A fabrication process for a differential pressure sensor

Abstract

This invention provides a fabrication process for a differential pressure sensor. The differential pressure sensor includes a housing with a cavity and a chip assembly and connectors located within the housing. The connectors include a first annular ring on the outer side and a second annular ring on the inner side, forming an annular channel between the first and second annular rings. The horizontal cross-sectional area of ​​the annular channel gradually increases in the direction away from the chip. The fabrication process includes injecting epoxy resin into the annular channel to separate the internal and external gas pressures of the chip assembly. The fabrication process of this invention achieves a high-performance, high-sensitivity differential pressure sensor through mold fabrication and optimized process parameter settings. Simultaneously, the encapsulation structure design achieves absolute isolation between the two cavities of the chip.

Description

Technical Field

[0001] This invention relates to the technical field of differential pressure sensors, and in particular to a manufacturing process for a differential pressure sensor. Background Technology

[0002] The existing differential pressure sensors are implemented in the following ways: (1) mechanical structure, such as patent 200910000717.5, which adopts a pure mechanical structure. When there is differential pressure, the two elastic elements produce different deformations, which causes the linkage to move and the pointer to rotate through the gear set; (2) diaphragm structure, such as patent 201310627068.8, where differential pressure causes the diaphragm to deform. The diaphragm is designed with strain resistors. The greater the differential pressure, the greater the deformation of the diaphragm. The piezoresistive effect causes the resistance value of the strain resistor to change more, and the output voltage of the Wheatstone bridge composed of the strain resistors is greater. For the first method, the mechanical structure generally has low sensitivity and is difficult to measure small differential pressures. For the second method, higher sensitivity can be achieved. Compared with the first method, it also has advantages such as small size and low price, but the sensitivity is still not very high.

[0003] In view of this, the inventors specifically designed a manufacturing process for a differential pressure sensor, which led to this invention. Summary of the Invention

[0004] The problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a high-sealing-performance MEMS gas differential pressure sensor. This addresses the low sensitivity of existing gas differential pressure sensors, enabling the measurement of relative vacuum in the range of 0Pa-10000Pa, exhibiting piecewise linearity, and achieving a measurement resolution better than 0.5Pa. The specific technical solution of this invention is as follows:

[0005] A fabrication process for a differential pressure sensor, the differential pressure sensor comprising a housing with a cavity and a chip assembly and connector located within the housing, wherein the connector comprises a first annular ring disposed on the outer side and a second annular ring disposed on the inner side, an annular channel being formed between the first annular ring and the second annular ring, the horizontal cross-sectional area of ​​the annular channel gradually increasing along the direction away from the chip; the fabrication process includes injecting epoxy resin into the annular channel to separate the internal and external air pressure of the chip assembly.

[0006] Furthermore, the chipset includes a second glass sheet and a chip.

[0007] Furthermore, the fabrication process also includes a chipset fabrication process, which includes the following steps:

[0008] Step S01: Cleaning of the silicon oxide wafer and the first glass sheet;

[0009] Step S02: Photolithographic development of silicon oxide wafer and first glass plate;

[0010] Step S03: Perform magnetron sputtering on the first glass sheet;

[0011] Step S04: Perform plasma etching on the silicon oxide wafer;

[0012] Step S05: Perform back-side photolithography on the silicon oxide wafer from step S04 and remove the oxide layer;

[0013] Step S06, anodic bonding: The metal surface of the first glass plate and the etched surface of the silicon oxide plate are placed in a chip bonding machine for bonding to form a primary electrostatic bonding seal;

[0014] Step S07, Second glass slide scribing: Scribing the glass slide using a scribing machine with a grinding wheel;

[0015] Step S08, laser drilling: A 2mm diameter hole is drilled in the center of the second glass sheet using laser drilling to protect the inner film from adhesion during glue injection;

[0016] Step S09, Differential pressure chamber bonding: The second glass sheet after drilling is bonded to the chip;

[0017] Furthermore, in step S01, the sample is first boiled in solution No. 3 for 20-40 minutes and then dried. Then it is placed in a vacuum oven and dried for 30-60 minutes. Solution No. 3 is hydrogen peroxide and concentrated sulfuric acid, and the ratio of the two is 1:3.

