Preparation method of TBC battery without nitric acid

Abstract

The invention relates to the technical field of TBC battery preparation, in particular to a nitric-acid-free TBC battery preparation method which comprises the following steps: cleaning and polishing an N-type silicon wafer; depositing a first tunneling oxide layer and a first polycrystalline silicon layer doped with a B element on the back surface of the N-type silicon wafer, and generating a mask BSG layer on the surface of the first polycrystalline silicon layer at the same time; locally slotting the mask BSG layer, and cleaning a slotting region to etch the first polycrystalline silicon layer below the slotting region; depositing a second tunneling oxide layer and a second polycrystalline silicon layer doped with P element on the back surface of the cleaned N-type silicon wafer, and generating a mask PSG layer on the surface of the second polycrystalline silicon layer; locally slotting a P region and an adjacent GAP region of the N-type silicon wafer; a mixed solution of HF and H2O2 is used as a polishing solution to polish and etch the N-type silicon wafer, and double-sided texturing is carried out; depositing AlOx layers on the front surface and the back surface of the textured N-type silicon wafer; siNx antireflection films are sequentially deposited on the front face and the back face of the N-type silicon wafer.

Description

Technical Field

[0001] The present invention relates to the technical field of TBC battery preparation, in particular to a method for preparing a TBC battery without requiring nitric acid. Background Art

[0002] The bottleneck of traditional TBC battery manufacturing and its reliance on nitric acid remain key issues in the industrialization of TBC batteries: High nitric acid dependence. Nitric acid (HNO3) is widely used in cleaning and etching processes due to its strong oxidizing properties, such as removing oxide layers from silicon wafers and etching polysilicon layers. However, this produces nitrogen-containing wastewater, increasing environmental treatment costs. Traditional patterned doping requires multiple mask depositions and nitric acid-assisted etching, a lengthy process that can easily damage the passivation layer, impacting battery performance.

[0003] TBC cells require a superimposed TOPCon passivation layer and BC back contact structure, which increases process steps (such as laser grooving and gradient doping of the polysilicon layer). The equipment investment per GW is as high as 400 million yuan, significantly higher than that of mainstream TOPCon production lines. The use of nitric acid further increases material costs (such as silver paste consumption) and waste liquid treatment expenses.

[0004] To address the above issues, the industry urgently needs to achieve environmental protection and cost reduction and efficiency improvement of TBC batteries through nitric acid-free process innovation. As an important branch of N-type technology, the industrialization process of TBC batteries is limited by the environmental protection and cost issues of traditional nitric acid processes. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a TBC battery without the need for nitric acid, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a TBC battery without nitric acid, characterized by comprising the following steps: Step 1: Cleaning and polishing the N-type silicon wafer; Step 2: depositing a first tunneling oxide layer and a first polysilicon layer doped with B element on the back side of the N-type silicon wafer, and forming a mask BSG layer on the surface of the first polysilicon layer; Step 3: partially groove the mask BSG layer, clean the grooved area, and etch the first polysilicon layer below the grooved area; Step 4: depositing a second tunneling oxide layer and a second polysilicon layer doped with P element on the back side of the cleaned N-type silicon wafer, and forming a mask PSG layer on the surface of the second polysilicon layer; Step 5: Partially groove the P region and the adjacent GAP region of the N-type silicon wafer; Step 6: Use a mixture of HF and H2O2 as a polishing solution to polish and etch the N-type silicon wafer, and perform double-sided texturing; Step 7: depositing an AlOx layer on the front and back of the N-type silicon wafer after texturing; Step 8: depositing SiNx anti-reflection films on the front and back of the N-type silicon wafer in sequence; Step 9: Screen printing, sintering or copper electroplating are performed on the front and back sides of the N-type silicon wafer to form metal electrodes, thereby completing the preparation of the TBC battery.

[0007] Preferably, the step 1 specifically includes: Use a 2-5% KOH solution at 70-80°C to clean and polish the N-type silicon wafer, and control the thinning amount between 0.2-0.4g.

