JP7423706B2 - micro light emitting diode display device - Google Patents

Description

TECHNICAL FIELD This disclosure relates to display devices, and more particularly to micro light emitting diode displays.

Pixels of a micro-light-emitting diode display can be formed by placing semiconductor light-emitting mesas on a semiconductor connection layer. Each of the semiconductor light emitting mesas corresponds to a subpixel and is arranged in an array on the semiconductor connection layer. In addition to being a connection layer, the semiconductor connection layer can also function as a common electrode for each light emitting mesa, and is electrically connected to the circuit board via the bonding metal layer.

However, the resistance value of the semiconductor connection layer is higher than the resistance value of the conductor. Emitting mesas farther away from a common ground point have fewer electron-hole pairs recombining. On the other hand, the number of electron-hole pairs that recombine increases in the light-emitting mesa that is closer to the common ground point. Therefore, the brightness of the micro-light emitting diode display may be non-uniform.

The present disclosure provides a micro light emitting diode display device with uniform emission brightness.

According to one embodiment of the present disclosure, a micro light emitting diode display is provided that includes a circuit board, an epitaxial structure, and a conductive layer. The epitaxy structure is electrically connected to the circuit board and includes a connection layer and a plurality of light emitting mesas. The light-emitting mesa is disposed on the connection layer, the thickness of the connection layer being less than the thickness of the light-emission mesa, and the connection layer having a first surface exposed by the light-emission mesa and a second surface opposite the first surface. Has a surface. A conductive layer is disposed on the second surface of the connection layer, exposing a plurality of sub-regions of the second surface, and a vertical projection of the conductive layer onto the connection layer is a vertical projection of the first surface onto the connection layer. overlap.

According to another embodiment of the present disclosure, a micro light emitting diode display is provided that includes a circuit board, an epitaxial structure, and a transparent conductive layer. The epitaxy structure is electrically connected to the circuit board and includes a connection layer and a plurality of light emitting mesas. A light emitting mesa is disposed on the connection layer, the connection layer having a first surface exposed by the light emitting mesa and a second surface opposite the first surface. A transparent conductive layer is disposed on the second surface of the connection layer, and the transparent conductive layer completely covers the second surface.

Based on the above, in the micro light emitting diode display provided by the embodiments of the present disclosure, a conductive layer is disposed on the connection layer of the epitaxial structure. Since the resistance value of the conductive layer is smaller than the resistance value of the connection layer, the current of the circuit board can be transmitted more uniformly through the conductive layer. In this case, the same potential difference can drive the same number of recombining electron-hole pairs in the light-emitting mesas at different distances from a common ground point, which leads to non-uniform brightness in the micro-light emitting diode display. can be prevented from becoming. Furthermore, as resolution requirements increase, the arrangement of light-emitting mesas (sub-pixels) becomes denser. In contrast to the conventional situation where the conductive layer is disposed on the first surface of the connection layer, the conductive layer of the present disclosure is disposed on the second surface, which significantly improves yield.

In order to make the above features and advantages of the present disclosure understandable, some embodiments will be described in detail below with reference to the drawings.

1 shows a top schematic view of a micro light emitting diode display according to an embodiment of the present disclosure; FIG. 1A shows a cross-sectional schematic view along line II' shown in FIG. 1A; FIG. 1 shows a top schematic view of a micro light emitting diode display according to an embodiment of the present disclosure; FIG. 2A shows a cross-sectional schematic view along the line II-II' shown in FIG. 2A; FIG. 1 is a cross-sectional schematic diagram of a micro light emitting diode display according to an embodiment of the present disclosure; FIG. 1 is a cross-sectional schematic diagram of a micro light emitting diode display according to an embodiment of the present disclosure; FIG. 1 is a cross-sectional schematic diagram of a micro light emitting diode display according to an embodiment of the present disclosure; FIG.

Mode for carrying out the invention

Referring to FIGS. 1A and 1B, the micro light emitting diode display device 1 has a display area A1 and a non-display area A2, and includes a circuit board C1, an epitaxial structure ES, and a conductive layer 30. The display area A1 refers to an area where a plurality of display sub-pixels PX are arranged, and the non-display area A2 is arranged at least partially around the display area A1, and a plurality of driving elements (not shown) are arranged. It can be an area. Each of the display sub-pixels PX has a light emitting mesa 20 which provides the image light of the micro light emitting diode display 1.