[0018] Furthermore, the photolithography development in step S02 employs the following steps:

[0019] Step S21, coating: Apply tackifier and photoresist in sequence, coat with a spin coater and then dry.

[0020] Step S22, photolithography: The silicon oxide wafer and the first glass plate are exposed using a photolithography machine and a film plate;

[0021] Step S23, Development: The exposed sample is placed in the developing solution for development to reveal the pattern. The development time is 60-80 seconds.

[0022] Furthermore, the coating sequence in step S21 is as follows: tackifier, spin coater 50r 3s, 2500r 60s, 5214-E photoresist, spin coater 50r 3s, 2500r 60s, heating plate 96℃ 4min;

[0023] In step S22, specifically: the photoresist is 5214-E, the spin coating speed is 2500 r / min, the mercury lamp intensity is 9-11, and the exposure time is 20-30 s.

[0024] Furthermore, in step S03, magnetron sputtering includes the following steps:

[0025] Step S31, Sputtering: Sputter a chromium + aluminum metal layer on the surface by magnetron sputtering;

[0026] Step S32, stripping: Immerse the sputtered sample in a 5%-10% acetone solution and let it stand for 8-24 hours. Use a clean cotton swab to strip off the excess metal layer outside the structure.

[0027] Furthermore, in step S04, the plasma etching includes the following steps:

[0028] Step S41, Coating: Coating the back of the silicon oxide wafer with adhesive and baking at high temperature for 15-30 minutes to create a protective layer; This step is for protection, and the photoresist, spin coating parameters, etc. can be the same as above. After baking at a low temperature of 96℃ for 4 minutes, it can be transferred to a high temperature of 135℃ and baked for another 15-30 minutes.

[0029] Step S42, remove oxide layer: wash with hydrofluoric acid solution to remove the silicon dioxide layer of the exposed surface and the patterned structure area. The area outside the pattern is protected by photoresist and is not affected.

[0030] Step S43, Etching: Plasma etching for 4 micrometers;

[0031] Step S44, Photoresist removal: Acetone is used to remove residual plasma chemicals and photoresist, followed by alcohol cleaning, and then the silicon oxide wafer is cleaned with solution No. 3, which consists of hydrogen peroxide and concentrated sulfuric acid in a ratio of 1:3.

[0032] Furthermore, in step S05, a silicon oxide wafer is etched using plasma etching. Specifically,

[0033] Step S51: After washing the silicon oxide wafer with solution No. 3, place it in an oven and bake at high temperature for 30 minutes to prepare for photolithography; if the silicon oxide wafer is left for a long time, it needs to be washed with solution No. 3 again.

[0034] Step S52, apply adhesive;

[0035] Step S53, Photolithography: Perform a second exposure on the back side of the silicon oxide wafer.

[0036] Step S54, development.

[0037] Furthermore, in step S05, the oxide layer is removed by using hydrofluoric acid solution to remove the oxide layer of the current photolithographic structure and all the oxide layer of the first photolithographic surface; then it is cleaned.

[0038] Furthermore, the cleaning is performed using the following method:

[0039] Step S55, Cleaning with solution No. 3: Place hydrogen peroxide and concentrated sulfuric acid in a container with a ratio of 1:3, place the container on a heating plate and heat to 230-250℃ and boil for 20-40 minutes, then rinse with deionized water 6-8 times with a rinsing cup.

[0040] Step S56, Wash BOE solution: Soak for 5 minutes and then rinse with deionized water once. Repeat this process 3-5 times until the photolithographic pattern area shows signs of dehydration.

[0041] Step S57, washing with acetone and alcohol: Immerse the sample in acetone and stir it with tweezers for 2-5 minutes, then replace with fresh acetone and repeat the operation. Then rinse with alcohol and deionized water, and finally dry with a nitrogen gun.

[0042] Furthermore, in step S07, taking a 9.2mm*9.2mm first glass slide as an example, the sample is placed on the worktable of the dicing machine, and vacuum adsorption is turned on. The glass dicing cutter is loaded, and then the parameters are set on the dicing machine operation panel: spindle speed 15000r / min, step 9.2*10.7mm, workpiece thickness: 1mm, allowance thickness: 0.15mm, and feed speed: 3mm / s.

[0043] A second glass sheet will also be needed for later drilling and bonding. The parameters are as follows: step size 9.2*9.2mm, workpiece thickness 0.5mm, and other parameters are the same as above.

