Optical device and electronic device

Abstract

The present invention addresses the problem of providing an optical device which is compact and lightweight and which has high light utilization efficiency.　The present invention is an optical device comprising a reflective polarizing plate, a lens, and an optical rotator. By combining the reflective polarizing plate and the optical rotator, it is possible to make a catadioptric system having light utilization efficiency without using a half mirror. As the optical rotator, three Faraday rotators which respectively correspond to R (red light), G (green light), B (blue light) are disposed in series on the optical path and used. As a result, it is possible to impart appropriate respective rotation angles to R, G, and B polarized light. Thus, it is possible to facilitate control of a rotation angle with respect to light of each wavelength.

Description

Optical and Electronic Equipment

[0001] One aspect of the present invention relates to optical and electronic devices.

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

[0003] Note that in this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. A transistor and a semiconductor circuit are examples of a semiconductor device. In addition, a memory device, a display device, an imaging device, and an electronic device may include a semiconductor device.

[0004] Goggle-type devices and eyeglass-type devices have been developed as electronic devices for XR (a collective term for virtual reality (VR), augmented reality (AR), mixed reality (MR), etc.).

[0005] XR equipment such as goggle-type devices is desirably small and thin to improve portability and wearability. Therefore, such electronic devices use thin catadioptric systems designed to have a short focal length. For example, Patent Literature 1 discloses a catadioptric system that reduces losses in transmission and reflection of polarized light and improves light utilization efficiency.

[0006] International Publication No. 2023 / 126740

[0007] Takashi Koida, "High Mobility Transparent Conductive Film," National Institute of Advanced Industrial Science and Technology, AIST Photovoltaic Power Generation Research Results Report 2019, Internet <URL: https: / / unit.aist.go.jp / rpd-envene / PV / ja / results / 2019 / oral / T13.pdf>

[0008] Generally, the catadioptric systems used in XR devices utilize selective reflection of polarized light, resulting in insufficient light utilization efficiency. For this reason, XR devices require increased display brightness. Increasing the brightness of display devices increases power consumption and reduces the reliability of display devices, so optical devices with high light utilization efficiency are desired.

[0009] Therefore, an object of one embodiment of the present invention is to provide an optical device with high light utilization efficiency, a small and lightweight optical device, a small electronic device including the optical device, an electronic device with low power consumption, or a novel electronic device.

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

[0011] One embodiment of the present invention relates to an optical device with high light utilization efficiency and an electronic device including the optical device.

[0012] One aspect of the present invention is an optical device in which a first optical rotator, a second optical rotator, and a third optical rotator are arranged in this order, and the first to third optical rotators have different wavelength dependencies of the rotation angles of the polarization planes, and when linearly polarized light including a first wavelength, a second wavelength, and a third wavelength is incident on the first optical rotator, the polarization planes of the linearly polarized light of the first wavelength, the second wavelength, and the third wavelength emitted from the third optical rotator are identical.

[0013] The rotation angles imparted by the first to third optical rotators to the linearly polarized light of the first, second, and third wavelengths that are transmitted can be 45° + 180 × M (M is an integer).

[0014] The first wavelength may correspond to red light, the second wavelength may correspond to green light, and the third wavelength may correspond to blue light.

[0015] It is preferable to use Faraday rotators for the first to third optical rotators.

[0016] The Faraday rotator preferably includes a magneto-optical crystal and a magnetic field generating source, and the magnetic field generating source preferably includes a coil. The first to third optical rotators preferably have coils with different inductances. The first to third optical rotators may have magneto-optical crystals with different thicknesses.

[0017] It is preferable that the liquid crystal display device has a first reflective polarizer and a second reflective polarizer, and that the first to third rotators are positioned between the first reflective polarizer and the second reflective polarizer.

[0018] Furthermore, it is preferable that the optical element has a first convex lens, which is disposed between the first reflective polarizer and the first optical rotator, and the first convex lens is disposed in contact with the first reflective polarizer.

[0019] It is also preferable that the optical element has a second convex lens, which is disposed between the second reflective polarizer and the third optical rotator, and the second convex lens is disposed in contact with the second reflective polarizer.

[0020] Another aspect of the present invention is an electronic device that includes the optical device described above and an organic EL (Electro Luminescence) panel, where the organic EL panel is arranged so that a display unit intersects perpendicularly with the optical axis 46 of the optical device 30, and the organic EL panel has a lens provided on the organic EL element.

[0021] The organic EL element can be connected to a transistor having a metal oxide in a channel formation region, and the metal oxide is preferably indium oxide.

[0022] According to one embodiment of the present invention, an optical device with high light utilization efficiency can be provided. Alternatively, a small and lightweight optical device can be provided. Alternatively, a small electronic device including the optical device can be provided. Alternatively, an electronic device with low power consumption can be provided. Alternatively, a novel electronic device can be provided.

[0023] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims.

[0024] FIG. 1 is a diagram illustrating an optical device. FIGS. 2A and 2B are diagrams illustrating an optical rotator. FIG. 3A is a diagram illustrating the Verdet constant of a magneto-optical crystal. FIG. 3B is a diagram illustrating the rotation angle of a Faraday rotator. FIG. 4 is a diagram illustrating the rotation angle of a Faraday rotator. FIG. 5 is a diagram illustrating the rotation of the polarization plane of linearly polarized light of each wavelength in each Faraday rotator. FIG. 6 is a diagram illustrating the rotation angle of a Faraday rotator. FIG. 7 is a diagram illustrating the rotation of the polarization plane of linearly polarized light of each wavelength in each Faraday rotator. FIG. 8 is a diagram illustrating the rotation angle of a Faraday rotator. FIG. 9 is a diagram illustrating the rotation of the polarization plane of linearly polarized light of each wavelength in each Faraday rotator. FIGS. 10A, 10B, and 10C are diagrams illustrating Faraday rotators. FIGS. 10D, 10E, and 10F are diagrams illustrating magnetic field generation sources. FIGS. 11A and 11B are diagrams illustrating optical devices. FIGS. 12A and 12B are diagrams illustrating pixels of a display panel. FIGS. 13A, 13B, 13C, 13D, and 13E are diagrams illustrating a display panel. FIGS. 14A and 14B are diagrams illustrating a glasses-type device. FIGS. 15A and 15B are diagrams illustrating a configuration example of a display panel. FIG. 16 is a diagram illustrating a configuration example of a display panel. FIG. 17 is a diagram illustrating a configuration example of a display panel. FIG. 18 is a diagram illustrating a configuration example of a display panel. FIG. 19 is a diagram illustrating a configuration example of a display panel. FIG. 20 is a diagram illustrating a configuration example of a display panel. FIG. 21 is a diagram illustrating a configuration example of a display panel. FIGS. 22A and 22B are diagrams illustrating a transistor. FIGS. 23A and 23B are diagrams illustrating the carrier concentration dependence of hole mobility. FIG. 23C is a cross-sectional view illustrating an indium oxide film.

[0025] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that various modifications in form and detail may be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below. In the configuration of the invention described below, the same parts or parts having similar functions will be designated by the same reference numerals in different drawings, and repeated description thereof may be omitted. Hatching of the same elements constituting the drawings may be omitted or changed as appropriate in different drawings.

[0026] Furthermore, even if a circuit diagram shows a single element, that element may be configured as multiple elements as long as there is no functional problem. For example, multiple transistors operating as switches may be connected in series or parallel. Also, a capacitor may be divided and placed in multiple locations.

[0027] Furthermore, one conductor may have multiple functions, such as wiring, electrode, and terminal, and in this specification, multiple names may be used for the same element. Also, even when elements are shown as being directly connected to each other on a circuit diagram, in reality, the elements may be connected via one or more conductors, and in this specification, such a configuration is also included in the category of direct connection.

[0028] In this specification, "connection" includes, as an example, "electrical connection." Note that the term "electrical connection" is sometimes used to define the connection relationship between circuit elements as a physical entity. Furthermore, "electrical connection" includes "direct connection" and "indirect connection." "A and B are directly connected" means that A and B are connected without the intervention of a circuit element (e.g., a transistor, a switch, etc.; wiring is not considered a circuit element). On the other hand, "A and B are indirectly connected" means that A and B are connected via one or more circuit elements.

[0029] For example, assuming that a circuit including A and B is operating, if there is a time during the operation of the circuit when an electrical signal is exchanged or an interaction of electrical potential occurs between A and B, then it can be defined that "A and B are indirectly connected" as objects. Note that even if there is a time during the operation of the circuit when no electrical signal is exchanged or an interaction of electrical potential occurs between A and B, it can still be defined that "A and B are indirectly connected" as long as there is a time during the operation of the circuit when an electrical signal is exchanged or an interaction of electrical potential occurs between A and B.

[0030] An example of a case where "A and B are indirectly connected" is when A and B are connected via the source and drain of one or more transistors. On the other hand, an example of a case where it cannot be said that "A and B are indirectly connected" is when an insulator is present in the path from A to B. Specifically, there are cases where a capacitive element is connected between A and B, and cases where a gate insulating film of a transistor is present between A and B. Therefore, it cannot be said that "the gate (A) of a transistor and the source or drain (B) of the transistor are indirectly connected."

[0031] Another example of a case where it cannot be said that "A and B are indirectly connected" is when multiple transistors are connected via their sources and drains to the path from A to B, and a constant potential V is supplied to a node between one transistor and another transistor from a power supply, GND, etc.

[0032] Embodiment 1 In this embodiment, an optical device and an electronic device according to one embodiment of the present invention will be described.

[0033] One embodiment of the present invention is an optical device with high light utilization efficiency and an electronic device including the optical device. In the optical device, a catadioptric system can be configured without using a half mirror by using a reflective polarizer and a polarization rotator. Therefore, an optical system with high light utilization efficiency can be achieved without light loss due to a half mirror.

[0034] Furthermore, three Faraday rotators are used as the polarization rotators. It is known that the rotation angle of a Faraday rotator with respect to linearly polarized light is wavelength-dependent. Therefore, in one embodiment of the present invention, first to third Faraday rotators are arranged in series on the optical path so as to correspond to R (red light), G (green light), and B (blue light), respectively. This allows appropriate rotation angles to be applied to the polarized light of R, G, and B, making it easy to control the rotation angle for light of each wavelength.

[0035] The optical device according to one embodiment of the present invention has a configuration in which multiple elements (optical components) are combined. The configuration housed in a housing is also simply called a lens. Furthermore, due to its thin shape, the catadioptric system or the entire optical device is sometimes called a pancake lens.

[0036] FIG. 1 is a perspective view illustrating an electronic device of one embodiment of the present invention, showing a display panel and an optical device included in the electronic device. The display panel 31 is disposed so that the display portion intersects perpendicularly with the optical axis 46 of the optical device 30. Note that in this specification, "perpendicular" refers to a state in which two lines form an angle of 85° or more and 95° or less. Here, one of the two lines refers to the optical axis 46 of the optical device 30, and the other refers to a line parallel to the display portion (display surface). Note that the shapes of the elements shown in FIG. 1 are merely examples.

[0037] The user can view the image displayed on the display panel 31 by bringing the eye 10 close to the optical device 30. The user can view the image with the viewing angle widened by the optical device 30, which gives the user a sense of immersion and realism.

[0038] A liquid crystal panel having liquid crystal elements, an organic EL panel having organic EL elements, an LED panel having micro LEDs, or the like can be used as the display panel 31. In particular, it is preferable to use an organic EL panel which is self-luminous and can easily form a high-definition display unit.

[0039] Although details will be described later, in the optical rotator used in the optical device 30 according to one embodiment of the present invention, the rotation angle of the polarization plane of linearly polarized light is wavelength-dependent. Therefore, it is preferable that the RGB light emitted by the display panel 31 be close to monochromatic light.

[0040] Therefore, when using an organic EL panel, a panel with a color-coded coating method is more suitable than a white light-emitting element + color filter method. The color-coded coating method makes it easier to narrow the emission wavelength, enabling emission of light close to monochromatic light. Furthermore, in organic EL panels, the emission wavelength can also be narrowed by using organic EL elements with a microcavity structure, enabling emission of light close to monochromatic light. When using a liquid crystal panel, the wavelength of each color of RGB light emitted by the liquid crystal panel can be narrowed by using an LED backlight or laser backlight.

[0041] A linear polarizer 32 is disposed on the display surface side of the display panel 31. For example, as shown in Fig. 1, a configuration can be adopted in which the linear polarizer 32 is attached to the display surface of the display panel 31. The linear polarizer 32 can extract linearly polarized light whose vibration direction coincides with the transmission axis from non-polarized light that vibrates in all directions 360° emitted by the display panel 31. Note that the same effect can be obtained even if the display surface of the display panel 31 and the linear polarizer 32 are separated from each other.

[0042] The optical device 30 is a catadioptric optical system, and has a configuration in which a reflective polarizer 41, a lens 42, an optical rotator 43, a reflective polarizer 44, and a lens 45 are arranged in this order. Note that these elements of the optical device 30 are merely examples, and other elements such as lenses, retardation plates, and half mirrors other than those described above may also be provided. Also, some of the elements of the optical device 30 shown in FIG. 1 may not be provided. Note that the linear polarizer 32 described above may also be included in the elements of the optical device 30. Also, the order of some of the elements described above may be reversed.

