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

Micro-LED Micro display and preparation method thereof Download PDF

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CN116404027A
CN116404027A CN202310475901.5A CN202310475901A CN116404027A CN 116404027 A CN116404027 A CN 116404027A CN 202310475901 A CN202310475901 A CN 202310475901A CN 116404027 A CN116404027 A CN 116404027A
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micro
led
layer
gan
metal
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王立
刘海荣
胡武民
徐龙权
丁杰
刘苾雨
全知觉
吴小明
王光绪
张建立
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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

Micro-LED Micro display and preparation method thereof
Technical Field
The invention relates to the field of semiconductor display devices, in particular to a Micro-LED Micro display and a preparation method thereof.
Background
The micro-display is an indispensable component for preparing novel intelligent equipment such as VR/AR, and the existing micro-display prepared based on technologies such as liquid crystal on silicon (LCoS), organic Light Emitting Diode (OLED) and the like cannot meet application requirements in the aspects of brightness, power consumption, reliability and the like. The Micro-LED has the advantages of high luminous efficiency, high-current-resistant operation, stability, reliability and the like, and is an ideal scheme for preparing the VR/AR Micro-display. However, since the pixel size of Micro-LEDs is very small, it is very difficult to prepare LEDs into a uniform and reliable pixel array and integrate them with CMOS drive substrates with high reliability, and it is difficult to realize colorization with low manufacturing yield and high cost.
In order to reduce the manufacturing difficulty, one common process route is as follows: and a transparent sapphire substrate is adopted to grow a blue GaN-based LED epitaxial structure, and a mesa array of Micro-LEDs is formed by etching, but n-GaN is kept continuous. One p-type ohmic electrode was prepared on each Micro-LED chip and connected by forming a connection to the pixels of the CMOS drive substrate by being aligned to bond the n-GaN as a common cathode to the cathode of the CMOS drive substrate. In this way, the addressing control of each Micro-LED chip can be implemented to generate a display image. This solution is simple to implement, but it has a disadvantage that the sapphire substrate is transparent and has a strong optical waveguide effect, which causes serious optical crosstalk problems. In order to reduce optical crosstalk, an improvement is: the n-GaN is still continuous, but the sapphire substrate is removed after para-bonding using a laser lift-off scheme. This approach can reduce optical crosstalk, but because n-GaN is still a continuous layer, the optical waveguide effect still exists. Moreover, since the layer is only a few micrometers thick and has a width on the order of a few millimeters or even centimeters, cracks easily occur in a laser lift-off process or the like, resulting in a low manufacturing yield. In order to solve the above problems, the n-GaN layer needs to be cut to manufacture individual Micro-LED chips, but the n-GaN layer is cut to cause uneven conditions between adjacent Micro-LED chips, which results in extremely difficult passivation of the Micro-LED chips and electrode wiring process.
Disclosure of Invention
It is a first object of the present invention to provide a Micro-LED Micro-display that adopts a structure of a separate n-GaN mesa to avoid the problems of optical crosstalk and n-GaN layer cleavage.
The second object of the present invention is to provide a method for manufacturing a Micro-LED Micro display, which designs a redistribution layer RDL on a CMOS driving substrate, and connects a Micro-LED chip array with the CMOS driving substrate by means of the redistribution layer RDL, so as to realize a display function of a Micro-LED and reduce the difficulty of passivation and electrode wiring processes after cutting an n-GaN layer in the manufacturing process of the Micro-LED chip.
The first object of the present invention is achieved by:
a Micro-LED Micro-display comprising:
(1) A CMOS driving substrate including an array of pixels which are independently addressable and controllable, and a common electrode distributed outside the pixel region;
(2) A redistribution layer RDL (Re-distributed Layer) formed on the CMOS drive substrate;
(3) Micro-LED chip arrays connected to pixel arrays on the CMOS drive substrate through a redistribution layer RDL;
is characterized in that:
the surface of the CMOS driving substrate is provided with an insulating layer, and a series of through holes are formed in the insulating layer, so that metal electrodes of a pixel array in the CMOS driving substrate are exposed;
the redistribution layer RDL includes an anode, a cathode, and a metal bezel outside the pixel array, wherein: the anodes are metal lattices which are distributed independently, and the metal lattices are electrically connected with the CMOS circuit through holes on the insulating layer respectively; the cathodes are a series of metal strips, the number of rows or columns of the cathodes is the same as that of the anode metal lattice, and all the cathode metal strips are all connected to a metal outer frame outside the pixel area; the metal outer frame has two functions, namely, all cathode metal strips are connected to form common negative connection; secondly, ensuring the alignment precision of the Micro-LED chip array and the pixel array of the CMOS driving substrate;
the Micro-LED chip array is made of GaN-based semiconductor materials, and GaN-based semiconductor layers of each chip are independent of each other and are not connected with each other.
