Image forming element and method for manufacturing the same

Abstract

The image forming element comprises a plurality of pixels arranged in a two-dimensional array, and projects and displays the emitted light of the pixels, wherein the pixels include at least one light-emitting element that emits the emitted light, and the image forming element comprises: a plurality of light-emitting elements, a mounting substrate on which the plurality of light-emitting elements are mounted on a mounting surface, a first light-shielding layer, and a second light-shielding layer, wherein the mounting substrate includes a driving circuit for driving the light-emitting elements, and has individual electrodes on the mounting surface that are electrically connected to power supply electrodes of the light-emitting elements, at least a portion of the plurality of light-emitting elements include a light source and a wavelength conversion layer, the wavelength conversion layer converts the wavelength of light emitted by the light source and emits the light to the outside, the first light-shielding layer is arranged around the light source, and is formed of a material having light reflectivity or light absorption, and the second light-shielding layer is arranged between adjacent wavelength conversion layers, and is formed of a material having light reflectivity or light absorption.

Description

[0001] This application is a divisional application of the invention patent with application number 201680068315.7, application date November 9, 2016, and invention name “Image Forming Element”. Technical Field

[0002] The present invention relates to an image forming element including a plurality of pixels and projecting and displaying light emitted from the pixels. Background Art

[0003] In projectors, head-up displays (HUDs), etc., the light emitted from the light source is separated into three primary colors: red, green, and blue. And, by using an optical switch to change the light intensity for each pixel, it is synthesized and projected to form a color image. For optical switches, liquid crystal elements and digital micromirror devices (DMDs) are used. For liquid crystal elements, for example, a transmissive liquid crystal panel and a reflective liquid crystal element (for example, LCOS: Liquid Crystal On Silicon) in which a liquid crystal layer is provided on a liquid crystal drive circuit element composed of a silicon LSI are used. DMD forms a tiny reflector configured for each pixel on its drive circuit, and switches the light by adjusting the angle of the reflector.

[0004] In the method of forming a color image using an optical switch such as the above, for darker pixels, there are differences such as blocking or absorbing light from the light source by liquid crystal, or emitting light outside the optical path through the above-mentioned reflector, but both cases lead to light waste. Regardless of whether it is a brighter case or a darker case, the energy consumed by the light source does not change, resulting in a large energy loss. In addition, when a liquid crystal element is used for an optical switch, it is difficult to completely block the light, so there is a problem of reduced image contrast. When a DMD is used for an optical switch, sometimes the contrast is reduced due to stray light (Stray Light) generated by light outside the optical path. As a result, in a display using a liquid crystal element and an optical switch element such as a DMD, the energy of the light source is wasted.

[0005] In order to reduce power consumption, the idea of ​​using self-luminous elements to form pixels of the display has been proposed. For example, in Patent Document 1, a structure is disclosed in which an LED chip whose light-emitting layer is composed of AlInGaP is integrated on a silicon substrate forming a driving circuit. In Patent Document 2, a structure is also disclosed in which an LED chip whose light-emitting layer is composed of InGaN layer is integrated on a silicon substrate forming a driving circuit. In addition, in Non-Patent Document 1, a structure in which blue LED chips whose light-emitting layers are composed of InGaN layers are integrated in 30 rows and 30 columns on a silicon substrate forming a driving circuit, and a structure in which blue LED chips whose light-emitting layers are composed of InGaN layers are integrated in 60 rows and 60 columns are disclosed. In addition, an example in which three-color phosphors are arranged on the LED of each pixel is also disclosed. In addition, the pixel pitch is 140 [μm] or 70 [μm]. In Non-Patent Document 2, a 160×120 pixel monochrome display element is trial-produced for a structure in which a green LED chip whose light-emitting layer is composed of InGaN is integrated on a silicon substrate forming a driving circuit. The pixel pitch is 15 [μm].

[0006] In the technology disclosed above, current flows from the driving circuit on the silicon substrate to the LED chip constituting each pixel corresponding to the brightness information of each pixel. Therefore, pixels in the dark state do not consume current, and pixels in the bright state only consume current corresponding to the brightness. Therefore, the current consumption can be greatly reduced compared with the current mainstream optical switching method. In addition, the epitaxial layer (usually an N-type epitaxial layer) of the LED chip is used as the electrode on one side of the LED (usually the negative side). Alternatively, there is also a case where the epitaxial growth substrate of the LED chip is used as its retaining layer and remains intact.

[0007] In addition, as an example of the prior art related to the present invention, Patent Document 3 discloses a structure in which an AlGaAs-based LED is bonded to a silicon substrate on which a driving circuit is formed. In addition, Patent Document 4 discloses an example in which a pixel is formed by an LED chip in which a cathode and an anode are provided on one side of the LED chip. That is, the so-called flip chip connection is applied to an LED display.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent document 1: Japanese Patent Application Publication No. 10-12932.

[0011] Patent document 2: Japanese Patent Application Publication No. 2002-141492.

[0012] Patent document 3: Japanese Patent Gazette No. 3813123.

[0013] Patent document 4: U.S. Patent No. 9111464.

[0014] Non-patent literature

[0015] Non-patent document 1: Liu, ZJet al., "Monolithic LED Microdisplay on ActiveMatrix Substrate Using Flip-Chip Technology", IEEE journal of selected topics in quantum electronics, Vol. 15, No. 4, p. 1298-1302, (2009).

[0016] Non-patent document 2: J Day et al., “III-Nitride full-scale high-resolution microdisplays”, Applied Physics Letters 99(3), 031116, (2011). Summary of the invention

[0017] Technical Problems to be Solved by the Invention

[0018] However, there are the following problems in producing LED display chips using the structures and methods described in Patent Documents 1 to 4 and Non-Patent Documents 1 to 2.

[0019] First, as in Patent Documents 1 to 2 and Non-Patent Documents 1 to 2, consider the case where the substrate used to form the LED chip and the epitaxial layer constituting the LED are continuous between pixels, or even if they are disconnected, they are very close. In these cases, light leaks from the lit pixel to the adjacent pixel, and the adjacent pixel also emits light slightly. This is a phenomenon caused by part of the light being confined inside the epitaxial layer and the substrate, so the light that leaks to the adjacent pixel through them is emitted from the pixel to the outside. This phenomenon cannot be avoided in the above-mentioned technology. In addition, this phenomenon increases the brightness of the dark pixel adjacent to the bright pixel, thereby causing the problem of reducing the contrast of the image.

[0020] In addition, in patent documents 1 to 3 and non-patent documents 1 to 2, upper and lower electrode type LED chips are used for pixels. (In addition, the upper and lower electrode type is a structure in which a cathode and an anode are arranged above and below the light-emitting layer. Usually, the cathode electrode is arranged in contact with the lower surface of the N-type epitaxial layer below the light-emitting layer, and the anode electrode is arranged in contact with the upper surface of the P-type epitaxial layer above the light-emitting layer.) If an upper and lower electrode type LED chip is used, after the electrode on the silicon substrate forming the driving circuit is connected to the electrode on one side of the LED chip, if the process of connecting the electrode on the other side of the LED chip to the other electrode on the silicon substrate is not performed, the characteristics of the LED chip cannot be tested. In the case of testing each pixel after connecting the electrodes of the LED chip, even if a bad pixel such as not lighting or poor grayscale is found through testing, it is not easy to repair the bad pixel. Assuming that in the case of repair, it is necessary to remove the connection between the LED chip and the silicon substrate and the bad LED chip, replace it with a normal LED chip, connect the electrode on one side of the LED chip to the electrode on the silicon substrate, and connect the electrode on the other side of the LED chip to the electrode on the silicon substrate again. Such a repair process is not only costly, but also sometimes causes damage to the surrounding pixels, making it impractical. Therefore, it is very difficult to repair such pixel defects in displays, and if it is performed, the yield rate will be significantly reduced.

[0021] In view of the above circumstances, an object of the present invention is to provide an image forming element having excellent color rendering and high contrast, and to establish a technology capable of manufacturing an image forming element with a low defect rate and a high yield.

[0022] Means of solving the problem

[0023] In order to achieve the above-mentioned purpose, an image forming element based on one embodiment of the present invention comprises a plurality of pixels arranged in a two-dimensional array, and projects and displays the emitted light of the pixels, the pixels include at least one light-emitting element that emits the emitted light, the image forming element comprises: a plurality of the light-emitting elements, a mounting substrate on which the plurality of the light-emitting elements are mounted on a mounting surface, a first light-shielding layer and a second light-shielding layer, the mounting substrate includes a driving circuit for driving the light-emitting elements, and has individual electrodes on the mounting surface that are electrically connected to power supply electrodes of the light-emitting elements, at least a portion of the plurality of light-emitting elements include a light source and a wavelength conversion layer, the wavelength conversion layer converts the wavelength of light emitted by the light source and emits it to the outside, the first light-shielding layer is arranged around the light source, and is formed of a material having light reflectivity or light absorption, and the second light-shielding layer is arranged between adjacent wavelength conversion layers, and is formed of a material having light reflectivity or light absorption.

[0024] In the above-mentioned image forming element, the height of the first light shielding layer may be the same as the height of the light source from the surface facing the mounting substrate to the surface opposite to the surface facing the mounting substrate.

[0025] In the above-mentioned image forming element, the plurality of light sources may include a compound semiconductor layer, and the plurality of adjacent light-emitting elements may share at least a portion of the compound semiconductor layer.

[0026] In the above-mentioned image forming element, it can also be constructed as follows: the plurality of the above-mentioned light sources include a compound semiconductor layer, the adjacent plurality of the above-mentioned light-emitting elements share at least a portion of the above-mentioned compound semiconductor layer, and the above-mentioned second light-shielding layer is arranged on the above-mentioned compound semiconductor layer shared by the adjacent plurality of the above-mentioned light-emitting elements.

[0027] In the above-mentioned image forming element, the compound semiconductor layer may be configured to be individualized for each of the plurality of light-emitting elements.

[0028] In the above-mentioned image forming element, the first light-shielding layer and the second light-shielding layer may be formed of the same material.

[0029] In the above-mentioned image forming element, the first light shielding layer may be formed of a resin in which a white pigment is dispersed.

[0030] In the above-mentioned image forming element, the first light shielding layer may be formed of a resin in which a black pigment is dispersed.

[0031] In the above-mentioned image forming element, the wavelength conversion layer may include a quantum dot material.

[0032] In the above-mentioned image forming element, the wavelength conversion layer may include a color filter layer.

[0033] In the above-mentioned image forming element, the second light shielding layer may have a high reflectivity and a low light absorption.

[0034] In addition, in order to achieve the above-mentioned purpose, in a manufacturing method of an image forming element based on another embodiment of the present invention, the above-mentioned image forming element has a plurality of pixels and projects and displays the emitted light of the pixels, and the above-mentioned manufacturing method includes the following steps: a step of forming a driving circuit on a mounting substrate formed by a semiconductor substrate, and the above-mentioned driving circuit is used to drive the light source corresponding to the above-mentioned pixel; a step of forming a light-emitting array, and the above-mentioned light-emitting array is composed of a plurality of the above-mentioned light sources; a step of pasting the above-mentioned light-emitting array on the above-mentioned mounting substrate; a step of setting a first light-shielding layer between the plurality of the above-mentioned light sources; a step of setting a second light-shielding layer on the above-mentioned first light-shielding layer; and a step of setting a wavelength conversion layer on the above-mentioned light source.

[0035] In the above-mentioned method for manufacturing the image forming element, it can also be constructed as follows: sequentially implementing: the process of pasting the above-mentioned light-emitting array onto the above-mentioned mounting substrate, the process of setting the above-mentioned first light-shielding layer between the above-mentioned multiple light sources, the process of setting the above-mentioned second light-shielding layer on the above-mentioned first light-shielding layer, and the process of setting a wavelength conversion layer on the above-mentioned light source.

[0036] In the above-mentioned method for manufacturing the image forming element, it can also be constructed as: after the process of setting the above-mentioned second light-shielding layer, it can also include the following processes: a process of forming a resist pattern, wherein the above-mentioned resist pattern covers a portion of the upper surface of the above-mentioned second light-shielding layer; and a process of configuring the above-mentioned wavelength conversion layer in the portion of the upper surface of the above-mentioned second light-shielding layer that is not covered by the above-mentioned resist pattern.

[0037] In the above-mentioned method for manufacturing the image forming element, it can also be configured as follows: the process of setting a wavelength conversion layer on the above-mentioned light source also includes the following processes: the process of forming a negative resist layer on the above-mentioned second light-shielding layer; the process of making a part of the above-mentioned negative resist layer insoluble by exposure; and the process of dissolving the unexposed negative resist layer in the process of making a part of the above-mentioned negative resist layer insoluble by exposure.

[0038] The method for manufacturing the image forming element may further include providing a resist pattern on a surface of the light source after the step of attaching the light emitting array to the mounting substrate.

[0039] In the above-mentioned method for manufacturing the image forming element, it can also be constructed as follows: after the process of pasting the above-mentioned light-emitting array onto the above-mentioned mounting substrate, it also includes the process of setting a resist pattern on the surface of the above-mentioned light source, and the process of setting the above-mentioned first shading layer and the process of setting the above-mentioned second shading layer are carried out simultaneously.

[0040] In the above-mentioned method for manufacturing an image forming element, the wavelength conversion layer may include a quantum dot material.

[0041] Effects of the Invention

[0042] According to the present invention, it is possible to provide an image forming element having excellent color rendering and high contrast, and to establish a technology capable of manufacturing an image forming element with a low defect rate and a high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram for explaining the structure of an LED display chip.

[0044] Figure 2 It is a perspective plan view of a pixel according to the first embodiment.

[0045] Figure 3 It is a cross-sectional view showing a configuration example of a pixel according to the first embodiment.

[0046] Figure 4 : is an equivalent circuit diagram showing a configuration example of a pixel driving circuit according to the first embodiment.

[0047] Figure 5 It is a perspective plan view showing an example of a pattern layout of a pixel driving circuit.

[0048] Fig. 6A Represents the cross-sectional structure along the single-point chain line BB.

[0049] Figure 6B Represents the cross-sectional structure along the single-point chain line CC.

[0050] Fig. 7A This is a diagram for explaining the process of epitaxially growing a compound semiconductor layer on a sapphire substrate and forming a transparent conductive film thereon.

[0051] Figure 7B This is a diagram for explaining a step of forming a mesa portion in an epitaxial layer.

[0052] Figure 7C It is a diagram for explaining the process of forming a protective film.

[0053] Fig.7D It is a diagram for explaining the process of forming each contact hole.

[0054] Fig. 7E It is a diagram for explaining the process of forming the P-side electrode and the N-side electrode.

[0055] Figure 7F It is a diagram for explaining the process of forming the separation groove.

[0056] Figure 7G This is a diagram for explaining the process of attaching the separated blue LED chips to the holding substrate.

[0057] Figure 7H This is a diagram for explaining the process of separating each blue LED chip from the sapphire substrate.

[0058] Fig.7I This is a diagram for explaining the step of attaching each blue LED chip to the transfer substrate.

[0059] Figure 8 This is a plan view showing an example of a blue LED chip provided in a pixel array.

[0060] Fig.9A This is a diagram for explaining the process of attaching a blue LED chip to an image driving circuit.

[0061] Fig. 9B This is a diagram for explaining the process of performing a light emission test on a pixel.

[0062] Fig. 9C This is a diagram for explaining a process of removing a blue LED chip detected to have poor light emission from an image driving circuit.

[0063] Fig.9D This is a diagram for explaining the process of mounting a replacement normal blue LED chip.

[0064] Fig.9E This is a diagram for explaining the process of performing a re-emission test of a pixel.

[0065] Fig.9F This is a diagram for explaining the process of firing the LED display chip while applying pressure.

[0066] Figure 9G This is a diagram for explaining the process of forming a resist pattern on a blue LED chip.

[0067] Figure 9H This is a diagram for explaining a process of forming a light-shielding reflective layer on a pixel array.

[0068] Fig.9I This is a diagram for explaining the process of removing the resist pattern.

[0069] Fig.10 Graph showing the current dependence of the luminous efficiency of blue LED chips of various shapes manufactured by different manufacturers.

[0070] Fig.11A It is a plan view showing a modified example of a blue LED chip provided in a pixel array.

[0071] Fig. 11BIt is a plan view showing another modified example of a blue LED chip provided in a pixel array.

[0072] Fig. 11C It is a plan view showing another modified example of a blue LED chip provided in a pixel array.

[0073] Fig.12 It is a cross-sectional view showing a configuration example of a pixel according to the second embodiment.

[0074] Fig.13 It is a perspective plan view of a pixel according to the third embodiment.

[0075] Fig.14A It is a perspective plan view showing a configuration example of a pixel having an independent type light-emitting element.

[0076] Fig. 14B It is a perspective plan view showing a configuration example of a pixel having an integrated light-emitting element.

[0077] Fig. 14C It is a perspective plan view showing a configuration example in which a plurality of pixels are integrated.

[0078] Fig.15 It is a cross-sectional view showing a configuration example of a pixel in an independent type LED display chip.

[0079] Fig.16 This is an equivalent circuit diagram showing an example of a pixel driving circuit for an independent light-emitting element.

[0080] Fig.17A It is a diagram showing the process of coating a wavelength conversion layer and performing pattern exposure.

[0081] Fig. 17B It is a diagram showing the process of developing and baking the wavelength conversion layer.

[0082] Fig. 17C It is a diagram showing the process of coating a wavelength conversion layer and performing pattern exposure.

[0083] Fig.17D It is a diagram showing the process of developing and baking the wavelength conversion layer.

[0084] Fig.18A It is a diagram showing the process of coating a wavelength conversion layer for red and performing pattern exposure.

[0085] Fig.18B This is a diagram showing the steps of developing and baking the red wavelength conversion layer.

[0086] Fig. 18C This is a diagram showing the process of developing and baking the wavelength conversion layer for green.

[0087] Fig.18D This is a diagram showing the process of developing and baking the wavelength conversion layer for blue.

[0088] Fig.19A It is a figure which shows the process of forming a positive resist pattern and applying a wavelength conversion layer.

[0089] Fig.19B It is a figure which shows the process of removing the flat part of a wavelength conversion layer and a positive resist pattern.

[0090] Fig. 20 It is a perspective plan view of a pixel according to the fourth embodiment.

[0091] Fig.21 : is an equivalent circuit diagram showing an example of a pixel driving circuit according to the fourth embodiment.

