A method for etching metal in VCSEL chips

Abstract

This invention discloses a method for etching metal in VCSEL chips, relating to the field of etching technology. To avoid the roughness problem after dry etching, this invention improves the VCSEL chip metal etching method. First, a positive photoresist is used as a mask to expose the surface of the VCSEL chip epitaxial wafer. Then, dry etching is used to initially etch the surface of the epitaxial wafer. During dry etching, BCl2 and Cl2 are used as etching gases, and nitrogen is added to induce the formation of a passivation layer, preventing lateral etching. Based on this, an etching solution is used to etch and smooth the VCSEL chip epitaxial wafer. Potassium permanganate is used to oxidize the uneven areas after etching, facilitating the etching with phosphoric acid. Furthermore, to avoid defects such as oxide spots due to excessive oxidation, this invention strictly limits the potassium permanganate content, achieving smoothing of the VCSEL chip epitaxial wafer after dry etching and effectively improving the etching quality of the VCSEL chip.

Description

Technical Field

[0001] This invention relates to the field of etching technology, specifically a method for etching metal in VCSEL chips. Background Technology

[0002] GaAs-based materials, due to their unique properties, are widely used in various fields such as semiconductor lasers, photodetectors, and aerospace devices, especially playing a crucial role in the manufacture of semiconductor lasers. GaAs-based VCSELs (vertical-cavity surface-emitting lasers) have been widely used in 3D imaging, autonomous driving, the Internet of Things, and data communication, while also demonstrating great potential and role in high-precision technology fields such as optoelectronic countermeasures, lidar, and aerospace. Etching technology is a crucial step in the fabrication process of GaAs-based VCSELs, and the etching process is a process that complements photolithography. During etching, the choice of etching process will seriously affect the quality of the photomask, and the quality of the photomask will seriously affect the quality of the GaAs surface after etching, ultimately directly affecting the final performance of the device. Currently, VCSEL etching is mainly divided into two methods: wet etching and dry etching. Dry etching is a technique that uses plasma bombardment or corrosive gas to etch wafers that are not protected by a mask. Because dry etching has advantages such as high precision, good controllability, suitability for mass production, and high process cleanliness, it is generally used for etching GaAs-based VCSELs to ensure precise control of the morphology. However, GaAs-based VCSELs suffer from surface roughness issues after dry etching, so further improvements to the etching process are needed. Summary of the Invention

[0003] The purpose of this invention is to provide a method for etching metal in VCSEL chips to solve the problems mentioned in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a VCSEL chip metal etching method, comprising the following steps:

[0005] S1. After ultrasonic cleaning of the epitaxial wafer, dry its surface until dry, spin-coat photoresist onto its surface, heat to 100-110℃ and dry for 10 minutes, cool to room temperature and expose and develop its surface, then heat to 100-110℃ again and dry and harden the film for 10 minutes, then set aside.

[0006] The method for preparing the photoresist is as follows:

[0007] After mixing n-butyl acrylate and phenolic resin, solvent and leveling agent are added, and mixing is continued for 10-15 minutes. After vacuum degassing, diazonoquinone photosensitizer is added again, and mixing is continued for 5-10 minutes. After vacuum degassing, photoresist is obtained.

[0008] S2. Place the developed epitaxial wafer in a plasma chamber, fill it with etching gas, and perform an etching process on the surface of the epitaxial wafer.

[0009] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150-200s, remove the epitaxial wafer and rinse it with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean it again with anhydrous ethanol for 10-20min, and set it aside.

[0010] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10-15 min, then heat to 100-110℃ and dry for 5-10 min to complete the etching.

[0011] Furthermore, in step S1, when cleaning the epitaxial wafer, the surface is washed for 10-20 minutes with acetone, deionized water and anhydrous ethanol at a temperature of 45-55℃, respectively.

[0012] Further, in step S1, the photoresist is composed of 2.4-5 parts of n-butyl acrylate, 10-15 parts of phenolic resin, 20-60 parts of solvent, 0.05-0.15 parts of leveling agent and 2-4 parts of diazonaphthoquinone photosensitizer by weight.

[0013] The solvent is at least one of acetone and butyl acetate; the leveling agent is vinyltriethoxysilane.

[0014] Furthermore, in step S2, the etching gas is composed of BCl3, Cl2, and N2 in a volume ratio of (1-1.5):1:1.

[0015] Furthermore, in step S2, the total flow rate of the etching gas is 80-200 sccm.

[0016] Furthermore, in step S2, during etching, the bias power is set to 200-300W and the inductively coupled plasma power is set to 300-800W.

[0017] Furthermore, in step S3, the preparation method of the potassium permanganate phosphate etching solution is as follows:

[0018] After purging nitrogen gas into deionized water for 15-30 minutes, phosphoric acid is added, and the mixture is ultrasonically vibrated for 30-60 minutes. Then, potassium permanganate is added again, and the mixture is ultrasonically vibrated for another 10-30 minutes to obtain a potassium permanganate phosphate etching solution.

