Micro-LED and display device

Abstract

The present invention discloses a micro light-emitting diode and a display device therefor, comprising a semiconductor layer sequence, wherein the semiconductor layer sequence comprises a rear side and a front side, wherein on the front side a semiconductor layer of a first type and a semiconductor layer of a second type are arranged in sequence and an active layer therebetween, wherein the rear side of the semiconductor layer sequence comprises a groove, wherein the groove extends through the semiconductor layer of the second type and the active layer to expose the semiconductor layer of the first type, wherein the rear side of the semiconductor layer sequence comprises a first mesa in the groove, a second mesa on the semiconductor layer of the second type and a groove sidewall arranged therebetween, wherein on the rear side of the semiconductor layer sequence there are a first metal electrode electrically connected to the semiconductor layer of the first type, and a second metal electrode,which is electrically connected to the second type semiconductor layer, wherein the first metal electrode and the second metal electrode are used to bond to an external power source, and wherein an electrode hole of the second metal electrode is provided on the side of the surface facing away from the short edge of the chip, thereby increasing the continuity of the bonding area of ​​the electrodes and improving the product yield.

Description

Technical area

[0001] The present invention relates to the field of semiconductor manufacturing, in particular micro light-emitting diodes and display devices. Technology in the background

[0002] Micro-LEDs (mLEDs) are the next generation of display light sources currently being intensively researched. They feature low power consumption, high brightness, ultra-high resolution and color saturation, fast response time, low energy consumption, and a long lifetime. Furthermore, their power consumption is approximately 10% of that of LCDs and 50% of that of OLEDs. Compared with the same self-luminous OLED, they exhibit several times higher brightness and higher pixel density. Due to these obvious advantages, mLEDs are expected to replace current OLEDs and LCDs and become the next generation of display light sources. However, mLEDs are not yet available for mass production due to many technical difficulties that still need to be overcome. One of the key technical challenges is improving the process yield for micrometer-sized core particles. Content of the invention

[0003] In order to improve the process yield of a micro light-emitting diode, such as the chip yield or the transfer yield, a micro light-emitting diode is proposed in the present invention in which the process yield of the micro light-emitting diode can be effectively improved. The present invention discloses a micro light-emitting diode and a display device therefor, comprising a semiconductor layer sequence, wherein the semiconductor layer sequence comprises a back side and a front side, wherein on the front side a semiconductor layer of a first type and a semiconductor layer of a second type are arranged in sequence and an active layer therebetween, wherein the back side of the semiconductor layer sequence has a groove, wherein the groove extends through the semiconductor layer of the second type and the active layer to expose the semiconductor layer of the first type, wherein the back side of the semiconductor layer sequence has a first mesa in the groove,a second mesa on the second-type semiconductor layer and a groove sidewall arranged therebetween, wherein a first metal electrode, which is electrically connected to the first-type semiconductor layer, and a second metal electrode, which is electrically connected to the second-type semiconductor layer, are provided on the back side of the semiconductor layer sequence. The first metal electrode and the second metal electrode are used for bonding to an external power source. The first metal electrode is arranged completely within the groove to prevent the first metal electrode from encroaching onto the second mesa. The back side of the second metal electrode has a second electrode hole, wherein the second electrode hole is provided at a non-centered position on the back side of the second metal electrode.thereby achieving a more continuous and evenly distributed bonding area on the surface of the second metal electrode, which is more advantageous for a high-pressure bonding process for anisotropic conductive adhesives compared to a conventional bonding process for high-temperature melting of metals.

[0004] According to the present invention, it is preferable that the micro-LED has a rectangular shape, the length of the short edge of the micro-LED is not greater than 20 µm, the length of the long edge of the micro-LED is not greater than 30 µm, and a single edge of the first mesa is not greater than 20 µm. The smaller the size of the chip, the smaller the corresponding area of ​​the first metal electrode. The area of ​​the first metal electrode that is co-level with the second metal electrode is used for bonding with an external power source. Assuming that the first metal electrode encroaches on the second mesa, this leads to a significant reduction in the area of ​​the first metal electrode that is co-level with the second metal electrode, resulting in a lack of bonding strength.

[0005] According to the present invention, it is preferable that the groove has an open step structure, wherein three of the four sides of the groove are exposed and the other side is a groove side wall, which contributes to reducing the process margin and increasing the effective light exit area.