[0092] Fig. 22 1 is an equivalent circuit diagram showing another example of the pixel driving circuit according to the fourth embodiment.

[0093] Fig.23 : is an equivalent circuit diagram showing an example of a pixel driving circuit according to the fifth embodiment.

[0094] Fig.24 This is an equivalent circuit diagram showing an example of a pixel driving circuit in which the configuration of the fourth embodiment is combined with the fifth embodiment.

[0095] Fig.25 It is an equivalent circuit diagram showing another example of the pixel driving circuit according to the fifth embodiment. DETAILED DESCRIPTION

[0096] Hereinafter, an LED display chip 1 equipped with an LED (Light Emitting Diode) as a light source is cited as an example, and an embodiment of the present invention is described with reference to the accompanying drawings. In addition, the LED display chip 1 is an example of an image forming element having a plurality of pixels 3 and used to project the emitted light of the pixel 3 onto a projection surface (not shown) to form an image. In the following, for the light-emitting element 10, in the case of monochromatic light emission of the LED display chip 1, it refers to the entire light-emitting portion of each pixel 3, and in the case of color light emission, it refers to the light-emitting portion of each color constituting the pixel 3. In addition, the state in which a single LED or a plurality of LEDs integrated into one are separated from adjacent LEDs is called monolithicization. LED and LED chip refer to a light source composed of a compound semiconductor layer 31 and electrodes 40, 41, etc. described later, and their composition does not include a wavelength conversion layer 62 for converting the wavelength of the emitted light of the LED or LED chip. In addition, the light-emitting element 10 refers to an element having an LED or an LED chip and a wavelength conversion layer 62 in a composition in which the wavelength conversion layer 62 is provided on the LED or LED chip. The wavelength conversion layer 62 for converting the wavelength of light emitted from the LED is not provided in the light emitting element 10 in the configuration of the LED or the LED chip, but refers to the LED itself or the LED chip itself.

[0097] <First embodiment>

[0098] In the present embodiment, three types of LED display chips 1 are used to display color images. Each LED display chip 1 emits monochromatic light of red (R), green (G), and blue (B). A color image is formed by overlapping the luminous images projected from each LED display chip 1R, 1G, and 1B. The red light-emitting element 11 of the LED display chip 1R for red display is equipped with a red LED chip having, for example, an AlInGaP-based red LED. The green light-emitting element 12 of the LED display chip 1G for green display is equipped with a green LED chip having, for example, an InGaN-based green LED. The blue light-emitting element 13 of the LED display chip 1B for blue display is equipped with a blue LED chip 50 having, for example, an InGaN-based blue LED. In addition, the red LED, the green LED, and the blue LED are compound semiconductor light-emitting diodes that emit monochromatic light of red (R), green (G), and blue (B), respectively. Hereinafter, when the red light-emitting element 11, the green light-emitting element 12, and the blue light-emitting element 13 are collectively referred to as the light-emitting element 10 only. The LED display chip 1 can perform a brighter display and perform a projection display suitable for a large screen.

[0099] Hereinafter, the configuration of the LED display chip 1 will be described by taking the LED display chip 1B for blue display as an example. The configurations of the LED display chip 1R for red display and the LED display chip 1G for green display are the same, and thus their description will be omitted.

[0100] Figure 1 1B is a schematic diagram for explaining the structure of the LED display chip 1B. Figure 1 As shown in the right figure of FIG. 1 , the LED display chip 1B includes an LSI 7 and a light emitting array 8 provided in a pixel array 2 composed of a plurality of pixels 3 .

[0101] also, Figure 1 The right figure is a schematic diagram showing an example of the configuration of the LED display chip 1B. In addition, the figure in the upper center is a schematic diagram showing an example of the configuration of the LSI 7, and the upper left figure is a top view showing an example of a silicon wafer W1 formed as a single piece of the LSI 7. In addition, Figure 1 The lower center figure is a schematic diagram showing a configuration example of the light emitting array 8, and the lower left figure is a top view showing an example of a sapphire wafer W2 on which the light emitting array 8 is formed.

[0102] in addition, Figure 2 It is a perspective plan view of the pixel 3 according to the first embodiment. Figure 3 It is a cross-sectional view showing a configuration example of the pixel 3 according to the first embodiment. Figure 3 Indicates along Figure 2 The cross-sectional structure of pixel 3 along the single-point chain line AA.

[0103] The pixel array 2 is arranged two-dimensionally with N rows and M columns, and is composed of a total of N×M pixels 3. Hereinafter, pixel 3 (I, J) is used to represent a pixel in row I and column J. In addition, N and M are both positive integers, I is a positive integer greater than 1 and less than N, and J is a positive integer greater than 1 and less than M. For example, if it is a full HD standard display, N=1080 and M=1920, and the number of pixels 3 is about two million. Each pixel 3 includes multiple or single self-luminous blue LED chips 50.

[0104] The LSI 7 can be formed by a common CMOS process and is a light-emitting control unit that supplies power to the light-emitting array 8 and controls its light emission. Figure 1 As shown in the upper left figure of , various circuits for projecting and displaying images are formed monolithically on a silicon wafer W1, and then divided into individual unit units to manufacture LSI 7. Figure 1 As shown in the upper center portion of the figure, the LSI 7 includes the above-mentioned various circuits, namely, a plurality of pixel driving circuits 100, a row selection circuit 4, a column signal output circuit 5, and an image processing circuit 6.

[0105] The pixel driving circuit 100 is arranged in a two-dimensional arrangement of N rows and M columns corresponding to each pixel 3, and supplies a driving current 54 (described later) to the blue LED (here, the blue LED chip 50) arranged above itself to drive it to emit light. The row selection circuit 4 selects the I row in which the emitting pixels 3 (I, J) in the pixel array 2 are arranged based on the image data. The column signal output circuit 5 controls the light emission of each pixel 3 (I, J) in the selected I row based on the image data. The image processing circuit 6 controls the row selection circuit 4 and the column signal output circuit 5 based on the image data.

[0106] like Figure 3 As shown, the pixel driving circuit 100 is composed of various circuits formed monolithically on the silicon wafer W1 and wiring layers formed thereon, for example, formed by a CMOS process. At the top of the pixel driving circuit 100, an N-side common electrode 19 electrically connected to the blue LED chip 50 and a P-side individual electrode 20 are provided on the mounting surface of the blue LED chip 50. The N-side common electrode 19 is a common electrode electrically connected to the later-described N-side electrode 41 of each blue LED chip 50 of the pixel 3 arranged along the column direction and arranged in each column of the two-dimensionally arranged pixel 3. The P-side individual electrode 20 is provided for each pixel 3 and electrically connected to the later-described P-side electrode 40 of the blue LED chip 50. The pixel driving circuit 100 supplies a driving current 54 to each blue LED chip 50 of the pixel 3 (I, J) of the I row selected by the row selection circuit 4 according to the signal output by the column signal output circuit 5, so that it emits light. The more detailed structure of the pixel driving circuit 100 will be described later.

[0107] The light emitting array 8 is composed of a plurality of light emitting elements 10 (here, blue LED chips 50) arranged two-dimensionally in N rows and M columns corresponding to each pixel 3. Figure 3 As shown, the blue LED chip 50 includes a compound semiconductor layer 31, a transparent conductive film 35, a protective film 37, a P-side electrode 40, and an N-side electrode 41. The compound semiconductor layer 31 has an N-side epitaxial layer 32, a light-emitting layer 33, and a P-side epitaxial layer 34, and these layers 32 to 34 are stacked in sequence. The more detailed structure of the blue LED chip 50 will be described later.

[0108] Figure 3The blue LED chip 50 is a blue LED that is monolithic for each pixel 3. By this monolithicization, the leakage of light toward the adjacent blue LED chip 50 can be minimized, thereby improving the contrast of the image projected by the LED display chip 1. In addition, it is also possible to suppress or prevent problems such as positional offset between the blue LED chip 50 and the LSI 7 caused by the difference in thermal expansion coefficient between the compound semiconductor layer 31 of the blue LED chip 50 and the silicon wafer W1 formed as a monolithic piece of the LSI 7. In addition, the blue LED chip 50 has a cathode (N-side electrode 41) and an anode (P-side electrode 40). They are connected to the N-side common electrode 19 and the P-side individual electrode 20 of the pixel driving circuit 100 respectively by the same method. In addition, the P-side electrode 40 and the N-side electrode 41 are power supply electrodes arranged on the same main surface. Therefore, a light emission test is carried out at the stage of connecting the blue LED chip 50 to the pixel driving circuit 100. If poor light emission is found, the blue LED chip 56 with poor light emission can be removed and replaced with a normal blue LED chip 55 (refer to the following description). FIG. 9A to FIG. 9I ).

[0109] In addition, the blue LED chip 50 is singulated in the process of forming itself (refer to the following). FIG. 7A to FIG. 7I ), it is preferred that the blue LED chips 50 are formed on the sapphire substrate 30 in a two-dimensional arrangement of N rows and M columns corresponding to the pixels 3. In this way, the inconsistency of the element characteristics of each blue LED chip 50 can be reduced, thereby improving the uniformity of the image. In addition, when the light-emitting array 8 is attached to the LSI 7, the blue LED chip 50 can be set on the pixel driving circuit 100, so this process can also be performed very simply.

[0110] The space between adjacent blue LED chips 50 (for example, Figure 8 The separation groove 42 of the pixel driver circuit 100 requires a certain distance. The reason is that, for example, when removing the above-mentioned blue LED chip 50 with poor light emission from the pixel driver circuit 100, a space is required for inserting the front end of the micromanipulator. In addition, in order to suppress or prevent the reduction of image contrast and reduce light loss, it is preferred to fill the space between adjacent blue LED chips 50 with a material with high reflectivity and low light absorption (such as Figure 3 On the other hand, if these conditions are taken into consideration and the space between adjacent blue LED chips 50 is large, the light-emitting area of ​​each pixel 3 becomes small, the light-emitting efficiency of the blue LED chip 50 decreases, and the power consumption of the blue LED chip 50 increases. These conflicting requirements can be satisfied by making the area occupancy rate of the blue LED chip 50 relative to the area of ​​the pixel 3 be greater than 15% and less than 85%.

[0111] In addition, the luminous efficiency of the blue LED chip 50 is 1 [A / cm 2 ]~10[A / cm 2 ] is the best (see below). Fig.10 In order to suppress the decrease rate of luminous efficiency to within 20% of its maximum value, it should be suppressed to 50 [A / cm 2 Furthermore, in order to suppress the decrease rate of luminous efficiency to within 10% of its maximum value, the current density should be suppressed to 20 [A / cm 2 ] or so. In order to emit a beam with a maximum brightness of, for example, 2000 [lm] (lumens), for the blue LED display chip 1B with the lowest relative visual sensitivity, a driving current 54 of about 12 [μA] needs to be supplied to the blue LED chip 50 for each pixel. For example, for the Figure 8 For the blue LED chip 50 shown in FIG. 1 , the current density becomes 21 [A / cm 2 ] or so. Therefore, if the current injection density toward the light-emitting layer 33 (described later) of the blue LED chip 50 increases, it will fall into a vicious cycle of reducing the luminous efficiency of the blue LED chip 50 and further increasing the current density. Therefore, in order to reduce the current density, it is important to increase the area of ​​the current injection region. The area where current can be injected is Figure 8 The area of ​​the mesa portion 36 described later is consistent, so it is necessary to increase the area of ​​the mesa portion 36. The area of ​​the mesa portion 36 increases or decreases correspondingly to the area of ​​the compound semiconductor layer 31. In principle, the area of ​​the N-type contact hole 39 can be removed and the area can be close to the area of ​​the compound semiconductor layer 31. Therefore, the area occupancy rate of the compound semiconductor layer 31 relative to the area of ​​the pixel 3 is considered as an important parameter below. In addition, the above research takes the shortest distance from the end of the transparent conductive film 35 to the end of the mesa portion 36 as a premise of being short to about 1 [μm]. The driving current 54 temporarily flows in the P-side epitaxial layer 34 via the transparent conductive film 35, but if the shortest distance from the end of the transparent conductive film 35 to the end of the mesa portion 36 is long, the voltage drop in the P-side epitaxial layer 34 is large, and no current is injected at the end of the mesa portion 36.

[0112] The N-side electrode 41 and the P-side electrode 40 of the blue LED chip 50 are connected to the N-side common electrode 19 and the P-side individual electrode 20 of the pixel driving circuit 100, respectively. The N-side electrode 41 and the P-side electrode 40 are formed simultaneously in one process and connected by the same connection material (for example, see the following). Fig. 7E). It is preferred that the N-side electrode 41 and the P-side electrode 40 are connected via an anisotropic conductive film 51. The anisotropic conductive film 51 can use, for example, a resin adhesive layer in which conductive particles are dispersed. For the anisotropic conductive film 51, a conductive path can be formed in the pressure-bonded portion by the proximity of the conductive particles and the contact with each other, but no conductive path is formed in the non-pressure-bonded portion and electrical insulation is maintained. That is, the film thickness direction can be conductive by pressurization, and the film direction (the direction on the plane orthogonal to the film thickness direction) is insulated. Due to such anisotropy, it is not necessary to form a connecting film independently on the N-side common electrode 19 and the P-side individual electrode 20. Therefore, the anisotropic conductive film 51 can be formed in the entire area of ​​the pixel array 2. After the anisotropic conductive film 51 is formed, the plurality of blue LED chips 50 constituting the light-emitting array 8 are affixed to the pixel array 2 together. At this time, the blue LED chip 50 may be formed on the sapphire substrate 30 and then attached to the LSI 7 on which the pixel driving circuit 100 is formed, and then the sapphire substrate 30 may be peeled off by a laser lift-off process. Conversely, the sapphire substrate 30 may be previously attached to a peeling substrate, and then laser lift-off may be performed, and then the sapphire substrate 30 may be transferred to the transfer substrate 45 and attached to the LSI 7.

[0113] It is preferred that the light emitting array 8 be tested before being fired while being pressurized. This is because even if a blue LED chip 50 with poor light emission is found after firing, it is difficult to repair it. Therefore, after being pasted on the anisotropic conductive film 51, a light emission test of each blue LED chip 50 is performed in a state where conduction is obtained by temporary pressurization. When a blue LED chip 50 with poor light emission is detected, the blue LED chip 50 with poor light emission is removed by a micro-manipulation needle 57, and a normal blue LED chip 50 is installed. In addition, the normal LED chip is marked with a symbol 55, and the bad LED chip is marked with a symbol 56. After confirming the normal operation after the repair, the light emitting array 8 is fired while being pressurized, and the pasting process of the light emitting array 8 is completed (refer to the following). FIG. 9A to FIG. 9I ).

[0114] A light shielding reflective layer 60 is provided between the blue LED chips 50 (see Figure 3 ). The light shielding reflective layer 60 can suppress or prevent light from leaking to the adjacent blue LED chip 50, thereby preventing a decrease in image contrast. The light shielding reflective layer 60 can be filled with, for example, a composite material in which a white pigment is mixed with silicone resin.

[0115] Next, a specific configuration example of the LED display chip 1B for blue display is described. In addition, the size of each pixel 3 is, for example, 10 [μm] × 10 [μm], and the number of effective pixels is, for example, 480 × 640 (VGA specification). The size of the effective part of the pixel array 2 is, for example, 4.8 [mm] × 6.4 [mm]. The chip size of the LED display chip 1B as a whole is also matched with the row selection circuit 4, the column signal output circuit 5, and the image processing circuit 6, and is, for example, 8 [mm] × 10 [mm].

[0116] First, the pixel driving circuit 100 will be described in more detail. Figure 4 1 is an equivalent circuit diagram showing a configuration example of the pixel driving circuit 100 according to the first embodiment. Figure 4 As shown, the pixel driving circuit 100 has a selection transistor 105, a holding capacitor 108, a driving transistor 111, and a test transistor 117. They are formed monolithically on a silicon wafer W1 when manufacturing LSI 7. The selection transistor 105 is, for example, an N-type MOS transistor, and its gate terminal is connected to the row selection line (RoI) 101. In addition, the source terminal of the selection transistor 105 is connected to the column signal line (CS) 102, and the drain terminal is connected to one end of the holding capacitor 108 and the gate terminal of the driving transistor 111. The other end of the holding capacitor 108 is connected to the source terminal of the driving transistor 111 and the power supply line (Vcc) 114. The driving transistor 111 is, for example, a P-type MOS transistor, and its drain terminal is connected to the P-side individual electrode 20. The anode terminal of the blue light emitting element 13 (here, the blue LED chip 50) and the source terminal of the test transistor 117 are connected in parallel to the P-side individual electrode 20. The gate terminal of the test transistor 117 is connected to the test signal line (TE) 116. The cathode terminal of the blue light emitting element 13 and the drain terminal of the test transistor 117 are both connected to the ground line (GND) 115. In addition, the circuit configuration of the pixel driving circuit 100 is not limited to Figure 4 , various known circuit structures can be used.

[0117] When row I of the pixel array 2 is selected, the row selection line (RoI) 101 of row I is activated. At this time, in pixel 3 (I, J), the selection transistor 105 is turned on, and the column signal is applied to the gate terminal of the driving transistor 111 from the column signal line (CS) 102, and a driving current 54 flows in the blue light-emitting element 13 from the power supply line (Vcc) 114. If the selection period of row I ends and the selection transistor 105 is turned off, the potential of the gate terminal of the driving transistor 111 is maintained by the holding capacitor 108. Therefore, during the period from the end of the selection period to the next selection of row I, the driving current 54 continues to flow in the blue light-emitting element 13.

[0118] The test transistor 117 is a switch circuit that selectively short-circuits the P-side individual electrode 20 and the N-side common electrode 19, and is provided, for example, to test whether the pixel driving circuit 100 operates normally and whether the outputs of the row selection circuit 4 and the column signal output circuit 5 are normal. The reason is as follows.

[0119] First, the blue light emitting element 13 must be provided only on a good LSI 7. Therefore, in the LSI 7 (see Figure 1 Before connecting the light emitting array 8 (upper left figure), it is necessary to test LSI 7 to select whether it is a good product. At this time, the functions of the parts not related to the pixel driving circuit 100 can be tested by the usual circuit testing technology. Here, in the pixel driving circuit 100 without the test transistor 117, no current can flow in the pixel 3 before the blue light emitting element 13 is connected to the pixel driving circuit 100, so it is difficult to perform the above-mentioned test. Therefore, a test transistor 117 is formed in each pixel driving circuit 100.

