CN115719779A

CN115719779A - TOPCon battery mask method

Info

Publication number: CN115719779A
Application number: CN202211508708.9A
Authority: CN
Inventors: 安艳龙; 王步峰; 王强; 陈斌
Original assignee: Shangyi Rongdeng New Energy Co ltd
Current assignee: Shangyi Rongdeng New Energy Co ltd
Priority date: 2022-11-29
Filing date: 2022-11-29
Publication date: 2023-02-28

Abstract

A TOPCon battery mask method comprises the steps of carrying out laser doping on a silicon wafer by adopting an SE process, forming an oxide layer mask in an oxidation furnace, spraying boric acid solution with the mass concentration of 0.01% -1% on a laser doping surface of the silicon wafer, introducing oxygen into the oxidation furnace at high temperature after the boric acid solution on the surface of the silicon wafer is dried, enabling the oxygen to pass through a water bath in a low-temperature pure water bottle before entering the oxidation furnace, enabling oxygen carrying water vapor to enter the oxidation furnace, forming a silicon dioxide layer on the surface of the silicon wafer under the reaction action, forming the oxide layer mask in a laser doping area, and greatly increasing the growth speed of mask silicon dioxide by spraying the boric acid and the oxygen carrying water vapor to enter the oxidation furnace.

Description

TOPCon battery mask method

Technical Field

The invention belongs to the technical field of solar cells, and particularly relates to a masking method for alkali polishing of an N-type crystal TOPCon cell.

Background

At present, the N-type TOPCon battery becomes an important battery technology in the field of photovoltaic batteries, and the technology has the advantages of high conversion efficiency, high double-sided rate, low temperature coefficient, low attenuation and low cost. The TOPCon battery is an upgraded product based on the PERC battery technology, and has more compatibility on the production line.

The SE process is an important process of the PERC cell, and the grid line part of the crystalline silicon cell is subjected to laser doping through SE laser doping, so that phosphorus atoms in an N + layer formed by diffusion of the PERC cell can be doped into a silicon substrate under laser energy, the contact resistance of the metal grid line part and the silicon wafer can be reduced, and the purpose of improving the efficiency is achieved.

However, in the current N-type TOPCon cell, boron is diffused by diffusion of boron, so that borosilicate glass is formed on the surface of the silicon wafer, and since the diffusion coefficient of B is low, laser doping can be performed only by using high laser energy, but the borosilicate glass on the surface of the silicon wafer is easily damaged by the high laser energy. Because the subsequent process needs to use an alkali polishing process to polish the back, if the borosilicate glass is not protected, the alkali liquor can damage the PN junction of the laser doping area on the front, and the conversion efficiency of the cell is reduced. Therefore, a mask is needed to be formed on the SE laser region to generate silicon dioxide, so as to protect the PN junction of the laser doping region. In the traditional SE post-chain oxidation mask technology suitable for the PERC process, a certain amount of oxygen is introduced to carry out thermal oxidation reaction on a silicon wafer at the high temperature of 800-900 ℃, but the forming temperature of N-type TOPCon battery borosilicate glass is high and needs to reach more than 1000 ℃. Therefore, the growth speed of the mask silicon dioxide which is simply oxidized by introducing oxygen at high temperature is lower, and the process requirement cannot be met, so that the applicable effect of the TOPCon cell SE laser-doped medium-chain oxidation is limited.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides the TOPCon battery mask method, which greatly increases the growth speed of mask silicon dioxide by a process of spraying boric acid and oxygen to carry water vapor into an oxidation furnace.

In order to achieve the purpose, the invention adopts the following technical scheme: a TOPCon battery mask method comprises the steps of carrying out laser doping on a silicon wafer by adopting an SE process, forming an oxide layer mask in an oxidation furnace, spraying a boric acid solution with the mass concentration of 0.01% -1% on the laser doping surface of the silicon wafer, introducing oxygen into the oxidation furnace at high temperature after the boric acid solution on the surface of the silicon wafer is dried, enabling the oxygen to pass through a water bath in a low-temperature pure water bottle before entering the oxidation furnace, enabling the oxygen to carry water vapor to enter the oxidation furnace, forming a silicon dioxide layer on the surface of the silicon wafer under the reaction action, and forming the oxide layer mask in a laser doping area.

