阅读说明：本技术 微型发光元件、图像显示元件及其制造方法 (Micro light emitting device, image display device and method of manufacturing the same ) 是由 井口胜次 于 2019-05-31 设计创作，主要内容包括：一种在内置有微型发光元件(100)的驱动电路的驱动电路基板(50)之上,连接了所述微型发光元件(100)的图像显示元件,上述微型发光元件(100)在与上述驱动电路的接合面的相反侧具有光出射面,上述微型发光元件(100)的结合面侧的表面与上述驱动电路基板(50)的结合面侧的表面中的任一个具有凹凸形状,上述微型发光元件(100)的P电极(19P)与N电极(19N)、和上述驱动电路基板(50)侧的P侧电极(51)与N侧电极(52)经由金属纳米粒子(30)而连接,上述微型发光元件(100)的结合面侧的表面与上述驱动电路基板(50)的结合面侧的表面之间所形成的空隙填充有光固化树脂(31)。由此,抑制材料不同的微型发光元件(100)与驱动电路基板(50)的温度上升并使它们贴合。(An image display device in which a micro light emitting element (100) is connected to a driver circuit board (50) having a driver circuit of the micro light emitting element (100) built therein, the micro light emitting element (100) has a light emitting surface on the opposite side of the bonding surface to the drive circuit, either the surface of the micro light-emitting element (100) on the bonding surface side or the surface of the drive circuit board (50) on the bonding surface side has a concave-convex shape, the P-electrode (19P) and the N-electrode (19N) of the micro light-emitting element (100) and the P-side electrode (51) and the N-side electrode (52) on the side of the drive circuit board (50) are connected via metal nanoparticles (30), a gap formed between the surface of the micro light-emitting element (100) on the bonding surface side and the surface of the drive circuit board (50) on the bonding surface side is filled with a light-curing resin (31). Thus, the micro light-emitting element (100) and the drive circuit substrate (50) are bonded together while suppressing temperature rise in the micro light-emitting element and the drive circuit substrate.)

1. An image display device in which a plurality of micro light-emitting elements having a light emitting surface on the opposite side of a bonding surface with a driving circuit having the micro light-emitting elements built therein are connected to the driving circuit substrate of the driving circuit,

At least one of a surface of the micro light-emitting element on the bonding surface side and a surface of the driver circuit board on the bonding surface side has a concave-convex shape,

The electrodes of the micro light-emitting elements are connected to the electrodes on the substrate side of the drive circuit via metal nanoparticles,

A gap formed between a surface of the micro light-emitting element on the bonding surface side and a surface of the driving circuit board on the bonding surface side is filled with a light-curing resin.

2. Image display element according to claim 1,

The surface of the micro light-emitting element on the bonding surface side is flat, and the surface of the driving circuit board on the bonding surface side has a concave-convex shape.

3. Image display element according to claim 2,

the convex portion of the surface of the drive circuit board on the bonding surface side is an electrode.

4. Image display element according to claim 1,

The surface of the driver circuit board on the bonding surface side is flat, and the surface of the micro light-emitting element on the bonding surface side has a concave-convex shape.

5. Image display element according to claim 4,

The convex portion of the surface of the micro light-emitting element on the bonding surface side is an electrode.

6. Image display element according to claim 4,

The concave portion of the surface of the bonding surface side of the micro light-emitting element is a dividing groove portion for dividing the light-emitting layer of the micro light-emitting element.

7. Image display element according to claim 1,

The surface of the micro light-emitting element on the bonding surface side has a concave-convex shape, and the surface of the drive circuit board on the bonding surface side also has a concave-convex shape.

8. Image display element according to claim 7,

The convex portion of the surface of the micro light-emitting element on the bonding surface side is an electrode, the concave portion is a dividing groove portion for dividing the light-emitting layer of the micro light-emitting element, and the convex portion of the surface of the driving circuit board on the bonding surface side is an electrode.

9. image display element according to claim 1,

The metal nanoparticles are disposed on the surface of the micro light-emitting element on the bonding surface side.

10. Image display element according to claim 1,

the metal nanoparticles are disposed on the surface of the driver circuit board on the side of the bonding surface.

11. Image display element according to claim 1,

The image display device includes a dummy element made of the same material as a micro light emitting element and a dummy region in which a dummy electrode corresponding to the dummy element is disposed on the drive circuit substrate, the dummy element being disposed on an outer periphery of a pixel region of the image display element and formed of a pixel which emits light, and a gap between the dummy element and the drive circuit substrate is different from that of the pixel region.

12. Image display element according to claim 11,

The dummy electrode of the dummy element and the dummy electrode of the drive circuit on the substrate side are both longer than the pixel portion.

13. Image display element according to claim 11,

the dummy element has a dividing groove portion longer than the pixel portion.

14. Image display element according to claim 11,

The pattern of the void between the dummy element and the driving circuit substrate is different depending on the side of the pixel region.

15. image display element according to claim 11,

Setting as follows: the dummy region has a small gap on a side close to an external connection region of the image display element, and the dummy region has a large gap on a side far from the external connection region.

16. Image display element according to claim 11,

The dummy region has a small gap in the central portion and a large gap in the peripheral portion.

17. Image display element according to claim 1,

The amount of leakage of the light-curing resin from the side near the external connection region of the image display element is smaller than the amount of leakage of the light-curing resin from the side far from the external connection region.

18. A method for manufacturing an image display element, comprising:

Forming a micro light-emitting element made of a compound semiconductor on a growth substrate;

Forming a drive circuit board including a drive circuit;

Arranging metal nanoparticles on one of a bonding surface of the micro light-emitting element and a bonding surface of the driver circuit board;

Disposing the micro light-emitting element on the drive circuit board;

injecting a light-curing resin between the micro light-emitting elements on the driving circuit board;

Irradiating the light-curable resin with light and curing the light-curable resin; and

And peeling the growth substrate.

19. The method for manufacturing an image display element according to claim 18,

the step of irradiating the light-curable resin with light and curing the light-curable resin is performed through the growth substrate.

20. The method for manufacturing an image display element according to claim 18,

The step of disposing the micro light-emitting elements on the driver circuit board includes a step of injecting a light-curing resin into a dummy element portion formed simultaneously with the micro light-emitting elements, and curing the resin by light irradiation.

Technical Field

The invention relates to a micro light emitting device, an image display device and a method of manufacturing the same.

Background

A display device including a plurality of micro light emitting elements constituting pixels on a drive circuit substrate is proposed. As such a display element, for example, patent document 1 discloses a small display element that displays a color image. In the display element, a driving circuit is formed on a silicon substrate, and a micro ultraviolet Light Emitting Diode (LED) array is arranged thereon. In addition, in the display element, a wavelength conversion layer that converts ultraviolet light into visible light of red, green, and blue is provided over the ultraviolet light emitting diode.

Such a display device is small in size, and has characteristics such as high luminance and high durability. Therefore, the display device is expected to be used as a display element for a display device such as a glasses-type terminal and a head-up display (HUD).

In such a display element, the materials constituting the driver circuit board and the micro light-emitting element are different from each other, and a step of bonding the two is required. (see patent documents 1 and 2).

Disclosure of Invention

technical problem to be solved by the invention

in a process of manufacturing a display device for a micro projector by attaching micro LEDs to an LSI on which a drive circuit is formed, a group of micro LEDs to be light emitting portions is attached to a wafer on which the drive circuit LSI is formed, and it is necessary to electrically connect electrodes of the micro LEDs to electrodes of the drive circuit in a one-to-one correspondence. The size of one micro LED is about 50 μm to several μm, and the number of the micro LEDs is several tens of thousands to several millions. Therefore, the size of one electrode is very small in the range of about 1 μm to about 10 μm. Further, the difference in thermal expansion coefficient between the GaN layer constituting the micro LED and the sapphire substrate as a growth substrate is large relative to the silicon substrate constituting a normal drive circuit, and if the temperature is raised in the bonding step, the design positions of the electrodes on the drive circuit LSI and the electrodes of the micro LED are shifted by the difference in thermal expansion coefficient, and the small electrodes may not overlap each other. Even if the connection is made by arranging the patterns so as to overlap each other in a state of temperature rise, a large thermal stress is generated and the connection is broken as long as the temperature returns to room temperature.

