Red light Micro LED device substrate selective corrosion method

Abstract

The invention belongs to the technical field of Micro-LED, and particularly relates to a Micro-LED device substrate selective corrosion implementation method, which comprises the following steps of: introducing an acid and alkali resistant nitride film to wrap a wafer in a silicon-based IC (Integrated Circuit) driving process, and forming a metal contact layer by utilizing a method of forming a hole in the etched film and then evaporating metal, thereby obtaining the selective corrosion of the substrate of a Micro-LED device. And then interconnection with an epitaxial wafer is carried out through a metal diffusion bonding mode, and finally thinning corrosion is carried out on an epitaxial substrate. The method is simple and convenient, the epitaxial substrate can be directly removed after epitaxy and drive circuit bonding, and a process does not need to be additionally introduced to protect the silicon-based IC.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon-based Micro-LED, and specifically relates to a method for selectively etching a substrate of a red light Micro-LED device. Background Art

[0002] Among various new display technologies, Micro-LED, as a lighting and display technology based on the highly efficient and stable third-generation semiconductor gallium nitride material, plays an irreplaceable role. As a highly integrated and miniaturized active light-emitting device array, coupled with its own characteristics such as ultra-fast response speed, low operating voltage, ultra-stability, high light output efficiency and wide operating temperature range, the Micro-LED array is highly applicable in many fields such as micro-lighting, backlight-free micro-display, and optical communication.

[0003] The preparation process of red light Micro-LED device epitaxy using sapphire substrate or silicon substrate is relatively immature. The current mature red light epitaxy in the industry is mostly prepared using aluminum gallium indium phosphide system materials. The substrate gallium arsenide is lattice-matched with the aluminum gallium indium phosphide material, and high-quality epitaxy can be grown. However, the gallium arsenide substrate will absorb the light emitted by the device, greatly affecting the optical properties of the device. The gallium arsenide substrate needs to be removed in the production process. The gallium arsenide substrate is mainly removed by wet method, that is, the etching solution is used to react with the substrate to remove the gallium arsenide. However, the etching solution will damage the IC drive circuit, and it is impossible to selectively corrode the silicon substrate while retaining the silicon-based IC drive circuit. Therefore, it is particularly important to develop a method for selectively etching the substrate of Micro-LED devices. Summary of the invention

[0004] In view of the problem that the removal of the substrate in the prior art causes damage to the IC driving circuit, the present invention proposes a method for selectively etching the substrate of a MicroLED device.

[0005] The present invention provides a method for selectively etching a substrate of a red light Micro-LED device, comprising the following steps: 1) Depositing metal on a silicon-based IC wafer to form a mesa; 2) Use thin film deposition technology to deposit a mask, which covers the front and back sides of the silicon-based IC wafer; 3) Use an etching process to etch away part of the mask to expose the deposited metal part; 4) Depositing metal as contact metal on the side of the silicon-based IC wafer; 5) Evaporating metal on the GaAs substrate epitaxial wafer and bonding the epitaxial wafer to the silicon-based IC wafer using a thermal compression bonding process; 6) The substrate is treated with cutting, thinning and etching solvent to obtain a selectively etched device.

[0006] In step 1), the deposited metal is a metal that has good adhesion to the silicon-based IC wafer and is easy to remove using a metal stripping process.

[0007] Furthermore, the metal is selected from Ni, Au, Cr, Pt, Ti or Pd.

[0008] In step 2), the thin film deposition technology is atomic layer deposition or chemical vapor deposition. As the best embodiment of the present invention, atomic layer deposition is the best deposition method. Compared with the traditional deposition process, atomic layer deposition can ensure the uniformity of large-area film formation, and it is dense and pinhole-free, and can achieve sub-nanometer-level film thickness control.

[0009] Furthermore, the thin film deposition material is SiN X , SiN X The film deposition thickness is 500-800nm ​​and the deposition temperature is 400-500℃.

[0010] As another embodiment of the present invention, the thin film deposition material is AlN, the AlN thin film deposition thickness is 500-800nm, and the deposition temperature is 300-400°C.

