Color micro-led bonding method based on controllable preparation of metal bump array

Abstract

The present application relates to a kind of based on metal bump array controllable preparation color Micro-LED bonding method, metal bump array is prepared using electroplating method, the surface morphology of metal bump is regulated by changing current density, the height uniformity of metal bump is improved by cathode rotation and electroplating parameter;Two photoetchings are used, and the electrical connection bridge deposition of electroplating seed layer is deposited on the first photoetching mask layer, and the size and shape of metal bump are defined using the second photoetching mask layer, and the metal bump array of uniform size, shape and electrical characteristics is formed;Metal bump array with different heights is prepared on CMOS drive substrate and red light, green light, blue light three kinds of Micro-LED chip respectively using the above preparation method, and red light, green light, blue light three kinds of Micro-LED chip are bonded on CMOS drive substrate by three times bonding respectively, and color Micro-LED display array is formed.The method can realize higher pixel density in unit area, improve the picture quality and production efficiency of Micro-LED display.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more specifically to a bonding method for color Micro-LEDs based on a controllable fabrication method using a metal bump array. Background Technology

[0002] With the development of a new round of technological revolution and the rise of new applications such as 5G ultra-high-definition displays, AR glasses, medical displays, and automotive displays, these applications have placed higher demands on display technology. Micro-LED displays have emerged to meet this need, boasting outstanding characteristics such as high brightness, long lifespan, wide color gamut, and good stability, thus satisfying the personalized needs of high-end displays. Micro-LED display technology refers to a new type of display technology that utilizes Micro-LED chips to achieve full-color display, encompassing technologies such as chip fabrication, driving substrate fabrication, mass transfer and bonding, and full-colorization.

[0003] The bonding technology between Micro-LED chips and driver chips is a key technological link in promoting the practical application and marketization of Micro-LED displays. Two commonly used bonding methods include traditional wire bonding and improved flip-chip bonding. Improved bonding technology is a mature, efficient, and reliable hybrid integration technology, and it is expected to become the mainstream development technology for Micro-LEDs. One of the difficulties in flip-chip bonding technology lies in the fabrication of bumps. Therefore, designing a microstructure of high-density metal bumps on Micro-LED chips and using low-cost electroplating methods to fabricate uniform bumps, thereby solving problems such as stress deformation and reliability in high-density metal bump bonding, is currently a research hotspot in academia.

[0004] Full-color technology is also one of the challenges of Micro-LED display technology. Currently, there are two main technologies for achieving full-color in Micro-LED: one is the RGB three-color LED method, and the other is the ultraviolet (UV) LED / blue LED + light-emitting medium method. The first method is based on the principle of three primary color mixing, so the resulting image colors are relatively stable. The technology is mature and therefore the cost is relatively low, but there are deviations in the full-color display of LED pixels. The second method is mainly based on quantum dot technology, so the resulting image colors have higher saturation and a simpler structure, but there are problems with insufficient color uniformity and mutual interference between colors. Summary of the Invention

[0005] The purpose of this invention is to provide a color Micro-LED bonding method based on a controllable fabrication of a metal bump array. This method can achieve higher pixel density per unit area, thereby improving the image quality and production efficiency of Micro-LED displays.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: a color Micro-LED bonding method based on controllable fabrication of a metal bump array. The method involves preparing the metal bump array using electroplating, controlling the surface morphology of the metal bumps by changing the current density, and improving the uniformity of the metal bump height by cathode rotation and electroplating parameters. Two photolithography steps are used to deposit the electrical connection bridges of the electroplating seed layer onto the first photolithographic mask layer, and the second photolithographic mask layer defines the size and shape of the metal bumps, forming a metal bump array with uniform size, shape, and electrical properties. Using the above fabrication method, metal bump arrays of different heights are fabricated on a CMOS driving substrate and on red, green, and blue Micro-LED chips, respectively. The red, green, and blue Micro-LED chips are then bonded to the CMOS driving substrate through three bonding steps to form a color Micro-LED display array.

[0007] Furthermore, the metal bumps include single-element metal bumps, alloy metal bumps, and multilayer metal bumps.