[0006] According to the present invention, it is preferred that the micro light-emitting diode further comprises a first insulating layer and a second insulating layer, wherein the first insulating layer has a first opening provided on a first mesa, wherein the first metal electrode is partially provided on the first mesa, wherein the first metal electrode extends from the first mesa within the first opening to the first insulating layer, wherein the second insulating layer is provided on a second mesa, wherein the second insulating layer has a second opening provided on the second mesa, wherein the second metal electrode is partially provided on the second mesa, wherein the second metal electrode extends from the second mesa within the second opening to the second insulating layer.

[0007] According to the present invention, it is preferable that the back surface of the first metal electrode corresponding to the first opening has a first electrode hole, while the back surface of the second metal electrode corresponding to the second opening has a second electrode hole, wherein the opening area of ​​the first electrode hole is smaller than the opening area of ​​the second electrode hole. By reducing the area of ​​the first electrode hole, the area of ​​the first mesa is reduced and the area of ​​the effective light exit area is increased.

[0008] According to the present invention, it is preferred that a process minimum exists in the opening area of ​​the insulating layer due to the smaller core grain size and due to process limitations, wherein the opening area of ​​the first electrode hole is 10 to 90% of the area of ​​the back surface of the first metal electrode and the opening area of ​​the second electrode hole is 10 to 90% of the area of ​​the back surface of the second metal electrode.

[0009] According to the present invention, it is preferable that the opening area is further reduced by adjusting the materials of the first insulating layer and the second insulating layer, wherein the opening area of ​​the first electrode hole is between 10% and 40% of the area of ​​the back surface of the first metal electrode and the opening area of ​​the second electrode hole is between 10% and 40% of the area of ​​the back surface of the second metal electrode.

[0010] According to the present invention, it is preferred that due to the reduction of the chip size, the first metal electrode and the second metal electrode are limited in area, wherein the projection area of ​​the back of the first metal electrode and the second metal electrode is not larger than 100 µm 2 amounts.

[0011] According to the present invention, it is preferable that the distance between the first metal electrode and the second metal electrode is 4 µm to 10 µm.

[0012] According to the present invention, it is preferable that the micro light-emitting diode is subjected to a substrate stripping process and a process for partially removing the first type semiconductor layer, so that the first type semiconductor layer of the micro light-emitting diode is at least partially removed.

[0013] According to the present invention, it is preferred that the second metal electrode has a rectangular shape as seen in rear projection, wherein the second metal electrode comprises a first edge L21, a second edge L22, a third edge L23 and a fourth edge L24 which are sequentially connected to each other, wherein the first edge L21 is close to the short edge of the micro-LED and is parallel to the short edge, while the second edge L22 and the fourth edge L24 are parallel to the long edge of the micro-LED.

[0014] According to the present invention, it is preferable that the distance between the second electrode hole and the third edge L23 is less than 1 / 2 of the distance between the second electrode hole and the first edge L21.

[0015] According to the present invention, it is preferred that the first metal electrode has a rectangular shape as seen in rear projection, wherein the first metal electrode comprises a first edge L11, a second edge L12, a third edge L13 and a fourth edge L14 which are sequentially connected, wherein the first edge L11 is close to the short edge of the micro LED and is parallel to the short edge, while the second edge L12 and the fourth edge L14 are parallel to the long edge of the micro LED, wherein the distance from the first electrode hole to the third edge L13 is less than 1 / 2 of the distance from the first electrode hole to the first edge L11.

[0016] According to the present invention, it is preferable that the first electrode hole and the second electrode hole are arranged diagonally around the center of the micro-LED.

[0017] Within the scope of the present invention, a display device is also provided with a circuit board containing a micro-light-emitting diode according to one of the above descriptions, wherein the micro-light-emitting diode is electrically connected to the circuit board by a bonding layer.

[0018] The advantageous effects of the present invention include: improving the manufacturing yield and process yield of the micron-sized chip, reducing the production cost, and promoting the industrialization of the micron-sized chip by optimizing the chip structure and / or process. Description of the accompanying drawings

[0019] To better illustrate the technical solutions in the embodiments of the present application, a brief description of the accompanying drawings necessary for the embodiments and technical illustration is provided below. It should be understood that the following accompanying drawings illustrate only some embodiments of the present application, and that other relevant accompanying drawings can be created based on these drawings without any creative effort by a person skilled in the art with ordinary knowledge in the field of technology.