[0011] In step 3), the etching process is reactive ion etching, ion beam etching or inductively coupled plasma etching. As the best embodiment of the present invention, inductively coupled plasma etching is the preferred etching method, and the etching gas is CF 4 , S.F. 6 、SiCl 4 or NF 3 .

[0012] In step 4), the deposited metal structure uses Ni, Au, Cr, Pt, Ti or Pd and their combinations, the part in contact with the air is Au, the Au thickness is 4000-8000A, and the evaporation method is electron beam evaporation, magnetron sputtering, etc.

[0013] In step 5), the metal evaporation method is: using electron beam evaporation equipment for evaporation, the evaporated metal is Au, and the Au thickness is 4000-10000A.

[0014] In step 6), the cutting and thinning method is to use a dual-axis grinding and polishing machine, the grinding liquid abrasive is selected from boron carbide with a particle size of 15um, the pressure is set to 1.2-1.5kg, the grinding wheel is an iron grinding wheel, the grinding and polishing speed is 30-60 rpm, and the gallium arsenide substrate epitaxial wafer is thinned to 200um and then the grinding and polishing is stopped, and the patch is rinsed with deionized water.

[0015] In step 6), the corrosion solvent is an oxidizing acid or weak alkaline solution. Specifically, the corrosion solvent is sulfuric acid, hydrogen peroxide, hydrochloric acid, hydrogen peroxide, phosphoric acid, hydrogen peroxide; ammonia water, hydrogen peroxide. The above solution ratio can be adjusted according to the sample conditions, and the solution temperature is controlled at 25-40°C.

[0016] The selective etching method for the substrate of a Micro-LED device provided by the present invention improves the device preparation process, uses silicon nitride as a passivation layer on the driving circuit, and adopts a coating method to protect the circuit. Silicon nitride can withstand most acid and alkali corrosion at room temperature, which is conducive to the lossless removal of substrate materials and reduces the difficulty and cost of process technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the metal table structure. Figure 2 Schematic diagram of the protective film deposition structure. Figure 3 Schematic diagram of the etched hole structure. Figure 4 Schematic diagram of the metal bump preparation structure. Figure 5 Schematic diagram of metal evaporation structure. Figure 6 Schematic diagram of the thermal compression bonding structure. Figure 7 Schematic diagram of substrate removal structure. DETAILED DESCRIPTION

[0018] Embodiment 1: The embodiment of the present invention uses inorganic materials as acid etching masks to etch the gallium arsenide substrate of the red light epitaxial wafer and retain the silicon-based IC. The specific steps include: 1) Use an air gun to purge the silicon-based IC wafer, soak it in acetone and alcohol, and then rinse it with deionized water for 10 minutes. After rinsing, use a spin dryer to dry it; use a spin coating device to apply negative photoresist on the silicon-based IC drive circuit, with a thickness of 2-3um, and dry it after coating. The drying temperature is 80-90℃ and maintained for 5-7 minutes. After baking, use a photolithography machine with a corresponding mask pattern mask to expose the wafer. After exposure, use an alkaline developer to remove the photoresist that does not react with ultraviolet light, leaving a metal deposition pattern. After development, rinse it with deionized water for 8-10 minutes. After rinsing, use a spin dryer to dry it. Use electron beam evaporation equipment to evaporate bonding metal on the epitaxial wafer. The metal material structure is Cr / Pt / Au, the thickness of Cr is 40-100nm, the thickness of Pt is 100-200nm, and the thickness of Au is 100-500nm.

[0019] 2) Use atomic layer deposition equipment to deposit SiN on silicon-based IC wafers X Corrosion protection film deposition, deposition thickness is 500-800nm, deposition temperature is 400-500℃. Thin film deposition is required on both sides of silicon-based IC wafers.

[0020] 3) Use photolithography to etch away the SiN X Part of the metal surface is exposed, and the rest of the area is still protected by photoresist. Then, inductively coupled plasma etching is used to remove the SiN X Etch away to expose the deposited metal part.

