CN110444559B - Micro-LED array and preparation method thereof - Google Patents

Abstract

The invention discloses a Micro-LED array and a preparation method thereof, and relates to the field of LED packaging. It mainly includes a silicon substrate, a metal substrate, and a plurality of identical light-emitting chips located between the silicon substrate and the metal substrate; the light-emitting chips are arranged in sequence from bottom to top Metal contacts, p-type gallium nitride layer, multiple quantum well layer and n-type gallium nitride layer; wirings are arranged on the silicon substrate, the metal contacts are electrically interconnected with the silicon substrate through the wirings, and the metal substrate is arranged on the n-type gallium nitride The metal contact is used as the p-electrode of the light-emitting chip; the metal substrate is used as the n-electrode of the light-emitting chip; when the silicon substrate is energized, the current flows from the metal contact to the metal substrate to realize the light emission of the Micro-LED array. The Micro-LED array and the preparation method thereof disclosed in the invention can realize the gold-free encapsulation of the Micro-LED array.

Description

A kind of Micro-LED array and preparation method thereof

technical field

The invention relates to the field of LED packaging, in particular to a Micro-LED array and a preparation method thereof.

Background technique

The bonding wire is a very important part of the LED packaging process. The four major substrates used in the bonding wire are gold, silver, copper, and aluminum. The gold wire has high electrical conductivity, corrosion resistance, good toughness and oxidation resistance. Advantages, is a good choice. Gold wire bonding acts as a wire connection in the LED package, connecting the chip surface electrode and the substrate to realize the electrical interconnection of the LED.

Micro-LED technology, that is, LED miniaturization and matrix technology, refers to a high-density tiny-sized LED array integrated on a chip. The Micro-LED array is actually an array of LEDs after miniaturization, and the size is below 100um. Micro-LED not only has all the advantages of self-illumination, small size, light weight, high brightness, longer life, lower power consumption, faster response time and better controllability of LEDs, but also has obvious high However, its chip size is less than 100um, and commercialization still faces many challenges, such as mass transfer technology, full-color display, epitaxy technology, bonding technology Wait. Although Micro-LED not only inherits the advantages of high efficiency, high brightness, high reliability and fast response time of inorganic LED, but also has the characteristics of self-illumination without backlight, and has the advantages of energy saving, simple structure, small size and thin shape. However, because the chip of Micro-LED is too small, generally less than 100um, it is very difficult to use the general gold wire bonding method.

Ordinary GaN-based LED packaging structures mainly include front-loading, flip-chip and vertical structures. The front-loading structure is simple to manufacture, and the process is mature, and the light emitted from the active region exits through the P-type GaN region and the transparent electrode. However, because the p and n electrodes of the front-mounted LED are on the same side, and the current flows laterally through the n-GaN layer, there is a problem of current crowding; secondly, due to the poor thermal conductivity of the sapphire substrate, it will cause a problem of low heat dissipation efficiency; and gold wire bonds Coupling is an indispensable process for formal structures. The flip-chip structure is based on the traditional front-mounted LED chip packaging, inverting the LED chip and soldering it with a silicon substrate with metal bumps. Compared with the front-mounted packaging process, the gold wire bonding process is reduced and the wires are removed. The steps of frame and wire bonding make the package volume smaller and further improve the heat dissipation efficiency, but there is still the problem of current crowding. The p-electrode and n-electrode of the vertical structure are distributed on the top and bottom surfaces of the LED structure respectively, and the current flows vertically from the p-electrode to the n-electrode, which can effectively solve the problems of heat dissipation and current crowding, but cannot avoid the gold wire bonding process. Suitable for Micro-LED arrays. In addition, the existing wafer-level monolithic hybrid integration technology, the monolithic processing method is not suitable for large arrays, which is time-consuming, and the single-chip integration during the bonding process requires a high alignment process, so it is not suitable for Micro-LED array.

