not necessarily provided. Design is appropriately determined in consideration of required transistor characteristics.
The insulator 270 is preferably formed using an insulating material having a function of inhibiting the passage of oxygen and impurities such as water or hydrogen. For example, aluminum oxide or hafnium oxide is preferably used. In that case, oxidization of the conductor 260 due to oxygen from above the insulator 270 can be inhibited. Moreover, entry of impurities such as water or hydrogen from above the insulator 270 into the metal oxide 230 through the conductor 260 and the insulator 250 can be inhibited.
The insulator 271 functions as a hard mask. By provision of the insulator 271, the conductor 260 can be processed to have a side surface that is substantially perpendicular. Specifically, the angle formed by the side surface of the conductor 260 and the surface of the substrate can be greater than or equal to 75° and less than or equal to 100°, preferably greater than or equal to 80° and less than or equal to 95°.
The insulator 271 may be formed using an insulating material having a function of inhibiting the passage of oxygen and impurities such as water or hydrogen so that the insulator 271 also functions as a barrier layer. In this case, the insulator 270 is not necessarily provided.
The insulator 270, the conductor 260, the metal oxide 252, the insulator 250, and the metal oxide 230c are selectively removed using the insulator 271 as a hard mask, whereby their side surfaces can be substantially aligned with each other and the surface of the metal oxide 230b can be partly exposed.
The transistor 200C includes a region 243a and a region 243b on part of the exposed surface of the metal oxide 230b. One of the region 243a and the region 243b functions as a source region, and the other of the region 243a and the region 243b functions as a drain region.
The region 243a and the region 243b can be formed by addition of an impurity element such as phosphorus or boron to the exposed surface of the metal oxide 230b by an ion implantation method, an ion doping method, a plasma immersion ion implantation method, or plasma treatment, for example. In this embodiment and the like, an impurity element refers to an element other than main constituent elements.
Alternatively, the region 243a and the region 243b can be formed in such manner that, after part of the surface of the metal oxide 230b is exposed, a metal film is formed and then heat treatment is performed so that the element contained in the metal film is diffused into the metal oxide 230b.
The electrical resistivity of the regions of the metal oxide 230b to which the impurity element is added decreases. For that reason, the region 243a and the region 243b are sometimes referred to as “impurity regions” or “low-resistance regions”.
The region 243a and the region 243b can be formed in a self-aligned manner by using the insulator 271 and/or the conductor 260 as a mask. Accordingly, the conductor 260 does not overlap the region 243a and/or the region 243b, so that the parasitic capacitance can be reduced. Moreover, an offset region is not formed between the channel formation region and the source-drain region (the region 243a or the region 243b). The formation of the region 243a and the region 243b in a self-aligned manner achieves a higher on-state current, a lower threshold voltage, and a higher operating frequency, for example.
The transistor 200C includes an insulator 272 on the side surfaces of the insulator 271, the insulator 270, the conductor 260, the metal oxide 252, the insulator 250, and the metal oxide 230c. The insulator 272 is preferably an insulator having a low dielectric constant. The insulator 272 is preferably silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, porous silicon oxide, or a resin, for example. In particular, silicon oxide, silicon oxynitride, silicon nitride oxide, or porous silicon oxide is preferably used for the insulator 272 because an excess oxygen region can be easily formed in the insulator 272 in a later step. Silicon oxide and silicon oxynitride are preferable because of their thermal stability. The insulator 272 preferably has a function of diffusing oxygen.
Note that an offset region may be provided between the channel formation region and the source-drain region in order to further reduce the off-state current. The offset region is a region where the electrical resistivity is high and the impurity element is not added. The offset region can be formed by addition of the impurity element after the formation of the insulator 272. In this case, the insulator 272 serves as a mask like the insulator 271 or the like. Thus, the impurity element is not added to the region of the metal oxide 230b overlapped by the insulator 272, so that the electrical resistivity of the region can be kept high.
The transistor 200C also includes the insulator 254 over the insulator 272 and the metal oxide 230. The insulator 254 is preferably formed by a sputtering method. The insulator formed by a sputtering method can be an insulator containing few impurities such as water or hydrogen.
Note that an oxide film formed by a sputtering method may extract hydrogen from the component over which the oxide film is formed. For that reason, the insulator 254 formed by a sputtering method absorbs hydrogen and water from the metal oxide 230 and the insulator 272. This reduces the hydrogen concentration in the metal oxide 230 and the insulator 272.
<Materials for Transistor>
Materials that can be used for the transistor will be described.
