Cleaning method after ion implantation

Abstract

The invention provides a cleaning method after ion implantation. The method comprises the following steps: removing metal impurities possibly remained on the surface of a silicon wafer after ion implantation by using diluted hydrochloric acid; oxidizing the surface powdery residues through hydrogen peroxide; ammonia water simultaneously removing reactants, removing oxides on the surface by using diluted hydrofluoric acid; removing residual organic matters on the surface through hydrogen peroxide; meanwhile, oxidizing residual metal impurities; removing oxidized metal impurities and residual alkali after alkali washing by using hydrochloric acid; removing a generated oxide layer by using diluted hydrofluoric acid; finally, using diluted hydrochloric acid for removing metal ions, so that impurities such as phosphorus, nitrogen, oxygen and carbon remaining on the surface of the silicon wafer after ion implantation can be basically and completely removed. The influence of the remaining impurities on the whole cell structure including the passivation effect, the surface concentration change and the P-N junction quality is further eliminated, and a good cell structure is obtained.

Description

technical field [0001] The invention belongs to the technical field of solar cells, in particular to a cleaning method after ion implantation. Background technique [0002] The current industrialized high-efficiency solar cells are mainly N-type double-sided cells. The front of the cell is doped with B to form a PN junction, and the silver-aluminum paste is used to burn through the aluminum oxide and silicon nitride layers to form a metal contact; the back of the cell is formed by making a layer of N+ The phosphorus diffusion layer reduces the contact resistance and makes the silver paste form a good ohmic contact with the back of the cell. The production of the phosphorus diffusion layer on the back increases the difficulty of the complete cell manufacturing process. The highly doped layer in the N+ layer also means that the Auger recombination in the cell and the interface defects on the silicon surface increase, which reduces the efficiency of the N-type cell. Compared w...

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Problems solved by technology

[0004] Since there will be a layer of impurities on the surface of the battery after ion implantation doping, and the existing cleaning methods after ion implantation cannot completely remove the remaining surface impurities after implantation, resulting in subsequent high-temperature annealing on the surface or even inside of the silicon wafer. Defects are formed, and at the same time, if the residual phosphorus element diffuses to the surface after high temperature, the phenomenon of surface recombination increases, which in turn changes the passivation effect and surface concentration of the battery, thus affecting the passivation effect of the battery and the quality of the entire P-N junction

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