CN116404027A - Micro-LED Micro display and preparation method thereof - Google Patents

Abstract

The invention discloses a Micro-LED Micro display and a preparation method thereof. The redistribution layer RDL includes an anode, a cathode, and a metal casing: the anodes are metal lattices which are distributed independently, the cathodes are a series of metal strips with the same row number or column number as that of the anode metal lattices, and all the cathode metal strips are connected to a metal outer frame outside the pixel array to form common cathode connection; the p-type ohmic electrodes of the Micro-LED chips and the anode metal lattices of the RDL form bonding connection in a one-to-one correspondence mode, and the n-type ohmic electrodes of the Micro-LED chips and the cathode metal strips of the RDL form bonding connection. According to the invention, the redistribution layer RDL is designed on the CMOS driving substrate, and the Micro-LED chip array is integrated on the CMOS driving substrate, so that a Micro-display is formed, and the Micro-display structure can reduce the difficulty of passivation and electrode wiring process after the n-GaN layer is carved in the manufacturing process of the Micro-LED chip.

Description

A kind of Micro-LED microdisplay and preparation method thereof

technical field

The invention relates to the field of semiconductor display devices, in particular to a Micro-LED microdisplay and a preparation method thereof.

Background technique

Microdisplay is an essential component for the preparation of new smart devices such as VR/AR. Existing microdisplays based on technologies such as liquid crystal on silicon (LCoS) and organic light-emitting diodes (OLED) have poor performance in terms of brightness, power consumption, and reliability. It still cannot meet the application requirements. Micro-LED has the advantages of high luminous efficiency, high current resistance, stability and reliability, and is an ideal solution for preparing VR/AR microdisplays. However, due to the very small pixel size of the Micro-LED, it is very difficult to prepare the LED into a uniform and reliable pixel array and achieve high reliability integration with the CMOS driver substrate, the manufacturing yield is low, the cost is high, and it is difficult to achieve colorization .

In order to reduce manufacturing difficulty, a common process route is: use a transparent sapphire substrate to grow a blue GaN-based LED epitaxial structure, form a Micro-LED mesa array by etching, but keep n-GaN continuous. A p-type ohmic electrode is prepared on each Micro-LED chip and connected to the pixel of the CMOS driving substrate by parasite bonding, and n-GaN is connected to the cathode of the CMOS driving substrate as a common cathode. In this way, the addressing control of each Micro-LED chip can be realized to generate a display image. This solution is relatively simple to implement, but one of its disadvantages is that the sapphire substrate is transparent and has a strong optical waveguide effect, which brings serious optical crosstalk problems. In order to reduce optical crosstalk, an improved solution is to keep n-GaN continuous, but use laser lift-off to remove the sapphire substrate after para-bonding. Although this solution can reduce optical crosstalk, because n-GaN is still a continuous layer, the optical waveguide effect still exists. Moreover, since the layer is only a few microns thick and the width is on the order of several millimeters or even centimeters, cracks are prone to occur in processes such as laser lift-off, resulting in low manufacturing yield. In order to solve the above problems, it is necessary to cut off the n-GaN layer to produce individual Micro-LED chips, but cutting off the n-GaN layer will cause unevenness between adjacent Micro-LED chips, and then The passivation and electrode wiring processes of Micro-LED chips are extremely difficult.

Contents of the invention

The first object of the present invention is to provide a Micro-LED microdisplay, which adopts an independent n-GaN mesa structure to avoid the problems of optical crosstalk and n-GaN layer cracking.

The second object of the present invention is to provide a method for preparing a Micro-LED microdisplay. The preparation method designs a redistribution layer RDL on a CMOS drive substrate, and uses the redistribution layer RDL to connect the Micro-LED chip array with the CMOS driver. The substrates are connected to realize the display function of the Micro-LED, and reduce the difficulty of the passivation process and the electrode wiring process after cutting the n-GaN layer during the manufacturing process of the Micro-LED chip.