[0120] When testing the pixel driving circuit 100, the test transistor 117 is turned on. In this way, the N-side common electrode 19 and the P-side individual electrode 20 are short-circuited, so that the drive current 54 flowing from the power line (Vcc) 114 to the blue light emitting element 13 can be measured. In this way, almost all defects of the LSI 7, including the defect of the pixel 3, can be detected. In addition, Figure 2 , Figure 3 In the embodiment, an N-side common electrode 19 and a P-side individual electrode 20 are provided for each pixel, but the N-side common electrode 19 can also be shared by multiple pixels. Therefore, it is also necessary to test the driving circuit of the pixel without the N-side common electrode 19. In this case, in the test mode in which the test transistor 117 is turned on, the test transistor 117 can be configured in such a way that the P-side individual electrode 20 is directly connected to the wiring connected to the N-side common electrode 19. In the case where it is difficult to connect the wiring connected to the N-side common electrode 19 in terms of layout, the P-side individual electrode 20 can also be directly connected to the GND wiring. This structure is composed of a so-called upper and lower electrode chip with a structure in which a light-emitting element is sandwiched between an N-side electrode and a P-side electrode, and can also be applied when only one electrode of each light-emitting element is directly connected to the pixel driving circuit.

[0121] Next, a case where the configuration of the pixel driving circuit 100 is realized by a four-layer wiring process is taken as an example for description. Figure 5 2 is a perspective top view showing an example of a pattern layout of the pixel driving circuit 100. Fig. 6A as well as Figure 6B is a cross-sectional structural diagram of the pixel driving circuit 100 . Fig. 6A Indicates along Figure 5 The cross-sectional structure of the single-point chain line BB. Figure 6B Indicates along Figure 5 In addition, in these figures, each wiring layer is referred to as the first to fourth metal wiring layers 210 to 240 in order from the bottom layer (ie, the layer farthest from the surface) to the top layer (ie, the layer closest to the surface).

[0122] The fourth layer of metal wiring 240 (the top layer) is composed of an N-side common electrode 19 and a P-side individual electrode 20 electrically connected to the blue LED chip 50. The upper surface of the fourth layer of metal wiring 240 is exposed in the same plane as the upper surface of the pixel driving circuit 100. Therefore, the upper surface of the pixel driving circuit 100 becomes a flat surface. The third layer of metal wiring 230 is composed of a row selection line (RoI) 101 and a power line (Vcc) 114. The second layer of metal wiring 220 is composed of a column signal line (CS) 102, a ground line (GND) 115, and a test signal line (TE) 116. The first layer of metal wiring 210 (the bottom layer) is composed of a plurality of local wirings within the pixel 3. In addition, in the first to fourth layers of metal wiring 210 to 240, each wiring is separated by an interlayer insulating layer 250 formed, for example, using SiO2.

[0123] In addition, the gate poly-Si layer 206 formed between the first metal wiring 210 and the P-well layer 201 functions as the gate electrodes of the selection transistor 105 (N-type MOS transistor) and the drive transistor 111 (P-type MOS transistor) and one electrode of the retention capacitor 108.

[0124] In addition, an N-well layer 202, an STI (Shallow Trench Isolation) layer 203, and N+ diffusion layers 204a and 204b are formed on the P-well layer 201 of the silicon substrate 200. The N-well layer 202 functions as a source electrode of the driving transistor 111 and the other electrode of the holding transistor 108, and forms a holding capacitor of the holding transistor 108 between the N-well layer 202 and the gate poly-Si layer 206. In addition, a P+ diffusion layer 205 that functions as a drain electrode of the driving transistor 111 is formed on the N-well layer 202. The STI layer 203 has a function of isolating elements, and is formed using, for example, SiO2. The N+ diffusion layer 204a functions as a source electrode of the selection transistor 105, and the N+ diffusion layer 204b functions as a drain electrode of the selection transistor 105.

[0125] These layers 201 to 205 and the gate poly-Si layer 206 are electrically connected to the first to fourth metal wirings 210 to 240 through contact holes or through-holes. The completed silicon wafer W1 is tested as it is before LSI 7 is cut out, and the locations of defective chips are recorded.

[0126] Next, the InGaN-based blue LED chip 50 is taken as an example and its manufacturing process is described. FIG. 7A to FIG. 7I This is a schematic diagram for explaining the manufacturing process of the blue LED chip 50 . Fig. 7A This is a diagram for explaining the process of epitaxially growing a compound semiconductor layer 31 on a sapphire substrate 30 and depositing a transparent conductive film 35 thereon. Figure 7B This is a diagram for explaining a step of forming the mesa portion 36 in the epitaxial layer. Figure 7C This is a diagram for explaining the step of forming the protective film 37 . Fig.7D It is a diagram for explaining the process of forming the contact holes 38 and 39 . Fig. 7E It is a diagram for explaining the process of forming the P-side electrode 40 and the N-side electrode 41 . Figure 7F This is a diagram for explaining the process of forming the separation groove 42 . Figure 7G This is a diagram for explaining a step of attaching the separated blue LED chips 50 to the holding substrate 43 . Figure 7H This is a diagram for explaining a process of separating each blue LED chip 50 from the sapphire substrate 30 . Fig.7I This is a diagram for explaining a step of attaching each blue LED chip 50 to the transfer substrate 45 .

[0127] like Fig. 7A As shown, on the main surface of a sapphire substrate 30 (e.g., 4 [inch] diameter) formed with a concave-convex pattern, an N-side epitaxial layer 32, a light-emitting layer 33, and a P-side epitaxial layer 34 are epitaxially grown in sequence, for example, using an MOCVD device, to form a compound semiconductor layer 31. The N-side epitaxial layer 32 is formed, for example, by a complex multilayer structure (not shown) including an N-side buffer layer, which is composed of a multilayer film such as a buffer layer, an undoped GaN layer, an N-type contact layer (n-GaN layer), and a superlattice layer. The light-emitting layer 33 is, for example, a multiple quantum well layer in which a quantum well layer (not shown) composed of InGaN and a barrier layer (not shown) composed of GaN are repeatedly stacked. The P-side epitaxial layer 34 is formed, for example, by a multilayer structure (not shown) including a GaN layer, a p-type AlGaN layer, a p-type GaN layer, and a p-type contact layer (p-GaN). After the compound semiconductor layer 31 is formed, a transparent conductive film 35 is formed on the P-side epitaxial layer 34 using a transparent conductive material such as ITO.

[0128] In addition, the area occupied by the blue LED chip 50 is relatively small, but even so, in order to inject current into the entire area of ​​the P-side epitaxial layer 34, the resistance of the P-side epitaxial layer 34 is relatively high. In addition, if the P-side electrode 40 and the N-side electrode 41 using a metal material are directly stacked on the P-type epitaxial layer 34, the reflectivity of the interface between the P-side electrode 40 and the N-side electrode 41 and the P-type epitaxial layer 34 formed using GaN is reduced, resulting in a decrease in light extraction efficiency. Therefore, it is preferred to form a transparent conductive film 35 and a protective film 37 described later between the P-type epitaxial layer 34 and the P-side electrode 40 and the N-side electrode 41 to separate the two and lengthen their shortest distance.

[0129] like Figure 7B As shown, the transparent conductive film 35 is patterned. Thereafter, the P-side epitaxial layer 34 , the light emitting layer 33 , and a portion of the N-side epitaxial layer 32 are removed by etching, thereby forming a mesa portion 36 in the compound semiconductor layer 31 .

[0130] like Figure 7C As shown, for example, a protective film 37 is formed on the entire surface of the exposed surface of the compound semiconductor layer 31 and the surface of the patterned transparent conductive film 35 using SiO2. At this time, the protective film 37 also covers the side wall of the mesa portion 36. Therefore, the protective film 37 can prevent leakage of the PN junction portion of the side wall portion exposed by the formation of the mesa portion 36. In addition, the protective film 37 can separate and electrically insulate the transparent conductive film 35 and the N-side electrode 41. Fig.7D As shown in FIG. 1 , a portion of the protective film 37 on the patterned transparent conductive film 35 is removed to form a P-side contact hole 38. In addition, a portion of the protective film 37 on the bottom surface of the recessed portion between the mesa portions 36 is removed to form an N-side contact hole 39. The recessed portion is the portion of the compound semiconductor layer 31 that is removed by etching (see FIG. 1 ). Figure 7B ).

[0131] like Fig. 7E As shown, an electrode film having a multilayer structure of, for example, Al / Ni / Pt / Ni / Au is formed on the protective film 37 and the contact holes 38 and 39 by a vapor deposition method or the like. Then, a portion of the electrode film is removed to form a P-side electrode 40 and an N-side electrode 41. In addition, in the mesa portion 36, the upper surface of the P-side electrode 40 is at the same height as the upper surface of the N-side electrode 41. By making the upper surfaces of the two electrodes 40 and 41 the same surface, the pasting process of the light emitting array 8 on the LSI 7 described later becomes easy.

[0132] like Figure 7FAs shown in FIG. 1 , in order to separate the blue LED chips 50 from each other, a separation groove 42 reaching the surface of the sapphire substrate 30 is formed on the bottom surface of the recessed portion between the terrace portions 36. Thereafter, the sapphire substrate 30 is further ground to be thinner and cut into units of each light emitting array 8 (see FIG. 1 ). Figure 1 ). In addition, the thickness of the sapphire substrate 30 after grinding is about 30 [μm] to 200 [μm]. In addition, the cutting of the sapphire substrate 30 can be carried out in the same manner as the usual LED chip cutting, for example, by using laser stealth cutting. In addition, it is preferred that the cutting groove (not shown) for dividing the sapphire substrate 30 is provided separately from the separation groove 42. If so, it is possible to suppress or prevent damage to the light-emitting layer 33 caused by the laser irradiating the back side of the sapphire substrate 30 when the sapphire substrate 30 is cut, for example, by using laser stealth cutting. By Figure 7F In the process, blue LED chips 50 of the amount of one LED display chip are prepared while being placed on a sapphire substrate 30 divided into units of each light-emitting array 8. In addition, the reason for cutting and separating the sapphire substrate 30 into units of each light-emitting array 8 is that LSI 7 is generally larger than the light-emitting array 8, so connecting a plurality of connected light-emitting array 8 groups relative to the corresponding LSI 7 groups at one time will cause more waste. For example, if the sapphire wafer W2 is bonded to the silicon wafer W1, an unused waste area has to be configured on the side of the sapphire wafer W2. Therefore, the sapphire wafer and the epitaxial layer formed thereon cannot be efficiently utilized. If an LSI 7 of the same size as the light-emitting array 8 can be formed, it is not impossible to bond the wafer to the wafer as a whole. However, in addition to the pixel driving circuit 100, the LSI 7 needs to be equipped with a row selection circuit 4, a column signal output circuit 5, an image processing circuit 6, etc. Therefore, it is difficult to make the LSI 7 the same size as the light-emitting array 8.

[0133] like Figure 7G As shown, the P-side electrode 40 and the N-type electrode 41 of each blue LED chip 50 are attached to the holding substrate 43 via an adhesive layer 44 .

[0134] In addition, if Figure 7H As shown, the sapphire substrate 30 is separated from the compound semiconductor layer 31 by, for example, laser lift-off method, while the P-side electrode 40 and the N-type electrode 41 of each blue LED chip 50 are oriented vertically downward. That is, the sapphire substrate 30 is removed from each blue LED chip 50. In addition, Figure 7H The process is Figure 7G It can also be implemented in the state.

[0135] like Fig.7IAs shown, the back surface of each blue LED chip 50 (i.e., the main surface on the N-side epitaxial layer 32 side) is attached to the transfer substrate 45 via the adhesive layer 46. In addition, each blue LED chip 50 is in a state ready to be attached to the light emitting array 8 of the LSI 7 with the P-side electrode and the N-type electrode 41 facing vertically upward.

[0136] exist Figure 8 Show Fig.7I An example of a processed blue LED chip 50 . Figure 8 FIG. 2 is a top view showing an example of a blue LED chip 50 provided in the pixel array 2. Figure 8 In the state where the width of the separation groove 42 is 1.6 μm relative to the size of the pixel 3 (e.g., 10 [μm] × 10 [μm]), the area occupancy rate of the compound semiconductor layer 31 relative to the area of ​​the pixel 3 in each blue LED chip 50 is approximately 71%. In addition, the area occupancy rate of the mesa portion 36 relative to the area of ​​the pixel 3 is, for example, 54%.

[0137] Next, a method of attaching and electrically connecting the light emitting array 8 to the LSI 7 will be described. The light emitting array 8 is provided only on a chip portion of good quality among the chip portions of the LSI 7 formed on the silicon wafer W1.

[0138] FIG. 9A to FIG. 9I This is a schematic diagram for explaining a method of providing the blue LED chip 50 in the image driving circuit 100 . Fig.9A This is a diagram for explaining a process of attaching the blue LED chip 50 to the image driving circuit 100 . Fig. 9B This is a diagram for explaining a process of performing a light emission test on the pixel 3 . Fig. 9C This is a diagram for explaining a process of removing the blue LED chip 56 in which light emission failure is detected from the image driving circuit 100 . Fig.9D This is a diagram for explaining the process of mounting a replacement normal blue LED chip 55 . Fig.9E This is a diagram for explaining the process of performing a re-emission test on the pixel 3. Fig.9F This is a diagram for explaining the process of firing the LED display chip 1 while applying pressure. Figure 9G This is a diagram for explaining a process of forming a resist pattern 58 on the blue LED chip 50 . Figure 9H This is a diagram for explaining a process of forming the light-shielding reflective layer 60 on the pixel array 2 . Fig.9I 58 is a diagram for explaining the process of removing the resist pattern 58. FIG. 9A to FIG. 9IIn FIG. 1 , as the structure of LSI 7, electrodes 19 and 20 connected to the blue LED chip 50 and an interlayer insulating film 250 are mainly shown, and other components are omitted. Fig. 9B as well as Fig.9E The zigzag arrows represent the blue light emitted by self-luminescence.

[0139] First, if Fig.9A As shown, an anisotropic conductive film 51 is formed on a pixel driving circuit 100 of an LSI 7 formed on a silicon wafer W1, and a light emitting array 8 is pasted on the anisotropic conductive film 51. Thus, a blue LED chip 50 is set on the pixel driving circuit 100 for each pixel 3. At this time, high-precision alignment is performed so that the P-side electrode 40 and the N-side electrode 41 of the blue LED chip 50 are accurately opposite to the P-side individual electrode 20 and the N-side common electrode 19 of the pixel driving circuit 100, respectively. In addition, in the inspection of this process, it is possible to detect portions of the light emitting array 8 that lack blue LED chips 50, blue LED chips 50 that have obvious shape abnormalities, etc. These can be detected by the process described later (for example, refer to Fig. 9C as well as Fig.9D ) The same method is used to install or replace the normal blue LED chip 50.

[0140] like Fig. 9B As shown, the silicon wafer W1 before cutting out the LSI 7 is pressed, for example, by a transparent substrate 52 (e.g., a glass plate) laminated with a transparent resin cushion layer 53. By this pressurization process, the blue LED chip 50 is temporarily fixed to the pixel driving device 100 via the anisotropic conductive film 51. In this state, a driving current 54 flows through each pixel 3 to perform a light emission test.

[0141] like Fig. 9C As shown, when a poorly emitting LED chip 56 that does not emit a predetermined amount of light is detected by the light emission test, the LED chip 56 is removed from the anisotropic conductive film 51 by a micro-manipulation needle 57. This process is performed before the pressure firing, so the poorly emitting LED chip 56 can be removed from the pixel driving circuit 100 relatively easily.

[0142] like Fig.9D As shown, a normal blue LED chip 50 is provided in the pixel 3 from which the poorly emitting LED chip 56 is removed. At this time, the anisotropic conductive film 51 removed together with the poorly emitting LED chip 56 can be added by, for example, a micropipette to repair the removed portion.

[0143] like Fig.9E As shown, the mounted blue LED chip 50 is again Fig. 9BIn addition, if a blue LED chip 56 with poor light emission is detected again, the same light emission test can be performed again. Figure 9C to Figure 9E process.

[0144] like Fig.9F As shown, when no blue LED chip 56 with poor light emission is detected, the silicon wafer W1 on which the LSI 7 is formed is fired while being pressed, and the blue LED chip 50 is fixed to the pixel driving circuit 100 via the anisotropic conductive film 51 .

[0145] Next, if Figure 9G As shown in FIG. 1 , a resist pattern 58 is formed on the back surface of the blue LED chip 50. At this time, the resist pattern 58 is also formed on the surface other than the pixel array 2.

[0146] like Figure 9H As shown, in a state where the resist pattern 58 is formed, a light-shielding reflective layer 60 is formed. For example, the light-shielding reflective layer 60 is applied to the entire surface of the LSI 7 of the silicon wafer W1 and baked (fired). In addition, as the light-shielding reflective layer 60, for example, a resin in which a white pigment is dispersed at a high concentration can be used. For example, titanium oxide particles can be used as the white pigment. In addition, it is preferred that the particle size is as small as possible.

[0147] like Fig.9I As shown in FIG. 5 , the thin light-shielding reflective layer 60 remaining on the resist pattern 58 is etched away, and the resist pattern 58 is peeled off. Through this treatment, a dam layer 61 is formed between adjacent blue LED chips 50 using the same material as the light-shielding reflective layer 60. In addition, the boundary between the light-shielding reflective layer 60 and the dam layer 61 is at the same height as the back surface of the blue LED chip 50.

[0148] Through the above steps, the light emitting array 8 is provided on the LSI 7. Figure 9H In the process, white pigment is used as the material for forming the light-shielding reflective layer 60, but if the thickness of the light-shielding reflective layer 60 is about several μm, it is impossible to completely block the leakage of light. In order to further suppress the leakage of light, it is more effective to use black pigment to absorb light. However, black pigment causes a significant reduction in light output. This is because: when white pigment is used, the light returned to the blue LED chip 50 due to reflection is released again on the surface and has the effect of increasing the brightness, but when black pigment is used, this effect disappears. However, in this embodiment, white pigment is used in the light-shielding reflective layer 60 in order to give priority to brightness, but when contrast is given priority, a light-shielding layer using black pigment can be used instead of the light-shielding reflective layer 60.

[0149] About Fig. 9C as well as Fig.9DWhen repairing the defective light-emitting positions of the light-emitting array 8 according to this embodiment, it is necessary to repair eight positions on average for each LED display chip 1. In addition, without repair, the pass rate of obtaining completely good products is almost zero. Therefore, the structure of the present invention has a very large effect in manufacturing low-defect LED display chips 1 with a high pass rate.

