Method and equipment for removing B / PSG layer in photovoltaic cell preparation

Abstract

The invention relates to the technical field of photovoltaic cell manufacturing, and particularly discloses a photovoltaic cell preparation method and device based on hot water film protection and heating. The method is characterized in that deionized water used for forming the protective water film in the chained B / PSG removal equipment is heated to a preset temperature (30-80 DEG C), so that the hot water protective film is formed on the first surface of the silicon wafer. According to the hot water film, the uniformity and the stability of a protection surface are enhanced by utilizing the excellent wettability, and the heat energy of the hot water film is conducted to the second surface through the silicon wafer substrate to indirectly preheat an area to be in contact with hydrofluoric acid corrosive liquid, so that the etching chemical reaction rate is remarkably accelerated. The corresponding equipment is improved in that a heating temperature control unit is additionally arranged on a water supply pipeline of the water film supply mechanism and comprises a heating device, a temperature sensor and a temperature controller. By means of simple and low-cost transformation, the double purposes of reaction acceleration and protection enhancement are achieved at the same time, the production efficiency and the product yield are effectively improved, and acid liquor consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell manufacturing technology, and specifically discloses a method and equipment for removing the B / PSG layer in photovoltaic cell preparation. Background Technology

[0002] With the continuous development of the photovoltaic industry, cost reduction and efficiency improvement have become the core pursuit of the industry. In the manufacturing process of photovoltaic cells, removing the borosilicate glass (BSG) or phosphosilicate glass (PSG) layer (collectively referred to as the B / PSG layer) formed after diffusion or phosphorus diffusion / annealing is a key process. At present, the industry generally uses a chain etching machine for single-sided etching: the silicon wafer is transported by rollers, so that one side is coated with deionized water to form a protective water film to prevent hydrofluoric acid (HF) from corroding the side; at the same time, the other side is contacted with HF acid solution by rollers, and the B / PSG layer is etched and removed through chemical reaction to proceed with subsequent process steps.

[0003] However, existing technological solutions are gradually facing bottlenecks due to the increasingly urgent need to increase production capacity. Specifically, if chain conveyors want to increase production capacity based on existing processes, they must increase the conveyor belt speed of silicon wafers. Currently, the industry's belt speed of 4.5 meters per minute is close to its limit. Some equipment manufacturers claim to support 5.0 meters per minute, but in actual production verification, their stability is insufficient and they cannot meet the requirements of large-scale mass production. Therefore, battery manufacturers often have no choice but to increase the number of machines to meet their production capacity targets, which undoubtedly brings huge capital investment and production space costs.

[0004] The root causes of the limitations of existing technologies lie primarily in the following aspects: First, the reaction rate is limited: the chemical reaction rate between HF acid and the B / PSG layer is extremely sensitive to temperature, and the reaction is relatively slow at room temperature (20-25℃). To achieve the desired etching effect within a limited reaction time, it is often necessary to increase the concentration of HF acid or extend the reaction time, which not only increases chemical consumption but also drives up production costs. Second, there are issues with the uniformity and stability of the water film: due to its inherent surface tension, the room-temperature deionized water film used for protection is difficult to form a highly uniform and stable protective layer on the high-speed silicon wafer surface, posing a risk of localized thinning or cracking. This could lead to HF acid mist or splashing corroding the protected surface, resulting in a decrease in product yield. Furthermore, energy consumption is separated from the process: if the reaction is accelerated by directly heating the acid, the entire acid circulation system needs to be heated and kept at a constant temperature. This involves high equipment modification costs, huge energy consumption, and difficulty in ensuring the accuracy and uniformity of temperature control.

[0005] Therefore, there is an urgent need in this field for a new technology that can effectively accelerate etching chemical reactions and reduce the consumption of process chemicals without significantly increasing costs and complexity, while also significantly enhancing the performance and stability of the protective water film. Summary of the Invention

[0006] To address the shortcomings of existing technologies, one objective of this invention is to provide a photovoltaic cell fabrication method based on hot water film protection and heating. This method can significantly accelerate the etching reaction rate, reduce acid consumption, and enhance the uniformity and stability of the protective water film, thereby improving production efficiency and product yield.

