Effect of Silicon Wafer Surface Stains on Copper-Assisted Chemical Etching

Abstract

Silicon wafer slicing is a crucial process during solar cell fabrication, but it often stains the silicon wafer surface. Thus, this work systematically investigated the composition, source, and cleaning method of typical white spot stains on silicon wafer surfaces. The EDS and XPS results showed that the white spot stains contained CaCO3 and SiO2 that were consistent with the filler components in sticky silicon ingot glue. The effects of stains on copper deposition and copper-assisted chemical etching were studied. White spot stains remained attached to the silicon surface after deposition and etching. These stains affected the uniform deposition of copper particles on the surface of the silicon wafer and also impeded the catalytic etching of copper particles. Finally, KOH solution was combined with an ultrasonic field to remove surface stains from the silicon wafer. This study provides important guidance for the removal of silicon wafer contaminants to fabricate high-efficiency solar cells.