[0150] The width of the separation groove 42 is very important for reliably implementing the repair of the light-emitting defective position. For example, the complete repair rate is 67% when the width of the separation groove 42 is 1.6μm, but the complete repair rate is halved when the width of the separation groove 42 is less than 1μm. This is because: due to contact with the adjacent pixel 3 during repair, the normal blue LED chip 55 is defective or the replacement normal blue LED chip 55 cannot be accurately set. Such troubles can be improved if the operating accuracy of the micro-manipulation needle 57 used for repair is improved, but even so, it is considered that the separation groove 42 needs to be more than 1μm wide.

[0151] On the other hand, the complete repair rate is increased to 90% when the width of the separation groove 42 is increased to 2.5 μm. However, the width of the separation groove 42 cannot be infinitely increased for easy repair. This is because the current density flowing in the blue LED chip 50 increases, its luminous efficiency decreases, and power consumption increases. Fig.10 This is a graph showing the current dependence of the luminous efficiency of blue LED chips 50 of various shapes manufactured by different manufacturers. 2 ]~10[A / cm 2 In order to suppress the luminous efficiency to a decrease within 10% of the maximum value, the maximum should be suppressed to 20 [A / cm 2 ], in order to suppress the decrease within 20%, it should be suppressed to 50 [A / cm 2 ] or less. In order to emit a beam with a maximum brightness of 2000 [lm] (lumens), a current of about 12 [μA] needs to flow for each pixel in the blue LED display chip 1B with the lowest relative visual sensitivity. In this case, for example, Figure 8 The current density flowing through the blue LED chip 50 is 21 [A / cm 2] or so. Therefore, there is a concern that power consumption increases and brightness drops below the maximum brightness of 2000 [lm]. However, it is not impossible to further halve the area of ​​the table portion 36. In this case, the area occupancy rate of the blue LED chip 50 relative to the area of ​​the pixel 3 is 34%. Therefore, the following design is required, that is, when pursuing low power consumption in high-cost high-end products, the area occupancy rate of the blue LED chip 50 is increased, and conversely, when giving priority to cost and allowing an increase in power consumption, the area occupancy rate of the blue LED chip 50 is reduced. The design of the blue LED chip 50 should be selected while taking into account the cost increase caused by the increase in the pass rate and the extent to which the maximum brightness specification is guaranteed.

[0152] In addition, the relative visual sensitivity of red is more than 4 times that of blue. Therefore, in the case of the red LED display chip 1R, if the luminous efficiency of the red LED chip is made the same as that of the blue LED chip 50, the driving current 54 required by the red LED chip is about half of that of the blue LED chip 50. (Compared to the contribution of blue to brightness, the contribution of red is about twice as large. Therefore, it will not be 1 / 4.) In this case, there is a possibility that the area occupancy of the red LED chip will further become about half (17%) of the above.

[0153] In addition, the green LED display chip 1G can also be formed in the same manner as the blue LED display chip 1B. The major difference is only the light-emitting layer 33, and the manufacturing process is not much different from the blue LED chip 50. In the case of the red LED chip, the red LED chip is formed using AlInGaNP, or the substrate material and the method of stripping the substrate are changed, but there is no structural change.

[0154] In addition, the blue LED display chip 1B described above was actually operated, and the brightness became 182 [lm], and the contrast was above the measurement limit. In addition, the maximum power consumption was 40 [W]. If it is combined with the red LED display chip 1R and the green LED display chip 1G of the same performance, it can ensure the performance of the maximum brightness of 2000 [lm].

[0155] <First Modification of First Embodiment>

[0156] In the above-mentioned embodiment, each LED is singulated (see Figure 8 ), but is not limited to this example, and the LEDs of the pixels 3 adjacent to each other in the column direction may be integrated into a single chip. Fig.11A FIG. 2 is a top view showing a modified example of a blue LED chip 50 provided in the pixel array 2. Fig.11AAs shown, each blue LED of two pixels 3 adjacent to each other in the column direction can be integrated without separating the compound semiconductor layers 31 of the two. At this time, no separation groove 42 in the row direction is formed between the two blue LEDs adjacent to each other up and down (in the column direction). Therefore, the area of ​​the mesa portion 36 of each blue LED can be enlarged to reduce the current density flowing in the blue LED chip 50, thereby improving its luminous efficiency. In addition, the two blue LEDs adjacent to each other in the column direction can further enlarge the area of ​​the mesa portion 36 by sharing the N-type contact hole 39, thereby further improving the luminous efficiency. Fig.11A In the case of Figure 8 In comparison, the area occupancy of the compound semiconductor layer 31 is increased by about 10% (77.28 / 70.56=1.095), and the area of ​​the mesa portion 36 is increased by about 20% (65.28 / 54.35=1.201). As a result, the conversion efficiency is improved by 2-3%. Moreover, the size of a blue LED chip 50 is larger than Figure 8 Therefore, the repair work of the light emitting array 8 (for example, refer to Fig. 9C as well as Fig.9D ) operation becomes easier, thereby improving the repair efficiency. When the pixel 3 is made smaller in order to improve the resolution of the image, the repair operation becomes more difficult as the pixel 3 is miniaturized. However, if a certain amount ( Fig.11A If the blue LEDs of the pixels 3 connected in the column direction are integrated, the repair efficiency can be further improved. Even if multiple blue LEDs are integrated, the number of pixels 3 to be repaired will not change much. On the contrary, the cost can be reduced by making the repair efficient. However, the blue LEDs of the pixels 3 connected in the column direction are integrated, so light leakage is slightly generated between the pixels 3 through the compound semiconductor layer 31 that remains integrated. Therefore, the contrast in the column direction is slightly reduced.

[0157] <Second Modification of First Embodiment>

[0158] Or, not limited to Figure 8 as well as Fig.11A As an example, the LEDs of the pixels 3 adjacent to each other in the row direction may be integrated. Fig. 11B FIG. 2 is a top view showing another variation of a blue LED chip disposed in the pixel array 2. Fig. 11B As shown, each blue LED of two pixels 3 adjacent to each other in the row direction can be integrated by not separating each compound semiconductor layer 31 therebetween. In this case, no separation groove 42 in the column direction is formed between two blue LEDs adjacent to each other on the left and right (in the row direction). Therefore, the area of ​​the mesa portion 36 of each blue LED can be enlarged to reduce the current density flowing in the blue LED chip 50, thereby improving its luminous efficiency. Fig. 11B In the case of Figure 8 In comparison, the area occupancy rate of the compound semiconductor layer 31 is increased by about 10%, and the area of ​​the terrace portion 36 is increased by about 17% (63.47 / 54.35=1.168). As a result, the conversion efficiency is improved by 1-2%. In addition, the size of a blue LED chip 50 is larger than Figure 8 The size of the light array 8 is reduced, so the operation of the repair work of the light array 8 becomes easier, and the repair efficiency can be improved. When the pixel 3 is reduced in size to improve the resolution of the image, the repair becomes more difficult as the pixel 3 is miniaturized. However, if a certain amount ( Fig. 11B If the blue LEDs of the pixels 3 connected in the row direction are integrated, the repair efficiency can be further improved. Even if multiple blue LEDs are integrated, the number of pixels 3 to be repaired will not change much. On the contrary, the cost can be reduced by making the repair more efficient. However, the blue LEDs of the pixels 3 connected in the row direction are integrated, so a slight light leakage occurs between the pixels 3 through the compound semiconductor layer 31 that remains integrated. Therefore, the contrast in the row direction is slightly reduced. In addition, the effect of improving the conversion efficiency of the blue LED chip 50 is better than that of the conventional method. Fig.11A The situation is small, Fig. 11B The example has the advantage that the contrast in the vertical direction of the image does not deteriorate. Because vertical resolution is sometimes more important than horizontal resolution, Fig. 11B The method is suitable for such use.

[0159] <Third Modification of First Embodiment>

[0160] Or, not limited to Figure 8 , Fig.11A as well as Fig. 11B As an example, it is also possible to integrate LEDs of multiple pixels 3 arranged in two dimensions with n rows and m columns. In addition, n is a positive integer greater than 2 and less than N, and m is a positive integer greater than 2 and less than M. In this way, the pass rate can be maintained and the resolution can be improved. Below, an LED display chip 1 in which the size of each pixel 3 is 5 [μm] × 5 [μm] and the number of effective pixels is 1080 × 1920 (full HD) is cited as an example for explanation. In addition, the effective part size of the pixel array 2 is, for example, 5.4 [mm] × 9.6 [mm]. In addition, the chip size of the entire LED display chip 1 is also matched with the row selection circuit 4, the column signal output circuit 5, and the image processing circuit 6, and is, for example, 8 [mm] × 15 [mm].

[0161] Fig. 11C 2 is a top view showing another modified example of the blue LED chip 50 provided in the pixel array 2. Fig. 11CIn the embodiment, the blue LEDs (especially their compound semiconductor layers 31) of the 16 pixels 3 arranged two-dimensionally in 4 rows and 4 columns are not separated but integrated. In this case, no separation grooves 42 are formed between the blue LEDs adjacent in the row direction and the column direction. Therefore, the area of ​​the mesa portion 36 of each blue LED can be enlarged to reduce the current density flowing in the blue LED chip 50, thereby improving its luminous efficiency. In addition, Fig. 11C In the embodiment, two blue LEDs adjacent to each other vertically (in the column direction) can share the N-type contact hole 39, thereby further increasing the area of ​​the mesa portion 36 and further improving the luminous efficiency.

[0162] In the third variant, from a viewpoint similar to the first and second variants, each blue LED of 16 pixels 3 in 4 rows and 4 columns is integrated to have a size of 20 [μm] × 20 [μm]. In addition, the size of the compound semiconductor layer 31 is 18 [μm] × 18 [μm]. This is because: Figure 8 In the same structure, the blue LED chip 50 is smaller and the repair of the light emitting array 8 is more difficult. Fig. 11C In this case, the area occupancy rate of the compound semiconductor layer 31 relative to the total area of ​​16 pixels 3 is 81%. In order to improve the repair success rate of the large-scale blue LED chip 50, the width of the separation groove 42 is increased to 2 [μm]. The configuration of the blue LED arranges the upper and lower pairs of pixels 3 that share the N-side contact hole 39 in two dimensions in the same pattern. The shape and position of the mesa portion 36 of each pixel 3 are adjusted in such a way that the area of ​​each pixel 3 becomes the same. Therefore, although the center position of the mesa portion 36 relative to the area of ​​the pixel 3 may be slightly different depending on the pixel 3, it is only a slight difference and will not cause a big problem to the image quality of the image projected by the LED display chip 1. The area occupancy rate of the mesa portion 36 relative to the area of ​​the pixel 3 is 58%.

[0163] The size of the pixel 3 in the third modification example is, for example, smaller than that in the first embodiment. Fig. 11C The transparent conductive film 35 is not formed in the P-side electrode 40, and the P-side epitaxial layer 34 is directly in contact with the P-side epitaxial layer 34. The sheet resistance of the P-side epitaxial layer 34 is as high as 5×10 4 [Ω], so there is a problem that the driving voltage of the pixel 3 increases by about 0.5 V if it is in direct contact, but there is an advantage that the technical problem of forming a fine pattern of the transparent conductive film 35 can be avoided.

[0164] In addition, if compared with the first embodiment (refer to Figure 8) Similarly, if the width of the separation groove 42 is made 1.6 [μm], the area occupancy rate of the compound semiconductor layer 31 is 85%, and the area occupancy rate of the terrace portion 36 increases to 64%. As for the width of the separation groove 42, it is preferably narrow as in the first embodiment in terms of reducing power consumption, but it is preferably wide as in the third variant in terms of improving the pass rate. In addition, when the sizes of the monolithic pixels 3 are made 5 [μm] × 5 [μm] and the width of the separation groove 42 is made 2 [μm], the area occupancy rate of the compound semiconductor layer 31 becomes 36%, and the area occupancy rate of the terrace portion 36 is, for example, 5%. In this case, the injection density of the current becomes very high, up to 10 times, and the luminous efficiency is significantly reduced. Therefore, the power consumption increases and the maximum brightness decreases. In addition, such a small blue LED chip 50 is difficult to operate, so the current situation is that the repair pass rate has to be reduced. However, in the third variant, these problems can be avoided and high-resolution LED display chips can be manufactured. In the third variant, a decrease in contrast may occur due to a slight inter-pixel leakage of light between the connected 16 pixels, but the contrast is very high when the entire screen is viewed in full, so the advantage over liquid crystal displays and the like is not lost.

[0165] As described above, according to the present embodiment, the image forming element 1 is an image forming element 1 having a plurality of pixels 3 and projecting and displaying the emitted light of the pixel 3, and is configured to include: a light emitting element 10 including a light source 50 for emitting light, and a mounting substrate 7 on which a plurality of light emitting elements 10 are arranged on a mounting surface, a plurality of light sources 50 monolithically including at least one pixel 3 are provided, the light sources 50 respectively have a plurality of power supply electrodes 40, 41 arranged on the same surface, the mounting substrate 7 has: a driving circuit 100 for driving the light source 50, and electrodes 19, 20 arranged on the mounting surface and electrically connected to the power supply electrodes 40, 41 of the light source 50, and in each pixel 3, the area occupancy rate of the light source 50 relative to the area of ​​the pixel 3 is greater than 15% and less than 85%.

[0166] According to this configuration, when the light emitting element 10 including the light source 50 is arranged on the mounting surface of the mounting substrate 7, the power supply electrodes 40 and 41 arranged on the same surface of the light source 50 can be electrically connected to the electrodes 19 and 20 arranged on the mounting surface. In addition, for example, when replacing a defective light source 56, it is relatively easy and efficient to remove the defective light source 56 and install a normal light source 55. In addition, since each of the plurality of light sources 50 includes at least one pixel 3 and is monolithic, it is possible to suppress the leakage of light to the adjacent pixel 3 through the inside of the light source 50. That is, it is possible to suppress the leakage of light toward the dark pixel adjacent to the bright pixel. Therefore, it is possible to suppress or prevent the reduction in the contrast of the image formed by the projected light of the pixel 3 and the color mixing of the emitted light between the adjacent pixels 3. In addition, if the light source 50 includes a plurality of pixels 3 and is monolithic, the number of light sources 50 to which the light emitting element 10 including the light source 50 is arranged on the mounting substrate 7 can be reduced, and the difficulty of its operation can also be improved. Therefore, the working efficiency is improved, and mass production is also facilitated. Furthermore, the area occupancy rate of each light source 50 relative to the area of ​​each pixel 3 is 15% or more and 85% or less. In this way, it is possible to satisfy the following in a good balance: suppressing the leakage of light to the adjacent pixels 3, suppressing the reduction of the luminous efficiency and the increase of the power consumption accompanying the reduction of the luminous area, and suppressing the reduction of the operation (for example, the replacement operation of the light source 50) accompanying the reduction of the interval between the adjacent light sources 50. Therefore, it is possible to manufacture an image forming element with excellent color rendering and high contrast with low defects and high yield.

[0167] In addition, according to the present embodiment, the image forming element 1 is an image forming element 1 having a plurality of pixels 3 and projecting and displaying the emitted light of the pixel 3, and is configured to include: a light-emitting element 10 including a light source 50 that emits light, and a mounting substrate 7 on which a plurality of light-emitting elements 10 are arranged on a mounting surface, a plurality of light sources 50 that are monolithic and include at least one pixel 3 are provided, each light source 50 has at least one power electrode 40, 41 on a surface opposite to the mounting substrate 7, the mounting substrate 7 has: a driving circuit 100 that drives the light source 50, and electrodes 19, 20 that are arranged on the mounting surface and electrically connected to the power electrodes 40, 41 of the light source 50, the driving circuit 100 includes: a switching circuit 117 that selectively short-circuits the electrodes 19, 20 that are electrically connected to the power electrodes 40, 41 of the light source 50 with other electrodes or wirings in the driving circuit 100.

[0168] According to this configuration, when the light emitting element 10 including the light source 50 is disposed on the mounting surface of the mounting substrate 7, at least one power supply electrode 40, 41 disposed on the surface opposite to the mounting substrate 7 can be electrically connected to the electrodes 19, 20 disposed on the mounting surface. In addition, for example, when replacing a defective light source 56, it is possible to relatively easily and efficiently remove the defective light source 56 and install a normal light source 55. In addition, since the plurality of light sources 50 are monolithic each including at least one pixel 3, it is possible to suppress the leakage of light to the adjacent pixel 3 through the inside of the light source 50. That is, it is possible to suppress the leakage of light to the dark pixel adjacent to the bright pixel. Therefore, it is possible to suppress or prevent the reduction in the contrast of the image formed by the projected light of the pixel 3 and the color mixing of the emitted light between the adjacent pixels 3. In addition, if the light source 50 is monolithic including a plurality of pixels 3, the number of light sources 50 to be disposed on the mounting substrate 7 by the light emitting element 10 including the light source 50 can be reduced, and the difficulty of its operation can also be improved. Therefore, the operation efficiency is improved, and mass production is also facilitated. In addition, the driving circuit 100 includes the switch circuit 117, so before the light source 50 is connected to the driving circuit 100, the switch circuit 117 is used to selectively short-circuit the electrodes 19 and 20 with other electrodes or wirings in the driving circuit 100, so that it is possible to detect whether the driving circuit 100 is normal or defective. Therefore, an image forming element with excellent color rendering and high contrast can be manufactured with low defects and high yield.

[0169] In the above-mentioned image forming element 1 , the light source 50 is configured as a compound semiconductor light emitting diode.

[0170] According to this configuration, power consumption can be suppressed to a relatively low level.

[0171] In the above-mentioned image forming element 1, the structure is as follows: the mounting substrate 7 is a semiconductor substrate Wi, and a driving circuit 100, an arrangement selection circuit 4 for selecting pixels 3 arranged along a specified direction (column direction), and a signal output circuit 5 for outputting a driving signal to the driving circuit 100 of the light source 50 that drives the pixels 3 selected by the arrangement selection circuit 4 are formed in a single chip on the mounting substrate 7.

[0172] According to this configuration, the drive circuit 100 , the array selection circuit 4 , and the signal output circuit 5 can be formed efficiently and compactly.

[0173] The image forming element 1 is further provided with an anisotropic conductive film 51 at least provided on the electrodes 19 and 20 of the mounting substrate 7 , and the power supply electrodes 40 and 41 of the light sources 50 are provided on the electrodes 19 and 20 of the mounting substrate 7 via the same anisotropic conductive film 51 .

