Fabrication method of a multi-color Micro-LED display device

Abstract

The present invention discloses a manufacturing method for a multi-color Micro-LED display device, belonging to the technical field of basic electrical components. The method of the present invention manufactures a Micro-LED display device by repeatedly performing wafer-level bonding on unpatterned LED epitaxial wafers of different colors. Since the LED epitaxial wafers are not patterned into a Micro-LED array before bonding, the requirements for alignment in the process are significantly relaxed. In a Micro-LED display device, a Micro-LED array needs to be integrated with a driving chip including a base substrate. In this process, LED arrays of multiple colors are manufactured as follows: The unpatterned LED epitaxial wafers are bonded to the surface of the driving chip, and then the substrates of the LEDs are removed and a planarization operation is performed to allow the next layer of unpatterned LED epitaxial wafers to be bonded. After stacking three layers of LED epitaxial layers in this way, the three different-color LED epitaxial layers are patterned into a Micro-LED array by etching, and then a metal layer is fabricated to complete the electrode connection. This method can improve the manufacturing efficiency of Micro-LED display devices.

Description

Technical Field

[0001] The present invention relates to display technology, and particularly to a manufacturing method of a multi-color Micro-LED display device, belonging to the technical field of basic electrical components. Background Art

[0002] Due to the characteristics of high brightness, high luminous efficiency, high contrast, fast response speed, long service life, high color gamut, self-luminescence, and seamless splicing, the performance of the new Micro-LED display device is much higher than that of the existing LCD and OLED display devices. Therefore, the new Micro-LED display device has broad application prospects in the fields of micro-projection, transparent display, and head-up display, etc.

[0003] In the prior art, the Micro-LED display device generally adopts a top-emission mode. The LED chip and the driving circuit chip are developed separately, and then one-to-one electrical interconnection is carried out between pixel units. However, the integration of millions or even tens of millions of micro-LEDs and the driving circuit chip array is very challenging. Taking a standard 4K ultra-high-definition display screen as an example, there are a total of 3840×2160 = 8294400 pixels. For RGB Micro-LEDs, a total of 8294400×3 = 24883200 Micro-LED grains are required, and the number of grains reaches the tens of millions level. Therefore, how to efficiently and accurately transfer a huge number of Micro-LED grains from the donor substrate to the driving substrate is a major process difficulty in the manufacture of the new Micro-LED display device at present.

[0004] To overcome the above process difficulties in the manufacture of the new Micro-LED display device, the prior art has proposed a manufacturing method for batch transferring Micro-LED grains and a manufacturing method for bonding an LED array with an original substrate to a driving chip by using an inverted soldering technique.

[0005] In the manufacturing method for batch transferring Micro-LED grains, the driving circuit chip is manufactured on one substrate, and the LED chip is manufactured on another substrate. First, the LED is transferred to an intermediate substrate and the original substrate is removed, and then the LED on the intermediate substrate is picked out and placed on the substrate with the driving circuit chip in multiple times. However, this manufacturing method is inefficient and expensive. In addition, the equipment for batch transferring micro-LEDs on a large scale is not yet very mature at present.

[0006] In the manufacturing method of bonding an LED array with an original substrate to a driving chip using an inverted soldering technique, first, solder metal bumps are fabricated on the surface of the LED array with the original substrate and the surface of the driving chip respectively. Then, an inverted soldering device is used to align the LED array with the fabricated solder metal bumps to the driving circuit chip, and the parameters of soldering pressure, temperature, and time are adjusted to achieve the electrical interconnection between the LED array and the driving circuit. The yield of the LED display panel manufactured by this method depends on the alignment accuracy between the LED array and the driving chip, and the pressure generated at the bonding interface due to the thermal mismatch between the two different substrates causes reliability problems. In addition, it is difficult to perform inverted soldering of LED arrays of multiple different colors on the driving chip, which is not conducive to the fabrication of color display devices.

[0007] In addition, both of the above two manufacturing methods for new Micro-LED display devices electrically interconnect the prepared LED chips and driving chips. Therefore, the miniaturization of a single LED pixel is limited, restricting the improvement of the resolution of the LED display panel.

[0008] In summary, the present invention aims to propose an efficient manufacturing method for multi-color Micro-LED display devices. Summary of the Invention

[0009] The object of the present invention is to address the deficiencies in the above background technology by providing a manufacturing method for multi-color Micro-LED display devices. By means of processes such as wafer bonding and substrate removal, the object of efficiently manufacturing multi-color Micro-LED display devices is achieved, and the technical problems of the existing manufacturing methods for Micro-LED display devices, such as the immaturity of the technology for batch transferring micro-LEDs, high cost, and low manufacturing efficiency, are solved.

[0010] The present invention adopts the following technical solutions to achieve the above object:

[0011] A manufacturing method for multi-color Micro-LED display devices, including steps 1 to 20.

