A micro-led bump array preparation and bonding method based on self-assembly of metal microspheres

Abstract

The application discloses a Micro-LED bump array preparation and bonding method based on metal microsphere self-assembly, comprising a Micro-LED chip substrate or a driving back plate, a bump lower metallization layer, an Au thin film, an inter-bump insulation layer and metal microspheres which are sequentially arranged from bottom to top.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor packaging technology, and in particular to a method for preparing and bonding a Micro-LED bump array based on metal microsphere self-assembly. Background Art

[0002] In recent decades, with the rapid development of display technology, display products have been widely used in televisions, monitors, laptops, tablets, mobile phones, and other applications, bringing great convenience to people's lives and work. Existing display technologies are mainly LCD (liquid crystal display) and OLED (organic light emitting diode) displays. With the continuous development of display technology, Micro-LED display technology, with its advantages such as ultra-high resolution, low power consumption, high brightness, high color saturation, fast response time, thin thickness, and long life, has become a focus of attention and research for major manufacturers and research institutions, and is expected to become the next generation of display technology.

[0003] Micro-LED chips are typically integrated with driver backplanes to enable display applications in various scenarios. As resolution and pixel density increase, bump preparation and bonding have become key technical challenges for Micro-LED displays. Flip-chip technology, among other things, lowers packaging costs and enables chip stacking and three-dimensional packaging, representing a growing trend in chip interconnect technology. Flip-chip bonding involves aligning and attaching the chip's solder joints to the pads on the substrate. A solder reflow process is then used to form solder balls between the chip and substrate pads. The gaps between the chip and substrate are then filled with adhesive to achieve an electrical and mechanical connection. Therefore, the key to flip-chip bonding lies in bump formation. Traditional bump fabrication methods include evaporation deposition, printing, electroplating, adhesive transfer, SB2-Jet, and metal droplet jetting. Each bump fabrication method has its drawbacks, and the technology is still relatively immature. For example, the commonly used traditional photolithography reflow method forms metal pillars through etching or lift-off methods, and then forms metal bumps through heating and reflow. This not only wastes a lot of metal materials, but also easily forms a metal oxide layer at high temperature during the solder reflow process in the bump production, which will affect the performance of the bumps, Micro-LED chips, and CMOS or TFT on the driver backplane. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing and bonding a Micro-LED bump array based on self-assembly of metal microspheres, which has a simple preparation process, saves raw materials, effectively improves the quality of the bumps, and enhances the bonding strength.

[0005] To achieve the above object, the application adopts the following technical scheme: a Micro-LED bump array preparation and bonding method based on metal microsphere self-assembly, the Micro-LED bump array comprising, from bottom to top, a substrate, a bump lower metallization layer, an Au thin film, an inter-bump insulation layer, and metal microspheres; the inter-bump insulation layer covers part of the area between pixels in the substrate, forming an exposed Au thin film array corresponding to the pixels of the substrate one by one; the metal microspheres are combined with the Au thin film array one by one through a self-assembly method, forming a metal microsphere array corresponding to the pixels of the substrate one by one; the metal microsphere array and the Au thin film array of the substrate are precisely aligned and bonded one by one, forming a Micro-LED display array.

[0006] In a preferred embodiment, the self-assembly combination method comprises electrostatic adsorption, Au-S covalent bond, or immune reaction.

[0007] In a preferred embodiment, the metal microspheres comprise gold microspheres, silver microspheres, indium microspheres, tin microspheres, and alloy microspheres thereof.

[0008] In a preferred embodiment, the substrate is specifically a Micro-LED chip substrate or a driving backplane.

[0009] In a preferred embodiment, the method comprises the following steps:

[0010] Step 1: cleaning and blow-drying the Micro-LED chip substrate and the driving backplane;

[0011] Step 2: setting a first photoresist mask layer on the surface of the Micro-LED chip substrate and the driving backplane through a photoetching process;

[0012] Step 3: depositing a UBM layer and an Au layer on the Micro-LED chip substrate and the driving backplane;

[0013] Step 4: peeling off the first photoresist mask layer, forming a UBM metal layer and an Au layer;

[0014] Step 5: depositing an insulation layer on the surface of the Au layer through a thin film deposition process, and then etching an opening above the patterned Au layer to expose the Au layer through a photoetching and ICP process;

[0015] Step 6: preparing a metal microsphere array through a self-assembly technology;

[0016] Step 7: bonding the metal microspheres on the Micro-LED chip substrate and the driving backplane;

[0017] Step 8: filling the gap of the bonded bump array structure with acrylic or epoxy resin.

