Mask removing liquid medicine, low-concentration alkaline aqueous solution and mask removing method

Abstract

The invention discloses a mask removing liquid medicine, a low-concentration alkaline aqueous solution and a mask removing method. The mask removing liquid medicine comprises the following raw materials in percentage by mass: 5%-15% of an alkaline activator, 0.5%-4% of a swelling agent, 0.3%-0.8% of a surfactant, 0.05%-0.3% of a complexing stabilizer and the balance of ultrapure water. In the low-concentration alkaline aqueous solution prepared by adopting the mask removing liquid medicine provided by the invention, the traditional pure solvent or high-concentration solvent is abandoned, and the mask is removed by adopting the low-concentration alkaline aqueous solution, so that the environment can be improved, the safety can be guaranteed, the cost can be greatly reduced, and meanwhile, the quality of cleaning and removing the mask can be guaranteed.

Description

A mask removal solution, a low-concentration alkaline aqueous solution, and a method for mask removal. Technical Field

[0001] This invention relates to the fields of photovoltaic and semiconductor technology, and in particular to a chemical solution for removing a mask in a Polyfinger inkjet path on a silicon wafer, a low-concentration alkaline aqueous solution prepared from the chemical solution, and a method for removing the silicon wafer mask using the low-concentration alkaline aqueous solution. Background Technology

[0002] In recent years, the Polyfinger laser process has been increasingly industrialized in TOPCon photovoltaic cell manufacturing. However, the laser process is complex to control, suffers from yield and production capacity issues, and has expensive equipment. Therefore, the Polyfinger inkjet process is a highly advantageous alternative.

[0003] In the inkjet printing process, the back side of a phosphorus-dilated silicon wafer is patterned and inkjet-printed to obtain a mask layer. After various wet processing steps, the poly layer in the non-mask areas on both sides and the back of the silicon wafer is etched away to reduce parasitic light absorption in the non-electrode areas on the back side, thereby improving the photoelectric conversion efficiency and yield of the solar cell. The silicon wafer then requires post-cleaning, which includes removing the mask layer using an alkaline solution. The mask layer obtained from patterned inkjet printing typically includes materials such as epoxy resin, polyurethane, polyimide, and modified paraffin. Traditional wet removal processes use pure solvents or high-concentration solvent systems, including toluene, xylene, benzyl alcohol, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide. These solvents have safety and environmental drawbacks such as high volatility, high physiological toxicity, and poor biodegradability, and pure or high-concentration solvent systems are also costly.

[0004] Therefore, overcoming the safety hazards, environmental unfriendliness, and high production costs associated with existing methods for removing patterned inkjet mask layers from the back of silicon wafers is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0005] This invention addresses the safety hazards, environmental unfriendliness, and high production costs associated with existing methods for removing patterned inkjet mask layers from the back of silicon wafers. It provides a mask removal solution for removing Polyfinger inkjet paths, a low-concentration alkaline aqueous solution containing this solution, and a method for removing the silicon wafer mask using this alkaline aqueous solution. This solution is suitable for alkaline water-based systems, is safe and environmentally friendly, and provides excellent mask removal results.

[0006] The present invention provides a mask removal solution comprising the following raw materials in weight percentage: 5%~15% alkaline activator, 0.5%~4% swelling agent, 0.3%~0.8% surfactant, 0.05%~0.3% complexing stabilizer, and the balance being ultrapure water.

[0007] Preferably, the alkaline activator is at least two of sodium silicate, sodium metasilicate pentahydrate, borax, sodium metaborate, ethanolamine, triethanolamine, ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine.

[0008] Preferably, the swelling agent is at least one selected from propylene glycol methyl ether, propylene glycol monoethyl ether, dipropylene glycol methyl ether, dipropylene glycol butyl ether, ethylene glycol ethyl ether, and ethylene glycol monobutyl ether.

[0009] Preferably, the surfactant is at least two of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, Tween 20, Tween 80, dodecyltrimethylammonium chloride, sodium lauroyl glutamate, sodium lauroyl sarcosinate, and bis(octyl)dimethylammonium chloride.

[0010] Preferably, the complexing stabilizer is at least one of sodium tripolyphosphate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium triacetate, sodium citrate, sodium tartrate, and sodium malate.

[0011] The low-concentration alkaline aqueous solution containing the aforementioned mask removal solution provided by the present invention comprises the following raw materials by volume percentage: 2%~3.5% of the mask removal solution, 2%~5% of liquid alkali, and the balance being ultrapure water.