[0044] Manually align the cutter position using the panel display and calculate the number of cuts.

[0045] Furthermore, in step S08, a laser is used to drill holes in the second glass sheet of 9.2*9.2mm, with the holes located at the geometric center of 9.2*9.2mm ±1mm.

[0046] Furthermore, in step S09, the bonding position is located on the annular upper surface of the silicon surface of the anodic bonding (silicon + glass) component and the surface of the 9.2*9.2 second glass sheet, with the planar coordinates being ±1mm from the geometric center of the annular structure.

[0047] The coating sequence is as follows: tackifier, spin coater 50r 3s, 2500r 60s, 5214-E photoresist, spin coater 50r 3s, 2500r 60s, heating plate 96℃ 4min.

[0048] The beneficial effects of this invention are as follows:

[0049] First, by fabricating the mold and optimizing the process parameters, a high-performance and high-sensitivity differential pressure sensor can be achieved.

[0050] Second, the absolute isolation between the two cavities of the chip is achieved through the structural design of the packaging. Attached Figure Description

[0051] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention.

[0052] in:

[0053] Figure 1 This is a cross-sectional view of the differential pressure sensor of the present invention;

[0054] Figure 2 This is a schematic diagram of the internal structure of the differential pressure sensor of the present invention;

[0055] Figure 3 This is a schematic diagram of the structure of the connector of the present invention;

[0056] Figure 4 This is a schematic diagram of the differential pressure sensor of the present invention;

[0057] Figure 5 Experimental data for this invention Figure 1 This represents the change in vacuum level and capacitance value;

[0058] Figure 6 Experimental data for this invention Figure 2 This indicates the change in capacitance value due to altitude;

[0059] Figure 7 Experimental data for this invention Figure 3 This indicates the change in capacitance over time as the vacuum level decreases at room temperature.

[0060] Figure 8 Experimental data for this invention Figure 4 This indicates that the vacuum level decreases at 60℃, and the capacitance value changes over time.

[0061] Figure 9 Experimental data for this invention Figure 5 This indicates that the vacuum level decreases at 80℃, and the capacitance value changes over time.

[0062] Figure 10 Experimental data for this invention Figure 6 , Figure 7-9 A comparison diagram.

[0063] Labeling explanation: 10, Chipset; 20, Connector; 21, First Ring; 22, Second Ring; 23, Ring Channel. Detailed Implementation

[0064] The technical solution of the present invention will be further described below with reference to the embodiments. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0065] For a fabrication process of a differential pressure sensor, please refer to [link / reference]. Figure 1-4 The differential pressure sensor includes a housing with a cavity and a chip assembly and connector located inside the housing. The connector includes a first annular ring disposed on the outer side and a second annular ring disposed on the inner side, forming an annular channel between the first and second annular rings. The horizontal cross-sectional area of ​​the annular channel 23 gradually increases along the direction away from the chip. The manufacturing process includes injecting epoxy resin into the annular channel 23 to separate the internal and external air pressure of the chip assembly.

[0066] The chipset includes a second glass sheet and a chip, with a specific structure similar to existing structures (e.g., the structure in a differential pressure contact MEMS capacitor film vacuum gauge, Chinese invention patent announcement number CN111982383A), which will not be described in detail. This invention mainly improves sealing performance by forming a double seal through the chipset fabrication process and the encapsulation of the annular channel 23. Furthermore, the fabrication process in this embodiment also includes a chipset fabrication process, which includes the following steps:

[0067] Step S01, cleaning of silicon oxide wafer and first glass plate. Specifically, first boil in solution No. 3 for 20-40 minutes and blow dry, then put into vacuum oven for 30-60 minutes. Solution No. 3 is hydrogen peroxide and concentrated sulfuric acid, and the ratio of the two is 1:3.

[0068] Step S02, photolithographic development of the silicon oxide wafer and the first glass plate, the photolithographic development adopts the following steps:

[0069] Step S21, coating: Apply tackifier and photoresist in sequence, coat with a spin coater and dry. Specifically, the coating sequence is: tackifier, spin coater 50r 3s, 2500r 60s, 5214-E photoresist, spin coater 50r 3s, 2500r 60s, heating plate 96℃ 4min.

