Micro LED multi-color chip and preparation method thereof

Abstract

The application provides a micro LED multi-color chip and a preparation method thereof. By integrating red, green and blue light emitting units on the same substrate, chips of different colors can be avoided from being transferred to a driving circuit substrate for multiple times, the complexity of the transfer process is simplified, the production efficiency is improved, small-size full-color pixels are facilitated to be prepared, and the resolution of an LED display screen is improved. In the preparation of the chip array, anode contact surfaces and cathode contact surfaces of each light emitting unit of each full-color pixel are respectively exposed by selective etching, then the cathode contact surfaces of each light emitting unit of each full-color pixel are connected in common by a metal bonding layer, the difficulty of wiring and integration process is reduced, and the application of the application to mass production is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor devices, in particular to a micro-LED multi-color chip and a preparation method thereof. BACKGROUND

[0002] From the application scene, micro-LED is mainly applied to direct display and backlight field. Unlike micro-LED backlight, micro-LED direct display technology directly uses micro-LED multi-color chip as display pixel point to provide basic unit of imaging, so as to realize full-color image display, and the technology has advantages of high brightness, wide color gamut, high contrast, fast response, low power consumption and long service life, and is expected to be widely applied to high-end LED display field in the future.

[0003] The full-color micro-LED display screen is assembled by red, green and blue (RGB) micro-LED chips on a driving circuit substrate in a certain arrangement mode. Since the size of the micro-LED chip is small, three times of transfer of R / G / B micro-LED chips is needed for manufacturing the full-color micro-LED display screen, so that the transfer efficiency and device yield will be limited to a certain extent, and there are problems such as difficulty in reducing the full-color pixel pitch.

[0004] In the prior art, although there is a technical solution of integrating red, green and blue LED structures on one substrate to avoid transferring R / G / B micro-LED chips three times, but there is a problem of complex wiring process through the technical solution, which leads to that this solution cannot be directly applied to mass production. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a micro-LED multi-color chip and a preparation method thereof, to solve the problem that there is no preparation method of micro-LED multi-color chip which can be mass-produced without three times of transfer in the prior art.

[0006] The present application provides a preparation method of a micro-LED multi-color chip, which comprises:

[0007] providing a substrate and growing an epitaxial layer on the substrate, the epitaxial layer comprising a first light-emitting stack, a second light-emitting stack and a third light-emitting stack stacked in sequence;

[0008] partially etching the epitaxial layer to form a first light-emitting unit, a second light-emitting unit and a third light-emitting unit, and expose the anode contact surface and the cathode contact surface of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit;

[0009] preparing a passivation layer on the surface of the epitaxial layer, the passivation layer being provided with a through hole, the through hole exposing the anode contact surface and the cathode contact surface of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit;

[0010] The first ohmic contact electrode is prepared at the via position of the cathode contact surface of the first, second and third light emitting units, and the second ohmic contact electrode is prepared at the via position of the anode contact surface;

[0011] The metal bonding stack is prepared on the first and second ohmic contact electrodes, and the first ohmic contact electrodes of the first, second and third light emitting units are connected through the metal bonding stack.

[0012] Each light emitting unit is one of a blue light unit, a green light unit or a red light unit, and the colors of each unit are different from each other.

[0013] In some embodiments of the present application, the outermost layer of the metal bonding stack is at the same level.

[0014] In some embodiments of the present application, the surfaces of the first, second and third light emitting units are at the same level.

[0015] In some embodiments, the first light emitting unit includes a first light emitting stack, a second light emitting stack and a third light emitting stack, the second light emitting unit includes the second light emitting stack and the third light emitting stack, and the third light emitting unit includes the third light emitting stack.

[0016] In some embodiments, the first light emitting stack includes a first N-type semiconductor layer, a first light emitting layer and a first P-type semiconductor layer stacked in sequence, the second light emitting stack includes a second N-type semiconductor layer, a second light emitting layer and a second P-type semiconductor layer stacked in sequence, and the third light emitting stack includes a third N-type semiconductor layer, a third light emitting layer and a third P-type semiconductor layer stacked in sequence; the cathode contact surface of the first, second and third light emitting units is the side of the first, second and third N-type semiconductor layers away from the substrate; and the anode contact surface of the first, second and third light emitting units is the side of the first, second and third P-type semiconductor layers away from the substrate.