Most of the Micro-LED arrays used in the mainstream of the market use a formal structure. Using the front-loading structure, on the one hand, there is a problem of current crowding because the current flows laterally through the n-GaN layer; on the other hand, since the commonly used Micro-LEDs are sapphire substrates (Al ₂ O ₃ ) High hardness, low thermal and electrical conductivity, will seriously affect the heat dissipation of the device under high current conditions. The most important thing is that for Micro-LEDs whose size is less than 100um, because the single chip in the Micro-LED array is very small, and the single chip in the Micro-LED array is a positive-mounted structure, it is necessary for the single chip in the Micro-LED array. Gold wire bonding of chips is very difficult, and the gold wire bonding process is difficult to complete.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a Micro-LED array and a preparation method thereof, which can realize the gold-free encapsulation of the Micro-LED array.

For achieving the above object, the present invention provides the following scheme:

A Micro-LED array, comprising a silicon substrate, a metal substrate, and a plurality of identical light-emitting chips located between the silicon substrate and the metal substrate;

The light-emitting chip is provided with metal contacts, p-type gallium nitride layer, multiple quantum well layer and n-type gallium nitride layer in sequence from bottom to top; wherein, wiring is provided on the silicon substrate, and the metal contacts pass through all the the wiring is electrically interconnected with the silicon substrate, and the metal substrate is arranged on the n-type gallium nitride layer;

The metal contact is used as the p-electrode of the light-emitting chip, the metal contact is used to generate holes, and the p-type gallium nitride layer is used to transmit the holes; the metal substrate is used as the light-emitting chip the n-electrode, the metal substrate is used to generate the electrons; the n-type gallium nitride layer is used to transport the electrons; the multiple quantum well layer is used to recombine the electrons and the holes, Photons are generated; when the silicon substrate is energized, the current flows from the metal contacts to the metal substrate to realize the light emission of the Micro-LED array.

Optionally, the light-emitting chips are arranged in an array between the silicon substrate and the metal substrate.

Optionally, the metal contacts are made of gold or nickel/gold alloy.

Optionally, the metal substrate is a copper substrate.

For achieving the above object, the present invention also provides the following scheme:

A preparation method of a Micro-LED array, comprising:

A plurality of identical light-emitting chips are simultaneously grown on a sapphire substrate; the light-emitting chips are chips sequentially grown with an n-type gallium nitride layer, a multiple quantum well layer, a p-type gallium nitride layer and metal contacts, wherein the The n-type gallium nitride layer is grown on a sapphire substrate;

According to the positions of the metal contacts on the sapphire substrate, wirings corresponding to the metal contacts are arranged on the silicon substrate;

inverting the sapphire substrate on which the light-emitting chip is grown, and bonding the inverted sapphire substrate to the silicon substrate through the metal contacts and the wiring to obtain a bonding array;

The sapphire substrate on the bonding array is peeled off, and then a metal substrate is bonded to each of the n-type gallium nitride layers.

Optionally, the growth step of the light-emitting chip specifically includes:

growing the n-type gallium nitride layer on the sapphire substrate;

growing the multiple quantum well layer on the n-type gallium nitride layer;

growing the p-type gallium nitride layer on the multiple quantum well layer;

Metal deposition is performed on the p-type gallium nitride layer to form the metal contacts.

Optionally, the bonding of the inverted sapphire substrate to the silicon substrate through the metal contacts and the wiring specifically includes:

The inverted sapphire substrate is bonded to the silicon substrate through the metal contacts and the wiring by using thermal pressure flip-chip welding, ultrasonic thermal pressure welding or conductive adhesive.

Optionally, the peeling off the sapphire substrate on the bonding array specifically includes:

The sapphire substrate on the bonding array is peeled off using a laser lift-off technique.

Optionally, performing metal deposition on the p-type gallium nitride layer to form the metal contact specifically includes:

The metal contacts are formed on the p-type gallium nitride layer by deposition method, sputtering method or electroplating method.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the Micro-LED array and the preparation method thereof disclosed in the present invention use the metal contact of the light-emitting chip as the p-electrode and the metal substrate as the n-electrode, Wiring is arranged on the silicon substrate, so that the light-emitting chip is directly electrically interconnected with the silicon substrate through metal contacts and wirings, so that the gold wire bonding operation of a single light-emitting chip in the Micro-LED array is not required, and the gold-free micro-LED array is realized. wire package. And when the silicon substrate is energized, the current flows from the metal contacts to the metal substrate, energizing the p-electrode and the n-electrode, and the multi-quantum well layer generates photons, which can realize the light-emitting of the Micro-LED array.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