First purpose of the present invention is achieved like this:

A Micro-LED microdisplay comprising:

(1) A CMOS drive substrate, including an array of pixels that can be independently addressed and controlled, and common electrodes distributed outside the pixel area;

(2) The redistribution layer RDL (Re-distributed Layer) formed on the CMOS drive substrate;

(3) A Micro-LED chip array connected to the pixel array on the CMOS drive substrate through the redistribution layer RDL;

Features are:

There is an insulating layer on the surface of the CMOS driving substrate, and a series of through holes are opened on the insulating layer, thereby exposing the metal electrodes of the pixel array in the CMOS driving substrate;

The redistribution layer RDL includes an anode, a cathode, and a metal frame outside the pixel array, wherein: the anode is an independently distributed metal lattice, and the metal lattice is electrically connected to the CMOS circuit through the through holes on the insulating layer; The cathode is a series of metal strips, the number of rows or columns of the cathode is the same as the number of rows or columns of the anode metal lattice, and all the cathode metal strips are connected to the metal frame outside the pixel area; the said The metal frame has two functions, one is to connect all the cathode metal strips to form a common cathode connection; the other is to ensure the alignment accuracy of the Micro-LED chip array and the pixel array of the CMOS drive substrate;

Among them, the Micro-LED chip array is made of GaN-based semiconductor materials, and the GaN-based semiconductor layers of each chip are independent of each other and not connected to each other.

Preferably, the anode material in the redistribution layer RDL preferably uses several combinations of Cr, Pt, In, Sn, Au, and the cathode material also preferably uses several combinations of Cr, Pt, In, Sn, Au; in order to ensure The anode and the cathode are easy to form a bonding connection, and the outermost layer of the anode and the cathode is preferably metal Au without an oxide layer and easy to soften, and the thickness of the Au layer is not less than 500nm. Further, the surface height difference between the anode, the cathode and the metal frame is not more than 100 nm.

Further, a protective layer is also provided on the surface of the insulating layer of the CMOS driving substrate to protect the CMOS driving substrate from being damaged by the subsequent process, thereby improving the reliability of the device; in order to make the protective layer have good process tolerance, The protective layer is an organic curable material, preferably polyimide photoresist or SU-8 photoresist.

Further, each chip in the Micro-LED chip array sequentially includes an n-GaN layer, a p-GaN layer, and an InGaN/GaN quantum well light-emitting layer sandwiched between the n-GaN layer and the p-GaN layer.

Further, an n-type ohmic electrode is provided on the n-GaN layer of each Micro-LED chip, and a p-type ohmic electrode is provided on the p-GaN layer; wherein, the n-type ohmic electrode and the p-type ohmic electrode are distributed on the Micro-LED chip. - LED chip on the same side; preferably, the surface layer of the n-type ohmic electrode and the p-type ohmic electrode of the Micro-LED chip is an Au layer with a thickness not less than 500nm, and the surface heights of the n-type ohmic contact and the p-type ohmic electrode are different Not greater than 200nm;

Further, a layer of metal bonding laminate is also prepared on the n-type ohmic electrode and the p-type ohmic electrode of each Micro-LED chip, and the difference in surface height between the n-type ohmic electrode and the p-type ohmic electrode is not more than 200nm; The role of the metal bonding stack is to connect the Micro-LED chip array with the redistribution layer RDL to form a current channel, and to fix the Micro-LED chip on the CMOS drive substrate. In order to make this layer of metal bonded laminates not easily damaged during subsequent processing, they preferably use chemically resistant metals such as Cr, Pt, In, Sn, Au; and in order to ensure that these metals are easy to form bonding connections, The metal whose melting point is higher than the bonding temperature should be selected, and the outermost layer of the metal bonding laminate is preferably the metal Au which has no oxide layer and is easy to soften, and the thickness of the Au layer is not less than 500nm. At the same time, in order to ensure the alignment accuracy between the Micro-LED chip array and the pixel array of the CMOS drive substrate, a metal inner frame is prepared around the Micro-LED chip array, and the height of the metal inner frame is the same as the height of the metal bonded laminate. The height difference is not greater than 200nm, and the width of the metal inner frame should not be less than three times the width of the metal bonded laminate.

Further, the p-type ohmic electrode of the Micro-LED chip and the anode metal lattice of the redistribution layer RDL form a one-to-one correspondence to form a bonding connection, while the n-type ohmic electrode of the Micro-LED chip forms a bond connection with the cathode metal strip of the redistribution layer RDL. bonded connection.

Further, the Micro-LED chip array includes red, green and blue Micro-LED chips.

