Preparation method of high-resolution Micro LED display substrate and display substrate

Abstract

The invention provides a preparation method of a high-resolution Micro LED display substrate and a display substrate, and belongs to the technical field of display, and the preparation method comprises the steps: forming a barrier layer on a CMOS drive substrate; forming a bonding metal layer on the barrier layer; redundant metal on the bonding metal layer is removed; bonding the whole circle Micro LED chip with the bonding metal layer; the substrate of the whole circle Micro LED chip is peeled off; a single Micro LED pixel is prepared; an insulating layer is formed between the single Micro LED pixels; and preparing a common cathode electrode to be interconnected with the bonding metal layer. The display substrate comprises a CMOS driving substrate, a barrier layer, a bonding metal layer, a full-circle Micro LED chip, an insulating layer and a common cathode electrode layer. According to the invention, high-resolution display can be realized, meanwhile, the precision requirement during bonding alignment can be reduced, and the bonding strength and the bonding stability are not influenced.

Description

[0001] This application is a divisional application of the patent application entitled "A high-resolution Micro LED display substrate and its preparation method". The application date of the original application is September 1, 2022, and the application number is 202211072015.X. Technical Field

[0002] The present application belongs to the field of display technology, and in particular, relates to a method for preparing a high-resolution Micro LED display substrate and a display substrate. Background Art

[0003] In the display field, high resolution has always been the research direction of researchers. With the continuous development of display technology, Micro LED has emerged in the field of display technology. Due to its high brightness, high contrast, long life, high stability in extreme environments and low power consumption and energy saving advantages, it is considered to be the future technology for displays. The existing Micro LED display substrate structure and preparation method have extremely high requirements for bonding and alignment accuracy. It is difficult to ensure high bonding alignment accuracy while meeting the requirements of bonding strength and bonding stability. Summary of the invention

[0004] The purpose of this application is to provide a method for preparing a high-resolution Micro LED display substrate and a display substrate to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above objectives, on the one hand, the present application provides a method for preparing a high-resolution Micro LED display substrate, comprising the following steps:

[0006] S1, forming a barrier layer on a CMOS driving substrate;

[0007] S2, forming a bonding metal layer covering the barrier layer on the barrier layer;

[0008] S3, attaching a blue film to the surface of the source film, peeling off the blue film to remove the metal on the photoresist, and removing the negative photoresist;

[0009] S4, bonding the entire circular Micro LED chip to the bonding metal layer through a bonding process;

[0010] S5, decomposing the GaN layer at the GaN / sapphire interface by laser, and peeling off the sapphire substrate of the full-circle Micro LED chip;

[0011] S6. Prepare a single Micro LED pixel through photolithography and etching processes;

[0012] S7, depositing a SiO2 film by plasma enhanced chemical vapor deposition, exposing the N-GaN and the SiO2 film on the bonding metal layer by photoresist, photolithography, and development, removing the SiO2 film by dry etching, and finally removing the photoresist, so as to deposit an insulating layer between single Micro LED pixels, expose the GaN layer and the bonding metal layer, and the rest is covered by a passivation layer;

[0013] S8. Prepare a common cathode electrode pattern by applying negative resist, photolithography and development, and then prepare a common cathode electrode layer by E-beam evaporation of metal. Then, stick a blue film on the surface of the source film, peel off the blue film to remove the metal on the photoresist, remove the negative photoresist, and interconnect the prepared common cathode electrode layer with the bonding metal layer.

[0014] Optionally, before step S1, it is also necessary to spin-coat a negative photoresist on the CMOS driving substrate, and expose the pixel region anode and the outer ring cathode on the CMOS driving substrate through a photolithography process.

[0015] Optionally, in step S1, the barrier layer is formed by a sputtering process; the material of the barrier layer is titanium, nickel or an alloy of the two, and may be one layer or more layers with a thickness of 1 nm to 1 μm.

[0016] Optionally, in step S2, the material of the bonding metal layer is tin, indium or an alloy of the two, and the thickness is 1 μm to 3 μm; and the bonding metal layer is formed by an E-beam process.

[0017] Optionally, in step S4, the bonding process is wafer bonding, the bonding temperature of the bonding process is 100° C. to 300° C., the bonding pressure is 98N to 147N, and the bonding time is 5 min to 20 min.

[0018] Optionally, in step S6, a pixel pattern is first prepared by photoresist coating, photolithography and development, and then GaN between pixels is removed by dry etching, and finally the resist is removed to prepare a single Micro LED pixel.

[0019] Optionally, in step S7, the insulating layer material is SiO2; and the thickness of the insulating layer is 1 μm to 10 μm.