[0008] Furthermore, the method specifically includes the following steps:

[0009] Step 1: Clean and dry the CMOS driver substrate and the blue Micro-LED epitaxial wafer;

[0010] Step 2: Deposit an ITO layer on the surface of the blue Micro-LED epitaxial wafer, form a mesa structure on the blue Micro-LED epitaxial wafer through photolithography and ICP etching, grow a SiO2 layer on the mesa by plasma-enhanced chemical vapor deposition, and then selectively etch the SiO2 by photolithography and wet etching to form an ITO window.

[0011] Step 3: Deposit the first photolithographic mask layer on the surface of the blue Micro-LED chip and the surface of the CMOS driving substrate respectively using photolithography;

[0012] Step 4: Deposit seed layers on the Micro-LED chip substrate and CMOS driver substrate formed in Step 3, respectively;

[0013] Step 5: Deposit a second photolithographic mask layer above the seed layer using a photolithography process;

[0014] Step 6: A highly uniform copper thin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density.

[0015] Step 7: A highly uniform tin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density to form a copper / tin metal film.

[0016] Step 8: Place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the second photolithographic mask layer; remove the seed layer by wet etching; place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the first photolithographic mask layer, forming a copper / tin metal bump array.

[0017] Step 9: Repeat steps 1-8 to form copper / tin metal bump arrays with different heights on the green and red Micro-LED chip substrates respectively.

[0018] Step 10: Bond the blue, green and red Micro-LED chip substrates with copper / tin metal bump arrays of different heights to the CMOS driving substrate respectively. After bonding, peel off the substrate of the Micro-LED chip substrate.

[0019] Step 11: Fill the gaps between the bumps of the color Micro-LED array obtained in step 10 with acrylic or epoxy resin to form a color Micro-LED display array.

[0020] Furthermore, the seed layer is made of metal Cu with a thickness of 100-300 nm. The seed layer enhances the adhesion between the electrolyte and the metal and promotes the surface uniformity of the bumps.

[0021] Furthermore, the order in which copper / tin metal bump arrays are fabricated on the three types of Micro-LED chips (red, green, and blue) is arbitrary. That is, copper / tin metal bump arrays can be fabricated first on any one of the blue, green, or red Micro-LED chip substrates, and then on the other two.

[0022] Furthermore, the bonding order of the red, green, and blue Micro-LED chip substrates to the CMOS driver substrate is arbitrary, and the height of the copper / tin metal bumps on the later-bonded Micro-LED chip substrate is greater than the height of the copper / tin metal bumps on the earlier-bonded Micro-LED chip substrate.

[0023] Furthermore, the surface morphology of the tin bumps is controlled by adjusting the current density to regulate the generation and growth rate of tin crystal nuclei during electroplating, thereby achieving controllable surface morphology of the tin bumps. The current density used for tin bump preparation is 12-14 mA / cm². 2 The electric field distribution during the electroplating process is adjusted by rotating the cathode to improve the height uniformity of the tin bumps. The cathode rotation rate for preparing the tin bumps is 50-100 rpm.

[0024] Furthermore, the speed of the two processes of tin crystal nucleus formation and growth determines the fineness of the metal crystal; if the formation speed of the crystal nucleus is fast and the growth speed is slow, then the number of crystal nuclei generated is large and the grains are fine, and vice versa, the grains are coarse.

[0025] Compared with existing technologies, this invention has the following advantages: This invention provides a color Micro-LED bonding method based on controllable fabrication of a metal bump array. This method uses electroplating to prepare the metal bump array. By changing the current density, the generation and growth rate of tin crystal nuclei during electroplating are adjusted, thereby achieving controllable surface morphology of the tin bumps. The uniformity of the metal bump height is improved by cathode rotation and electroplating parameters. Two photolithography steps are used, allowing the electrical connection bridges of the electroplated seed layer to be deposited on the first photolithographic mask layer, and the size and shape of the metal bumps to be defined by the second photolithographic mask layer. This makes the removal of the seed layer simple, clean, and convenient, unlike traditional wet etching which may result in incomplete seed layer removal and dry etching which requires expensive equipment. The fabrication process is not only cost-effective but also achieves high uniformity and controllable surface morphology. Furthermore, this method prepares metal bump arrays of different heights on a CMOS driving substrate and three types of Micro-LED chips (red, green, and blue). The red, green, and blue Micro-LED chips are bonded to the CMOS driving substrate through three bonding steps to form a color Micro-LED display array. This method of metal bump fabrication and bonding enables higher pixel density per unit area, improving the image quality and production efficiency of Micro-LED displays. Attached Figure Description