[0017] In some embodiments of the present application, the step of partially etching the epitaxial layer includes: selectively etching the epitaxial layer so that the first, second and third light emitting units expose the first, second and third N-type semiconductor layers, respectively; and groove etching the first and second light emitting units so that the first P-type semiconductor layer of the first light emitting unit and the second P-type semiconductor layer of the second light emitting unit are at least partially exposed, thereby obtaining a chip array in which the first, second and third light emitting units are at the same level.

[0018] In some embodiments, the step of preparing the metal bonding stack on the first ohmic contact electrode comprises: forming a metal bonding stack on the first ohmic contact electrode of the first light emitting unit, the second light emitting unit and the third light emitting unit respectively by a metal deposition technique, and the first ohmic contact electrode of the first light emitting unit, the second light emitting unit and the third light emitting unit are connected to each other through the metal bonding stack.

[0019] In some embodiments of the present application, the step of preparing the metal bonding stack on the second ohmic contact electrode comprises: forming a metal bonding stack on the second ohmic contact electrode and the third P-type semiconductor layer of the first light emitting unit, forming a metal bonding stack on the second ohmic contact electrode and the third P-type semiconductor layer of the second light emitting unit, and forming a metal bonding stack on the second ohmic contact electrode of the third light emitting unit by a metal deposition technique.

[0020] In some embodiments, the material of the metal bonding stack is any one or a combination of Cr, Pt, In, Sn and Au.

[0021] The second aspect of the present application further provides a micro-LED multi-color chip prepared by the preparation method of the micro-LED multi-color chip.

[0022] The present application can avoid transferring chips of different colors to a driving circuit substrate for multiple times, simplify the complexity of the transfer process, improve the production efficiency, and reduce the pitch of full-color pixels, which is beneficial to improving the resolution of the LED display screen. In the preparation of the chip array, the anode contact surface and the cathode contact surface of each light emitting unit of the full-color pixel are exposed by selective etching, and then the cathode contact surface of each light emitting unit of the sub-pixel in each full-color pixel is connected in common through a metal bonding stack, which reduces the difficulty of wiring and integration process, and facilitates the direct application of the present application to mass production. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A schematic diagram of growing an epitaxial layer for an embodiment of the present application.

[0024] Figure 2 A schematic diagram of etching an epitaxial layer for an embodiment of the present application.

[0025] Figure 3 A schematic diagram of preparing a passivation layer for an embodiment of the present application.

[0026] Figure 4 A schematic diagram of preparing an ohmic contact electrode for an embodiment of the present application.

[0027] Figure 5A schematic diagram of preparing a metal bond stack for embodiments of the present application. DETAILED DESCRIPTION

[0028] For the purposes of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings. The embodiments shown are intended to be illustrative only and not limiting of the present application. The present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The embodiments shown are intended as non-limiting examples of the application.

[0029] It should be noted that when an element as a "on" or "adjacent" another element, it can be directly on the other element or an intervening element can also be present. When an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements can also be present. As used herein the terms "vertical", "horizontal", "left", "right" and the like are merely used for the purpose of illustration.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "including" and "having" are intended to be inclusive and mean that there can be additional elements other than the listed elements.

[0031] Referring to Figures 1 to 5 , the present application provides a preparation method of a micro-LED multi-color chip, the preparation method comprising:

[0032] Step S1, providing a substrate 100, and growing an epitaxial layer on the substrate, the epitaxial layer comprising a first light-emitting stack, a second light-emitting stack and a third light-emitting stack stacked in sequence.