The epitaxial structure ES includes a connection layer 10 and a plurality of light emitting mesas 20. As shown in FIG. 1B, a plurality of light emitting mesas 20 respectively corresponding to a plurality of display sub-pixels PX are disposed on the connection layer 10, and each of the light emitting mesas 20 includes a first type semiconductor layer 201, a first type semiconductor layer 201, 2 type semiconductor layer 202 and a light emitting layer 203, the light emitting layer 203 is a multiple quantum well (MQW). The connection layer 10 is arranged on a plane parallel to the plane formed by the first direction D1 and the second direction D2, and connects a first surface 101 exposed by the light emitting mesa 20 and a first surface 101 of the first surface 101. and an opposite second surface 102.

According to an embodiment of the present disclosure, the connection layer 10 is an n-type semiconductor, the first type semiconductor layer 201 is an n-type semiconductor, and the second type semiconductor layer 202 is a p-type semiconductor. However, the present disclosure is not limited thereto. In another embodiment of the present disclosure, the connection layer 10 is a p-type semiconductor, the first type semiconductor layer 201 is a p-type semiconductor, and the second type semiconductor layer 202 is an n-type semiconductor. In particular, the connection layer 10 and the first type semiconductor layer 201 may be formed integrally. That is, the two layers may be the same layer. For example, by forming a plurality of separated first type semiconductor layers 201 and a continuous connection layer 10 by an etching process, the yield of material transfer to the circuit board C1 can be improved, and power consumption can be reduced. The connection layer 10 can also be used as a common electrode for this purpose.

The circuit board C1 may be, for example, a complementary metal oxide semiconductor (CMOS) substrate, a liquid crystal on silicon (LCOS) substrate, a thin film transistor (TFT) substrate, or other substrate with operational circuitry. but not limited to. As shown in FIG. 1B, the epitaxial structure ES is electrically connected to the circuit board C1 via the bonding metal layer 120, the bonding metal layer 130, the bonding metal layer 140, and the bonding metal layer 150. and bonding metal layer 150 are a common ground point. When a voltage is applied to the bonding metal layer 120 via the circuit board C1 and a potential difference is generated between the bonding metal layer 120 and the common ground point, a current is generated due to the potential difference, and the bonding metal layer 120 to which the voltage is applied is generated. Recombination of electron-hole pairs occurs in the connected light-emitting mesa 20, thereby generating light. The light emitted by the light emitting mesa 20 exits the micro light emitting diode display 1 along a direction substantially parallel to the third direction D3 and enters the user's eyes. Here, the first direction D1, the second direction D2, and the third direction D3 are perpendicular to each other.

Since the connection layer 10 functioning as a common electrode is a semiconductor, the resistance value of the connection layer 10 is higher than the resistance value of the conductor. When a predetermined potential difference is applied between the common ground point and the bonding metal layer 120 far from the common ground point, the number of recombined electron-hole pairs in the corresponding light emitting mesa 20 will be reduced. If the same potential difference is applied to the common ground point and the bonding metal layer 120 close to the common ground point, the number of recombining electron-hole pairs in the corresponding light emitting mesa 20 will be large. In order to avoid the above situation, the conductive layer 30 is arranged on the second surface 102 of the connection layer 10, and the thickness of the connection layer 10 in the third direction D3 is made thinner than the thickness of the light emitting mesa 20. By utilizing a conductive layer 30 having a low resistance to assist in the transmission of current, the current can be distributed evenly. Even if the same potential difference is applied to the common ground point and the bonding metal layer 120 far from the common ground point, the number of recombined electron-hole pairs in the corresponding light emitting mesa 20 will not decrease. The light emitted from the light emitting mesa 20 is prevented from being reflected inside the connection layer 10. Light loss is avoided. Therefore, the light emitting mesas 20 of the micro light emitting diode display 1 can have the same brightness when the same potential difference is applied, and the micro light emitting diode display 1 can have good brightness uniformity.

The larger the area of the conductive layer 30, the more uniformly the current is distributed and the brightness uniformity of the micro-light emitting diode display device 1 is improved. In one embodiment, if the vertical projection of the conductive layer 30 onto the connection layer 10 is the first projection and the vertical projection of the first surface 101 onto the connection layer 10 is the second projection, the first projection The area of the overlapping portion of the second projection is 0.5 times or more the area of the second projection. In one embodiment, the vertical projection (i.e., the second projection) of the first surface 101 onto the connection layer 10 is completely within the vertical projection (i.e., the first projection) of the conductive layer 30 onto the connection layer 10. include. In another embodiment, the vertical projection (i.e., the second projection) of the first surface 101 onto the connection layer 10 is within the vertical projection (i.e., the first projection) of the conductive layer 30 onto the connection layer 10. Completely contained, the area of the overlapping portion of the first and second projections is equal to the area of the second projection.