Preferably, the anode material in the redistribution layer RDL is preferably a combination of several of Cr, pt, in, sn, au and the cathode material is also preferably a combination of several of Cr, pt, in, sn, au; in order to ensure that the anode and the cathode are easy to form bonding connection, the outermost layers of the anode and the cathode are 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 heights of the anode, the cathode and the metal outer frame are different by not more than 100nm.
Furthermore, a protective layer is arranged 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, so that the reliability of the device is improved; in order to make the protective layer have good process tolerance, the protective layer is made of organic curing material, preferably polyimide photoresist or SU-8 photoresist.
Further, each chip in the Micro-LED chip array sequentially comprises 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 arranged on the n-GaN layer of each Micro-LED chip, and a p-type ohmic electrode is arranged on the p-GaN layer; the n-type ohmic electrode and the p-type ohmic electrode are distributed on the same side of the Micro-LED chip; preferably, the surface layers of the n-type ohmic electrode and the p-type ohmic electrode of the Micro-LED chip are Au layers with the thickness not less than 500nm, and the surface heights of the n-type ohmic contact and the p-type ohmic electrode are different by not more than 200nm;
furthermore, a layer of metal bonding lamination is also prepared on the n-type ohmic electrode and the p-type ohmic electrode of each Micro-LED chip, and the surface height difference between the n-type ohmic electrode and the p-type ohmic electrode is not more than 200nm; the metal bond stack serves to connect the array of Micro-LED chips to the redistribution layer RDL to form a current path and to secure the Micro-LED chips to the CMOS drive substrate. In order to make this metal bond stack less susceptible to damage during subsequent processing, it is preferred to use a chemically resistant metal such as Cr, pt, in, sn, au; in order to ensure that the metals are easy to form bonding connection, metals with melting points higher than the bonding temperature should be selected, and the outermost layer of the metal bonding lamination is preferably metal Au without an oxide layer and easy to soften, wherein the thickness of the Au layer is not less than 500nm. Meanwhile, in order to ensure the alignment precision of the Micro-LED chip array and the pixel array of the CMOS driving substrate, a metal inner frame is also prepared at the periphery of the Micro-LED chip array, the height of the metal inner frame is not more than 200nm different from the height of the metal bonding lamination, and the width of the metal inner frame is not less than three times the width of the metal bonding lamination.
Further, the p-type ohmic electrode of the Micro-LED chip is in one-to-one correspondence with the anode metal lattice of the redistribution layer RDL to form bonding connection, and the n-type ohmic electrode of the Micro-LED chip is in bonding connection with the cathode metal strip of the redistribution layer RDL.
Further, the Micro-LED chip array comprises red light, green light and blue light Micro-LED chips.