In order to avoid such a problem, patent document 2 proposes a method of connecting without raising the temperature, but a special cylindrical electrode structure must be provided for connection, and application to a fine electrode is difficult. Further, a large stress needs to be applied for connection, and when the display element has a higher resolution and the number of electrodes to be connected is increased, a very large stress needs to be applied. For this reason, the method disclosed in patent document 2 is difficult to apply to a high-resolution display element.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for bonding electrodes appropriately while suppressing temperature increase in bonding with a large number of bonding electrodes and a small electrode size.

Means for solving the problems

(1) One embodiment of the present invention is an image display device in which an image display device (image display device) including a plurality of micro light emitting devices (light emission devices) having a light emitting surface on a side opposite to a bonding surface (bonding surface) to a driving circuit is connected to a driving circuit board (driving circuit substrate) including the driving circuit,

at least one of a surface of the micro light-emitting element on the bonding surface side and a surface of the driver circuit board on the bonding surface side has a concave-convex shape,

The electrodes of the micro light-emitting elements and the electrodes on the substrate side of the driving circuit are connected via metal nanoparticles,

A photo-curing resin (photo-curing resin) is filled in a space (space) formed between the surface of the micro light-emitting element on the bonding surface side and the surface of the driving circuit board on the bonding surface side.

(2) In addition, in the image display device according to the embodiment of the present invention, in addition to the configuration (1), a dummy device made of the same material as that of the micro light emitting device and a dummy electrode corresponding to the dummy device are disposed on the drive circuit substrate on the outer periphery of a pixel region of the image display device, the pixel region being formed of a pixel which emits light, and a gap between the dummy device and the drive circuit substrate is different from that of the pixel region.

(3) In addition, according to an embodiment of the present invention, in the configuration of (2), a pattern of a gap between the dummy element and the driver circuit board is different depending on a side of the pixel region.

(4) One embodiment of the present invention is a method for manufacturing an image display element, including:

forming a micro light-emitting element made of a compound semiconductor on a growth substrate; forming a drive circuit board including a drive circuit;

Arranging metal nanoparticles on one of a bonding surface of the micro light-emitting device and a bonding surface of the driver circuit board;

Disposing the micro light-emitting device on the drive circuit board;

Injecting a light-curable resin between the micro light-emitting elements on the drive circuit board; and irradiating the light-curable resin with light to cure the light-curable resin.

(5) In addition, the manufacturing method according to an embodiment of the present invention is an image display device in which the step of irradiating the light-curable resin with light and curing the light-curable resin is performed through the growth substrate in addition to the configuration of (4).

(6) In addition to the configuration of (4), the method for manufacturing an image display device according to an embodiment of the present invention includes a step of injecting a light-curing resin into a dummy device portion formed simultaneously with the micro light-emitting devices and curing the resin by light irradiation.

Effects of the invention

According to one embodiment of the present invention, it is possible to realize bonding with a large number of bonding electrodes and a small electrode size, which cannot be realized by a conventional device, while suppressing temperature increase.

Drawings

Fig. 1 is a sectional view of a pixel portion of an image display element according to a first embodiment of the present invention.

Fig. 2 is a plan view of a micro light-emitting element according to a first embodiment of the present invention.

Fig. 3 is a manufacturing process of a micro light emitting device according to a first embodiment of the present invention.

fig. 4 is a manufacturing process of an image display element according to a first embodiment of the present invention.

Fig. 5 (a) is a plan view of the image display element according to the first embodiment of the present invention, and fig. 5 (b) and (c) are cross-sectional views of the outer peripheral portion of the image display element according to the first embodiment of the present invention.

Fig. 6A is a plan view of a micro light-emitting element according to a modification of the first embodiment of the present invention.

Fig. 6B is a plan view of a micro light-emitting element according to another modification of the first embodiment of the present invention.

Fig. 7 is a sectional view of an image display element according to a second embodiment of the present invention.

Fig. 8 is a process for manufacturing a micro light-emitting device according to a second embodiment of the present invention.

fig. 9 is a manufacturing process of an image display element according to a second embodiment of the present invention.

Fig. 10 is a manufacturing process of an image display element according to a third embodiment of the present invention.

Fig. 11 is a process for manufacturing a micro light-emitting device according to a third embodiment of the present invention.

fig. 12 is a manufacturing process of an image display element according to a third embodiment of the present invention.

Fig. 13 is a process for manufacturing a micro light-emitting device according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

[ first embodiment ]

an embodiment of the present invention is explained below.

[ outline of the structure of the image display element ]

next, an image display device 200 having a plurality of micro light emitting devices 100 as a light source is taken as an example, and an embodiment of the present invention will be described with reference to the drawings (fig. 1 and the like). The image display device 200 includes a plurality of micro light-emitting devices 100 in a pixel region (pixel region)1 (fig. 5). The image display device 200 includes a driving circuit board 50 for supplying a current to the micro light-emitting device 100 and emitting light. The light emitted from the micro light-emitting element 100 is emitted to the opposite side of the driver circuit board 50. In the following, the case of using single crystal silicon as the material of the driver circuit board 50 is described, but a glass substrate or a plastic substrate on which polycrystalline silicon TFTs or IGZO-TFTs are formed may be used.

The wavelength conversion layer (wavelength conversion layer), the light diffusion layer (light diffusion layer), the color filter, the microlens, and the like may be disposed on the light emission side of the micro light-emitting element 100, but are not directly related to the present invention and are not shown in the drawings.

The driving circuit board 50 includes a micro light emitting element driving circuit (micro light emitting element drive circuit), a row selection circuit (row selection circuit), a column signal output circuit (column signal output circuit), an image processing circuit (image processing circuit), an input/output circuit (input/output circuit), and the like. The micro light-emitting element driving circuit controls the current supplied to each micro light-emitting element 100. The row selection circuit selects each row of the micro light-emitting elements 100 arranged in a two-dimensional matrix. Further, the column signal output circuit outputs a light emission signal to each column of the micro light-emitting elements 100. Further, the image processing circuit calculates a light emission signal based on the input signal.

A P-side electrode 51 (second drive electrode) and an N-side electrode 52(N-drive electrode) (first drive electrode) for connecting to the micro light-emitting element 100 are disposed on the surface of the drive circuit board 50 on the bonding surface side.

In general, the drive circuit board 50 is a silicon substrate (semiconductor substrate) on which an LSI (Large-Scale Integrated circuit) is formed, and can be manufactured by a known technique, and therefore, the function and configuration thereof will not be described in detail.

The cross section along the substrate surface of the micro-light emitting element 100 may have various planar shapes such as a rectangle, a polygon, a circle, and an ellipse. The maximum length in the direction along the substrate surface is assumed to be 60 μm or less.

Further, it is assumed that the image display device 200 integrates more than 3 thousand micro light emitting devices 100 in the pixel region 1.

The micro light-emitting device 100 includes a compound semiconductor 14 as a light-emitting body (light emission portion), and generally includes an N-side layer (N-side layer)11 (first conductive layer), a light-emitting layer (light emission layer)12, and a P-side layer (P-side layer)13 (second conductive layer) stacked in this order.

The compound semiconductor 14 is a nitride semiconductor (AlInGaN system) in a micro LED device that emits light in a wavelength band from ultraviolet to green, for example. When the compound semiconductor 14 emits light in a wavelength band from yellow green to red, it is an AlInGaP system. Further, the compound semiconductor 14 is an AlGaAs system or a GaAs system in a wavelength band from red to infrared.