FIG. 1 is a structural diagram of an embodiment of the Micro-LED array of the present invention;

2 is a flow chart of an embodiment of a method for preparing a Micro-LED array of the present invention;

3 is a schematic diagram of a single structural unit of the bonding array of the present invention;

FIG. 4 is a schematic diagram of a front-loading structure in a common GaN-based LED packaging structure;

5 is a schematic diagram of a vertical structure in a common GaN-based LED packaging structure;

6 is a schematic diagram of a flip-chip structure in a common GaN-based LED packaging structure;

FIG. 7 is a schematic diagram showing that p-electrodes and n-electrodes are respectively distributed on the upper top surface and the lower bottom surface of the LED structure in the vertical structure;

8 is a schematic diagram of p-electrodes and n-electrodes distributed on the lower bottom surface and the upper top surface of the LED structure in a vertical structure, respectively;

FIG. 9 is a schematic diagram of gold wire bonding of a positive structure in a common GaN-based LED package;

10 is a schematic diagram of vertical structure gold wire bonding in a common GaN-based LED package;

FIG. 11 is a schematic diagram of flip-chip bonding in a common GaN-based LED package.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a Micro-LED array and a preparation method thereof, which can realize the gold-free encapsulation of the Micro-LED array.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a structural diagram of an embodiment of a Micro-LED array of the present invention. Referring to FIG. 1 , the Micro-LED array includes a silicon substrate 101 , a metal substrate 102 , and a plurality of identical light-emitting chips located between the silicon substrate 101 and the metal substrate 102 .

The light-emitting chips are arranged in an array between the silicon substrate 101 and the metal substrate 102 .

The light-emitting chip is provided with metal contacts 103, p-type gallium nitride layer 104, multiple quantum well layer 105 and n-type gallium nitride layer 106 in sequence from bottom to top; wherein, the silicon substrate 101 is provided with wirings, and the The metal contact 103 is electrically interconnected with the silicon substrate 101 through the wiring, and the metal substrate 102 is disposed on the n-type gallium nitride layer 106 .

The metal contact 103 is made of gold or nickel/gold alloy.

The metal substrate 102 is a copper substrate.

The multiple quantum well layer 105 is a multi-layer quantum well, which mainly improves the recombination efficiency of holes and electrons. To a certain extent, the more quantum wells, the higher the recombination efficiency, and the higher the recombination efficiency, the higher the luminous efficiency.

The metal contact 103 is used as the p-electrode of the light-emitting chip, the metal contact 103 is used to generate holes, and the p-type gallium nitride layer 104 is used to transmit the holes; the metal substrate 102 is used as a For the n-electrode of the light-emitting chip, the metal substrate 102 is used for generating the electrons; the n-type gallium nitride layer 106 is used for transmitting the electrons; the multiple quantum well layer 105 is used for the electrons and the electrons. The holes are recombined to generate photons; when the silicon substrate 101 is energized, current flows from the metal contacts 103 to the metal substrate 102 to realize the light emission of the Micro-LED array.

In this embodiment, the Micro-LED array is composed of 2*2 chips. FIG. 1 shows a 2*2 gold-free packaged Micro-LED array. After confirming that the Micro-LED array is 2*2, on the silicon substrate 101 2*2 array wiring is performed on it.

