Effect of grit shape and crystal structure on damage in diamond wire scribing of silicon

Fundamental understanding of the fixed abrasive slicing of photovoltaic silicon wafers is crucial for producing low-cost wafers with superior surface quality and mechanical strength. With the goal of understanding the diamond wire sawing process, this paper investigates the scribing of mono- and multi-crystalline silicon by the abrasive grits on an actual diamond wire. Specifically, the effects of grit shape and silicon crystal structure on the resulting surface morphology, subsurface damage, and the critical depth of cut at which ductile-to-brittle transition occurs are investigated. Results show that surface cracking depends on the grit shape. Scribing across the grain and twin boundaries in multi-crystalline silicon impacts the resulting surface morphology, with grit shape producing a greater effect than crystallographic orientation in the grain interior relative to the grain boundary. Subsurface damage depends on the grit shape and crystal structure. Differences in the critical depth of cut for ductile-to-brittle transition in scribing of mono-crystalline silicon are explained via analysis of the stress state produced by idealized grit shapes.