Diffusion method used for crystalline silicon solar battery

Abstract

The invention discloses a diffusion method used for a crystalline silicon solar battery. The method comprises the following steps of: (1) placing a silicon wafer into a diffusion furnace; rising the temperature from 780-810 DEG C to 840-860 DEG C; and simultaneously introducing POCL3+O2+N2 for 12 to 14 minutes; (2) simultaneously introducing O2+N2 when rising the temperature in the diffusion furnace to 840-860 DEG C and keeping the constant temperature for 2 to 5 minutes; simultaneously introducing the POCL3+O2+N2 for 8 to 12 minutes when rising the temperature from 840-860 DEG C to 870-890 DEG C; reducing the temperature from 870-890 DEG C to 800 DEG C; introducing the O2+N2 in the process of reducing the temperature; stabilizing for 2 minutes at the temperature of 800 DEG C; and introducing the POCL3+O2+N2; and (3) taking the silicon wafer out of the diffusion furnace. In the method, both the requirements on the doping concentration of an emitting region and the surface concentration of the emitting region in diffusion can be met at the same time; a gettering effect is good; and the distribution of a doping curve is more reasonable.

Description

technical field [0001] The invention relates to a diffusion method, in particular to a diffusion method applied to crystalline silicon solar cells. Background technique [0002] Diffusion technology is the most important process of monocrystalline silicon and polycrystalline silicon solar cells. Its purpose is to form an emitter region with the conductivity type opposite to that of the substrate, thereby forming a PN junction. Usually monocrystalline silicon and polycrystalline silicon solar cells use P-type substrates, phosphorus oxychloride POCL 3 Liquid source diffusion forms a phosphorous-doped N-type emission region through a series of chemical reactions and phosphorus atom diffusion processes. Generally, the diffusion temperature is set at 830-870°C and the source time is 20-35 minutes; during the high temperature process, POCL 3 Nitrogen (generally called this part of nitrogen as small nitrogen) is carried into the quartz tube, and nitrogen (generally called this par...

AI Technical Summary

Problems solved by technology

Increase the resistance of the current moving to the grid wire electrode in the emission area; and because the conduction between the electrode and the emission area depends on the tunneling effect, the contact resistance between the electrode and the emission area is also related to the doping amount. The higher the doping, the higher the contact resistance. Small; if the doping is too low, the contact resistance will increase rapidly, and even ohmic contact cannot be formed

[0004] As mentioned above, the doping concentration of the emitter region must take into account the above two requirements. The currently widely used process is usually selected at one temperature, and the temperature remains unchanged during the diffusion process. Considering the above requirements, a compromise temperature is selected. However, it does not pay enough attention to the gettering process in the diffusion of silicon wafers, and the junction depth curve formed in this way changes as follows: figure 1 As shown, curve 1 is the junction depth curve at the beginning of diffusion, and curve 2 is the final junction depth curve after diffusion. It can be seen from curve 2 that the surface concentration of the emission region will decrease after the diffusion is completed, and the impurity concentration in the body is higher than that on the surface. It affects the contact between the silver grid line and the silicon chip in the later stage, which is not conducive to the collection of electrons, resulting in a high series resistance of the cell, a smaller fill factor, and a lower efficiency

Images