[0020] On the other hand, the present application provides a high-resolution Micro LED display substrate, which is prepared by the above-mentioned preparation method. The high-resolution Micro LED display substrate includes: a CMOS driving substrate, a barrier layer, a bonding metal layer, a full-circle Micro LED chip, an insulating layer and a common cathode electrode layer; the full-circle Micro LED chip includes a chip P electrode, a current spreading layer and a GaN layer.

[0021] The technical effects of this application are:

[0022] The present application provides a method for preparing a high-resolution Micro LED display substrate and a display substrate, which can achieve high-resolution display while reducing the precision requirements during bonding and alignment without affecting the bonding strength and bonding stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic cross-sectional structure diagram of a high-resolution Micro LED display substrate in an embodiment of the present application;

[0025] Figure 2 is a schematic diagram of the cross-sectional structure of the barrier layer in an embodiment of the present application;

[0026] Figure 3 is a schematic diagram of the cross-sectional structure of the bonding metal layer in an embodiment of the present application;

[0027] Figure 4 Schematic diagram of the cross-sectional structure of the bonding between the full-circle Micro LED chip and the CMOS driver substrate in the embodiment of the present application;

[0028] Figure 5 This is a schematic diagram of the cross-sectional structure of the whole-circle Micro LED chip substrate peeling in the embodiment of the present application;

[0029] Figure 6 A schematic diagram of a cross-sectional structure of a Micro LED single pixel prepared in an embodiment of the present application;

[0030] Figure 7 Schematic diagram of the cross-sectional structure of the insulation layer in the embodiment of the present application.

[0031] Figure numerals: 100 - CMOS driving substrate; 200 - barrier layer; 300 - bonding metal layer; 400 - full-circle Micro LED chip; 401 - chip P electrode; 402 - current spreading layer; 403 - GaN layer; 404 - chip substrate; 500 - insulating layer; 600 - common cathode electrode layer. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] like Figures 2 to 7 As shown, the method for preparing a high-resolution Micro LED display substrate provided in the present application includes the following steps:

[0035] Step 101: spin-coat a negative photoresist on the CMOS driving substrate 100, and expose the pixel region anode and the outer ring cathode on the CMOS driving substrate 100 through a photolithography process.

[0036] Step 102: forming a barrier layer 200 on the CMOS driver substrate 100, which increases the adhesion between the bonding metal and the metal on the driver substrate surface, prevents the diffusion of the bonding layer metal and the metal on the driver substrate surface, reduces the defects and thickness of the interface alloy compound, reduces the generation of voids, and improves the bonding reliability.

[0037] In an exemplary embodiment, the material of the barrier layer 200 may be titanium, nickel, or an alloy of the two, and may be one layer or multiple layers with a total thickness ranging from 1 nm to 1 μm; wherein the barrier layer may be formed by sputtering to make the film more dense, which is beneficial to reduce diffusion, such as Figure 2 shown.

[0038] Step 103 : forming a bonding metal layer 300 on the barrier layer 200 .

[0039] In an exemplary embodiment, the material of the bonding metal layer 300 is one of tin and indium or an alloy of the two, which can be one layer or more layers with a total thickness of 1 μm to 3 μm; wherein the bonding metal layer 300 is completed by an E-beam method, and a metal film with good film quality and thick thickness can be prepared, such as Figure 3 shown.

[0040] Step 104: attach a blue film to the surface of the source film, peel off the blue film to remove the metal on the photoresist, and remove the negative photoresist.

[0041] Step 105: Bond the full-circle Micro LED chip 400 to the bonding metal layer (300) through a bonding process.

[0042] In an exemplary embodiment, the entire circular Micro LED chip 400 is aligned with the bonding metal layer (300) of the CMOS driving substrate (100) by an alignment bonding device, and then bonding is achieved under temperature and pressure conditions, such as Figure 4 As shown, the bonding temperature is 100℃~300℃, the bonding pressure is 98N~147N, and the bonding time is 5min~20min. Compared with die to die bonding, wafer bonding requires lower alignment accuracy, which can improve production yield.

[0043] Step 106: Remove the sapphire substrate of the entire circular Micro LED chip (400) by laser decomposing the GaN layer 403 at the GaN / sapphire interface. Figure 5 shown.

[0044] Step 107: Prepare a single Micro LED pixel through photolithography and etching processes.

[0045] In an exemplary embodiment, a pixel pattern is prepared by coating, photolithography, and development, and then GaN between pixels is removed by dry etching, and finally the coating is removed to prepare a single Micro LED pixel. Figure 6 shown.

[0046] Step 108: Deposit SiO2 thin film by PECVD. The prepared thin film is dense and has good insulation performance. Then, the SiO2 thin film on the N-GaN and the cathode bonding metal layer of the outer ring of the driving substrate is exposed by coating, photolithography, and development. Then, the SiO2 thin film is removed by dry etching. Finally, the coating is removed to deposit an insulating layer 500 between single Micro LED pixels, exposing the GaN layer and the cathode bonding metal layer of the outer ring of the driving substrate. The rest is covered by the passivation layer to avoid contact with the chip and cause leakage. The thickness can be 1μm to 10μm, such as Figure 7 shown.