[0012] Step 1, first bonding metal fabrication: Clean the surfaces of the green LED epitaxial wafer to be fabricated with bonding metal and the driving chip, and deposit a bonding metal layer on the front sides of the green LED epitaxial wafer and the driving chip by means of vacuum coating.

[0013] Step 2, first wafer-level bonding: Place the green LED epitaxial wafer with the bonding metal fabricated on the front side and the driving chip on both sides of a high-pressure bonder, and adjust parameters such as bonding pressure, bonding time, and bonding temperature to achieve high-quality bonding of the two wafers.

[0014] Step 3, removal of the substrate of the green LED epitaxial wafer: The substrate of the green LED epitaxial wafer on the bonded wafer is removed by means of grinding, etching, laser lift-off and other processes.

[0015] Step 4, removal of the buffer layer of the green LED: The buffer layer between the substrate of the green LED epitaxial wafer and the green LED epitaxial layer is removed by means of ICP etching, and the surface is polished flat by CMP.

[0016] Step 5, fabrication of the second bonding metal: The surface of the red LED epitaxial wafer to which the bonding metal is to be fabricated and the bonded wafer from which the buffer layer of the green LED is removed in Step 4 are cleaned, and a bonding metal layer is deposited on the front sides of the two wafers by means of vacuum coating.

[0017] Step 6, second wafer-level bonding: The red LED epitaxial wafer with the second bonding metal fabricated in Step 5 and the bonded wafer are placed on both sides of a high-pressure bonder, and parameters such as the bonding pressure, bonding time, and bonding temperature are adjusted to achieve high-quality bonding of the two wafers.

[0018] Step 7, removal of the substrate of the red LED epitaxial wafer: The substrate of the red LED epitaxial wafer on the bonded wafer is removed by means of grinding, etching, laser lift-off and other processes.

[0019] Step 8, removal of the buffer layer of the red LED: The buffer layer between the substrate of the red LED epitaxial wafer and the red LED epitaxial layer is removed by means of ICP etching, and the surface is polished flat by CMP.

[0020] Step 9, fabrication of the third bonding metal: The surface of the blue LED epitaxial wafer to which the third bonding metal is to be fabricated and the bonded wafer from which the buffer layer of the red LED is removed in Step 8 are cleaned, and a bonding metal layer is deposited on the front sides of the two wafers by means of vacuum coating.

[0021] Step 10, third wafer-level bonding: The blue LED epitaxial wafer with the third bonding metal fabricated in Step 9 and the bonded wafer are placed on both sides of a high-pressure bonder, and parameters such as the bonding pressure, bonding time, and bonding temperature are adjusted to achieve high-quality bonding of the two wafers.

[0022] Step 11, removal of the substrate of the blue LED epitaxial wafer: The substrate of the blue LED epitaxial wafer on the bonded wafer is removed by means of grinding, etching, laser lift-off and other processes.

[0023] Step 12, removal of the buffer layer of the blue LED: The buffer layer between the substrate of the blue LED epitaxial wafer and the blue LED epitaxial layer is removed by means of ICP etching, and the surface is polished flat by CMP.

[0024] Step 13, Blue LED patterning: According to the pixel size designed on the driving chip, etch the blue LED epitaxial layer on the surface of the bonding chip in Step 12 to form a blue LED patterned array.

[0025] Step 14, Third bonding metal patterning: According to the size of the blue LED patterned array, etch the third bonding metal layer between the blue LED and the red LED to form a partition, so that the individual third-layer bonding metal structures under each blue LED in the blue LED patterned array obtained in Step 13 are independent of each other.

[0026] Step 15, Red LED patterning: According to the pixel size designed on the driving chip, etch the red LED epitaxial layer on the surface of the bonding chip in Step 14 to form a red LED patterned array.

[0027] Step 16, Second bonding metal patterning: According to the size of the red LED patterned array, etch the second bonding metal layer between the red LED and the green LED to form a partition, so that the individual second-layer bonding metal structures under each red LED in the red LED patterned array obtained in Step 15 are independent of each other.

[0028] Step 17, Green LED patterning: According to the pixel size designed on the driving chip, etch the green LED epitaxial layer on the surface of the bonding chip in Step 16 to form a green LED patterned array.

[0029] Step 18, First bonding metal patterning: According to the size of the green LED patterned array, etch the first bonding metal layer between the green LED and the driving chip to form a partition, so that the individual first-layer bonding metal structures under each green LED in the green LED patterned array obtained in Step 17 are independent of each other.

[0030] Step 19, Anode interconnection electrode fabrication: Fabricate metal electrodes to connect the individual third-layer bonding metal structure and the individual first-layer bonding metal structure under the blue LED, so that the anode on the driving chip is electrically connected to the positive electrode metal of the blue LED; fabricate metal electrodes to connect the individual second-layer bonding metal structure and the first-layer bonding metal structure under the red LED, so that the anode on the driving chip is electrically connected to the positive electrode metal of the red LED; the individual first-layer bonding metal structure under the green LED is directly connected to the anode on the driving chip, and there is no need to fabricate an interconnection metal electrode.