[0008] Preferably, the step S2 specifically includes: The cleaned and polished N-type silicon wafer is placed in the LPCVD equipment, and a first tunneling oxide layer and an intrinsic polysilicon layer with a thickness of 1-2nm are deposited on the back. Then, the B element is doped by a high-temperature diffusion method to form a first polysilicon layer with a thickness of 200-210nm. At the same time, a mask BSG layer with a thickness of 50-150nm is generated on the surface of the first polysilicon layer.

[0009] Preferably, the step S3 specifically includes: The mask BSG layer is partially grooved by laser, and the grooved area is treated with a KOH solution with a concentration ratio of 1:0.1-1 and a laser cleaning additive at 65-75° C. for 100-300 seconds.

[0010] Preferably, the concentration of the KOH solution is 2-5%, the concentration of the laser cleaning additive is 0.5%-2%, and the components of the laser cleaning additive include sodium benzoate, lauryl glucoside, sodium diacetate glucose and deionized water.

[0011] Preferably, the step S4 specifically includes: Place the N-type silicon wafer in the PECVD equipment, deposit a second tunneling oxide layer with a thickness of 1-2nm and polysilicon doped with P elements on the back to form a second polysilicon layer with a thickness of 250-270nm. At the same time, form a PSG layer with a thickness of 50-150nm on the surface, and then perform back annealing treatment at 800-950℃ for 20-30min.

[0012] Preferably, the step S6 specifically includes: An N-type silicon wafer is placed in a chain machine, and a mixture of HF and H2O2 with a concentration ratio of 1:5-20 is used as the polishing liquid, the HF concentration is 3-5%, and the H2O2 concentration is 15-60%. Dodecyl glucoside with a concentration of 1%-5% is added to the polishing liquid. The front of the N-type silicon wafer is polished and etched at a temperature of 20-50°C for 1-10 minutes; then the N-type silicon wafer is placed in the texturing machine tank and texturized using alkali. At the same time, the texturizing alkali solution corrodes the second polysilicon layer in the laser groove area to form a PN isolation GAP area; finally, the N-type silicon wafer passes through an acid tank to remove the PSG and BSG layers on the back of the N-type silicon wafer.

[0013] Preferably, the step S7 specifically includes: ALD is used on the front and back sides of the N-type silicon wafer in turn to generate an AlOx film layer with a thickness of 6-12nm on the front and back sides of the N-type silicon wafer.

[0014] Preferably, the step S9 specifically includes: A SiNx anti-reflection film with a thickness of 60-80 nm is deposited on the front and back of the N-type silicon wafer using PECVD.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a TBC battery without the need for nitric acid. The method uses a mixture of HF and H2O2 as a polishing liquid to polish and etch the front side of an N-type silicon wafer, avoiding the use of HNO3 for etching and reducing wastewater treatment costs. Through process reconstruction and innovation, the method promotes TBC technology to move towards high efficiency, low carbon, and low cost, providing key technical support for the sustainable development of the photovoltaic industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention provides a flow chart of a method for preparing a TBC battery without the need for nitric acid. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] Figure 1 The present invention provides a flow chart of a method for preparing a TBC battery without nitric acid. Figure 1 As shown, an embodiment of the present invention provides a method for preparing a TBC battery without nitric acid, comprising the following steps: Step 1: Cleaning and polishing the N-type silicon wafer; Step 2: depositing a first tunneling oxide layer and a first polysilicon layer doped with B element on the back side of the N-type silicon wafer, and forming a mask BSG layer on the surface of the first polysilicon layer; Step 3: partially groove the mask BSG layer, clean the grooved area, and etch the first polysilicon layer below the grooved area; Step 4: depositing a second tunneling oxide layer and a second polysilicon layer doped with P element on the back side of the cleaned N-type silicon wafer, and forming a mask PSG layer on the surface of the second polysilicon layer; Step 5: Partially groove the P region and the adjacent GAP region of the N-type silicon wafer; Step 6: Use a mixture of HF and H2O2 as a polishing solution to polish and etch the N-type silicon wafer, and perform double-sided texturing; Step 7: depositing an AlOx layer on the front and back of the N-type silicon wafer after texturing; Step 8: depositing SiNx anti-reflection films on the front and back of the N-type silicon wafer in sequence; Step 9: Screen printing, sintering or copper electroplating are performed on the front and back sides of the N-type silicon wafer to form metal electrodes, thereby completing the preparation of the TBC battery.