[0018] In a preferred embodiment, the UBM metal layer mainly plays the role of adhesion and diffusion barrier, and is sequentially arranged on the Micro-LED chip substrate and the driving backboard from bottom to top; the adhesion layer comprises metal Ti, Cr, Cu, W or an alloy thereof, and has a thickness of 50-300 nm; and the barrier layer is metal Pd, Pt or an alloy thereof, and has a thickness of 50-300 nm.

[0019] In a preferred embodiment, the Au layer is arranged above the UBM layer and plays the role of infiltration.

[0020] In a preferred embodiment, the bonding condition in step 7 is that the temperature is room temperature to 300 DEG C, the pressure is 1-10 MPa, and the time is 10-90 min.

[0021] Compared with the prior art, the present application has the following beneficial effects: the preparation process is simple, raw materials are saved, the quality of the bump is effectively improved, and the bonding strength is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a bump preparation process schematic diagram (one) of the preferred embodiment of the present application;

[0023] Figure 2 is a bump preparation process schematic diagram (two) of the preferred embodiment of the present application;

[0024] Figure 3 is a bump preparation process schematic diagram (three) of the preferred embodiment of the present application;

[0025] Figure 4 is a bump preparation process schematic diagram (four) of the preferred embodiment of the present application;

[0026] Figure 5 is a bump preparation process schematic diagram (five) of the preferred embodiment of the present application;

[0027] Figure 6 is a bump preparation process schematic diagram (six) of the preferred embodiment of the present application;

[0028] Figure 7 is a metal microsphere array top view of the Micro-LED chip or the driving backboard of the preferred embodiment of the present application;

[0029] Figure 8 is a metal microsphere array and driving backboard metal microsphere array one-to-one accurate alignment pre-bonding process schematic diagram of the preferred embodiment of the present application;

[0030] Figure 9Au thin film array of Micro-LED chip or driving backboard and metal microsphere array of driving backboard or Micro-LED chip one-to-one accurate alignment pre-bonding process schematic diagram of preferred embodiment of the present application;

[0031] Figure 10 bonding process schematic diagram of preferred embodiment of the present application;

[0032] Figure 11 filling process schematic diagram of preferred embodiment of the present application;

[0033] Reference signs: 101-Micro-LED chip substrate or driving backboard; 102-photoresist; 103-UBM layer; 104-Au layer; 105-insulating layer; 106-metal microsphere; 107-acrylic or epoxy resin. DETAILED DESCRIPTION

[0034] The application will be further described below in conjunction with the drawings and embodiments.

[0035] It should be noted that the following detailed description is illustrative only and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains.

[0036] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form, and in addition, it should be understood that when the terms “comprise” and / or “include” are used in the specification, it means that there is a feature, step, operation, device, component and / or combination thereof.

[0037] Reference Figures 1 to 11A method for preparing and bonding a Micro-LED bump array based on self-assembly of metal microspheres 106 comprises a Micro-LED chip substrate or driver backplane 101, an under-bump metallization layer (UBM layer 103), an Au film, an inter-bump insulating layer 105, and metal microspheres 106, which are sequentially arranged from bottom to top; the inter-bump insulating layer 105 covers a portion of the area between pixels in the Micro-LED chip substrate or driver backplane 101, and a photoresist 102 is provided on the inter-bump insulating layer 105 to form a bond with the Micro-LED chip pixels or the driver backplane 106. 1 pixel in a one-to-one correspondence with the exposed Au thin film array; the metal microspheres 106 are combined one-to-one with the Au thin film array through a self-assembly method to form a metal microsphere 106 array corresponding one-to-one to the pixels of the Micro-LED chip or the pixels of the driving backplane 101; the metal microsphere 106 array of the Micro-LED chip and the metal microsphere 106 array or the Au thin film array of the driving backplane are precisely aligned and bonded one by one, or the Au thin film array of the Micro-LED chip and the metal microsphere 106 array of the driving backplane are precisely aligned and bonded one by one to form a Micro-LED display array.

[0038] The self-assembly bonding methods include electrostatic adsorption, Au-S covalent bond, and immune reaction.

[0039] The metal microspheres 106 include gold microspheres, silver microspheres, indium microspheres, tin microspheres, and alloy microspheres thereof.