Taking the Micro-LED array composed of 2*2 chips as an example, after confirming that the Micro-LED array is 2*2, the wiring of the 2*2 array is performed on the silicon substrate. On the sapphire substrate by MOCVD method, a p-type gallium nitride layer, a multi-quantum well layer and an n-type gallium nitride layer are sequentially grown as the epitaxial layer of the Micro-LED. After the epitaxial layer is grown, the evaporation deposition method is used first. Metal deposition is performed on the p-type gallium nitride layer of each chip of the Micro-LED array to form metal contacts, corresponding to the 2*2 wiring on the silicon substrate. After flip-chipping the Micro-LED array, the metal contacts of the array are bonded to the silicon substrate using a thermocompression welding process to achieve electrical interconnection. If the silicon substrate is not used for wiring connections, it is necessary to make gold wires on a single chip to achieve electrical interconnection. The function of electrical interconnection is to achieve power-on, without electrical interconnection, the chip cannot work normally, and in the prior art, under normal circumstances, it can only be achieved by gold wire, and gold wire belongs to the LED packaging stage. Wiring and bonding multiple metal contacts on the substrate, and then forming a circuit with the metal substrate to realize light emission, the packaging of Micro-LED array can be realized without gold wire, using the high temperature decomposition characteristics of GaN material and the band between GaN and sapphire Gap difference, using ultraviolet pulsed laser with photon energy greater than the GaN band gap but smaller than the sapphire band gap, irradiating the GaN material through the sapphire substrate, resulting in strong absorption at its interface, increasing the local temperature, and GaN gasification and decomposition. The sapphire substrate is peeled off, and the GaN epitaxial wafer (n-type gallium nitride layer) is bonded to the transfer substrate metal substrate by wafer bonding, and the GaN material is combined with the metal substrate by hot pressing. The temperature is 300-500°C, and the entire Micro-LED array can share the n-electrode (Micro-LED array, that is, 2*2 chips share the n-electrode, that is, the metal substrate), so as to realize the gold-free package of the Micro LED array.

FIG. 2 is a flow chart of an embodiment of a method for preparing a Micro-LED array of the present invention. Referring to Figure 2, the preparation method of the Micro-LED array includes:

Step 201: Simultaneously grow a plurality of identical light-emitting chips on the sapphire substrate 107; the light-emitting chips are sequentially grown with an n-type gallium nitride layer 106, a multiple quantum well layer 105, a p-type gallium nitride layer 104 and metal contacts. The chip of point 103 , wherein the n-type gallium nitride layer 106 is grown on the sapphire substrate 107 .

In this step 201, the growth step of the light-emitting chip specifically includes:

The n-type gallium nitride layer 106 is grown on the sapphire substrate 107 .

The multiple quantum well layer 105 is grown on the n-type gallium nitride layer 106 .

The p-type gallium nitride layer 104 is grown on the multiple quantum well layer 105 .

Metal deposition is performed on the p-type gallium nitride layer 104 to form the metal contacts 103 .

Wherein, performing metal deposition on the p-type gallium nitride layer 104 to form the metal contacts 103 specifically includes:

Metal deposition is performed on the p-type gallium nitride layer 104 by deposition method, sputtering method or electroplating method to form the metal contact 103 .

When the light-emitting chips are grown, the thickness and size of each layer of the light-emitting chips are controlled by changing the temperature and material concentration during the reaction. It is a conventional practice to grow one type of layer on the sapphire substrate at the same time. process, the interval and block between the same layers of each of the light-emitting chips can be controlled.

Step 202 : According to the positions of the metal contacts 103 on the sapphire substrate 107 , the wirings corresponding to the metal contacts 103 are arranged on the silicon substrate 101 .

In step 202, the distribution of the Micro-LED array is determined first, that is, the position of each metal contact in the Micro-LED array is determined, and then the wiring consistent with the distribution of the Micro-LED array is performed on the silicon substrate.

Step 203: Invert the sapphire substrate 107 on which the light-emitting chip is grown, and bond the inverted sapphire substrate 107 to the silicon substrate 101 through the metal contacts 103 and the wiring to obtain a bond combined array.

FIG. 3 is a schematic diagram of a single structural unit of the bonding array of the present invention. Referring to FIG. 3 , if the bonding array is cut, a plurality of identical structural units as shown in FIG. 3 can be obtained.

In this step 203, the inverting sapphire substrate 107 is bonded to the silicon substrate 101 through the metal contacts 103 and the wiring, which specifically includes:

The inverted sapphire substrate 107 is bonded to the silicon substrate 101 through the metal contacts 103 and the wiring using thermal pressure flip-chip bonding, ultrasonic thermal compression bonding or conductive adhesive.

During bonding, according to the distribution of the Micro-LED array (the positions of the metal contacts in the Micro-LED array), the metal contacts are aligned with the wiring on the silicon substrate before bonding.

Step 204 : peel off the sapphire substrate 107 on the bonding array, and then bond the metal substrate 102 to each of the n-type gallium nitride layers 106 .

