JP2020085952A - Micro led display device, and micro led display device wiring method - Google Patents

Abstract

To cause light emission efficiency with respect to a dimension of a micro LED not to fall in a micro LED display device having a micro LED arrayed in a matrix way, and having matrix wiring lines connected to a p-type semiconductor layer and an n-type semiconductor layer respectively.SOLUTION: A micro LED display device comprises: a plurality of first electrode wiring lines that are formed on a substrate, and are extendedly provided in an X-direction and lined parallely in a Y-direction; a micro LED that includes a vertical type structure having a first semiconductor layer, a light emission layer and a second semiconductor layer laminated along a Z-direction going across a surface of the substrate, in which the first semiconductor layer is connected onto the first electrode wiring line; an insulation film that is formed on the substrate having the first electrode wiring line formed, and opens a light emission area of the micro LED; and a plurality of second electrode wiring lines that are formed on the insulation film so as to be connected to a lateral face of the second semiconductor layer, and are extendedly provided in the Y-direction and lined parallely in the X-direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to a micro LED display device and a wiring method for the micro LED display device.

A display device (display) using a light emitting diode (LED) is conventionally known. On the other hand, the micro LED technology is a technology premised on miniaturizing the size of a single LED to a level of several μm to several tens of μm. ) Is a display unit (for example, a pixel), the display device can be made lighter, thinner, shorter, smaller, higher in brightness, higher in definition, and more energy-saving, and in addition to the miniaturized micro LED. It is attracting attention as a material for realizing next-generation displays such as a transparent display having a transparent substrate and a flexible display having a substrate on which a micro LED is mounted as a flexible substrate.

It is said that there are some problems to be solved in order to mass-produce the micro LED display device, and one of them is how to mount and wire the micro LED at low cost and efficiently. It's a problem. Conventionally, flip-chip mounting is performed for mounting arrayed LEDs. However, even in a micro LED display device, flip-chip mounting that can reduce the mounting area compared to wire bonding can be adopted. It has been proposed (see Patent Document 1 below).

Patent No. 6383074

FIG. 1 shows a conventional technique in which a single micro LED is mounted on a wiring board by flip chip mounting. In order to form a display device in which a plurality of micro LEDs 100 are arranged in a matrix, it is necessary to form matrix wiring for connecting the plurality of arranged micro LEDs 100 on the substrate 110. The matrix wiring is composed of, for example, a lower-layer n-electrode wiring 111 extending in a direction orthogonal to each other and an upper-layer p-electrode wiring 113 formed on the lower-layer n-electrode wiring 111 via an insulating film 112. It

The flip-chip mounted micro LED 100 includes an n-type semiconductor layer 101, an active layer (light-emitting layer) 102, and a p-type semiconductor layer 103, and the n-type semiconductor layer 101 is an n-th layer under the insulating film 112 via a through hole. The p-type semiconductor layer 103 is connected to the n-electrode 104 connected to the electrode wiring 111, and is connected to the upper-layer p-electrode wiring 113 wired on the insulating film 112 via the p-electrode 105.

In such a conventional technique, since the n-electrode 104 and the p-electrode 105 are provided on the same surface side of the micro LED 100, the light-emitting portion can be obtained only in the area overlapping at least the p-electrode 105. For this reason, when the size of the micro LED 100 becomes smaller, the area of the n-electrode 104 cannot be reduced accordingly, so that the area occupied by the n-electrode 104 with respect to the size of the micro LED 100 becomes larger, and the micro LED 100 becomes larger. There is a problem in that the light emission efficiency with respect to the dimension is reduced.

The present invention has been proposed to address such a problem. That is, in a micro LED display device in which micro LEDs are arranged in a matrix and matrix wirings are respectively connected to the p-type semiconductor layer and the n-type semiconductor layer, the light emission efficiency with respect to the size of the micro LEDs is not reduced. The problem is to improve the productivity of the micro LED display device by efficiently forming the matrix wiring connected to the micro LED.