In the following, a configuration in which the N-side layer is disposed on the light emitting side will be specifically described with respect to the compound semiconductor 14 constituting the micro light-emitting element 100. However, the compound semiconductor 14 may be configured such that the P-side layer 13 is disposed on the light emitting side.

each of the N-side layer 11, the light-emitting layer 12, and the P-side layer 13 is preferably a non-single layer and includes a plurality of layers in general, but since it is not directly related to the present invention, a specific structure of each layer is not described. In general, the light-emitting layer is sandwiched between an N-type layer (N-type layer) and a P-type layer (P-type layer), and the N-type layer and the P-type layer may be undoped layers or may include layers having opposite conductivity dopants as appropriate, and will be referred to as an N-side layer and a P-side layer hereinafter.

[ details of image display element 200 ]

As shown in fig. 1, the image display device 200 is configured such that the micro light-emitting device 100 emitting light is bonded to the driving circuit board 50 with a bonding surface (indicated by a thick broken line). In the micro light-emitting element 100, the light-emitting layer 12 is divided by a dividing groove (isolationrench) 15. A P-electrode (second electrode)19P connected to the P-side layer 13 is disposed in the pixel region 1 in a region where the light-emitting layer 12 remains. In addition, an N-electrode (first electrode)19N (first electrode) connected to the N-side layer 11 is disposed in a region (isolation region) of the dividing groove 15 in the pixel region 1.

The P-electrode 19P and the N-electrode 19N are formed simultaneously in the same step as described later, and therefore have different shapes, sizes, and depths, but are formed of wiring materials (wiring materials) having the same structure as the material. The wiring material generally has a laminated structure of a plurality of layers of a barrier metal layer (barrier metal layer), a main conductive layer (conductive layer), a cap layer (cap layer), and the like, but the P electrode 19P and the N electrode 19N have the same laminated structure. That is, the micro light-emitting element 100 side of the image display element 200 is constituted by a single wiring layer.

In the configuration of the present embodiment, the P-electrode 19P and the N-electrode 19N are formed of a metal material that is ohmically connected to the N-side layer 11, and therefore, ohmic connection to the P-side layer 13 can be performed via the P-electrode layer (P-electrode layer) 10. When the compound semiconductor 14 is a nitride semiconductor, the P electrode layer 10 is a good conductor such as ITO (Indium-Tin-Oxide) or palladium (Pd), which is a transparent electrode.

The protection film (protection layer)17 is embedded in the dividing groove 15 of the micro light-emitting element 100, and the surface (second surface) of the protection film 17 on the bonding surface side is flat. The P electrode 19P and the N electrode 19N are formed on the bonding surface side, and the surface thereof is a plane having substantially the same height as the surface of the protective film 17.

The surface of the P-side electrode 51 and the surface of the N-side electrode 52 on the side of the drive circuit board 50 are configured to be higher than the surface of the insulating film (insulating layer) 55. The P-electrode 19P and the N-electrode 19N are connected to the P-side electrode 51 and the N-side electrode 52 on the side of the drive circuit board 50, respectively.

Nano-sized metal nanoparticles 30 are arranged at the interface between the P-electrode 19P and the P-side electrode 51 and at the interface between the N-electrode 19N and the N-side electrode 52. The light-curing resin 31 is filled between the driving circuit board 50 and the micro light-emitting device 100. The P-electrode 19P and the P-side electrode 51, or the N-electrode 19N and the N-side electrode 52 are in contact via a large number of metal nanoparticles 30, and the driving circuit board 50 and the micro-light emitting element 100 are in close contact by shrinkage of the photo-curable resin, so that good electrical connection can be achieved. The metal nanoparticles 30 are made of palladium (Pd), gold (Au), platinum (Pt), nickel (Ni), aluminum (Al), or the like. The photocurable resin is a resin that undergoes polymerization reaction by irradiation with ultraviolet rays or near ultraviolet rays and is cured, and may be of an acrylate radical polymerization type such as epoxy resins, polyurethanes, acrylics, silicones, or of an epoxy cationic polymerization type.

In this way, since the P-electrode 19P and the P-side electrode 51, or the N-electrode 19N and the N-side electrode 52 are electrically connected by the metal nanoparticles 30, the surface layers of the P-electrode 19P and the N-electrode 19N and the surface layers of the P-side electrode 51 and the N-side electrode 52 may be made of different materials.

[ overview of the micro light-emitting element 100 ]

The micro light-emitting elements 100 are generally arranged in a two-dimensional array when viewed from the bonding surface side. As shown in fig. 2 (b), the P-electrode 19P is disposed in the central portion of the micro light-emitting element 100, and the N-electrode 19N is disposed in the divided region of the boundary portion. As shown in fig. 2 (a), a dividing groove 15 is present below the N electrode 19N. Fig. 1 is a cross section showing a-a in fig. 2 (b). Fig. 2 (a) shows the surface after the dividing groove 15 is formed (the state of fig. 3 (b)). Fig. 2 (b) shows the surface of the P electrode 19P and the N electrode 19N after the formation (state of fig. 3 (e)). However, the protective film 17 is omitted.

[ method for manufacturing micro light-emitting device 100 ]

Next, a manufacturing process of the micro light-emitting element 100 will be described with reference to fig. 3. As shown in fig. 3 (a), a compound semiconductor composed of an N-side layer 11, a light-emitting layer 12, and a P-side layer 13 is stacked in this order on a growth substrate 9, and a P-electrode layer 10 is deposited. The growth substrate 9 is, for example, a sapphire substrate. The growth substrate 9 is preferably a substrate transparent to ultraviolet rays and near ultraviolet rays.

Next, as shown in fig. 3 (b), the P electrode layer 10, the P-side layer 13, the light-emitting layer 12, and a part of the N-side layer 11 are etched to form dividing grooves 15. At this time, the portion including the light-emitting layer 12 becomes the mesa 16.

As shown in fig. 2 (a), the dividing grooves 15 are arranged at equal intervals in the longitudinal and lateral directions, and the mesa 16 has a quadrangular frustum shape. However, the shape of the mesa 16 is not limited to a quadrangular frustum, and may be a truncated cone or other polygonal frustum.

The sidewalls of the mesa 16 are preferably inclined at 45 degrees ± 10 degrees with respect to the plane in which the light-emitting layer 12 is formed. Of the light emitted from the light-emitting layer 12, the light advances in a direction parallel to the light-emitting layer 12 at the highest rate. Therefore, by reflecting such light in the direction of the light exit surface, the light extraction efficiency of the micro-light emitting element 100 can be improved.

When the side wall of the mesa 16 is vertical, light emitted in the horizontal direction is repeatedly reflected and is not emitted to the outside. If the inclination of the side wall of the mesa 16 increases from 45 degrees, the incident angle when the light is incident on the light exit surface becomes excessively large, and total reflection occurs on the light exit surface, or the light is not emitted to the outside.

Next, as shown in fig. 3 c, a protective film 17 is deposited, and the surface is polished by CMP (Chemical-Mechanical-Polishing) to be flat, the protective film 17 is an insulating film, for example, SiO ₂, SiN, SiON, or a laminated film of these films, and various film formation techniques such as a CVD method (Chemical Vapor Deposition method), a sputtering method, and coating can be used for forming the protective film 17.

Next, as shown in fig. 3 (d), P grooves (P-grooves) 18P are formed in the mesa 16, and N grooves (N-grooves) 18N are formed in the dividing grooves 15. The P groove 18P is hole-shaped and reaches the P electrode layer 10. The N-groove 18N is in the form of a groove (channel) extending in both the vertical and horizontal directions, and reaches the N-side layer 11 up to the bottom of the dividing groove 15.