In this embodiment, conductive layer 30 is an opaque, highly conductive material such as gold, titanium, aluminum, silver, platinum, and alloys thereof. Accordingly, conductive layer 30 is configured to expose a plurality of subareas 102S of second surface 102, each subarea 102S corresponding to a light emitting mesa 20. Specifically, as shown in FIG. 1B, the vertical projections of the subareas 102S onto the connection layer 10 overlap with the vertical projections of the light-emitting mesas 20 onto the connection layer 10, respectively, so that each of the light-emitting mesas 20 The light emitted by can pass through the corresponding sub-area 102S and then exit from the micro-light emitting diode display device 1. Although the vertical projection of conductive layer 30 onto connection layer 10 overlaps the vertical projection of first surface 101 onto connection layer 10 and does not overlap the vertical projection of light emitting mesa 20 onto connection layer 10, this disclosure but not limited to. In one embodiment of the present disclosure, the vertical projection of conductive layer 30 onto connection layer 10 partially overlaps the vertical projection of at least a portion of light emitting mesa 20 onto connection layer 10 . In other words, the area of the vertical projection of at least a portion of the subarea 102S onto the connection layer 10 is smaller than the area of the vertical projection of the corresponding light emitting mesa 20 onto the connection layer 10. In such a configuration, the light emitted by the light emitting mesa 20 is further restricted by the conductive layer 30 and the light travels in a more concentrated direction, thereby avoiding crosstalk between display sub-pixels PX. Preferably, the ratio between the vertical projection of at least a portion of the subarea 102S onto the connection layer 10 and the vertical projection of the corresponding light emitting mesa 20 onto the connection layer 10 is between 0.5 and 1; If the ratio is less than 0.5, the light extraction rate may be insufficient.

Furthermore, since the conductive layer 30 is an opaque highly conductive material, the thickness of the conductive layer 30 is adjusted to be less than or equal to the thickness of the epitaxial structure ES so as to reduce the amount of light absorbed by the conductive layer 30. It is composed of The total area of the conductive layers 30 disposed in the display area A1 is larger than the total area of the conductive layers 30 disposed in the non-display area A2 so that the current is transmitted more uniformly in the conductive layer 30 in the display area A1. Please also note that it is large. Each of the light emitting mesas 20 has the same brightness when the same potential difference is applied to it.

In this embodiment, the micro light emitting diode display device 1 further includes a semiconductor pad 40, and the semiconductor pad 40 and the bonding metal layers 140, 150, which function as a common ground point, are all located in the non-display area A2, and the light emitting diode display device 1 further includes a semiconductor pad 40. 20 is arranged in the display area A1.

Semiconductor pad 40 and light emitting mesa 20 may be manufactured in the same process and may have similar structures. Since the upper surface of each light emitting mesa 20 and the upper surface of the semiconductor pad 40 on the side away from the connection layer 10 are on the same plane, the bonding metal layer 150 and the bonding metal layer 130 on the circuit board C1 are connected to the bonding metal layer 140 and the bonding metal layer The yield of the process of bonding each layer 120 can be improved. Furthermore, the bonding metal layer 140 has an epitaxial section 140E, which allows the bonding metal layer 140 to be electrically connected between the connection layer 10 and the bonding metal layer 150.

Other embodiments of the disclosure are described below in order to fully describe the various embodiments of the disclosure. The following embodiments use some of the reference numbers and content of the above embodiments, the same reference numbers are used to indicate the same or similar elements, and the description of the same technical content is omitted. Please note. For explanations of omitted parts, the above embodiments can be referred to and will not be described in the following embodiments.

Referring to FIGS. 2A and 2B, the micro light emitting diode display device 2 has a display area A1 and a non-display area A2, and includes a circuit board C1, an epitaxial structure ES, and a conductive layer 30A. The plurality of light emitting mesas 20 are grouped into a plurality of light emitting mesa groups 20G in units of four light emitting mesas 20, and the conductive layer 30A is configured to expose the plurality of subareas 102G of the second surface 102, Each subarea 102G corresponds to a light emitting mesa group 20G. However, the present disclosure is not limited thereto. In some embodiments, the light emitting mesas 20 of the micro light emitting diode display 2 are grouped into a plurality of light emitting mesa groups 20G in units of at least three light emitting mesas 20. Thereafter, when color conversion elements (not shown, e.g. quantum dots) are disposed on the second surface 102 corresponding to the at least three light emitting mesas 20, the at least three light emitting mesas 20 are configured to emit red light, e.g. Green light and blue light can be emitted to form a full color display.