[0174] According to this structure, the anisotropic conductive film 51 can be conductive in the film thickness direction due to pressure, and the insulation in the film direction (the direction on the plane perpendicular to the film thickness direction) is maintained. Therefore, it is not necessary to form a connecting film independently on the electrodes 19 and 20 of the mounting substrate 7. That is, when the power supply electrodes 40 and 41 of the light source 50 are set on the electrodes 19 and 20 of the mounting substrate 7, the power supply electrodes 40 and 41 can be connected to the electrodes 19 and 20 to make them electrically connected, and the insulation can be maintained.

[0175] In the above-mentioned image forming element 1, it is configured to further include a first light-shielding layer 60 having light reflectivity or light absorption, and the first light-shielding layer 60 is provided between adjacent light sources 50. According to this configuration, the first light-shielding layer 60 can suppress or prevent light leakage toward the adjacent light source 50, thereby preventing the contrast of the image 3 from being reduced.

[0176] <Second embodiment>

[0177] Next, the second embodiment is described. In the second embodiment, each LED display chip 1R, 1G, and 1B converts the emitted light of the blue-violet LED chip 70 by using a wavelength conversion layer, thereby outputting monochromatic light of red (R), green (G), and blue (B). The following describes the configuration that is different from the first embodiment. In addition, the same reference numerals are marked on the same components as the first embodiment, and their description is sometimes omitted.

[0178] The light-emitting elements 11, 12, and 13 of each LED display chip 1R, 1G, and 1B are respectively provided with a blue-violet LED chip 70 and a wavelength conversion layer 62. The blue-violet LED chip 70 is an excitation light source for the red light-emitting element 11, and emits near-ultraviolet light with a wavelength of 400 [nm] to 430 [nm]. The wavelength conversion layer 62 is different in each light-emitting element 11, 12, and 13. That is, the wavelength conversion layer 62 of the red light-emitting element 11 of the red LED display chip 1R converts the wavelength of the near-ultraviolet light emitted from the blue-violet chip LED 70 into red light and outputs it to the outside. The wavelength conversion layer 62 of the green light-emitting element 12 of the green LED display chip 1G converts the wavelength of the near-ultraviolet light emitted from the blue-violet LED chip 70 into green light and outputs it to the outside. The wavelength conversion layer 62 of the blue light-emitting element 13 of the blue LED display chip 1B converts the wavelength of the near-ultraviolet light emitted from the blue-violet LED chip 70 into blue light and outputs it to the outside. Therefore, the structure of each LED display chip 1R, 1G, and 1B is common until the blue-violet LED chip 70 is pasted to the pixel driving circuit 100. In this way, there is no need to separately form an LED display chip 1 having a light-emitting layer 33 that emits three different colors (wavelengths) of light. Therefore, the development period of the LED display chip 1 can be shortened, thereby reducing the inventory of work-in-progress. In addition, in general, the excitation efficiency of the wavelength conversion layer 62 of near-ultraviolet light is high. In addition, people have a low visual sensitivity to near-ultraviolet light. Therefore, there is an advantage that even if there is a slight near-ultraviolet light component that is transmitted through the wavelength conversion layer 62 and emitted to the outside, the effect of reducing the color purity of the pixel 3 is small. In addition, for the wavelength conversion layer 62, various phosphors and quantum dot wavelength conversion layers can be used. Phosphors have the characteristics of relatively low cost and long-term stable performance. The quantum dot wavelength conversion layer has the advantage of a narrow half-value width of the emission spectrum, thereby being able to expand its color gamut. In addition, the wavelength conversion layer 62 does not need to be composed of a monomer material. For example, a blue LED chip may be used as a light source, and white light may be formed by a mixture of yellow phosphor, green phosphor, and red phosphor. Subsequently, each color filter of R, G, and B may be arranged to form each light of red, green, and blue. In this case, the wavelength conversion layer 62 has a double-layer structure of a phosphor layer and a color filter layer.

[0179] Fig.12 It is a cross-sectional view showing a configuration example of a pixel 3 according to the second embodiment. Fig.12 For example, along Figure 2 The cross-sectional structure of the pixel 3 of the single point chain line AA is shown in FIG. In addition, the pixel 3 of the red LED display chip 1R is mainly cited as an example for explanation below, but the pixel 3 of the LED display chip 1G for green display and the LED display chip 1B for blue display are also the same, so their explanation is omitted.

[0180] like Fig.12 As shown, by providing a dam layer 61 between adjacent blue-violet LED chips 70, the leakage of light passing through the wavelength conversion layer 62 can be suppressed to a minimum. The dam layer 61 is formed using a material with high reflectivity and low light absorption, preferably formed using the same material as the light-shielding reflective layer 60. The size of the pixel 3 is as small as several [μm] to several tens of [μm]. It is technically difficult to provide a wavelength conversion layer 62 in each pixel 3, and the manufacturing cost is also high. Therefore, the wavelength conversion layer 62 is applied to the front of the pixel array 2 at the same time, thereby simplifying the process and reducing the manufacturing cost.

[0181] The structure and manufacturing method of the blue-violet LED chip 70 are almost the same as those of the blue LED chip 50 (see, for example, FIG. 7A to FIG. 7I ). The biggest difference between the two is that the In concentration of the quantum well layer of the light-emitting layer 33 constituting the blue-violet LED chip 14 is lower than that of the quantum well layer of the blue LED chip 50 and the band gap of the well layer is larger than that of the blue LED chip 50. In addition, the thickness of each layer of the multiple quantum well structure is slightly changed, but it does not have much impact on the structure of this embodiment. In addition, regarding LSI7, it is basically the same structure as the first embodiment. However, the driving current 54 of the blue-violet LED chip 70 changes due to the difference in the conversion efficiency of the wavelength conversion layer 62. In addition, there is a situation where the temperature dependence of the light conversion efficiency of the blue-violet LED chip 70 and the wavelength conversion layer 62 as a whole is sometimes different according to the light-emitting elements 11, 12, and 13 of each color. In this case, LSI7 controls the driving current 54 of the blue-violet LED chip 70 in accordance with the temperature change.

[0182] Next, a method of providing the light emitting array 8 composed of the blue-violet LED chips 70 arranged two-dimensionally on the LSI 7 will be described. The process of attaching the blue-violet LED chips 70 to the image driving circuit 100 can be implemented in the same manner as in the first embodiment (see FIG. 9A to FIG. 9I ). Fig.9I After the process, a fluorescent resin layer (i.e., a precursor of the wavelength conversion layer 62) mixed with fluorescent particles is applied to the entire surface of the pixel array 2 and baked (fired), so that Fig.12 As shown, a wavelength conversion layer 62 is provided on the blue-violet LED chip 70. At this time, it is preferred that the fluorescent resin layer is removed outside the pixel array 2. In addition, the fluorescent resin layer needs to be removed at least at the pad electrode (not shown) connecting the LSI 7 and the external substrate (not shown). It is also possible to cover the area where the fluorescent resin layer is to be removed (for example, the peripheral part of the pixel array 2) with a resist pattern in advance and then apply the fluorescent resin layer, and remove the resist pattern after dissolving the thin fluorescent resin layer remaining on the resist pattern.

[0183] Compared with the case where a red LED having a compound semiconductor layer 31 of a quaternary system (e.g., AlInGaP) is mounted on a red LED display chip 1R, the red LED display chip 1R formed by the above method has the characteristics of less brightness reduction due to temperature rise and excellent long-term reliability. The reason is that: compared with the compound semiconductor of the quaternary system (AlInGaP), the nitride semiconductor system materials used for green LEDs and blue LEDs have less brightness reduction due to temperature rise and higher mechanical strength. Therefore, even if used for a long time, the color balance is difficult to collapse, so that a red LED display chip 1R with fewer defects can be realized. In addition, the operating voltage of the red LED of the AlInGaP system is 2.5V, which is lower than the operating voltage of the InGaN system (about 3V). Therefore, it is necessary to design LSI7 separately, or to design LSI7 with a wider operating range in order to make LSI7 common, and there is a problem that the development period of LSI7 becomes longer. On the other hand, in the LED display chips 1R, 1G, and 1B of this embodiment, the driving voltage can be made the same, so there is also an advantage that the development period can be shortened.

[0184] The red phosphor mixed in the wavelength conversion layer 62 includes various materials such as YOX (Y2O3:Eu), CaAlSiN3 and other nitride phosphors, and KSF and other fluoride phosphors. Among these, KSF phosphors have a small amount of infrared light emission and a sharp light emission peak near 600 to 650 [nm], such as K2 (Si 0.99 Mn 0.01 )F6 (manganese-activated tetravalent metal fluoride phosphor) is more advantageous in expanding the color gamut. In addition, quantum dot materials can also be used for the wavelength conversion layer 62. In this case, there is an advantage that the half-value width of the emission spectrum can be narrowed and the color gamut can be expanded.

[0185] <Modification of Second Embodiment>

[0186] In addition, as an excitation light source instead of the blue-violet LED chip 70, a blue LED chip 50 that emits blue light with a wavelength of 430 [nm] to 470 [nm] can also be used. In this case, the wavelength conversion layer 62 is not required in the blue LED display chip 1B. Therefore, in the manufacturing process of the blue LED display chip 1B, the process of forming the wavelength conversion layer 62 can be reduced, which is effective in reducing manufacturing costs. However, in the red LED display chip 1R and the green LED display chip 1G, there is a concern that the color purity of the pixel will be reduced due to the leakage of blue light. The following mainly takes the pixel 3 of the LED display chip 1G for green display as an example for explanation. The pixel 3 of the red LED display chip 1R is also the same, so its description is omitted.

[0187] The green LED display chip 1G is composed of a blue LED chip 50 having good luminous efficiency and a wavelength conversion layer 62 that converts the wavelength of blue light emitted from the blue LED chip 50 into green light. The reason is that the green LED can be formed using a nitride compound semiconductor like the blue LED 50, but the luminous efficiency of the green LED is generally lower than that of the blue LED 50. Therefore, the chip size of the green LED needs to be larger, and thus there is a tendency for the price to be high.

[0188] For the wavelength conversion layer 62, various materials such as oxides (Zn2SiO4:Mn), sulfides (ZnS:CuAl, Gd2O2S:Tb), and oxynitride phosphors can be used. β-SiALON (Eu 0.05 Si 11.5 Al 0.5 O 0.05 N 19.95 ) is more advantageous. In addition, in the case where quantum dot materials can also be used, there is an advantage in that the half-value width of the emission spectrum can be narrowed and the color gamut can be expanded. The structure and manufacturing method of the blue LED chip 50 are almost the same as those in the first embodiment. Regarding LSI7, it is the same as the second embodiment. As for the method of setting the light-emitting array 8 composed of two-dimensionally arranged blue LEDs 50 on LSI7, it is the same except that the blue LED chip 50 is used instead of the blue-violet LED chip 70, and the material of the wavelength conversion layer 62 (for example, β-SiALON phosphor) is different.

[0189] Green phosphors such as β-type SiALON have a wide emission spectrum, so the color gamut of the green LED display chip 1G tends to be narrower than that of the green LED. However, in the green LED display chip 1G using the green phosphor, although the NTSC ratio is reduced by about 10%, the manufacturing cost can be reduced by 5%, and the power consumption can be reduced by 19% compared to the case of using the green LED.

[0190] As described above, the image forming element 1 of the present embodiment is configured such that the light emitting element 10 further includes the wavelength conversion layer 62 that converts the wavelength of the light emitted by the light sources 70 and 50 and emits the light to the outside.

[0191] According to this configuration, light emitted from the same light source 50 can be converted into light of different colors by the wavelength conversion layer 62. That is, the same light source 50 as the light emitting element 10 can be used. In the above-mentioned image forming element 1, it is configured to further include a second light shielding layer 61 having light reflectivity or light absorption, and the second light shielding layer 61 is provided at least partially between adjacent wavelength conversion layers 62.

[0192] According to this configuration, the second light shielding layer 61 can suppress or prevent leakage of light between adjacent light emitting elements 10 (particularly, the wavelength conversion layer 62 ), thereby preventing a decrease in contrast of the image 3 .

[0193] <Third embodiment>

[0194] Next, the third embodiment will be described. In the third embodiment, one LED display chip 1 projects a color image. The following describes the configurations that are different from the first embodiment. The same reference numerals are used for the same configurations as the first embodiment, and the description thereof may be omitted.

[0195] Fig.13 is a perspective top view of a pixel 3 according to the third embodiment. Fig.13 As shown, each pixel 3 is provided with a red light emitting element 11, a green light emitting element 12, and a blue light emitting element 13. The light emitting elements 11 to 13 are composed of, for example, a blue-violet LED chip 70 (i.e., an excitation light source) and a wavelength conversion layer 62, and are provided on a pixel driving circuit 100 that supplies a driving current 54 to them.

[0196] exist Fig.13 In the LED display chip 1, when the light emitting elements 11 to 13 are of the same size, the size of each light emitting element 11 to 13 is the same as that of the light emitting element 10 of the LED display chip 1 for single color (for example, see Figure 2 ) is about 1 / 3 of that of the conventional LED display chip 1. Therefore, the manufacturing process of the LED chip and the bonding process to the LSI 7 become difficult. In particular, since the wavelength conversion layers 62 for red and green must be arranged on each LED chip with high precision, the pass rate is sometimes reduced. However, since a full-color image can be displayed by a single LED display chip 1, there is a great advantage that the optical system can be constructed very simply.

[0197] As a method of improving the above-mentioned difficulty in manufacturing, the structure of the LED display chip 1 can be changed. Figures 14A to 14C A configuration example of the pixel 3 according to this embodiment is shown. Fig.14A It is a perspective plan view showing a configuration example of a pixel 3 including independent light emitting elements 11 to 13 . Fig. 14B It is a perspective plan view showing a configuration example of a pixel 3 having an integrated light emitting element 10 . Fig. 14C It is a perspective plan view showing a configuration example in which a plurality of pixels 3 are integrated.

[0198] exist Fig.14AIn the figure, the three light-emitting elements 11 to 13 of red light, green light and blue light are composed of three independent blue-violet LED chips 70 as excitation light sources, and wavelength conversion layers of red light, green light and blue light. The size of each pixel 3 is, for example, 20 [μm] × 20 [μm], and the number of effective pixels is, for example, 480 × 640 (VGA specification). The size of the effective part of the pixel array 2 is, for example, 9.6 [mm] × 12.8 [mm]. In addition, the chip size of the entire LED display chip 1 is also matched with the row selection circuit 4, the column signal output circuit 5, and the image processing circuit 6, for example, 15 [mm] × 18 [mm]. The size of each blue-violet LED chip 70 constituting each light-emitting element 11 to 13 is 18 [μm] × 4.67 [μm], and is arranged with a width of 2 [μm] apart. In this case, the total area occupancy rate of the blue-violet LED chip 70 relative to the area of ​​the pixel 3 is 63%.

[0199] On the other hand, Fig. 14B In the figure, the transparent electrode film 35 and the P-side electrode 40 for each light-emitting element 11 to 13 are of course independently provided, but the compound semiconductor layer 31 is integrally formed. The size of each pixel 3 is, for example, 20 [μm] × 20 [μm], and the number of effective pixels is, for example, 480 × 640 (VGA specification). The size of the effective part of the pixel array 2 is, for example, 9.6 [mm] × 12.8 [mm]. In addition, the chip size of the entire LED display chip 1 is also matched with the row selection circuit 4, the column signal output circuit 5 and the image processing circuit 6 and is, for example, 15 [mm] × 18 [mm]. The size of the blue-violet LED chip 70 for the integrated light-emitting elements 11 to 13 is, for example, 18 [μm] × 18 [μm]. In this case, the area occupancy rate of the blue-violet LED chip 70 relative to the area of ​​the pixel 3 is 81%.

[0200] exist Fig. 14B In the embodiment, the compound semiconductor layer 31 and the N-side electrode 41 of the light-emitting elements 11 to 13 are formed integrally. By adopting such a structure, the size of the compound semiconductor layer 31 can be large, so that the handling of the blue-violet LED chip 70 can be easy. In the integrated light-emitting element 10, it is easy to make its size and the width of the separation groove 42 large, so it has the advantages of being easy to manufacture and reducing costs. On the other hand, light leaks to other blue-violet LEDs adjacent to each other through the compound semiconductor layer 31, so the color purity is slightly reduced. However, the adjacent pixels 3 are separated by the light-shielding reflection layer 60, so there is no degradation in contrast. In addition, in the integrated blue-violet LED chip 70, the compound semiconductor layer 31 does not need to be completely integrated. It is also possible to separate a part of the P-side epitaxial layer 34, the light-emitting layer 33, and the N-side epitaxial layer 32 between each light-emitting element. In this way, the leakage of light can be reduced and the reduction in color purity can be suppressed.

[0201] In addition, Fig. 14B In such an integrated light emitting element 10, when at least one of the LEDs of each color is abnormal, it is necessary to replace the entire LED chip during repair. However, the number of defective LEDs is not large, so the cost increase caused by the repair is not a problem. On the contrary, the effect of easier repair is much greater.

[0202] <Independent LED display chip 1>

[0203] Next, the light emitting elements 11 to 13 (see FIG. Fig.14A ) is described with reference to an example of the structure of an LED display chip 1. Fig.15 1 is a cross-sectional view showing a configuration example of a pixel 3 in an independent type LED display chip 1. Fig.15 Shown along Fig.13 An example of a cross-sectional structure of a pixel 3 along a single-dot chain line DD is shown in FIG. 1 . In the LED display chip 1 , light emitting elements 11 to 13 that emit red light, green light, and blue light, respectively, are provided on a pixel driving circuit 100 .

[0204] Fig.16 1 is an equivalent circuit diagram showing an example of a pixel driving circuit 100 for independent light emitting elements 11 to 13. Fig.16 As shown in FIG. 1 , the pixel driving circuit 100 includes a driving circuit 100R for supplying a driving current 54 to the red light emitting element 11, a driving circuit 100G for supplying a driving current 54 to the green light emitting element 12, and a driving circuit 100B for supplying a driving current 54 to the blue light emitting element 13. When manufacturing the LSI 7, these are formed monolithically on the silicon wafer W1. The number of driving circuits included in the pixel driving circuit 100 increases in accordance with the number of light emitting elements 10.