In order to solve such a problem, the present invention has the following configurations.
A micro LED display device in which a plurality of micro LEDs are arranged in a matrix in an X direction which is one direction along a surface of a substrate and a Y direction along a surface of the substrate which intersects the X direction, the micro LED being formed on the substrate. A plurality of first electrode wirings extending in the X direction and arranged in parallel in the Y direction, and a first semiconductor layer, a light emitting layer, and a second semiconductor layer are stacked along the Z direction intersecting the surface. A micro LED having a vertical structure, in which the first semiconductor layer is connected to the first electrode wiring, and a light emitting region of the micro LED formed on the substrate on which the first electrode wiring is formed. An opened insulating film, and a plurality of second electrode wirings formed on the insulating film so as to be connected to the side surface of the second semiconductor layer, extended in the Y direction, and arranged in parallel in the X direction. A micro LED display device comprising:

A micro LED display device having such characteristics is a micro LED in which micro LEDs are arranged in a matrix and matrix wirings are respectively connected to a p-type semiconductor layer (first semiconductor layer) and an n-type semiconductor layer (second semiconductor layer). In the LED display device, matrix wiring can be performed without reducing the light emission efficiency with respect to the size of the micro LED. Further, by efficiently forming the matrix wiring connected to the micro LED, the productivity of the micro LED display device can be improved.

It is an explanatory view explaining a micro LED display device by flip chip mounting of the prior art. It is explanatory drawing which showed the structural example of the micro LED display apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing which showed the wiring structure of the micro LED simple substance of the micro LED display apparatus in FIG. It is explanatory drawing which showed the structural example of the micro LED display apparatus which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which showed the wiring structure of the micro LED simple substance of the micro LED display apparatus in FIG. It is explanatory drawing (formation of 1st electrode wiring and the mounting process of micro LED) explaining an example of the wiring method of the micro LED display apparatus which concerns on embodiment of this invention. FIG. 6 is an explanatory view (insulating film formation and recess formation step) for explaining an example of a wiring method of the micro LED display device according to the embodiment of the present invention. It is explanatory drawing (2nd electrode wiring formation process) explaining an example of the wiring method of the micro LED display apparatus which concerns on embodiment of this invention. It is explanatory drawing which showed the example of the color display of the micro LED display apparatus which concerns on embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals in different drawings indicate the parts having the same functions, and redundant description in each drawing will be appropriately omitted. In each figure, the direction of arrow X (X direction) is one direction on the substrate surface, the direction of arrow Y (Y direction) intersects the X direction on the substrate surface, and the direction of arrow Z (Z direction) intersects the substrate surface. Pointing in the direction you want to.

As shown in FIGS. 2 and 3, in the micro LED display device 1 according to one embodiment, a plurality of micro LEDs 10 are arranged in the X direction, which is one direction along the surface of the substrate 20, and along the surface of the substrate intersecting with the X direction. It is arranged in a matrix in the Y direction. As shown in FIG. 3, the single micro LED 10 has the first semiconductor layer 11, the light emitting layer 12, and the second semiconductor layer 13 stacked along the Z direction intersecting the surface (XY plane) of the substrate 20. It has a vertical structure.

A first electrode wiring 21 and a second electrode wiring 22 are arranged on the substrate 20 so as to intersect three-dimensionally to form a matrix wiring. The first electrode wirings 21 are formed on the substrate 20 directly or via an insulating film or the like, and the individual first electrode wirings 21 are extended in the X direction shown in the drawing, and the plurality of first electrode wirings 21 are formed. Are arranged in parallel in the Y direction shown. The second electrode wiring 22 is formed on the insulating film 23 formed on the substrate 20 on which the first electrode wiring 21 is formed, and each second electrode wiring 22 is extended in the Y direction shown in the drawing. In addition, the plurality of second electrode wirings 22 are arranged in parallel in the X direction shown.

The first semiconductor layer 11 of the micro LED 10 is connected to the first electrode wiring 21, and the side surface 13A (YZ surface) of the second semiconductor layer 13 of the micro LED 10 is connected to the second electrode wiring 22. ing. The upper surface 13B of the micro LED 10 serving as a light emitting region is exposed from the opening of the insulating film 23, and no electrode connecting portion is formed on the upper surface 13B.

In the illustrated example, the recess 23A is formed in the insulating film 23, the side surface 13A of the second semiconductor layer 13 of the micro LED 10 is exposed in the recess 23A, and the second electrode wiring 22 is formed in the recess 23A. Then, the second electrode wiring 22 is connected to the side surface 13A of the second semiconductor layer 13. However, the present invention is not limited to this, and the side surface 13A of the second semiconductor layer 13 is exposed on the insulating film 23 by forming the insulating film 23 to be thinner than the vertical thickness of the vertical type micro LED 10, for example. Then, by forming the second electrode wiring 22 on the insulating film 23, the second electrode wiring 22 may be connected to the side surface 13A of the second semiconductor layer 13.

4 and 5 show a micro LED display device 1 according to another embodiment. The example shown in FIGS. 4 and 5 has a configuration in which the second electrode wiring 22 has an opening in the light emitting region therein, and the micro LED 10 is arranged in the opening, and The points are the same as the examples shown in FIGS. 2 and 3. In the example shown in FIGS. 4 and 5, the second electrode wiring 22 is connected to the side surface 13A of the second semiconductor layer 13 of the micro LED 10 on the four surfaces inside the opening provided in the second electrode wiring 22.