[0031] Step 20, manufacturing of the common cathode electrode: First, an insulating layer is fabricated on the bonding pad surface where the interconnection electrodes are manufactured in step 19). Then, through photolithography and etching, a portion of the insulating layer on the surfaces of the red LED, green LED, and blue LED arrays is removed to expose the corresponding LED layers. Finally, a common cathode metal electrode is deposited on the bonding pad surface, such that the cathodes of the red LED, green LED, and blue LED arrays are all connected to the common cathode electrode on the driving chip. Thus, the multi-color Micro-LED device is manufactured.

[0032] Based on the above technical solutions, the present invention can be further improved as follows.

[0033] Further, the sizes of the LED epitaxial wafer and the driving chip are the same, being 2 inches, 4 inches, 6 inches, or 8 inches.

[0034] Preferably, the substrate material of the LED epitaxial wafer is silicon-based or sapphire-based.

[0035] Preferably, the LED epitaxial wafer has a vertical structure, with the anode disposed above the light-emitting layer and the cathode disposed below the light-emitting layer.

[0036] Preferably, the substrate of the driving chip can be silicon-based or glass-based.

[0037] Preferably, in the middle of each pixel unit on the surface of the driving chip, there is a metal anode lead electrode connected to the bonding metal, and cathode lead electrodes are distributed around the pixel area.

[0038] Further, in steps 1, 5, and 9, the bonding surface of the bonding metal is made of Au and Sn, the adhesion layer of the bonding metal is made of Ti and Ni, and the barrier layer of the bonding metal is made of Pt.

[0039] Preferably, in steps 2, 6, and 10, before wafer bonding, the two surfaces to be bonded are activated to remove impurities such as metals and organic substances on the surfaces, so as to improve the bonding quality.

[0040] Further, in steps 3, 7, and 11, during the process of substrate removal, care should be taken to avoid damaging the flatness of the LED epitaxial wafer below the substrate.

[0041] Preferably, in steps 4, 8, and 12, after the buffer layer is etched away, the LED is further etched and thinned to enhance the light efficiency of the LED.

[0042] Further, in steps 4 and 8, after the buffer layer is removed and the LED is thinned, a CMP polishing and flattening treatment must be performed to reduce the roughness of the bonding pad surface after the thinning process and ensure the smoothness and flatness of the subsequent bonding interface.

[0043] Further, in steps 13, 15, and 17, during the process of performing graphic ICP etching on the LED, the etching rate is controlled by selecting the working pressure, etching power, and the ratio of reaction gases, so as to prevent the situation of incomplete etching where no array is formed or over-etching occurs too much.

[0044] Further, in steps 14, 16, and 18, during the process of performing graphic IBE etching on the bonding metal, the etching rate is controlled by selecting the working pressure, etching power, etc., so as to prevent the situation of incomplete etching where no array is formed or over-etching occurs too much; in addition, during the etching process, the etching angle is adjusted to prevent the metal particles etched out from accumulating on both sides of the channel, which affects the subsequent production of interconnection electrodes.

[0045] Preferably, in step 19, the anodic interconnection electrode can be prepared by the method of negative photoresist stripping metal. The adhesion layer of the anodic interconnection electrode is made of Ti and Ni, and the conductive layer of the anodic interconnection electrode is made of the adhesion layer Pt and Au.

[0046] Further, in step 20, the insulating layer can be silicon oxide or silicon nitride, and the common cathode electrode uses an ITO transparent electrode, which does not block the light output of the LED.

[0047] The present invention adopts the above technical solutions and has the following beneficial effects:

[0048] (1) By using unpatterned different-color LED epitaxial wafers for multiple bondings, the present invention overcomes the defects of the existing manufacturing technology of Micro-LED display devices. Since the epitaxial wafers are not patterned into miniature Micro-LED arrays, the requirements for alignment are significantly relaxed, which has the advantage of convenient mass production and improves the production efficiency.

[0049] (2) The method for manufacturing a multi-color Micro-LED display device of the present invention, after multiple bondings of unpatterned different-color LED epitaxial wafers, realizes the patterning of different-color LED epitaxial wafers based on semiconductor processes such as photolithography and etching. Therefore, compared with massive transfer schemes such as Pick&Place, it is easier to miniaturize a single LED pixel to the sub-micron level, which is more conducive to the manufacture of high-resolution Micro-LED devices.

[0050] (3) The method for manufacturing a multi-color Micro-LED display device of the present invention first inversely bonds unpatterned different-color LED epitaxial wafers, and then positively etches different-color LED epitaxial wafers to form different-color LED arrays, avoiding the use of expensive equipment for batch large-scale transfer of miniature LEDs and overcoming the defect that the flip-chip bonding technology cannot manufacture multi-color Micro-LED display devices. Description of the Drawings

[0051] Figure 1For the green LED epitaxial wafer after the first layer of bonding metal is fabricated.