[0043] The reflective polarizers 41 and 44 reflect linearly polarized light whose vibration direction coincides with the reflection axis and transmit linearly polarized light that is orthogonal to the reflection axis. The reflection axis and transmission axis are orthogonal to each other. The reflective polarizers 41 and 44 may be, for example, wire grid polarizers or dielectric multilayer films.

[0044] The lenses 42 and 45 can be convex lenses. For example, a biconvex lens, a plano-convex lens, or a convex meniscus lens can be used as the convex lens. The lenses 42 and 45 can also be configured by combining a plurality of lenses selected from a biconvex lens, a plano-convex lens, a convex meniscus lens, a biconcave lens, a plano-concave lens, and a concave meniscus lens. The lenses 42 and 45 are not limited to spherical lenses, and may also be aspherical lenses.

[0045] Furthermore, the optical device 30 may be provided with lenses other than the lenses 42 and 45. Furthermore, either the lens 42 or the lens 45 may not be provided. Furthermore, the lenses 42 and 45 may be provided at other positions.

[0046] It is desirable to use resin lenses for the lenses used in the optical device 30 to reduce weight. However, resin has a tendency to cause birefringence. In materials with birefringence, the refractive index differs depending on the direction of vibration of polarized light, resulting in different transmission speeds for different polarized components. Therefore, a phase difference occurs between the polarized components after passing through the material, causing a change in the polarization state. In catadioptric optical systems, when a change in polarization state occurs, light rays that do not travel along the normal optical path are generated. These light rays enter the eye as stray light and are perceived as double images or blurred images.

[0047] The relationship between the polarization state and the optical path will be described later, but for the reasons mentioned above, it is preferable that the lens 42 on the optical path through which polarized light travels back and forth be made of glass, which exhibits almost no birefringence. Also, because humans cannot perceive polarized light, there is no problem even if a resin lens with birefringence is used for the lens 45 placed immediately in front of the eye 10. In other words, it can be said that it is preferable that the lens 45 be made of resin.

[0048] For example, acrylic resin, polycarbonate resin, polyester resin, cycloolefin resin, etc. are known as resins that can be used for lenses, and these can typically be used as the material for lens 45. Note that if a material with sufficiently small birefringence is used, a resin lens can also be used for lenses such as lens 42 that are located on the optical path through which polarized light travels back and forth.

[0049] The optical rotator 43 is provided between the reflective polarizer 41 and the reflective polarizer 44, and the combination of these has an important function in determining the optical path of the catadioptric optical system. The optical rotator 43 can rotate the polarization plane of incident linearly polarized light and emit it. In one embodiment of the present invention, a Faraday rotator is used as the optical rotator 43.

[0050] 2A shows a cross-sectional view illustrating the operation of a Faraday rotator that can be used as the polarization rotator 43. The Faraday rotator has a magneto-optical crystal 43C and a magnetic field source 43M. The magneto-optical crystal 43C may be, for example, a TSAG crystal (Tb ３ Sc ２ Al ３ O １２ ), TGG crystal (Tb ３ Ga ５ O １２ The magnetic field generating source 43M may be a permanent magnet or a coil.

[0051] The magneto-optical crystal 43C is cylindrical, and a magnetic field source 43M is provided to cover the side surface. A magnetic flux MF emitted from the magnetic field source 43M is applied to the magneto-optical crystal 43C, and linearly polarized light PL passing between the two end faces of the magneto-optical crystal 43C that are not covered by the magnetic field source 43M is subjected to an action that rotates the polarization plane.

[0052] 2A, when the incident light is linearly polarized light PL with a polarization plane of 0° and the rotation angle of the magneto-optical crystal 43C is θ, the emitted light that is reflected by the mirror MR and travels back and forth through the magneto-optical crystal 43C (transmits twice) becomes linearly polarized light PL with a polarization plane of 2θ. Note that linearly polarized light PL with a polarization plane of 0° can be extracted by passing unpolarized light NPL through a linear polarizer LP with a transmission axis of 0°.

[0053] Optical elements with optical rotation, such as quartz, are reciprocal, meaning that the direction of rotation of linearly polarized light follows the direction of light propagation. Therefore, when linearly polarized light passes through an optical element, the plane of polarization is rotated, but when it passes through the optical element again after reflection by a mirror, the plane of polarization returns to its original state. In other words, with a reciprocal optical rotator, the rotation of the plane of polarization of linearly polarized light is canceled out when there is an optical path that goes back and forth through the optical element.

[0054] On the other hand, Faraday rotators are non-reciprocal, and the direction of rotation of polarized light follows the direction of the magnetic field, not the direction in which the light propagates. Therefore, if the rotation angle of the polarization plane when linearly polarized light passes through a Faraday rotator is θ, the rotation angle on the round trip will be 2θ. Specific details of the operation will be described later, but in optical device 30 according to one aspect of the present invention, by using a Faraday rotator as polarization rotator 43, an optical system that, in principle, does not generate losses when the polarization state is taken into consideration, can be realized.

[0055] In the Faraday rotator, the rotation angle θ of the linearly polarized light is derived from Equation 1.

[0056]

[0057] where V(λ) is the Verdet constant of the magneto-optical crystal at wavelength λ, B is the magnetic flux density along the direction of light propagation, and L is the length of the magneto-optical crystal. The Verdet constant is a proportional constant that indicates the amount of rotation of the polarization plane of linearly polarized light due to the Faraday effect, and is a value specific to the material.

[0058] It is known that the Verdet constant of a magneto-optical crystal depends on wavelength. Fig. 3A shows a typical value of the Verdet constant of a TGG crystal, which is one of the magneto-optical crystals that can be used in a Faraday rotator. Fig. 3B shows the rotation angle θ in the visible light region of a Faraday rotator using a TGG crystal. The rotation angle θ shown in Fig. 3B is an example calculated assuming a TGG crystal thickness L of 3.818 mm and a magnetic flux density B of 1 T.

[0059] As such, the Verdet constant is highly wavelength-dependent, and when the magnetic flux density B and the length L of the magneto-optical crystal are constant at the above values, for example, the rotation angle θ of blue light (e.g., 458 nm) is approximately 68°, the rotation angle θ of green light (e.g., 534 nm) is approximately 45°, and the rotation angle θ of red light (e.g., 627 nm) is approximately 30°.

[0060] Therefore, while there is no problem when using a single wavelength, when a full-color display is envisioned, the polarization plane will differ depending on the wavelength in the optical path of the catadioptric system. When light with different polarization planes is mixed in the optical path of the catadioptric system, the polarizing plate, which has the function of transmitting or reflecting light, will no longer function ideally. This can result in the generation of light that does not pass through the normal optical path (stray light), which can reduce the visibility of the image.

[0061] Therefore, in one embodiment of the present invention, as shown in the cross-sectional view of FIG. 2B, three Faraday rotators FR λ１ , F.R. λ２ , F.R. λ３ Faraday rotator FR λ１ , F.R. λ２ , F.R. λ３ correspond to one or more wavelengths of blue light, green light, and red light, respectively, and are arranged in order so as to have overlapping regions. λ１ , F.R. λ２ , F.R. λ３ Each of these has the function of giving an appropriate rotation angle to linearly polarized light of each wavelength, so that the polarization planes of the emitted light can be made uniform.

[0062] Here, the Faraday rotator FR λ１ The Faraday rotator FR has a magneto-optical crystal C1 and a magnetic field source M1. λ２ The Faraday rotator FR has a magneto-optical crystal C2 and a magnetic field source M2. λ３ has a magneto-optical crystal C3 and a magnetic field source M3. λ１ , F.R. λ２ , F.R. λ３ Although the examples show that the electrodes are close to each other, they may be spaced apart.

[0063] The magneto-optical crystals C1 to C3 may be made of the same material or different materials. In either case, if the rotation angle θ depends on the wavelength, the rotation angle θ of the linearly polarized light of each wavelength can be adjusted by changing the length L of each of the magneto-optical crystals C1 to C3 and / or by changing the magnetic flux density B applied to each of the crystals.

[0064] When permanent magnets are used as the magnetic field generating source 43M (magnetic field generating sources M1 to M3), the magnetic flux density B can be changed by using permanent magnets with different magnetic forces for each of the magnetic field generating sources M1 to M3. When coils are used as the magnetic field generating source 43M, the magnetic flux density B can be changed by using coils with different inductances for each of the magnetic field generating sources M1 to M3 and by changing the current flowing through each coil.

[0065] Faraday Rotator FR λ１ , F.R. λ２ , F.R. λ３ are arranged in series on the optical path, and have wavelength λ １ The rotation angle of the light θ (λ １ ), wavelength λ ２ The rotation angle of the light θ (λ ２ ), wavelength λ ３ The rotation angle of the light θ (λ ３ ) can be expressed by Equations 2 to 4, respectively.

[0066]

[0067] Here, V １ (λ １ ), V １ (λ ２ ), V １ (λ ３ ), is the wavelength λ of the magneto-optical crystal C1 １ 〜λ ３ The Verdet constants in each of ２ (λ １ ), V ２ (λ ２ ), V ２ (λ ３ ), is the wavelength λ of the magneto-optical crystal C2 １〜λ ３ The Verdet constants in each of ３ (λ １ ), V ３ (λ ２ ), V ３ (λ ３ ), is the wavelength λ of the magneto-optical crystal C3 １ 〜λ ３ Furthermore, B1, B2, and B3 are the magnetic flux densities corresponding to the magnetic field sources M1 to M3, respectively, and L1, L2, and L3 are the lengths corresponding to the magneto-optical crystals C1 to C3, respectively.

[0068] For example, as shown in FIG. λ１ , F.R. λ２ , F.R. λ３ Each of the wavelengths can be configured to have a peak at a desired rotation angle (e.g., 45°) at a desired wavelength (e.g., 458 nm, 534 nm, 627 nm), and to have characteristics such that they do not interfere with each other's wavelength ranges.

[0069] In this case, as shown in FIG. 5, the wavelength λ incident on the polarization rotator 43 １ The light with a polarization plane of 0° (hereinafter referred to as 0° linearly polarized light PL) is λ１ The polarization plane is rotated by +45°, and the Faraday rotator FR λ２ , F.R. λ３ There is no interference (+0°) and the light is emitted from the polarization rotator 43 as light with a polarization plane of 45° (hereinafter referred to as 45° linearly polarized light PL).

[0070] In addition, the wavelength λ incident on the optical rotator 43 ２ The 0° linearly polarized light PL is λ１ There is no interference (+0°), and the Faraday rotator FR λ２ The polarization plane is rotated by +45°, and the Faraday rotator FR λ３ There is no interference (+0°) at the incident angle of 45°, and the light is emitted from the polarization rotator 43 as 45° linearly polarized light PL.

[0071] In addition, the wavelength λ incident on the optical rotator 43 ３ The 0° linearly polarized light PL is λ１ , F.R. λ２There is no interference (+0°), and the Faraday rotator FR λ３ The polarization plane is rotated by +45° at , and the light is emitted from the polarization rotator 43 as 45° linearly polarized light PL.

[0072] That is, the linearly polarized light PL of each wavelength is rotatably rotated by the Faraday rotator FR. λ１ , F.R. λ２ , F.R. λ３ Therefore, even if the rotation angle of the linearly polarized light of the Faraday rotator is wavelength dependent, it is possible to align the rotation angles of the linearly polarized light PL of each wavelength.

[0073] In the above, the Faraday rotator FR λ１ , F.R. λ２ , F.R. λ３ In the above description, the Faraday rotator FR has a characteristic that it does not interfere with each other's wavelength range, but this is not limiting. For example, as shown in FIG. λ１ , F.R. λ２ , F.R. λ３ may have the property of rotating the plane of polarization of linearly polarized light PL of two or more different wavelengths.

[0074] In this case, too, when the desired rotation angle is 45°, the linearly polarized light PL of each wavelength is rotated by the Faraday rotator FR. λ１ , F.R. λ２ , F.R. λ３ The rotation angle may be set to 45° in total or optically equivalent to 45° when the light is transmitted through the optical fiber.

[0075] In FIG. 6, the Faraday rotator FR λ１ is the wavelength λ １ The polarization plane of the linearly polarized light PL (458 nm) is rotated by 27°, and the wavelength λ ２ This example shows an example in which the plane of polarization of linearly polarized light PL (534 nm) is rotated by 5°. λ２ is the wavelength λ １ The polarization plane of the linearly polarized light PL (458 nm) is rotated by 18°, and the wavelength λ ２ The polarization plane of the linearly polarized light PL (534 nm) is rotated by 40°, and the wavelength λ ３This example shows an example in which the plane of polarization of linearly polarized light PL (627 nm) is rotated by 12°. λ３ is the wavelength λ ３ This shows an example in which the plane of polarization of linearly polarized light PL (627 nm) is rotated by 33°.

[0076] In this case, as shown in FIG. 7, the wavelength λ incident on the optical rotator 43 １ The 0° linearly polarized light PL is λ１ The polarization plane rotates by +27°, and the Faraday rotator FR λ２ The polarization plane rotates by +18°, and the Faraday rotator FR λ３ There is no interference (+0°) at the incident angle of 45°, and the light is emitted from the polarization rotator 43 as 45° linearly polarized light PL.