[0033] In some embodiments of the present application, as shown in Figure 1 , the first light-emitting stack comprises a first N-type semiconductor layer 121, a first light-emitting layer 122 and a first P-type semiconductor layer 123 stacked in sequence, the second light-emitting stack comprises a second N-type semiconductor layer 131, a second light-emitting layer 132 and a second P-type semiconductor layer 133 stacked in sequence, and the third light-emitting stack comprises a third N-type semiconductor layer 141, a third light-emitting layer 142 and a third P-type semiconductor layer 143 stacked in sequence. The first light-emitting layer 122, the second light-emitting layer 132 and the third light-emitting layer 142 respectively emit one of blue light, green light or red light, and the color of each light-emitting layer is different from each other.

[0034] In some embodiments of the present application, the substrate 100 can be a sapphire substrate or a silicon substrate. Before growing the epitaxial layer, a buffer layer 110 can be grown in the MOCVD system, and the material of the buffer layer 110 can be AlN. The N-type semiconductor layer can be an n-GaN layer, the P-type semiconductor layer can be a p-GaN layer, and the light-emitting layer can be an InGaN / GaN quantum well layer.

[0035] Step S2, partially etching the epitaxial layer to form the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit, and expose the anode contact surface and the cathode contact surface of the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit.

[0036] In some embodiments of the present application, the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit are formed by partially etching the epitaxial layer, and then the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit are processed by a preset material removal method, so that the first N-type semiconductor layer 121, the second N-type semiconductor layer 131, and the third N-type semiconductor layer 141 are exposed, respectively. The first N-type semiconductor layer 121, the second N-type semiconductor layer 131, and the third N-type semiconductor layer 141 are the cathode contact surfaces of the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit. The first P-type semiconductor layer 123 of the first light-emitting unit and the second P-type semiconductor layer 133 of the second light-emitting unit are at least partially exposed by groove etching. The first P-type semiconductor layer 123, the second P-type semiconductor layer 133, and the third P-type semiconductor layer 143 are the anode contact surfaces of the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit. Then, the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit at the same horizontal height are obtained, and the structure formed is as shown in FIG. 2. Figure 2

[0037] In some embodiments of the present application, the first light-emitting unit includes a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack, the second light-emitting unit includes the second light-emitting stack and the third light-emitting stack, and the third light-emitting unit includes the third light-emitting stack.

[0038] It should be noted that by first growing the light-emitting layers of each color unit on the same substrate, then obtaining a plurality of light-emitting units by selective etching, and then removing the color units and the light-emitting layers on different light-emitting units as needed, the light-emitting units can control different colors of light.

[0039] Step S3, preparing a passivation layer 150 on the surface of the epitaxial layer, and the passivation layer 150 is provided with a through hole, and the through hole exposes the anode contact surface and the cathode contact surface of the first light-emitting unit, the second light-emitting unit, and the third light-emitting unit. ​

[0040] In some embodiments of the present application, a passivation layer material is first deposited on the surface of the epitaxial layer, and then a through hole is etched by photolithography and wet etching or dry etching, exposing the first N-type semiconductor layer 121 and the first P-type semiconductor layer 123 of the first light emitting unit, the second N-type semiconductor layer 131 and the second P-type semiconductor layer 133 of the second light emitting unit, and the third N-type semiconductor layer 141 and the third P-type semiconductor layer 143 of the third light emitting unit. The preparation of the passivation layer 150 is completed, and the structure formed is as shown in Figure 3 .

[0041] In some embodiments of the present application, the material of the passivation layer 150 is any one or a combination of silicon nitride, aluminum nitride, silicon oxide, and aluminum oxide. Alternatively, the material of the passivation layer 150 is an organic curing material, such as a polyimide photoresist or an SU-8 photoresist.

[0042] Step S4, a first ohmic contact electrode is prepared at the through hole position of the cathode contact surface of the first light emitting unit, the second light emitting unit, and the third light emitting unit, respectively, and a second ohmic contact electrode is prepared at the through hole position of the anode contact surface.