[0021] 4) Use photolithography technology to protect the areas other than the atomic layer deposition opening with photoresist, and use electron beam evaporation equipment to perform metal evaporation. The evaporated metal is Au, and the Au thickness is 5000A; metal is evaporated on the epitaxial side of the silicon substrate, and the metal structure is Au with a thickness of 4000A.

[0022] 5) The metal on the epitaxial side of the silicon substrate was first ultrasonically cleaned with acetone and ethanol solutions for 5 minutes, and then rinsed with deionized water for 10 minutes. The metal surface was then treated to reduce the roughness, and the wafer surface was treated with a plasma degumming machine for 3 minutes; the silicon-based IC wafer and the silicon substrate epitaxial were bonded by a hot press bonding machine, with a bonding temperature of 300°C, a bonding pressure of 15Mpa, and a pressure holding time of 60 minutes.

[0023] 6) Use a dual-axis grinding and polishing machine for thinning operations. The grinding liquid abrasive uses boron carbide with a particle size of 15um, the pressure is set to 1.2-1.5kg, the grinding wheel uses an iron grinding wheel, and the grinding and polishing speed is 30-60 rpm. After the silicon substrate epitaxial wafer is thinned to 200um, stop grinding and polishing, and rinse the wafer with deionized water; put the thinned wafer into a corrosion solution of phosphoric acid: hydrogen peroxide: water = 5:3:3, soak for 20 minutes, remove the gallium arsenide substrate, rinse with deionized water for 10 minutes, and then dry it with a spin dryer.

[0024] In summary, the technical solution of this embodiment is helpful for the selective corrosion of silicon materials, which can well protect the silicon-based IC driving circuit, solve the impact of the use of gallium arsenide etching solution on the IC driving circuit, and can effectively improve the production efficiency of Micro-LED products and reduce costs.

Claims

1. The present invention provides a method for selectively etching a substrate of a red light Micro LED device. It is characterized by the following steps: 1) Depositing metal on silicon-based IC to form a mesa; 2) Use thin film deposition technology to deposit a mask, which covers the front and back sides of the silicon-based IC; 3) Use an etching process to etch away part of the mask to expose the deposited metal part; 4) Depositing metal as contact metal on the silicon-based IC side; 5) Evaporating metal on the silicon substrate / GaAs substrate epitaxial wafer, and bonding the epitaxial wafer to the IC drive circuit using a hot pressing bonding process; 6) The substrate is treated with cutting, thinning and etching solvent to obtain a selectively etched device.

2. In step 1) of claim 1, the deposited metal is a metal material with high conductivity.

3. In the step 2) of claim 1, the thin film is deposited using silicon nitride or aluminum nitride as the deposition material.

4. In step 2) of claim 1, the thin film is deposited on the side at the driving end of the silicon-based IC.

5. In step 2) of claim 1, the thin film is deposited on the front and back sides of the silicon-based IC wafer to protect the wafer.

6. The thin film deposition in step 2) as claimed in claim 1 is carried out by ALD.

7. In the etching process in step 3) as claimed in claim 1, the etching equipment is preferably ICP etching, and the etching gas is CF4, SF6, SiCl4 or NF3.

8. In step 4) of claim 1, the deposited metal structure is composed of Ni, Au, Cr, Pt, Ti, Pd and multiple combinations thereof, the metal in contact with air is Au, and the Au thickness is 4000-8000A.

9. In step 5) of claim 1, metal is deposited, wherein the deposited metal structure is Au.

10. The thinning method in step 6) of claim 1 is to use a dual-axis grinding and polishing machine, the grinding liquid abrasive is selected from boron carbide with a particle size of 15um, the pressure is set to 1.2-1.5kg, the grinding disc is an iron grinding disc, the grinding and polishing speed is 30-60 rpm, and the silicon substrate epitaxial wafer is thinned to 200um and then the grinding and polishing is stopped, and the patch is rinsed with deionized water.

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