[0012] Preferably, the liquid alkali is an aqueous solution of sodium hydroxide or potassium hydroxide, with an effective content of 45%.

[0013] The present invention also provides a method for removing masks using a low-concentration alkaline aqueous solution, comprising the following steps: weighing raw materials according to the raw material ratio of the alkaline solution provided by the present invention, and sequentially adding ultrapure water, liquid alkali, and mask removal solution to the tank; starting the tank solution to circulate and bubble, and stopping the bubbling after the bubbling time is reached, while maintaining tank solution circulation; testing the tank solution temperature, and when the cleaning temperature is reached, inputting the silicon wafer into the tank solution for mask removal cleaning, and performing subsequent processing after the cleaning time is reached.

[0014] Preferably, the bubbling time is 3-5 minutes; the cleaning temperature is 40-60°C; and the cleaning time is 30-60 seconds.

[0015] The alkaline activator in the mask removal solution of this invention can promote the saponification of ester bonds, amide bonds, and anhydride bonds in the mask layer by sodium hydroxide or potassium hydroxide in the alkaline aqueous solution, causing macromolecules to break down and generate water-soluble carboxylates. The swelling agent can penetrate into the gaps between macromolecular chains, increasing the interchain spacing and generating uneven swelling internal stress, making it easier for alkaline substances to undergo saponification. The surfactant can improve the physical transport and removal process of the alkaline solution, enhance the interfacial wetting effect, and emulsify and solubilize the reaction products, extending the service life of the solution. The complexing stabilizer can complex divalent cations in the solution, improving the actual utilization rate of sodium hydroxide or potassium hydroxide.

[0016] The low-concentration alkaline aqueous solution for mask removal provided by this invention abandons the use of traditional pure solvents or high-concentration solvents and instead uses a low-concentration alkaline aqueous solution. This can improve the environment, ensure safety, significantly reduce costs, and at the same time ensure the quality of mask removal. Attached Figure Description

[0017] Figure 1 is a photograph of the silicon wafer before mask removal using the existing process; Figure 2 is a photograph of the silicon wafer after mask removal using the existing process; Figure 3 is a microscope image of the silicon wafer before mask removal using the existing process; Figure 4 is a microscope image of the silicon wafer after mask removal using the existing process; Figure 5 is a photograph of the silicon wafer before mask removal in Embodiment 1 of the present invention; Figure 6 is a photograph of the silicon wafer after mask removal in Embodiment 1 of the present invention; Figure 7 is a microscope image of the silicon wafer before mask removal in Embodiment 1 of the present invention; Figure 8 is a microscope image of the silicon wafer after mask removal in Embodiment 1 of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the invention and do not constitute a limitation thereof.

[0019] This invention provides a mask removal solution comprising the following raw materials in weight percentages: 5%~15% alkaline activator, 0.5%~4% swelling agent, 0.3%~0.8% surfactant, 0.05%~0.3% complexing stabilizer, and the balance being ultrapure water. Specifically: the alkaline activator is at least two of sodium silicate, sodium metasilicate pentahydrate, borax, sodium metaborate, ethanolamine, triethanolamine, ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine. The swelling agent is at least one of propylene glycol methyl ether, propylene glycol monoethyl ether, dipropylene glycol methyl ether, dipropylene glycol butyl ether, ethylene glycol ethyl ether, and ethylene glycol monobutyl ether. The surfactant is at least two of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, Tween 20, Tween 80, dodecyltrimethylammonium chloride, sodium lauroyl glutamate, sodium lauroyl sarcosinate, and bis(octyl)dimethylammonium chloride. The complexing stabilizer is at least one of sodium tripolyphosphate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium triacetate, sodium citrate, sodium tartrate, and sodium malate.

[0020] The low-concentration alkaline aqueous solution containing the aforementioned mask removal solution provided by the present invention comprises the following raw materials by volume percentage: 2%~3.5% of the mask removal solution, 2%~5% of liquid alkali, and the balance being ultrapure water.

[0021] The liquid alkali can be an aqueous solution of sodium hydroxide or potassium hydroxide, with an effective content of 45%.

[0022] The present invention also provides a method for removing masks using a low-concentration alkaline aqueous solution, comprising the following steps: weighing raw materials according to the raw material ratio of the alkaline solution provided by the present invention, and sequentially adding ultrapure water, liquid alkali, and mask removal solution to the tank; turning on the machine to circulate and bubble the tank solution, and turning off the bubbling after reaching the bubbling time of 3-5 minutes, while maintaining tank solution circulation; testing the tank solution temperature, and when the cleaning temperature of 40-60°C is reached, immersing the silicon wafer in the tank solution for mask removal cleaning, and performing subsequent processing after reaching the cleaning time of 30-60 seconds.