[0019] Furthermore, in step S3, the ratio of phosphoric acid: potassium permanganate: deionized water in the potassium permanganate etching solution is 70-95g: 3-7g: 1L.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] To avoid the roughness problem after dry etching, this invention improves the metal etching method for VCSEL chips;

[0022] By using a two-step method, firstly, photoresist is used as a mask on the epitaxial wafer of the VCSEL chip. The photoresist prepared in this invention is diazonoquinone, which uses a positive photosensitive agent and has high precision, so it can provide good protection for the epitaxial wafer of the VCSEL chip. After the surface is exposed, dry etching is used to perform preliminary etching on the surface of the epitaxial wafer. During dry etching, this invention uses BCl2 and Cl2 as etching gases and adds nitrogen gas to induce the formation of a passivation layer to prevent the formation of lateral etching that would affect the quality of the VCSEL chip.

[0023] Furthermore, based on this, the present invention also uses an etching solution to etch and smooth the VCSEL chip epitaxial wafer. In the etching solution, phosphoric acid is used as a hydrogen ion donor, and potassium permanganate, which has strong oxidizing properties, is used as a raw material. After the uneven areas are etched by potassium permanganate, it facilitates the etching of phosphoric acid. In order to avoid the defect of oxide spots in the etched area due to excessive oxidizing properties, the present invention also strictly limits the potassium permanganate content. By controlling the potassium permanganate content, the smoothing treatment of the VCSEL chip epitaxial wafer after dry etching is achieved, which effectively improves the etching quality of the VCSEL chip, thereby improving the consistency and reliability of the device, and fully ensuring the subsequent interlayer bonding, optical performance and laser efficiency. Detailed Implementation

[0024] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The method for preparing the photoresist used in this application embodiment is as follows:

[0026] By weight, 4 parts of n-butyl acrylate resin and 12 parts of phenolic resin were mixed, then 45 parts of butyl acetate solvent and 0.1 parts of vinyltriethoxysilane were added. After mixing for 15 minutes, the mixture was degassed under vacuum. Then, 3 parts of diazonoquinone photosensitizer were added and the mixture was mixed for 8 minutes. After degassed under vacuum, the photoresist was obtained.

[0027] The phenolic resin used in this application is commercially available SH-3088 linear phenolic resin.

[0028] Example 1. A method for etching metal in a VCSEL chip, comprising the following steps:

[0029] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0030] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0031] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0032] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0033] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:3 g:1 L.

[0034] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0035] Example 2. A method for etching metal in a VCSEL chip, comprising the following steps:

[0036] Compared with Example 1, this example increases the proportion of BCl3 in step S2;

[0037] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0038] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1.2:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0039] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0040] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0041] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:3 g:1 L.

[0042] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0043] Example 3. A method for etching metal onto a VCSEL chip, comprising the following steps:

[0044] Compared with Example 1, this example increases the proportion of BCl3 in step S2.

[0045] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0046] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1.5:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0047] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0048] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0049] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:3 g:1 L.

[0050] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0051] Example 4. A method for etching metal onto a VCSEL chip, comprising the following steps:

[0052] Compared with Example 1, this example increases the etching time in step S3;

[0053] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0054] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0055] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 180s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0056] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0057] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:3 g:1 L.

[0058] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0059] Example 5. A method for etching metal onto a VCSEL chip, comprising the following steps:

[0060] Compared with Example 1, this example increases the etching time in step S3;

[0061] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0062] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0063] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 200s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0064] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0065] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:3 g:1 L.

[0066] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0067] Example 6. A method for etching metal onto a VCSEL chip, comprising the following steps:

[0068] Compared with Example 1, this example increases the amount of potassium permanganate added in step S3;

[0069] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0070] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1.2:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0071] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0072] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0073] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:5 g:1 L.

[0074] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0075] Example 7. A method for etching metal onto a VCSEL chip, comprising the following steps:

[0076] Compared with Example 1, this example increases the proportion of potassium permanganate in step S3;

[0077] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0078] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0079] S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150s, remove the epitaxial wafer and rinse with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean with anhydrous ethanol for 20min, and set aside.

[0080] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0081] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:6 g:1 L.

[0082] S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0083] Comparative Example 1. A method for etching metal in a VCSEL chip, comprising the following steps:

[0084] Compared with Example 1, this comparative example did not perform the original S3 step;

[0085] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0086] S2. Place the developed epitaxial wafer in a plasma chamber and fill it with an etching gas composed of BCl3, Cl2 and N2 in a volume ratio of 1:1:1. Control the total flow rate of the etching gas to 100 sccm, set the bias power to 200W, and the inductively coupled plasma power to 400W to perform an etching process on the surface of the epitaxial wafer.