[0205] The configuration of each drive circuit 100R, 100G, 100B is Figure 4 That is, the driving circuit 100R for the red light emitting element 11 includes a selection transistor 105R, a holding capacitor 108R, a driving transistor 111R, and a test transistor 117R. The driving circuit 100G for the green light emitting element 12 includes a selection transistor 105G, a holding capacitor 108G, a driving transistor 111G, and a test transistor 117G. The driving circuit 100B for the blue light emitting element 13 includes a selection transistor 105B, a holding capacitor 108B, a driving transistor 111B, and a test transistor 117B.

[0206] In the driving circuit 100R, the selection transistor 105R is, for example, an N-type MOS transistor, and its gate terminal is connected to the row selection line (RoI) 101. In addition, the source terminal of the selection transistor 105R is connected to the column signal line (CS) 102R for the red light emitting element 11, and the drain terminal is connected to one end of the holding capacitor 108R and the gate terminal of the driving transistor 111R. The other end of the holding capacitor 108R is connected to the source terminal of the driving transistor 111R and the power supply line (Vcc) 114. The driving transistor 111R is, for example, a P-type MOS transistor, and its drain terminal is connected to the P-side individual electrode 20R for the red light emitting element 11. The anode terminal of the red light emitting element 11 and the source terminal of the test transistor 117R are connected in parallel to the P-side individual electrode 20R. The gate terminal of the test transistor 117R is connected to the test signal line (TE) 116. The cathode terminal of the red light emitting element 11 and the drain terminal of the test transistor 117R are both connected to the ground line (GND) 115. The other drive circuits 100G and 100B are also configured similarly, and thus their description is omitted.

[0207] Next, a method for manufacturing the LED display chip 1 having the independent light emitting elements 11 to 13 is described. This manufacturing process can be implemented in the same manner as the first embodiment except that the pixel 3 is enlarged and the blue-violet LED chip 70 is divided into three (see FIG. 9A to FIG. 9I ). Moreover, in Fig.9I After the process, a process of setting wavelength conversion layers 62 (62R, 62G, 62B) for each color is implemented. However, in the first embodiment and its first to third variants and the second embodiment and its variants, the resist pattern 58 forming the pattern of the light-shielding reflective layer 60 is completely removed. On the other hand, in the present embodiment, only the resist pattern in the area of ​​the pixel 3 is removed, and the rest of the area is left (not shown). The reason is that: there is a step difference between the area of ​​the pixel 3 and other places due to the height difference with the blue-violet LED 70, so it is impossible to uniformly apply the wavelength conversion layer 62.

[0208] FIG. 17A to FIG. 17D This is a diagram for explaining an example of a process of providing the wavelength conversion layer 62R for each color in the LED display chip 1 using the independent type light emitting elements 11 to 13 . Fig.17A as well as Fig. 17C It is a figure which shows the process of coating and pattern exposure of the wavelength conversion layer 62R. Fig. 17B as well as Fig.17D : is a diagram showing the process of developing and baking the wavelength conversion layer 62R. Fig.17A as well as Fig. 17B Shown along Fig.14AThe cross section of the single-point chain line E1-E1. Fig. 17C as well as Fig.17D Shown along Fig.14A The cross section is a double-dot chain line E2-E2. In addition, the process of providing the wavelength conversion layer 62R for red is cited as an example for description below.

[0209] First, if Fig.17A As shown in FIG. 1 , a composite resin layer (negative resist layer) in which red light-emitting phosphor is dispersed is applied to the surface of the pixel 3 (on the blue-violet LED 70 and the dam layer 61), and the portion on the blue-violet LED 70 that becomes the red light-emitting element 11 is exposed. By this exposure, the composite resin in the above portion becomes polymerized and insoluble. Next, as shown in FIG. Fig. 17B As shown in FIG. 1 , the unexposed portion of the composite resin layer (the portion other than the portion on the blue-violet LED 70) is dissolved using a developer. This process allows the red wavelength conversion layer 62R to be left only in the portion where the red light emitting element 11 is to be formed. The same process is also performed on the green and blue wavelength conversion layers 62G and 62B. Fig.17A as well as Fig. 17B The light emitting elements 11 to 13 of three colors (R, G, and B) can be formed by the same steps.

[0210] As a result of manufacturing the LED display chip 1 as described above, the average number of defective pixels per chip is about 31. By making the width of the separation groove 42 as wide as 2 [μm], the repairability of the defective position is improved. On the other hand, each blue-violet LED 70 is slender in shape, so the operation during repair is difficult, and the complete repair rate is reduced to about 30%. However, the result of actually operating the LED display chip 1 is that the maximum brightness becomes 2000 [lm]. In addition, the contrast is above the measurement limit, and the maximum power consumption is also 50 [W]. The NTSC ratio is 103%, and the color gamut is also a good result.

[0211] <Integrated LED display chip 1>

[0212] Next, the light emitting elements 11 to 13 (see Fig. 14B ) is described by taking an example of the structure of an LED display chip 1 having a red light, a green light, and a blue light. In this structure, LED chips that excite and emit light with red light, green light, and blue light are integrated. Therefore, the size of the integrated LED chip is about three times the size of the independent LED chip. In addition, the operation during repair becomes easier, thereby having the effect of improving the pass rate. However, the compound semiconductor layer is not separated but continuous, so the excited light leaks not only to the wavelength conversion layer 62 for the target color (for example, red), but also to the wavelength conversion layer 62 for other colors (for example, green and blue). Therefore, the color purity of the pixel 3 is slightly deteriorated.

[0213] Next, a method for manufacturing an LED display chip 1 having integrated light-emitting elements 11 to 13 is described. In addition, in the LED display chip 1, the blue-violet LED chip 70 that excites the three-color wavelength conversion layers 62R, 62G, and 62B is not monolithic for each light-emitting element 11 to 13. In addition, a dam layer 61 is also provided on the blue-violet LED chip 70 to separate the wavelength conversion layers 62R, 62G, and 62B. The manufacturing process of the integrated LED display chip 1 can be implemented in the same manner as the first embodiment except for the above (see FIG. 9A to FIG. 9I ). Moreover, in Fig.9I After the step of forming the wavelength conversion layer 62 for each color, a step of providing the wavelength conversion layer 62 for each color is implemented.

[0214] FIG. 18A to FIG. 18D This is a diagram for explaining an example of a process of providing wavelength conversion layers 62R to 62B for respective colors in the LED display chip 1 using the integrated light emitting elements 11 to 13 . Fig.18A This is a diagram showing the steps of coating and pattern exposure of the red wavelength conversion layer 62R. Fig.18B This is a diagram showing the process of developing and baking the red wavelength conversion layer 62R. Fig. 18C This is a diagram showing the process of developing and baking the green wavelength conversion layer 62G. Fig.18D This is a diagram showing the process of developing and baking the wavelength conversion layer 62B for blue. FIG. 18A to FIG. 18D Shown along Fig. 14B Cross-section of the single-point chain line FF.

[0215] First, if Fig.18A As shown, a composite resin layer (negative resist layer) in which red light-emitting phosphor is dispersed is applied to the surface of the pixel 3 (the back of the blue-violet LED 70 and the dam layer 61), so that the portion corresponding to the light-emitting area of ​​the red light-emitting element 11 is exposed and not dissolved. Fig.18B As shown, the unexposed portion of the composite resin layer (except the portion corresponding to the light emitting region of the red light emitting element 11) is dissolved using a developer. Through this process, the red wavelength conversion layer 62R is provided in the portion where the red light emitting element 11 is to be formed.

[0216] Next, in order to form the green light emitting element 12, Fig.18A Similarly, a composite resin layer (negative resist layer) in which green light-emitting phosphor is dispersed is applied to the surface of the pixel 3, so that the portion corresponding to the light-emitting region of the green light-emitting element 12 is exposed and insoluble. Fig. 18C As shown, the unexposed portion is dissolved using a developing solution, and a wavelength conversion layer 62G for green is provided in the portion where the green light emitting element 12 is to be formed.

[0217] Next, in order to form the blue light emitting element 13, Fig.18A Similarly, a composite resin layer (negative resist layer) in which a blue light-emitting phosphor is dispersed is applied to the surface of the pixel 3, and the portion corresponding to the light-emitting region of the blue light-emitting element 13 is exposed and insoluble. Fig.18D As shown, a developer is used to dissolve the unexposed portion and a wavelength conversion layer 62B for blue is provided in the portion where the blue light emitting element 13 is formed. By implementing the above steps, the integrated light emitting elements 11 to 13 can be provided in the LED display chip 1. In addition, the order of forming the phosphors of each color is not limited to the above order. Moreover, the configuration within the pixel can also be changed without being limited to the above.

[0218] As a result of manufacturing the LED display chip 1 as described above, the yield rate is approximately doubled and the cost can be significantly reduced compared to the LED display chip 1 using the independent light emitting elements 11 to 13. On the other hand, the NTSC ratio becomes 100%, and the color gamut is deteriorated.

[0219] <LED display chip 1 integrating a plurality of pixels 3>

[0220] Next, a configuration in which a plurality of pixels are integrated (see Fig. 14C Hereinafter, a configuration example of an LED display chip 1 (hereinafter referred to as a plurality of pixels integrated type) is described. In this configuration, a plurality of pixels are integrated in an LED display chip 1 that excites red light, green light, and blue light to emit light. Fig. 14C In the embodiment of the present invention, the four pixels of the light-emitting elements 10s, 10t, 10u, and 10v are integrated. The size of the LED chip with multiple pixels integrated is about 12 times the size of the independent LED chip. In addition, the operation during repair becomes easier, so the effect of improving the pass rate is greater. However, the color purity of the LED display chip 1 may be slightly degraded. In addition, a decrease in contrast may occur due to light leakage between adjacent pixels.

[0221] For a plurality of pixel-integrated LED display devices 1, as Fig. 14CAs shown, the red light emitting elements 11s, 11t, 11u, 11v, the green light emitting elements 12s, 12t, 12u, 12v, and the blue light emitting elements 13s, 13t, 13u, 13v are monolithicized into one LED chip. In addition, the red light emitting element 11s, the green light emitting element 12s, and the blue light emitting element 13s constitute the light emitting element 10s of the pixel 3s. The red light emitting element 11t, the green light emitting element 12t, and the blue light emitting element 13t constitute the light emitting element 10t of the pixel 3t. The red light emitting element 11u, the green light emitting element 12u, and the blue light emitting element 13u constitute the light emitting element 10u of the pixel 3u. The red light emitting element 11v, the green light emitting element 12v, and the blue light emitting element 13v constitute the light emitting element 10v of the pixel 3v. The P-side electrode 40 is independently provided for each of the above-mentioned light emitting elements 11s to 13v. However, one N-side electrode 41 is provided for the entirety of the above-mentioned light emitting elements 11s to 13v. By configuring in this way, the area where the N-side contact hole 39 is formed and the area where the N-side electrode 41 is formed can be reduced. Therefore, the mesa portion 36 (not shown), the transparent conductive film 35, the P-side contact hole 38 and the P-side electrode 40 of each light-emitting element 10s to 10v can be enlarged. By enlarging the pattern of the mesa portion and the transparent conductive film 35, the light-emitting efficiency can be improved. By enlarging the P-side contact hole 38, the manufacture of the light-emitting elements 10s to 10v is facilitated. Moreover, by enlarging the P-side electrode 40, the alignment accuracy when bonding the LSI 7 and the light-emitting elements 10s to 10v can be relaxed, and the bonding is facilitated. In addition, Fig. 14C The example of integrating four pixels is shown in FIG. 1 , but the LED display chip 1 of the multiple pixel integrated type is not limited to this example. The number of pixels integrated in the LED display chip 1 of the multiple pixel integrated type does not need to be limited to four, and can also be increased or decreased. In other words, it can also be a number other than four.

[0222] <Modification of the third embodiment>

[0223] Alternatively, the wavelength conversion layers 62R to 62B may be formed by a method without exposing the composite resin layer to light. Fig.19A as well as Fig.19B This is a diagram for explaining another example of the process of providing the wavelength conversion layer 62 . Fig.19A The diagram shows the steps of forming a positive resist pattern 63 and applying a wavelength conversion layer 62 . Fig.19B The figure shows the process of removing the flat portion of the wavelength conversion layer 62 and the positive resist pattern 63 . Fig.19A as well as Fig.19B For example, along Fig.14A The cross section of the single-point chain line EE. In addition, Fig.19A as well as Fig.19B The steps in the LED display chip 1 using the independent light emitting elements 11 to 13 are exemplified. The steps in the LED display chip 1 using the integrated light emitting elements 11 to 13 are the same, so the description thereof is omitted.

[0224] like Fig.19A As shown, first, a mold of a positive resist pattern 63 is made on the surface of the pixel 3 except for the portion corresponding to the light-emitting area of ​​the red light-emitting element 11, and a composite resin layer in which red light-emitting phosphors are dispersed is applied on the surface of the pixel 3 (including the positive resist pattern 63). Fig.19B As shown in FIG. 1 , the surface layer of the composite resin layer is removed in such a manner that only the composite resin layer corresponding to the light-emitting region of the red light-emitting element 11 is left. That is, the composite resin layer on the positive resist pattern 63 and the positive resist pattern 63 are removed. Through this process, a wavelength conversion layer 62R for red is provided in the portion where the red light-emitting element 11 is to be formed. In this method, the resolution of the positive resist pattern 63 is high, so it is different from the exposure method (see FIG. 1 ). Fig.17A as well as Fig.18A ) can form a pattern with higher precision. Therefore, it is applicable when the size of the pixel 3 is made smaller. As described above, according to the present embodiment, the image forming element 1 is an image forming element 1 having a plurality of pixels 3 and projecting and displaying the emitted light of the pixel 3, and is configured to include: a light emitting element 10, which includes a light source 70 for emitting light; and a mounting substrate 7, on which a plurality of light emitting elements 10 are arranged on the mounting surface, and a plurality of light sources 70 that are monolithic and include at least one pixel 3 are arranged, and the light sources 70 each have at least one power supply electrode 40, 41 on the surface opposite to the mounting substrate 7, and the mounting substrate 7 has: a driving electrode 40, 41; The driving circuit 100R, 100G, 100B of the dynamic light source 70, and the electrodes 19, 20 (20R, 20G, 20B) arranged on the mounting surface and electrically connected to the power electrodes 40, 41 of the light source 70, the driving circuit 100R, 100G, 100B includes: the switching circuit 117R, 117G, 117B that selectively short-circuits the electrodes 19, 20 electrically connected to the power electrodes 40, 41 of the light source 70 with other electrodes or wirings in the driving circuit 100.

[0225] According to this configuration, when the light emitting element 10 including the light source 70 is disposed on the mounting surface of the mounting substrate 7, at least one power supply electrode 40, 41 disposed on the surface opposite to the mounting substrate 7 can be electrically connected to the electrodes 19, 20 disposed on the mounting surface. In addition, when replacing a defective light source 56, for example, the defective light source 56 can be removed and a normal light source 55 can be installed relatively easily and efficiently. In addition, since the plurality of light sources 70 are monolithic with each including at least one pixel 3, it is possible to suppress the leakage of light toward the adjacent pixel 3 through the inside of the light source 70. That is, it is possible to suppress the leakage of light toward the dark pixel adjacent to the bright pixel. Therefore, it is possible to suppress or prevent the reduction in the contrast of the image formed by the projected light of the pixel 3 and the color mixing of the emitted light between the adjacent pixels 3. In addition, if the light source 70 is monolithic with a plurality of pixels 3, the number of light sources 70 to be disposed on the mounting substrate 7 by the light emitting element 10 including the light source 70 can be reduced, and the difficulty of its operation can also be improved. Therefore, the operation efficiency is improved, and mass production is also facilitated. In addition, the driving circuits 100R, 100G, and 100B include the switch circuits 117R, 117G, and 117B. Therefore, before connecting the light source 70 of the light-emitting element 11, 12, and 13 to the driving circuits 100R, 100G, and 100B, the electrodes 19 and 20 can be selectively short-circuited with other electrodes or wirings in the driving circuit 100 by the switch circuits 117R, 117G, and 117B to detect whether the driving circuits 100R, 100G, and 100B are normal or defective. Therefore, an image forming element with excellent color rendering and high contrast can be manufactured with low defects and high yield.

[0226] In the above-described image forming element 1 , a plurality of wavelength conversion layers 62R, 62G, 62B are provided in the light emitting elements 11 , 12 , 13 , and each of the wavelength conversion layers 62R, 62G, 62B converts emitted light into light of different wavelengths.

[0227] According to this configuration, the light emitted from the same light source 70 can be converted into light of different colors by the wavelength conversion layers 62R, 62G, and 62B. That is, the same light source 70 as the light emitting elements 11, 12, and 13 can be used.

[0228] In addition, in the above-described image forming element 1 , the light source 70 is provided for each of the wavelength conversion layers 62R, 62G, and 62B.

[0229] According to this configuration, it is possible to suppress the mixing of colors among the light emitting elements 11 , 12 , and 13 . Alternatively, in the above-described image forming element 1 , the plurality of wavelength conversion layers 62R, 62G, and 62B are provided for each light source 70 .

[0230] According to this configuration, the light source 70 for converting light by the wavelength conversion layers 62R, 62G, and 62B is shared, so that the size of the light source 70 can be relatively large. Therefore, the light source 70 is easy to handle, the work efficiency is improved, and the yield rate is also improved.

[0231] <Fourth embodiment>

[0232] Next, the fourth embodiment is described. In the fourth embodiment, the repair of the light emitting element 10 can be minimized, so two identical light emitting elements 10a and 10b are provided in one pixel 3. The following describes the configurations that are different from the first to third embodiments. In addition, the same reference numerals are given to the same configurations as the first to third embodiments, and their descriptions are sometimes omitted.

[0233] Fig. 20 is a perspective top view of a pixel 3 according to the fourth embodiment. Fig. 20 As shown, a first light-emitting element 10a and a second light-emitting element 10b are mounted in one pixel 3. The transparent conductive film 35 and the P-side electrode 40 are provided for each light-emitting element 10a, 10b, but the mesa portion 36 (i.e., the compound semiconductor layer 31) is integrated, and the N-side electrode 41 is shared. Moreover, the first light-emitting element 10a is usually used, but when the first light-emitting element 10a becomes poor in light emission, the second light-emitting element 10b is used. By using them separately in this way, the repair work caused by the poor light emission of the light-emitting element 10 can be reduced. However, when the N-side electrode 40 becomes poorly conductive, or when both the first light-emitting element 10a and the second light-emitting element 10b become defective, the light-emitting element 10 of the pixel 3 needs to be replaced.