[0077] In addition, the wavelength λ incident on the optical rotator 43 ２ The 0° linearly polarized light PL is λ１ The polarization plane rotates by +5°, and the Faraday rotator FR λ２ The polarization plane rotates by +40°, and FR λ３ There is no interference (+0°) at the incident angle of 45°, and the light is emitted from the polarization rotator 43 as 45° linearly polarized light PL.

[0078] In addition, the wavelength λ incident on the optical rotator 43 ３ The 0° linearly polarized light PL is λ１ No interference, Faraday rotator FR λ２ The polarization plane rotates by +12°, and FR λ３ The polarization plane is rotated by +33° at , and the light is emitted from the polarization rotator 43 as 45° linearly polarized light PL.

[0079] That is, the linearly polarized light PL of each wavelength is rotatably rotated by the Faraday rotator FR. λ１ , F.R. λ２ , F.R. λ３ Therefore, even if the rotation angle of linearly polarized light in the Faraday rotator is wavelength dependent, it is possible to align the rotation angles of light of each wavelength.

[0080] Also, the Faraday rotator FR λ１ , F.R. λ２, F.R. λ３ may have the property of interfering with each other in all wavelength ranges.

[0081] In this case, too, when the desired rotation angle is 45°, the linearly polarized light PL of each wavelength is rotated by the Faraday rotator FR. λ１ , F.R. λ２ , F.R. λ３ The angle may be configured so that a total rotation of 45° occurs when light passes through the lens. Alternatively, the angle may be configured so that the rotation is optically equivalent to 45°. An angle optically equivalent to 45° is an angle obtained by adding a multiple of 180° to 45° (45° + 180° × M (M is an integer)), and examples thereof include -135°, 225°, 405°, and 585°.

[0082] In FIG. 8, the Faraday rotator FR λ１ is the wavelength λ １ The polarization plane of the linearly polarized light PL (458 nm) is rotated by 60°, and the wavelength λ ２ The polarization plane of the linearly polarized light PL (534 nm) is rotated by 19°, and the wavelength λ ３ This example shows an example in which the plane of polarization of linearly polarized light PL (627 nm) is rotated by 4°. λ２ is the wavelength λ １ The polarization plane of linearly polarized light PL (458 nm) is rotated by 177°, and the wavelength λ ２ The polarization plane of linearly polarized light PL (534 nm) is rotated by 66°, and the wavelength λ ３ This example shows an example in which the plane of polarization of linearly polarized light PL (627 nm) is rotated by 10°. λ３ is the wavelength λ １ The polarization plane of the linearly polarized light PL (458 nm) is rotated by 348°, and the wavelength λ ２ The polarization plane of the linearly polarized light PL (534 nm) is rotated by 144°, and the wavelength λ ３ This shows an example in which the plane of polarization of linearly polarized light PL (627 nm) is rotated by 31°.

[0083] In this case, as shown in FIG. 9, the wavelength λ incident on the optical rotator 43 １ The 0° linearly polarized light PL is λ１The polarization plane is rotated by +60°, and the Faraday rotator FR λ２ The polarization plane is rotated by +177°, and the Faraday rotator FR λ３ The polarization plane is rotated by +348° at , and the light is emitted from the polarization rotator 43 as 585° linearly polarized light PL.

[0084] In addition, the wavelength λ incident on the optical rotator 43 ２ The 0° linearly polarized light PL is λ１ The polarization plane rotates by +19°, and the Faraday rotator FR λ２ The polarization plane rotates by +66°, and FR λ３ The polarization plane is rotated by +144° at , and the light is emitted from the polarization rotator 43 as 225° linearly polarized light PL.

[0085] In addition, the wavelength λ incident on the optical rotator 43 ３ The 0° linearly polarized light PL is λ１ The polarization plane rotates by +4°, and the Faraday rotator FR λ２ The polarization plane rotates +10°, and FR λ３ The polarization plane is rotated by +31° at , and the light is emitted from the polarization rotator 43 as 45° linearly polarized light PL.

[0086] That is, the linearly polarized light PL of each wavelength is rotatably rotated by the Faraday rotator FR. λ１ , F.R. λ２ , F.R. λ３ When the light passes through the Faraday rotator, it is rotated by the same total of 45° or the equivalent of 45°. Therefore, even if the rotation angle of linearly polarized light in the Faraday rotator depends on the wavelength, it is possible to align the rotation angles of light of each wavelength.

[0087] In the above, the explanation was given up to the rotation of the polarization plane of linearly polarized light PL being +45° or an angle optically equivalent to +45°. However, as mentioned above, the rotation angle doubles when the light passes back and forth through the Faraday rotator, and therefore, by using a mirror or the like, rotation to +90° or an angle optically equivalent to +90° is possible.

[0088] As described above, in order to give a desired rotation angle to the polarization plane of the linearly polarized light PL of each wavelength, a Faraday rotator FR λ１ , F.R. λ２ , F.R.λ３ Each of these must have the appropriate characteristics as shown in FIG. 4, FIG. 6 or FIG.

[0089] The magnetic flux densities B1, B2, and B3 shown in Equations 2 to 4, and the lengths L1, L2, and L3 corresponding to the magneto-optical crystals C1 to C3, can be treated as variables. Therefore, if the product Bi·Li (i=1, 2, or 3) is considered to be an unknown, the unknown can be uniquely determined from three simultaneous linear equations with three unknowns.

[0090] For example, as shown in the cross-sectional view of FIG. 10A, a Faraday rotator FR λ１ , F.R. λ２ , F.R. λ３ In each of the above, magnetic field sources M1 to M3 and magneto-optical crystals C1 to C3 can be provided individually. In this configuration, the magnetic flux densities B1, B2, B3 and the lengths L1, L2, L3 corresponding to the magneto-optical crystals C1 to C3 can be individually adjusted so as to satisfy the product Bi·Li.

[0091] In this case, the lengths L1, L2, and L3 can all be different values, or any two of them can be the same value. The magnetic flux densities B1, B2, and B3 can all be different values, or any two of them can be the same value. The lengths L1, L2, and L3 corresponding to the magneto-optical crystals C1 to C3 can all be the same value, and the magnetic flux densities B1, B2, and B3 can be adjusted.

[0092] As shown in the cross-sectional view of FIG. 10B, the Faraday rotator FR λ１ , F.R. λ２ , F.R. λ３ A common magnetic field generating source M123 can be provided, and magneto-optical crystals C1 to C3 can be provided separately. In this configuration, the lengths L1, L2, and L3 corresponding to the magneto-optical crystals C1 to C3 can be adjusted so as to satisfy the product Bi·Li.

[0093] As shown in the cross-sectional view of FIG. 10C, the above-mentioned Faraday rotator FR λ１ and Faraday rotator FR λ２ Function of the Faraday Rotator FR λ３ Faraday rotator FR with the functionλ２３ The Faraday rotator FR may be configured as follows: λ２３ has a magneto-optical crystal C23 having the functions of the magneto-optical crystals C2 and C3, and a magnetic field generating source M23. The configuration is not limited to the above, and a Faraday rotator having the functions of any two of the Faraday rotators can also be used. Also, in FIGS. 10A to 10C, the Faraday rotator FR λ１ , F.R. λ２ , F.R. λ３ , F.R. λ２３ The order of steps can be changed as appropriate.

[0094] As shown in Fig. 10D, permanent magnets MT can be used as the magnetic field sources M1, M2, M3, M123, and M23. Since a Faraday rotator requires a certain magnetic flux density even in the optical path at a position far from the magnetic field source, it is preferable that the permanent magnets MT have a strong magnetic force. For example, neodymium magnets, samarium-cobalt magnets, etc. can be used as the permanent magnets MT.

[0095] 10E, coils can be used as the magnetic field generating sources M1, M2, M3, M123, and M23. Coils have the advantage that their shape can be easily adjusted to match the shape of the target object (here, the magneto-optical crystal), and they can be made larger and lighter than permanent magnets. Furthermore, while the magnetic force of permanent magnets changes with temperature and time, coils can vary their magnetic force by adjusting the magnitude of the current, making it possible to generate a constant magnetic force.

[0096] Furthermore, the magnetic flux Φ generated by a coil is proportional to the coil's inductance L and the current I (Φ = LI). Increasing the coil's inductance L increases its ability to store magnetic flux Φ. This means that more magnetic flux Φ is generated by passing the same current, and the magnetic flux density B can be increased.

[0097] The inductance L can be increased by using a magnetic material with high magnetic permeability as the core. Therefore, as shown in Figure 10F, a magnetic material with high magnetic permeability MM may be provided between the coil CL and the region where the magneto-optical crystal is provided. Note that magnetic permeability is an index that indicates how easily magnetic flux can be collected, and the more easily magnetized a material is, such as iron, the higher its value.

[0098] Furthermore, if the coil length is constant, the inductance L of the coil is proportional to the cross-sectional area of ​​the coil and the number of turns of the conductor wire. Therefore, for example, as shown in Figure 10A, if the magnetic field generating sources M1 to M3 can generate different magnetic fields, it can be said that if the cross-sectional area of ​​the coil is constant, it is sufficient to provide each of the magnetic field generating sources M1 to M3 with a coil having a different number of turns of the conductor wire.

[0099] That is, it is preferable to provide each of the magnetic field generating sources M1 to M3 with a coil having a different inductance L. Furthermore, since the magnetic flux density B can be changed by changing the magnitude of the current flowing through each coil, it can be said that adjusting the magnetic flux density B is easier than when a permanent magnet is used.

[0100] Instead of the Faraday rotator, the polarization rotator 43 may be a film cell filled with twisted nematic liquid crystal, or a polymer liquid crystal film filled with twisted nematic liquid crystal.

[0101] 1 shows an example in which several elements constituting the optical device 30 are arranged close to each other, but this is not limiting. The elements constituting the optical device 30 may be divided into several units, and each unit may be arranged separately. In such a case, a support may be provided for each unit. Furthermore, a lens may be used as the support.

[0102] To arrange adjacent elements in close proximity to each other, for example, optical contact can be used to arrange the elements so that they are in contact with each other without using adhesives between them. This reduces the need for adhesives and improves heat and chemical resistance. Furthermore, by eliminating elements with different refractive indices, unnecessary reflections can be prevented.

[0103] Alternatively, it is preferable to bond the elements together using an optical adhesive that has high transmittance for the wavelength of light to be used (for example, the wavelength range of visible light (e.g., 360 nm to 830 nm) or the wavelength range from blue light to red light (e.g., 450 nm to 780 nm)) and does not absorb specific polarized light or exhibit birefringence. With this configuration, properties equivalent to those of optical contact can be obtained.

[0104] Alternatively, one element may be formed on the other element by using a method such as coating or film formation instead of lamination. Alternatively, one element and the other element may be arranged so as to be in contact with each other without providing an adhesive or the like between them. Alternatively, a gap may be provided between the two elements.

[0105] Furthermore, an anti-reflection layer may be provided on the surface of a light-transmitting element that has an interface with air. By preventing unnecessary reflection on the surface of the element (the interface between air and the element), it is possible to improve the light utilization efficiency and suppress the generation of stray light.

[0106] The antireflection layer can be a film-type antireflection coating or a dielectric multilayer coating. For example, it is preferable to provide a dielectric multilayer coating on a curved surface such as the surface of a lens, where it is difficult to attach a film. Furthermore, for elements with flat surfaces, either a film-type antireflection coating or a dielectric multilayer coating may be provided. However, if the element on which the antireflection layer is formed is a resin film, the element may be thermally damaged during the process of forming the dielectric multilayer coating. In such cases, it is preferable to provide a film-type antireflection coating on the element via an adhesive.

[0107] Film-type antireflection coatings include a type that cancels out reflected light by interference, and a moth-eye type that continuously changes the refractive index by fine protrusions formed on the surface. In either type, it is preferable to use a film that is not produced by a stretching method as the base film. Films produced by a stretching method may have optical anisotropy, which may change the polarization state. In terms of small angle dependence and wavelength dependence, it is preferable to use a moth-eye type.

[0108] Next, the overall operation of the optical device 30 having the above-described configuration will be described.

[0109] 11A is a diagram illustrating an optical path of a portion of an optical device according to one embodiment of the present invention, where a portion of the optical path is indicated by a dashed line. For clarity, some elements that are shown adjacent to each other in FIG. 1 are shown separated from each other. Note that the effects of one embodiment of the present invention can also be achieved by arranging the elements as shown in FIG. 11A .

[0110] A portion of the light emitted from the display panel 31 passes through the linear polarizer 32, the reflective polarizer 41, the lens 42, and the optical rotator 43, and is reflected by the reflective polarizer 44. The light reflected by the reflective polarizer 44 passes through the optical rotator 43 and the lens 42, and is reflected again by the reflective polarizer 41. The light reflected by the reflective polarizer 41 passes through the lens 42, the optical rotator 43, the reflective polarizer 44, and the lens 45, and is incident on the eye 10.

[0111] 11B, the reflective polarizer 44 may be provided on the curved surface side of the lens 45. By providing the reflective polarizer 44 on the curved surface side of the lens 45, the reflective surface becomes a concave surface with positive power, thereby increasing the magnification of the display.

[0112] In this case, a portion of the light emitted from the display panel 31 passes through the linear polarizer 32, the reflective polarizer 41, the lens 42, the optical rotator 43, and the lens 45, and is reflected by the reflective polarizer 44. The light reflected by the reflective polarizer 44 passes through the lens 45, the optical rotator 43, and the lens 42, and is reflected again by the reflective polarizer 41. The light reflected by the reflective polarizer 41 passes through the lens 42, the optical rotator 43, the lens 45, and the reflective polarizer 44, and is incident on the eye 10.