[0070] Step S22, photolithography: expose the silicon oxide wafer and the first glass plate using a photolithography machine and a film plate. Specifically: use 5214-E photoresist, a spin coating speed of 2500 r / min, a mercury lamp intensity of 9-11, and an exposure time of 20-30 s.

[0071] Step S23, Development: The exposed sample is placed in the developing solution for development to make the pattern appear, and the development time is 60-80 seconds.

[0072] Step S03, magnetron sputtering is performed on the first glass sheet, wherein the magnetron sputtering includes the following steps:

[0073] Step S31, Sputtering: Sputter a chromium + aluminum metal layer on the surface by magnetron sputtering;

[0074] Step S32, stripping: Immerse the sputtered sample in a 5%-10% acetone solution and let it stand for 8-24 hours. Use a clean cotton swab to strip off the excess metal layer outside the structure.

[0075] Step S04: Plasma etching is performed on the silicon oxide wafer using a dry etching process. The plasma etching process includes the following steps:

[0076] Step S41, Coating: Coating the back of the silicon oxide wafer with adhesive and baking at high temperature for 15-30 minutes to create a protective layer; This step is for protection, and the photoresist, spin coating parameters, etc. can be the same as above. After baking at a low temperature of 96℃ for 4 minutes, it can be transferred to a high temperature of 135℃ and baked for another 15-30 minutes.

[0077] Step S42, remove oxide layer: wash with hydrofluoric acid solution to remove the silicon dioxide layer of the exposed surface and the patterned structure area. The area outside the pattern is protected by photoresist and is not affected.

[0078] Step S43, Etching: Plasma etching for 4 micrometers;

[0079] Step S44, Photoresist removal: Wash with acetone to remove residual plasma chemicals and photoresist, clean with alcohol, and then clean the silicon oxide wafer with solution No. 3, which is hydrogen peroxide and concentrated sulfuric acid in a ratio of 1:3.

[0080] Step S05 involves performing back-side photolithography on the silicon oxide wafer from step S04 and removing the oxide layer. Specifically, the silicon oxide wafer etched using plasma etching includes:

[0081] Step S51: After washing the silicon oxide wafer with solution No. 3, place it in an oven and bake at high temperature for 30 minutes to prepare for photolithography; if the silicon oxide wafer is left for a long time, it needs to be washed with solution No. 3 again.

[0082] Step S52, apply adhesive (see step S21 for specific steps, the same below);

[0083] Step S53, photolithography: perform a second exposure on the back side of the silicon oxide wafer;

[0084] Step S54, development.

[0085] The oxide layer is removed using a hydrofluoric acid solution from the oxide layer of the current photolithographic structure (which is protected by photoresist), as well as all the oxide layer on the first photolithographic surface (the patterned area from the first photolithography has already been removed); then cleaning is performed; and the cleaning is performed using the following method:

[0086] Step S55, Cleaning with Solution No. 3: Place hydrogen peroxide and concentrated sulfuric acid in a container with a ratio of 1:3 (e.g., 220ml: 660ml, depending on the container). Place the container on a heating plate and heat to 230-250℃ and boil for 20-40 minutes (depending on the bubbles in the solution reaction). Then rinse with deionized water 6-8 times using a rinsing cup.

[0087] Step S56, wash with BOE (hydrofluoric acid) solution: soak for 5 minutes and then rinse with deionized water once. Repeat the operation 3-5 times until the photolithographic pattern area shows signs of dehydration.

[0088] Step S57, washing with acetone and alcohol: Immerse the sample in acetone and stir it with tweezers for 2-5 minutes, then replace with fresh acetone and repeat the operation. Then rinse with alcohol and deionized water, and finally dry with a nitrogen gun.

[0089] Step S06, anodic bonding: The metal surface of the first glass plate and the etched surface of the silicon oxide plate are placed in a chip bonding machine for bonding to form a primary electrostatic bonding seal;

[0090] Step S07, Second glass slide scribing: Use a scribing machine to scribing the glass. Taking the first glass slide of 9.2mm*9.2mm as an example, place the sample on the worktable of the scribing machine, turn on vacuum adsorption, load the glass scribing cutter, and then set the parameters on the scribing machine operation panel: spindle speed 15000r / min, step (final size of the device) 9.2*10.7mm, workpiece thickness: 1mm (anodic bonding sheet), allowance thickness: 0.15mm, feed rate: 3mm / s;

[0091] A second glass sheet will also be needed for later drilling and bonding. The parameters are as follows: step size 9.2*9.2mm, workpiece thickness 0.5mm, and other parameters are the same as above.