Further, as shown in fig. 3 (e), the P-groove 18P and the N-groove 18N are filled with a metal film by a Damascene (damascone) method, and the P-electrode 19P and the N-electrode 19N are formed. The metal film is a combination of a barrier film of, for example, tantalum (Ta), tungsten (W), titanium nitride (TiN), or the like, and copper. Or a combination of gold or nickel, an aluminum alloy, or the like, and a corresponding barrier film. In the damascene method, a metal thin film is deposited on a substrate structure having a trench, and CMP polishing is performed, whereby the metal thin film can remain in the trench and the surface can be planarized.

Here, the damascene method is one of the metal wiring forming methods of LSI, and is a thin film forming technique combining a gold plating technique and a lift-off method. A damascene (damascone) method of filling a fine metal wiring layer in an insulating layer is called a damascene method. In a method focusing on a copper (Cu) wiring, a groove in a wiring shape is formed in an interlayer insulating film, and a metal such as copper is embedded. The second wiring method is a "single damascene wiring method", which is a method of forming a wiring groove after a metal connector plug is formed in a connection hole. The other method is called "dual damascene wiring method", which is a method of burying metal immediately after forming a connection hole and a wiring groove. The damascene method is used in combination with a CMP technique for planarizing the multilayer wiring layer. The process of fig. 3 is a single damascene method.

As described above, the P electrode 19P is disposed on the mesa 16, the N electrode 19N is disposed on the dividing groove 15, and the P electrode 19P and the N electrode 19N are disposed together on the surface (on the same plane) serving as the bonding surface, and the surface is made of the same material and is flat.

In the configuration of the present embodiment, the wiring layer is formed in one layer, and can be formed in a two-stage photolithography process of forming the dividing groove 15 and the mesa 16 and forming the P groove 18P and the N groove 18N. Therefore, the micro light-emitting element 100 can be manufactured in a very simple manufacturing process, and the equipment investment can be reduced, thereby significantly reducing the manufacturing cost.

[ method for manufacturing image display element 200 ]

Next, a manufacturing process of the image display device 200 will be described with reference to fig. 4. As shown in fig. 4 (a), the micro light-emitting element 100 is formed through the process of fig. 3. Next, as shown in fig. 4(b), metal nanoparticles 30 are arranged on the surface of the micro light-emitting element 100. The metal nanoparticles 30 are, for example, palladium.

Palladium nanoparticles can be formed by self-assembly using a block copolymer (see japanese patent 5875124), and one of the methods of self-assembly using a block copolymer is, for example, (i) a polystyrene-block-poly (2-vinylpyridine) (polystyrene-block-poly (2-vinylpyridine)) which is one of block copolymers is spin-coated to the micro light-emitting element 100, (ii) the spin-coated film is immersed in an aqueous solution of sodium tetrachloropalladate (Na ₂ PdCl ₄) to selectively precipitate palladium ions to 2-vinylpyridine (2-vinylpyridine) cores in the polystyrene-block-poly (2-vinylpyridine), (iii) the polystyrene-block-poly (2-vinylpyridine) is removed by plasma treatment.

Since the block copolymer for forming such metal nanoparticles 30 is extremely thin, it is difficult to form the block copolymer uniformly on a plane having large irregularities. Therefore, the electrode surface forming the metal nanoparticles 30 must be flat. In this embodiment, the surface of the micro light-emitting element 100 is formed flat, and this condition is satisfied.

Further, as shown in fig. 4 (c), the driver circuit board 50 is manufactured. The driver circuit board 50 is formed on a single crystal silicon substrate (wafer) by a normal CMOS (Complementary metal-oxide semiconductor) process, for example. The surface of the P-side electrode 51 and the surface of the N-side electrode 52 on the side of the driver circuit board 50 are formed higher than the surface of the insulating film 55. The wiring material constituting the P-side electrode 51 and the N-side electrode 52 is, for example, copper wiring or aluminum alloy. In the case of an aluminum alloy, since processing is performed by a dry etching technique, the structure of (c) of fig. 4 is easily formed. In the case of copper wiring, since the surface is flat because the wiring is formed by the damascene method, an additional step of digging an insulating film layer around the wiring is required. That is, as shown in fig. 4 (c), the convex portion of the surface of the driving circuit board 50 on the bonding surface side is an electrode constituting the P-side electrode 51 and the N-side electrode 52, and the concave portion is an exposed portion of the insulating film 55 between the electrodes.

Here, the driving circuit board 50 is preferably in a wafer state, and the micro light emitting devices 100 are preferably singulated in units of the image display device 200. Such an aggregate of the singulated micro light-emitting devices 100 is referred to as a light-emitting device unit (lighting unit) 101.

Next, as shown in fig. 4 (d), the light-emitting element unit 101 is disposed on a silicon substrate on which the driver circuit substrate 50 is arranged. At this stage, a gap 33 is made between the bonding surface side surface of the drive circuit substrate 50 and the bonding surface side surface of the light emitting element unit 101. Next, as shown in fig. 4 (e), the light-curable resin is injected into the interface, thereby filling the gap 33 with the light-curable resin 31. By connecting the light-emitting element units, the time for the light-curable resin to spread over the entire light-emitting element units can be shortened, and the bonding time can be shortened. Over time, the wafers can be bonded to each other.

In order to spread the light curable resin 31 between the drive circuit substrate 50 and the light emitting element unit 101, a space is required between the two. It is difficult to spread the photocurable resin 31 over a space defined by the height of the metal nanoparticles 30 in a short time. Since the bonding surface on the light-emitting element unit 101 side to which the metal nanoparticles 30 are attached is flat, it is necessary to provide irregularities on the driver circuit board 50 side in order to form a sufficient gap 33. This is because the P-side electrode 51 and the N-side electrode 52 have a convex shape.

Next, as shown in fig. 4 (f), light irradiation for curing the resin is performed from the growth substrate 9 side, and the light-curable resin 31 is cured. The growth substrate 9 is preferably light-transmissive for light curing because the growth substrate 9 cannot be light-cured without peeling the growth substrate 9, as in the case of a silicon substrate, when light is not transmitted. Since the driving circuit board 50 and the micro light-emitting element 100 are closely connected by photocuring, the growth substrate peeling process (fig. 4 (g)) to be performed next becomes easy. The growth substrate 9 can be peeled off by a laser peeling method or the like. After the growth substrate 9 is peeled off, the polymerization of the photocurable resin 31 is further advanced by heating, and the electrical connection can be further strengthened. At this time, since the growth substrate 9 is peeled off, the thermal stress generated by the difference in thermal expansion coefficient is greatly relaxed.

Even if the P-electrode 19P and the N-electrode 19N of the micro light-emitting element 100 are pressed against the P-side electrode 51 and the N-side electrode 52 of the driving circuit board 50 through the metal nanoparticles 30, the connection resistance cannot be sufficiently reduced. However, the photocurable resin 31 is cured by light irradiation without increasing the temperature, and a large shrinkage stress is generated, thereby reducing the connection resistance. Therefore, even when the driver circuit board 50 and the micro light-emitting element 100 have greatly different thermal expansion coefficients, the electrodes can be connected without being concerned about positional displacement.

[ Effect ]

Next, fig. 5 (a) shows a plan view of the image display device 200. A portion which emits light and actually displays an image within the image display element 200 is a pixel region 1. The description above mainly targets the pixel region 1.

The image display device 200 includes a dummy region 2, which is a non-light-emitting region, other than the pixel region 1, a plurality of external connection regions 3, a cut portion 4 for separating the image display device 200 into individual pieces, and the like. In the dummy region 2, circuits such as a row selection circuit, a column signal output circuit, an image processing circuit, and an input/output circuit are disposed on the drive circuit substrate 50, in addition to the micro light-emitting element drive circuit.