<<Substrate>>
As a substrate where the transistor 200A, the transistor 200B, or the transistor 200C is formed, an insulator substrate, a semiconductor substrate, or a conductor substrate can be used, for example. Examples of the insulator substrate include a glass substrate, a quartz substrate, a sapphire substrate, a stabilized zirconia substrate (e.g., an yttria-stabilized zirconia substrate), and a resin substrate. Examples of the semiconductor substrate include a semiconductor substrate of silicon or germanium and a compound semiconductor substrate of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, or gallium oxide. Another example includes a semiconductor substrate in which an insulator region is provided in the above semiconductor substrate, e.g., a silicon on insulator (SOI) substrate. Examples of the conductor substrate include a graphite substrate, a metal substrate, an alloy substrate, and a conductive resin substrate. Other examples include a substrate containing a nitride of a metal, a substrate including an oxide of a metal, an insulator substrate provided with a conductor or a semiconductor, a semiconductor substrate provided with a conductor or an insulator, and a conductor substrate provided with a semiconductor or an insulator. Alternatively, any of these substrates provided with an element may be used. Examples of the element provided over the substrate include a capacitor, a resistor, a switching element, and a memory element.
A flexible substrate may be used as the substrate, and the transistor 200A, the transistor 200B, or the transistor 200C may be provided directly on the flexible substrate. Alternatively, a separation layer may be provided between the substrate and the transistor. The separation layer can be used when part or the whole of the transistor formed over the separation layer is separated from the substrate and transferred to another substrate. Thus, the transistor can be transferred to a substrate having low heat resistance or a flexible substrate.
<<Insulator>>
Examples of an insulator include an insulating oxide, an insulating nitride, an insulating oxynitride, an insulating nitride oxide, an insulating metal oxide, an insulating metal oxynitride, and an insulating metal nitride oxide.
With miniaturization and high integration of transistors, for example, a problem such as generation of leakage current may arise because of a thin gate insulator. When a high-k material is used for an insulator functioning as a gate insulator, the driving voltage of the transistor can be lowered while the physical thickness of the gate insulator is kept. On the other hand, when a material having a low dielectric constant is used for an insulator functioning as an interlayer film, the parasitic capacitance between wirings can be reduced. Accordingly, a material is preferably selected depending on the function of an insulator.
Examples of the insulator having a high dielectric constant include gallium oxide, hafnium oxide, zirconium oxide, an oxide containing aluminum and hafnium, an oxynitride containing aluminum and hafnium, an oxide containing silicon and hafnium, an oxynitride containing silicon and hafnium, and a nitride containing silicon and hafnium.
Examples of the insulator having a low dielectric constant include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, porous silicon oxide, and a resin.
When a transistor including an oxide semiconductor is surrounded by insulators having a function of inhibiting transmission of oxygen and impurities such as hydrogen (e.g., the insulator 214, the insulator 222, the insulator 254, and the insulator 274), the electrical characteristics of the transistor can be stable. An insulator with a function of inhibiting transmission of oxygen and impurities such as hydrogen can be formed to have a single-layer structure or a stacked-layer structure including an insulator containing, for example, boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, or tantalum. Specifically, as the insulator with a function of inhibiting transmission of oxygen and impurities such as hydrogen, a metal oxide such as aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, or tantalum oxide or a metal nitride such as aluminum nitride, aluminum titanium nitride, titanium nitride, silicon nitride oxide, or silicon nitride can be used.
An insulator functioning as a gate insulator preferably includes a region containing oxygen that is released by heating. For example, when silicon oxide or silicon oxynitride that includes a region containing oxygen released by heating is provided in contact with the metal oxide 230, oxygen vacancies in the metal oxide 230 can be compensated.
<<Conductor>>
For the conductor, it is preferable to use a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, lanthanum, and the like; an alloy containing any of the above metal elements; an alloy containing a combination of the above metal elements; or the like. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, or the like. Tantalum nitride, titanium nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, and an oxide containing lanthanum and nickel are preferable because they are oxidation-resistant conductive materials or materials that maintain their conductivity even after absorbing oxygen. In addition, a semiconductor having high electric conductivity, typified by polycrystalline silicon containing an impurity element such as phosphorus, or silicide such as nickel silicide may be used.
Conductors formed using any of the above materials may be stacked. For example, a stacked-layer structure combining a material containing any of the above metal elements and a conductive material containing oxygen may be used. A stacked-layer structure combining a material containing any of the above metal elements and a conductive material containing nitrogen may be used. Further, a stacked-layer structure combining a material containing any of the above metal elements, a conductive material containing oxygen, and a conductive material containing nitrogen may be used.
