Ultra thin silicon wafer slicing using wire-EDM for solar cell application

Abstract

The ever increasing demand of silicon solar cells in PV industry calls for minimizing the material loses (kerf) during Si wafer slicing. The currently employed abrasive slicing methods are capable of slicing ~350μm thick wafers. Recent research efforts have put forward wire-EDM as a potential method. This work presents an extensive experimentation to understand the parametric effects that give ultra thin wafer while minimizing the kerf-loss and maximizing the slicing rate. Ultra thin wafers of size 130–150μm were fabricated using wire-EDM while controlling the input energy by avoiding wire or wafer breakage. The kerf-loss was reduced by ~50% (121μm) while maintaining a high slicing rate of 1.05mm/min. A typical wafer and associated kerf profiles showed a wider thickness at the entry and exit than the middle of the wafer. An increase in open voltage and a decrease in servo voltage increase the slicing rate in frontal direction and cause a decrease in slicing rate in the lateral direction, consequently decreasing the kerf-loss.