Second purpose of the present invention is achieved like this:

A method for preparing a Micro-LED microdisplay, comprising the following steps:

(1) Grow GaN-based red/green/blue LED epitaxial structures on silicon substrates; wherein, LED epitaxial structures include n-GaN layers, p-GaN layers, and n-GaN layers, p-GaN layers sandwiched between InGaN/GaN quantum well light-emitting layer;

(2) Make a LED epitaxial structure of one color into multiple Micro-LED chips. The specific steps are: first use the dry etching process to etch the p-GaN layer and the InGaN/GaN quantum well layer in some areas of the LED epitaxial structure. The n-GaN layer is etched and removed to expose the n-GaN layer to form a p-GaN mesa structure; then the n-GaN layer between the p-GaN mesa structures is etched by dry etching to form a trench exposing the silicon substrate, LED epitaxial frame and each independent Micro-LED chip; the width between the grooves is not less than the width of the p-GaN mesa structure of the Micro-LED chip;

(3) Prepare a p-type ohmic electrode on each p-GaN mesa structure, and prepare an n-type ohmic electrode on the n-GaN layer next to each p-GaN mesa structure;

(4) Preparing metal bonding laminates on n-type ohmic electrodes, p-type ohmic electrodes and LED epitaxial frames;

(5) In the etching step (2), the depth of the groove of the silicon substrate is greater than the thickness of the GaN-based LED epitaxial structure;

(6) Passivate the Micro-LED chip array, the material of the passivation layer is nitride or oxide containing Si, Al; or the material of the passivation layer is curable photoresist, such as polyimide Photoresist, SU-8 photoresist;

(7) Etching a CMOS drive substrate covered with an insulating layer to form a through-hole array;

(8) Prepare a redistribution layer RDL on the CMOS drive substrate after the hole is opened. The redistribution layer RDL includes an anode, a cathode, and a metal frame outside the pixel array, where the anode is an independently distributed metal point The metal lattice is electrically connected to the CMOS drive substrate through the through holes on the insulating layer; the cathode is a series of metal strips, the number of rows or columns of the cathode is the same as the number of rows or columns of the anode lattice The same, and all cathode metal strips are connected to the metal frame outside the pixel array;

(9) Spin-coat a layer of curable photoresist on the surface of the CMOS drive substrate with the redistribution layer RDL prepared, and remove the photoresist on the surface of the redistribution layer RDL and the surface of the pad area on the CMOS drive substrate by photolithography , and then cure the photoresist to protect the CMOS drive substrate from being damaged in the subsequent process; the curable photoresist is polyimide photoresist, SU-8 photoresist;

(10) Parasite-bond the Micro-LED chip array of one color obtained in steps (1)-(6) with the CMOS driver substrate with redistribution layer RDL obtained in steps (7)-(9), Connect the p-type ohmic electrode of each Micro-LED chip in the Micro-LED chip array to the anode metal point of the redistribution layer RDL, and connect the n-type ohmic electrode of each Micro-LED chip to the cathode metal strip of the redistribution layer RDL ;

(11) Remove the silicon substrate used for the epitaxial growth of Micro-LED chips; obtain a monochrome Micro-LED microdisplay;

(12) Repeat steps (10) and (11) with the second color Micro-LED chip array obtained in steps (1)-(6), and ensure that the bonding point is staggered from the first bonding point ;

(13) Repeat steps (10) and (11) with the third color Micro-LED chip array obtained in steps (1)-(6), and ensure that the bonding points are the same as the first and second times The bonding points are staggered; a full-color Micro-LED microdisplay is obtained.

Furthermore, the connection between the Micro-LED chip array and the CMOS drive substrate prepared with the redistribution layer RDL is realized by thermocompression bonding by alignment bonding, in which the n-type ohmic electrode of the Micro-LED chip is connected to the redistribution layer. The cathode of the RDL layer is connected, the p-type ohmic electrode is connected to the anode of the redistribution layer RDL, and the bonding interface is Au/Au; at the same time, the metal inner frame around the Micro-LED chip array is in contact with the metal outer frame in the redistribution layer RDL To ensure the alignment accuracy of the Micro-LED chip array and the pixel array of the CMOS drive substrate.

In the present invention, by designing the redistribution layer RDL on the CMOS driving substrate, the Micro-LED chip array is integrated on the CMOS driving substrate, thereby forming a microdisplay; the structure of this microdisplay can reduce the n- The difficulty of passivation and electrode wiring process after the GaN layer is cut, and the silicon substrate of the Micro-LED chip is easier to remove than the sapphire substrate, and there is no need to use complex and difficult mass transfer technology, so that the present invention can achieve full-color The display method is simpler and more reliable.

