Self-aligned light-induced electroless plating/electro-plating technology, with its advantages of fine grid lines and fast and efficient process, became an ideal option for the preparation of selective emitter solar cells. However, before these technologies processing, the heavy doping area should be etched by HF solution to remove the surface SiO₂ effectively and the pinholes should not emerge to expose the silicon substrate in the SiNx:H mask. Otherwise, the metal nickel and silver would deposit in the pinholes during the light-induced electroless plating/electro-plating resulting in the over-plating phenomenon. This demanded that the pretreatment solution should have highly selective etching for SiO₂/SiNx:H. This paper analyzed the causes of the over-plating phenomenon in terms of the experiment results and studied the feasibility of selective etching for SiO₂/SiNx:H. According to the mechanism of HF etching SiO₂ and SiNx:H, the over-plating phenomenon of multicrystalline silicon solar cells was improved by adjusting the pH value of the buffer HF solution.

Key words: over-plating, selective etching, light-induced electroless plating/electro-plating, multicrystalline silicon solar cells