[0087] S3. Remove the photoresist from the epitaxial wafer surface, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0088] Comparative Example 2. A method for etching metal in a VCSEL chip, comprising the following steps:

[0089] Compared with Example 1, this comparative example did not perform the original step S2.

[0090] S1. Place the GaAs substrate VCSEL epitaxial wafer in acetone, deionized water and anhydrous ethanol at 50±2℃ respectively, and ultrasonically clean the surface for 10 min. After drying the surface, spin-coat the surface with AZ5214 photoresist, heat to 100℃ and dry for 10 min. After cooling to room temperature, use an ABM Inc. UV exposure machine to expose and develop the surface at a wavelength of 365nm. After exposure and development, heat to 110℃ again and dry and harden the film for 10 min.

[0091] S2. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer to it, ultrasonically vibrate, treat for 150s, remove the epitaxial wafer and rinse it with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean it again with anhydrous ethanol for 20min, and set it aside.

[0092] The preparation method of the potassium permanganate phosphate etching solution is as follows:

[0093] After passing nitrogen gas through deionized water for 18 minutes, phosphoric acid was added, and the mixture was ultrasonically vibrated for 30 minutes. Potassium permanganate was then added, and the mixture was ultrasonically vibrated for another 25 minutes to obtain a potassium permanganate phosphate etching solution. The ratio of phosphoric acid:potassium permanganate:deionized water in the potassium permanganate phosphate etching solution was 70 g:3 g:1 L.

[0094] S3. Remove the photoresist from the epitaxial wafer surface after step S2, wash again with acetone and anhydrous ethanol for 10 min each, then heat to 110℃ and dry for 8 min to complete the etching.

[0095] Testing: The surface roughness of Examples 1-7 and Comparative Example 2 was measured using a profilometer. The test results are shown in the table below.

[0096]

[0097] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for etching metal onto a VCSEL chip, characterized in that, Includes the following steps: S1. After ultrasonic cleaning of the epitaxial wafer, dry its surface until dry, spin-coat photoresist onto its surface, heat to 100-110℃ and dry for 10 minutes, cool to room temperature and expose and develop its surface, then heat to 100-110℃ again and dry and harden the film for 10 minutes, then set aside. The method for preparing the photoresist is as follows: After mixing n-butyl acrylate and phenolic resin, solvent and leveling agent are added, and mixing is continued for 10-15 minutes. After vacuum degassing, diazonoquinone photosensitizer is added again, and mixing is continued for 5-10 minutes. After vacuum degassing, photoresist is obtained. S2. Place the developed epitaxial wafer in a plasma chamber, fill it with etching gas, and perform a first etching process on the surface of the epitaxial wafer. S3. Cool the potassium permanganate phosphate etching solution to 0-2℃, add the epitaxial wafer after the first etching treatment, ultrasonically vibrate, treat for 150-200s, remove the epitaxial wafer and rinse it with deionized water, then place it in anhydrous acetone again, ultrasonically vibrate and clean for 10min, then ultrasonically clean it again with anhydrous ethanol for 10-20min, and set it aside. S4. Remove the photoresist from the epitaxial wafer surface after step S3, wash again with acetone and anhydrous ethanol for 10-15 min, then heat to 100-110℃ and dry for 5-10 min to complete the etching.

2. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S1, when cleaning the epitaxial wafer, the surface is washed for 10-20 minutes with acetone, deionized water and anhydrous ethanol at a temperature of 45-55℃.

3. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S1, the photoresist, by weight, is composed of 2.4-5 parts of n-butyl acrylate, 10-15 parts of phenolic resin, 20-60 parts of solvent, 0.05-0.15 parts of leveling agent and 2-4 parts of diazonaphthoquinone photosensitizer. The solvent is at least one of acetone and butyl acetate; the leveling agent is vinyltriethoxysilane.

4. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S2, the etching gas is composed of BCl3, Cl2, and N2 in a volume ratio of (1-1.5):1:

1.

5. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S2, the total flow rate of the etching gas is 80-200 sccm.

6. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S2, during etching, the bias power is set to 200-300W and the inductively coupled plasma power is set to 300-800W.

7. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S3, the preparation method of the potassium permanganate phosphate etching solution is as follows: After purging nitrogen gas into deionized water for 15-30 minutes, phosphoric acid is added, and the mixture is ultrasonically vibrated for 30-60 minutes. Then, potassium permanganate is added again, and the mixture is ultrasonically vibrated for another 10-30 minutes to obtain a potassium permanganate phosphate etching solution.

8. The VCSEL chip metal etching method according to claim 1, characterized in that: In step S3, the ratio of phosphoric acid: potassium permanganate: deionized water in the potassium permanganate etching solution is 70-95g: 3-7g: 1L.

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