[0052] Figure 2 For the drive chip after the first layer of bonding metal is fabricated.

[0053] Figure 3 For the bonded wafer formed by the first wafer-level bonding.

[0054] Figure 4 For the bonded wafer after the substrate of the green LED epitaxial wafer is removed.

[0055] Figure 5 For the bonded wafer after the second layer of bonding metal is fabricated.

[0056] Figure 6 For the red LED epitaxial wafer after the second layer of bonding metal is fabricated.

[0057] Figure 7 For the bonded wafer formed by the second wafer-level bonding.

[0058] Figure 8 For the bonded wafer after the substrate of the red LED epitaxial wafer is removed.

[0059] Figure 9 For the bonded wafer after the third layer of bonding metal is fabricated.

[0060] Figure 10 For the blue LED epitaxial wafer after the third layer of bonding metal is fabricated.

[0061] Figure 11 For the bonded wafer after the third wafer-level bonding.

[0062] Figure 12 For the bonded wafer after the substrate of the blue LED epitaxial wafer is removed.

[0063] Figure 13 For the bonded wafer after the blue LED epitaxial layer is patterned.

[0064] Figure 14 For the bonded wafer after the third layer of bonding metal under the blue LED is patterned.

[0065] Figure 15 For the bonded wafer after the red LED epitaxial layer is patterned.

[0066] Figure 16 For the bonded wafer after the second layer of bonding metal under the red LED is patterned.

[0067] Figure 17 For the bonded wafer after the green LED epitaxial wafer is patterned.

[0068] Figure 18It is a bonding wafer after the first layer of bonding metal is formed under the graphical green LED.

[0069] Figure 19 It is a schematic diagram of the bonding wafer after manufacturing the anode interconnection electrode.

[0070] Figure 20 It is the bonding wafer after manufacturing the insulating layer.

[0071] Figure 21 It is a Micro-LED display device formed after manufacturing the common cathode electrode.

[0072] Figure 22 It is a flowchart for manufacturing a multi-color Micro-LED display device according to the present invention.

[0073] Description of reference numerals in the figure: 11. Substrate of the green LED epitaxial wafer; 12. Green LED epitaxial layer; 13. First layer of bonding metal; 14. Driving chip; 15. Common cathode electrode on the driving chip; 16. Anode on the driving chip; 21. Substrate of the red LED epitaxial wafer; 22. Red LED epitaxial layer; 23. Second layer of bonding metal; 31. Substrate of the blue LED epitaxial wafer; 32. Blue LED epitaxial layer; 33. Third layer of bonding metal; 321. Single blue LED; 331. Single structure of the third layer of bonding metal; 221. Single red LED; 231. Single structure of the second layer of bonding metal; 121. Single green LED; 131. Single structure of the first layer of bonding metal; 41. Anode interconnection electrode; 51. Insulating layer; 61. Common cathode electrode. Detailed implementation manners

[0074] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0075] As Figure 22 shown, a manufacturing method of a multi-color Micro-LED display device designed by the present invention includes Step 1 to Step 11.

[0076] Step 1: Manufacture the first layer of bonding metal on the upper surface of the first-color LED epitaxial wafer and the upper surface of the driving chip, perform the first wafer-level bonding, and process the bonding wafer obtained from the first wafer-level bonding to remove the first-color LED epitaxial wafer substrate and the buffer layer, so as to form a first bonding wafer bonded with the first-color LED epitaxial layer.

[0077] Step 2: Fabricate the second bonding metal on the upper surface of the first bonding wafer and the upper surface of the second-color LED epitaxial wafer, perform the second wafer-level bonding, and process the bonded wafer obtained from the second wafer-level bonding to remove the substrate and buffer layer of the second-color LED epitaxial wafer, thereby forming a second bonding wafer bonded with the second-color LED epitaxial layer and the first-color LED epitaxial layer.

[0078] Step 3: Fabricate the third bonding metal on the upper surface of the second bonding wafer and the upper surface of the third-color LED epitaxial wafer, perform the third wafer-level bonding, and process the bonded wafer obtained from the third wafer-level bonding to remove the third-color LED epitaxial wafer and the buffer layer, thereby forming a third bonding wafer bonded with the third-color LED epitaxial layer, the second-color LED epitaxial layer, and the first-color LED epitaxial layer.

[0079] Step 4: Pattern the third-color LED epitaxial layer of the third bonding wafer to form a third-color LED patterned array including at least one third-color LED.

[0080] Step 5: Pattern the third bonding metal to form a third bonding metal patterned array. The third bonding metal patterned array includes at least one single third bonding metal structure located below the third-color LED. The vertical projection size of the third-color LED is smaller than the vertical projection size of the single third bonding metal structure below it.

[0081] Step 6: Pattern the second-color LED epitaxial layer between the third bonding metal patterned array and the second bonding metal to form a second-color LED patterned array including at least one second-color LED. The vertical projection size of the second-color LED located below a single third bonding metal structure is larger than the vertical projection size of the single third bonding metal structure.

