P-type IBC battery preparation method based on laser oxidation

Abstract

The invention discloses a P-type IBC cell preparation method based on laser oxidation, and relates to the technical field of solar cells. According to the method, laser is directly used for processing the N region, the 1-4nm oxide layer is grown at the N region to serve as a mask to prevent alkali liquor corrosion, the unprocessed region is etched by alkali liquor, and the silicon substrate is exposed to serve as the P region to form the interdigitated structure. According to the method, one procedure is omitted, so that the equipment and personnel investment and the process fragment rate are reduced, the process time is shortened, the factory yield is increased, energy used by laser in the laser oxidation process is very low, generated heat residues are far lower than the ablation effect, and a large number of ablation fragments cannot be sprayed out in the oxidation process; and the problems of residual heat and ablative chippings are perfectly solved. Meanwhile, redevelopment is carried out on a P-type battery piece, the efficiency of a traditional P-type PRCE battery is broken through, the service life of a P-type silicon wafer industry chain is prolonged, early-stage equipment investment is shared, and energy conservation and environmental protection are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a method for preparing a P-type IBC cell based on laser oxidation. Background Art

[0002] The traditional preparation method of P-type IBC battery is mainly: double-sided alkaline polishing - back phosphorus diffusion - mask - laser removal of P area mask - wet cleaning to expose P area substrate - front texturing and mask removal - double-sided\single-sided aluminum oxide - double-sided silicon nitride - laser grooving - metallization. Among them, the key process of forming the back pattern of the cross-finger is mask-laser-cleaning, which adds three additional processes compared to the production line P-type perc battery. Each process has a negative impact on the overall yield: mask removal residue problem; laser damage to the substrate problem; leakage problem caused by cleaning, etc.

[0003] Patent No. 202210739851.2 discloses a simple preparation method for a P-type IBC battery. After phosphorus diffusion, a silicon-based inorganic mask is coated, and the mask is locally heated by laser. The heated mask is not corrosion-resistant and is corroded by alkali to form a P area. The area protected by the mask becomes the N area, thereby forming a cross-finger back battery.

[0004] Patent No. 202211063386.1 discloses a P-type IBC battery structure and preparation method, double-sided cleaning and polishing, back-side deposition mask silicon nitride, laser ablation to reserve the back surface field, double-sided cleaning and texturing, high-concentration phosphorus doping in the reserved area as the N region, removal of PSG and mask, thermal oxygen annealing, back-side aluminum oxidation, double-sided silicon nitride, laser film opening, and finally forming an IBC battery structure.

[0005] As the demand for component battery efficiency continues to increase, the original mainstream P-type perc battery faces the risk of being eliminated, and how to upgrade technology has become an urgent problem for major manufacturers. The original perc battery manufacturers first consider the factor of maximum compatibility with the original battery production line in the face of the next stage of technology upgrades, and the HJT solution is first excluded; upgrading to the TOPCON route, compared with the original perc production line, only adds boron expansion equipment, polysilicon and tunnel oxide deposition equipment and RCA, most of the equipment can be used directly with slight modifications, and has become the first choice for most battery component manufacturers; for manufacturers with vertically integrated industries, it is obviously too expensive to abandon P-type batteries and fully transform N-type TOPCON. P-type IBC batteries based on P-type silicon wafers have become the first choice for such companies to upgrade. IBC batteries have no grid lines on the front, and have better light utilization than traditional batteries with grid lines on both the front and back, reducing the shading loss caused by grid lines, thereby improving the power generation efficiency of the battery cell, but the problems of difficult process, high cost and low yield restrict the development of IBC batteries. The present invention is based on a laser oxidation process to prepare a back-side battery with interdigitated fingers, replacing the traditional three-step process route for forming a graphic pattern. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a P-type IBC battery based on laser oxidation to solve the problems existing in the prior art.