[0019] In one embodiment of the present invention, step 1 specifically includes: A 182.2*182.2mm N-type silicon wafer with a thickness in the range of 110-150 μm was selected; a KOH solution with a concentration of 2-5% was used to clean and polish the N-type silicon wafer at 70-80°C, and the thinning amount was controlled between 0.2-0.4g.

[0020] In one embodiment of the present invention, step S2 specifically includes: The cleaned and polished N-type silicon wafer is placed in the LPCVD equipment, and a first tunneling oxide layer and an intrinsic polysilicon layer with a thickness of 1-2nm are deposited on the back. Then, the B element is doped by a high-temperature diffusion method to form a first polysilicon layer with a thickness of 200-210nm. At the same time, a mask BSG layer with a thickness of 50-150nm is generated on the surface of the first polysilicon layer.

[0021] In one embodiment of the present invention, step S3 specifically includes: The mask BSG layer is partially grooved by laser, and the grooved area is treated with a KOH solution with a concentration ratio of 1:0.1-1 and a laser cleaning additive at 65-75° C. for 100-300 seconds.

[0022] Specifically, in one embodiment of the present invention, the concentration of the KOH solution is 2-5%, and the concentration of the laser cleaning additive is 0.5-2%. The laser cleaning additive comprises sodium benzoate, lauryl glucoside, sodium diacetate glucose, and deionized water. Lauryl glucoside serves as a surfactant, and sodium diacetate serves as a catalyst.

[0023] In one embodiment of the present invention, step S4 specifically includes: Place the N-type silicon wafer in the PECVD equipment, deposit a second tunneling oxide layer with a thickness of 1-2nm and polysilicon doped with P elements on the back to form a second polysilicon layer with a thickness of 250-270nm. At the same time, form a PSG layer with a thickness of 50-150nm on the surface, and then perform back annealing treatment at 800-950℃ for 20-30min.

[0024] In one embodiment of the present invention, step S6 specifically includes: An N-type silicon wafer is placed in a chain machine, and a mixture of HF and H2O2 with a concentration ratio of 1:5-20 is used as the polishing liquid, the HF concentration is 3-5%, and the H2O2 concentration is 15-60%. Dodecyl glucoside with a concentration of 1%-5% is added to the polishing liquid. The front of the N-type silicon wafer is polished and etched at a temperature of 20-50°C for 1-10 minutes; then the N-type silicon wafer is placed in the texturing machine tank and texturized using alkali. At the same time, the texturizing alkali solution corrodes the second polysilicon layer in the laser groove area to form a PN isolation GAP area; finally, the N-type silicon wafer passes through an acid tank to remove the PSG and BSG layers on the back of the N-type silicon wafer.

[0025] A mixture of HF and H2O2 is used as the polishing liquid to polish and etch the front side of N-type silicon wafers, avoiding the use of HNO3 for etching and reducing wastewater treatment costs; dodecyl glucoside is used as a surfactant to adjust the tension of the polishing liquid and does not directly participate in the etching reaction; through process reconstruction and innovation, TBC technology is promoted to move towards high efficiency, low carbon and low cost, providing key technical support for the sustainable development of the photovoltaic industry.

[0026] In one embodiment of the present invention, step S7 specifically includes: ALD is used on the front and back sides of the N-type silicon wafer in turn to generate an AlOx film layer with a thickness of 6-12nm on the front and back sides of the N-type silicon wafer.

[0027] In one embodiment of the present invention, step S9 specifically includes: A SiNx anti-reflection film with a thickness of 60-80 nm is deposited on the front and back of the N-type silicon wafer using PECVD.