[0082] Step 7: Pattern the second bonding metal to form a second bonding metal patterned array. The second bonding metal patterned array includes at least one single second bonding metal structure located below the second-color LED. The vertical projection size of the second-color LED is smaller than the vertical projection size of the single second bonding metal structure below it.

[0083] Step 8: Pattern the first-color LED epitaxial layer between the second bonding metal patterned array and the first bonding metal to form a first-color LED patterned array including at least one first-color LED. The vertical projection size of the first-color LED located below a single second bonding metal structure is larger than the vertical projection size of the single second bonding metal structure.

[0084] Step 9: Pattern the first layer of bonding metal to form a first-layer bonding metal patterned array. The first-layer bonding metal patterned array includes at least one single first-layer bonding metal structure located under the first-color LED. The vertical projection size of the first-color LED is smaller than the vertical projection size of the single first-layer bonding metal structure under it.

[0085] Step 10: Fabricate an anode interconnection electrode connecting the single third-layer bonding metal structure under the third-color LED and the single first-layer bonding metal structure, and fabricate an anode interconnection electrode connecting the single second-layer metal structure under the second-color LED and the single first-layer metal structure.

[0086] Step 11: Fabricate a common cathode electrode for the third-color LED patterned array, the second-color LED patterned array, and the first-color LED patterned array.

[0087] Example 1

[0088] A manufacturing method of a multi-color Micro-LED display device disclosed by the present invention specifically includes steps 1 to 20.

[0089] Step 1, fabricate the first layer of bonding metal

[0090] As Figure 1 , Figure 2 shown, the surfaces of the green light LED epitaxial chip and the driving chip 14 are cleaned by ultrasonic cleaning with acetone and isopropyl alcohol in sequence. After that, the first layer of bonding metal 13 is deposited on the upper surfaces of the two chips, i.e., the upper surface of the green light LED epitaxial layer 12 and the upper surface of the driving chip 14, respectively, by sputtering vacuum coating process. The first layer of bonding metal 13 is formed by stacking Ti, Pt, and Au in sequence. The thicknesses of the metal layers prepared by Ti, Pt, and Au are 10 nm, 20 nm, and 350 nm, respectively.

[0091] Step 2, perform the first wafer-level bonding

[0092] As Figure 3 shown, the metal surfaces of the green light LED epitaxial wafer with the first layer of bonding metal 13 fabricated and the driving chip 14 are activated to remove impurities such as metals and organic substances on the surfaces. After that, the two chips to be bonded are placed on one side of a high-pressure bonder respectively, and the bonding pressure, bonding time, and bonding temperature are set to 50000 N, 60 mins, and 300 °C respectively to achieve high-quality bonding of the two chips.

[0093] Step 3, remove the substrate of the green light LED epitaxial wafer

[0094] For Figure 3For the bonding wafer shown, first, the substrate 11 of the green LED epitaxial wafer is thinned from 1.1 mm to 0.1 mm by mechanical grinding. Then, the remaining 0.1 mm thick substrate is etched clean by deep silicon etching process. The bonding wafer after removing the substrate of the green LED epitaxial wafer is as Figure 4 shown.

[0095] Step 4: Remove the green LED buffer layer

[0096] For the Figure 4 bonding wafer shown, the green LED buffer layer exposed after removing the substrate of the green LED epitaxial wafer is removed by ICP etching. Then, the n-type doped region exposed after removing the green LED buffer layer is thinned by the same process to enhance the light efficiency of the LED. After that, the surface of the n-type doped region is polished flat by CMP.

[0097] Step 5: Fabricate the second bonding metal

[0098] As Figure 5 , Figure 6 shown, the red LED epitaxial wafer to fabricate the second bonding metal and the bonding wafer after removing the green LED buffer layer in Step 4 are cleaned ultrasonically with acetone and isopropyl alcohol in sequence. Then, the second bonding metal 23 is deposited on the upper surfaces of the two wafers to be bonded, i.e., the surface of the green LED epitaxial layer 12 without bonding metal and the upper surface of the red LED epitaxial layer 22, by sputtering vacuum coating process. The second bonding metal 23 is composed of Ti, Pt, and Au stacked in sequence. The thicknesses of the metal layers prepared by Ti, Pt, and Au are 10 nm, 20 nm, and 350 nm respectively.

[0099] Step 6: Second wafer-level bonding

[0100] As Figure 7 shown, the red LED epitaxial wafer with the second bonding metal 23 fabricated in Step 5 and the metal surface of the bonding wafer are activated to remove impurities such as metals and organic substances on the surface. Then, the two wafers to be bonded are placed on one side of a high-pressure bonder respectively, and the bonding pressure, bonding time, and bonding temperature are set to 50000 N, 60 mins, and 300 °C respectively to achieve high-quality bonding of the two wafers.