[0092] Manually align the cutting position with the panel display (this position is pre-designed by the photomask) and calculate the number of cuts (the number of dicing cuts is manually calculated based on the pre-designed pattern of the photomask).

[0093] Step S08, laser drilling: Use laser drilling to drill a hole in the center of the second glass sheet. The hole diameter is 2mm. This is to protect the inner film from being adhered during glue injection. Specifically, laser drilling is performed on the 9.2*9.2mm second glass sheet. The hole is located at the geometric center of 9.2*9.2mm ±1mm.

[0094] Furthermore, in step S09, the bonding position is located on the annular upper surface of the silicon surface of the anodic bonding (silicon + glass) component and the surface of the 9.2*9.2 second glass sheet, with the planar coordinates being ±1mm from the geometric center of the annular structure.

[0095] The coating sequence is as follows: tackifier, spin coater 50r 3s, 2500r 60s, 5214-E photoresist, spin coater 50r 3s, 2500r 60s, heating plate 96℃ 4min;

[0096] Step S09, Differential pressure chamber bonding: The second glass sheet after drilling is bonded to the chip.

[0097] A differential pressure sensor can be fabricated using the above process, and the results can be obtained through experiments as shown in the attached figure. Figure 5 , 6 7. The change in capacitance of the differential pressure sensor fabricated using the process of this invention under varying vacuum conditions can be found in [reference needed]. Figure 5 ,pass Figure 5 It is known that for every 0.1 Pa change in vacuum level, the capacitance changes by 0.59 fF. Therefore, the differential pressure sensor of this invention achieves a resolution of 0.1 Pa, which is significantly better than 0.5 Pa. Furthermore, the change in capacitance value of the differential pressure sensor obtained by this invention can be found in [reference needed]. Figure 6 ,pass Figure 6 It is known that in the water column pressure simulation test, for every 0.01mm increase in water column height, the capacitance changes by 1.34fF. Therefore, the accuracy of the differential pressure sensor of this invention is 0.01mm. Furthermore, the differential pressure sensor manufactured by the process of this invention is less affected by temperature. Within a certain time, the vacuum decreases under different temperatures, but the curves of change are consistent over time at different temperatures. Therefore, the trend of capacitance change is roughly the same. For details, please refer to [reference needed]. Figure 7-10 In summary, the differential pressure sensor manufactured using the process of this invention has high accuracy.

[0098] The beneficial effects of this invention are as follows:

[0099] First, by fabricating the mold and optimizing the process parameters, a high-performance and high-sensitivity differential pressure sensor can be achieved.

[0100] Second, the absolute isolation between the two cavities of the chip is achieved through the structural design of the packaging.

[0101] Third, epoxy resin is used as a sealing material. The epoxy resin is injected into the U-shaped structure to separate the inner membrane from the external air pressure, forming a secondary seal.

[0102] Fourth, the second annular ring adopts a hollow column, which is tilted at a certain angle to facilitate later installation; the hollow column and the air holes on both sides of the chip are in different pressure environments, forming a differential pressure.

[0103] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A fabrication process for a differential pressure sensor, characterized in that, The differential pressure sensor includes a housing with a cavity and a chip assembly and connector located inside the housing. The connector includes a first annular ring disposed on the outer side and a second annular ring disposed on the inner side. An annular channel is formed between the first annular ring and the second annular ring. The horizontal cross-sectional area of ​​the annular channel gradually increases along the direction away from the chip. The manufacturing process includes injecting epoxy resin into an annular channel to separate the internal and external air pressure of the chipset, and the chipset includes a second glass sheet and a chip. The fabrication process also includes a chipset fabrication process, which includes the following steps: Step S01: Cleaning of the silicon oxide wafer and the first glass sheet; Step S02: Photolithographic development of silicon oxide wafer and first glass plate; Step S03: Perform magnetron sputtering on the first glass sheet; Step S04: Perform plasma etching on the silicon oxide wafer; Step S05: Perform back-side photolithography on the silicon oxide wafer from step S04 and remove the oxide layer; Step S06, anodic bonding: The metal surface of the first glass plate and the etched surface of the silicon oxide plate are placed in a chip bonding machine for bonding to form a primary electrostatic bonding seal; Step S07, Second glass slide scribing: Scribing the glass slide using a scribing machine; Step S08, laser drilling: Use laser drilling to drill a hole in the center of the second glass plate, with a hole diameter of 2mm; Step S09, Differential pressure chamber bonding: The second glass sheet after drilling is bonded to the chip.