[0113] By repeating reflection in this way, the optical path length can be ensured, and therefore an optical system with a short focal length can be achieved. Note that the following description will be given taking the configuration of FIG. 11A as an example.

[0114] First, the polarization state in the optical path of the optical device according to one embodiment of the present invention will be described in detail with reference to Fig. 11A. In Fig. 11A, the polarization state is shown in the upper optical path, and the efficiency of light transmission or reflection in each element is shown in the lower optical path.

[0115] Note that, in this description, the transmission axis of the linear polarizer 32 is set to 0°, but 0° is not an absolute value but a reference value. In other words, the polarization plane of the linearly polarized light extracted by the linear polarizer 32 is treated as 0°. Therefore, for example, 45° linearly polarized light means linearly polarized light whose polarization plane is rotated by 45° from the linearly polarized light extracted by the linear polarizer 32.

[0116] The unpolarized light NPL vibrating in all directions by 360° emitted from the display panel 31 is incident on the linear polarizer 32. The transmission axis of the linear polarizer 32 is 0°, and 0° linearly polarized light PL is emitted from the linear polarizer 32.

[0117] It should be noted that when the display panel 31 is a liquid crystal panel, it is not necessary to provide the linear polarizer 32. The liquid crystal panel has a configuration in which a liquid crystal element is sandwiched between two linear polarizers, and one of the linear polarizers can function as the linear polarizer 32.

[0118] The 0° linearly polarized light PL emitted from the linear polarizer 32 passes through the reflective polarizer 41 with a transmission axis of 0° and the lens 42, and is incident on the optical rotator 43. Here, the optical rotator 43 is the non-reciprocal Faraday rotator described above, and the rotation angle of the polarization plane is 45°. Therefore, the polarization plane of the 0° linearly polarized light PL is rotated by 45° by the optical rotator 43, and the 0° linearly polarized light PL is emitted as 45° linearly polarized light PL.

[0119] The 45° linearly polarized light PL emitted from the optical rotator 43 is reflected by the reflective polarizer 44 with a reflection axis of 45°, and is again incident on the optical rotator 43. The polarization plane of the 45° linearly polarized light PL is rotated by 45° by the optical rotator 43, and the 45° linearly polarized light PL is emitted as 90° linearly polarized light PL.

[0120] The 90° linearly polarized light PL emitted from the optical rotator 43 is reflected by the reflective polarizer 41 with a reflection axis of 90°, and again enters the optical rotator 43. The polarization plane of the 90° linearly polarized light PL is rotated by 45° by the optical rotator 43, and the 90° linearly polarized light PL is emitted as 135° linearly polarized light PL.

[0121] The 135° linearly polarized light PL emitted from the polarization rotator 43 passes through a reflective polarizer 44 with a transmission axis of 135° and a lens 45 .

[0122] In this way, by using linearly polarized light and a nonreciprocal optical rotator, it is possible to selectively reflect or transmit light using a reflective polarizer placed in the optical path, thereby ensuring the optical path length within a limited space and shortening the focal length of optical equipment.

[0123] Next, the light utilization efficiency will be explained. Note that the reflectance and transmittance of each element are assumed to be typical or ideal values.

[0124] When the amount of light emitted from the display panel 31 is 100%, the linear polarizer 32 absorbs light other than 0° linearly polarized light, so the light emitted from the linear polarizer 32 is generally about 40% (x 0.4).

[0125] Thereafter, transmission and reflection are repeated at each element arranged in the optical path, and because the transmittance and reflectance of each are ideally 100% (×1), the light that ultimately emerges from lens 45 is approximately 40%. In other words, optical device 30 according to one embodiment of the present invention does not use a half mirror, which has a large loss, and therefore the loss of light other than at linear polarizer 32 is ideally zero. Therefore, optical device 30 can be said to be an optical device with high light utilization efficiency.

[0126] Furthermore, since the optical device according to one embodiment of the present invention uses only linearly polarized light instead of circularly polarized light, a retardation plate is not required, which reduces the number of optical components constituting the optical device compared to conventional devices, and enables the optical device and electronic device to be manufactured at low cost.

[0127] Next, the configuration of pixels and light-emitting elements of an organic EL panel that can be used as the display panel 31 will be described. Light-emitting elements that can be used in one embodiment of the present invention preferably have an MML (metal maskless) structure in which light-emitting layers are separately formed using a lithography process without using a FMM (fine metal mask). Light-emitting elements with an MML structure can have a higher aperture ratio than light-emitting elements fabricated using an FMM, and can emit light with high brightness or low power consumption. The organic EL panel is configured to further enhance light extraction efficiency by combining light-emitting elements with an MML structure and a convex lens. By combining this organic EL panel with the optical device 30 of one embodiment of the present invention, an XR device with high display quality and low power consumption can be formed.

[0128] 12A is a cross-sectional view corresponding to the cross section B1-B2 shown in the top view of the pixel having the S-stripe arrangement shown in FIG. 12B. The pixel has subpixels 105R, 105G, and 105B. However, the description of subpixel 105R will be omitted here, and only subpixels 105G and 105B will be described. Note that the description of subpixels 105G and 105B can be referred to for the subpixel 105R.

[0129] Here, an example using pixels with an S-stripe arrangement will be described, but the MML structure can be applied to any shape of sub-pixel, including stripe arrangement, delta arrangement, zigzag arrangement, pentile arrangement, diamond arrangement, etc.

[0130] The light emitting element 110G of the sub-pixel 105G and the light emitting element 110B of the sub-pixel 105B are provided on a substrate 161. The substrate 161 includes a support, as well as elements of a pixel circuit.

[0131] It is preferable to use, for example, an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode) as the light-emitting element 110G and the light-emitting element 110B. As the light-emitting substance contained in the EL element, not only an organic compound but also an inorganic compound (such as a quantum dot material) can be used.

[0132] The light-emitting element 110G has a pixel electrode 111G, an organic layer 112G, a common layer 114, and a common electrode 113. The light-emitting element 110B has a pixel electrode 111B, an organic layer 112B, a common layer 114, and a common electrode 113. The common layer 114 and the common electrode 113 are provided in common to the light-emitting element 110G and the light-emitting element 110B.

[0133] The organic layer 112G of the light-emitting element 110G contains a light-emitting organic compound that emits at least green light. The organic layer 112B of the light-emitting element 110B contains a light-emitting organic compound that emits at least blue light. The organic layer 112G and the organic layer 112B can also be called EL layers, and each include at least a layer containing a light-emitting substance (light-emitting layer).

[0134] Hereinafter, when describing matters common to light emitting element 110G and light emitting element 110B, they may be referred to as light emitting element 110. Similarly, when describing matters common to components distinguished by alphabets, such as organic layer 112G and organic layer 112B, they may be described using symbols without the alphabets.

[0135] The organic layer 112 and the common layer 114 can each independently have one or more of an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer. For example, the organic layer 112 can have a stacked structure of a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer from the pixel electrode 111 side, and the common layer 114 can have an electron injection layer.

[0136] The pixel electrode 111G and the pixel electrode 111B are provided for each light-emitting element. The common electrode 113 and the common layer 114 are provided as a continuous layer common to each light-emitting element. A conductive film that is translucent to visible light is used for either the pixel electrode or the common electrode 113, and a conductive film that is reflective is used for the other. By making each pixel electrode translucent and the common electrode 113 reflective, a bottom-emission display device can be obtained. Conversely, by making each pixel electrode reflective and the common electrode 113 translucent, a top-emission display device can be obtained. Incidentally, by making both the pixel electrodes and the common electrode 113 translucent, a dual-emission display device can also be obtained.

[0137] A protective layer 121 is provided on the common electrode 113 to cover the light emitting elements 110G and 110B. The protective layer 121 has a function of preventing impurities such as water from diffusing from above into each light emitting element.

[0138] The edge of the pixel electrode 111 preferably has a tapered shape. When the edge of the pixel electrode 111 has a tapered shape, the organic layer 112 provided along the edge of the pixel electrode 111 can also have an inclined portion. By tapering the edge of the pixel electrode 111, the coverage of the organic layer 112 provided over the edge of the pixel electrode 111 can be improved. Furthermore, by tapering the side surface of the pixel electrode 111, foreign matter (for example, also referred to as dust or particles) during the manufacturing process can be easily removed by a process such as cleaning, which is preferable.

[0139] In this specification and the like, the term "tapered shape" refers to a shape in which at least a part of a side surface of a structure is inclined with respect to a substrate surface. For example, it is preferable that the structure has a region in which the angle between the inclined side surface and the substrate surface (also referred to as the taper angle) is less than 90°.

[0140] The organic layer 112 is processed into an island shape using, for example, a resist mask formed by lithography. As a result, the organic layer 112 has a shape in which the angle between the top surface and the side surface is close to 90 degrees at its edge. On the other hand, an organic film formed using FMM (Fine Metal Mask) or the like tends to be gradually thinner toward the edge, and the top surface is formed in a sloped shape over a range of, for example, 1 μm to 10 μm, making it difficult to distinguish between the top surface and the side surface.

[0141] Between two adjacent light emitting elements, an insulating layer 124, an insulating layer 125 and a resin layer 126 are provided.

[0142] Between two adjacent light-emitting elements, the side surfaces of the organic layers 112 face each other with the resin layer 126 sandwiched therebetween. The resin layer 126 is located between the two adjacent light-emitting elements and is provided so as to fill the ends of each organic layer 112 and the region between the two organic layers 112. The resin layer 126 has a smooth, convex upper surface, and a common layer 114 and a common electrode 113 are provided to cover the upper surface of the resin layer 126.

[0143] The resin layer 126 functions as a planarizing film that fills in the step between two adjacent light-emitting elements. By providing the resin layer 126, it is possible to prevent the common electrode 113 from being separated by the step at the end of the organic layer 112 (also called step disconnection), which would otherwise occur and result in insulation of the common electrode on the organic layer 112.

[0144] Furthermore, the resin layer 126 insulates the organic layers 112 of adjacent light-emitting elements 110 from each other. This reduces leakage current between adjacent light-emitting elements via the organic layers 112, thereby suppressing unnecessary light emission due to crosstalk. This improves the color-developing performance of the display device.

[0145] An insulating layer containing an organic material can be suitably used as the resin layer 126. For example, acrylic resin, polyimide resin, epoxy resin, imide resin, polyamide resin, polyimideamide resin, silicone resin, siloxane resin, benzocyclobutene resin, phenolic resin, precursors of these resins, etc. can be used as the resin layer 126. Alternatively, organic materials such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or alcohol-soluble polyamide resin can be used as the resin layer 126.

[0146] Furthermore, a photosensitive resin can be used as the resin layer 126. A photoresist can be used as the photosensitive resin. The photosensitive resin can be a positive-type material or a negative-type material.

[0147] The resin layer 126 may contain a material that absorbs visible light. For example, the resin layer 126 itself may be made of a material that absorbs visible light, or the resin layer 126 may contain a pigment that absorbs visible light. For example, the resin layer 126 may be a resin that can be used as a color filter that transmits red, blue, or green light and absorbs other light, or a resin that contains carbon black as a pigment and functions as a black matrix.

[0148] The resin layer 126 absorbs light emitted from the light emitting element in an oblique direction, thereby suppressing leakage of light (stray light) from the light emitting element to an adjacent light emitting element via the resin layer 126. This improves the display quality of the display device.

[0149] The insulating layer 125 is provided in contact with the side surface of the organic layer 112. The insulating layer 125 is also provided to cover the upper end portion of the organic layer 112. A portion of the insulating layer 125 is provided in contact with the upper surface of the substrate 161.

[0150] The insulating layer 125 is located between the resin layer 126 and the organic layer 112, and functions as a protective film to prevent the resin layer 126 from contacting the organic layer 112. If the organic layer 112 and the resin layer 126 come into contact with each other, the organic layer 112 may be dissolved by an organic solvent or the like used when forming the resin layer 126. Therefore, by providing the insulating layer 125 between the organic layer 112 and the resin layer 126, it is possible to protect the side surfaces of the organic layer 112.

[0151] The insulating layer 125 can be an insulating layer containing an inorganic material. For example, an inorganic insulating film such as an insulating oxide film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used for the insulating layer 125. The insulating layer 125 may have a single-layer structure or a stacked-layer structure. Examples of oxide insulating films include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, an indium gallium zinc oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide film. Examples of nitride insulating films include a silicon nitride film and an aluminum nitride film. Examples of oxynitride insulating films include a silicon oxynitride film and an aluminum oxynitride film. Examples of nitride oxide insulating films include a silicon nitride oxide film and an aluminum nitride oxide film. In particular, by using a metal oxide film such as an aluminum oxide film or a hafnium oxide film formed by an ALD method, or an inorganic insulating film such as a silicon nitride film or a silicon oxide film, as the insulating layer 125, an insulating layer 125 with few pinholes and excellent protection of the EL layer can be formed.

[0152] In this specification and elsewhere, an oxynitride refers to a material whose composition contains more oxygen than nitrogen, and a nitride oxide refers to a material whose composition contains more nitrogen than oxygen. For example, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, and silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0153] The insulating layer 125 can be formed by a sputtering method, a CVD method, a PLD method, an ALD method, or the like. The insulating layer 125 is preferably formed by an ALD method because it has good coverage.