[0020] In these drawings show: Fig. 1 and Fig. 2 shows a schematic plan view and a schematic sectional view of the prior art; Fig. 3 and Fig. 4 is a schematic plan view and a schematic sectional view of Embodiment 1 of the present invention, respectively; Fig. 5 and Fig. 6 is a schematic plan view and a schematic sectional view of Embodiment 2 of the present invention, respectively; Fig. 7 and Fig. 8 is a schematic plan view and a schematic sectional view of Embodiment 3 of the present invention, respectively; Fig. 9 and Fig. 10 are schematic diagrams of the method for performing macrotransfer in Embodiment 3 of the present invention; Fig. 11 is a schematic sectional view of Embodiment 4 of the present invention; Fig. 12 is a schematic sectional view of Embodiment 5 of the present invention. Specific embodiments

[0021] In order to more clearly illustrate the objects, technical solutions, and advantages of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. It is obvious that the described embodiments represent a part of the embodiments of the present invention and not all embodiments. The technical features embodied in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.Starting from the embodiments of the present invention, all other embodiments achieved by a person having ordinary skill in the art without creative work fall within the scope of the present invention.

[0022] Referring to Fig. 1 and Fig. 2, as a comparison, the prior art is constantly demanding smaller chips to improve pixel density and reduce product costs. Due to the requirement to enable isometric design of the first and second metal electrodes and to reduce the number of photomask channels, the semiconductor layer sequence of the chip is designed according to the so-called "hole-digging" principle. However, since the first metal electrode overlaps the second mesa, the area of ​​the first metal electrode that is level with the second metal electrode is limited, so the bonding yield does not meet the requirements when the micro-LED is bonded to external circuits.

[0023] With reference to Fig. 3 and Fig. 4, in a first embodiment of the present invention, a micro-LED is provided which has a rectangular shape, wherein the short edge of the micro-LED has a length of 10 µm to 20 µm and the long edge of the micro-LED has a length of 15 µm to 30 µm, e.g., the dimensions of the micro-LED are 10 µm * 25 µm. The micro-LED has a semiconductor layer sequence 110, wherein the semiconductor layer sequence 110 comprises a rear side and a front side, wherein on the front side, a semiconductor layer 111 of a first type and a semiconductor layer 112 of a second type are arranged in sequence, with an active layer 113 arranged therebetween, wherein the semiconductor layer 111 of the first type of the micro-LED is at least partially removed in the forward direction.for example, by a substrate stripping process and an epitaxial thinning process. The backside of the semiconductor layer sequence 110 has a first groove G1, wherein the first groove G1 acts as a mesa groove, wherein the first groove G1 extends through the semiconductor layer 112 of the second type and the active layer 113 and exposes the semiconductor layer 111 of the first type, wherein the backside of the semiconductor layer sequence 110 has a first mesa M1 within the first groove G1, a second mesa M2 on the semiconductor layer 112 of the second type, and a first groove sidewall S1 arranged therebetween, wherein a first metal electrode 210, which is electrically connected to the semiconductor layer 111 of the first type, and a second metal electrode 220, which is electrically connected to the semiconductor layer 112 of the second type, are arranged on the backside of the semiconductor layer sequence 1110, wherein the first metal electrode 210 and the second metal electrode 220 are used toto be connected to an external power source, wherein the first metal electrode 210 is completely provided in the groove G1.

[0024] In this embodiment, the length of a single edge of the first mesa M1 is not greater than 20 µm, wherein the first groove G1 has an open step structure, wherein three of the four sides of the groove G1 are exposed and the other side represents a groove side wall S1, ie the first mesa M1 is formed open on three sides.

[0025] This embodiment further includes a first insulating layer 310 and a second insulating layer 320, the first insulating layer 310 having a first opening K1, the first opening K1 being provided on the first mesa M1, the first metal electrode 210 being partially provided in the first opening K1 and on the first mesa M1, the first metal electrode 210 extending from the first mesa M1 within the first opening K1 to the first insulating layer 310, the second insulating layer 320 being provided on the second mesa M2, the second insulating layer 320 having a second opening K2, the second opening K2 being provided on the second mesa M2, the second metal electrode 220 being partially provided on the second mesa M2, the second metal electrode 220 extending from the second mesa M2 within the second opening K2 to the second insulating layer 320.

