Alkali corrosion auxiliary agent for cleaning wound-plated polycrystalline silicon and application of alkali corrosion auxiliary agent

Abstract

The invention discloses an alkali corrosion auxiliary agent for cleaning wound-plated polycrystalline silicon and application of the alkali corrosion auxiliary agent. The alkali corrosion auxiliary agent comprises the following components in percentage by mass: 2-5% of polyether, 1-2.5% of an anionic surfactant, 1-2.5% of a dispersing agent and the balance of deionized water. According to the method, the winding plating polycrystalline silicon is removed by adopting the alkali corrosion liquid with the alkali corrosion auxiliary agent instead of acid corrosion or TMAH, so that the product yield is increased, the chemical cost is reduced, the environmental protection problems such as nitrogen emission do not exist, and no harm is caused to a human body; the alkali corrosion auxiliary agent has selective adsorption and corrosion inhibition effects, and can corrode and remove edge winding plating polycrystalline silicon under the condition of protecting a pyramid structure from being damaged; the process window is wide, the efficiency is stable, the method can be suitable for various devices, groove type machines and chain type machines, and mass production can be conveniently achieved by using an existing machine table on a production line.

Description

technical field [0001] The invention relates to the field of photovoltaics, in particular to an alkali corrosion auxiliary agent for cleaning polycrystalline silicon and its application. Background technique [0002] TOPCon (Tunnel Oxide Passivated Contact) is a high-efficiency crystalline silicon solar cell technology. This technology prepares an ultra-thin (about 1-2nm) tunneling oxide layer on the back of the cell, and then deposits a 20nm-thick phosphorous-doped contact layer. The heterogeneous amorphous silicon layer is formed into doped polysilicon after high-temperature annealing, and the two together form a passivation contact structure. Because the oxide layer is very thin and the silicon thin layer is doped, many carriers can penetrate the two passivation layers, while the minority carriers are blocked. If metal is deposited on it, passivation contacts without openings can be obtained. However, in the manufacturing process of this kind of battery, a layer of polys...

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Problems solved by technology

However, in the manufacturing process of this kind of battery, a layer of polysilicon (polysilicon) is coated on the back of the silicon wafer. In this step, a wrap-around phenomenon will occur, which will cause the front edge of the silicon wafer to be coated with polysilicon, which will affect the appearance and efficiency of the finished product. Degradation, in order to solve this phenomenon, the industry initially used high-end instruments to avoid the problem of coiling and plating. Now some factories have developed and used the following three chemical corrosion methods to solve the problem of coiling and plating:

[0003] 1) Using acid etching, hydrofluoric acid and nitric acid are used to remove the polysilicon on the front side, and the window of this method is narrow, which can easily lead to damage to the front PN junction and a significant drop in product yield; or directly double-sided Plating amorphous silicon, but the solution to the problem of front amorphous silicon affecting the appearance is still to use acid etching. This method still has a narrow window, which is easy to damage the front PN junction and cannot improve product yield, and acid etching also has air pollution. , nitrogen emissions and high chemical costs and other environmental issues;

[0004] 2) Only inorganic alkali potassium hydroxide or sodium hydroxide is used to remove the polysilicon on the front side. This method requires the BSG in the previous process to be thick enough to ensure that part of the BSG is retained when removing the polysilicon on the front side, but this The method window is narrow, the yield rate is not high in mass production, the efficiency and yield rate fluctuate greatly, and when making thick BSG, it will lead to low boron expansion capacity and low battery efficiency;

[0005] 3) Use TMAH (tetramethylhydrogen ammonia) to solve the problem of winding plating, but TMAH is a neurotoxin that has certain damage to the human body and the nitrogen content is too high. The dosage is large, and there is a nitrogen discharge problem.

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