[0234] In order to perform the above-described operation, a pixel driving circuit 100 capable of selecting and driving the first light emitting element 10 a and the second light emitting element 10 b is required. Fig.21 1 is an equivalent circuit diagram showing an example of the pixel driving circuit 100 according to the fourth embodiment. Fig.21 As shown, the pixel driving circuit 100 has: a selection transistor 105, a holding capacitor 108, a driving transistor 111, a test transistor 117, a first element selection transistor 121, a second element selection transistor 122, and a light emitting element selection circuit 140. When manufacturing LSI 7, these are formed in a single piece on a silicon wafer W1. In addition, Fig.21In the description, the pixel driving circuit 100 includes the light emitting element selection circuit 140, but a part of the light emitting element selection circuit 140, such as the non-volatile storage transistor part, may be configured in other parts of the LSI 7. The selection transistor 105 is, for example, an N-type MOS transistor, and its gate terminal is connected to the row selection line (RoI) 101. In addition, the source terminal of the selection transistor 105 is connected to the column signal line (CS) 102, and the drain terminal is connected to one end of the holding capacitor 108 and the gate terminal of the driving transistor 111. The other end of the holding capacitor 108 is connected to the source terminal of the driving transistor 111 and the power supply line (Vcc) 114. The driving transistor 111 is, for example, a P-type MOS transistor. The source terminals of the first element selection transistor 121, the second element selection transistor 122, and the test transistor 117 are connected in parallel to its drain terminal. The drain terminal of the first element selection transistor 121 is connected to the anode terminal of the first light emitting element 10a. The drain terminal of the second element selection transistor 122 is connected to the anode terminal of the second light emitting element 10b. The gate terminals of the first element selection transistor 121 and the second element selection transistor 122 are connected to the light emitting element selection circuit 140 described later. The gate terminal of the test transistor 117 is connected to the test signal line (TE) 116. The cathode terminals of the first light emitting element 10a and the second light emitting element 10b and the drain terminal of the test transistor 117 are all connected to the ground line (GND) 115.

[0235] The light emitting element selection circuit 140 includes a nonvolatile memory transistor 145, a selection transistor 146, a first inverter circuit 147, a second inverter circuit 148, and a latch transistor 149. The source terminal of the nonvolatile memory transistor 145 is connected to the power supply line (Vcc) 114, and the gate terminal is connected to the FG line 150. The drain terminal of the nonvolatile memory transistor 145 is connected to the source terminal of the selection transistor 146, the input terminal of the first inverter circuit 147, and the source terminal of the latch transistor 149. The gate terminal of the selection transistor 146 is connected to the signal line (SE) 151, and the drain terminal is connected to the ground line (GND) 115. The output terminal of the first inverter circuit 147 is connected to the gate terminal of the second element selection transistor 122 and the input terminal of the second inverter circuit 148. The output terminal of the second inverter circuit 148 is connected to the gate terminal of the first element selection transistor 121 and the drain terminal of the latch transistor 149. The gate terminal of the latch transistor 149 is connected to the signal line (SE-) 152. In addition, here, a stacked gate transistor having a floating gate is used as the nonvolatile memory transistor 145, but it is not limited to this example, and other types of transistors having a nonvolatile memory effect such as a charge trap type can also be used. In addition, an element having a nonvolatile memory effect can also be used in combination with a transistor.

[0236] When the light emission test of the first light emitting element 10a and the second light emitting element 10b is performed, the light emission test of the first light emitting element 10a is performed first. When the first light emitting element 10a is light emitting poorly, writing is performed on the non-volatile storage transistor 145 of its pixel 3 to increase the threshold of the non-volatile storage transistor 145. That is, the signal line (SE) 151 is turned on, and writing is enabled by supplying a high voltage to the signal line (FG) 150. When the power supply of the LED display chip 1 is turned on, one of the first light emitting element 10a and the second light emitting element 10b is selected using the non-volatile storage transistor 145. When the signal line (SE) 151 is in the on state, the signal line (FG) 150 is turned on. When no data is written to the nonvolatile memory transistor 145, the driving capability of the nonvolatile memory transistor 145 is higher. Therefore, the input signal to the first inverter circuit 147 becomes High (hereinafter referred to as H), the output signal of the first inverter circuit 147 and the input signal of the second inverter circuit 148 become Low (hereinafter referred to as L), and the output signal of the second inverter circuit 148 becomes H. Thus, the first light-emitting element 10a is selected. Thereafter, the signal line (FG) 150 and the signal line (SE) 151 are returned to the off state. At this time, the potential of the signal line (SE-) 152 becomes H. This potential that has become H is fixed as long as the power is turned on.

[0237] On the other hand, when the threshold voltage of the nonvolatile memory transistor 145 is high, even if the signal line (FG) 150 is turned on, the nonvolatile memory transistor 145 is not turned on, so the input signal of the first inverter circuit 147 becomes L, the output signal of the first inverter circuit 147 and the input signal to the second inverter circuit 148 become H, and the output signal of the second inverter circuit 148 becomes L. As a result, the second light-emitting element 10b is selected.

[0238] By configuring the pixel driving circuit 100 in this way, it is possible to significantly reduce light emission failure of the light emitting element 10. Although the circuit scale of the pixel driving circuit 100 increases, or a nonvolatile memory transistor 145 needs to be fabricated, it can be formed without any problem using the latest miniaturization process.

[0239] Next, two identical light emitting elements 10a and 10b (see Fig. 20 ) is described as an example of manufacturing an LED display chip 1. An LED display chip 1 having the same function as the first embodiment is manufactured. As for the size of the pixel 3, the micro-processing level is improved, for example, a size of 10 [μm] × 10 [μm] is manufactured. Fig.21The pixel driving circuit 100 shown in the figure. However, in order to form the nonvolatile memory transistor 145, the formation process is slightly longer. In addition, in order to configure the increased signal line, the number of wiring layers is increased by one layer. In addition, because a circuit (not shown) for controlling the selection circuit 140 including the nonvolatile memory transistor 145 is added, the area of ​​the LED chip is increased by about 5%. In accordance with the increase in the number of processes, the manufacturing cost is also increased by about 12%.

[0240] The process of placing the light emitting element 10 on the LSI 7 is the same as that in the first embodiment (see Figures 9A to 9I ) is the same. In the process of testing poor luminescence (refer to Fig. 9B ) was reduced by about 30%. This can be considered to be the effect of reducing the size of the light emitting element 10. Moreover, it was found that 80% of the defective light emitting elements 10 were normalized by switching from the first light emitting element 10a to the second light emitting element 10b. Therefore, the defective light emitting elements 10 that had to be replaced were reduced to 14% compared with the case of the first embodiment. Therefore, for products with a large production volume, although there is an increase in the cost of LSI 7, the benefits generated by the increase in productivity based on the reduction in defective repairs are greater, and the effect of the present invention is large. However, for models with a small production volume, on the contrary, the benefits are greater when there is no light emitting element switching function.

[0241] <Modification of the Fourth Embodiment>

[0242] Fig. 22 2 is an equivalent circuit diagram showing another example of the pixel driving circuit 100 according to the fourth embodiment. Fig. 22 The pixel driving circuit 100 shown in FIG. Fig.21 Similarly, it has a selection transistor 105, a holding capacitor 108, and a driving transistor 111. On the other hand, the first element selection transistor 121 is replaced by a first nonvolatile storage transistor 155, and the second element selection transistor 122 is replaced by a second nonvolatile storage transistor 156. In addition, a test transistor 117a is arranged in parallel with the LED 10a, and a test transistor 117b is arranged in parallel with the LED 10b. Fig. 22 The composition and Fig.21 Compared with the structure of , the number of nonvolatile storage transistors and test transistors increases to two each, but the light emitting element selection circuit 140 is deleted to simplify the circuit. In addition, the pixel driving circuit 100 is provided with a first control gate 153 and a second control gate 154. The first control gate 153 controls the gate terminal of the first nonvolatile storage transistor 155. The second control gate 154 controls the gate terminal of the second nonvolatile storage transistor 156. When manufacturing LSI 7, they are formed monolithically on the silicon wafer W1.

[0243] By providing the test transistor 117a and the test transistor 117b, the entire circuit of the pixel portion, including the characteristics of the first nonvolatile storage transistor 155 and the second nonvolatile storage transistor 156, can be tested during the manufacturing stage of the LSI 7. For example, the characteristics of the first nonvolatile storage transistor 155 can be tested as follows. Both the test transistors 117a and 117b are turned on. The second nonvolatile storage transistor 156 is turned off. By raising the row selection line 101 to a high level and lowering the potential of the column signal line 102 to a GND level, the drive transistor 111 is turned on, and a voltage is applied from the power supply Vcc to the drain side of the first nonvolatile storage transistor 155 (the terminal connected to the drain of the drive transistor 111). Furthermore, if the first control gate 153 is turned on, the current flowing in the first nonvolatile storage transistor 155 can be evaluated. In addition, if the voltage applied from the power supply Vcc and the voltage applied to the first control gate 153 are appropriately selected, writing can also be performed. For example, the voltage applied from the power supply Vcc is set to about 3V to 6V, and the control gate voltage is set to about 4V to 12V. If the current evaluation is performed again after writing, the result of the writing can be confirmed. In addition, the evaluation of the second non-volatile storage transistor 156 can also be implemented in the same way. Although it is desired to perform a write test, the write result must be eliminated by ultraviolet irradiation at the end of the test, and equipment must be set up for this purpose, and the test time is also prolonged, so the write test can also be omitted.

[0244] At the stage when the LED display chip 1 is completed, when the light emission test of the first light emitting element 10a and the second light emitting element 10b is performed, the light emission test of the first light emitting element 10a is performed first. In the state before the light emission test, the threshold voltage of the first nonvolatile storage transistor 155 and the second nonvolatile storage transistor 156 are both low, and they are in a state that can be turned on by the control gate voltage Vn (for example, 3V to 12V) during operation. The first nonvolatile storage transistor 155 is turned on, and the second nonvolatile storage transistor 156 is turned off to evaluate the light emission characteristics of each pixel 3 in turn. At the stage when the evaluation of all pixels is completed, for normal pixels 3, the second nonvolatile storage transistor 156 is written, and it is turned off for the control gate voltage Vn. When writing to the second nonvolatile storage transistor 156, similar to the test in the manufacturing stage of LSI 7, the test transistor 117a is turned on, and the first nonvolatile storage transistor 155 is turned off to perform writing.

[0245] In the light-emitting test of the first light-emitting element 10a, for the pixel judged to be defective, the first non-volatile storage transistor 155 is written, and the control gate voltage Vn becomes a non-connected state. Moreover, in the light-emitting test of the first light-emitting element 10a, the light-emitting test of the second light-emitting element 10b is performed only for the pixel judged to be defective. As a result, if there is no problem, a good chip is obtained. If it is a normal state, the number of pixels that become defective in the light-emitting test of the first light-emitting element 10a is a very small number of all pixels, and the possibility of problems in the test of the second light-emitting element 10b is very small. In the event that the second light-emitting element 10b becomes defective, for example, by writing to the non-volatile storage transistor 156b, by not having current flowing in the second light-emitting element 10b, the leakage current is cut off, and it becomes a completely black pixel (non-luminous state), so it can be used in the application that allows black pixels. Therefore, the qualified rate can be further improved.

[0246] As described above, according to the present embodiment, the image forming element 1 is configured such that a plurality of identical light emitting elements 10 a and 10 b are provided for each pixel 3 .

[0247] According to this configuration, even if one of the light emitting elements 10a becomes defective, the other light emitting element 10b can be used without replacement as long as it is normal. Therefore, the defect occurrence rate is reduced, and thus production efficiency can be improved.

[0248] In the above-described image forming element 1 , the drive circuit 100 is configured to include at least one nonvolatile memory transistor 145 for selecting any one of the plurality of identical light emitting elements 10 a and 10 b .

[0249] According to this configuration, any one of the same light-emitting elements 10 a and 10 b can be selected by at least one nonvolatile memory transistor 145 , so that light emission failure of the light-emitting element 10 can be significantly reduced.

[0250] <Fifth Embodiment>

[0251] Next, the fifth embodiment is described. In the fifth embodiment, the configuration of the pixel driving circuit 100 for reducing the inconsistency of the light emitting intensity of the light emitting element 10 between different pixels 3 is described. The light emitting element 10 is the same as in the other embodiments. In the pixel driving circuit 100 of this embodiment, a nonvolatile storage transistor 161 is provided to finely adjust the amount of current flowing in the light emitting element 10.

[0252] When the inconsistency of the luminous intensity of the light-emitting element 10 constituting the pixel 3 is not within a certain range, abnormally bright points and / or darker points are generated in the image. Or, problems such as spots occur in a uniform display area. As a result, the display quality of the image deteriorates. Therefore, during the lighting test of the pixel 3, the pixel 3F with a large inconsistency in luminous intensity is considered defective and must be replaced with a normal product. In the case of a large inconsistency in the characteristics of the light-emitting element 10, the production cost increases due to the increase in repair time. In addition, in the case of an inconsistency in luminous intensity caused by the wavelength conversion layer 62, such replacement is more difficult. Therefore, the LED display chip 1 itself has to become defective.

[0253] Therefore, in this embodiment, after being temporarily completed as a display element, by adding a function to adjust the luminous intensity of each pixel 3, the permissible range of inconsistency of the luminous intensity of the light-emitting element 10 can be expanded. As a result, the number of pixels that should be repaired can be reduced. In addition, when the wavelength conversion layer 62 is used, the defect caused by the inconsistency of the wavelength conversion layer 62 is suppressed and the manufacturing cost of the display element can be reduced. Regarding such a configuration, the configuration different from the first to fourth embodiments is described. In addition, the same figure mark is marked on the same components as the first to fourth embodiments, and its description is sometimes omitted.

[0254] Fig.23 1 is an equivalent circuit diagram showing an example of the pixel driving circuit 100 according to the fifth embodiment. Fig.23 As shown, the pixel driving circuit 100 has: a selection transistor 105, a holding capacitor 108, a driving transistor 111N, a test transistor 117, and a non-volatile memory transistor 161. When manufacturing LSI 7, they are formed as a single piece on the silicon wafer W1. The difference from the first embodiment is that the driving transistor 111N is composed of an NMOS transistor, the non-volatile memory transistor 161 is provided between the driving transistor 111N and the light-emitting element 10, and a signal line 160 for the control gate (CG) of the non-volatile memory transistor 161 is provided. Here, as the non-volatile memory transistor 161, a stacked gate transistor with a floating gate is used, but it is not limited to this example, and other types of transistors with non-volatile memory effect such as charge trapping type can also be used. In addition, it is also possible to use an element with non-volatile memory effect in combination with a transistor. In addition, the number of non-volatile memory transistors 161 possessed by the pixel driving circuit 100 is not limited to Fig.23 In other words, the pixel driving circuit 100 may be configured to include at least one nonvolatile storage transistor 161. In addition, the circuit method for adjusting the current amount by the nonvolatile storage transistor 161 is not limited to Fig.23 , in the Fig.23 In a different circuit configuration, the nonvolatile memory transistor 161 does not necessarily need to be provided in the pixel driving circuit 100 , and may be provided in other parts of the LSI 7 .

[0255] Next, a method for adjusting the luminous intensity of the light-emitting element 10 using the non-volatile memory transistor 161 is described. First, at the stage where the LED display chip 1 is completed, the luminous intensity of each pixel is measured, and the pixel 3F (sometimes multiple) whose luminous intensity exceeds the upper limit of the specification (i.e., the allowable range of inconsistency of the luminous intensity) is determined. Moreover, the luminous intensity of the pixel 3F that exceeds the upper limit of the specification is reduced and brought within the specification, thereby making the pixel 3F a good product. The reduction in luminous intensity is carried out by reducing the current flowing in the driving transistor 111N. That is, by increasing the threshold of the non-volatile memory transistor 161, the conductance between the source / drain of the non-volatile memory transistor 161 is reduced, and the potential difference between the source / drain (the potential difference between the terminals A-SD) is increased. Thus, by increasing the source potential of the driving transistor 111N (the potential of the terminal SD), the current flowing in the driving transistor 111N is reduced. The signal potential is written to the gate electrode of the driving transistor 111N with the power supply Vcc114 as a reference. The signal potential is held by the holding capacitor 108. The output current of the driving transistor 111N is mainly determined by the source-gate potential difference (terminal GD-SD potential difference). Therefore, if the source potential (terminal SD potential) increases, the output current decreases.

[0256] The threshold value of the nonvolatile memory transistor 161 is adjusted as follows. First, a voltage is applied to the row selection line 101 and the column signal line 102 to turn on the drive transistor 111N via the selection transistor 105, and the test transistor 117 is turned on. In this way, a current is caused to flow in the nonvolatile memory transistor 161. In this state, a pulse voltage is applied to the control gate terminal 160 of the nonvolatile memory transistor 161. Thus, electrons are injected into the floating gate, and the threshold value can be increased. In order to perform this writing, the voltage applied to the control gate terminal 160 and the voltage of the power supply Vcc114 are appropriately adjusted. In the case of a stacked gate transistor, the source / drain voltage is generally 3V or more, and the source / control gate voltage is 4V or more. However, these depend on the size, structure, etc. of the stacked gate transistor. When the light-emitting element 10 is lit, the nonvolatile memory transistor 161 is operated in a linear operation region where a potential much larger than the threshold voltage is applied to the control gate voltage. In this way, the nonvolatile memory transistor 161 operates as a resistor, and a potential difference substantially proportional to the amount of current flowing in the light emitting element 10 is generated between the source and the drain. As the threshold voltage increases, the potential difference between the source and the drain increases, thereby increasing the source voltage of the driving transistor 111N. Therefore, the driving current can be reduced.

[0257] The threshold voltage of the stacked gate transistor can be controlled continuously with high precision by applying voltage and the number of applied pulses. Therefore, the driving current of the light-emitting element 10 can be finely adjusted. As a result, the inconsistency of the luminous intensity between the light-emitting elements can be reduced, so that display elements with high display quality can be produced with a high yield.