Similar to the micro-light-emitting diode display device 1, the total area of the conductive layers 30A arranged in the display area A1 of the micro-light-emitting diode display device 2 is larger than the total area of the conductive layers 30A arranged in the non-display area A2. , current can be uniformly transmitted by the conductive layer 30A in the display area A1. Each of the light emitting mesas 20 has the same brightness when the same potential difference is applied to it.

Referring to FIG. 3, the micro light emitting diode display device 3 has a display area and a non-display area, and includes a circuit board C1, an epitaxial structure ES, a conductive layer 30B, a conductive layer 50, and an insulating layer 220. The conductive layer 30B includes a conductive layer 30B1 arranged in the display area and a conductive layer 30B2 arranged in the non-display area.

The width of the conductive layer 30B1 decreases in the direction away from the second surface 102 (ie, along the positive direction of the third direction D3), and the conductive layer 30B1 presents a view that is wide at the bottom and narrow at the top. Since the cross-sectional view of the conductive layer 30B1 shown in FIG. 3 has a conical shape, the light emitted by the corresponding light emitting mesa 20 can be reflected and concentrated more toward the center. Thereafter, when a color conversion element (not shown, for example, a quantum dot) is placed on the second surface 102 corresponding to the light emitting mesa 20, the groove G formed in the conductive layer 30B1 Provides a housing space for color conversion elements with greater machining tolerances. In other embodiments, the width of conductive layer 30B1 decreases in a direction away from second surface 102, and conductive layer 30B1 has a trapezoidal shape in cross-section.

The conductive layer 30B2 in the non-display area is also arranged in the through hole 10H penetrating the connection layer 10, and is electrically connected to the bonding metal layer 140, the bonding metal layer 150, and the circuit board C1. The current from the circuit board C1 is sequentially transmitted to the bonding metal layer 150, the bonding metal layer 140, and the conductive layer 30B2 in the through hole 10H, and is transferred onto the second surface 102 without passing through the connection layer 10 having a higher resistance. The conductive layer 30B2 and the conductive layer 30B1 are reached. Since the total area of the conductive layer 30B1 disposed in the display area is larger than the total area of the conductive layer 30B2 disposed in the non-display area, it is ensured that the current is transmitted more uniformly in the conductive layer 30B1. Each of the light emitting mesas 20 has the same brightness when the same potential difference is applied to it.

The micro-light emitting diode display device 3 of this embodiment further comprises another conductive layer 50 arranged on the first surface 101 of the connection layer 10. In other words, the conductive layer 50 is arranged between the light emitting mesas 20. The conductive layer 50 is also configured to conduct current from the circuit board C1, and an insulating layer 220 is disposed between the conductive layer 50 and the light emitting mesa 20.

Referring to FIG. 4, the micro light emitting diode display device 4 includes a circuit board C1, an epitaxial structure ES1, and a conductive layer 30C.

The epitaxial structure ES1 includes a connection layer 10A and a plurality of light emitting mesas 20. The connection layer 10A can be formed by epitaxial growth on a patterned epitaxial substrate, and includes a plurality of three-dimensional patterns 102P, the three-dimensional patterns 102P being arranged on the second surface 102A. That is, the connection layer 10A is different from the connection layer 10 shown in FIG. 1B in which the second surface 102 is flat, and the second surface 102A of the connection layer 10A has a plurality of three-dimensional patterns 102P. The conductive layer 30C is arranged within the plurality of grooves G' of the three-dimensional pattern 102P. In such a situation, the contact area between the conductive layer 30C disposed on the three-dimensional pattern 102P and the second surface 102A is the same as that between the conductive layer 30 and the second surface 102 shown in FIG. 1B. , the bonding yield between the connection layer 10A and the conductive layer 30C is improved, and the current transmission efficiency from the circuit board C1 is improved.

The above conductive layer 30, conductive layer 30A, conductive layer 30B, and conductive layer 30C are opaque conductive layers. However, the present disclosure is not limited thereto. In some embodiments, conductive layer 30, conductive layer 30A, conductive layer 30B, and conductive layer 30C are transparent conductive layers.