The light emitting element unit 101 is attached to cover the pixel region 1. In the light emitting element unit 101 in the pixel region 1, the micro light emitting element 100 shown in fig. 1 is disposed, but the dummy element 110 and the substrate-side dummy electrode 53 need to be disposed outside the pixel region 1. These structures are structures for reducing the amount of leakage of the light-curing resin 31 to the outside of the light-emitting element unit 101. For example, when the light-curing resin 31 is injected between the driver circuit board 50 and the light-emitting element unit 101 from the direction (a) in fig. 5 (a), if a large amount of the light-curing resin 31 leaks in the directions (B) and (C), it covers the external connection region 3 and is difficult to remove. On the other hand, as in the (D) direction, there is no problem with some leakage in the portion where the external connection region 3 is not present. Further, if the gap between the driver circuit board 50 and the light emitting element unit 101 is reduced, time is required for the entire photocurable resin 31 to be spread, which disadvantageously increases the process time. Here, the size of the gap needs to be adjusted in accordance with the direction in the outer peripheral portion of the pixel region 1. That is, the dummy region 2 is provided so that the side closer to the external connection region 3 has a small gap and the side farther from the external connection region 3 has a large gap.

In the present configuration, since the bonding surface of the light emitting element unit 101 is flat, the size of the gap is adjusted according to the length of the substrate-side dummy electrode 53 on the side of the driver circuit substrate 50. When the gap is small, the substrate-side dummy electrode 53 may be lengthened as shown in fig. 5 (b), and when the gap is large, the substrate-side dummy electrode 53 may be shortened as shown in fig. 5 (c). Here, the void is a portion filled with the photocurable resin 31. In this way, the substrate-side dummy electrode 53 for adjusting the size of the void is arranged on the outer periphery of the pixel region 1, and the dummy element 110 paired therewith is arranged, whereby the amount of leakage of the photocurable resin 31 can be controlled, and electrical connection in the external connection region 3 can be easily achieved. That is, in the present configuration, the amount of leakage of the light-curable resin from the pixel region close to the external connection region 3 can be reduced to be smaller than the amount of leakage of the light-curable resin from the pixel region close to the external connection region 3.

the dummy elements 110 on the outer periphery of the light-emitting element unit 101 can be used as temporary fixing regions for bonding the light-emitting element unit 101 to the driver circuit board 50. While the light-curable resin 31 is uniformly spread, it is not preferable to hold the light-emitting element unit 101 in a state of being pressed against the driver circuit board 50 to reduce the throughput of the adhesive. Here, for example, the light-emitting element unit 101 is fixed to the driver circuit board 50 in the dummy element 110 portion by injecting the light-curable resin 31 from the (B) side and the (C) side and irradiating light in a stage where the light penetrates under the dummy element 110. If the time required for the light-curing resin 31 to cover the dummy element 110 is shorter than the time required for the light-emitting element unit to permeate into the whole, the throughput of the adhesive can be improved. After the plurality of light emitting element units 101 are bonded, the light curable resin 31 is injected from the (a) side, and light irradiation is performed after the entire light emitting element units 101 are covered. These steps can be performed in parallel for the plurality of light-emitting element units 101, and therefore, high productivity can be achieved even if a little time is taken. In this case, the gap formed by the substrate-side dummy electrode 53 may be large on the (B) and (C) sides. When the light-curable resin 31 is injected from the (B) and (C) sides, a small amount of the light-curable resin needs to penetrate under the dummy element 110 in a short time, and therefore, a large void is preferable. When the photocurable resin 31 is injected from the (a) side, the injected resin is first cured to block the (B) and (C) sides, and thus the photocurable resin 31 does not leak to the (B) and (C) sides. On the other hand, on the (D) side, in order to make the penetration of the photocurable resin 31 uniform, for example, the gap formed by the substrate-side dummy electrode 53 in the central portion where the penetration speed is high can be made small, and the gap can be gradually widened toward the end portions on the (B) and (C) sides. That is, the dummy region 2 has a side with a small gap in the central portion and a large gap in the peripheral portion.

as described above, it is preferable that the dummy elements 110 for temporarily fixing the light emitting element unit 101, reducing the leakage of the light curable resin 31, and equalizing the penetration of the light permeable resin 31 are arranged on the outer periphery of the pixel region 1. Further, a substrate-side dummy electrode 53 for controlling a gap between the light-emitting element unit 101 and the drive circuit substrate 50 is preferably disposed on the outer periphery of the pixel region 1.

[ modification of the first embodiment ]

In the first embodiment, the micro light-emitting element 100 has a single-color display element. However, as shown in fig. 6A (a), the pixel 5 can be constituted by the blue sub-pixel 6, the red sub-pixel 7, and the green sub-pixel 8, and a full-color display element can be formed. Each sub-pixel has a separate micro light emitting element. Each sub-pixel may be formed of a micro light emitting element that emits blue light, red light, and green light, or each sub-pixel may be caused to emit red light or green light by combining a micro light emitting element that emits blue light with a wavelength conversion layer.

In fig. 6A (a), the periphery of each sub-pixel is surrounded by a dividing groove 15, and an N electrode 19N is disposed on the dividing groove 15. However, as shown in fig. 6A (b), the periphery of each sub-pixel is surrounded by the dividing groove 15, but the N electrode 19N may be disposed so as to cover the periphery of the pixel 5. In this case, since it is not necessary to dispose the N electrode 19N between the sub-pixels in the pixel 5, the division groove 15 between the sub-pixels can be narrowed. As a result, by increasing the width of the mesa 16 of the sub-pixel, the area of the light-emitting layer 12 can be increased, the current density flowing in the light-emitting layer 12 can be reduced, and the light-emitting efficiency can be improved.

Further, as shown in fig. 6A (c), the N electrodes 19N may be arranged only in one direction of the boundary of the pixel 5, or as shown in fig. 6A (d), the N electrodes 19N may be arranged in dots at the four corners of the pixel 5. Both have the same effect as in fig. 6A (b), and as the amount of arrangement of the N electrode 19N is reduced, the effect such as improvement in light emission efficiency is increased. In this way, the N electrode 19N is disposed on the dividing groove 15, but is not necessarily disposed over the entire area of the dividing groove 15. In order to make the light output variations uniform among the pixels 5, the wiring resistance needs to be uniform among the pixels 5, and therefore the N electrode 19N is preferably provided at least for each pixel 5. Therefore, as shown in fig. 6A (d), the N electrodes 19N are preferably arranged at the four corners of the pixel 5. The shape of the sub-pixel is not limited to the shape shown in fig. 6A (a), and may be, for example, the shape shown in fig. 6B (a).

In the above example, the P-electrode 19P is disposed in one position with respect to the micro-light emitting element 100, but is not limited to one position. For example, as shown in fig. 6B (B), two P-electrodes 119P1 and 219P2 may be disposed. By providing the P-electrode 119P1 and the P-electrode 219P2, when one is defective in conduction, a redundant function can be achieved instead of the other. In addition, the redundant function is a function of configuring and operating a backup device as a backup from ordinary times so as to continuously maintain the entire system even after a failure occurs, in case any failure occurs in a part of the system.

As shown in fig. 6B (c), the P electrode layer is also divided into the P electrode 110-1 and the P electrode 210-2, and the micro light-emitting element 100 can be substantially divided into two. When the P-electrode 119P1 side is defective, the use of the P-electrode 219P2 makes it possible to provide a redundant function to the micro-light-emitting element 100 in addition to defective conduction of the electrodes.

In order to realize this redundancy function, it is necessary to store the presence or absence of a failure for each micro light-emitting element 100 on the side of the drive circuit board 50, and to provide each micro light-emitting element 100 with a function of selecting a P electrode on the side which is normal during operation, which increases the cost.