[0026] In this embodiment, the back surface of the first metal electrode 210, corresponding to the first opening K1, has a first electrode hole K11, while the back surface of the second metal electrode 220, corresponding to the second opening K2, has a second electrode hole K21. Since the first metal electrode 210 is entirely disposed on the first mesa M1 and the first insulating layer 310, and the second metal electrode 220 is entirely disposed on the second mesa M2 and the second insulating layer 320, the back surface of the first metal electrode 210 and the back surface of the second metal electrode 220 are of the same height, except for the first electrode hole K11 and the second electrode hole K21. In some embodiments, a transparent current extension layer may be provided between the second metal electrode 210 and the second-type semiconductor layer 112.

[0027] In this embodiment, the second mesa M2 has a rectangular shape, and a single side of the second mesa M2 has a length of 5 µm to 20 µm. It has been experimentally proven that a small rectangular shape contributes to an increase in current density and thus in the brightness of the product.

[0028] In this embodiment, the opening area of ​​the first electrode hole K11 accounts for 10% to 90% of the area of ​​the back surface of the first metal electrode 210, while the opening area of ​​the second electrode hole K12 accounts for 10% to 90% of the area of ​​the back surface of the second metal electrode 220.

[0029] Referring to Fig. 5 and Fig. 6, in a second embodiment of the present invention, considering that the first electrode hole K11 and the second electrode hole K21 will cause a lack of continuity in the distribution of the isometric areas in height on the back surfaces of the first metal electrode 210 and the second metal electrode 220, in order to further optimize the bonding yield of the metal electrodes and the external circuits, in the present embodiment, the first electrode hole K11 and the second electrode hole K21 are formed eccentrically.

[0030] The first electrode hole K11 is a circular hole with a diameter of 2 µm to 4 µm, and the center of the hole is not provided in the center of the back surface of the first metal electrode 210. Projectively, the back surface of the first metal electrode 210 has a rectangular shape, with the first edge L11, the second edge L12, the third edge L13, and the fourth edge L14 arranged sequentially.

[0031] In some embodiments, the first metal electrode 210 and the second metal electrode 220 have an edge in the range of 3 µm to 8 µm, wherein the first metal electrode 210 and the second metal electrode 220 both have a rectangular shape when viewed in projection.

[0032] The second electrode hole K12 is a circular hole with a diameter of 2 µm to 4 µm, and the center of the hole is not located at the center of the back surface of the second metal electrode 220. Projectively, the back surface of the second metal electrode 220 has a rectangular shape, with the first edge L21, the second edge L22, the third edge L23, and the fourth edge L24 arranged sequentially.

[0033] In some embodiments, the second electrode hole K21 is provided near a corner of the second metal electrode 220, i.e., the second electrode hole K21 is located between 1.5 µm and 3 µm from the center of the second metal electrode. The distance between the second electrode hole K21 and the first edge L21 is less than 1 / 2 of the distance between the second electrode hole K21 and the third edge L23, and the distance between the second electrode hole K21 and the second edge L22 is less than 1 / 2 of the distance between the second electrode hole K21 and the fourth edge L24.

[0034] In this embodiment, the opening area of ​​the first electrode hole K11 is 10% to 40% of the area of ​​the back surface of the first metal electrode 210 and / or the opening area of ​​the second electrode hole K12 is 10% to 40% of the area of ​​the back surface of the second metal electrode 220. The projection area of ​​the back surfaces of the first metal electrode 210 and the second metal electrode 220 is not larger than 100 µm 2 .

[0035] With reference to Fig. 7 and Fig. 8, in the third embodiment of the present invention, the micro-LED is improved with a distance of 4 µm to 10 µm between the first metal electrode 210 and the second metal electrode 220 based on the first two embodiments, where the inter-electrode distance refers to the minimum distance between them. Due to the fact that the first metal electrode 210 and the second metal electrode 220 are limited by the size of the chip, if the distance is too small, the isometric surfaces at the level of the first metal electrode 210 and the second metal electrode 220 are too close to each other, resulting in difficulties in forming effective support.