[0026] Figures 1 to 8 This is a schematic diagram of the bump preparation process in an embodiment of the present invention;

[0027] Figure 9 This is a diagram of the electroplating experimental apparatus in an embodiment of the present invention;

[0028] Figure 10 This is a top view of the RGB three-color array on the Micro-LED chip in an embodiment of the present invention;

[0029] Figure 11 This is a schematic diagram of the first bonding in an embodiment of the present invention;

[0030] Figure 12 This is a schematic diagram of the second bonding in an embodiment of the present invention;

[0031] Figure 13 This is a schematic diagram of the third bonding step in an embodiment of the present invention;

[0032] Figure 14 This is an SEM image of the tin bump at low current density in an embodiment of the present invention;

[0033] Figure 15 This is an SEM image of the tin bump under high current density in an embodiment of the present invention;

[0034] In the figure: 101-GaN; 102-U-GaN; 103-N-GaN; 104-P-GaN with ITO; 105-Insulating layer; 106-Photoresist; 107-Seed layer; 108-Copper bump; 109-Tin bump; 110-Acrylic or epoxy resin. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0036] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0037] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0038] This embodiment provides a color Micro-LED bonding method based on controllable fabrication of a metal bump array. The metal bump array is fabricated using electroplating. The surface morphology of the metal bumps is controlled by changing the current density, and the uniformity of the metal bump height is improved by cathode rotation and electroplating parameters. Two photolithography steps are used: the electrical connection bridges of the electroplating seed layer are deposited on the first photolithographic mask layer, and the size and shape of the metal bumps are defined by the second photolithographic mask layer, forming a metal bump array with uniform size, shape, and electrical properties. Using the above fabrication method, metal bump arrays of different heights are fabricated on a CMOS driving substrate and on red, green, and blue Micro-LED chips, respectively. The red, green, and blue Micro-LED chips are then bonded to the CMOS driving substrate through three bonding steps to form a color Micro-LED display array.

[0039] The metal bumps can be single-metal bumps, alloy metal bumps, or multi-layer metal bumps.

[0040] In this embodiment, the above-described color Micro-LED bonding method based on a controllable fabrication of a metal bump array specifically includes the following steps:

[0041] Step 1: Clean and dry the CMOS driver substrate and the blue Micro-LED epitaxial wafer.

[0042] Step 2: Deposit an ITO layer on the surface of the blue Micro-LED epitaxial wafer, form a mesa structure on the blue Micro-LED epitaxial wafer through photolithography and ICP etching, grow a SiO2 layer on the mesa using plasma-enhanced chemical vapor deposition (PECVD), and then selectively etch the SiO2 using photolithography and wet etching methods to form an ITO window.

[0043] Step 3: The first photolithographic mask layer is deposited on the surface of the blue Micro-LED chip and the surface of the CMOS driving substrate respectively by photolithography.

[0044] Step 4: Deposit seed layers on the Micro-LED chip substrate and CMOS driver substrate formed in Step 3, respectively;

[0045] Step 5: Set a second photolithographic mask layer above the seed layer using photolithography.

[0046] Step 6: A highly uniform copper thin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density.

[0047] Step 7: A highly uniform tin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density to form a copper / tin metal film.

[0048] Step 8: Place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the second photolithographic mask layer; remove the seed layer by wet etching; place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the first photolithographic mask layer, forming a copper / tin metal bump array.

[0049] Step 9: Repeat steps 1-8 to form copper / tin metal bump arrays with different heights on the green and red Micro-LED chip substrates respectively.

[0050] Step 10: Bond the blue, green and red Micro-LED chip substrates with copper / tin metal bump arrays of different heights to the CMOS driver substrate respectively. After bonding, peel off the substrate of the Micro-LED chip substrate.

[0051] Step 11: Fill the gaps between the bumps of the color Micro-LED array obtained in step 10 with acrylic or epoxy resin to form a color Micro-LED display array.

[0052] The electroplating experimental apparatus used in this embodiment is as follows: Figure 9 As shown. The bump fabrication process is as follows. Figure 1-8 As shown. The triple bonding process is as follows. Figure 11-13 As shown. In this embodiment, the top view of the RGB three-color array on the Micro-LED chip is as follows. Figure 10 As shown.