[0154] Furthermore, a reflective film (e.g., a metal film containing one or more selected from silver, palladium, copper, titanium, aluminum, etc.) may be provided between the insulating layer 125 and the resin layer 126, so that the light emitted from the light-emitting layer is reflected by the reflective film, thereby improving the light extraction efficiency.

[0155] The insulating layer 124 is a portion of a protective layer (also referred to as a mask layer or a sacrificial layer) that protects the organic layer 112 when the organic layer 112 is etched. The insulating layer 124 can be made of the same material as can be used for the insulating layer 125. In particular, it is preferable to use the same material for the insulating layer 124 and the insulating layer 125 because this allows the use of common processing equipment and the like.

[0156] In particular, metal oxide films such as aluminum oxide films and hafnium oxide films, or inorganic insulating films such as silicon nitride films and silicon oxide films formed by the ALD method have few pinholes and are therefore excellent in the function of protecting the EL layer, and can be suitably used for the insulating layer 125 and the insulating layer 124.

[0157] The protective layer 121 may have, for example, a single-layer structure or a stacked structure including at least an inorganic insulating film. Examples of the inorganic insulating film include oxide films or nitride films such as a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a silicon nitride film, an aluminum oxide film, an aluminum oxynitride film, and a hafnium oxide film. Alternatively, the protective layer 121 may be made of a semiconductor material or a conductive material such as indium gallium oxide, indium zinc oxide, indium tin oxide, or indium gallium zinc oxide.

[0158] An insulating layer 104 is provided over the protective layer 121. The insulating layer 104 functions as a planarization layer. The insulating layer 104 can be formed using, for example, a material that can be used for the resin layer 126 or a material that can be used for the insulating layer 125. Note that the insulating layer 104 may not be provided.

[0159] Lenses 102 (lenses 102G and 102B), which are plano-convex lenses, are provided on the insulating layer 104 so as to overlap the light-emitting element 110. In addition, an insulating layer 107 is provided on the lenses 102. The lenses 102 are provided in pairs with the light-emitting element 110. In other words, one lens 102 is provided for each sub-pixel.

[0160] The lens 102 is provided above the light-emitting element 110 (in the direction in which light is emitted). The lens 102 has a convex lens shape, and therefore can act in a direction to converge light. In other words, the lens 102 can suppress divergence of light emitted by the light-emitting element, thereby improving the light extraction efficiency of the display device. The lens 102 can be manufactured using the same material and process as the resin layer 126.

[0161] The insulating layer 107 provided on the lens 102 is an adhesive layer provided between the lens 102 and the substrate 163, and is preferably made of an organic material. For example, an optical adhesive having a refractive index close to that of the glass or film that can be used as the substrate 163 can be used.

[0162] Although the provision of the lens can improve the efficiency of light extraction from the display panel, it is also effective to use a light-emitting element with higher luminous efficiency in order to improve the front brightness of the display panel. In principle, the brightness of tandem organic EL elements improves depending on the number of layers they are stacked in if the current density is the same, and a two-layer tandem organic EL element can achieve twice the brightness of a single-layer light-emitting element.

[0163] Furthermore, because the lifespan of an organic EL element depends on the current density, even if the brightness of a tandem organic EL element is doubled, the lifespan will be equivalent to that of a single organic EL element if the current density is the same. In other words, tandem organic EL elements are an effective technology for increasing the brightness and reliability of organic EL elements.

[0164] The above is a description of an example of the configuration of the light emitting element and its vicinity.

[0165] 13A is a block diagram illustrating a display panel 31 according to one embodiment of the present invention. The display panel 31 includes a pixel array 74, a circuit 75, and a circuit 76. The pixel array 74 includes pixels 40 arranged in columns and rows.

[0166] The pixel 40 can have a plurality of sub-pixels 71. The sub-pixels 71 have the function of emitting light for display. By assigning colors such as R (red), G (green), and B (blue) to the light emitted by the sub-pixels 71, a full-color display can be achieved.

[0167] The subpixel 71 has a light-emitting device that emits unpolarized visible light. It is preferable to use an EL element such as an OLED or QLED as the light-emitting device. Examples of light-emitting materials that the EL element may have include fluorescent materials, phosphorescent materials, thermally activated delayed fluorescence (TADF) materials, and inorganic compounds (such as quantum dot materials). Alternatively, an LED such as a micro LED may be used as the light-emitting device.

[0168] The circuit 75 and the circuit 76 are driver circuits for driving the sub-pixel 71. The circuit 75 can function as a source driver circuit, and the circuit 76 can function as a gate driver circuit. The circuits 75 and 76 can be, for example, shift register circuits.

[0169] The display device 20 may be divided into a plurality of regions vertically and horizontally, and pixels may be driven for each divided region.

[0170] 13B , the circuit 75 and the circuit 76 can be separately disposed below the pixel array 74. In this case, the display device 20 has a laminated structure of a layer 77 and a layer 78, and a plurality of the circuits 75 and a plurality of the circuits 76 are provided on the layer 77, and the pixel array 74 is provided on the layer 78 so as to overlap the circuits 75 and the circuits 76.

[0171] By dividing the circuit 75 and the circuit 76, the pixel array 74 can be driven for each divided area. For example, the pixel array 74 can be operated at different frame rates in parts. The pixel array 74 can be displayed at different resolutions in parts, and can also be made compatible with foveated rendering.

[0172] Furthermore, by providing the driver circuit below the pixel array 74, the wiring length can be shortened and the wiring capacitance can be reduced. This allows for high-speed operation and low power consumption. Furthermore, the display device 20 can have a narrow frame.

[0173] 13B are merely examples and may be changed as appropriate. Part of the circuit 75 and part of the circuit 76 may be formed in the same layer as the pixel array 74. The layer 77 may also include circuits such as a memory circuit, an arithmetic circuit, and a communication circuit.

[0174] In this structure, for example, the layer 77 is provided on a single crystal silicon substrate, the circuits 75 and 76 are formed using transistors having silicon in their channel formation regions (hereinafter referred to as Si transistors), and the pixel circuits included in the pixel array 74 provided in the layer 78 are formed using transistors having metal oxide in their channel formation regions (hereinafter referred to as OS transistors). The OS transistor can be formed using a thin film and can be stacked on the Si transistor.

[0175] 13C , a layer 79 including an OS transistor may be provided between the layer 77 and the layer 78. The layer 79 may include an OS transistor that forms part of a pixel circuit included in the pixel array 74. Alternatively, the layer 79 may include an OS transistor that forms part of the circuit 75 and the circuit 76. Alternatively, the layer 77 may include an OS transistor that forms part of a circuit such as a memory circuit, an arithmetic circuit, or a communication circuit.

[0176] Furthermore, the shape of the display panel 31 when viewed from above is not limited to a rectangle, but may be a circle as shown in Fig. 13D, or a polygon such as an octagon as shown in Fig. 13E.

[0177] 14A is a diagram illustrating an example of a glasses-type device including a display device and an optical device according to one embodiment of the present invention. Here, a combination of the display panel 31 and the optical device 30 shown in FIG. 1 is indicated by a dashed line as a display unit 60.

[0178] The user can view the image displayed on the display panel 31 by bringing their eyes close to the optical device 30 provided on the display surface side of the display panel 31. The user can view the image with the viewing angle widened by the optical device 30, which gives the user a sense of immersion and realism.

[0179] Two sets of display units 60 are incorporated into the housing 50. One display unit 60 is for the right eye and the other display unit 60 is for the left eye, and by displaying images corresponding to the parallax on each display unit 60, a stereoscopic effect of the image can be perceived.

[0180] Furthermore, the housing 50 or the holder 55 may be provided with an input terminal and an output terminal. The input terminal can be connected to a cable for supplying a video signal from a video output device or the like, or power for charging the battery. The output terminal functions as an audio output terminal, for example, and can be connected to earphones, headphones, or the like. Note that if the device is configured to be able to output audio data via wireless communication or if audio is output from an external video output device, the audio output terminal need not be provided.

[0181] Furthermore, a wireless communication module and a storage module may be provided inside the housing 50 or the holder 55. The wireless communication module performs wireless communication, and the content to be viewed can be downloaded and stored in the storage module. This allows the user to view the downloaded content offline.

[0182] 14B , a line-of-sight detection sensor 51 may be provided within the housing 50. The line-of-sight detection sensor 51 detects the position of the gaze by detecting changes in the reflected light due to iris movement using light emitted from a light source 52 provided within the housing 50. The light emitted by the light source 52 is preferably near-infrared light, which has extremely low visibility. For example, operation buttons such as power on, power off, sleep, volume adjustment, channel change, menu display, selection, decision, and back, as well as operation buttons such as video play, stop, pause, fast forward, and fast rewind, may be displayed, and the respective operations can be performed by visually recognizing the operation buttons. Furthermore, the user's level of fatigue may be detected based on the number of blinks, and an alert may be displayed.

[0183] By using the display device of one embodiment of the present invention for a glasses-type device, the electronic device can have low power consumption and high reliability.

[0184] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0185] Embodiment 2 In this embodiment, a structural example of a display panel that can be used as a display device according to one embodiment of the present invention will be described.

[0186] The display panel of this embodiment is a high-definition display panel, and is particularly suitable for use as the display section of VR devices such as head-mounted displays, and wearable devices that can be worn on the head, such as eyeglass-type AR devices.

[0187] 15A shows a perspective view of a display module 280. The display module 280 has a display panel 200A and an FPC 290. Note that the display panel included in the display module 280 is not limited to the display panel 200A, and may be any of display panels 200B to 200H described below.

[0188] The display module 280 has a substrate 291 and a substrate 292. The display module 280 has a display unit 281. The display unit 281 is an area for displaying an image.

[0189] 15B is a perspective view schematically illustrating the configuration on the substrate 291 side. A circuit portion 282, a pixel circuit portion 283 on the circuit portion 282, and a pixel portion 284 on the pixel circuit portion 283 are stacked on the substrate 291. A terminal portion 285 for connecting to the FPC 290 is provided in a portion of the substrate 291 that does not overlap with the pixel portion 284. The terminal portion 285 and the circuit portion 282 are connected via a wiring portion 286 composed of a plurality of wirings.

[0190] The pixel section 284 has a plurality of periodically arranged pixels 284a. An enlarged view of one pixel 284a is shown on the right side of Fig. 15B. The pixel 284a has a light-emitting element 110R that emits red light, a light-emitting element 110G that emits green light, and a light-emitting element 110B that emits blue light.

[0191] The pixel circuit portion 283 has a plurality of pixel circuits 283a arranged periodically. Each pixel circuit 283a is a circuit that controls the light emission of three light-emitting devices included in one pixel 284a. One pixel circuit 283a may be configured to have three circuits that control the light emission of one light-emitting device. For example, the pixel circuit 283a may be configured to have at least one selection transistor, one current control transistor (drive transistor), and a capacitor for each light-emitting device. In this case, a gate signal is input to the gate of the selection transistor, and a source signal is input to the source. This realizes an active matrix display panel.

[0192] The circuit portion 282 includes a circuit for driving each pixel circuit 283a in the pixel circuit portion 283. For example, it is preferable that the circuit portion 282 includes one or both of a gate line driver circuit and a source line driver circuit. In addition, the circuit portion 282 may include at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like. Furthermore, a transistor provided in the circuit portion 282 may constitute a part of the pixel circuit 283a. That is, the pixel circuit 283a may be composed of a transistor included in the pixel circuit portion 283 and a transistor included in the circuit portion 282.

[0193] The FPC 290 functions as wiring for supplying a video signal, a power supply potential, etc. from the outside to the circuit portion 282. An IC may be mounted on the FPC 290.

[0194] The display module 280 can be configured such that one or both of the pixel circuit unit 283 and the circuit unit 282 are provided overlapping below the pixel unit 284, thereby enabling the aperture ratio (effective display area ratio) of the display unit 281 to be extremely high. For example, the aperture ratio of the display unit 281 can be set to 40% or more and less than 100%, preferably 50% or more and 95% or less, and more preferably 60% or more and 95% or less. Furthermore, the pixels 284a can be arranged at an extremely high density, enabling the pixel density of the display unit 281 to be extremely high. For example, it is preferable that the pixels 284a be arranged in the display unit 281 at a pixel density of 2000 ppi or more, preferably 3000 ppi or more, more preferably 5000 ppi or more, and even more preferably 6000 ppi or more, and 20,000 ppi or less, or 30,000 ppi or less.

[0195] Because such a display module 280 has extremely high resolution, it can be suitably used in VR devices such as head-mounted displays, or eyeglass-type AR devices. For example, even in a configuration in which the display unit of the display module 280 is viewed through lenses, the display module 280 has an extremely high-resolution display unit 281, so even if the display unit is enlarged with the lenses, the pixels are not visible, allowing for a highly immersive display. Furthermore, the display module 280 is not limited to this, and can be suitably used in electronic devices with relatively small display units. For example, it can be suitably used in the display unit of a wearable electronic device such as a wristwatch.

[0196] [Display Panel 200A] The display panel 200A shown in FIG. 16 includes a substrate 301, light-emitting elements 110R, 110G, and 110B, a capacitor 240, and a transistor 310.