[0036] The first electrode hole K11 is a circular hole with a diameter of 2 µm to 4 µm, and the center of the hole is not provided at a central position on the back surface of the first metal electrode 210. Projectively, the back surface of the first metal electrode 210 has a rectangular shape, with the first edge L11, the second edge L12, the third edge L13, and the fourth edge L14 arranged sequentially; the first edge L11 is close to the short edge of the micro-LED and parallel to the short edge, and the second edge L12 and the fourth edge L14 are parallel to the long edge.

[0037] In some embodiments, the first metal electrode 210 and the second metal electrode 220 have side dimensions of 3 µm to 8 µm, and in projection, the first metal electrode 210 and the second metal electrode 220 are rectangular.

[0038] The second electrode hole K12 is a circular hole with a diameter of 2 µm to 4 µm, and the center of the hole is not located at the center of the back surface of the second metal electrode 220. Projectively, the back surface of the second metal electrode 220 has a rectangular shape, with the first edge L21, the second edge L22, the third edge L23, and the fourth edge L24 arranged sequentially. The first edge L21 is close to the short edge of the micro-LED and is parallel to the short edge, while the second edge L22 and the fourth edge L24 are parallel to the long edge. In this embodiment, the distance of the second electrode hole K21 from the third edge L23 is less than 1 / 2 of the distance of the second electrode hole K21 from the first edge L21, wherein the distance here refers to the shortest distance from the edge of the second electrode hole K21 to the first edge L21 or the third edge L23.

[0039] In some embodiments, the second electrode hole K21 is provided on the side of the second metal electrode 220 near the first metal electrode 210, thereby achieving that the bonding surface of the second metal electrode 220 is arranged substantially on the side facing away from the first metal electrode 210. In this embodiment, the second electrode hole K21 is arranged at any corner on the side of the second metal electrode 220 near the side of the first metal electrode 210, while the first electrode hole K11 can be arranged as an adaptation on the side of the first metal electrode 210 near the second metal electrode 220, wherein the first electrode hole K11 and the second electrode hole K12 are arranged diagonally to the center of the micro-LED, and wherein the second electrode hole K21 is arranged at a distance of 1.5 µm to 3 µm from the center of the second metal electrode 220.The distance from the second electrode hole K21 to the third edge L23 is less than 1 / 2 of the distance from the second electrode hole K21 to the first edge L21, and the distance from the first electrode hole K11 to the third edge L13 is less than 1 / 2 of the distance from the first electrode hole K11 to the first edge L11, wherein the distance from the second electrode hole K21 to the first metal electrode 210 is not less than 5 µm. In some embodiments of the present example, the distance between the second electrode hole K21 and the first metal electrode 210 is between 5 µm and 10 µm.

[0040] In this embodiment, the opening area of ​​the first electrode hole K11 is between 10% and 40% of the area of ​​the back surface of the first metal electrode 210, and / or the opening area of ​​the second electrode hole K12 is between 10% and 40% of the area of ​​the back surface of the second metal electrode 220. The projection area of ​​the back surface of the first metal electrode 210 and the second metal electrode 220 is not larger than 100 µm 2 .

[0041] Referring to Fig. 9 and Fig. 10, since in some embodiments the micro-LED must undergo print film imprinting, such as in a high-pixel display chip process, the micro-LED 100 has a dimension of 100 µm x 150 µm or less, and at least a portion of the positive side of the semiconductor layer of the first type of micro-LED is removed or thinned, thus stripping the primary substrate. Using the print film principle, ultra-thin and / or small components can be picked up and placed. This embodiment enables the selection and attachment of these ultra-thin, fragile, and / or small components by micro-transfer printing without core rotation.Due to the axially symmetric structure of the first metal electrode, the second metal electrode and the semiconductor layer sequence around the long edge, no rotational offset occurs during the mass transfer process, whereby the asymmetry of the electrode holes is negligible.

[0042] The mass transfer process of microtransfer printing enables the critical assembly and integration of microscale, high-performance device arrays on non-native substrates. In its simplest form, microtransfer printing is analogous to the transfer of liquid-based inks from a printing station to paper using a rubber stamper. However, in microtransfer printing, the "ink" consists of a high-performance semiconductor device in solid form, and the "paper" can be a substrate containing circuit boards, adhesive films, plastics, or other semiconductors. Microtransfer printing uses a special pre-formed elastomer imprint 400 coupled with a high-precision, controlled-motion printhead to selectively pick up and print large arrays of microscale devices onto a non-native target substrate.