[0053] In step 2, SiO2 is used as an insulating layer with a thickness of 100nm. The insulating layer can play a protective and insulating role.

[0054] In step 4, the seed layer is made of metallic Cu with a thickness of 100-300 nm. This seed layer enhances the adhesion between the electrolyte and the metal and promotes the surface uniformity of the bumps.

[0055] In the above method, the order in which copper / tin metal bump arrays are fabricated on the red, green, and blue Micro-LED chips is arbitrary. That is, copper / tin metal bump arrays can be fabricated first on any one of the blue, green, or red Micro-LED chip substrates, and then on the other two. The bonding order between the red, green, and blue Micro-LED chip substrates and the CMOS driver substrate is also arbitrary, with the height of the copper / tin metal bumps on the later-bonded Micro-LED chip substrate being greater than the height of the copper / tin metal bumps on the earlier-bonded Micro-LED chip substrate.

[0056] In steps 6 and 7, the spacing of the Micro-LED bump array is 8µm and the diameter is 4.5µm, with the copper film having a height of 3µm and the tin film having a height of 2µm.

[0057] The surface morphology of the tin bumps is controlled by adjusting the current density to regulate the generation and growth rate of tin crystal nuclei during electroplating. High uniformity is achieved by rotating the cathode to adjust the electric field distribution during electroplating and by using appropriate electroplating parameters. The current density used for tin bump fabrication is 12-14 mA / cm². 2 The electric field distribution during the electroplating process is adjusted by rotating the cathode, thereby improving the uniformity of the tin bump height. The cathode rotation rate for preparing the tin bump is 50-100 rpm. The speed of the two processes of tin nucleus formation and growth determines the fineness of the metal crystal; if the nucleus formation rate is fast and the growth rate is slow, the number of nuclei generated is large and the grains are fine, and vice versa.

[0058] In step 7, a high-density, highly uniform Micro-LED tin bump array with controllable surface morphology is prepared using electroplating, specifically including the following methods:

[0059] 1. At low current densities, the formation rate of crystal nuclei is slow, while the growth rate is fast, resulting in fewer crystal nuclei and coarser grains.

[0060] Under conditions of a current density of 7 mA / cm², an anode-cathode distance of 3 cm, a plating solution stirring rate of 210 rpm, a cathode rotation rate of 60 rpm, and an electroplating time of 25 min, the following results were obtained: Figure 14 The tin bump array shown has a height of 3.067 μm at the top, 3.259 μm in the middle, and 3.309 μm at the bottom, with a uniformity of approximately 3.76%.

[0061] Second, under high current density, the crystal nucleus is generated quickly, and the growth rate is full, resulting in a large number of crystal nuclei and finer grains.

[0062] Under conditions of a current density of 12 mA / cm², an anode-cathode distance of 3 cm, a plating solution stirring rate of 210 rpm, a cathode rotation rate of 60 rpm, and a plating time of 4 min, the following results were obtained: Figure 15 The tin bump array shown has a height of 3.283 μm at the top, 3.041 μm in the middle, and 3.230 μm at the bottom, with a uniformity of approximately 3.8%.

[0063] In step 8, the wet etching process uses a copper ammonia solution with the following proportions: 5g CuCl2, 5g NH4Cl, 84ml NH3H2O, and 2.5L deionized water.

[0064] In step 10, the bonding process is divided into three stages: first, pre-bonding, with a pressure of 15 MPa and heating to 200°C for 10 min in a formic acid environment; second, final bonding, with the temperature continuing to rise to 260°C and held for 5 min; third, annealing, with annealing at 200°C for 20 min; and finally, slow cooling to room temperature to reduce stress.

[0065] A specific embodiment is provided below. This embodiment specifically includes the following steps:

[0066] Step 1: Clean and dry the CMOS driver substrate and the blue Micro-LED epitaxial wafer.

[0067] Step 2: Deposit an ITO layer on the surface of the blue Micro-LED epitaxial wafer, form a mesa structure on the blue Micro-LED epitaxial wafer through photolithography and ICP etching, grow a 100nm SiO2 layer on the mesa using plasma-enhanced chemical vapor deposition (PECVD), and then selectively etch the SiO2 using photolithography and wet etching methods to form an ITO window.