Further, the spraying amount of the boric acid solution with the mass concentration of 0.01-1% on the laser doping surface is 10-100ml.

Further, the drying of the boric acid solution is carried out by adopting hot air at 60-90 ℃.

Further, the temperature of the oxygen gas in the oxidation furnace is 700-1100 ℃, the oxygen gas introduction amount is 10-100slm, and the reaction time is 100-500 seconds.

Compared with the prior art, the invention has the beneficial effects that: after the silicon wafer doped with laser is sprayed with boric acid, the boric acid forms B2O3 after being heated and decomposed, the reaction speed of the B2O3 and silicon can be increased under the atmosphere of certain water vapor, so that the growth speed of an SiO2 layer is increased, the generation of a protective mask of a laser region is quickly realized, meanwhile, in the process, the doping concentration of B in an SE laser doping region can be further increased, the doping concentration of a grid line region is favorably reduced, the contact resistance is reduced, the conversion efficiency is improved, and the comprehensive efficiency is improved by more than 0.1%; the scheme has another advantage, secondary B diffusion is carried out in the SE laser doping area in a mask diffusion mode, certain conditions can be provided for improving the square resistance of boron diffusion and reducing the doping concentration, and further optimization of the boron diffusion process is facilitated; meanwhile, in the process of mask diffusion, secondary doping also provides a certain condition for reducing SE laser power, lower laser power can be used, the expected surface doping concentration is also achieved after secondary complementary doping, and the lower laser power is beneficial to reducing the damage of laser to the pyramid top on the surface of the silicon wafer, so that the efficiency is promoted, and the method has great economic value.

Detailed Description

To further illustrate the present invention, the following specific embodiments are enumerated:

the method comprises the following steps: the silicon wafer after SE laser enters a chain type oxidation furnace, and the laser doping surface is arranged above the roller;

step two: spraying 10-100ml of boric acid solution with the mass concentration of 0.01% -1% on the surface;

step three; drying the sprayed silicon wafer by hot air at 60-90 ℃ to dry the boric acid solution on the surface;

step four: introducing 10-100slm oxygen at 700-1100 ℃, passing the oxygen in a pure water bottle at 20 ℃ in a water bath manner before entering equipment, ensuring that a certain amount of water vapor is carried into a furnace tube, and reacting for 100-500 seconds; under the combined action of water vapor and oxygen, the reaction of Si + O2= SiO2 occurs, and a silicon dioxide layer with a certain thickness is produced on the surface of the silicon wafer. Meanwhile, after the boric acid solution is sprayed on the surface, the following reaction occurs: 2H3BO3= B2O3+3H2O,2B2O3+3Si =3SiO2+4B, the generation speed of the oxide layer can be greatly improved by adding boric acid, so that an oxide layer mask is formed in an SE laser doping area, and the alkali polishing process is convenient to realize.

It should be apparent that the above-described embodiment is merely an example of the present invention, and any simple modification of the principle provided by the present invention falls within the protection scope of the present invention.

Claims

1. A TOPCon battery mask method comprises a silicon wafer which is subjected to laser doping by adopting an SE process, and an oxide layer mask is formed in an oxidation furnace, and is characterized in that boric acid solution with the mass concentration of 0.01% -1% is sprayed on the laser doping surface of the silicon wafer, oxygen is introduced into the oxidation furnace at high temperature after the boric acid solution on the surface of the silicon wafer is dried, the oxygen passes through a water bath in a low-temperature pure water bottle before entering the oxidation furnace, so that the oxygen carries water vapor to enter the oxidation furnace, a silicon dioxide layer is formed on the surface of the silicon wafer under the reaction action, and the oxide layer mask is formed in a laser doping area.

2. A TOPCon cell masking method as claimed in claim 1, wherein the spraying amount of the boric acid solution with mass concentration of 0.01% -1% on the laser doping surface is 10-100ml.

3. A TOPCon cell mask method as claimed in claim 1, wherein the drying of the boric acid solution is done with hot air at 60-90 ℃.

4. A TOPCon cell masking method as claimed in claim 1, wherein the temperature in the oxidation furnace is 700-1100 ℃ when oxygen is introduced into the furnace, the oxygen introduction amount is 10-100slm, and the reaction time is 100-500 seconds.