[0007] A method for preparing a P-type IBC battery based on laser oxidation, comprising the following preparation steps:

[0008] (1) Double-sided cleaning and alkaline polishing, clean the dirt on the incoming materials and make a polished surface on the back of the battery cell to improve the reflectivity of the back side;

[0009] (2) Back side phosphorus diffusion: the silicon wafer enters the furnace tube in a positive direction for high temperature phosphorus diffusion. The reaction gases are POCl3 and O2. The diffusion temperature is 750-800℃ and the diffusion time is 20-30min to form the battery emitter:

[0010] (3) Laser oxidation, wherein the laser oxidation energy is 10-12W, the grown oxide layer is used as an alkali etching barrier layer, the alkali etching temperature is 78-80°C, and the N region on the back of the battery is laser treated to grow a silicon oxide layer;

[0011] (4) Wet etching, using KOH and additives. The additives are mainly used to control the reaction rate and degas. The unprotected area is etched using alkaline KOH to expose the silicon substrate to form a P area.

[0012] (5) Front texturing, the texturing agent is a 2% by volume KOH aqueous solution, a 0.5%-0.7% by volume texturing additive, the temperature is 80°C, the texturing time is 300s, so that the reflectivity of the anti-reflective velvet surface in the full band of 300-1200nm is between 9% and 15%, and at the same time, the back mask is removed, and the laser treatment area is repaired to increase the optical path and improve the utilization rate of light;

[0013] (6) Double-sided aluminum oxide, using ALD to prepare the aluminum oxide passivation layer, providing field passivation and chemical passivation effects;

[0014] (7) Double-sided silicon nitride, using an enhanced plasma deposition furnace to deposit silicon nitride thin film by PECVD, with a reaction temperature of 400°C-520°C, providing chemical passivation and reducing reflectivity;

[0015] (8) Laser grooving: using laser to groove silicon nitride and aluminum oxide to facilitate contact between the slurry;

[0016] (9) metallization by screen printing to prepare metal electrodes;

[0017] Furthermore, in step (2), the surface concentration after back phosphor diffusion is 2E20-1E21atoms / cm 3 .

[0018] Furthermore, in step (3), laser oxidation is used to prepare a mask to form a back contact finger cross-cell.

[0019] Furthermore, in the step (3), picosecond laser is used to process the N region.

[0020] Furthermore, in step (3), the laser wavelength is 350-1000nm.

[0021] Furthermore, the laser treatment in step (3) causes minimal damage to the cell, with IVoc loss <8%.

[0022] Furthermore, the thickness of the oxide layer after laser treatment in step (3) is 1-4 nm.

[0023] Furthermore, in the step (6), aluminum oxide is grown on both sides with a thickness of 3-5 nm.

[0024] Furthermore, in step (7), the thickness of the front silicon nitride is 65-85 nm, and the thickness of the back silicon nitride is 80-95 nm.

[0025] Furthermore, in step (8), the slotting laser energy is 30W-40W.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0027] The present invention adopts laser oxidation + wet etching to replace the mask-laser removal of P area mask-wet etching in the traditional preparation method. The mask method usually adopts silicon nitride or silicon oxide prepared by PECVD method. The PECVD method requires the use of an enhanced plasma deposition furnace, the reaction temperature is 400℃-520℃, and the deposition mask thickness is 40nm-70nm. This process requires the silicon wafer to rely on the card point to fit the graphite boat, which is easy to cause warping after high temperature in the furnace, increasing the breakage rate.

[0028] The present invention does not require this process, and directly uses a laser to process the N region. A 1-4nm oxide layer is grown at the N region as a mask to block alkali corrosion. The area not protected by laser treatment is etched by alkali, exposing the silicon substrate as the P region, thereby forming a cross-finger structure. This reduces one process step, reduces equipment and personnel investment, reduces process breakage rate, reduces process time, and increases factory output. Compared with laser etching technology, laser oxidation uses very low energy in the oxidation process, so the residual heat generated is much lower than the ablation effect. There will not be a large amount of ablation debris ejected during the oxidation process. Therefore, the problems of residual heat and ablation debris are perfectly solved at the same time. At the same time, the present invention is further developed on P-type battery cells, breaking through the efficiency of traditional P-type PRCE batteries, extending the life of the P-type silicon wafer industry chain, spreading the initial equipment investment, and is beneficial to energy conservation and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 It is the traditional route for preparing IBC batteries;

[0031] Figure 2 This is the route for preparing IBC batteries of the present invention;

[0032] Figure 3 The invention discloses a P-type IBC battery process structure: a P-type substrate 1; a phosphorus emitter 2; an aluminum oxide passivation layer 3; a silicon nitride passivation layer 4; an N-region electrode 5; and a P-region electrode 6. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 work are within the scope of protection of the present invention.