[0197] Substrate 301 corresponds to substrate 291 in FIGS. 15A and 15B.

[0198] The transistor 310 has a channel formation region in a substrate 301. The substrate 301 can be, for example, a semiconductor substrate such as a single crystal silicon substrate. The transistor 310 includes a part of the substrate 301, a conductive layer 311, a low-resistance region 312, an insulating layer 313, and an insulating layer 314. The conductive layer 311 functions as a gate electrode. The insulating layer 313 is located between the substrate 301 and the conductive layer 311 and functions as a gate insulating layer. The low-resistance region 312 is a region in which the substrate 301 is doped with impurities and functions as one of a source and a drain. The insulating layer 314 is provided to cover a side surface of the conductive layer 311.

[0199] An element isolation layer 315 is provided between two adjacent transistors 310 so as to be embedded in the substrate 301 .

[0200] In addition, an insulating layer 261 is provided to cover the transistor 310 , and a capacitor 240 is provided over the insulating layer 261 .

[0201] The capacitor 240 has a conductive layer 241, a conductive layer 245, and an insulating layer 243 located therebetween. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.

[0202] The conductive layer 241 is provided over the insulating layer 261 and is buried in the insulating layer 254. The conductive layer 241 is connected to one of the source and drain of the transistor 310 by a plug 271 buried in the insulating layer 261. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 interposed therebetween.

[0203] An insulating layer 255a is provided to cover the capacitor 240, an insulating layer 255b is provided over the insulating layer 255a, and an insulating layer 255c is provided over the insulating layer 255b.

[0204] An inorganic insulating film can be preferably used for each of the insulating layers 255a, 255b, and 255c. For example, it is preferable to use a silicon oxide film for the insulating layer 255a and the insulating layer 255c, and a silicon nitride film for the insulating layer 255b. This allows the insulating layer 255b to function as an etching protection film. In this embodiment, an example is shown in which part of the insulating layer 255c is etched to form a recess, but the insulating layer 255c does not necessarily have to have a recess.

[0205] The light-emitting elements 110G and 110B are provided over the insulating layer 255c. Embodiment 1 can be referred to for the structures of the light-emitting elements 110G and 110B.

[0206] In the display panel 200A, a separate light-emitting device is fabricated for each emitted color, resulting in minimal change in chromaticity between light emitted at low and high luminance. Furthermore, because the organic layers 112G and 112B are spaced apart from each other, crosstalk between adjacent subpixels can be suppressed even in a high-resolution display panel. This makes it possible to realize a high-resolution display panel with high display quality.

[0207] An insulating layer 125 and a resin layer 126 are provided in the region between adjacent light emitting elements.

[0208] The pixel electrode 111G and the pixel electrode 111B of the light-emitting element are connected to one of the source and drain of the transistor 310 via a plug 256 embedded in the insulating layers 255a, 255b, 255c and 243, a conductive layer 241 embedded in the insulating layer 254, and a plug 271 embedded in the insulating layer 261. The height of the top surface of the insulating layer 255c and the height of the top surface of the plug 256 are the same or approximately the same. Various conductive materials can be used for the plug.

[0209] Furthermore, a protective layer 121 is provided on the light emitting elements 110G and 110B. An insulating layer 104 and a lens 102 (lenses 102G and 102B) are provided on the protective layer 121. A substrate 163 is bonded to the lens 102 with an insulating layer 107 that functions as an adhesive layer.

[0210] There is no insulating layer covering the upper end of each pixel electrode 111 between two adjacent pixel electrodes 111. This allows the distance between adjacent light-emitting elements to be extremely narrow, resulting in a high-definition or high-resolution display panel.

[0211] 17 has a configuration in which a transistor 310A and a transistor 310B, each having a channel formed in a semiconductor substrate, are stacked. Note that in the following description of the display panel, descriptions of parts that are the same as those of the display panel described above may be omitted.

[0212] The display panel 200B has a structure in which a substrate 301B provided with a transistor 310B, a capacitor 240, and a light-emitting device and a substrate 301A provided with a transistor 310A are bonded together.

[0213] Here, an insulating layer 345 is provided on the lower surface of the substrate 301B, and an insulating layer 346 is provided on the insulating layer 261 provided on the substrate 301A. The insulating layers 345 and 346 function as protective layers and can suppress the diffusion of impurities into the substrates 301B and 301A. The insulating layers 345 and 346 can be made of an inorganic insulating film that can be used for the protective layer 121.

[0214] The substrate 301B is provided with a plug 343 that penetrates the substrate 301B and an insulating layer 345. Here, it is preferable to provide an insulating layer 344 that covers the side surface of the plug 343 and functions as a protective layer.

[0215] Furthermore, in the substrate 301B, a conductive layer 342 is provided below the insulating layer 345. The conductive layer 342 is embedded in the insulating layer 335, and the lower surfaces of the conductive layer 342 and the insulating layer 335 are flattened. The conductive layer 342 is connected to a plug 343.

[0216] On the other hand, in the substrate 301A, a conductive layer 341 is provided on an insulating layer 346. The conductive layer 341 is embedded in the insulating layer 336, and the upper surfaces of the conductive layer 341 and the insulating layer 336 are flattened.

[0217] It is preferable to use the same conductive material for the conductive layers 341 and 342. For example, a metal film containing an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W, or a metal nitride film containing the above elements (titanium nitride film, molybdenum nitride film, tungsten nitride film), etc., can be used. In particular, it is preferable to use copper for the conductive layers 341 and 342. This allows for the application of Cu-Cu (copper-copper) direct bonding technology (technology that achieves electrical conductivity by connecting Cu (copper) pads together).

[0218] [Display Panel 200C] A display panel 200C shown in FIG. 18 has a configuration in which a conductive layer 341 and a conductive layer 342 are joined via a bump 347.

[0219] 18 , by providing a bump 347 between the conductive layer 341 and the conductive layer 342, the conductive layer 341 and the conductive layer 342 can be electrically connected. The bump 347 can be formed using a conductive material containing, for example, gold (Au), nickel (Ni), indium (In), tin (Sn), or the like. Alternatively, for example, solder may be used as the bump 347. An adhesive layer 348 may be provided between the insulating layer 345 and the insulating layer 346. When the bump 347 is provided, the insulating layer 335 and the insulating layer 336 may not be provided.

[0220] [Display Panel 200D] The display panel 200D shown in FIG. 19 differs from the display panel 200A mainly in the configuration of the transistors.

[0221] The transistor 320 is a transistor (OS transistor) in which a metal oxide (also referred to as an oxide semiconductor) is used for a semiconductor layer in which a channel is formed.

[0222] The transistor 320 includes a semiconductor layer 321 , an insulating layer 323 , a conductive layer 324 , a pair of conductive layers 325 , an insulating layer 326 , and a conductive layer 327 .

[0223] Substrate 331 corresponds to substrate 291 in FIGS. 15A and 15B.

[0224] An insulating layer 332 is provided over a substrate 331. The insulating layer 332 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the substrate 331 to the transistor 320 and prevents oxygen from being released from the semiconductor layer 321 toward the insulating layer 332. The insulating layer 332 can be, for example, a film through which hydrogen or oxygen is less likely to diffuse than a silicon oxide film, such as an aluminum oxide film, a hafnium oxide film, or a silicon nitride film.

[0225] A conductive layer 327 is provided over the insulating layer 332, and an insulating layer 326 is provided to cover the conductive layer 327. The conductive layer 327 functions as a first gate electrode of the transistor 320, and part of the insulating layer 326 functions as a first gate insulating layer. An oxide insulating film such as a silicon oxide film is preferably used for at least a portion of the insulating layer 326 that is in contact with the semiconductor layer 321. The top surface of the insulating layer 326 is preferably planarized.

[0226] The semiconductor layer 321 is provided over the insulating layer 326. The semiconductor layer 321 preferably includes a metal oxide (also referred to as an oxide semiconductor) film exhibiting semiconductor characteristics. A pair of conductive layers 325 is provided on and in contact with the semiconductor layer 321 and functions as a source electrode and a drain electrode.

[0227] An insulating layer 328 is provided to cover top surfaces and side surfaces of the pair of conductive layers 325 and side surfaces of the semiconductor layer 321, and an insulating layer 264 is provided over the insulating layer 328. The insulating layer 328 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the insulating layer 264 or the like into the semiconductor layer 321 and prevents oxygen from being released from the semiconductor layer 321. The insulating layer 328 can be an insulating film similar to the insulating layer 332.

[0228] An opening reaching the semiconductor layer 321 is provided in the insulating layer 328 and the insulating layer 264. An insulating layer 323 in contact with the top surface of the semiconductor layer 321 and a conductive layer 324 are buried in the opening. The conductive layer 324 functions as a second gate electrode, and the insulating layer 323 functions as a second gate insulating layer.

[0229] The upper surfaces of the conductive layer 324, the insulating layer 323, and the insulating layer 264 are planarized so that their heights are the same or approximately the same, and insulating layers 329 and 265 are provided to cover them.

[0230] The insulating layer 264 and the insulating layer 265 function as interlayer insulating layers. The insulating layer 329 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the insulating layer 265 or the like to the transistor 320. The insulating layer 329 can be formed using an insulating film similar to the insulating layer 328 and the insulating layer 332.

[0231] The plug 274 connected to one of the pair of conductive layers 325 is provided so as to be embedded in the insulating layer 265, the insulating layer 329, and the insulating layer 264. Here, the plug 274 preferably has a conductive layer 274a covering the side surfaces of the openings of the insulating layer 265, the insulating layer 329, the insulating layer 264, and the insulating layer 328 and part of the top surface of the conductive layer 325, and a conductive layer 274b in contact with the top surface of the conductive layer 274a. In this case, it is preferable to use a conductive material through which hydrogen and oxygen do not easily diffuse as the conductive layer 274a.

[0232] Note that the structure of the transistor included in the display panel of this embodiment is not particularly limited. For example, a planar transistor, a staggered transistor, an inverted staggered transistor, or the like can be used. Furthermore, either a top-gate transistor or a bottom-gate transistor structure may be used. Alternatively, gates may be provided above and below a semiconductor layer in which a channel is formed.

[0233] The transistor 320 has a structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates. The two gates may be connected and the transistor may be driven by supplying the same signal to them. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other.

[0234] The crystallinity of a semiconductor material used for a semiconductor layer of a transistor is not particularly limited, and any of an amorphous semiconductor, a single-crystal semiconductor, and a semiconductor having crystallinity other than single crystal (a microcrystalline semiconductor, a polycrystalline semiconductor, or a semiconductor having a crystalline region in part) may be used. The use of a single-crystal semiconductor or a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0235] The band gap of the metal oxide used for the semiconductor layer of the transistor is preferably 2 eV or more, more preferably 2.5 eV or more. Use of a metal oxide with a wide band gap can reduce the off-state current of the OS transistor.

[0236] The semiconductor layer provided in the OS transistor preferably contains indium, or preferably contains indium, M (M is one or more selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc. In particular, M is preferably one or more selected from aluminum, gallium, yttrium, and tin.

[0237] For example, for a semiconductor layer of an OS transistor, an oxide containing indium (InOx) is preferably used. Alternatively, an oxide containing indium and gallium (also referred to as IGO) is preferably used. Alternatively, an oxide containing indium, gallium, and zinc (also referred to as IGZO) is preferably used. Alternatively, an oxide containing indium, tin, and zinc is preferably used. Alternatively, an oxide containing indium, gallium, tin, and zinc is preferably used.

[0238] Note that an oxide semiconductor used for a semiconductor layer of an OS transistor is preferably formed by a sputtering method or an ALD method. When an oxide semiconductor is formed by a sputtering method, productivity and film density can be increased. When an oxide semiconductor is formed by an ALD method, film coverage can be improved.

[0239] An OS transistor has a wider band gap and a lower carrier concentration than silicon transistors, and can have an extremely small off-state current, which enables charge stored in a capacitor connected in series with the transistor to be held for a long period of time.

[0240] An OS transistor has significantly higher field-effect mobility than a transistor using amorphous silicon. Furthermore, an OS transistor has significantly lower source-drain leakage current (also referred to as off-state current) in an off state, and can hold charge accumulated in a capacitor connected in series with the transistor for a long period of time. Furthermore, the use of an OS transistor can reduce the power consumption of a display panel.

[0241] Furthermore, to increase the emission luminance of a light-emitting device included in a pixel circuit, it is necessary to increase the amount of current flowing through the light-emitting device. To achieve this, it is necessary to increase the source-drain voltage of a driving transistor included in the pixel circuit. Since an OS transistor has a higher source-drain withstand voltage than a Si transistor, a high voltage can be applied between the source and drain of the OS transistor. Therefore, by using an OS transistor as the driving transistor included in a pixel circuit, it is possible to increase the amount of current flowing through the light-emitting device and increase the emission luminance of the light-emitting device.

[0242] Furthermore, when the transistor operates in the saturation region, the change in source-drain current of an OS transistor is smaller than that of a Si transistor in response to a change in gate-source voltage. Therefore, by using an OS transistor as a driving transistor included in a pixel circuit, the current flowing between the source and drain can be precisely controlled by changing the gate-source voltage, thereby controlling the amount of current flowing through the light-emitting device. This allows for a larger number of gray levels to be displayed in the pixel circuit.