Description of drawings

Figure 1 is a schematic diagram of the preparation process of the monochrome Micro-LED chip array provided by the embodiment of the present invention;

FIG. 2 is a schematic flow diagram of preparing a redistribution layer RDL on a CMOS drive substrate provided by an embodiment of the present invention;

Fig. 3 is a three-dimensional schematic flow chart for preparing a redistribution layer RDL provided by an embodiment of the present invention;

Fig. 4 is a schematic flow diagram of integrating a single-color Micro-LED chip array into a CMOS drive substrate provided by an embodiment of the present invention;

Fig. 5 is a schematic diagram of the preparation process of the red Micro-LED chip array provided by the embodiment of the present invention;

Fig. 6 is a schematic diagram of the preparation process of the green Micro-LED chip array provided by the embodiment of the present invention;

Fig. 7 is a schematic diagram of the preparation process of the blue light Micro-LED chip array provided by the embodiment of the present invention;

FIG. 8 is a schematic flow diagram of preparing a redistribution layer RDL on a CMOS drive substrate according to an embodiment of the present invention;

FIG. 9 is a schematic flow diagram of integrating red/green/blue Micro-LED chip arrays into a CMOS drive substrate provided by an embodiment of the present invention;

FIG. 10 is a schematic structural diagram of a full-color Micro-LED microdisplay with chips of different sizes provided by an embodiment of the present invention;

FIG. 11 is a schematic structural diagram of another full-color Micro-LED microdisplay with chips of different sizes provided by an embodiment of the present invention.

Detailed ways

In order to facilitate those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings.

Example 1:

A method for preparing a monochrome Micro-LED microdisplay, comprising the following three contents:

A, as shown in Figure 1, a method for preparing a single-color Micro-LED chip array, comprising the following steps:

Step S1 , growing an LED epitaxial structure 110 on the surface of the silicon substrate 101 . Wherein, the LED epitaxial structure 110 includes an n-GaN layer 111, a p-GaN layer 113, and an InGaN/GaN quantum well light-emitting layer 112 sandwiched between the n-GaN layer 111 and the p-GaN layer 113;

In step S2 , the LED epitaxial structure 110 is fabricated into a plurality of Micro-LED chips 115 by standard semiconductor manufacturing process. The specific steps are as follows: remove the redundant part of the LED epitaxial structure 110 by etching or other material removal techniques, thereby exposing part of the n-GaN layer 111, the p-GaN layer 113 and an LED epitaxial frame 114, so that the remaining LED epitaxial structure 110 On the silicon substrate 101, a plurality of independent structures with a size of about 10 microns and arranged at intervals are formed; then an n-type ohmic electrode 150 is prepared on the n-GaN layer 111, and an n-type ohmic electrode 150 is prepared on the p-GaN layer 113 and the LED epitaxial frame 114 Prepare a p-type ohmic electrode 160 on it; in this way, a complete Micro-LED chip 115 can be formed, and each independent structure will eventually form a Micro-LED chip 115;

Step S3, preparing a metal bonding laminate 170 on the n-type ohmic electrode 150 and the p-type ohmic electrode 160 of the Micro-LED chip 115 by metal deposition technology;

In step S4 , the Micro-LED chip 115 is passivated by thin film preparation technology, and the passivation layer is 180 .

B, as shown in Figure 2 and Figure 3, a method for preparing a CMOS drive substrate with a redistribution layer RDL, comprising the following steps:

Step S1, using a standard semiconductor process to open the insulating layer 201 of the CMOS driving substrate 200, exposing the metal lattice 202 of the pixel area 210 and the metal frame 203 of the non-pixel area 220 of the CMOS driving substrate 200;

In step S2, a redistribution layer RDL is prepared on the CMOS driving substrate 200 after the hole is opened. The specific steps are as follows. Prepare independently distributed anode metal lattices 231 and a series of cathode metal strips with the same number of rows or columns as the number of rows or columns of the anode metal lattice 231 on the CMOS drive substrate 200 by metal deposition technology. 232 and metal frame 233. Wherein, the anode metal lattice 231 is electrically connected to the metal lattice 202 of the CMOS driving substrate 200, and all the cathode metal strips 232 are connected to the metal frame 233 outside the pixel area;

In step S3, passivation protection is performed on the CMOS drive substrate 200 prepared with the redistribution layer RDL, and a layer of protection layer 240 is prepared on the CMOS drive substrate 200 except for the redistribution layer RDL region and the I/O pad 204 region, so that A CMOS driving substrate 200 prepared with a redistribution layer RDL can be obtained.