In this case, since the pattern of the P electrode layer 10 is different from the pattern of the mesa 16, there is a possibility that the photolithography process is increased by one step. However, the cost increase due to the increase in the number of steps and the cost reduction due to the increase in the yield due to the redundancy function are balanced, and it is possible to determine which of the division of the P electrode layer and the division of the P electrode layer is prioritized. As described above, the P electrode is disposed on the mesa 16 having the light-emitting layer 12, but the number is not necessarily limited to one, and a plurality of P electrodes may be disposed.

As described above, not only miniaturization of pixels but also formation of sub-pixels for full-color formation, addition of redundant functions for yield improvement, and the like are required in various aspects in order to reduce the size of electrodes of the micro light-emitting element 100 and arrange them at high density. In order to miniaturize the electrode size, it is becoming increasingly difficult to form bumps on the electrodes. In contrast, the structure in which the self-assembled metal nanoparticles are arranged as in the present invention does not require a fear of short-circuiting between electrodes, and a large number of projections can be provided on each electrode.

[ second embodiment ]

other embodiments of the present invention will be described below.

As shown in fig. 7 (a), the image display element 200a of the present embodiment is different from the image display element 200 of the first embodiment in that the bonding surface on the side of the driving circuit substrate 50a is flat, the bonding surface side of the micro light emitting elements 100a is not flat but is separated into individual pieces, and that the P electrode 19P is provided on the bonding surface side of the micro light emitting elements 100a and the common N electrode 40 is provided on the light irradiation surface side.

[ outline of the image display element 200a ]

as shown in fig. 7 (a), the image display device 200a is configured such that the micro light-emitting device 100a emitting light is bonded to the drive circuit board 50a with a bonding surface (indicated by a thick dotted line). The micro light-emitting elements 100a are divided into the light-emitting layers 12 by the dividing grooves 15, and further, are completely divided into the individual micro light-emitting elements 100a by the separating grooves (separating grooves) 20. A P electrode 19P (second electrode) connected to the P-side layer 13 is disposed in the pixel region 1 in a region where the light-emitting layer 12 remains. As shown in fig. 7b, the common N-electrode 40 connected to the N-side layer 11 is connected to the N-electrode 19N (first electrode) outside the pixel region 1.

The surface of the P-side electrode 51 on the side of the driver circuit board 50a and the surface of the insulating film 55 are formed almost flat. The P electrode 19P is connected to the P-side electrode 51 on the drive circuit board 50a side.

Nano-sized metal nanoparticles 30 are arranged at the interface between the P-electrode 19P and the P-side electrode 51. The light-curing resin 31 is filled between the driver circuit board 50a and the micro light-emitting element 100 a. The P-electrode 19P and the P-side electrode 51, or the N-electrode 19N and the N-side electrode 52 are in contact via a large number of metal nanoparticles 30, and the driving circuit board 50a and the micro-light emitting element 100a are in close contact by shrinkage of the photo-curable resin, so that good electrical connection can be achieved.

In this configuration, since the bonding surface of the driver circuit board 50a is flat, the size of the gap 33 determines the electrode constituting the P electrode 19P, which is the convex portion of the surface of the micro light-emitting element 100a on the bonding surface side, and the exposed portion of the protective film 17, which is the concave portion, which is located in the dividing groove 15, according to the separation groove 20. That is, the concave portion is the dividing groove 15 portion. Specifically, the length of the P-electrode 19P on the light-emitting element unit 101a side and the width of the separation groove 20 are adjusted.

When the gap 33 is reduced, the P-electrode 19P of the dummy element 110a may be lengthened and the arrangement of the isolation groove 20 may be reduced as shown in fig. 7 (c). In contrast, when the gap is increased, the P electrode 19P may be shortened by closely arranging the separation grooves 20. That is, the length of the division groove 15 may be increased. In this manner, as in the first embodiment, the dummy element 110a is disposed in the outer peripheral portion of the pixel region 1, thereby temporarily fixing the light-emitting element unit 101 a. Further, by controlling the size of the void of the dummy element 110a, it is possible to reduce the leakage of the light-curable resin 31 and to make the penetration of the light-permeable resin 31 uniform, as in the first embodiment.

[ method for manufacturing micro light-emitting device 100a ]

Next, a manufacturing process of the micro light-emitting element 100a will be described with reference to fig. 8. A part of the dummy element 110a is shown, the left side is a pixel portion included therein, and the right side is an N electrode included therein. The manufacturing process of the micro light-emitting element 100a is the same as the steps (a), (b), and (c) of fig. 3, and thus, this portion is omitted. Therefore, as shown in fig. 8 (a), after the protective film 17 is deposited on the mesa 16, as shown in fig. 8 (b), a P groove 18P is formed on the mesa 16. The P groove 18P is hole-shaped and reaches the P electrode layer 10. In the dummy element region, the N groove 18N is formed at the bottom of the dividing portion 15 and reaches the N-side layer 11. Further, as shown in fig. 8 (c), the P-groove 18P and the N-groove 18N are filled with a metal film by a damascene method, and a P-electrode 19P and an N-electrode 19N are formed.

Next, as shown in fig. 8 (d), the surface of the protective film 17 is etched to expose the upper portions of the P electrode 19P and the N electrode 19N. The present etching may be dry etching or wet etching. As shown in fig. 8 (e), the protective film 17 and the compound semiconductor layer 14 are etched, thereby forming separation grooves 20. The separation grooves 20 preferably separate the micro light-emitting elements 100a into individual pieces. By the separation, light leakage between the micro light-emitting elements 100a can be reduced, and thus low contrast and color mixing of a display image due to the light leakage can be reduced.

As in the case of the micro light-emitting device 100a, a light-emitting device having only one electrode on a bonding surface needs to have the other electrode on a light irradiation surface after being bonded to the driver circuit board 50a, but has the following advantages: the fine pixel size can be formed to such an extent that there is no space on the bonding surface where the P electrode and the N electrode are arranged in parallel.

as shown in fig. 8 (e), the isolation trench 20 preferably reaches the growth substrate 9, but may stay in the compound semiconductor layer 14. Since light leakage is reduced as the residual film thickness of the compound semiconductor layer 14 is thinner, it is better to make the residual film thickness of the compound semiconductor layer 14 thinner from the viewpoint of reducing light leakage. However, since the light-emitting surface of the micro light-emitting element 100a can be made uniform and flat by leaving the thin compound semiconductor layer 14, it is advantageous in that the resistance of the common N electrode 40 can be reduced and the scattering of the emitted light can be reduced.

[ method for manufacturing image display element 200a ]

Next, a manufacturing process of the image display device 200a will be described with reference to fig. 9. As shown in fig. 9 (a), the micro light-emitting element 100a is formed through the process of fig. 8. Next, as shown in fig. 9 (b), a driver circuit board 50a is manufactured. The driver circuit board 50a is formed on a single crystal silicon substrate (wafer) by a normal CMOS (Complementary metal-oxide semiconductor) process, for example. The surface of the P-side electrode 51 and the surface of the N-side electrode 52 on the side of the drive circuit board 50a and the surface of the insulating film 55 are flat. The wiring material constituting the surface of the P-side electrode 51 and the N-side electrode 52 is, for example, a copper wiring. In the case of copper wiring, since the copper wiring is formed by the damascene method, the surface is flat, and the structure of fig. 9 (b) can be easily manufactured.

Next, as shown in fig. 9 (c), palladium nanoparticles are arranged on the surface of the driver circuit board 50a by the same method as in the first embodiment. In the first embodiment, as shown in fig. 4(b), the metal nanoparticles are disposed on the bonding surface of the micro light-emitting element 100, but in the present embodiment, the metal nanoparticles are disposed on the bonding surface of the driver circuit board 50 a.

here, the driving circuit board 50a is preferably in a wafer state, and the micro light emitting elements 100a are preferably singulated in units of the image display elements 200 a. The assembly of such singulated micro light-emitting elements 100a is referred to as a light-emitting element unit 101.