[0243] Furthermore, in terms of the saturation characteristics of the current that flows when a transistor operates in the saturation region, an OS transistor can pass a more stable current (saturation current) than a Si transistor, even when the source-drain voltage gradually increases. Therefore, by using an OS transistor as a driving transistor, a stable current can be passed through a light-emitting device, even when the current-voltage characteristics of an EL device vary. In other words, when an OS transistor operates in the saturation region, the source-drain current of the OS transistor remains almost unchanged even when the source-drain voltage increases, thereby stabilizing the light-emitting luminance of the light-emitting device.

[0244] As described above, by using an OS transistor for a driving transistor included in a pixel circuit, it is possible to achieve "reduced power consumption," "increased light emission luminance," "multiple gray levels," "suppressed variations in light-emitting devices," and the like.

[0245] [Display Panel 200F] A display panel 200F shown in FIG. 20 has a stacked structure of a transistor 310 in which a channel is formed in a substrate 301 and a transistor 320 in which a channel is formed and a semiconductor layer containing metal oxide is formed.

[0246] An insulating layer 261 is provided to cover the transistor 310, and a conductive layer 251 is provided over the insulating layer 261. An insulating layer 262 is provided to cover the conductive layer 251, and a conductive layer 252 is provided over the insulating layer 262. The conductive layers 251 and 252 each function as wirings. An insulating layer 263 and an insulating layer 332 are provided to cover the conductive layer 252, and the transistor 320 is provided over the insulating layer 332. An insulating layer 265 is provided to cover the transistor 320, and a capacitor 240 is provided over the insulating layer 265. The capacitor 240 and the transistor 320 are electrically connected by a plug 274.

[0247] The transistor 320 can be used as a transistor that forms a pixel circuit. The transistor 310 can be used as a transistor that forms a pixel circuit or a driver circuit (gate line driver circuit, source line driver circuit) that drives the pixel circuit. The transistors 310 and 320 can be used as transistors that form various circuits such as an arithmetic circuit or a memory circuit.

[0248] With this configuration, not only pixel circuits but also driving circuits etc. can be formed directly below the light-emitting device, which makes it possible to make the display panel smaller than when driving circuits are provided around the periphery of the display area.

[0249] [Display Panel 200G] The display panel 200G shown in Fig. 21 has a configuration in which the transistor 320 of the display panel 200F shown in Fig. 20 is replaced with a transistor 320A (vertical transistor). Note that the configuration in which the transistor 320 is replaced with the transistor 320A can also be applied to the display panel 200D shown in Fig. 19.

[0250] 22A shows a cross-sectional view of the transistor 320A in the XZ plane, and FIG. 22B shows a cross-sectional view of the transistor 320A in the XY plane including the wiring 440.

[0251] The transistor 320A includes an oxide semiconductor 470, an insulator 430, and a conductor 420. The oxide semiconductor 470 functions as a semiconductor layer, the insulator 430 functions as a gate insulator, and the conductor 420 functions as a gate electrode. The wiring 450 has a region that functions as one of a source electrode and a drain electrode of the transistor 320A. The wiring 440 has a region that functions as the other of the source electrode and the drain electrode of the transistor 320A.

[0252] An opening 490 is provided through the wiring 440 and the insulator 480, reaching the wiring 450. The opening 490 has a columnar shape with a substantially circular upper surface. This structure allows for miniaturization or high integration of memory cells. Note that the side surface of the opening 490 is preferably perpendicular to the upper surface of the wiring 450.

[0253] At least a part of the oxide semiconductor 470 is disposed in the opening 490. Note that the oxide semiconductor 470 has a region in contact with the top surface of the wiring 450, a region in contact with the side surface of the wiring 440, and a region in contact with the side surface of the insulator 480 in the opening 490.

[0254] The insulator 430 is disposed so that at least a portion thereof covers the opening 490. The conductor 420 is disposed so that at least a portion thereof is located in the opening 490. Note that the conductor 420 is preferably provided so as to fill the opening 490, and preferably has a substantially circular shape in top view in order to increase the degree of integration.

[0255] As illustrated in FIG. 22A, the oxide semiconductor 470 includes a region 470i and regions 470na and 470nb that are provided to sandwich the region 470i.

[0256] The region 470na is a region of the oxide semiconductor 470 that is in contact with the wiring 450. At least a part of the region 470na functions as one of the source region and the drain region of the transistor 320A. The region 470nb is a region of the oxide semiconductor 470 that is in contact with the wiring 440. At least a part of the region 470nb functions as the other of the source region and the drain region of the transistor 320A. As shown in FIG. 22B , the wiring 440 is in contact with the entire periphery of the oxide semiconductor 470. Therefore, the other of the source region and the drain region of the transistor 320A can be formed along the entire periphery of a portion of the oxide semiconductor 470 that is formed in the same layer as the wiring 440.

[0257] The region 470i is a region sandwiched between the regions 470na and 470nb in the oxide semiconductor 470. At least part of the region 470i functions as a channel formation region of the transistor 320A. That is, the channel formation region of the transistor 320A is formed in a part of the oxide semiconductor 470 located between the wiring 450 and the wiring 440. It can also be said that the channel formation region of the transistor 320A is located in a region of the oxide semiconductor 470 that is in contact with the insulator 480 or in a region in the vicinity of the insulator 480.

[0258] The channel length of the transistor 320A is the distance between the source region and the drain region. In other words, the channel length of the transistor 320A is determined by the thickness of the insulator 480 on the wiring 450. In FIG. 22A , the channel length L of the transistor 320A is indicated by a dashed double-headed arrow. The channel length L is the distance between the end of the region where the oxide semiconductor 470 and the wiring 450 contact each other and the end of the region where the oxide semiconductor 470 and the wiring 440 contact each other in a cross-sectional view. In other words, the channel length L corresponds to the length of the side surface of the insulator 480 on the opening 490 side in a cross-sectional view.

[0259] In a planar transistor, the channel length is limited by the exposure limit of photolithography, making further miniaturization difficult. However, in one embodiment of the present invention, the channel length can be set by the film thickness of the insulator 480. Therefore, the channel length of the transistor 320A can be made into an extremely fine structure that is equal to or less than the exposure limit of photolithography (for example, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less, and 1 nm or more, or 5 nm or more). This allows the on-state current of the transistor 320A to be increased.

[0260] Furthermore, as described above, the channel formation region, the source region, and the drain region can be formed in the opening 490. This allows the area occupied by the transistor 320A to be reduced compared to a conventional transistor in which the channel formation region, the source region, and the drain region are provided separately on the XY plane, thereby increasing the pixel density.

[0261] A transistor having a channel formation region along the side surface of the insulator 480 in the opening 490 is also called a vertical transistor.

[0262] 22B , the oxide semiconductor 470, the insulator 430, and the conductor 420 are arranged concentrically in the XY plane including the channel formation region of the oxide semiconductor 470. Therefore, the side surface of the conductor 420 located at the center faces the side surface of the oxide semiconductor 470 with the insulator 430 interposed therebetween. That is, the entire periphery of the oxide semiconductor 470 forms the channel formation region in a top view. In this case, for example, the channel width of the transistor 320A is determined by the perimeter of the oxide semiconductor 470. That is, the channel width of the transistor 320A can be determined by the maximum width of the opening 490 (the maximum diameter when the opening 490 is circular in a top view). In FIGS. 22A and 22B , the maximum width D of the opening 490 is indicated by a double-headed, dashed arrow. In FIG. 22B , the channel width W of the transistor 320A is indicated by a double-headed, dashed arrow. By increasing the maximum width D of the opening 490, the channel width per unit area can be increased, and the on-current can be increased.

[0263] When the opening 490 is formed by photolithography, the maximum width D of the opening 490 is limited by the exposure limit of photolithography. Furthermore, the maximum width D of the opening 490 is limited by the film thicknesses of the oxide semiconductor 470, the insulator 430, and the conductor 420 provided in the opening 490. The maximum width D of the opening 490 is, for example, 5 nm or more, 10 nm or more, or 20 nm or more, and preferably 100 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less. When the opening 490 has a circular shape in top view, the maximum width D of the opening 490 corresponds to the diameter of the opening 490, and the channel width W can be calculated as "D × π."

[0264] In the memory device of one embodiment of the present invention, the channel length L of the transistor 320A is preferably at least shorter than the channel width W of the transistor 320A. The channel length L of the transistor 320A of one embodiment of the present invention is 0.1 to 0.99 times, preferably 0.5 to 0.8 times, the channel width W of the transistor 320A. With such a structure, a transistor with favorable electrical characteristics and high reliability can be realized.

[0265] Furthermore, by forming the opening 490 to have a substantially circular shape in top view, the oxide semiconductor 470, the insulator 430, and the conductor 420 are arranged concentrically. This makes the distance between the conductor 420 and the oxide semiconductor 470 substantially uniform, allowing a gate electric field to be applied to the oxide semiconductor 470 substantially uniformly.

[0266] The channel formation region of a transistor using an oxide semiconductor for a semiconductor layer preferably has fewer oxygen vacancies or a lower concentration of impurities such as hydrogen, nitrogen, or metal elements than the source and drain regions. For example, the aluminum concentration in the channel formation region of the oxide semiconductor is preferably 1×10 ２２ atoms / cm ３ Preferably, 1×10 ２１ atoms / cm ３ More preferably, 1×10 or less ２０ atoms / cm ３ Less than 5 x 10 is more preferable. １９ atoms / cm ３ More preferably, 1×10 or less １９ atoms / cm ３ Less than 5 x 10 is more preferable. １８ atoms / cm ３ More preferably, 1×10 or less １８ atoms / cm ３ The following is even more preferred:

[0267] In addition, hydrogen atoms near the oxygen vacancies are converted into defects where hydrogen atoms have entered the oxygen vacancies (hereinafter referred to as V Ｏ H) and generate electrons that become carriers. Therefore, in the channel formation region, V Ｏ It is preferable that H is also reduced. In this way, the channel formation region of the transistor is a high-resistance region with a low carrier concentration. Therefore, the channel formation region of the transistor can be said to be i-type (intrinsic) or substantially i-type.

[0268] In addition, the source and drain regions of a transistor using an oxide semiconductor for a semiconductor layer have more oxygen vacancies than the channel formation region. ＯThe source and drain regions of a transistor are n-type regions with a high carrier concentration and low resistance compared to the channel formation region, due to a high concentration of H or a high concentration of impurities such as hydrogen, nitrogen, and metal elements.

[0269] 22A and other drawings, the opening 490 is provided so that the side surface of the opening 490 is perpendicular to the upper surface of the wiring 450, but the present invention is not limited to this. For example, the side surface of the opening 490 may be tapered.

[0270] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes and examples described in this specification.

[0271] Embodiment 3 In this embodiment, an indium oxide film that can be used for a semiconductor layer of a transistor included in a display panel of one embodiment of the present invention will be described.

[0272] In this specification and the like, indium oxide having at least a crystalline portion or a crystalline region in a film is referred to as crystalline indium oxide (crystal IO) or crystalline indium oxide (crystalline IO). Examples of crystalline IO or crystalline IO include single-crystalline indium oxide, polycrystalline indium oxide, and microcrystalline indium oxide.

[0273] Indium oxide is a semiconductor material having physical properties that are completely different from those of oxide semiconductors such as In—Ga—Zn oxide (hereinafter also referred to as IGZO) and zinc oxide.

[0274] The carrier concentration dependence of the Hall mobility of indium oxide, silicon, and IGZO will be explained. FIG. 23A shows the carrier concentration dependence of the Hall mobility of silicon (Si) and indium oxide (InO Ｘ ) and FIG. 23B is a schematic diagram showing the carrier concentration dependence of the hole mobility for IGZO.

[0275] First, IGZO tends to exhibit higher hole mobility as the carrier concentration increases, as shown by the arrows in Figure 23B. On the other hand, indium oxide tends to exhibit higher hole mobility as the carrier concentration decreases, as shown by the arrows in Figure 23A (see Non-Patent Document 1). This trend is similar to that of silicon; the lower the dopant (impurity) concentration in the material, the less impurity scattering there is and the higher the hole mobility. In other words, the higher the purity and intrinsic indium oxide, the higher the hole mobility. From these results, it can be said that indium oxide, unlike IGZO, is a material with physical properties similar to those of silicon. Note that the characteristics of indium oxide shown in Figure 23A are assumed to be single crystal. Therefore, when indium oxide is non-single crystal (e.g., polycrystalline), the characteristics may differ from those shown in Figure 23A.

[0276] 23A, the range R1 of low carrier concentration has extremely high hole mobility, and therefore can be said to be a range of carrier concentration suitable for, for example, a channel formation region of a transistor. For example, in the case of indium oxide, the range R1 is a range where the carrier concentration value is 1×10 １５ cm −３ The range includes, for example, 1×10 １４ cm −３ That's it, 1 x 10 １８ cm −３ By sufficiently reducing the carrier concentration, the Hall mobility can be reduced to 270 cm ２ It is expected that the resistance can be increased to about / (V·s).

[0277] In addition, in indium oxide, the region where the carrier concentration is in the range R1 may contain an element that lowers the carrier concentration. Examples of elements that lower the carrier concentration include magnesium, calcium, zinc, cadmium, and copper. By substituting these elements for indium, the carrier concentration can be lowered. Examples of elements that lower the carrier concentration include nitrogen, phosphorus, arsenic, and antimony. For example, by substituting nitrogen, phosphorus, arsenic, or antimony for oxygen, the carrier concentration can be lowered.