The second object of the present invention is achieved by:
a preparation method of a Micro-LED Micro display comprises the following steps:
(1) Growing a GaN-based red/green/blue LED epitaxial structure on a silicon substrate; the LED epitaxial structure comprises an n-GaN layer, a p-GaN layer and an InGaN/GaN quantum well light-emitting layer clamped between the n-GaN layer and the p-GaN layer;
(2) Manufacturing an LED epitaxial structure with one color into a plurality of Micro-LED chips, wherein the specific steps are as follows: firstly, etching and removing the p-GaN layer and the InGaN/GaN quantum well layer in the partial area of the LED epitaxial structure by using a dry etching process until the n-GaN layer is exposed, so as to form a p-GaN mesa structure; then, the n-GaN layer between the p-GaN mesa structures is etched by a dry etching process to form grooves exposing the silicon substrate, LED epitaxial frames and independent Micro-LED chips; the width between the grooves is not smaller than the width of the p-GaN mesa structure of the Micro-LED chip;
(3) Preparing p-type ohmic electrodes on each p-GaN mesa structure, and preparing n-type ohmic electrodes on n-GaN layers beside each p-GaN mesa structure;
(4) Preparing a metal bonding lamination layer on the n-type ohmic electrode, the p-type ohmic electrode and the LED epitaxial frame;
(5) Etching the groove of the silicon substrate in the step (2) until the depth is larger than the thickness of the GaN-based LED epitaxial structure;
(6) Passivating the Micro-LED chip array, wherein the material of the passivation layer is nitride or oxide containing Si and Al; or the material of the passivation layer is a curable photoresist such as polyimide photoresist, SU-8 photoresist;
(7) Etching a CMOS driving substrate with an insulating layer covered on the surface to form a through hole array;
(8) Preparing a redistribution layer RDL on the perforated CMOS driving substrate, wherein the redistribution layer RDL comprises an anode, a cathode and a metal outer frame outside the pixel array, the anode is a plurality of metal lattices which are independently distributed, and the metal lattices are electrically connected with the CMOS driving substrate through holes on the insulating layer respectively; the cathodes are a series of metal strips, the number of rows or columns of the cathodes is the same as the number of rows or columns of the anode lattice, and all the cathode metal strips are all connected to a metal outer frame outside the pixel array;
(9) Spin-coating a layer of curable photoresist on the surface of the CMOS driving substrate with the RDL of the redistribution layer, removing the photoresist on the surface of the RDL of the redistribution layer and the surface of a bonding pad area on the CMOS driving substrate by a photoetching technology, and curing the photoresist to protect the CMOS driving substrate from being damaged in a subsequent process; the curable photoresist is polyimide photoresist, SU-8 photoresist;
(10) Performing alignment bonding on the Micro-LED chip array with one color obtained in the steps (1) - (6) and the CMOS driving substrate with the redistribution layer RDL obtained in the steps (7) - (9), so that the p-type ohmic electrode of each Micro-LED chip in the Micro-LED chip array is connected with the anode metal point of the redistribution layer RDL, and the n-type ohmic electrode of each Micro-LED chip is connected with the cathode metal strip of the redistribution layer RDL;
(11) Removing a silicon substrate used for epitaxial growth of the Micro-LED chip; obtaining a single-color Micro-LED Micro display;
(12) Repeating the steps (10) and (11) by using the Micro-LED chip array with the second color obtained in the steps (1) - (6), and ensuring that the bonding point position is staggered from the first bonding point position;
(13) Repeating the steps (10) and (11) by using the Micro-LED chip array with the third color obtained in the steps (1) - (6), and ensuring that bonding points are staggered from the first bonding points and the second bonding points; a full color Micro-LED Micro display is obtained.
Further, the connection between the Micro-LED chip array and the CMOS driving substrate provided with the redistribution layer RDL is realized by hot-press bonding through a method of alignment bonding, wherein an n-type ohmic electrode of the Micro-LED chip is connected with a cathode of the redistribution layer RDL, a p-type ohmic electrode is connected with an anode of the redistribution layer RDL, and a bonding interface is Au/Au; meanwhile, a metal inner frame at the periphery of the Micro-LED chip array is connected with a metal outer frame in the RDL of the redistribution layer, so that the alignment precision of the Micro-LED chip array and the pixel array of the CMOS driving substrate is ensured.
According to the invention, the redistribution layer RDL is designed on the CMOS driving substrate, so that the Micro-LED chip array is integrated on the CMOS driving substrate, and a Micro display is formed; the Micro display structure can reduce the difficulty of passivation and electrode wiring process after the n-GaN layer is cut in the manufacturing process of the Micro-LED chip, and the silicon substrate of the Micro-LED chip is easier to remove compared with the sapphire substrate, and a complex and difficult mass transfer technology is not required, so that the full-color display mode is simpler and more reliable.