[0068] Step 3: The first photolithographic mask layer is deposited on the surface of the blue Micro-LED chip and the surface of the CMOS driving substrate respectively by photolithography.

[0069] Step 4: Deposit 100nm copper seed layers on the Micro-LED chip substrate and CMOS driver substrate formed in Step 3, respectively.

[0070] Step 5: Set a second photolithographic mask layer above the seed layer using photolithography.

[0071] Step 6: A highly uniform copper thin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density.

[0072] Step 7: A highly uniform tin thin film is prepared on the Micro-LED chip substrate and CMOS driver substrate using electroplating, and by rotating the cathode and adjusting the current density, forming a copper / tin metal thin film. The surface morphology of the tin bumps is controlled by adjusting the current density to regulate the generation and growth rate of tin crystal nuclei during electroplating, thus achieving controllable surface morphology of the tin bumps. High uniformity is achieved by rotating the cathode to adjust the electric field distribution during electroplating and by using appropriate electroplating parameters. Specifically, the following methods are included:

[0073] Method 1: At low current density, the formation rate of crystal nuclei is slow, while the growth rate is fast, resulting in fewer crystal nuclei and coarser grains.

[0074] Under conditions of a current density of 7 mA / cm², an anode-cathode distance of 3 cm, a plating solution stirring rate of 210 rpm, a cathode rotation rate of 60 rpm, and an electroplating time of 25 min, the following results were obtained: Figure 14 The tin bump array shown has a height of 3.067 μm at the top, 3.259 μm in the middle, and 3.309 μm at the bottom, with a uniformity of approximately 3.76%.

[0075] Method 2: Under high current density, the crystal nucleus is generated quickly and the growth rate is full, resulting in a large number of crystal nuclei and finer grains.

[0076] Under conditions of a current density of 12 mA / cm², an anode-cathode distance of 3 cm, a plating solution stirring rate of 210 rpm, a cathode rotation rate of 60 rpm, and a plating time of 4 min, the following results were obtained: Figure 15 The tin bump array shown has a height of 3.283 μm at the top, 3.041 μm in the middle, and 3.230 μm at the bottom, with a uniformity of approximately 3.8%.

[0077] Step 8: Place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the second photomask layer; remove the seed layer by wet etching using a copper ammonia solution with a ratio of 5g CuCl2, 5g NH4Cl, 84ml NH3·H2O and 2.5L deionized water; place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the first photomask layer, forming a copper / tin metal bump array.

[0078] Step 9: Repeat steps 1-8 to form copper / tin metal bump arrays with different heights on the green and red Micro-LED chip substrates, respectively.

[0079] Step 10: Blue, green, and red Micro-LED chip substrates with copper / tin metal bump arrays of different heights were bonded to the CMOS driver substrate. The bonding process consisted of three stages: first, pre-bonding, with a pressure of 15 MPa and heating to 200°C for 10 minutes in a formic acid environment; second, final bonding, with the temperature further increased to 260°C and held for 5 minutes; third, annealing, with annealing at 200°C for 20 minutes; and finally, slow cooling to room temperature to reduce stress. After bonding, the substrate of the Micro-LED chip substrate was peeled off.

[0080] Step 11: Fill the gaps between the bumps of the color Micro-LED array obtained in step 10 with acrylic or epoxy resin to form a color Micro-LED display array.

