Single side polish etching for the rear side of crystalline silicon wafers

Standard silicon solar cells have a textured front and rear side. In order to optimize the light trapping within the cell and the conditions for a good rear side passivation with local contacts, a planar rear surface is most suitable. The different structured front and rear surfaces of the wafer make the implementation of a single side etching process step essential. The main focus in this study is etching a planar rear surface with industrial standard applications based on a textured surface. With isotropic etch behaviour and high etch rates, which are preferred for inline processes, acidic measures are used to flatten the rear surface of the wafer. Mono- and multicrystalline wafers have been etched by obtaining a weighted reflection of about 35%. A successful single side polish etching after texturization requires a high silicon removal (10 to 30 µm). This process was already successfully transferred to an industrially deployable highly efficient cell design.