Drawings
FIG. 1 is a schematic diagram of a preparation flow of a single-color Micro-LED chip array according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of preparing a redistribution layer RDL on a CMOS driving substrate according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a three-dimensional flow for preparing the RDL of the redistribution layer according to an embodiment of the present invention;
FIG. 4 is a schematic flow chart of integrating a single-color Micro-LED chip array on a CMOS driving substrate according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a process flow for preparing a red light Micro-LED chip array according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a preparation flow of a green light Micro-LED chip array according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a preparation flow of a blue light Micro-LED chip array according to an embodiment of the present invention;
fig. 8 is a schematic flow chart of preparing a redistribution layer RDL on a CMOS driving substrate according to an embodiment of the present invention;
FIG. 9 is a schematic flow chart of integrating red/green/blue light Micro-LED chip arrays on a CMOS driving substrate respectively according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of a full-color Micro-LED Micro-display with chips of different sizes according to an embodiment of the present invention;
FIG. 11 is a schematic diagram of a full-color Micro-LED Micro-display with chips of different sizes according to an embodiment of the present invention.
Detailed Description
The present invention is further described in detail below with reference to the accompanying drawings in order to facilitate understanding and practicing the present invention by those of ordinary skill in the art.
Example 1:
the preparation method of the single-color Micro-LED Micro-display comprises the following three contents:
a, as shown in FIG. 1, a preparation method of a single-color Micro-LED chip array comprises the following steps:
in step S1, an LED epitaxial structure 110 is grown on the surface of a silicon substrate 101. 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 using standard semiconductor processing. The method comprises removing the excessive parts of the LED epitaxial structure 110 by etching or other material removing techniques to expose 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 forms a plurality of independent structures with a size of about 10 μm and arranged at intervals on the silicon substrate 101; then an n-type ohmic electrode 150 is prepared on the n-GaN layer 111, and a p-type ohmic electrode 160 is prepared on the p-GaN layer 113 and the LED epitaxial frame 114; thus, a complete Micro-LED chip 115 can be formed, and each independent structure finally forms a Micro-LED chip 115;
step S3, preparing a metal bonding stack 170 on the n-type ohmic electrode 150 and the p-type ohmic electrode 160 of the Micro-LED chip 115 by a metal deposition technique;
in step S4, the Micro-LED chip 115 is subjected to passivation treatment by a thin film preparation technology, and the passivation layer is 180.
B, as shown in fig. 2 and 3, a method for preparing a CMOS drive substrate with a redistribution layer RDL, comprising the steps of:
step S1, performing an insulating layer 201 opening treatment on the CMOS driving substrate 200 by using a standard semiconductor process to expose the metal lattice 202 of the pixel region 210 and the metal outer frame 203 of the non-pixel region 220 of the CMOS driving substrate 200;
in step S2, a redistribution layer RDL is prepared on the perforated CMOS drive substrate 200. The following steps are specifically performed, in which the anode metal lattice 231, the cathode metal strips 232 having the same number of rows or columns as the anode metal lattice 231, and the metal frame 233 are fabricated on the CMOS driving substrate 200 by metal deposition technology. Wherein the anode metal lattice 231 is electrically connected with the metal lattice 202 of the CMOS driving substrate 200, and all the cathode metal strips 232 are all connected to the metal frame 233 outside the pixel region;
in step S3, passivation protection is performed on the CMOS driving substrate 200 with the redistribution layer RDL, and a protective layer 240 is formed on the CMOS driving substrate 200 except for the redistribution layer RDL region and the I/O pad 204 region, so that the CMOS driving substrate 200 with the redistribution layer RDL is obtained.
C. As shown in fig. 4, a method for integrating a single-color Micro-LED chip array into a CMOS drive substrate with a redistribution layer RDL prepared, includes the steps of:
in step S1, micro-LED chips 115 are integrated onto a CMOS drive substrate 200 prepared with a redistribution layer RDL using an alignment bonder. Wherein the n-type ohmic electrode 150 of the Micro-LED chip 115 is connected to the cathode metal stripe 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;
and S2, removing the silicon substrate 101 of the Micro-LED chip 115 to obtain the single-color Micro-LED Micro display.