[0101] Step 7: Remove the substrate of the red LED epitaxial wafer

[0102] For the Figure 7 bonding wafer shown, first, the substrate 21 of the red LED epitaxial wafer is thinned from 1.5 mm to 0.1 mm by mechanical grinding. Then, the remaining 0.1 mm thick substrate is etched clean by deep silicon etching process. The bonding wafer after removing the substrate of the red LED epitaxial wafer is as Figure 8as shown

[0103] Step 8, removing the red LED buffer layer

[0104] For Figure 8 the bonding wafer shown, the red LED buffer layer exposed after removing the substrate of the red LED epitaxial wafer is removed by ICP etching, and then the n-type doped region exposed after removing the red LED buffer layer is thinned using the same process to enhance the light efficiency of the LED. After that, the surface of the n-type doped region is polished flat by CMP.

[0105] Step 9, fabricating the third layer of bonding metal

[0106] As Figure 9 、 Figure 10 shown, the surface of the blue LED epitaxial wafer to which the third layer of bonding metal is to be fabricated and the bonding wafer after removing the red LED buffer layer in Step 8 are cleaned by ultrasonic cleaning with acetone and isopropyl alcohol in sequence. After that, the third layer of bonding metal 33 is deposited on the upper surfaces of the two chips to be bonded, namely, the surface of the red LED epitaxial layer 22 where no bonding metal is present and the upper surface of the blue LED epitaxial layer 32, by sputtering vacuum coating process. The third layer of bonding metal 33 is composed of Ti, Pt, and Au stacked in sequence, and the thicknesses of the metal layers prepared from Ti, Pt, and Au are 10 nm, 20 nm, and 350 nm respectively.

[0107] Step 10, the third wafer-level bonding

[0108] As Figure 11 shown, the metal surfaces of the blue LED epitaxial wafer and the bonding wafer on which the third layer of bonding metal 33 is fabricated in Step 9 are activated to remove impurities such as metal and organic matter on the surface. After that, the two chips to be bonded are placed on one side of a high-pressure bonder respectively, and the bonding pressure, bonding time, and bonding temperature are set to 50000 N, 60 mins, and 300 °C respectively to achieve high-quality bonding of the two chips.

[0109] Step 11, removing the substrate of the blue LED epitaxial wafer

[0110] As Figure 11 shown for the bonding wafer, the substrate 31 of the blue LED epitaxial wafer is first thinned from 1.2 mm to 0.1 mm by mechanical grinding, and then the remaining 0.1 mm thick silicon substrate 31 is etched clean by deep silicon etching process. The bonding wafer after removing the substrate of the blue LED epitaxial wafer is as Figure 12 shown

[0111] Step 12, removing the blue LED buffer layer

[0112] For Figure 12The bonding chip shown removes the blue LED buffer layer exposed after removing the substrate of the blue LED epitaxial wafer by ICP etching, and then thins the n-type doped region exposed after removing the blue LED buffer layer using the same process to enhance the light efficiency of the LED. After that, the surface of the n-type doped region is polished flat by CMP.

[0113] Step 13, patterning the blue LED epitaxial layer

[0114] As Figure 13 shown, according to the pixel size designed on the driving chip, the blue LED epitaxial layer 32 on the surface of the bonding chip in Step 12 is etched by ICP to form a blue LED patterned array. The vertical projection size of a single blue LED 321 is 5um * 5um.

[0115] Step 14, patterning the third layer of bonding metal

[0116] As Figure 14 shown, according to the size of the blue LED patterned array, the third layer of bonding metal between the blue LED patterned array and the red LED epitaxial layer 22 is etched by IBE to form partitions, so that the single third layer of bonding metal structures under each blue LED in Step 13 are independent of each other, forming a third layer of bonding metal patterned array. The vertical projection size of each independent single third layer of bonding metal structure 331 is 6um * 6um.

[0117] Step 15, patterning the red LED epitaxial layer

[0118] As Figure 15 shown, according to the pixel size designed on the driving chip, the red LED epitaxial layer on the surface of the bonding chip in Step 14 is etched by ICP to form a red LED patterned array. The vertical projection size of a single red LED 221 without a single third layer of bonding metal structure 331 above it is 5um * 5um, and the vertical projection size of a single red LED with a single third layer of bonding metal structure 331 above it is 7um * 7um.

[0119] Step 16, patterning the second layer of bonding metal

[0120] As Figure 16As shown, according to the size of the red LED patterned array, IBE etching is performed on the second bonding metal between the red LED patterned array and the green LED epitaxial layer to form a partition, so that the single second bonding metal structures under each red LED in step 15 are independent of each other, forming a second bonding metal patterned array. The vertical projection size of the single second bonding metal structure under the red LED with a vertical projection size of 5um * 5um is 6um * 6um, and the vertical projection size of the single second bonding metal structure 231 under the red LED with a vertical projection size of 7um * 7um is 8um * 8um.