[0007] Another objective of this invention is to provide an apparatus for implementing the above-described method, which is simple to modify, low in cost, and has precise temperature control, and can be seamlessly integrated into existing chain production processes.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: On one hand, this invention provides a method for removing the B / PSG layer in photovoltaic cell fabrication, applied to a chain conveyor. The chain conveyor transports silicon wafers via rollers and forms a protective water film on the first surface of the wafer. Hydrofluoric acid etching solution is then applied to the second surface of the wafer to remove the B / PSG layer. The core of this method lies in: The deionized water used to form the protective water film is heated; A hot water protective film is formed on the first side of the silicon wafer using heated deionized water. The heat energy of the hot water protective film is used to preheat the second side of the silicon wafer to accelerate the chemical reaction between the hydrofluoric acid etching solution and the B / PSG layer.

[0009] Preferably, the deionized water is heated to a preset temperature T, wherein T is higher than the ambient temperature and lower than the boiling point of water.

[0010] Preferably, the preset temperature T is in the range of 30°C to 80°C. Within this temperature range, the heat transfer effect is significant, and the evaporation of the water film is under control.

[0011] More preferably, the preset temperature T is in the range of 50°C to 65°C. This temperature range achieves an optimal balance between significantly accelerating the chemical reaction and preventing the water film from evaporating too quickly, resulting in a wide process window and stable performance.

[0012] On the other hand, the present invention provides an apparatus for implementing the above method, including a water film supply mechanism, wherein a heating and temperature control unit is connected in series on the water supply pipeline of the water film supply mechanism; the water inlet of the heating and temperature control unit is connected to a deionized water source through a pipeline, and its water outlet is connected to a water nozzle for coating a water film onto the surface of a silicon wafer through a pipeline.

[0013] The heating and temperature control unit includes: a heating device with an internal flow channel for heating deionized water; a temperature sensor installed at the outlet of the heating device or on the outlet pipe for detecting the temperature of the outflowing water; and a temperature controller connected to the heating device and the temperature sensor for controlling the heating power of the heating device based on the detection signal from the temperature sensor, so that the water temperature is stabilized at a preset value.

[0014] Preferably, the heating device is an instantaneous tubular heater or a plate heater, and its exterior is wrapped with a high-temperature resistant and corrosion-resistant material to adapt to the deionized water environment and ensure long-term stable operation.

[0015] Preferably, the water film supply mechanism further includes an insulated water storage tank, which is connected in series on the pipeline between the heating and temperature control unit and the water outlet nozzle; the outer wall of the insulated water storage tank and / or the water pipes connecting the components is covered with an insulation layer to reduce heat loss during short-term storage and transportation, improve energy efficiency and ensure process stability.

[0016] As an alternative implementation, the deionized water source of the water film supply mechanism is an external pipeline that supplies preheated deionized water. This external pipeline is connected to the water inlet of the heating and temperature control unit, which is used to reheat the preheated deionized water to the preset value, thereby realizing the cascade utilization of energy.

[0017] Compared with the prior art, the beneficial technical effects of this invention are reflected in: Significantly improved reaction efficiency and reduced acid consumption: By indirectly heating the reverse side of the silicon wafer, the local temperature at the contact point between the HF acid solution and the silicon wafer is effectively increased, resulting in a substantial increase in the chemical reaction rate of the HF acid solution. While achieving the same etching effect, the concentration of the HF solution used can be effectively reduced or the reaction time shortened, thereby significantly reducing chemical consumption and lowering production costs. Simultaneously, this method makes it possible for chain conveyors to overcome existing belt speed bottlenecks (such as stable operation above 5.0 m / min) without altering the core structure, directly increasing the production capacity per unit time.

[0018] Enhanced protection and improved yield: Heating the deionized water reduces its surface tension and enhances its wetting properties, enabling the formation of a more uniform, stable, and strongly adherent protective water film on the high-speed silicon wafer surface. This significantly reduces the risk of front-side corrosion due to localized thinning or rupture of the water film, improving product consistency and final yield.