Example 2:
a preparation method of a full-color Micro-LED Micro-display comprises the following steps:
A. as shown in fig. 5, 6 and 7, a method for preparing a red/green/blue Micro-LED chip array includes, but is not limited to, the following steps:
in step S1, an LED epitaxial structure 110 is grown on the surface of a silicon substrate 101. The LED epitaxial structure 110 includes an n-GaN layer 111, a p-GaN layer 113, and a red/green/blue InGaN/GaN quantum well light emitting layer 122/132/142 sandwiched between the n-GaN layer 111 and the p-GaN layer 113;
in step S2, the LED epitaxial structure 120/130/140 is fabricated into a plurality of red/green/blue light Micro-LED chips 125/135/145 using standard semiconductor processing. In a specific implementation, the redundant parts of the LED epitaxial structures 120/130/140 may be removed by etching or other material removal techniques, so as to expose part of the n-GaN layer 111, the p-GaN layer 113 and one red/green/blue LED epitaxial frame 124/134/144, so that the remaining epitaxial structures 120/130/140 form a plurality of independent structures with a size of about 10 micrometers and arranged at intervals on the silicon substrate 101, i.e. the n-GaN layer 111 is etched; then an n-type ohmic electrode 150 is prepared on the n-GaN layer 111, and a p-type ohmic electrode 160 is prepared on the p-GaN layer 113 and the LED epitaxial frame 124/134/144; thus, a complete red/green/blue Micro-LED chip 125/135/145 can be formed, and each individual structure ultimately forms 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 light Micro-LED chip 125/135/145 by a metal deposition technique;
step S4, removing redundant parts of the silicon substrate 101 of the red/green/blue light Micro-LED chip 125/135/145 by etching or other silicon material removing technologies, and ensuring that the depth of the groove is larger than the thickness of the GaN-based red/green/blue light LED epitaxial structure, thereby obtaining a silicon groove 190;
and S5, carrying out passivation treatment on the red/green/blue light Micro-LED chips 125/135/145 by a film preparation technology, wherein the passivation layer is 180.
B. As shown in fig. 8, a method for preparing a CMOS drive substrate with a redistribution layer RDL includes the steps of:
step S1, performing an insulating layer 201 opening treatment on the CMOS driving substrate 200 by using a standard semiconductor process to expose the metal lattice 202 of the pixel region 210 and the metal outer frame 203 of the non-pixel region 220 of the CMOS driving substrate 200;
in step S2, a redistribution layer RDL is prepared on the perforated CMOS drive substrate 200. The following steps are performed to prepare anode metal lattices 231 and a series of cathode metal strips 232 with the same number of rows or columns as the anode metal lattices 231 on the CMOS driving substrate 200 by metal deposition technology. Wherein the anode metal lattice 231 is electrically connected with the metal lattice 202 of the CMOS driving substrate 200, and all the cathode metal strips 232 are all connected to the metal frame 233 outside the pixel region;
in step S3, passivation protection is performed on the CMOS driving substrate 200 with the redistribution layer RDL, and a protective layer 240 is formed on the CMOS driving substrate 200 except for the redistribution layer RDL region and the I/O pad 204 region. Thus, the CMOS drive substrate 200 prepared with the redistribution layer RDL can be obtained.
C. As shown in fig. 9, a method for integrating a red/green/blue Micro-LED chip array on a CMOS driving substrate with a redistribution layer RDL prepared thereon, includes the steps of:
in step S1, a red light Micro-LED chip 125 is integrated onto a CMOS drive substrate 200 prepared with a redistribution layer RDL using an alignment bonder. Wherein the n-type ohmic electrode 150 of the red light Micro-LED chip 125 is connected with the cathode metal stripe 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected with the anode metal lattice 231 of the redistribution layer RDL;
step S2, removing the silicon substrate 101 of the red light Micro-LED chip 125;
in step S3, green light Micro-LED chips 135 are integrated onto CMOS drive substrate 200, which is prepared with redistribution layer RDL, using an alignment bonder. Wherein the n-type ohmic electrode 150 of the green light Micro-LED chip 135 is connected with the cathode metal stripe 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected with the anode metal lattice 231 of the redistribution layer RDL;
step S4, removing the silicon substrate 101 of the green light Micro-LED chip 135;
in step S5, blue light Micro-LED chips 145 are integrated onto the CMOS drive substrate 200 prepared with the redistribution layer RDL using an alignment bonder. Wherein the n-type ohmic electrode 150 of the blue light Micro-LED chip 145 is connected with the cathode metal stripe 232 of the redistribution layer RDL, and the p-type ohmic electrode 160 is connected with the anode metal lattice 231 of the redistribution layer RDL;
in step S6, the silicon substrate 101 of the blue light Micro-LED chip 145 is removed.