[0043] Referring to Fig. 11, in a fourth embodiment of the present invention, a micro-LED is provided, in which the backside of the semiconductor layer sequence 110 comprises a first mesa M1 within a first groove G1, a second mesa M2 on a semiconductor layer 112 of the second type, and a first groove sidewall S1 arranged therebetween. In some micro-LED manufacturing processes, the front surface of the semiconductor layer 111 of the first type is used in conjunction with the imprint 400 for mass transfer.

[0044] The semiconductor layer sequence 110 is provided on the back side with a first metal electrode 210, which is electrically connected to the semiconductor layer 111 of the first type, and with a second metal electrode 220, which is electrically connected to the semiconductor layer 112 of the second type. In this embodiment, the first metal electrode 210 is connected to the first semiconductor layer 111 of the first type, while the second metal electrode 220 is connected to the semiconductor layer 112 of the second type. In one embodiment, a current extension layer, such as a transparent conductive layer, can also be provided between the second metal electrode 220 and the semiconductor layer 112 of the second type.

[0045] Further comprising a first insulating layer 310 and a second insulating layer 320, wherein the first insulating layer 310 consists of silicon oxide and / or silicon nitride, the second insulating layer 320 consists of silicon oxide, silicon nitride and titanium oxide, the first insulating layer 310 being of a lower material type than the second insulating layer 320 and the second insulating layer 320 comprising the material of the first insulating layer 310, the first insulating layer 310 having a first opening K1, the first opening K1 being provided on the first mesa M1, a sidewall of the first opening K1 and the first mesa M1 having an angle of θ1, a first metal electrode 210 being provided at least partially on the first mesa M1, the first metal electrode 210 extending from the first mesa M1 within the first opening K1 to the first insulating layer 310, the second insulating layer 320 being provided on a second mesa M2,and wherein the dashed line in the figure serves only to schematically depict the second insulating layer 320. The second insulating layer 320 comprises a portion of the first insulating layer 310, wherein the first insulating layer 310 extends from the first mesa M1 across the first groove sidewall S1 to the second mesa M2, wherein the second insulating layer 320 has a second opening K2, wherein the second opening K2 is provided on the second mesa M2, wherein the second metal electrode 220 is provided at least partially on the second mesa M2, wherein the second metal electrode 220 extends from the second mesa M2 within the second opening K2 to the second insulating layer 320. The second opening K2 has an aperture of 1 µ to 5 µ, wherein the aperture of the second opening K2 can be suitably enlarged,to improve the etching conditions and reduce the angle between the sidewall of the second opening K2 and the horizontal plane. The first metal electrode 210, corresponding to the first opening K1, has a first electrode hole K11 on the back side, while the second metal electrode 220, corresponding to the second opening K2, has a second electrode hole K21 on the back side, wherein the opening area of ​​the first electrode hole K11 is smaller than the opening area of ​​the second electrode hole K21.

[0046] In this embodiment, the second insulating layer 320 is thicker than the first insulating layer 310, with the thickness of the first insulating layer 310 being 1 / 4 to 2 / 3 of the thickness of the second insulating layer 320. In this embodiment, the first insulating layer 310 has a thickness of 0.5 to 2 µm, and the second insulating layer 320 has a thickness of 1 to 3 µm. Thinning the thickness of the first insulating layer 310 contributes to improving the production yield of the first metal electrode 210 and preventing the metal from cracking around the first opening K1.

[0047] When the aperture of the second opening K2 is between 1 and 5 µm, the aperture of the second opening K2 may be appropriately increased to improve the etching conditions and reduce the angle θ2 between the side wall of the second opening K2 and the horizontal plane.

[0048] In this embodiment, the micro-LED has a rectangular shape, the length of the short edge of the micro-LED is no larger than 15 µm, and the single side of the first mesa M1 is no larger than 15 µm. The application of micrometer-scale LEDs is limited by size requirements, and a first mesa like that of a conventional LED cannot be provided. The first mesa M1 is smaller than the second mesa M2, and the area of ​​the first mesa M1 is 1 / 2 to 4 / 5 of that of the second mesa M2, with the second mesa M2 being the main light-emitting region. In the present embodiment, the first mesa M1 is reduced in size to further increase the area of ​​the light-emitting region.

