Investigation of Wafer Surfaces with Space-Resolved Breaking Strength Tests and Corresponding Analysis of the Crack Depth

Abstract

Due to the multi-wire slurry sawing process, crystalline silicon wafers show a critical damage behavior in form of a limited breaking strength. To enhance the yield of the crystalline solar cell production, it is necessary to minimize the breaking ratio of silicon wafers and solar cells. The breaking strength is determined both by the surface quality at the edges (especially determined by microcracks and chippings) and by the surface quality of the front and back sides of the wafer (especially determined by steps, grooves and microcracks). In our contribution we investigated the subsurface and edge damages of selected multicrystalline silicon wafers and developed a special fracture bending test for investigating critical wafer areas. This allows a correlation between space-resolved breaking strength values and corresponding surface roughness and crack depths.