The first semiconductor layer 11 in the micro LED 10 is, for example, p-GaN, the second semiconductor layer 13 is n-GaN, and the light emitting layer 12 is an active layer having an MQW (Multiple Quantum Well) structure. The material of the micro LED 10 is not particularly limited, and various semiconductor materials capable of forming the vertical micro LED 10 can be used.

For the first electrode wiring 21 and the second electrode wiring 22, a conductive metal such as Al, Au, Ag, Cu can be used. Further, the first electrode wiring 21 and the second electrode wiring 22 can be formed as a single layer or a multilayer film made of a conductive material such as Ni. The insulating layer 23 can be made of a resin material such as epoxy, polyimide or silicone, or an inorganic material such as alumina or silica.

The substrate 20 may be made of any material, such as glass or resin, as long as it can insulate the first electrode wiring 21, and if an insulating coating is formed on the underlying layer of the first electrode wiring 21, Further, any material including a conductive material such as metal can be used. Further, the substrate 20 is not limited to a rigid plate body, and may be a flexible film body or the like.

In such a micro LED display device 1, an electrode connecting portion is provided on the upper surface 13B of the second semiconductor layer 13 which is a light emitting region in each of the micro LEDs 10 arranged in a matrix on the substrate 20. Since it does not exist, it is possible to drive the plurality of micro LEDs 10 for display without lowering the light emission efficiency with respect to the size of the micro LEDs 10.

When the micro LED 10 emits ultraviolet rays, the upper surface 13B of each individual micro LED 10 is exposed from the opening of the insulating film 23 or the second electrode wiring 22 and there is nothing that blocks the upper surface 13B which is a light emitting region. It is possible to emit ultraviolet rays having a desired wavelength without being restricted by the transmission wavelength.

Next, an example of a forming method (wiring method) of the micro LED display device 1 will be described with reference to FIGS. The formation of the micro LED display device 1 shown here includes the step of forming the first electrode wiring shown in FIGS. 6A and 6B, the step of mounting the micro LED shown in FIG. Although the steps of forming the insulating film shown in a) to (c) and the step of forming the second electrode wiring shown in FIG. 8 are included, the method is not particularly limited to this method.

First, in the step of forming the first electrode wiring, as shown in FIG. 6B, a plurality of first electrode wirings are formed on the flat plate-shaped or film-shaped substrate 20 prepared as shown in FIG. 6A. 21 are formed in parallel. At this time, a metal material such as Al or Cu is formed on the substrate 20 by a film forming technique such as sputtering, plating, or vapor deposition to a thickness of, for example, about 500 nm, and then a photolithographic technique or the like is used to show X in the drawing. The plurality of first electrode wirings 21 extending in the direction and arranged in parallel in the Y direction in the drawing are patterned.

After forming the first electrode wiring 21 on the substrate 20, as shown in FIG. 6( c ), the micro LED 10 previously formed and divided into dimensions of several μn to several tens μm□ is attached to the first electrode wiring 21. 21 are arranged in a matrix. Here, the first semiconductor layer 11 of the micro LED 10 is connected on the first electrode wiring 21.

After arranging the micro LEDs 10 on the first electrode wiring 21, as shown in FIG. 7A, an insulating film 23 which is a photosensitive resin film is formed. The insulating film 23 is formed by coating or the like on the substrate 20 on which the first electrode wiring 21 is formed. For example, if the height of the micro LED 10 is 10 μm, the insulating film 23 has a thickness of about 8 to 9 μm so that the upper portion of the micro LED 10 projects from the surface of the insulating film 23. This is to prevent the insulating film 23 from covering the upper surface 13B of the micro LED, which is the light emitting region, whereby the insulating film 23 is formed so that the light emitting region of the micro LED 10 is opened.

Next, as shown in FIG. 7B, the exposure mask 30 is installed so that the opening 31 is aligned with the side surface 13A of the micro LED 10, and exposure, development, and etching are performed by a photolithography process. An insulating film 23 having a pattern of recesses 23A as shown in FIG. 7C is formed. As a result, the side surface 13A of the second semiconductor layer 13 in the micro LED 10 is exposed in the recess 23A. At this time, the size of the recess 23A can be set to have a width of about 1 to 5 μm and a depth of about 2 to 3 μm. The depth of the recess 23A needs to be set so that the light emitting layer 12 of the micro LED 10 is not exposed.