[0121] Step 17, pattern the green LED epitaxial layer 12

[0122] As Figure 17 shown, according to the pixel size designed on the driving chip, ICP etching is performed on the green LED epitaxial layer on the surface of the bonding pad in step 16 to form a green LED patterned array. The vertical projection size of a single green LED without a single second bonding metal structure above it is 5um * 5um, the vertical projection size of a single green LED with a single second bonding metal structure with a vertical projection size of 6um * 6um above it is 7um * 7um, and the vertical projection size of a single green LED with a single second bonding metal structure 231 with a vertical projection size of 8um * 8um above it is 9um * 9um.

[0123] Step 18, pattern the first bonding metal layer

[0124] As Figure 18 shown, according to the size of the green LED patterned array, IBE etching is performed on the first bonding metal between the green LED patterned array and the driving chip to form a partition, so that the single first bonding metal structures under each green LED in step 17 are independent of each other, forming a first bonding metal patterned array. The vertical projection size of the single first bonding metal structure under the green LED with a vertical projection size of 5um * 5um is 6um * 6um, the vertical projection size of the single first bonding metal structure under the green LED with a vertical projection size of 7um * 7um is 8um * 8um, and the vertical projection size of the single first bonding metal structure 131 under the green LED with a vertical projection size of 9um * 9um is 10um * 10um.

[0125] Step 19, fabricate the anode interconnection electrode

[0126] As Figure 19As shown, the anode interconnection electrode 41 is fabricated by means of negative photoresist lift-off. The single third-layer bonding metal layer structure and the single first-layer bonding metal layer structure under the blue LED are connected, so that the anode 16 on the driving chip is electrically connected to the positive electrode metal of the blue LED. The anode interconnection electrode 41 is made by vacuum thermal evaporation of Ti and Au, and the thicknesses of Ti and Au are 20 nm and 300 nm respectively. The anode interconnection electrode 41 is fabricated by means of negative photoresist lift-off. The single second-layer bonding metal structure and the single first-layer bonding metal structure under the red LED are connected, so that the anode 16 on the driving chip is electrically connected to the positive electrode metal of the red LED. The anode interconnection electrode 41 is made by vacuum thermal evaporation of Ti and Au, and the thicknesses of Ti and Au are 20 nm and 300 nm respectively. The single first-layer bonding metal structure under the green LED is directly connected to the anode 16 on the driving chip, and there is no need to fabricate the anode interconnection electrode 41 any more.

[0127] Step 20: Fabricate the common cathode electrode

[0128] As Figure 20 、 Figure 21 shown, first, an insulating layer 51 is fabricated on the bonding chip surface where the anode interconnection electrode 41 is fabricated in step 19 by means of PECVD vacuum coating method. Then, part of the insulating layer 51 on the surfaces of the red LED, green LED, and blue LED arrays is removed by means of photolithography and etching to expose the corresponding LED arrays. Finally, the ITO metal is deposited on the bonding chip surface by means of magnetron sputtering to fabricate the common cathode electrode 61, so that the cathodes of the red LED, green LED, and blue LED arrays are all connected to the common cathode electrode 15 on the driving chip. Thus, the multi-color Micro-LED device is fabricated.

[0129] It should be noted that the embodiments described above are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts, including other bonding sequences of the red LED epitaxial layer, blue LED epitaxial layer, and green LED epitaxial layer, and bonding with other color LED epitaxial layers, are also within the protection scope of this patent.

Claims

1. A manufacturing method of a multi-color Micro-LED display device, characterized in that a first layer of bonding metal is fabricated on the upper surface of the first-color LED epitaxial wafer and the upper surface of the driving chip, and the first wafer-level bonding is performed. The bonded wafer obtained from the first wafer-level bonding is processed to remove the substrate and buffer layer of the first-color LED epitaxial wafer, forming a first bonded wafer bonded with the first-color LED epitaxial layer; a second layer of bonding metal is fabricated on the upper surface of the first bonded wafer and the upper surface of the second-color LED epitaxial wafer, and the second wafer-level bonding is performed. The bonded wafer obtained from the second wafer-level bonding is processed to remove the substrate and buffer layer of the second-color LED epitaxial wafer, forming a second bonded wafer bonded with the second-color LED epitaxial layer and the first-color LED epitaxial layer; a third layer of bonding metal is fabricated on the upper surface of the second bonded wafer and the upper surface of the third-color LED epitaxial wafer, and the third wafer-level bonding is performed. The bonded wafer obtained from the third wafer-level bonding is processed to remove the third LED epitaxial wafer and buffer layer, forming a third bonded wafer bonded with the third-color LED epitaxial layer, the second-color LED epitaxial layer, and the first-color LED epitaxial layer; The third-color LED epitaxial layer of the third bonded wafer is patterned to form a third-color LED patterned array including at least one third-color LED; The third layer of bonding metal is patterned to form a third-layer bonding metal patterned array. The third-layer bonding metal patterned array includes at least one single third-layer bonding metal structure located below the third-color LED. The vertical projection size of the third-color LED is smaller than the vertical projection size of the single third-layer bonding metal structure below it; The second-color LED epitaxial layer between the third-layer bonding metal patterned array and the second layer of bonding metal is patterned to form a second-color LED patterned array including at least one second-color LED. The vertical projection size of the second-color LED located below a single third-layer bonding metal structure is larger than the vertical projection size of the single third-layer bonding metal structure; The second layer of bonding metal is patterned to form a second-layer bonding metal patterned array. The second-layer bonding metal patterned array includes at least one single second-layer bonding metal structure located below the second-color LED. The vertical projection size of the second-color LED is smaller than the vertical projection size of the single second-layer bonding metal structure below it; The first-color LED epitaxial layer between the second-layer bonding metal patterned array and the first layer of bonding metal is patterned to form a first-color LED patterned array including at least one first-color LED. The vertical projection size of the first-color LED located below a single second-layer bonding metal structure is larger than the vertical projection size of the single second-layer bonding metal structure; Pattern the first layer of bonding metal to form a first-layer bonded metal pattern array, where the first-layer bonded metal pattern array includes at least one single first-layer bonded metal structure located below the first-color LED, and the vertical projection size of the first-color LED is smaller than the vertical projection size of the single first-layer bonded metal structure below it; Fabricate an anode interconnection electrode connecting the single third-layer bonded metal structure below the third-color LED and the single first-layer bonded metal structure, and fabricate an anode interconnection electrode connecting the single second-layer metal structure below the second-color LED and the single first-layer metal structure; Fabricate the common cathode electrodes of the third-color LED pattern array, the second-color LED pattern array, and the first-color LED pattern array.