[0043] In some embodiments of the present application, as shown in Figure 4 , metal deposition is performed on the epitaxial layer, forming a first cathode electrode 161 on the first N-type semiconductor layer 121 of the first light emitting unit, and a first anode electrode 171 on the first P-type semiconductor layer 123; forming a second cathode electrode 162 on the second N-type semiconductor layer 131 of the second light emitting unit, and a second anode electrode 172 on the second P-type semiconductor layer 133; forming a third cathode electrode 163 on the third N-type semiconductor layer 141 of the third light emitting unit, and a third anode electrode 173 on the third P-type semiconductor layer 143. The first light emitting unit, the first cathode electrode 161, and the first anode electrode 171 constitute a first chip, the second light emitting unit, the second cathode electrode 162, and the second anode electrode 172 constitute a second chip, and the third light emitting unit, the third cathode electrode 163, and the third anode electrode 173 constitute a third chip, thereby forming an RGB Mini-LED chip array.

[0044] It should be noted that the first cathode electrode 161, the second cathode electrode 162, and the third cathode electrode 163 are collectively referred to as a first ohmic contact electrode, and the first anode electrode 171, the second anode electrode 172, and the third anode electrode 173 are collectively referred to as a second ohmic contact electrode.

[0045] Step S5, a metal bonding stack is prepared on the first ohmic contact electrode and the second ohmic contact electrode, respectively, and the first ohmic contact electrodes of the first light emitting unit, the second light emitting unit, and the third light emitting unit are connected through the metal bonding stack.

[0046] In some embodiments of the present application, as shown in Figure 5 The epitaxial layer is subjected to metal deposition to form a first metal bonding stack 181 on the first anode electrode 171 and part of the third P-type semiconductor layer 143, to form a second metal bonding stack 182 on the second anode electrode 172 and part of the third P-type semiconductor layer 143, and to form a third metal bonding stack 183 on the third anode electrode 173. The first cathode electrode 161, the second cathode electrode 162, and the third cathode electrode 163 are connected to part of the third P-type semiconductor layer 143 to form a fourth metal bonding stack 180. The first cathode electrode 161, the second cathode electrode 162, and the third cathode electrode 163 are connected to each other through the fourth metal bonding stack 180. The outermost layers of the first metal bonding stack 181, the second metal bonding stack 182, the third metal bonding stack 183, and the fourth metal bonding stack 180 are at the same level. The preparation of the micro-LED multi-color chip is completed.

[0047] It should be noted that the first metal bonding stack 181, the second metal bonding stack 182, the third metal bonding stack 183, and the fourth metal bonding stack 180 are collectively referred to as a metal bonding stack.

[0048] In some embodiments of the present application, the material of the metal bonding stack is any one or a combination of Cr, Pt, In, Sn, and Au. Embodiment 1

[0049] Please refer to Figures 1 to 5 The present embodiment provides a preparation method of a micro-LED multi-color chip, comprising the following steps:

[0050] Step S1, as shown in Figure 1 An AlN buffer layer is grown on the silicon substrate, and an epitaxial layer is grown on the AlN buffer layer. The epitaxial layer comprises a blue light stack, a green light stack, and a red light stack stacked in sequence. The blue light stack comprises a first N-type semiconductor layer 121, a first light-emitting layer 122, and a first P-type semiconductor layer 123 stacked in sequence. The green light stack comprises a second N-type semiconductor layer 131, a second light-emitting layer 132, and a second P-type semiconductor layer 133 stacked in sequence. The red light stack comprises a third N-type semiconductor layer 141, a third light-emitting layer 142, and a third P-type semiconductor layer 143 stacked in sequence.

[0051] The N-type semiconductor layer is an n-GaN layer, the P-type semiconductor layer is a p-GaN layer, and the light-emitting layer is an InGaN / GaN quantum well layer.