[0040] Example 1:

[0041] A method for preparing and bonding a Micro-LED bump array based on self-assembly of metal microspheres 106 includes the following steps:

[0042] Step 1: Clean and dry the Micro-LED chip substrate and driver backplane;

[0043] Step 2: Using a photolithography process, a first photolithography mask layer is formed on the surface of the Micro-LED chip substrate and the driver backplane;

[0044] Step 3: Depositing the UBM layer 103 and the Au layer 104 on the Micro-LED chip substrate and the driver backplane;

[0045] Step 4: stripping the first photolithography mask layer to form a UBM metal layer and an Au layer 104;

[0046] Step 5: Deposit an insulating layer 105 on the surface of the Au layer 104 by a thin film deposition process, and then etch an opening above the patterned Au layer 104 by photolithography and ICP process to expose the Au layer 104:

[0047] Step 6: the array of metal microspheres 106 is prepared by self-assembly technology;

[0048] Step 7: the metal microspheres 106 on the Micro-LED chip substrate and the driving backboard are bonded;

[0049] Step 8: the gap of the bump array structure after bonding is filled with acrylic or epoxidized resin 107;

[0050] The UBM metal layer of step 3 mainly plays the role of adhesion and diffusion barrier, which is usually composed of multiple metal films such as adhesion layer, diffusion barrier layer and wetting layer, and is arranged on the Micro-LED chip substrate and the driving backboard from bottom to top; the adhesion layer includes metals Ti, Cr, Cu, W or their alloys, and the thickness is 50-300 nm; the barrier layer is metal Pd, Pt or their alloys, and the thickness is 50-300 nm.

[0051] The Au layer 104 of step 3 is arranged above the UBM layer 103 and plays the role of wetting, and the thickness is 100-300 nm.

[0052] The insulating layer 105 of step 5 is SiO2, and the thickness is 100 nm. The insulating layer 105 can play the role of protection and isolation.

[0053] The self-assembly bonding method includes electrostatic adsorption, Au-S covalent bond and immune reaction.

[0054] The metal microspheres 106 include gold microspheres, silver microspheres, indium microspheres, tin microspheres and alloy microspheres, and the size of the microspheres is 3-5 um. Gold microspheres are selected in this embodiment.

[0055] The self-assembly technology is used to prepare the array of metal microspheres 106 in step 6, which specifically includes the following methods:

[0056] Method one: since the gold particles are firmly combined with the amino group through non-covalent electrostatic adsorption, the self-assembly method of electrostatic adsorption is used to combine the Au layer 104 with the metal microspheres 106; that is, the metal microspheres 106 are modified with amino groups, so that the metal microspheres 106 only fall on the Au layer 104 and are electrostatically adsorbed with the Au layer 104;

[0057] Method two: since a very strong Au-S covalent bond is formed between the thiol group, the self-assembly method of Au-S covalent bond is used to combine the Au layer 104 with the metal microspheres 106; that is, the metal microspheres 106 are modified with thiol groups, so that the metal microspheres 106 only fall on the Au layer 104 and are covalently bonded with Au;

[0058] Method three: since the N-terminal of the protein and the carboxyl molecules on the surface of the gold nanoparticles are modified by carbodiimide hydrochloride / N-hydroxysuccinimide (EDC / NHS) to form an amide bond, the Au layer 104 surface molecules can specifically bind to the protein, so by using the nanolabeling technology, the antibody on the metal microsphere 106 is accessed, and then the metal microsphere 106 only falls on the Au layer 104, and the metal microsphere 106 and the Au layer 104 will undergo strong chemical adsorption;

[0059] The bonding conditions in step 7 are: temperature from room temperature to 300℃, pressure from 1-10MPa, time from 10-90min; as shown in Figure 8 、 Figure 9 The metal microsphere 106 array of the Micro-LED chip is precisely bonded with the metal microsphere 106 array or the Au thin film array of the driving backboard one by one, or the Au thin film array of the Micro-LED chip is precisely bonded with the metal microsphere 106 array of the driving backboard one by one, to form a Micro-LED display array.

[0060] Embodiment 2:

[0061] This example includes the following specific steps:

[0062] Step 1: clean and dry the Micro-LED chip substrate and the driving backboard;

[0063] Step 2: set a first photoresist mask layer on the surface of the Micro-LED chip substrate and the driving backboard by a photoetching process;

[0064] Step 3: deposit 200nm Ti and 200nm Pt as the UBM layer 103 and 100nm Au layer 104 on the Micro-LED chip substrate and the driving backboard;

[0065] Step 4: peel off the first photoresist mask layer to form the UBM metal layer and the Au layer 104;

[0066] Step 5: deposit a 100nm thick SiO2 layer as the insulating layer 105 on the surface of the Au layer 104 by a thin film deposition process, and then etch an opening above the patterned Au layer 104 by a photoetching and ICP process to expose the Au layer 104;

[0067] Step 6: prepare a 3um size metal microsphere 106 array by a self-assembly technology; which includes the following methods:

[0068] Method one: since the gold particles are firmly combined with the amino groups through non-covalent electrostatic adsorption, the Au layer 104 is combined with the metal microspheres 106 by using the self-assembly method combined with electrostatic adsorption; that is, the amino groups are modified on the metal microspheres 106, so that the metal microspheres 106 only fall on the Au layer 104 and electrostatic adsorption occurs between the Au layer 104 and the metal microspheres 106;