Next, as shown in fig. 9 (d), the light emitting element unit 101a is arranged on the silicon substrate on which the driver circuit board 50a is arranged, and as shown in fig. 9 (e), a light-curing resin is injected into the interface. The photocurable resin herein is a resin that undergoes a polymerization reaction and is cured by irradiation with ultraviolet rays or near ultraviolet rays. By connecting the light-emitting element units, the time for the light-curable resin to spread over the entire light-emitting element units can be shortened, and the bonding time can be shortened. After the lapse of time, bonding of wafers to each other can be performed.

Next, as shown in fig. 9 (f), light irradiation for curing the resin is performed from the growth substrate 9 side, and the light-curable resin 31 is cured. The growth substrate 9 is not light-curable unless the growth substrate 9 is peeled off, as in the case of a silicon substrate, and the growth substrate 9 preferably transmits light for curing the light-curable resin 31. Since the driving circuit board 50a and the micro light-emitting element 100a are closely connected by photocuring, the growth substrate peeling process (fig. 9 (g)) to be performed next becomes easy. The growth substrate 9 can be peeled off by a laser peeling method or the like. After the growth substrate 9 is peeled off, the polymerization of the photocurable resin 31 is further advanced by heating, and the electrical connection can be further strengthened. At this time, since the growth substrate 9 is peeled off, the thermal stress generated by the difference in thermal expansion coefficient is greatly relaxed.

Next, as shown in fig. 9 (h), the common N electrode 40 is formed on the light emitting surface side of the micro light emitting element 100 a. The common N electrode 40 is, for example, an ITO (Indium Tin Oxide) thin film, which is a transparent conductive film.

With this configuration, the same effects as those of the first embodiment can be obtained.

[ third embodiment ]

Another embodiment of the present invention will be described below.

As shown in fig. 10 (a), the present embodiment is different from the image display device 200 of the first embodiment in that in the image display device 200b of the present embodiment, the bonding surface on the side of the driver circuit board 50b and the bonding surface on the side of the micro light-emitting devices 100b are not flat, and the micro light-emitting devices 100b are separated into individual pieces.

[ outline of image display element 200b ]

As shown in fig. 10 (a), the image display device 200b is configured such that the micro light-emitting device 100b emitting light is bonded to the driving circuit board 50b at a bonding surface (indicated by a thick dotted line). The micro light-emitting element 100b is divided into the light-emitting layers 12 by the dividing grooves 15, and further into the individual micro light-emitting elements 100b by the separating grooves 20.

The P-electrode 19P and the N-electrode 19N are formed simultaneously in the same step as described later, and therefore have different shapes, sizes, and depths, but are made of wiring materials having the same structure as the material. The normal wiring material has a laminated structure composed of a plurality of layers of a barrier metal layer, a main conductive layer, a cap layer, and the like, but the P electrode 19P and the N electrode 19N have the same laminated structure. That is, the micro light-emitting element 100 side of the image display element 200b is constituted by a single wiring layer.

In the configuration of the present embodiment, the P-electrode 19P and the N-electrode 19N are formed of a metal material that is ohmically connected to the N-side layer 11, and therefore, ohmic connection to the P-side layer 13 can be made via the P-electrode layer 10. When the compound semiconductor 14 is a nitride semiconductor, the P electrode layer 10 is a good conductor such as ITO (Indium-Tin-Oxide) or palladium (Pd), which is a transparent electrode.

the dividing groove 15 of the micro-light emitting element 100b is covered with the protective film 17, but is not embedded in the protective film 17. The P-electrode 19P and the N-electrode 19N are formed on the bonding surface side, and the P-electrode 19P (second electrode) connected to the P-side layer 13 and the N-electrode 19N connected to the N-side layer 11 are arranged in the region where the light-emitting layer 12 of the micro light-emitting element 100b remains.

The surface of the P-side electrode 51 and the surface of the N-side electrode 52 on the side of the driver circuit board 50b are formed higher than the surface of the insulating film 55. The P-electrode 19P and the N-electrode 19N are connected to the P-side electrode 51 and the N-side electrode 52 on the side of the drive circuit board 50, respectively.

The interface of the two electrodes is arranged with nano-sized metal nanoparticles 30. The light-curing resin 31 is filled between the driving circuit board 50b and the micro light-emitting element 100 b. The P-electrode 19P and the P-side electrode 51, or the N-electrode 19N and the N-side electrode 52 are in contact via a large number of metal nanoparticles 30, and the driving circuit board 50b and the micro-light emitting element 100b are in close contact by shrinkage of the photo-curable resin, so that good electrical connection can be achieved.

In this way, since the P-electrode 19P and the P-side electrode 51, or the N-electrode 19N and the N-side electrode 52 are electrically connected by the metal nanoparticles 30, the surface layers of the P-electrode 19P and the N-electrode 19N and the surface layers of the P-side electrode 51 and the N-side electrode 52 may be made of different materials.

In the present configuration, since the electrode on the bonding surface of the driver circuit board 50b is formed higher than the insulating film 55, the substrate-side dummy electrode 53 can be disposed outside the pixel region 1, and the size of the void can be controlled. That is, the convex portion on the surface of the bonding surface of the driver circuit board 50b is an electrode such as the P-side electrode 51, the N-side electrode 52, and the dummy electrode 53, and the concave portion is an exposed portion of the insulating film 55. Further, the size of the gap may be adjusted according to the length of the P electrode 19P on the light emitting element unit 101b side and the width of the separation groove 20. That is, the convex portion of the bonding side surface on the light emitting element cell 101b side is the electrode of the P electrode 19P, N electrode 19N, and the concave portion is the dividing groove 15 portion including the dividing groove 20. When the gap is reduced, the P-electrode 19P of the dummy element 110b may be lengthened and the arrangement of the isolation groove 20 may be reduced as shown in fig. 10 (b). Meanwhile, a long substrate-side dummy electrode 53 may be arranged. In contrast, when the gap is increased, the P electrode 19P may be shortened by closely arranging the separation grooves 20. A short substrate-side dummy electrode 53 may be disposed. In this manner, as in the first embodiment, the dummy element 110b is disposed in the outer peripheral portion of the pixel region 1, thereby temporarily fixing the light-emitting element unit 101 b. Further, by controlling the size of the void of the dummy element 110b, it is possible to reduce the leakage of the light-curable resin 31 and to make the penetration of the light-permeable resin 31 uniform, as in the first embodiment.

[ method for manufacturing micro light-emitting device 100b ]

Next, a manufacturing process of the micro light-emitting element 100b will be described with reference to fig. 1. The manufacturing process of the micro light-emitting element 100b is the same as the steps (a) and (b) of fig. 3, and thus, this step is omitted. As shown in fig. 11 (a), the protective film 17b is deposited, but it is not necessary to completely fill the dividing groove 15 as in the first embodiment, and thus it is only necessary to be a thin film. Next, as shown in fig. 11 (b), a P contact hole 21P is formed in the mesa 16, and an N contact hole 21N is formed in the bottom of the dividing groove 15. The P contact hole 21P is formed in a hole shape and reaches the P electrode layer 10, and the N contact hole 21N is also formed in a hole shape and reaches the N-side layer 11. Further, as shown in fig. 11 (c), the P electrode 19bP and the N electrode 19bN are formed by a lift-off method. The electrode material is, for example, gold (Au) as a main wiring material, and nickel (Ni) or platinum (Pt) serving as an adhesion layer or a barrier layer is disposed under the electrode material.

Next, as shown in fig. 11(d), the protective film 17b of the dividing groove 15 and the compound semiconductor layer 14 are etched, thereby forming a separation groove 20. The separation grooves 20 preferably separate the micro light-emitting elements 100b into individual pieces. The function of the separation tank 20 is the same as that of the second embodiment.