[0019] The equipment modification is simple and cost-effective: Compared to heating solutions that require modification of the entire corrosive acid circuit system, this invention only improves the piping of the protective water system and adds a compact heating and temperature control unit. This solution is technically mature, has extremely low modification costs, requires no large-scale alterations to existing equipment, and its subsequent maintenance costs and operating energy consumption are far lower than the former, making it easy to promote and apply in industry.

[0020] Synergistic effect: By using the heating and protection water film technology, this invention solves two long-standing technical problems: "slow etching reaction rate" and "poor performance of the protective water film". This results in a synergistic effect of "1+1>2" and has great industrial application value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the principle of a protective hot water film forming on the surface of a silicon wafer in an embodiment of the present invention. Figure 2 This is a schematic diagram of the system configuration of a heating and temperature control unit for generating and supplying hot water in an embodiment of the present invention.

[0022] Figure reference numerals: 1-Silicon wafer, 2-Transfer roller, 3-Hot water inlet, 4-Water film volume regulating valve, 5-Water outlet nozzle, conveying direction is indicated by an arrow; 7-Ambient temperature deionized water inlet, 8-Heating plate, 9-Level sensor, 10-Temperature sensor, 11-Solenoid valve, 12-Insulated water pipe, 13-Insulated water storage tank, 14-Hot water outlet. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] refer to Figure 1 and Figure 2The B / PSG layer removal device in photovoltaic cell fabrication provided by this invention is an improvement on the existing chain-type device. The device body includes a device frame, a roller conveying system, and a water film supply mechanism. Its core improvement lies in the fact that the water film supply mechanism includes a heating and temperature control unit for heating and temperature control of the deionized water supplied to the water film supply mechanism.

[0028] like Figure 2 As shown, the working process of the heating and temperature control unit is as follows: Room temperature deionized water is supplied by an external system and first flows into a heating device. In this embodiment, the heating device is specifically a heating plate 8, which is wrapped in a high-temperature resistant and corrosion-resistant material to ensure long-term stable operation. The water is initially heated after flowing through the heating plate. The heating device is not limited to a plate heater; other equivalent heating elements such as an instantaneous tubular heater can also be used.

[0029] Coordinated control of liquid level and temperature is crucial for the stable operation of this system. Two liquid level sensors 9 are installed on the heating plate 8, serving as a high-level sensor and a low-level sensor, respectively. These two sensors work together to comprehensively judge the high and low liquid level signals, ensuring that the liquid level in the heating plate 8 is always maintained at a suitable operating level, thereby guaranteeing heating efficiency and preventing dry burning.

[0030] When the liquid level is appropriate, the temperature sensor 10, located near the outlet of the heating plate 8 or in the pipeline, begins to monitor the water temperature in real time. This temperature sensor 10 is electrically connected to a temperature controller (such as a PID temperature controller, not shown in the figure). The temperature controller receives the feedback signal from the temperature sensor and compares it with a preset temperature value (e.g., 55°C), thereby precisely adjusting the power of the heating plate 8 to form a high-precision closed-loop temperature control system, ensuring the outlet water temperature remains stable within the preset range.

[0031] After being heated and temperature-controlled, the water is fed into an insulated water storage tank 13. This tank is equipped with an independent level sensor to monitor the water level. This level sensor is linked to a solenoid valve 11 on the inlet pipe, forming a closed-loop control of the hot water supply: when the water level is below a set value, the solenoid valve 11 opens to replenish water; when the water level reaches the set height, the solenoid valve 11 closes. This ensures a continuous and stable supply.

[0032] Finally, hot water is stably output from the hot water outlet 14 of the insulated water storage tank 13.

[0033] like Figure 1 As shown, hot water enters the distribution pipeline through hot water inlet 3, and the operator can precisely adjust the flow rate to each outlet point through the water film volume adjustment valve 4. After the flow rate is adjusted, the hot water is finally evenly coated on the surface of the continuously passing silicon wafer 1 through the water outlet nozzle 5.

[0034] The silicon wafer 1 is carried by the conveying roller 2 and moves at high speed in a specified conveying direction. Hot water forms a stable and uniform hot water protective film on the surface of the silicon wafer 1.