Referring to FIG. 5, the micro light emitting diode display device 5 includes a circuit board C1, an epitaxial structure ES, and a transparent conductive layer 30T. The transparent conductive layer 30T is disposed on the second surface 102 of the connection layer 10 and completely covers the second surface 102. The material of the transparent conductive layer 30T may be a metal oxide material such as indium tin oxide (ITO) or zinc (ZnO). Since light can pass through the transparent conductive layer 30T, there is no need to expose multiple sub-regions of the second surface as with various opaque conductive layers in previous embodiments; The contact area with the second surface is maximized and the efficiency of current transfer from the circuit board C1 is greatly improved.

In summary, in the micro-light emitting diode display provided by embodiments of the present disclosure, a conductive layer is disposed on a connecting layer of an epitaxial structure. Since the resistance of the conductive layer is smaller than the resistance of the connection layer, current from the circuit board can be transferred into the conductive layer. In this case, even if the emitting mesas are at different distances from a common ground point, the same potential difference can drive the same number of electron-hole pairs to recombine in their emitting mesas, which leads to micro-emitting Non-uniform brightness of diode display devices can be avoided. Moreover, a manufacturing process in which the conductive layer is placed on the second surface of the connection layer, as opposed to the case in which the conductive layer is placed on the first surface of the connection layer, has a significantly higher yield.

The micro-light emitting diode display device of the present disclosure can have uniform emission brightness while having higher yield.

1, 2, 3, 4, 5: Micro light emitting diode display device 10, 10A: Connection layer 10H: Through hole 20: Light emitting mesa 20G: Light emitting mesa group 30, 30A, 30B, 30B1, 30B2, 50, 30C, 30T: Conductive layer 40: Semiconductor pad 101: First surface 102, 102A: Second surface 102P: Three-dimensional pattern 102S, 102G: Subarea 120, 130, 140, 150: Bonding metal layer 140E: Epitaxial section 201: First type semiconductor layer 202: second type semiconductor layer 203: light emitting layer 220: insulating layer A1: display area A2: non-display area
C1: Circuit board D1: First direction D2: Second direction D3: Third direction ES, ES1: Epitaxial structure G, G': Groove PX: Display subpixel

Claims (7)

a circuit board;
an epitaxial structure electrically connected to the circuit board,
a connection layer;
a plurality of light-emitting mesas disposed on the connection layer, wherein the connection layer has a thickness thinner than the light-emission mesa, and the connection layer contacts a first surface exposed by the light-emission mesa. an epitaxial structure having a second surface opposite the first surface;
a first conductive layer disposed on the second surface of the connection layer, wherein a vertical projection of the first conductive layer onto the connection layer is a vertical projection of the first surface onto the connection layer; a first conductive layer overlapping the projection;
The micro light emitting diode display device, wherein the thickness of the first conductive layer is less than or equal to the thickness of the epitaxial structure. The vertical projection of the first conductive layer onto the connection layer is a first projection, the vertical projection of the first surface onto the connection layer is a second projection, and the first projection and the The micro light emitting diode display device according to claim 1, wherein the area of the overlapping portion of the second projection is 0.5 times or more the area of the second projection. 2. The micro light emitting diode display of claim 1, wherein the first conductive layer exposes a plurality of subareas of the second surface, each subarea corresponding to the light emitting mesa. 4. The light emitting mesa is grouped into a plurality of light emitting mesa groups, the first conductive layer exposing a plurality of subareas of the second surface, each subarea corresponding to the light emitting mesa group. 1. The micro light emitting diode display device according to 1. The micro light emitting diode display device according to claim 1, wherein the first conductive layer is disposed in a through hole penetrating the connection layer and electrically connected to the circuit board. The micro light emitting diode display of claim 1, further comprising a second conductive layer disposed on the first surface of the connection layer. a circuit board;
an epitaxial structure electrically connected to the circuit board, the epitaxial structure comprising a connection layer and a plurality of light emitting mesas disposed on the connection layer, wherein the connection layer has a first structure exposed by the light emitting mesas; an epitaxial structure having a surface and a second surface opposite the first surface;
a transparent conductive layer disposed on the second surface of the connection layer and completely covering the second surface,
A micro light emitting diode display device, wherein the thickness of the transparent conductive layer is less than or equal to the thickness of the epitaxial structure.