C. As shown in Figure 4, a method for integrating a monochromatic Micro-LED chip array into a CMOS drive substrate prepared with a redistribution layer RDL, comprising the following steps:

Step S1, using an alignment bonding machine to integrate the Micro-LED chip 115 onto the CMOS drive substrate 200 prepared with the redistribution layer RDL. Wherein, the n-type ohmic electrode 150 of the Micro-LED chip 115 is connected to the cathode metal strip 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected to the anode metal lattice 231 of the redistribution layer RDL;

Step S2, removing the silicon substrate 101 of the Micro-LED chip 115 to obtain a single-color Micro-LED microdisplay.

Example 2:

A method for preparing a full-color Micro-LED microdisplay, comprising the following steps:

A. As shown in Figure 5, Figure 6 and Figure 7, a method for preparing a red/green/blue Micro-LED chip array includes but is not limited to the following steps:

Step S1 , growing an LED epitaxial structure 110 on the surface of the silicon substrate 101 . Wherein, the LED epitaxial structure 110 includes an n-GaN layer 111, a p-GaN layer 113, and red/green/blue InGaN/GaN quantum well light-emitting layers 122/132 sandwiched between the n-GaN layer 111 and the p-GaN layer 113. /142;

In step S2, the LED epitaxial structure 120/130/140 is fabricated into a plurality of red/green/blue Micro-LED chips 125/135/145 by using standard semiconductor manufacturing process. In a specific implementation, the excess part of the LED epitaxial structure 120/130/140 can be removed by etching or other material removal techniques, thereby exposing part of the n-GaN layer 111, the p-GaN layer 113 and a red/green/blue LED epitaxial structure. Block 124/134/144, so that the remaining epitaxial structure 120/130/140 forms a plurality of independent structures with a size of about 10 microns and arranged at intervals on the silicon substrate 101, that is, the n-GaN layer 111 is cut off ; Then prepare an n-type ohmic electrode 150 on the n-GaN layer 111, and prepare a p-type ohmic electrode 160 on the p-GaN layer 113 and the LED epitaxial frame 124/134/144; in this way, a complete red/green/blue light can be formed Micro-LED chip 125/135/145, each independent structure will eventually form a red/green/blue Micro-LED chip 125/135/145;

Step S3, preparing a metal bonding stack 170 on the n-type ohmic electrode 150 and the p-type ohmic electrode 160 of the red/green/blue Micro-LED chip 125/135/145 by metal deposition technology;

Step S4, remove the excess part of the silicon substrate 101 of the red/green/blue Micro-LED chips 125/135/145 by etching or other silicon material removal techniques, ensuring that the depth of the groove is greater than that of the GaN-based red/green/blue LED The thickness of the epitaxial structure, thereby obtaining the silicon trench 190;

In step S5, the red/green/blue Micro-LED chips 125/135/145 are passivated by thin film preparation technology, and the passivation layer is 180.

B. As shown in Figure 8, a method for preparing a CMOS drive substrate with a redistribution layer RDL, comprising the following steps:

Step S1, using a standard semiconductor process to open the insulating layer 201 of the CMOS driving substrate 200, exposing the metal lattice 202 of the pixel area 210 and the metal frame 203 of the non-pixel area 220 of the CMOS driving substrate 200;

In step S2, a redistribution layer RDL is prepared on the CMOS driving substrate 200 after the hole is opened. The specific steps are as follows. Prepare independently distributed anode metal lattices 231 and a series of cathode metal strips with the same number of rows or columns as the number of rows or columns of the anode metal lattice 231 on the CMOS drive substrate 200 by metal deposition technology. 232. Wherein, the anode metal lattice 231 is electrically connected to the metal lattice 202 of the CMOS driving substrate 200, and all the cathode metal strips 232 are connected to the metal frame 233 outside the pixel area;

In step S3 , passivation protection is performed on the CMOS driving substrate 200 prepared with the redistribution layer RDL, and a protective layer 240 is prepared on the CMOS driving substrate 200 except for the RDL region and the I/O pad 204 region. In this way, the CMOS driving substrate 200 prepared with the redistribution layer RDL can be obtained.