[0049] Due to the fact that the first opening K1 is provided on the first mesa M1, the smaller the area of ​​the first mesa M1, the larger the light-emitting area and the higher the efficiency of the device. Therefore, the area of ​​the first opening M1 is smaller than the area of ​​the second opening M2, the first opening K1 has an aperture of 1 µm to 3 µm and the second opening K2 has an aperture of 1 µm to 5 µm, where the aperture here indicates the maximum pitch of the opening in a plan view. The second opening K2 is provided on the second mesa M2, the aperture of the second opening K2 being greater than or equal to the aperture of the first opening K1, thereby further reducing the difficulty in machining the second opening K2.The angle between the first opening K1 and the horizontal plane is θ1, and the angle between the second opening K2 and the horizontal plane is θ2, where θ1 is not greater than θ2, and the angle between the first opening K1 and the horizontal plane θ1 is between 20° and 45°, and the angle between the second opening K2 and the horizontal plane θ2 is between 20° and 60°. The present embodiment makes it possible to reduce the angle between the first opening K1 and the horizontal plane, particularly the difficulty in controlling the angle, by controlling the type and thickness of the dielectric material of the insulating layer in the dry etching process. At the same time, the area of ​​the first electrode hole K11 is reduced, thereby increasing the effective bonding area of ​​the first metal electrode 210 and thus increasing the bonding yield.

[0050] In some embodiments of the present invention, the first insulating layer 310 is made of one dielectric material, while the second insulating layer 320 is made of two or more dielectric materials. The dielectric material of the first insulating layer 310 is different from the dielectric material of the second insulating layer 320.

[0051] In this embodiment, a second insulating layer 320 is arranged on a second mesa M2, wherein the second insulating layer 320 comprises an insulating-reflective layer 321, wherein the insulating-reflective layer 321 consists of DBR, for example with a periodic dielectric overlay of silicon dioxide and titanium dioxide, wherein the number of cycles is greater than 3, while the first insulating layer 310 extends from the first mesa M1 across the first groove sidewall S1 to the second mesa M2 and covers the insulating-reflective layer 321 to form a part of the second insulating layer 320.In the present embodiment, the window for the removal process is expanded by reducing the thickness and / or the material type of the dielectric layer under the first metal electrode 210, wherein the removal is carried out, for example, by wet etching or dry etching, and in order to further reduce the difficulty in processing the first opening K1 and to make the angle of the first opening K1 more controllable, the present invention uses, for example, dry etching.

[0052] Referring to Fig.12, in a fifth embodiment of the present invention, a display device is provided with a circuit board containing a micro-LED of any embodiment, wherein the micro-LED is electrically connected to the circuit board 500 through a bonding layer 510. The above-described appropriate design of the metal electrodes, the electrode holes, and the first groove of the micro-LED improves the product yield, particularly during the high-pressure, low-temperature bonding process, thereby increasing the bonding yield when the bonding layer 510 is made of, for example, an anisotropic conductive adhesive.

[0053] The above descriptions merely illustrate better embodiments of the present invention and are not intended to limit the present invention. Any changes, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are intended to be within the scope of the present invention.