As shown in fig. 10 and 11, a full-color Micro-LED Micro display is thus obtained.
In the method for manufacturing a single-color or full-color Micro-LED Micro-display according to the present invention, the steps are not required to be completed in the listed order, and the order may be appropriately adjusted according to the conditions of the apparatus and the like used. The present invention is not particularly limited as to the GaN growth and etching conditions, and the bonding temperature and pressure may be appropriately adjusted according to the specific equipment conditions or the experience commonly possessed by those skilled in the art. These modifications also fall within the scope of the invention.
Further, the Micro-LED chip size of about "10 microns" in the embodiments of the present invention is merely an example size, and does not constitute a specific limitation on the Micro-LED chip size. Generally, the size of the Micro-LED chip may reach 1-50 μm, and a person skilled in the art may determine the corresponding semiconductor manufacturing process according to the common size range of the Micro-LED chip, which is not limited in this application.
The above embodiments are merely for illustrating the design concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, the scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications according to the principles and design ideas of the present invention are within the scope of the present invention.

Claims (9)

1. A Micro-LED Micro-display comprising:
(1) A CMOS driving substrate including an array of pixels which are independently addressable and controllable, and a common electrode distributed outside the pixel region;
(2) A redistribution layer RDL formed on the CMOS drive substrate;
(3) Micro-LED chip array connected with pixel array on CMOS drive substrate via RDL;
the method is characterized in that:
the surface of the CMOS driving substrate is provided with an insulating layer, and a series of through holes are formed in the insulating layer;
the redistribution layer RDL comprises an anode, a cathode and a metal outer frame, wherein the anode is a plurality of metal lattices which are independently distributed, and the metal lattices are respectively electrically connected with the CMOS circuit through small holes on the insulating layer; the cathodes are metal strips, the number of rows or columns of the metal strips is the same as that of the anode metal lattice, and all the cathode metal strips are connected to a metal outer frame outside the pixel area;
the Micro-LED chip array is made of GaN-based semiconductor materials, and GaN-based semiconductor layers of each chip are independent of each other and are not connected with each other.
2. The Micro-LED Micro-display of claim 1, wherein: the surface layer of the RDL is an Au layer with the thickness not less than 500nm, and the surface heights of the anode, the cathode and the metal outer frame are different by not more than 100nm.
3. The Micro-LED Micro-display of claim 1 or 2, wherein: 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 layers of the n-type ohmic electrode and the p-type ohmic electrode of the Micro-LED chip are Au layers with the thickness not less than 500nm, and the surface height difference of the n-type ohmic contact and the p-type ohmic electrode is not more than 200nm; 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.
4. The Micro-LED Micro-display of claim 1, wherein: the Micro-LED chip array comprises red light, green light and blue light Micro-LED chips.