[0035] Figure 1 The direction of transport is indicated by an arrow. Silicon wafer 1 moves forward driven by conveyor roller 2, and its front (upper surface) is first coated with the aforementioned hot water protective film. The heat energy of this film is rapidly conducted through the thermally conductive silicon wafer substrate to its back (the side in contact with the acid). When the preheated back side of the silicon wafer reaches and comes into contact with the HF acid region, the chemical reaction occurs immediately at a higher local temperature, with a reaction rate significantly higher than at room temperature. Simultaneously, the hot water film on the front side of the silicon wafer, due to its lower surface tension and better wettability, can completely and stably cover the silicon wafer surface, effectively isolating it from the erosion of acid mist or sputtering droplets, providing a protective reliability far exceeding that of a room temperature water film.

[0036] Preferably, the insulated water storage tank 13 and the water pipes connecting each component are all equipped with an insulation layer. This can minimize the loss of heat during short-term storage and transportation, improve energy utilization efficiency, and ensure the stability of the process.

[0037] In another embodiment, waste heat from the factory cooling tower or other processes is recovered and used to preheat deionized water to 30-40°C before it is further heated to a preset temperature of 55°C by the heating and temperature control unit described in this invention. This method further reduces the energy consumption of the system and maximizes energy utilization.

[0038] In another embodiment, the heating and temperature control unit can be composed of a separate water heater. This water heater can directly produce and provide hot water at a stable preset temperature. Hot water from the water heater is directly delivered to the nozzle 5 of the water film supply mechanism through an insulated outlet pipe. This solution highly integrates heating and water storage functions, simplifying on-site installation and control systems.

[0039] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0040] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A method for removing the B / PSG layer in photovoltaic cell fabrication, applied to a chain conveyor, wherein the chain conveyor transports silicon wafers via rollers and forms a protective water film on a first surface of the silicon wafer, and applies a hydrofluoric acid etching solution to the second surface of the silicon wafer to remove the B / PSG layer, characterized in that... The method includes: The deionized water used to form the protective water film is heated; A hot water protective film is formed on the first side of the silicon wafer using heated deionized water. The heat energy of the hot water protective film is used to preheat the second side of the silicon wafer to accelerate the chemical reaction between the hydrofluoric acid etching solution and the B / PSG layer.

2. The method according to claim 1, characterized in that, The deionized water is heated to a preset temperature T, where T is higher than the ambient temperature and lower than the boiling point of water.

3. The method according to claim 2, characterized in that, The preset temperature T ranges from 30°C to 80°C.

4. The method according to claim 3, characterized in that, The preset temperature T ranges from 50°C to 65°C.

5. A chain-type B / PSG removal device for implementing the method as described in any one of claims 1 to 4, comprising a water film supply mechanism, characterized in that, A heating and temperature control unit is connected in series on the water supply pipeline of the water film supply mechanism; The water inlet of the heating and temperature control unit is connected to a deionized water source via a pipe, and its water outlet is connected to a water nozzle used to coat a water film onto the silicon wafer surface via a pipe.

6. The device according to claim 5, characterized in that, The heating and temperature control unit includes: The heating device has an internal flow channel for heating deionized water; A temperature sensor is installed at the water outlet or on the water outlet pipe of the heating device to detect the temperature of the water flowing out. A temperature controller, connected to the heating device and the temperature sensor, is used to control the heating power of the heating device according to the detection signal of the temperature sensor, so that the water temperature is stabilized at a preset value.

7. The device according to claim 6, characterized in that, The heating device is an instantaneous tubular heater or a plate heater.

8. The device according to claim 5, characterized in that, The water film supply mechanism also includes an insulated water tank, which is connected in series on the pipeline between the heating and temperature control unit and the water outlet nozzle; the outer wall of the insulated water tank and / or the water pipes connecting the components is covered with an insulation layer.

9. The device according to claim 5, characterized in that, The deionized water source of the water film supply mechanism is an external pipeline that supplies preheated deionized water, and this external pipeline is connected to the water inlet of the heating and temperature control unit.

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