When a metal oxide is used for the channel formation region of the transistor, the conductor functioning as the gate electrode preferably employs a stacked-layer structure using a material containing any of the above metal elements and a conductive material containing oxygen. In this case, the conductive material containing oxygen is preferably provided on the channel formation region side. When the conductive material containing oxygen is provided on the channel formation region side, oxygen released from the conductive material is easily supplied to the channel formation region.
It is particularly preferable to use, for the conductor functioning as the gate electrode, a conductive material containing oxygen and a metal element contained in the metal oxide in which the channel is formed. A conductive material containing any of the above metal elements and nitrogen may be used. For example, a conductive material containing nitrogen, such as titanium nitride or tantalum nitride, may be used. Indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, or indium tin oxide to which silicon is added may be used. Indium gallium zinc oxide containing nitrogen may be used. With the use of such a material, hydrogen contained in the metal oxide in which the channel is formed can be captured in some cases. Alternatively, hydrogen entering from a surrounding insulator or the like can be captured in some cases.
<<Metal Oxide>>
A metal oxide contains preferably at least indium or zinc and particularly preferably indium and zinc. In addition, aluminum, gallium, yttrium, tin, or the like is preferably contained. Furthermore, one or more elements selected from boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like may be contained.
Here, the case where the metal oxide is an In-M-Zn oxide that contains indium, an element M, and zinc is considered. The element M is aluminum, gallium, yttrium, tin, or the like. Other examples that can be used as the element M include boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium. Note that two or more of the above elements can be used in combination as the element Min some cases.
Note that in this specification and the like, a metal oxide containing nitrogen is also referred to as a metal oxide in some cases. A metal oxide containing nitrogen may be referred to as a metal oxynitride.
[Structure of Metal Oxide]
An oxide semiconductor (metal oxide) is classified into a single crystal oxide semiconductor and a non-single-crystal oxide semiconductor. Examples of a non-single-crystal oxide semiconductor include a CAAC-OS, a polycrystalline oxide semiconductor, an nc-OS (nanocrystalline oxide semiconductor), an a-like OS (amorphous-like oxide semiconductor), and an amorphous oxide semiconductor.
[Impurities]
Here, the influence of impurities in the metal oxide is described. When the metal oxide contains an alkali metal or an alkaline earth metal, defect states are formed and carriers are generated in some cases. Thus, a transistor using a metal oxide containing an alkali metal or an alkaline earth metal in a channel formation region tends to have normally-on characteristics. Therefore, it is preferable to reduce the concentration of an alkali metal or an alkaline earth metal in the metal oxide. Specifically, the concentration of an alkali metal or an alkaline earth metal in the metal oxide, measured by secondary ion mass spectrometry (SIMS), is lower than or equal to 1×1018 atoms/cm3, preferably lower than or equal to 2×1016 atoms/cm3.
Hydrogen contained in a metal oxide reacts with oxygen bonded to a metal atom and forms water. Hence, hydrogen contained in a metal oxide may cause oxygen vacancies in the metal oxide. Entry of hydrogen into the oxygen vacancies generates electrons serving as carriers in some cases. Furthermore, some hydrogen may react with oxygen bonded to a metal atom and generate an electron serving as a carrier. Thus, a transistor including a metal oxide that contains hydrogen tends to have normally-on characteristics.
For this reason, hydrogen in the metal oxide is preferably reduced as much as possible. Specifically, the hydrogen concentration of the metal oxide measured by SIMS is lower than 1×1020 atoms/cm3, preferably lower than 1×1019 atoms/cm3, further preferably lower than 5×1018 atoms/cm3, still further preferably lower than 1×1018 atoms/cm3. When a metal oxide with a sufficiently reduced impurity concentration is used for a channel formation region of a transistor, the transistor can have stable electrical characteristics.
As a metal oxide used for a semiconductor of a transistor, a thin film having high crystallinity is preferably used. With the thin film, the stability or reliability of the transistor can be improved. As the thin film, a thin film of a single crystal metal oxide or a thin film of a polycrystalline metal oxide can be used, for example. However, a high-temperature process or a laser heating process is required to form the thin film of a single crystal metal oxide or the thin film of a polycrystalline metal oxide over a substrate. Thus, the manufacturing cost is increased, and the throughput is decreased.
At least part of any of the structure examples, the drawings corresponding thereto, and the like described in this embodiment can be implemented in combination with any of the other structure examples, the other drawings, and the like as appropriate.
At least part of this embodiment can be implemented in combination with any of the other embodiments described in this specification as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-225818 | Dec 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/061254 | 11/30/2020 | WO |