This manufacturing process is similar to the conventional LED manufacturing process, is simple, and is effective when the micro light-emitting element 100b is relatively large.

[ method for manufacturing image display element 200b ]

Next, a manufacturing process of the image display device 200b will be described with reference to fig. 12. Further, as shown in fig. 12 (a), a driver circuit board 50b is manufactured. The driver circuit board 50b is formed on a single crystal silicon substrate (wafer) by a normal CMOS (Complementary metal-oxide semiconductor) process, for example. The surface of the P-side electrode 51 and the surface of the N-side electrode 52 on the side of the driver circuit board 50b are formed higher than the surface of the insulating film 55. The wiring material constituting the surface of the P-side electrode 51 and the N-side electrode 52 is, for example, an aluminum alloy wiring.

Since it is difficult to directly form metal nanoparticles on a surface of one of the substrates having such irregularities, it is necessary to form metal nanoparticles while temporarily flattening the surface, and then remove the metal nanoparticles except for the electrode portion.

First, as shown in fig. 12 (b), the planarization layer 32 is formed between the surface of the P-side electrode 51 and the N-side electrode 52. Next, as shown in fig. 12 (c), palladium nanoparticles are aligned by the same method as in the first embodiment. After that, as shown in fig. 12 (d), the planarization layer 32 is removed. The planarizing layer 32 is, for example, a resin layer, and can be planarized by coating or etch-back and removed by dissolving with a solvent.

Here, the driving circuit board 50b is preferably in a wafer state, and the micro light emitting elements 100b are preferably singulated in units of the image display elements 200 b. The aggregate of the monolithic micro light-emitting elements 100b is a light-emitting element unit 101 b.

Next, as shown in fig. 12 (e), the light emitting element unit 101b is arranged on the silicon substrate on which the driver circuit board 50b is arranged, and as shown in fig. 12 (f), a light-curing resin is injected into the interface.

Next, as shown in fig. 12 (g), light irradiation for curing the resin is performed from the growth substrate 9 side, and the light-curable resin 31 is cured. When the growth substrate 9 does not transmit light, as in the case of a silicon substrate, if the growth substrate 9 is not peeled off, photocuring cannot be performed, and the growth substrate 9 preferably transmits the cured light. Since the driving circuit board 50b and the micro light-emitting element 100b are closely connected by photocuring, the growth substrate separation step (fig. 12 (h)) to be performed next becomes easy. The growth substrate 9 can be peeled off by a laser peeling method or the like. After the growth substrate 9 is peeled off, the polymerization of the photocurable resin 31 is further advanced by heating, and the electrical connection can be further strengthened. At this time, since the growth substrate 9 is peeled off, the thermal stress generated by the difference in thermal expansion coefficient is greatly relaxed.

with this configuration, the same effects as those of the first embodiment can be obtained.

[ fourth embodiment ]

Another embodiment of the present invention will be described below.

as shown in fig. 13 (c), the present embodiment is different from the micro light-Emitting element 100 of the first embodiment in that the micro light-Emitting element 100c of the present embodiment is a VCSEL (vertical cavity Surface Emitting LASER) micro LASER element. Compared with a micro LED element, the light emitting wavelength spectrum is narrow, and display with high directivity can be performed.

[ method for manufacturing micro light-emitting device 100c ]

Next, an example of a method for manufacturing the micro light-emitting element 100c will be described with reference to fig. 13. Fig. 13 (a) to 13 (e) are sectional views each showing a manufacturing process of the micro light-emitting element 100 c.

As shown in fig. 13 (a), the compound semiconductor 14c is formed by sequentially depositing the first reflective layer 42, the N-side layer 11c, the light-emitting layer 12, and the P-side layer 13 on the growth substrate 9 in this order. The first reflective layer 42 is a dbr (distributed Bragg reflector) that reflects light of an oscillation wavelength. In the case of using a nitride semiconductor to emit blue light, the first reflective layer 42 can be formed by overlapping a pair of a plurality of AlxGa (1-x) N layers and GaN layers. For example, a total thickness of 93nm GaN/AlGaN pairs including 20 GaN layers 46nm thick and an AlxGa (1-x) N layer 47nm thick is about 1.8 μm.

On the compound semiconductor layer 14c, a transparent electrode layer 44 and a second reflective layer 45 are deposited, the transparent electrode layer 44 is an electrode layer of ITO (indium tin oxide) or the like, and has a thickness of about 50nm to 600nm, the second reflective layer 45 is a dbr composed of a dielectric multilayer film, for example, a pair of a TiO ₂ thin film (thickness 36nm) and a SiO ₂ thin film (thickness 77nm) is 10 layers, and the total thickness is about 1.1 μm, and the reflectance of the second reflective layer 45 with respect to blue light is higher than that of the first reflective layer 42.

As shown in fig. 13 (b), after the second reflective layer 45 is stacked, the dividing groove 15 is formed by a photolithography technique and a dry etching technique. The dividing groove 15 etches part of the second reflective layer 45, the transparent electrode 44, the P-side layer 13, the light-emitting layer 12, and the N-side layer 11. The side surfaces of the dividing groove 15 do not need to be largely inclined as in the first embodiment. This is because the laser element does not emit light in the horizontal direction, and therefore does not need to be reflected in the vertical direction. Next, as shown in fig. 13 (c), the dividing groove 15 is filled with a protective film 17 to make the surface flat. Further, as shown in fig. 13 (d), N-grooves 18N and P-grooves 18P are formed. The N-groove 18N etches the protective film 17 to reach the N-side layer 11c at the bottom of the dividing groove 15. The P groove 18P is formed by etching the protective film 17 and the second reflective layer 45 to reach the transparent electrode 44. Next, as shown in fig. 13 (e), P electrode 19cP and N electrode 19N are formed. Here, the P-electrode 19cP is formed on the light-emitting layer, but the region where the light-emitting layer 12 exists is preferably arranged not at the center but at the outer periphery. This is because the P electrode 19cP penetrates the second reflective layer 45, and hence light emission of the laser element is inhibited.

As described above, the P electrode 19cP is disposed on the light-emitting layer 12, the N electrode 19N is disposed on the dividing groove 15, and the P electrode 19cP and the N electrode 19N are disposed on the surface which becomes the bonding surface, and the surface is made of the same material and is flat. By combining the micro light-emitting element 100c with a driver circuit board (having the same configuration as the driver circuit board 50 of the first embodiment), an image display element can be configured in the same manner as in the first embodiment. Further, the same effects as those of the first embodiment can be achieved. Further, the present embodiment can achieve additional effects such as narrowing the spectral width of the emission wavelength and increasing the directivity, compared to the first embodiment.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention. Further, new technical features can be formed by combining the technical methods disclosed in the respective embodiments.

Description of the reference numerals

1 pixel region

2 dummy region

3 external connection area

4 cutting part

5 pixels

6 blue sub-pixel

7 red sub-pixel

8 green sub-pixel

9 growth substrate

10P electrode layer

11. 11c N side layer

12 light emitting layer

13P side layer

14. 14c compound semiconductor

15 dividing groove

16 table top

17. 17b protective film

18P P groove

18N N groove

19P, 19P1, 19P2, 19bP, 19cP electrode

19N, 19bN electrode

20 separating tank

21P P contact hole

21N N contact hole

30 metal nanoparticles

31 photo-curable resin

32 planarization layer

40 common N electrode

42 first reflective layer

44 transparent electrode layer

45 second reflective layer

50. 50a, 50b drive circuit board

51P side electrode

52N side electrode

53-substrate dummy electrode

55 insulating film

100. 100a, 100b, 100c micro light emitting element

101. 101a, 101b light emitting element unit

110. 110a, dummy element

200. 200a, 200b image display element