Effect of mechanical surface damage on Silicon wafer strength

Abstract

Solar power generation using polycrystalline silicon wafers has been rapidly growing in recent years. As a result, it is required to understand the strength characteristics of polycrystalline silicon wafers in order to enhance their quality. Scratches and material defects should be taken into consideration when strength characteristics of polycrystalline silicon are evaluated, since it is a brittle material. In this paper, bending strength of polycrystalline silicon wafers for solar cells were measured, and evaluation regarding the cause of different strength values, which depend on manufacturing conditions of the wafer, was conducted based on fracture mechanics. Residual stress measurements using Raman spectroscopic and observation with TEM (Transmission Electron Microscope) were also conducted. The results clarified the existence of numerous cracks on the wafer surface that are assumed to be generated during slicing process. Thus, it was confirmed that wafer strength depends on the level of machining damage in slicing process. We can establish high reliability for PV modules as a result of modifying the slicing conditions to minimize the mechanical surface damage on wafers and increase the wafer strength.