[0034] Embodiment 1;

[0035] (1) Double-sided cleaning and alkaline polishing, clean the dirt on the incoming materials and make a polished surface on the back of the battery cell to improve the reflectivity of the back side;

[0036] (2) Back side phosphorus diffusion: The silicon wafer enters the furnace tube in a positive direction for high temperature phosphorus diffusion. The reaction gases are POCl3 and O2. The diffusion temperature is 750℃, the diffusion time is 20min, and the surface concentration is 2E20-1E21atoms / cm 3， Forming the battery emitter:

[0037] (3) laser oxidation, wherein the laser oxidation energy is 10W, the wavelength is 350nm, a 3nm oxide layer is grown as an alkali etching barrier layer, the alkali etching temperature is 78°C, a picosecond laser is used to treat the N region on the back of the battery to grow a silicon oxide layer, the oxide layer thickness is 1nm, the battery cell is slightly damaged IVoc loss is <8%, and a mask is prepared to form a back contact finger cross battery;

[0038] (4) Wet etching, using KOH and additives. The additives are mainly used to control the reaction rate and degas. The unprotected area is etched using alkaline KOH to expose the silicon substrate to form a P area.

[0039] (5) Front texturing, the texturing agent is a 2% by volume KOH aqueous solution and a 0.5% by volume texturing additive, the temperature is 80°C, the texturing time is 300s, so that the reflectivity of the anti-reflective velvet surface within the full band of 300nm is between 9%, and at the same time, the back mask is removed, and the laser treatment area is repaired to increase the optical path and improve the utilization rate of light;

[0040] (6) Double-sided aluminum oxide, using ALD to prepare an aluminum oxide passivation layer with a thickness of 3nm, providing field passivation and chemical passivation effects;

[0041] (7) Double-sided silicon nitride, using an enhanced plasma deposition furnace to perform PECVD deposition of silicon nitride film, the reaction temperature is 400°C, the thickness of the front silicon nitride is 65nm, and the thickness of the back silicon nitride is 80nm, providing chemical passivation and reducing reflectivity;

[0042] (8) Laser grooving, with an energy of 30 W, using laser to groove silicon nitride and aluminum oxide to facilitate contact between the slurry;

[0043] (9) Metallization is performed by screen printing to prepare metal electrodes.

[0044] Embodiment 2;

[0045] (1) Double-sided cleaning and alkaline polishing, clean the dirt on the incoming materials and make a polished surface on the back of the battery cell to improve the reflectivity of the back side;

[0046] (2) Back side phosphorus diffusion: The silicon wafer enters the furnace tube in a positive direction for high temperature phosphorus diffusion. The reaction gases are POCl3 and O2. The diffusion temperature is 800℃, the diffusion time is 30min, and the surface concentration is 2E20-1E21atoms / cm 3， Forming the battery emitter:

[0047] (3) Laser oxidation, wherein the laser oxidation energy is 12W, the wavelength is 350nm, a 3.5nm oxide layer is grown as an alkali etching barrier layer, the alkali etching temperature is 80°C, a picosecond laser is used to treat the N region on the back of the battery to grow a silicon oxide layer, the oxide layer thickness is 4nm, the battery cell is slightly damaged IVoc loss is <8%, and a mask is prepared to form a back contact finger cross battery;

[0048] (4) Wet etching, using KOH and additives. The additives are mainly used to control the reaction rate and degas. The unprotected area is etched using alkaline KOH to expose the silicon substrate to form a P area.

[0049] (5) Front texturing, the texturing agent is a 2% by volume KOH aqueous solution and a 0.7% by volume texturing additive, the temperature is 80°C, the texturing time is 300s, so that the reflectivity of the anti-reflective velvet surface in the full band of 1200nm is between 15%, and at the same time, the back mask is removed, and the laser treatment area is repaired to increase the optical path and improve the utilization rate of light;

[0050] (6) Double-sided aluminum oxide, using ALD to prepare an aluminum oxide passivation layer with a thickness of 5 nm to provide field passivation and chemical passivation effects;

[0051] (7) Double-sided silicon nitride, using an enhanced plasma deposition furnace to perform PECVD deposition of silicon nitride film, the reaction temperature is 520°C, the front silicon nitride thickness is 85nm, and the back silicon nitride thickness is 95nm, providing chemical passivation and reducing reflectivity;

[0052] (8) Laser grooving, with an energy of 40 W, using laser to groove silicon nitride and aluminum oxide to facilitate contact between the slurry;

[0053] (9) Metallization is performed by screen printing to prepare metal electrodes.