[0023] Example 1: According to the raw material ratio of the mask removal solution of the present invention, the amount of each raw material used (mass percentage) is weighed as follows: sodium metasilicate pentahydrate: 6%, triethanolamine: 2.5%, propylenediamine: 0.8%, dipropylene glycol butyl ether: 0.5%, ethylene glycol ethyl ether: 2%, dodecyltrimethylammonium chloride: 0.6%, dioctyldimethylammonium chloride: 0.1%, sodium triacetate: 0.2%, ultrapure water: 87.3%.

[0024] The total percentage of each raw material used is: 6% + 2.5% + 0.8% + 0.5% + 2% + 0.6% + 0.1% + 0.2% = 12.7%, and the amount of ultrapure water used is 87.3%.

[0025] The weighed raw materials are added to the ultrapure water and stirred evenly to obtain the mask removal solution of the present invention.

[0026] According to the raw material ratio of the low-concentration alkaline aqueous solution of the present invention, the following raw material amounts (volume fractions) are weighed: 1.4L mask removal solution, 0.8L potassium hydroxide aqueous solution and 37.8L ultrapure water.

[0027] The effective content of potassium hydroxide in the aqueous solution is 45%. In this Example 1, the volume percentage of liquid alkali is 2.0%, thus obtaining a low-concentration alkaline aqueous solution.

[0028] During production, 37.8L of ultrapure water, 0.8L of potassium hydroxide aqueous solution (45% concentration), and 1.4L of mask removal solution were added sequentially to a 50L mask removal tank. The tank solution was circulated and bubbled for 3 minutes after starting the machine, then the bubbling was turned off, but the tank solution circulation was maintained. The tank solution temperature was tested, and when the temperature reached (52±0.2)℃, the silicon wafer was subjected to mask removal treatment for 45 seconds.

[0029] Example 2: According to the raw material ratio of the mask removal solution of the present invention, the amount of each raw material used (mass percentage) is weighed as follows: sodium metaborate: 4%, diethylenetriamine: 3%, propylene glycol methyl ether: 0.8%, ethylene glycol monobutyl ether: 1.5%, Tween 80: 0.2%, sodium lauroyl glutamate: 0.2%, sodium citrate: 0.1%, disodium ethylenediaminetetraacetate: 0.05%, ultrapure water: 90.15%.

[0030] The total percentage of each raw material used is: 4% + 3% + 0.8% + 1.5% + 0.2% + 0.2% + 0.1% + 0.05% = 9.85%, and the amount of ultrapure water used is 90.15%.

[0031] The weighed raw materials are added to the ultrapure water and stirred evenly to obtain the mask removal solution of the present invention.

[0032] According to the raw material ratio of the low-concentration alkaline aqueous solution of the present invention, the following raw material amounts (volume fractions) were weighed: 1.12 L of mask removal solution, 1.4 L of sodium hydroxide aqueous solution, and 37.48 L of ultrapure water.

[0033] The effective content of sodium hydroxide in the aqueous solution is 45%. In this Example 2, the volume percentage of liquid alkali is 3.5%, thus obtaining the low-concentration alkaline aqueous solution.

[0034] During production, 37.48L of ultrapure water, 1.4L of sodium hydroxide aqueous solution (45%), and 1.12L of mask removal solution were added sequentially to a 50L mask removal tank. The tank solution was started and circulated and bubbled for 5 minutes, after which the bubbling was turned off, but the tank solution circulation was maintained. The tank solution temperature was tested, and when the temperature reached (45±0.2)℃, the silicon wafer was subjected to mask removal treatment for 50 seconds.

[0035] Example 3: Based on the principle and proportion of the mask removal solution according to the present invention, the following raw materials were weighed (mass percentage): ethanolamine: 3%, ethylenediamine: 5%, dipropylene glycol methyl ether: 1.2%, sodium dodecylbenzenesulfonate: 0.4%, sodium lauroyl sarcosinate: 0.1%, sodium tripolyphosphate: 0.15%, sodium tartrate: 0.05%, ultrapure water: 90.1%.

[0036] The sum of the percentages of each raw material is: 3% + 5% + 1.2% + 0.4% + 0.1% + 0.15% + 0.05% = 9.9%, so the amount of ultrapure water used is 90.1%.