[0081] This embodiment employs an improved electroplating method to prepare tin bumps, which not only reduces costs but also achieves high uniformity and controllable surface morphology. This embodiment also utilizes a low-cost, simple, and efficient method for removing the seed layer: a two-step photolithography process. In this embodiment, metal bump arrays of different heights are prepared on a CMOS driving substrate and on red, green, and blue Micro-LED chips, respectively. The red, green, and blue Micro-LED chips are then bonded to the CMOS driving substrate using a three-step bonding process to form a color Micro-LED display array. This metal bump preparation and bonding method enables higher pixel density per unit area, improving the image quality and production efficiency of Micro-LED displays.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for bonding color Micro-LEDs based on a controllable fabrication method using a metal bump array, characterized in that, Metal bump arrays are fabricated using electroplating. The surface morphology of the metal bumps is controlled by changing the current density, and the uniformity of the metal bump height is improved by cathode rotation and electroplating parameters. Two photolithography steps are used to deposit the electrical connection bridges of the electroplating seed layer onto the first photolithographic mask layer, and the size and shape of the metal bumps are defined by the second photolithographic mask layer, forming a metal bump array with uniform size, shape, and electrical properties. Using the above fabrication method, metal bump arrays with different heights are fabricated on a CMOS driving substrate and on red, green, and blue Micro-LED chips, respectively. The red, green, and blue Micro-LED chips are then bonded to the CMOS driving substrate through three bonding steps to form a color Micro-LED display array. The method for bonding color Micro-LEDs based on a controllable fabrication method using a metal bump array includes the following steps: Step 1: Clean and dry the CMOS driver substrate and the blue Micro-LED epitaxial wafer; Step 2: Deposit an ITO layer on the surface of the blue Micro-LED epitaxial wafer, form a mesa structure on the blue Micro-LED epitaxial wafer through photolithography and ICP etching, grow a SiO2 layer on the mesa by plasma-enhanced chemical vapor deposition, and then selectively etch the SiO2 by photolithography and wet etching to form an ITO window. Step 3: Deposit the first photolithographic mask layer on the surface of the blue Micro-LED chip and the surface of the CMOS driving substrate respectively using photolithography; Step 4: Deposit seed layers on the Micro-LED chip substrate and CMOS driver substrate formed in Step 3, respectively; Step 5: Deposit a second photolithographic mask layer above the seed layer using a photolithography process; Step 6: A highly uniform copper thin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density. Step 7: A highly uniform tin film is prepared on the Micro-LED chip substrate and CMOS driver substrate by electroplating and by rotating the cathode and adjusting the current density to form a copper / tin metal film. Step 8: Place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the second photolithographic mask layer; remove the seed layer by wet etching; place the Micro-LED chip substrate and CMOS driver substrate in the resist remover to remove the first photolithographic mask layer, forming a copper / tin metal bump array. Step 9: Repeat steps 1-8 to form copper / tin metal bump arrays with different heights on the green and red Micro-LED chip substrates respectively. Step 10: Bond the blue, green and red Micro-LED chip substrates with copper / tin metal bump arrays of different heights to the CMOS driving substrate respectively. After bonding, peel off the substrate of the Micro-LED chip substrate. Step 11: Fill the gaps between the bumps of the color Micro-LED array obtained in step 10 with acrylic or epoxy resin to form a color Micro-LED display array.

2. The color Micro-LED bonding method based on a controllable fabrication of a metal bump array according to claim 1, characterized in that, The metal bumps include single-element metal bumps, alloy metal bumps, and multi-layer metal bumps.

3. The color Micro-LED bonding method based on a controllable fabrication of a metal bump array according to claim 1, characterized in that, The seed layer is made of metallic Cu with a thickness of 100-300 nm. The seed layer enhances the adhesion between the electrolyte and the metal and promotes the surface uniformity of the bumps.

4. The color Micro-LED bonding method based on a controllable fabrication of a metal bump array according to claim 1, characterized in that, The order in which copper / tin metal bump arrays are fabricated on red, green, and blue Micro-LED chips is arbitrary. That is, copper / tin metal bump arrays can be fabricated first on any one of the blue, green, or red Micro-LED chip substrates, and then copper / tin metal bump arrays can be fabricated on the other two.

5. The color Micro-LED bonding method based on a controllable fabrication of a metal bump array according to claim 1, characterized in that, The bonding order of red, green, and blue Micro-LED chip substrates to the CMOS driver substrate is arbitrary. The height of the copper / tin metal bumps on the Micro-LED chip substrate bonded later is greater than the height of the copper / tin metal bumps on the Micro-LED chip substrate bonded earlier.

6. The color Micro-LED bonding method based on a controllable fabrication of a metal bump array according to claim 1, characterized in that, The surface morphology of tin bumps is controlled by adjusting the current density to regulate the generation and growth rate of tin crystal nuclei during electroplating, thereby achieving controllable surface morphology of the tin bumps. The current density used for tin bump preparation is 12-14 mA / cm². 2 The electric field distribution during the electroplating process is adjusted by rotating the cathode to improve the height uniformity of the tin bumps. The cathode rotation rate for preparing the tin bumps is 50-100 rpm.

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