[0052] Step S2, the epitaxial layer is partially etched to form a blue light unit, a green light unit and a red light unit, and then the blue light unit, the green light unit and the red light unit are treated by a preset material removal method, so that the first N-type semiconductor layer 121, the second N-type semiconductor layer 131 and the third N-type semiconductor layer 141 are exposed respectively. The first N-type semiconductor layer 121, the second N-type semiconductor layer 131 and the third N-type semiconductor layer 141 are the cathode contact surfaces of the blue light unit, the green light unit and the red light unit. Then, the blue light unit and the green light unit are subjected to groove etching, so that the first P-type semiconductor layer 123 of the blue light unit is partially exposed, and the second P-type semiconductor layer 133 of the green light unit is partially exposed. The first P-type semiconductor layer 123, the second P-type semiconductor layer 133 and the third P-type semiconductor layer 143 are the anode contact surfaces of the blue light unit, the green light unit and the red light unit. Then, the blue light unit, the green light unit and the red light unit at the same horizontal height are obtained, and the structure formed is as shown in Figure 2 .

[0053] The blue light unit includes a blue light stack, a green light stack and a red light stack, the green light unit includes a green light stack and a red light stack, and the red light unit only includes a red light stack.

[0054] Step S3, silicon dioxide is deposited on the surface of the epitaxial layer, and then a through hole is etched by the method of photoetching and wet etching, so that the first N-type semiconductor layer 121 and the first P-type semiconductor layer 123 of the blue light unit, the second N-type semiconductor layer 131 and the second P-type semiconductor layer 133 of the green light unit, and the third N-type semiconductor layer 141 and the third P-type semiconductor layer 143 of the red light unit are exposed. The preparation of the passivation layer 150 is completed, and the structure formed is as shown in Figure 3 .

[0055] Step S4, as shown in Figure 4 , metal deposition is performed on the epitaxial layer, the first N-type semiconductor layer 121 of the blue light unit is formed with a first cathode electrode 161, and the first P-type semiconductor layer 123 is formed with a first anode electrode 171; the second N-type semiconductor layer 131 of the green light unit is formed with a second cathode electrode 162, and the second P-type semiconductor layer 133 is formed with a second anode electrode 172; the third N-type semiconductor layer 141 of the red light unit is formed with a third cathode electrode 163, and the third P-type semiconductor layer 143 is formed with a third anode electrode 173. The first light emitting unit, the first cathode electrode 161 and the first anode electrode 171 constitute a first chip, the second light emitting unit, the second cathode electrode 162 and the second anode electrode 172 constitute a second chip, and the third light emitting unit, the third cathode electrode 163 and the third anode electrode 173 constitute a third chip, thereby forming an RGB Mini-LED chip array.

[0056] Step S5, as shown in Figure 5As shown, the metal Au is deposited to form a first metal bonding stack 181 on the first anode electrode 171 and part of the third P-type semiconductor layer 143, to form a second metal bonding stack 182 on the second anode electrode 172 and part of the third P-type semiconductor layer 143, and to form a third metal bonding stack 183 on the third anode electrode 173. The first cathode electrode 161, the second cathode electrode 162, and the third cathode electrode 163 are formed on part of the third P-type semiconductor layer 143 to form a fourth metal bonding stack 180. The first cathode electrode 161, the second cathode electrode 162, and the third cathode electrode 163 are connected to each other through the fourth metal bonding stack 180. The outermost layers of the first metal bonding stack 181, the second metal bonding stack 182, the third metal bonding stack 183, and the fourth metal bonding stack 180 are at the same level.

[0057] The micro-LED multi-color chip prepared in the embodiment is as shown in FIG. 6. Figure 5 As shown, the micro-LED multi-color chip is a full-color chip, and is characterized in that the blue light unit, the green light unit, and the red light unit in the RGB Mini-LED chip array are at the same height and do not have a step difference. The outermost layers of the metal bonding stacks of all the chips will be at the same level, so that the subsequent packaging and electrical connection of the chip array are simpler and more reliable. The first chip, the second chip, and the third chip are integrated on the same substrate, and the blue, green, and red lights are controlled by the first chip, the second chip, and the third chip, respectively.