C, as shown in Figure 9, a method for integrating red/green/blue Micro-LED chip arrays on a CMOS drive substrate prepared with a redistribution layer RDL, comprising the following steps:

Step S1, using an alignment bonding machine to integrate the red Micro-LED chip 125 onto the CMOS drive substrate 200 prepared with the redistribution layer RDL. Wherein, the n-type ohmic electrode 150 of the red Micro-LED chip 125 is connected to the cathode metal strip 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected to the anode metal lattice 231 of the redistribution layer RDL;

Step S2, removing the silicon substrate 101 of the red Micro-LED chip 125;

Step S3, using an alignment bonding machine to integrate the green Micro-LED chip 135 onto the CMOS drive substrate 200 prepared with the redistribution layer RDL. Wherein, the n-type ohmic electrode 150 of the green Micro-LED chip 135 is connected to the cathode metal strip 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected to the anode metal lattice 231 of the redistribution layer RDL;

Step S4, removing the silicon substrate 101 of the green Micro-LED chip 135;

Step S5 , using an alignment bonding machine to integrate the blue Micro-LED chip 145 onto the CMOS drive substrate 200 prepared with the redistribution layer RDL. Wherein, the n-type ohmic electrode 150 of the blue Micro-LED chip 145 is connected to the cathode metal strip 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected to the anode metal lattice 231 of the redistribution layer RDL;

Step S6 , removing the silicon substrate 101 of the blue Micro-LED chip 145 .

As shown in Figure 10 and Figure 11, a full-color Micro-LED microdisplay is thus obtained.

It should be noted that, the above-mentioned method for preparing a single-color or full-color Micro-LED microdisplay of the present invention does not require the steps to be completed in the order listed, and the order can be appropriately adjusted according to the conditions of the equipment used. . The present invention has no special limitation on GaN growth and etching conditions, and the bonding temperature and pressure can also be appropriately adjusted according to specific equipment conditions or the experience usually possessed by those skilled in the art. These adjustments also belong to the protection scope of the technical solution of the present invention.

Further, the size of the Micro-LED chip in the embodiment of the present invention is about "10 microns" only as an example size, and does not constitute a specific limitation on the size of the Micro-LED chip. Generally speaking, the size of Micro-LED chips can reach between 1 and 50 μm. Those skilled in the art can determine the corresponding semiconductor manufacturing process according to the common size range of Micro-LED chips, which is not limited in this application.

The above embodiments are only used to illustrate the design concept and characteristics of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims (9)