2. The fabrication process of a differential pressure sensor according to claim 1, characterized in that, In step S01, the sample is first boiled in solution No. 3 for 20-40 minutes and then dried. Then it is placed in a vacuum oven and dried for 30-60 minutes. Solution No. 3 is hydrogen peroxide and concentrated sulfuric acid in a ratio of 1:

3.

3. The fabrication process of a differential pressure sensor according to claim 1, characterized in that, The photolithography development in step S02 adopts the following steps: Step S21, coating: Apply tackifier and photoresist in sequence, coat with a spin coater and then dry. Step S22, photolithography: The silicon oxide wafer and the first glass plate are exposed using a photolithography machine and a film plate; Step S23, Development: The exposed sample is placed in the developing solution for development, so that the pattern can be revealed.

4. The fabrication process of a differential pressure sensor according to claim 1, characterized in that, In step S03, magnetron sputtering includes the following steps: Step S31, Sputtering: Sputter a chromium + aluminum metal layer on the surface by magnetron sputtering; Step S32, stripping: Immerse the sputtered sample in a 5%-10% acetone solution and let it stand for 8-24 hours. Use a clean cotton swab to strip off the excess metal layer outside the structure.

5. The fabrication process of a differential pressure sensor according to claim 1, characterized in that, In step S04, plasma etching includes the following steps: Step S41, applying adhesive: Apply adhesive to the back of the silicon oxide wafer and bake at high temperature for 30 minutes to create a protective layer; Step S42, remove oxide layer: wash with hydrofluoric acid solution to remove the silicon dioxide layer of the exposed surface and the patterned structure area. The area outside the pattern is protected by photoresist and is not affected. Step S43, Etching: Plasma etching for 4 micrometers; Step S44, Photoresist removal: Acetone is used to remove residual plasma chemicals and photoresist, followed by alcohol cleaning, and then the silicon oxide wafer is cleaned with solution No. 3, which consists of hydrogen peroxide and concentrated sulfuric acid in a ratio of 1:

3.

6. The fabrication process of a differential pressure sensor according to claim 1, characterized in that, In step S05, a silicon oxide wafer is etched using plasma etching. Specifically, Step S51: After washing the silicon oxide wafer with solution No. 3, place it in an oven and bake at high temperature for 30 minutes to prepare for photolithography. If the silicon oxide wafer is left for a long time, it needs to be washed with solution No. 3 again. Solution No. 3 is made of hydrogen peroxide and concentrated sulfuric acid, and the ratio of the two is 1:

3. Step S52, apply adhesive; Step S53, Photolithography: Perform a second exposure on the back side of the silicon oxide wafer. Step S54, development.

7. The fabrication process of a differential pressure sensor according to claim 1, characterized in that, In step S05, the oxide layer is removed by using hydrofluoric acid solution to remove the oxide layer of the current photolithographic structure and all the oxide layer of the first photolithographic surface; then it is cleaned.

8. The fabrication process of a differential pressure sensor according to claim 7, characterized in that, The cleaning process includes the following steps: Step S55, Cleaning with solution No. 3: Place hydrogen peroxide and concentrated sulfuric acid in a container with a ratio of 1:3, place the container on a heating plate and heat to 230-250℃ and boil for 20-40 minutes, then rinse with deionized water 6-8 times with a rinsing cup. Step S56, Wash BOE solution: Soak for 5 minutes and then rinse with deionized water once. Repeat this process 3-5 times until the photolithographic pattern area shows signs of dehydration. Step S57, washing with acetone and alcohol: Immerse the sample in acetone and stir it with tweezers for 2-5 minutes, then replace with fresh acetone and repeat the operation. Then rinse with alcohol and deionized water, and finally dry with a nitrogen gun.

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