Next, as shown in FIG. 8A, a film forming mask 40 is formed. The film forming mask 40 is a mask layer in which an opening 41 corresponding to the pattern of the recess 23A is formed, and is removed after the layer of the second electrode wiring 22 is formed in the recess 23A by sputtering or vapor deposition. It is a thing. As shown in FIG. 8B, the micro LED display device 1 is completed by removing the film forming mask 40 after forming the second electrode wiring 22.

According to such a wiring method of the micro LED display device 1, it becomes possible to collectively connect the plurality of micro LEDs 10 by forming the second electrode wiring 22. Thereby, the wiring cost can be reduced and the efficiency can be improved, and the productivity of the micro LED display device 1 can be improved.

FIG. 9 shows a configuration example when the micro LED display device 1 is used as a color display device. Here, the light wavelength conversion unit 50 is provided on the light emission side of the micro LED 10 that emits ultraviolet rays UV. The light wavelength conversion unit 50 emits visible light excited by the ultraviolet UV emitted from the micro LED 10, and emits a phosphor 51 that emits red light by the ultraviolet UV and a green light by the ultraviolet UV. And a phosphor 53 that emits blue light by ultraviolet UV. Each phosphor 51, 52, 53 is partitioned by a partition wall 54, and a support 55 that transmits ultraviolet rays is provided on the micro LED 10 side of the phosphors 51, 52, 53. A filter layer 56 that transmits visible light and absorbs ultraviolet light is provided on the light emission side. By providing such a light wavelength conversion unit 50, the micro LED display device 1 capable of full-color display can be realized.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and changes in design within the scope not departing from the gist of the present invention, etc. Even so, it is included in the present invention. Further, the respective embodiments described above can be combined by diverting each other's technology as long as there is no contradiction or problem in the purpose and the configuration.

1: Micro LED display device,
10: Micro LED,
11: first semiconductor layer, 12: light emitting layer, 13: second semiconductor layer,
13A: side surface, 13B: top surface,
20: substrate, 21: first electrode wiring, 22: second electrode wiring, 23: insulating film,
30: exposure mask, 31: aperture,
40: mask for film formation, 41: opening,
50: light wavelength conversion part, 51, 52, 53: phosphor, 54: partition wall,
55: support, 56: filter layer

Claims (7)

A micro LED display device in which a plurality of micro LEDs are arranged in a matrix in an X direction, which is one direction along a surface of a substrate, and a Y direction, which is along a surface of a substrate intersecting with the X direction.
A plurality of first electrode wirings formed on the substrate, extending in the X direction and arranged in parallel in the Y direction;
A micro LED having a vertical structure in which a first semiconductor layer, a light emitting layer, and a second semiconductor layer are stacked along a Z direction intersecting with the surface, and the first semiconductor layer is connected to the first electrode wiring. When,
An insulating film formed on the substrate on which the first electrode wiring is formed and having an opening in a light emitting region of the micro LED;
A plurality of second electrode wirings formed on the insulating film so as to be connected to the side surface of the second semiconductor layer, extending in the Y direction, and arranged in parallel in the X direction. Micro LED display device. The micro LED display device according to claim 1, wherein the second electrode wiring is formed in a recess formed in the insulating film. 3. The micro LED display device according to claim 1, wherein the second electrode wiring has an opening inside the light emitting region. The micro LED display device according to claim 1, wherein the first semiconductor layer is p-GaN and the second semiconductor layer is n-GaN. 5. A light wavelength conversion unit that emits visible light excited by the ultraviolet light emitted from the micro LED is provided on the light emission side of the micro LED. The described micro LED display device. Extending a first electrode wiring in the X direction on the substrate, and arranging a plurality of the first electrode wirings in parallel in the Y direction on the substrate intersecting the X direction;
A micro LED having a vertical structure in which a first semiconductor layer, a light emitting layer, and a second semiconductor layer are stacked along a Z direction intersecting the surface is connected to the first semiconductor layer on the first electrode wiring. And arranging them in a matrix,
A step of forming an insulating film on the substrate on which the first electrode wiring is formed so that a light emitting region of the micro LED is opened;
A second electrode wiring is extended on the insulating film in the Y direction so as to be connected to a side surface of the second semiconductor layer, and a plurality of the second electrode wirings are arranged in parallel on the insulating film in the X direction. A wiring method for a micro LED display device, comprising: 7. The wiring method for a micro LED display device according to claim 6, further comprising the step of forming a concave portion in which the side surface of the second semiconductor layer is exposed in the insulating film prior to forming the second electrode wiring.

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