Claims

[1] A micro light-emitting diode comprising a semiconductor layer sequence, wherein the semiconductor layer sequence comprises a rear side and a front side, wherein on the front side a semiconductor layer of a first type and a semiconductor layer of a second type are arranged in sequence and an active layer therebetween, wherein the rear side of the semiconductor layer sequence has a groove, wherein the groove runs through the semiconductor layer of the second type and the active layer to expose the semiconductor layer of the first type, wherein the rear side of the semiconductor layer sequence comprises a first mesa in the groove, a second mesa on the semiconductor layer of the second type and a groove sidewall arranged therebetween, wherein on the rear side of the semiconductor layer sequence a first metal electrode which is electrically connected to the semiconductor layer of the first type and a second metal electrode which is electrically connected to the semiconductor layer of the second type,are provided, wherein the first metal electrode and the second metal electrode are used to bond with an external power source, , characterized by that the first metal electrode is arranged completely in the groove, wherein the back of the second metal electrode has a second electrode hole, wherein the second electrode hole is arranged at a non-centered position on the back of the second metal electrode. [2] Micro-light-emitting diode according to claim 1, characterized by that the micro-LED has a rectangular shape, wherein the length of the short edge of the micro-LED is not greater than 20 µm, the length of the long edge of the micro-LED is not greater than 30 µm and a single edge of the first mesa is not greater than 20 µm. [3] Micro-light-emitting diode according to claim 1, characterized bythat the groove has an open step structure, with three of the four sides of the groove being exposed and the other side representing a groove side wall. [4] Micro-light-emitting diode according to claim 1, characterized byin that it further comprises a first insulating layer and a second insulating layer, wherein the first insulating layer has a first opening provided on a first mesa, wherein the first metal electrode is partially provided on the first mesa, wherein the first metal electrode extends from the first mesa within the first opening to the first insulating layer, wherein the second insulating layer is provided on a second mesa, wherein the second insulating layer has a second opening provided on the second mesa, wherein the second metal electrode is partially provided on the second mesa, wherein the second metal electrode extends from the second mesa within the second opening to the second insulating layer, wherein a first electrode hole on the back side of the first metal electrode corresponds to the first opening and a second electrode hole on the back side of the second metal electrode corresponds to the second opening. [5] Micro-light-emitting diode according to claim 4, characterized by that the material of the first insulating layer is not completely identical to the material of the second insulating layer, wherein the first insulating layer contains silicon dioxide and the second insulating layer contains titanium dioxide. [6] Micro-light-emitting diode according to claim 4, characterized by that the back side of the first metal electrode corresponding to the first opening has a first electrode hole and the back side of the second metal electrode corresponding to the second opening has a second electrode hole, wherein the opening area of ​​the first electrode hole is smaller than the opening area of ​​the second electrode hole. [7] Micro-light-emitting diode according to claim 5, characterized bythat the opening area of ​​the first electrode hole is 10% to 90% of the area of ​​the back side of the first metal electrode and the opening area of ​​the second electrode hole is 10% to 90% of the area of ​​the back side of the second metal electrode. [8] Micro-light-emitting diode according to claim 5, characterized by that the opening area of ​​the first electrode hole is 10% to 40% of the area of ​​the back side of the first metal electrode and the opening area of ​​the second electrode hole is 10% to 40% of the area of ​​the back side of the second metal electrode. [9] Micro-LED according to claim 5, characterized by that the projection area of ​​the back of the first metal electrode and the second metal electrode is not larger than 100 µm 2 is. [10] Micro-light-emitting diode according to claim 1, characterized by that the distance between the first metal electrode and the second metal electrode is 4 µm to 10 µm. [11] Micro-light-emitting diode according to claim 1, characterized by that the semiconductor layer of the first type is at least partially removed from the micro-light-emitting diode in the forward direction. [12] Micro-light-emitting diode according to claim 2, characterized by in that the second metal electrode has a rectangular shape when viewed in rear projection, and the second metal electrode comprises a first edge L21, a second edge L22, a third edge L23 and a fourth edge L24 which are connected to one another in succession, the first edge L21 being close to the short edge of the micro-LED and parallel to the short edge, and the second edge L22 and the fourth edge L24 being parallel to the long edge of the micro-LED. [13] Micro-LED according to claim 12, characterized by that the distance between the second electrode hole and the third edge L23 is less than 1 / 2 of the distance between the second electrode hole and the first edge L21. [14] Micro-LED according to claim 13, characterized by that the second metal electrode has a rectangular shape when viewed in rear projection and the second metal electrode comprises a first edge L11, a second edge L12, a third edge L13 and a fourth edge L14 which are connected to one another one after the other, wherein the first edge L11 is close to the short edge of the micro light-emitting diode and parallel to the short edge and wherein the second edge L12 and the fourth edge L14 are parallel to the long edge of the micro light-emitting diode, and wherein the distance between the first electrode hole and the third edge L13 is less than 1 / 2 the distance between the first electrode hole and the first edge L11. [15] Micro-LED according to claim 14, characterized by that the first electrode hole and the second electrode hole are arranged diagonally around the center of the micro-LED. [16] A display device comprising a circuit board containing a micro-light-emitting diode according to any one of claims 1 to 15, wherein the micro-light-emitting diode is electrically connected to the circuit board by a bonding layer. [17] Display device according to claim 16, characterized by that the micro LED is bonded to the circuit board with an anisotropic conductive adhesive.

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