[0258] <First Modification of Fifth Embodiment>

[0259] Fig.24 This is an equivalent circuit diagram showing an example of a pixel driving circuit 100 in which the configuration of the fourth embodiment is combined with the fifth embodiment. Fig.24 The pixel driving circuit 100 shown in FIG. Fig.23 Similarly, the nonvolatile memory transistor 161, the light emitting element 10, and the test transistor 117 are provided. Fig.23 is a system, but in Fig.24 Zhongyu Fig. 22 Similarly, two systems are provided, that is, a system of the first nonvolatile memory transistor 155, the first light emitting element 10a, and the test transistor 117a, and a system of the second nonvolatile memory transistor 156, the second light emitting element 10b, and the test transistor 117b are connected in parallel.

[0260] During the manufacturing stage of LSI7, Fig. 22 Similarly, the pixel driving circuit 100 is tested by testing the characteristics of the first nonvolatile storage transistor 155 and the second nonvolatile storage transistor 156. The difference is that the driving transistor 111N is replaced by NMOS from PMOS, so the signal applied to the column signal line 102 is inverted. When the LED display chip 1 is completed, the light emission test of the first light emitting element 10a and the second light emitting element 10b is performed to make each pixel 3 capable of emitting light. Fig. 22 As described. That is, when the first light-emitting element 10a is a good product, the threshold value of the second non-volatile storage transistor 156 is increased so that the first light-emitting element 10b cannot be connected. On the other hand, when the first light-emitting element 10a is a defective product, the threshold value of the first non-volatile storage transistor 155 is increased so that the first light-emitting element 10a cannot be connected, so that the second light-emitting element 10b can emit light. Thereafter, for the pixel 3F whose light emission exceeds the specification value (for example, the upper limit value of the specification), the threshold value of the first non-volatile storage transistor 155 or the second non-volatile storage transistor 156 is fine-tuned to adjust the light emission of the first light-emitting element 10a or the second light-emitting element 10b. This is as Fig.23 The selection of the first light emitting element 10a and the second light emitting element 10b and the adjustment of the light emission amount may be performed simultaneously.

[0261] <Second Modification of Fifth Embodiment>

[0262] Fig.25 FIG. 1 is an equivalent circuit diagram showing another example of the pixel driving circuit 100 according to the fifth embodiment. Fig.23 In the configuration, by adjusting the current flowing in the light-emitting element 10 to reduce, the brightness of the light-emitting element 10 that is too bright is reduced, thereby reducing the brightness inconsistency among the light-emitting elements 10. However, if the brightness of a light-emitting element 10 is significantly lower than that of other light-emitting elements 10, there may be a light-emitting element 10 that cannot achieve a brightness that meets the specifications without significantly increasing the current. Fig.25 This is an example of a pixel driving circuit 100 that aims to increase brightness and reduce defects by allowing a large current to flow through such a low-brightness light-emitting element 10. That is, by providing a plurality of driving transistors 111N, a larger current than usual can be supplied to the light-emitting element 10.

[0263] Fig.25 The pixel driving circuit 100 and Fig.23 Similarly, the FET has a selection transistor 105, a holding capacitor 108, a test transistor 117, and a light emitting element 10. Fig.23The difference is that three driving transistors 111Na, 111Nb, and 111Nc are arranged in parallel, and non-volatile memory transistors 161a, 161b, and 161c are connected in series to each driving transistor 111Na, 111Nb, and 111Nc. The gate terminals of the driving transistors 111Na, 111Nb, and 111Nc are all connected to one terminal of the holding capacitor 108. The non-volatile memory transistors 161a, 161b, and 161c are driven through other control gates 160a, 160b, and 160c, respectively.

[0264] During the manufacturing stage of LSI7, Fig.24 Similarly, the pixel driving circuit 100 is tested by including the characteristics of the nonvolatile storage transistors 161a, 161b, and 161c. Next, at the stage where the LED display chip 1 is completed, the luminous intensity of each pixel 3 is measured with the control gate 160a turned on and 160b and 160c turned off, and the pixel 3EL (sometimes multiple pixels) whose luminous intensity is much lower than the lower limit of the specification (i.e., the allowable range of inconsistency of luminous intensity) is determined. For normal pixels 3 other than pixel 3EL, nonvolatile storage transistors 161b and 161c are written to increase the threshold voltage and become non-connected for the control gate voltage Vn. Next, for pixel EL, the luminous test is performed again with the control gates 160a and 160b turned on and 160c turned off. If the luminous intensity is above the lower limit of the specification in this state, the nonvolatile storage transistor 161c is written to increase the threshold voltage and become non-connected for the control gate voltage Vn. At this stage, for pixels whose luminous intensity is still insufficient, the luminous test is performed again with the control gates 160a, 160b, and 160c all turned on. In this way, a current about three times that of a normal pixel can flow through the luminous element 10. In this way, for pixels EL with increased luminous intensity, the current flowing through the luminous element 10 is adjusted by adjusting the threshold voltage of the non-volatile storage transistors 161b and 161c, thereby making it possible to bring the luminous intensity of the luminous element 10 within the specification. In addition, when the luminous intensity is higher than the specification, Fig.23 Similarly, by writing to the nonvolatile memory transistor 161 a and increasing the threshold voltage, the drive current of the drive transistor 111Na is reduced, thereby adjusting the brightness of the light emitting element 10 .

[0265] In the above example, three driving transistors 111Na, 111Nb, and 111Nc are configured, but it is not necessarily necessary to be three, and the driving transistor 111N may be multiple other than three. In addition, it is assumed that the multiple driving transistors 111N are all of the same size and the same driving current, but they do not necessarily need to be the same. For example, in a case where almost all low-brightness pixels 3 can be repaired by a current up to 1.5 times the current flowing in the standard element, the driving transistor 111N may also be two. In this case, one of them can be a smaller transistor with a driving current of about half (the gate width of the transistor is almost half) relative to the standard driving transistor 111N.

[0266] As described above, according to the present embodiment, the image forming element 1 is an image forming element 1 having a plurality of pixels 3 and projecting and displaying the emitted light of the pixels 3, and is configured to include: a light emitting element 10, which includes a light source 50 that emits light (which may be a blue LED chip 50, a bluish-purple LED chip 70, or an LED chip that emits light in other colors, but hereinafter represented by the blue LED chip 50); and a mounting substrate 7, on which a plurality of light emitting elements 10 are arranged on a mounting surface, and a plurality of light sources 50 that are monolithic and include at least one pixel 3 are arranged, the light sources 50 respectively having one or more power supply electrodes 40, 41 arranged on the same surface, the mounting substrate 7 having: a driving circuit 100 that drives the light source 50, and electrodes 19, 20 that are arranged on the mounting surface and electrically connected to the power supply electrodes 40, 41 of the light source 50, the driving circuit 100 including: at least one non-volatile storage transistor 161 for adjusting the light emission intensity of the light emitting element 10. According to this configuration, when the light emitting element 10 including the light source 50 is arranged on the mounting surface of the mounting substrate 7, the power supply electrodes 40 and 41 arranged on the same surface of the light source 50 can be electrically connected to the electrodes 19 and 20 arranged on the mounting surface. In addition, for example, when replacing a defective light source 56, it is possible to remove the defective light source 56 and install a normal light source 55 relatively easily and efficiently. In addition, since the plurality of light sources 50 are monolithic each including at least one pixel 3, it is possible to suppress the leakage of light to the adjacent pixel 3 through the inside of the light source 50. That is, it is possible to suppress the leakage of light to the dark pixel adjacent to the bright pixel. Therefore, it is possible to suppress or prevent the reduction of the contrast of the image formed by the projected light of the pixel 3 and the color mixing of the emitted light between the adjacent pixels 3. In addition, if the light source 50 is monolithic including a plurality of pixels 3, the number of light sources 50 to be arranged on the mounting substrate 7 by the light emitting element 10 including the light source 50 can be reduced, and the difficulty of its operation can also be improved. Therefore, the working efficiency is improved, and mass production is also easy. Furthermore, the light emission intensity of the light emitting element 10 is adjusted by at least one nonvolatile memory transistor 161. In this way, the permissible range of the inconsistency of the light emission intensity of the light emitting element 10 can be expanded, and the number of pixels to be repaired can be reduced. Therefore, an image forming element with excellent color rendering and high contrast can be manufactured with low defects and high yield.

[0267] The above is a description of the embodiments of the present invention. In addition, those skilled in the art will appreciate that the above embodiments are merely illustrative, and that various modifications may be made to the combination of various components and processes, all of which fall within the scope of the present invention.

[0268] For example, in the first to fifth embodiments, the pixels 3 of the pixel array 2 may be arranged in a two-dimensional manner other than N rows and M columns. For example, the plurality of pixels 3 may be arranged in a honeycomb shape.

[0269] The present invention is useful for, for example, a projector, a head-up display, a head-mounted display, a wearable terminal, and the like.

[0270] Description of Reference Numerals

[0271] 100 pixel drive circuit

[0272] 1 LED display chip

[0273] 2 Pixel Array

[0274] 3, 3s, 3t, 3u, 3v pixels

[0275] 4 Row selection circuit

[0276] 5-column signal output circuit

[0277] 6 Image Processing Circuit

[0278] 7 LSI

[0279] 8 Light Array

[0280] 10, 10s, 10t, 10u, 10v light emitting elements

[0281] 10a First light emitting element

[0282] 10b Second light emitting element

[0283] 11, 11s, 11t, 11u, 11v red light emitting element

[0284] 12, 12s, 12t, 12u, 12v green light emitting element

[0285] 13, 13s, 13t, 13u, 13v blue light emitting elements

[0286] 50 blue LED chips

[0287] 70 blue-violet LED chips

[0288] 19 N-side common electrode

[0289] 20 P side individual electrodes

[0290] 30 Sapphire substrate

[0291] 31 Compound semiconductor layer

[0292] 32 N-side epitaxial layer

[0293] 33 Luminous layer

[0294] 34 P-side epitaxial layer

[0295] 35. Transparent conductive film

[0296] 36 countertops

[0297] 37 Protective film

[0298] 38 P side contact hole

[0299] 39 N-side contact hole

[0300] 40 P side electrode

[0301] 41 N-side electrode

[0302] 42 Separation tank

[0303] 43. Keep the substrate

[0304] 44 Adhesive layer

[0305] 45 Transfer substrate

[0306] 46 Adhesive layer

[0307] 51 Anisotropic Conductive Film

[0308] 52 transparent substrate

[0309] 53 Transparent cushion

[0310] 54 Drive Current

[0311] 55 Normal LED chip

[0312] 56 Defective LED chips

[0313] 57 Micromanipulator

[0314] 58 Resist pattern

[0315] 60 Light-shielding reflective layer

[0316] 61 Dam layer

[0317] 62, 62R, 62G, 62B wavelength conversion layer

[0318] 63 Positive resist pattern

[0319] 100 pixel drive circuit

[0320] 101 Row Select Line (RoI)

[0321] 102, 102R, 102G, 102B column signal lines (CS)

[0322] 105, 105R, 105G, 105B selection transistor

[0323] 108, 108R, 108G, 108B holding capacitors

[0324] 114 Power line (Vcc)

[0325] 115 GND line

[0326] 111, 111R, 111G, 111B, 111N, 111Na, 111Nb, 111Nc driver transistors

[0327] 116 Test terminal (TE)

[0328] 117, 117R, 117G, 117B test transistor

[0329] 121 First element selection transistor

[0330] 122 Second element selection transistor

[0331] 140 Light-emitting element selection circuit

[0332] 145 Nonvolatile Memory Transistor

[0333] 146 Select transistor

[0334] 147 First Inverter Circuit

[0335] 148 Second inverter circuit

[0336] 149 Latch Transistor

[0337] 150 Signal line (FG)

[0338] 151 Signal line (SE)

[0339] 152 Signal line (SE-)

[0340] 153 First control gate

[0341] 154 Second control gate

[0342] 155 First nonvolatile storage transistor

[0343] 156 Second nonvolatile storage transistor

[0344] 160, 160a, 160b, 160c control gate terminal

[0345] 161, 161a, 161b, 161c non-volatile memory transistor

[0346] 160 Control gate terminal

[0347] 161 Nonvolatile Memory Transistor

[0348] 200 Silicon substrate

[0349] 201 P well layer

[0350] 202 N well layer

[0351] 203 STI layer

[0352] 204a, 204b N+ diffusion layer

[0353] 205 P+ diffusion layer

[0354] 206 gate poly-Si layer

[0355] 210 First layer metal wiring

[0356] 220 Second layer metal wiring

[0357] 230 Third layer metal wiring

[0358] 240 Fourth layer metal wiring

[0359] 250 interlayer insulation.

Claims

1. An image forming element comprising a plurality of pixels arranged in a two-dimensional array and projecting and displaying light emitted from the pixels, wherein the pixels include at least one light emitting element that emits the light emitted, wherein the image forming element is characterized in that: The image forming element comprises: a plurality of the light emitting elements, a mounting substrate on which the plurality of light emitting elements are mounted, a first light shielding layer, and a second light shielding layer. The mounting substrate includes a driving circuit for driving the light emitting element, and has individual electrodes on the mounting surface that are electrically connected to power supply electrodes of the light emitting element. At least a portion of the plurality of light emitting elements comprises a light source and a wavelength conversion layer, wherein the wavelength conversion layer converts the wavelength of light emitted by the light source and emits the light to the outside. The first light shielding layer is disposed around the light source and is formed of a light reflective or light absorbing material. The second light shielding layer is disposed between adjacent wavelength conversion layers and is formed of a material having light reflectivity or light absorption. The second light-shielding layer is disposed at least on a surface of the first light-shielding layer and a surface of the light source, and the second light-shielding layer on the surface of the light source is separated from the second light-shielding layer on the surface of the first light-shielding layer.

2. The image forming element according to claim 1, wherein: The height of the first light shielding layer is the same as the height of the light source from the surface facing the mounting substrate to the surface opposite to the surface facing the mounting substrate.

3. An image forming element comprising a plurality of pixels arranged in a two-dimensional array and projecting and displaying light emitted from the pixels, wherein the pixels include at least one light emitting element that emits the light emitted, wherein the image forming element is characterized in that: The image forming element comprises: a plurality of the light emitting elements, a mounting substrate on which the plurality of light emitting elements are mounted, a first light shielding layer, and a second light shielding layer. The mounting substrate includes a driving circuit for driving the light emitting element, and has individual electrodes on the mounting surface that are electrically connected to power supply electrodes of the light emitting element. At least a portion of the plurality of light emitting elements comprises a light source and a wavelength conversion layer, wherein the wavelength conversion layer converts the wavelength of light emitted by the light source and emits the light to the outside. The first light shielding layer is disposed around the light source and is formed of a light reflective or light absorbing material. The second light shielding layer is disposed between adjacent wavelength conversion layers and is formed of a material having light reflectivity or light absorption. The plurality of light sources include a compound semiconductor layer, the plurality of adjacent light emitting elements share at least a portion of the compound semiconductor layer and share an electrode having a polarity different from that of the individual electrodes, The plurality of light sources include a compound semiconductor layer, the plurality of adjacent light emitting elements share at least a portion of the compound semiconductor layer, and the second light shielding layer is provided on the compound semiconductor layer shared by the plurality of adjacent light emitting elements.

4. The image forming element according to claim 1 or 3, characterized in that: The first light-shielding layer and the second light-shielding layer are formed of the same material.

5. The image forming element according to claim 1 or 3, characterized in that: The first light shielding layer is formed of a resin in which a white pigment is dispersed.

6. The image forming element according to claim 1 or 3, characterized in that: The first light shielding layer is formed of a resin in which a black pigment is dispersed.

7. The image forming element according to claim 1 or 3, characterized in that: The wavelength conversion layer includes quantum dot material.

8. The image forming element according to claim 1 or 3, characterized in that: The wavelength conversion layer includes a color filter layer.

9. The image forming element according to claim 1 or 3, characterized in that: The second light shielding layer has high reflectivity and low light absorption.

10. A method for manufacturing an image forming element, the image forming element comprising a plurality of pixels and projecting and displaying light emitted from the pixels, the method comprising the following steps: A step of forming a driving circuit on a mounting substrate formed of a semiconductor substrate, wherein the driving circuit is used to drive a light source corresponding to the pixel; A step of forming a light emitting array, wherein the light emitting array is composed of a plurality of the light sources; A step of attaching the light emitting array to the mounting substrate; The step of providing a first light shielding layer between the plurality of light sources; a step of providing a second light-shielding layer made of a light-reflecting material on the first light-shielding layer and on a portion of the surface of the light source; as well as a step of providing a wavelength conversion layer on the light source, After the step of providing the second light shielding layer, the step of providing the wavelength conversion layer is performed.

11. The method for manufacturing an image forming element according to claim 10, wherein: The step of providing the wavelength conversion layer on the light source further comprises the following steps: forming a negative resist layer on the second light shielding layer; A step of insolubilizing a portion of the negative resist layer by exposure; as well as In the step of insolubilizing a portion of the negative resist layer by exposure, a step of dissolving the negative resist layer that has not been exposed.

12. A method for manufacturing an image forming element, the image forming element comprising a plurality of pixels and projecting and displaying light emitted from the pixels, the method comprising the following steps: A step of forming a driving circuit on a mounting substrate formed of a semiconductor substrate, wherein the driving circuit is used to drive a light source corresponding to the pixel; A step of forming a light emitting array, wherein the light emitting array is composed of a plurality of the light sources; A step of attaching the light emitting array to the mounting substrate; The step of providing a first light shielding layer between the plurality of light sources; a step of providing a second light shielding layer on the first light shielding layer; and a step of providing a wavelength conversion layer on the light source, After the step of providing the second light shielding layer, the method further comprises the following steps: forming a resist pattern, wherein the resist pattern covers a portion of the upper surface of the second light shielding layer; and a step of disposing the wavelength conversion layer on a portion of the upper surface of the second light shielding layer that is not covered by the resist pattern, The second light-shielding layer is disposed at least on a surface of the first light-shielding layer and a surface of the light source, and the second light-shielding layer on the surface of the light source is separated from the second light-shielding layer on the surface of the first light-shielding layer.

13. The method for manufacturing an image forming element according to any one of claims 10 to 12, characterized in that: After the step of attaching the light emitting array to the mounting substrate, the method further includes the step of providing a resist pattern on the surface of the light source.

14. The method for manufacturing an image forming element according to any one of claims 10 to 12, characterized in that: After the step of pasting the light emitting array onto the mounting substrate, the method further includes the step of providing a resist pattern on the surface of the light source. The process of providing the first light-shielding layer and the process of providing the second light-shielding layer are performed simultaneously.

15. The method for manufacturing an image forming element according to any one of claims 10 to 12, characterized in that: The wavelength conversion layer includes quantum dot material.

Images