In this step 204, the peeling off the sapphire substrate 107 on the bonding array specifically includes:

The sapphire substrate 107 on the bonding array is peeled off using a laser lift-off technique.

In this embodiment, a copper substrate is used as the metal substrate. After the sapphire substrate 107 is peeled off, the Micro-LED array is transferred to a copper substrate with better thermal conductivity and electrical conductivity using bonding technology, and the entire array shares n electrodes. .

For Micro-LED, since the general metal wire bonding method cannot be used to combine with the substrate, it is more suitable to use a flip-chip structure, which can better meet the requirements of small size and miniaturization of Micro-LED display. The invention aims to prepare metal contacts from the p-type gallium nitride layer of the MicroLED array, perform wiring corresponding to the Micro-LED array on a silicon substrate, and then use a hot-press welding process to connect the p-electrode surface of the array to the silicon substrate. The sapphire substrate is removed by laser lift-off technology, and the metal substrate is bonded to the n-type gallium nitride layer by bonding technology, and the p and n electrodes are located in the epitaxial layer (the p electrode, n The part of the electrode and the substrate is called epitaxial layer, in the present invention, it refers to the two sides of the p-type gallium nitride layer, the multiple quantum well layer and the n-type gallium nitride layer), so as to realize the gold-free packaging of the Micro-LED array.

Because the chip of Micro-LED is too small, it is difficult to perform gold wire bonding process for Micro-LED with positive structure. The present invention provides a solution method for electrical interconnection of a Micro-LED array using a gold-free wire bonding process. While solving the problem of the bonding process, the heat dissipation efficiency is improved and the problem of current crowding is solved. The gold wire bonding process of the present invention is mainly divided into two steps, one is to invert the array and bond with the silicon substrate, and the other is to peel off the sapphire substrate and transfer the array to a metal substrate with excellent electrical conductivity and thermal conductivity. The top is used as the n-electrode to realize electrical interconnection. In this way, the metal contact as the p-electrode and the metal substrate as the n-electrode are designed on both sides of the epitaxial layer, which also improves the problem of current crowding, thereby solving the problem of gold wire bonding in the Micro-LED array.

FIG. 4 , FIG. 5 and FIG. 6 are schematic diagrams of a front-mounted structure, a vertical structure and a flip-chip structure in a common GaN-based LED package structure, respectively. Among them, the vertical structure is divided into two types, one is that the p-electrode and the n-electrode are respectively distributed on the upper top surface and the lower bottom surface of the LED structure, as shown in FIG. 7 . The other is that the p-electrode and the n-electrode are distributed on the lower bottom surface and the upper top surface of the LED structure, respectively, as shown in FIG. 8 . The conventional ordinary front-mounted LED structure, the n-type gallium nitride layer is in contact with the sapphire substrate, the sapphire substrate has high hardness, and low thermal conductivity and electrical conductivity. After encapsulating the Micro-LED array, after flipping the Micro-LED, the p-type gallium nitride layer is in contact with the silicon substrate, the contact surface is replaced with a p-type gallium nitride layer, the sapphire substrate is replaced with a silicon substrate, and the thermal The resistance is much smaller than that of the sapphire substrate, which solves the problem of heat dissipation and improves the heat dissipation efficiency. In addition, since the sapphire substrate is peeled off after flip-chip, the array is transferred to a metal substrate with better electrical conductivity and thermal conductivity. The entire array shares n electrodes, so that the p and n electrodes are located on both sides of the epitaxial layer, and the current flows almost vertically. Through the epitaxial layer, very little current flows laterally, solving the problem of current crowding.

FIG. 9 , FIG. 10 and FIG. 11 are a schematic diagram of a front-mounted structure gold wire bonding, a vertical structure gold wire bonding schematic diagram, and a flip-chip structure bonding schematic diagram, respectively, in a common GaN-based LED package. Since the mainstream Micro-LED arrays in the market mostly adopt the front-mounted structure, and the Micro-LED chips are too small, it is too difficult and inefficient to perform gold wire bonding operations on a single chip. Then, the entire array is transferred to the metal substrate, and the entire Micro-LED array shares the n-electrode, realizing the gold-free packaging of the Micro-LED array.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other.