2. The manufacturing method of a multi-color Micro-LED display device according to claim 1, wherein, The sizes of the first-color LED epitaxial wafer, the second-color LED epitaxial wafer, and the third-color LED epitaxial wafer are the same as the size of the driving chip. The substrates of the first-color LED epitaxial wafer, the second-color LED epitaxial wafer, and the third-color LED epitaxial wafer are silicon-based substrates or sapphire-based substrates, and the first-color LED epitaxial wafer, the second-color LED epitaxial wafer, and the third-color LED epitaxial wafer are any combination of green LED epitaxial wafers, red LED epitaxial wafers, and blue LED epitaxial wafers.

3. The manufacturing method of a multi-color Micro-LED display device according to claim 1, characterized in that An anode electrode connected to the first layer of bonding metal is led out from the middle of each pixel unit on the surface of the driving chip, and cathode electrodes are led out around the pixel area on the surface of the driving chip. The substrate of the driving chip is a silicon-based substrate or a glass-based substrate.

4. The manufacturing method of a multi-color Micro-LED display device according to claim 1, wherein, Before each wafer-level bonding, activate the surface of the chip to be bonded to remove the metal and organic substances on the surface.

5. The manufacturing method of a multi-color Micro-LED display device according to claim 1, characterized in that The bonding surfaces of the first layer, second layer, and third layer of bonding metal are made of Au and Sn, the adhesion layer is made of Ti and Ni, and the barrier layer is made of Pt.

6. The manufacturing method of a multi-color Micro-LED display device according to claim 1, characterized in that, The specific method for removing the LED epitaxial wafer substrate and buffer layer from the bonded wafer obtained by each wafer-level bonding is as follows: thin the LED epitaxial wafer substrate by mechanical grinding, and etch the remaining LED epitaxial wafer substrate clean by deep silicon etching process; remove the buffer layer exposed after removing the LED outer wafer substrate by ICP etching process, thin the n-type doped region exposed after removing the buffer layer by ICP etching process, and polish and flatten the surface of the thinned n-type doped region by CMP.

7. The manufacturing method of a multi-color Micro-LED display device according to claim 1, characterized in that The method for patterning each color LED epitaxial layer is to perform ICP etching on each color LED epitaxial layer.

8. The manufacturing method of a multi-color Micro-LED display device according to claim 1, characterized in that, The method for patterning each layer of bonding metal is to perform IBE etching on each layer of bonding metal.

9. The manufacturing method of a multi-color Micro-LED display device according to claim 1, wherein, Use the method of negative photoresist stripping of metal to fabricate the anode interconnection electrode connecting the single third-layer bonded metal structure below the third-color LED and the single first-layer bonded metal structure, and the anode interconnection electrode connecting the single second-layer metal structure below the second-color LED and the single first-layer metal structure.

10. The manufacturing method of a multi-color Micro-LED display device according to claim 1, characterized in that, The method for fabricating the common cathode electrodes of the third-color LED patterned array, the second-color LED patterned array, and the first-color LED patterned array is as follows: An insulating layer is fabricated on the surface of the bonding pad with the anode interconnection electrodes already fabricated through PECVD vacuum coating. The insulating layer covering the third-color LED patterned array, the second-color LED patterned array, and the first-color LED patterned array is etched, and ITO is deposited on the surface of the bonding pad after the insulating layer etching through magnetron sputtering to prepare the common cathode electrodes.

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