5. A preparation method of a Micro-LED Micro display comprises the following steps:
(1) Growing a GaN-based red/green/blue LED epitaxial structure on a silicon substrate; the LED epitaxial structure comprises an n-GaN layer, a p-GaN layer and an InGaN/GaN quantum well light-emitting layer clamped between the n-GaN layer and the p-GaN layer;
(2) Manufacturing an LED epitaxial structure with one color into a plurality of Micro-LED chips, wherein the specific steps are as follows: firstly, etching and removing the p-GaN layer and the InGaN/GaN quantum well layer in the partial area of the LED epitaxial structure by using a dry etching process until the n-GaN layer is exposed, so as to form a p-GaN mesa structure; then, the n-GaN layer between the p-GaN mesa structures is etched by a dry etching process to form grooves exposing the silicon substrate, LED epitaxial frames and independent Micro-LED chips; the width between the grooves is not smaller than the width of the p-GaN mesa structure of the Micro-LED chip;
(3) Preparing p-type ohmic electrodes on each p-GaN mesa structure, and preparing n-type ohmic electrodes on n-GaN layers beside each p-GaN mesa structure;
(4) Preparing a metal bonding lamination layer on the n-type ohmic electrode, the p-type ohmic electrode and the LED epitaxial frame;
(5) Passivating the Micro-LED chip array to obtain a passivation layer;
(6) Etching a CMOS driving substrate with an insulating layer covered on the surface to form a through hole array;
(7) Preparing a redistribution layer RDL on the perforated CMOS driving substrate, wherein the redistribution layer RDL comprises an anode, a cathode and a metal outer frame outside the pixel array, the anode is a plurality of metal lattices which are independently distributed, and the metal lattices are electrically connected with the CMOS driving substrate through holes on the insulating layer respectively; the cathodes are a series of metal strips, the number of rows or columns of the cathodes is the same as the number of rows or columns of the anode lattice, and all the cathode metal strips are all connected to a metal outer frame outside the pixel array;
(8) Spin-coating a layer of curable photoresist on the surface of the CMOS driving substrate with the RDL of the redistribution layer, removing the photoresist on the surface of the RDL of the redistribution layer and the surface of a bonding pad area on the CMOS driving substrate by a photoetching technology, and curing the photoresist to protect the CMOS driving substrate from being damaged in a subsequent process;
(9) Performing alignment bonding on the Micro-LED chip array with one color obtained in the steps (1) - (5) and the CMOS driving substrate with the redistribution layer RDL obtained in the steps (6) - (8), so that the p-type ohmic electrode of each Micro-LED chip in the Micro-LED chip array is connected with the anode metal point of the redistribution layer RDL, and the n-type ohmic electrode of each Micro-LED chip is connected with the cathode metal strip of the redistribution layer RDL;
(10) Removing a silicon substrate used for epitaxial growth of the Micro-LED chip; a single color Micro-LED Micro-display was obtained.
6. The method for manufacturing a Micro-LED Micro-display according to claim 5, wherein: the method comprises the following steps of preparing a full-color Micro-LED Micro display:
repeating the steps (1) - (5) for three times to respectively prepare three Micro-LED arrays with different colors;
repeating the steps (9) - (10) for three times, respectively carrying out para-bonding on the three Micro-LED arrays with different colors and the CMOS driving substrate with the redistribution layer RDL obtained in the steps (6) - (8), removing the silicon substrate, and ensuring that the bonding point position of each time is staggered from the bonding point position in the front.
7. The method for manufacturing a Micro-LED Micro-display according to claim 6, wherein: and (3) when preparing the Micro-LED chip arrays with the second color and the third color, etching the groove of the silicon substrate before passivation treatment in the step (5), wherein the etching depth is larger than the thickness of the GaN-based LED epitaxial structure.
8. The method for manufacturing a Micro-LED Micro-display according to claim 5, wherein: in the step (5), the material of the passivation layer is nitride or oxide containing Si and Al; or the material of the passivation layer is a curable photoresist such as polyimide photoresist, SU-8 photoresist.
9. The method for manufacturing a Micro-LED Micro-display according to claim 5, wherein: in step (8), the curable photoresist is a polyimide photoresist, SU-8 photoresist.
CN202310475901.5A 2023-04-28 2023-04-28 Micro-LED Micro display and preparation method thereof Pending CN116404027A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116722094A (en) * 2023-08-07 2023-09-08 季华实验室 Display panel and manufacturing method thereof
CN117219715A (en) * 2023-11-08 2023-12-12 华引芯（武汉）科技有限公司 Preparation method of micro LED matrix light source and micro LED matrix light source

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116722094A (en) * 2023-08-07 2023-09-08 季华实验室 Display panel and manufacturing method thereof
CN117219715A (en) * 2023-11-08 2023-12-12 华引芯（武汉）科技有限公司 Preparation method of micro LED matrix light source and micro LED matrix light source
CN117219715B (en) * 2023-11-08 2024-03-01 华引芯（武汉）科技有限公司 Preparation method of micro LED matrix light source and micro LED matrix light source

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