[0278] On the other hand, the range R2 with a high carrier concentration has a low electrical resistance, and can be said to be a range of carrier concentrations suitable for, for example, the source and drain regions of a transistor, a resistor, or a transparent conductive film. ２０ cm −３ The range includes, for example, 1×10 １９ cm −３ That's it, 1 x 10 ２２ cm −３ By increasing the carrier concentration sufficiently, the resistivity can be reduced to 1×10 −４ It is expected that the resistance can be reduced to Ω·cm or less.

[0279] In the indium oxide, the region having a carrier concentration in the range R2 may contain an element that increases the carrier concentration. For example, it is preferable that the indium oxide contains an element that is common to the source electrode and the drain electrode of the transistor. Examples of elements that increase the carrier concentration include titanium, zirconium, hafnium, tantalum, tungsten, molybdenum, tin, silicon, and boron. In particular, it is more preferable to use an element whose oxide has conductive or semiconductive properties.

[0280] In this way, indium oxide uses a region with a low carrier concentration as the channel formation region of a transistor, and a region with a high carrier concentration as the source and drain regions of the transistor. In other words, indium oxide can be said to be an oxide capable of valence electron control. Note that IGZO may experience strain in the source and drain regions due to stress from electrodes in contact with the IGZO, resulting in the formation of n-type regions. On the other hand, unlike IGZO, indium oxide is capable of valence electron control, and therefore does not require strain to be formed in the film as with IGZO. Less strain in the film is expected to improve reliability. For example, by separately creating a region with a carrier concentration in the range R1 shown in FIG. 23A and a region with a carrier concentration in the range R2 in the indium oxide film, a so-called n-i-n junction (a junction between an n-type region, an i-type region, and an n-type region) can be created. Note that valence electron control in transistors using silicon is generally known. On the other hand, valence electron control in transistors using indium oxide is a novel technical concept that would not normally be conceived.

[0281] By using the above technical concept, the transistor having indium oxide in this specification and the like has two or more, preferably three or more, more preferably four or more, and most preferably five of the following characteristics (1) to (5): (1) high on-current (in other words, high mobility); (2) low off-current; (3) normally-off operation; (4) high reliability; and (5) high cutoff frequency (fT). For example, the transistor having indium oxide in this specification and the like has high mobility, low off-current, and is normally-off operation. The transistor has high mobility and is different from a normally-on transistor.

[0282] Next, an indium oxide film applied to a transistor will be described. The indium oxide film preferably has crystallinity (i.e., has crystal grains). Examples of films having crystal grains include single-crystal films, polycrystalline films, and amorphous films containing crystal grains (also called microcrystalline films). In particular, the indium oxide film is preferably a polycrystalline film, and more preferably a single-crystal film. A single-crystal film does not have grain boundaries. Impurities (typically, insulating impurities, insulating oxides, etc.) that hinder carrier flow tend to segregate at grain boundaries. The use of a single-crystal film can suppress carrier scattering at grain boundaries, thereby realizing a transistor exhibiting high field-effect mobility. Furthermore, the use of a single-crystal film has the excellent effect of suppressing variations in transistor characteristics due to the grain boundaries.

[0283] Furthermore, polycrystalline films are preferable because they can reduce carrier scattering and exhibit high field-effect mobility compared to microcrystalline or amorphous films. When using a polycrystalline film, it is preferable to use a film with as large a crystal grain size as possible and with few crystal grain boundaries. Note that in a transistor using an indium oxide polycrystalline film, if there is no crystal grain boundary in the channel formation region or no crystal grain boundary is observed, the channel formation region is located within a single crystal region included in the polycrystalline film, and therefore the transistor can be considered to be using single-crystal indium oxide.

[0284] The crystallinity of indium oxide can be analyzed by, for example, X-ray diffraction (XRD), transmission electron microscope (TEM), or electron diffraction (ED). Alternatively, a combination of these methods may be used for analysis.

[0285] In this specification and the like, a semiconductor layer in which no crystal grain boundary is observed in the channel formation region, a semiconductor layer in which the channel formation region is included in one crystal grain, or a semiconductor layer in which the crystal axis direction is the same in at least two regions in the channel formation region can be called a single crystal film. Also, a semiconductor layer in which, in the channel formation region, within one crystal grain, the direction of another crystal axis continuously changes around a certain crystal axis or a certain crystal orientation as the axis of rotation can be called a single crystal film.

[0286] The channel formation region refers to a region of the semiconductor layer that overlaps (or faces) the gate electrode via the gate insulating layer, and is located between the region in contact with the source electrode and the region in contact with the drain electrode. The current path in the channel formation region is the shortest distance between the source electrode and the drain electrode. Therefore, the crystal grains, crystal grain boundaries, crystal axes, crystal orientation, etc. in the channel formation region can be confirmed by observing a cross section including the semiconductor layer, the source electrode, and the drain electrode.

[0287] The indium oxide film in the channel formation region preferably has a lower impurity concentration. Impurities in the indium oxide film in the channel formation region can be a scattering source of carriers, which can lead to a decrease in field-effect mobility. These impurities can also hinder the crystal growth of the indium oxide film. Examples of impurities in the indium oxide film include boron and silicon. The indium oxide film preferably contains these impurities at concentrations of 0.1% or less, and more preferably 0.01% (100 ppm) or less. Carbon, hydrogen, and other elements may be contained in the film-forming gas or precursor during film formation, and may remain in the indium oxide film in greater amounts than the above-mentioned impurities.

[0288] The indium oxide film in the channel formation region may contain an element that can become the same trivalent cation as indium, as long as the crystal maintains a cubic crystal structure (bixbyite type). Examples of such an element include Group 13 elements of the periodic table, such as gallium and aluminum, and Group 3 elements of the periodic table. These elements exist mainly as trivalent cations in oxides, and therefore the carrier concentration of indium oxide can be maintained low.

[0289] By using such an indium oxide film in a transistor, the field effect mobility of the transistor can be increased to 50 cm ２ / (V·s) or more, preferably 100 cm ２ / (V·s) or more, more preferably 150 cm ２ / (V·s) or more, more preferably 200 cm ２ / (V·s) or more, more preferably 250 cm ２ / (V·s) or more.

[0290] One of the features of an indium oxide film is that it has higher oxygen permeability (diffusibility) than an IGZO film. As shown in FIG. 23C, an indium oxide film (InO Ｘ Oxygen (O) diffusing into the indium oxide film passes through the indium oxide film and becomes oxygen molecules (O ２ ) and is released as water molecules (H ２ O) may be released in the film. Ｏ In the case where an indium oxide film is present, oxygen atoms diffuse to compensate for the oxygen vacancies. Since oxygen diffuses easily in the indium oxide film, it can be said that oxygen vacancies are more easily compensated for in the indium oxide film than in the IGZO film.

[0291] As described above, an indium oxide film can more easily reduce oxygen vacancies in the film than an IGZO film. Therefore, by using such an indium oxide film in a transistor, a transistor exhibiting extremely high reliability can be realized.

[0292] Furthermore, as shown in FIG. 23C, the indium oxide film diffuses hydrogen. Hydrogen that diffuses into the indium oxide film from the outside passes through the indium oxide film and becomes hydrogen molecules (H ２ ) or reacts with oxygen contained in the membrane and is released as water molecules.

[0293] A transistor using an indium oxide film is an accumulation-type transistor that uses electrons as majority carriers. Assuming that the carrier relaxation time is constant, the smaller the effective mass of the electrons (carriers), the higher the electron mobility. In other words, by using indium oxide, which has a small effective mass of electrons, for a transistor, the on-state current or field-effect mobility of the transistor can be increased.

[0294] Table 1 shows the results of single crystal indium oxide (here, In ２ O ３ ) and single-crystal silicon (Si). As shown in Table 1, indium oxide is characterized by a small effective mass of electrons and a large effective mass of holes. Indium oxide also has the characteristic that the effective mass of electrons is almost independent of the crystal orientation. Therefore, by using crystalline indium oxide in a transistor, a transistor with high field-effect mobility and high frequency characteristics (also called f characteristics) can be realized. Furthermore, since the effective mass of holes is large, a transistor with extremely small off-current can be realized. For example, by applying an indium oxide film to a vertical transistor, the off-current per 1 μm of channel width can be reduced to 1 fA (1×10) in an environment of 125° C. −１５ A) or less, or 1aA (1 x 10 −１８ A) or less, and under room temperature (25°C) conditions, −１８ A) or less, or 1zA (1 x 10 −２１ Furthermore, as shown in Table 1, indium oxide has a smaller effective mass of electrons and a larger effective mass of holes than silicon, and therefore may be able to realize a transistor with higher field-effect mobility and lower off-state current than a Si transistor.

[0295]

[0296] It is preferable to provide a seed layer so as to be in contact with at least a portion of the crystalline indium oxide film. The seed layer is preferably made of a material containing crystals with a small difference in lattice constant (also called lattice mismatch) with indium oxide. This can improve the crystallinity of the indium oxide film. Note that a substrate (e.g., a single-crystal substrate) may be used as one of the layers in contact with at least a portion of the crystalline indium oxide film.

[0297] One method for evaluating the degree of lattice mismatch is to use the value of the lattice mismatch shown below. The lattice mismatch Δa [%] of the crystals of the formed film (here, the indium oxide film) with respect to the crystals of the seed layer is expressed as Δa = ((L １ -L ２ ) / L ２ ) × 100, where L １ is the length or lattice constant of the unit lattice vector of the crystal of the formed film, and L ２ is the length of the unit cell vector or the lattice constant of the crystal of the seed layer.

[0298] The smaller the absolute value of the lattice mismatch Δa between the seed layer and the indium oxide film, the more preferable, and it is most preferably 0. For example, Δa can be set to −5% or more and 5% or less, preferably −4% or more and 4% or less, more preferably −3% or more and 3% or less, and even more preferably −2% or more and 2% or less.

[0299] Here, the indium oxide crystal has a cubic crystal structure (bixbyite type). For example, the crystal of yttria-stabilized zirconia (YSZ) can have a cubic crystal structure (fluorite type). The lattice mismatch of the indium oxide crystal with the cubic YSZ crystal is in the range of −2% to 2%, and a single crystal film of indium oxide can be epitaxially grown on the YSZ substrate.

[0300] It should be noted that the crystal structure of the seed layer and the crystal structure of the indium oxide film may not necessarily have the same crystal system or crystal orientation. For example, a film having crystals of a hexagonal or trigonal structure may be used under an indium oxide film having crystals of a cubic structure. For example, by setting the crystal orientation of the surface of the seed layer to

[001] and the crystal orientation of the underside of the indium oxide film to

[111] , the requirements related to the crystal orientation necessary for epitaxial growth can be satisfied. Examples of hexagonal or trigonal crystals include wurtzite structure, YbFe ２ O ４ Type structure, Yb ２ Fe ３ O ７ YbFeFe alloys have the following structures: ２ O ４ Type structure or Yb ２ Fe ３ O ７ An example of a crystal having a ZnO-type structure is IGZO.

[0301] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0302]

Claims

a first optical rotator, a second optical rotator, and a third optical rotator are arranged in this order; the first to third optical rotators have different wavelength dependencies of the rotation angles of the polarization planes, When linearly polarized light including a first wavelength, a second wavelength, and a third wavelength is incident on the first polarization rotator, An optical device having a function of making the planes of polarization of the linearly polarized light of the first wavelength, the second wavelength, and the third wavelength emitted from the third rotator the same. 　 In claim 1, The optical device, wherein the rotation angles imparted by the first to third rotators to the linearly polarized light of the first wavelength, the second wavelength, and the third wavelength that are transmitted therethrough are 45° + 180×M (M is an integer). 　 In claim 1, The optical device wherein the first wavelength corresponds to red light, the second wavelength corresponds to green light, and the third wavelength corresponds to blue light. 　 In claim 1, The optical apparatus, wherein the first to third optical rotators are Faraday rotators. 　 In claim 4, the Faraday rotator includes a magneto-optical crystal and a magnetic field source; An optical instrument having a coil as the magnetic field source. 　 In claim 5, In the first to third optical rotators, Optical devices each having a coil with a different inductance. 　 In claim 5, In the first to third optical rotators, Optical devices each having a different thickness of the magneto-optical crystal. 　 In claim 1, a first reflective polarizer and a second reflective polarizer; The optical device includes the first to third rotators positioned between the first reflective polarizer and the second reflective polarizer. 　 In claim 8, a first convex lens; the first convex lens is provided between the first reflective polarizer and the first optical rotator, The optical device, wherein the first convex lens is provided in contact with the first reflective polarizing plate. 　 In claim 9, a second convex lens; the second convex lens is provided between the second reflective polarizer and the third optical rotator, The optical device is configured such that the second convex lens is in contact with the second reflective polarizing plate. 　 An optical device comprising: an optical device according to any one of claims 1 to 10; and an organic EL panel; The organic EL panel is disposed so that a display portion thereof perpendicularly intersects with an optical axis 46 of the optical device 30, and the organic EL panel has a lens provided on an organic EL element. 　 In claim 11, The organic EL element is connected to a transistor having a metal oxide in a channel forming region. 　 In claim 12, The electronic device wherein the metal oxide is indium oxide.

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