1. A Micro-LED microdisplay, comprising: (1) A CMOS drive substrate, including an independently addressable and controllable pixel array, and common electrodes distributed outside the pixel area; (2) The redistribution layer RDL formed on the CMOS drive substrate; (3) Micro-LED chip array connected to the pixel array on the CMOS drive substrate through RDL; It is characterized by: There is an insulating layer on the surface of the CMOS drive substrate, and a series of through holes are opened on the insulating layer; The redistribution layer RDL includes an anode, a cathode, and a metal frame, wherein the anode is an independently distributed metal lattice, and the metal lattice is electrically connected to the CMOS circuit through the holes on the insulating layer; the The cathode is a metal strip, the number of rows or columns is the same as the number of rows or columns of the anode metal lattice, and all the cathode metal strips are connected to the metal frame outside the pixel area; Wherein, the Micro-LED chip array is made of GaN-based semiconductor materials, and the GaN-based semiconductor layers of each chip are independent of each other and not connected to each other. 2. The Micro-LED microdisplay according to claim 1, characterized in that: the surface layer of the redistribution layer RDL is an Au layer with a thickness not less than 500 nm, and the surface height of the anode, cathode and metal frame The difference is not more than 100nm. 3. The Micro-LED microdisplay according to claim 1 or 2, characterized in that: the n-type ohmic electrode and the p-ohmic electrode of each Micro-LED chip are distributed on the same side of the Micro-LED chip; The surface layer of the n-type ohmic electrode and the p-type ohmic electrode of the Micro-LED chip is an Au layer with a thickness of not less than 500nm, and the difference between the surface heights of the n-type ohmic contact and the p-type ohmic electrode is not more than 200nm; wherein the Micro-LED The p-type ohmic electrode of the chip forms a one-to-one bond connection with the anode metal lattice of the RDL, while the n-type ohmic electrode of the Micro-LED chip forms a bond connection with the cathode metal strip of the RDL. 4. The Micro-LED microdisplay according to claim 1, wherein the Micro-LED chip array includes red, green and blue Micro-LED chips. 5. A preparation method for a Micro-LED microdisplay, comprising the following steps: (1) Grow GaN-based red/green/blue LED epitaxial structures on silicon substrates; wherein, LED epitaxial structures include n-GaN layers, p-GaN layers, and n-GaN layers, p-GaN layers sandwiched between InGaN/GaN quantum well light-emitting layer; (2) Make a LED epitaxial structure of one color into multiple Micro-LED chips. The specific steps are: first use the dry etching process to etch the p-GaN layer and the InGaN/GaN quantum well layer in some areas of the LED epitaxial structure. The n-GaN layer is etched and removed to expose the n-GaN layer to form a p-GaN mesa structure; then the n-GaN layer between the p-GaN mesa structures is etched by dry etching to form a trench exposing the silicon substrate, LED epitaxial frame and each independent Micro-LED chip; the width between the grooves is not less than the width of the p-GaN mesa structure of the Micro-LED chip; (3) Prepare a p-type ohmic electrode on each p-GaN mesa structure, and prepare an n-type ohmic electrode on the n-GaN layer next to each p-GaN mesa structure; (4) Preparing metal bonding laminates on n-type ohmic electrodes, p-type ohmic electrodes and LED epitaxial frames; (5) Passivate the Micro-LED chip array to obtain a passivation layer; (6) Etching a CMOS drive substrate covered with an insulating layer to form a through-hole array; (7) Prepare a redistribution layer RDL on the CMOS drive substrate after the hole is opened. The redistribution layer RDL includes an anode, a cathode, and a metal frame outside the pixel array, where the anode is an independently distributed metal point The metal lattice is electrically connected to the CMOS drive substrate through the through holes on the insulating layer; the cathode is a series of metal strips, the number of rows or columns of the cathode is the same as the number of rows or columns of the anode lattice The same, and all cathode metal strips are connected to the metal frame outside the pixel array; (8) Spin-coat a layer of curable photoresist on the surface of the CMOS drive substrate with the redistribution layer RDL prepared, and remove the photoresist on the surface of the redistribution layer RDL and the surface of the pad area on the CMOS drive substrate by photolithography , and then cure the photoresist to protect the CMOS drive substrate from damage in subsequent processes; (9) Parasite bonding the Micro-LED chip array of one color obtained in steps (1)-(5) and the CMOS drive substrate prepared with the redistribution layer RDL obtained in steps (6)-(8), Connect the p-type ohmic electrode of each Micro-LED chip in the Micro-LED chip array to the anode metal point of the redistribution layer RDL, and connect the n-type ohmic electrode of each Micro-LED chip to the cathode metal strip of the redistribution layer RDL ; (10) Remove the silicon substrate used for the epitaxial growth of the Micro-LED chip; obtain a monochrome Micro-LED microdisplay. 6. The method for preparing a Micro-LED microdisplay according to claim 5, characterized in that: it comprises the following steps to prepare a full-color Micro-LED microdisplay: Repeat steps (1)-(5) three times to prepare Micro-LED arrays of three different colors; Repeat steps (9)-(10) three times, respectively perform alignment bonding of three different color Micro-LED arrays with the CMOS driver substrate with redistribution layer RDL obtained in steps (6)-(8) and remove the silicon substrate, and ensure that each bonding point is staggered from the previous bonding point. 7. The method for preparing Micro-LED microdisplays according to claim 6, characterized in that: when preparing the Micro-LED chip arrays of the second and third colors, before the passivation treatment in step (5), silicon The groove of the substrate is etched, and the etching depth is greater than the thickness of the GaN-based LED epitaxial structure. 8. The method for preparing a Micro-LED microdisplay according to claim 5, characterized in that: in step (5), the material of the passivation layer is a nitride or oxide containing Si and Al; or the material of the passivation layer The material is curable photoresist, such as polyimide photoresist, SU-8 photoresist. 9 . The method for preparing a Micro-LED microdisplay according to claim 5 , wherein in step (8), the curable photoresist is polyimide photoresist or SU-8 photoresist.

Images