[0028] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a TBC battery without nitric acid, characterized in that: The following steps are involved: Step 1: Cleaning and polishing the N-type silicon wafer; Step 2: depositing a first tunneling oxide layer and a first polysilicon layer doped with B element on the back side of the N-type silicon wafer, and forming a mask BSG layer on the surface of the first polysilicon layer; Step 3: partially groove the mask BSG layer, clean the grooved area, and etch the first polysilicon layer below the grooved area; Step 4: depositing a second tunneling oxide layer and a second polysilicon layer doped with P element on the back side of the cleaned N-type silicon wafer, and forming a mask PSG layer on the surface of the second polysilicon layer; Step 5: Partially groove the P region and the adjacent GAP region of the N-type silicon wafer; Step 6: Use a mixture of HF and H2O2 as a polishing solution to polish and etch the N-type silicon wafer, and perform double-sided texturing; Step 7: depositing an AlOx layer on the front and back of the N-type silicon wafer after texturing; Step 8: depositing SiNx anti-reflection films on the front and back of the N-type silicon wafer in sequence; Step 9: Screen printing, sintering or copper electroplating are performed on the front and back sides of the N-type silicon wafer to form metal electrodes, thereby completing the preparation of the TBC battery.

2. The method for preparing a TBC battery without nitric acid according to claim 1, wherein: The step 1 specifically includes: Use a 2-5% KOH solution at 70-80°C to clean and polish the N-type silicon wafer, and control the thinning amount between 0.2-0.4g.

3. The method for preparing a TBC battery without nitric acid according to claim 2, wherein: The step S2 specifically includes: The cleaned and polished N-type silicon wafer is placed in the LPCVD equipment, and a first tunneling oxide layer and an intrinsic polysilicon layer with a thickness of 1-2nm are deposited on the back. Then, the B element is doped by a high-temperature diffusion method to form a first polysilicon layer with a thickness of 200-210nm. At the same time, a mask BSG layer with a thickness of 50-150nm is generated on the surface of the first polysilicon layer.

4. The method for preparing a TBC battery without nitric acid according to claim 3, wherein: The step S3 specifically includes: The mask BSG layer is partially grooved by laser, and the grooved area is treated with a KOH solution with a concentration ratio of 1:0.1-1 and a laser cleaning additive at 65-75° C. for 100-300 seconds.

5. The method for preparing a TBC battery without nitric acid according to claim 4, wherein: The concentration of the KOH solution is 2-5%, the concentration of the laser cleaning additive is 0.5%-2%, and the components of the laser cleaning additive include sodium benzoate, lauryl glucoside, sodium diacetate glucose and deionized water.

6. The method for preparing a TBC battery without nitric acid according to claim 5, wherein: The step S4 specifically includes: Place the N-type silicon wafer in the PECVD equipment, deposit a second tunneling oxide layer with a thickness of 1-2nm and polysilicon doped with P elements on the back to form a second polysilicon layer with a thickness of 250-270nm. At the same time, form a PSG layer with a thickness of 50-150nm on the surface, and then perform back annealing treatment at 800-950℃ for 20-30min.

7. The method for preparing a TBC battery without nitric acid according to claim 6, wherein: The step S6 specifically includes: An N-type silicon wafer is placed in a chain machine, and a mixture of HF and H2O2 with a concentration ratio of 1:5-20 is used as the polishing liquid, the HF concentration is 3-5%, and the H2O2 concentration is 15-60%. Dodecyl glucoside with a concentration of 1%-5% is added to the polishing liquid. The front of the N-type silicon wafer is polished and etched at a temperature of 20-50°C for 1-10 minutes; then the N-type silicon wafer is placed in the texturing machine tank and texturized using alkali. At the same time, the texturizing alkali solution corrodes the second polysilicon layer in the laser groove area to form a PN isolation GAP area; finally, the N-type silicon wafer passes through an acid tank to remove the PSG and BSG layers on the back of the N-type silicon wafer.

8. The method for preparing a TBC battery without nitric acid according to claim 7, wherein: The step S7 specifically includes: ALD is used on the front and back sides of the N-type silicon wafer in turn to generate an AlOx film layer with a thickness of 6-12nm on the front and back sides of the N-type silicon wafer.

9. The method for preparing a TBC battery without nitric acid according to claim 8, wherein: The step S9 specifically includes: A SiNx anti-reflection film with a thickness of 60-80 nm is deposited on the front and back of the N-type silicon wafer using PECVD.

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