[0058] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a micro-LED multi-color chip, characterized in that, The preparation method comprises: providing a substrate and growing an epitaxial layer on the substrate, the epitaxial layer comprising a first light-emitting stack, a second light-emitting stack and a third light-emitting stack stacked in sequence; partially etching the epitaxial layer to form a first light-emitting unit, a second light-emitting unit and a third light-emitting unit, and expose anode contact surfaces and cathode contact surfaces of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit; preparing a passivation layer on the surface of the epitaxial layer, the passivation layer being provided with through holes, the through holes exposing the anode contact surfaces and the cathode contact surfaces of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit; respectively preparing a first ohmic contact electrode at the through hole position of the cathode contact surface of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit, and a second ohmic contact electrode at the through hole position of the anode contact surface; respectively preparing a metal bonding stack on the first ohmic contact electrode and the second ohmic contact electrode, the first ohmic contact electrodes of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit being connected through the metal bonding stack; each of the light-emitting units is one of a blue light unit, a green light unit or a red light unit, and the colors of each unit are different from each other.

2. The method of claim 1, wherein: The outermost layer of the metal bonding stack is at the same level.

3. The method of claim 1, wherein: The surfaces of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit are at the same level.

4. The method of claim 3, wherein: The first light-emitting unit comprises the first light-emitting stack, the second light-emitting stack and the third light-emitting stack, the second light-emitting unit comprises the second light-emitting stack and the third light-emitting stack, and the third light-emitting unit comprises the third light-emitting stack.

5. The preparation method of the micro-LED multi-color chip according to claim 1, wherein: the first light-emitting stack comprises a first N-type semiconductor layer, a first light-emitting layer and a first P-type semiconductor layer stacked in sequence, the second light-emitting stack comprises a second N-type semiconductor layer, a second light-emitting layer and a second P-type semiconductor layer stacked in sequence, and the third light-emitting stack comprises a third N-type semiconductor layer, a third light-emitting layer and a third P-type semiconductor layer stacked in sequence; the cathode contact surfaces of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit are the far sides of the first N-type semiconductor layer, the second N-type semiconductor layer and the third N-type semiconductor layer from the substrate, and the anode contact surfaces of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit are the far sides of the first P-type semiconductor layer, the second P-type semiconductor layer and the third P-type semiconductor layer from the substrate.

6. The method of claim 5, wherein the method further comprises: The step of partially etching the epitaxial layer comprises: selectively etching the epitaxial layer so that the first N-type semiconductor layer, the second N-type semiconductor layer and the third N-type semiconductor layer of the first light-emitting unit, the second light-emitting unit and the third light-emitting unit are exposed respectively; slot etching the first light-emitting unit and the second light-emitting unit so that the first P-type semiconductor layer of the first light-emitting unit is at least partially exposed, and the second P-type semiconductor layer of the second light-emitting unit is at least partially exposed, thereby obtaining a chip array in which the first light-emitting unit, the second light-emitting unit and the third light-emitting unit are at the same level.

7. The method of claim 1, wherein the method further comprises: The step of preparing a metal bonding stack on the first ohmic contact electrode comprises: forming a metal bonding stack on the first ohmic contact electrode of the first light emitting unit, the second light emitting unit and the third light emitting unit respectively by a metal deposition technique, and the first ohmic contact electrode of the first light emitting unit, the second light emitting unit and the third light emitting unit are connected to each other by the metal bonding stack.

8. The method of claim 5, wherein the method further comprises: The step of preparing a metal bonding stack on the second ohmic contact electrode comprises: forming a metal bonding stack on the second ohmic contact electrode and the third P-type semiconductor layer of the first light emitting unit, forming a metal bonding stack on the second ohmic contact electrode and the third P-type semiconductor layer of the second light emitting unit, and forming a metal bonding stack on the second ohmic contact electrode of the third light emitting unit by a metal deposition technique.

9. The method of claim 1, wherein the method further comprises: The material of the metal bonding stack is any one or a combination of Cr, Pt, In, Sn and Au.

10. A micro-LED multi-color chip, characterized in that, The micro-LED multi-color chip is prepared by the preparation method of the micro-LED multi-color chip according to any one of claims 1-6.

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