[0054] Comparative Example

[0055] Preparation of traditional P-type PERC cells:

[0056] (1) Double-sided cleaning and texturing, the texturing agent is a 2% by volume KOH aqueous solution and a 0.6% by volume texturing additive, the temperature is 80°C, and the texturing time is 300s;

[0057] (2) Back side phosphorus diffusion, using high temperature phosphorus diffusion, the reaction gases are POCl3 and O2, the diffusion temperature is 775℃, and the diffusion time is 25min:

[0058] (3) cleaning and alkali polishing;

[0059] (4) Thermal oxidation to form a 3.5 nm oxide layer;

[0060] (5) Back side aluminum oxide, using ALD to prepare aluminum oxide passivation layer with a thickness of 4 nm;

[0061] (6) Double-sided silicon nitride: silicon nitride film is deposited by PECVD in an enhanced plasma deposition furnace at a reaction temperature of 460°C, with a front silicon nitride thickness of 75 nm and a back silicon nitride thickness of 87 nm;

[0062] (8) Laser grooving, energy 35W;

[0063] (9) Metallization is performed by screen printing to prepare metal electrodes.

[0064] Table 1

[0065]

[0066]

[0067] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a P-type IBC battery based on laser oxidation, characterized in that: The method comprises the following preparation steps: (1) Double-sided cleaning and alkaline polishing, clean the dirt on the incoming materials and make a polished surface on the back of the battery cell to improve the reflectivity of the back side; (2) Back side phosphorus diffusion: the silicon wafer enters the furnace tube in a positive direction for high temperature phosphorus diffusion. The reaction gases are POCl3 and O2. The diffusion temperature is 750-800℃ and the diffusion time is 20-30min to form the battery emitter: (3) Laser oxidation, where the laser oxidation energy is 10-12W, the oxide layer is grown as an alkali etching barrier layer, the alkali etching temperature is 78-80°C, and the N region on the back of the battery is laser treated to grow a silicon oxide layer; (4) Wet etching, using KOH and additives, using alkaline KOH to etch the unprotected area to expose the silicon substrate to form the P region; (5) Front texturing: the texturing agent is a 2% by volume KOH aqueous solution and a 0.5%-0.7% by volume texturing additive. The temperature is 80°C and the texturing time is 300s. The reflectivity of the anti-reflective velvet surface in the full band of 300-1200nm is between 9% and 15%. At the same time, the back mask is removed and the laser-treated area is repaired to increase the optical path and improve the utilization rate of light. (6) Double-sided aluminum oxide, using ALD to prepare the aluminum oxide passivation layer, providing field passivation and chemical passivation effects; (7) Double-sided silicon nitride, using an enhanced plasma deposition furnace to deposit silicon nitride film by PECVD, with a reaction temperature of 400°C-520°C, providing chemical passivation and reducing reflectivity; (8) Laser grooving: using laser to groove silicon nitride and aluminum oxide to facilitate contact between the slurry; (9) Metallization is performed by screen printing to prepare metal electrodes.

2. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: In step (2), the surface concentration after backside phosphorus diffusion is 2E20-1E21 atoms / cm 3 .

3. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: In the step (3), laser oxidation is used to prepare a mask to form a back contact finger cross-cell.

4. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: In the step (3), picosecond laser is used to process the N region.

5. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: The laser wavelength in step (3) is 350-1000nm.

6. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: The laser treatment in step (3) causes minimal damage to the cell, with IVoc loss of <8%.

7. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: The thickness of the oxide layer after laser treatment in step (3) is 1-4 nm.

8. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: In the step (6), aluminum oxide is grown on both sides with a thickness of 3-5 nm.

9. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: In the step (7), the thickness of the front silicon nitride is 65-85 nm, and the thickness of the back silicon nitride is 80-95 nm.

10. The method for preparing a P-type IBC battery based on laser oxidation according to claim 1, characterized in that: The slotting laser energy in step (8) is 30W-40W.

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