[0069] Method two: since a very strong Au-S covalent bond is formed between the Au and the thiol groups, the Au layer 104 is combined with the metal microspheres 106 by using the self-assembly method combined with the Au-S covalent bond; that is, the thiol groups are modified on the metal microspheres 106, so that the metal microspheres 106 only fall on the Au layer 104 and covalent bonding occurs between the Au and the metal microspheres 106;

[0070] Method three: since the N-terminal of the protein and the carboxyl groups modified on the surface of the gold nanoparticles are coupled through carbodiimide hydrochloride / N-hydroxysuccinimide (EDC / NHS) to form an amide bond, that is, the molecules on the surface of the Au layer 104 can specifically combine with the protein, through the nano-labeling technology, the antibodies are labeled on the metal microspheres 106, so that the metal microspheres 106 only fall on the Au layer 104, and strong chemical adsorption occurs between the metal microspheres 106 and the Au layer 104; the metal microspheres 106 are combined with the Au thin film array through the self-assembly method, forming the metal microsphere 106 array corresponding to the Micro-LED chip pixel or the driving backboard 101 pixel.

[0071] Step 7: the metal microspheres 106 on the Micro-LED chip substrate and the driving backboard are bonded, and the bonding conditions are set as a temperature of 200℃, a pressure of 5MPa, and a time of 50min.

[0072] Step 8: the gap of the bump array structure after bonding is filled with acrylic or epoxy resin 107;

[0073] In this example, the gold microsphere array is prepared by using the self-assembly method, which has simple preparation process, saves raw materials, effectively improves the quality of the bumps, and improves the bonding strength.

[0074] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the patent application of the present application shall be within the scope of the present application.

Claims

1. A method for preparing and bonding a Micro-LED bump array based on self-assembly of metal microspheres, characterized in that, The Micro-LED bump array comprises, from bottom to top, a substrate, a bump lower metallization layer, an Au thin film, an inter-bump insulation layer, and metal microspheres; the inter-bump insulation layer covers a partial area between pixels in the substrate, forming an exposed Au thin film array corresponding to the pixels of the substrate one by one; the metal microspheres are combined with the Au thin film array one by one through a self-assembly method, forming a metal microsphere array corresponding to the pixels of the substrate one by one; the metal microsphere array and the Au thin film array of the substrate are precisely aligned and bonded one by one, forming a Micro-LED display array. The method comprises the following steps: Step 1: cleaning and drying the Micro-LED chip substrate and the driving backboard; Step 2: setting a first photoresist mask layer on the surface of the Micro-LED chip substrate and the driving backboard through a photoetch process; Step 3: depositing a UBM layer and an Au layer on the Micro-LED chip substrate and the driving backboard; Step 4: peeling off the first photoresist mask layer to form a UBM metal layer and an Au layer; Step 5: depositing an insulation layer on the surface of the Au layer through a thin film deposition process, and then etching an opening above the patterned Au layer through a photoetch and ICP process to expose the Au layer; Step 6: preparing a metal microsphere array through a self-assembly technique; Step 7: bonding the metal microspheres on the Micro-LED chip substrate and the driving backboard; Step 8: filling the gap of the bonded bump array structure with acrylic or epoxy resin.

2. The method according to claim 1, wherein the method further comprises the steps of: providing a metal microsphere array on a substrate; and providing a Micro-LED array on a substrate; and bonding the metal microsphere array and the Micro-LED array. The self-assembly bonding method comprises electrostatic adsorption, Au-S covalent bond, or immune reaction. 3.The method of claim 1, wherein the metal microspheres are self-assembled into a Micro-LED bump array. The metal microspheres comprise gold microspheres, silver microspheres, indium microspheres, tin microspheres, and alloy microspheres thereof.

4. The method of claim 1, wherein the method further comprises: The substrate is specifically a Micro-LED chip substrate or a driving backboard.

5. The method of claim 1, wherein the method further comprises: The UBM metal layer comprises an adhesion layer and a barrier layer, which are sequentially arranged on the Micro-LED chip substrate and the driving backboard from bottom to top; the adhesion layer comprises metal Ti, Cr, Cu, W, or alloy thereof, and has a thickness of 50-300 nm; the barrier layer is metal Pd, Pt, or alloy thereof, and has a thickness of 50-300 nm.

6. The method of claim 1, wherein the method further comprises: The Au layer is arranged above the UBM layer and plays a role of wetting.

7. The method of claim 1, wherein the method further comprises: The bonding conditions in step 7 are as follows: temperature, room temperature to 300 DEG C; pressure, 1-10 MPa; and time, 10-90 min.

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