[0047] Step 109: prepare a common cathode electrode pattern by applying negative resist, photolithography, and development. Use negative resist to facilitate subsequent metal stripping. Then, prepare a common cathode electrode layer 600 by E-beam evaporation of metal. Use the E-beam process to prepare a metal film with good film quality and thick thickness. Then, attach a blue film to the surface of the source, peel off the blue film to remove the metal on the photoresist, remove the negative photoresist, and interconnect the prepared common cathode electrode layer 600 with the bonding metal layer 300 of the outer cathode of the CMOS drive substrate, as shown in FIG. Figure 1 shown.

[0048] like Figure 1As shown, the high-resolution Micro LED display substrate provided by the present application includes: a CMOS driving substrate 100, a barrier layer 200, a bonding metal layer 300, a full-circle Micro LED chip 400, an insulating layer 500 and a common cathode electrode layer 600. Among them, the full-circle Micro LED chip 400 includes a chip P electrode 401, a current spreading layer 402 and a GaN layer 403.

[0049] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for preparing a high-resolution Micro LED display substrate, characterized in that: The method for preparing the high-resolution MicroLED display substrate comprises the following steps: S1, forming a barrier layer (200) on a CMOS driving substrate (100); S2, forming a bonding metal layer (300) covering the barrier layer (200) on the barrier layer (200); S3, attaching a blue film to the surface of the source film, peeling off the blue film to remove the metal on the photoresist, and removing the negative photoresist; S4, bonding the full-circle Micro LED chip (400) to the bonding metal layer (300) through a bonding process; S5, decomposing the GaN layer (403) at the GaN / sapphire interface by laser, and peeling off the sapphire substrate of the full-circle Micro LED chip (400); S6. Prepare a single Micro LED pixel through photolithography and etching processes; S7, depositing a SiO2 film by plasma enhanced chemical vapor deposition, then exposing the N-GaN and the SiO2 film on the bonding metal layer (300) by photoresist, photolithography, and development, then removing the SiO2 film by dry etching, and finally removing the photoresist, thereby depositing an insulating layer (500) between single Micro LED pixels, exposing the GaN layer and the bonding metal layer (300), and the rest is covered by a passivation layer; S8, preparing a common cathode electrode pattern by negative photoresist, photolithography, and development, and then preparing a common cathode electrode layer (600) by E-beam evaporation of metal, and then attaching a blue film to the surface of the source, peeling off the blue film to remove the metal on the photoresist, removing the negative photoresist, and interconnecting the prepared common cathode electrode layer (600) with the bonding metal layer (300).

2. The method for preparing a high-resolution Micro LED display substrate according to claim 1, characterized in that: Before step S1, a negative photoresist is spin-coated on the CMOS driving substrate (100), and a pixel region anode and an outer ring cathode on the CMOS driving substrate (100) are exposed through a photolithography process.

3. The method for preparing a high-resolution Micro LED display substrate according to claim 1, characterized in that: In step S1, the barrier layer is formed by a sputtering process; the material of the barrier layer is titanium, nickel or an alloy of the two, and the thickness is 1 nm to 1 μm.

4. The method for preparing a high-resolution Micro LED display substrate according to claim 1, characterized in that: In step S2, the material of the bonding metal layer (300) is tin, indium or an alloy of the two, and the thickness is 1 μm to 3 μm; the bonding metal layer (300) is formed by an E-beam process.

5. The method for preparing a high-resolution Micro LED display substrate according to claim 1, characterized in that: In step S4, the bonding process is wafer bonding, the bonding temperature of the bonding process is 100° C. to 300° C., the bonding pressure is 98N to 147N, and the bonding time is 5 min to 20 min.

6. The method for preparing a high-resolution Micro LED display substrate according to claim 1, characterized in that: In step S6, a pixel pattern is first prepared by photoresist, photolithography and development, and then the GaN between pixels is removed by dry etching, and finally the resist is removed to prepare a single Micro LED pixel.

7. The method for preparing a high-resolution Micro LED display substrate according to claim 1, characterized in that: In step S7, the material of the insulating layer (500) is SiO2; the thickness of the insulating layer (500) is 1 μm to 10 μm.

8. A high-resolution Micro LED display substrate, prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The high-resolution Micro LED display substrate comprises: a CMOS driving substrate (100), a barrier layer (200), a bonding metal layer (300), a full-circle Micro LED chip (400), an insulating layer (500) and a common cathode electrode layer (600); the full-circle Micro LED chip (400) comprises a chip P electrode (401), a current spreading layer (402) and a GaN layer (403).

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