[0037] The weighed raw materials are added to the ultrapure water and stirred evenly to obtain the mask removal solution of the present invention.

[0038] According to the raw material ratio of the low-concentration alkaline aqueous solution of the present invention, the following raw material amounts (volume fractions) are weighed: 0.8L mask removal solution, 2.0L potassium hydroxide aqueous solution and 37.2L ultrapure water.

[0039] The effective content of sodium hydroxide in the aqueous solution is 45%. In this Example 3, the volume percentage of liquid alkali is 5.0%, thus obtaining the low-concentration alkaline aqueous solution.

[0040] In industrial production, 37.2L of ultrapure water, 2.0L of sodium hydroxide aqueous solution (45%), and 0.8L of mask removal solution are added sequentially to a 50L mask removal tank. The tank solution is circulated and bubbled for 4 minutes after starting the machine, then the bubbling is turned off, but the tank solution circulation is maintained. The tank solution temperature is tested, and when the temperature reaches (56±0.2)℃, the silicon wafer is subjected to mask removal treatment for 30 seconds.

[0041] The existing process uses a mask removal bath solution with a volume percentage of 80% N-methylpyrrolidone and the remainder being ultrapure water. The bath temperature is 26°C, and the cleaning time is 40 seconds. Microscopic testing of the silicon wafer samples after mask removal shows that, as illustrated in the attached figures, both the existing process (Figures 1-4) and Example 1 of this invention (Figures 5-8) can effectively remove the mask without leaving any residue. The existing process uses a high-concentration solution system, which is costly and environmentally unfriendly. Example 1 of this invention uses a low-concentration alkaline aqueous solution system, abandoning the use of traditional pure solvents or high-concentration solvents, which can improve the environment, ensure safety, significantly reduce costs, and at the same time guarantee the quality of mask removal and cleaning.

[0042] The above description is merely a specific embodiment of the present invention. It should be noted that any modifications, equivalent substitutions, and variations made within the spirit and framework of the present invention should be included within the protection scope of the present invention.

Claims

1. A mask removal solution comprising the following raw materials in weight percentages: 5%~15% alkaline activator, 0.5%~4% swelling agent, 0.3%~0.8% surfactant, 0.05%~0.3% complexing stabilizer, and the balance being ultrapure water.

2. The mask removal solution as described in claim 1, characterized in that, The alkaline activator is at least two of sodium silicate, sodium metasilicate pentahydrate, borax, sodium metaborate, ethanolamine, triethanolamine, ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine.

3. The mask removal solution as described in claim 1, characterized in that, The swelling agent is at least one of propylene glycol methyl ether, propylene glycol monoethyl ether, dipropylene glycol methyl ether, dipropylene glycol butyl ether, ethylene glycol ethyl ether, and ethylene glycol monobutyl ether.

4. The mask removal solution as described in claim 1, characterized in that, The surfactant is at least two of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, Tween 20, Tween 80, dodecyltrimethylammonium chloride, sodium lauroyl glutamate, sodium lauroyl sarcosinate, and bis(octyl)dimethylammonium chloride.

5. The mask removal solution as described in claim 1, characterized in that, The complexing stabilizer is at least one of sodium tripolyphosphate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium triacetate, sodium citrate, sodium tartrate, and sodium malate.

6. A low-concentration alkaline aqueous solution comprising the mask removal solution as described in any one of claims 1 to 5, comprising the following raw materials by volume percentage: 2% to 3.5% of the mask removal solution, 2% to 5% of liquid alkali, and the balance being ultrapure water.

7. The low-concentration alkaline aqueous solution as described in claim 6, characterized in that, The liquid alkali is an aqueous solution of sodium hydroxide or potassium hydroxide, with an effective content of 45%.

8. A method for removing a mask using a low-concentration alkaline aqueous solution as described in claim 6 or 7, comprising the following steps: weighing the raw materials according to the raw material ratio of the alkaline solution provided by the present invention, and sequentially adding ultrapure water, liquid alkali, and mask removal solution to the tank; starting the tank solution to circulate and bubble, stopping the bubbling after the bubbling time is reached, and maintaining tank solution circulation; testing the tank solution temperature, and when the cleaning temperature is reached, inputting the silicon wafer into the tank solution for mask removal cleaning, and performing subsequent processing after the cleaning time is reached.

9. The method for removing a mask as described in claim 8, characterized in that, The bubbling time is 3-5 minutes; the cleaning temperature is 40-60°C; and the cleaning time is 30-60 seconds.

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