In this paper, specific examples are used to illustrate the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the device and the core idea of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (6)

1. A Micro-LED array, characterized in that it comprises a silicon substrate, a metal substrate, and a plurality of identical light-emitting chips located between the silicon substrate and the metal substrate; The light-emitting chip is provided with metal contacts, p-type gallium nitride layer, multiple quantum well layer and n-type gallium nitride layer in sequence from bottom to top; wherein, wiring is provided on the silicon substrate, and the metal contacts pass through all the the wiring is electrically interconnected with the silicon substrate, and the metal substrate is arranged on the n-type gallium nitride layer; The metal contact is used as the p-electrode of the light-emitting chip, the metal contact is used to generate holes, and the p-type gallium nitride layer is used to transmit the holes; the metal substrate is used as the light-emitting chip the n-electrode, the metal substrate is used to generate electrons; the n-type gallium nitride layer is used to transmit the electrons; the multiple quantum well layer is used to recombine the electrons and the holes to generate photons When the silicon substrate is energized, the current flows from the metal contacts to the metal substrate to realize the light emission of the Micro-LED array; by preparing the metal contacts from the p-type gallium nitride layer of the Micro LED array, the silicon substrate The wiring corresponding to the Micro-LED array is carried out on the top, and then the p-electrode surface of the array is bonded to the silicon substrate by a hot-press welding process to realize electrical interconnection; the sapphire substrate is removed by laser lift-off technology, and the metal substrate is bonded by bonding technology. It is bonded to the n-type gallium nitride layer, and the p and n electrodes are located on both sides of the epitaxial layer, so as to realize the gold-free packaging of the Micro-LED array; The metal substrate is a copper substrate. 2 . The Micro-LED array according to claim 1 , wherein the light-emitting chips are arranged in an array between the silicon substrate and the metal substrate. 3 . 3 . The Micro-LED array of claim 1 , wherein the metal contacts are made of gold or nickel/gold alloy. 4 . 4. A preparation method applied to the Micro-LED array according to any one of claims 1-3, characterized in that, comprising: A plurality of identical light-emitting chips are simultaneously grown on a sapphire substrate; the light-emitting chips are chips sequentially grown with an n-type gallium nitride layer, a multiple quantum well layer, a p-type gallium nitride layer and metal contacts, wherein the The n-type gallium nitride layer is grown on a sapphire substrate; According to the positions of the metal contacts on the sapphire substrate, wirings corresponding to the metal contacts are arranged on the silicon substrate; inverting the sapphire substrate on which the light-emitting chip is grown, and bonding the inverted sapphire substrate to the silicon substrate through the metal contacts and the wiring to obtain a bonding array; The sapphire substrate on the bonding array is peeled off, and then the metal substrate is bonded to each of the n-type gallium nitride layers; metal contacts are prepared by preparing the p-type gallium nitride layer of the Micro LED array, and the silicon The wiring corresponding to the Micro-LED array is carried out on the substrate, and then the p-electrode surface of the array and the silicon substrate are bonded to realize electrical interconnection by the hot-press welding process; the sapphire substrate is removed by laser lift-off technology, and the metal is separated by bonding technology. The substrate is bonded to the n-type gallium nitride layer, and the p and n electrodes are located on both sides of the epitaxial layer, thereby realizing the gold-free packaging of the Micro-LED array; On the sapphire substrate by MOCVD method, a p-type gallium nitride layer, a multi-quantum well layer and an n-type gallium nitride layer are sequentially grown as the epitaxial layer of the Micro-LED. The p-type gallium nitride layer of each chip of the Micro-LED array is metal-deposited to form metal contacts. 5. The preparation method according to claim 4, wherein the growth step of the light-emitting chip specifically comprises: growing the n-type gallium nitride layer on the sapphire substrate; growing the multiple quantum well layer on the n-type gallium nitride layer; growing the p-type gallium nitride layer on the multiple quantum well layer; Metal deposition is performed on the p-type gallium nitride layer to form the metal contacts. 6 . The preparation method according to claim 4 , wherein the bonding of the inverted sapphire substrate to the silicon substrate through the metal contacts and the wiring comprises: 6 . The inverted sapphire substrate is bonded to the silicon substrate through the metal contacts and the wiring by using thermal pressure flip-chip welding or ultrasonic thermal pressure welding.

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