Analysis of the Effects of Wafer Slicing on the Mechanical Integrity of Silicon Wafers (2010-GIT-4)

This paper investigates the effect of crystallographic orientation on the mode of material removal (ductile vs. brittle) in diamond scribing of single crystal silicon (c-Si) and offers an explanation for the observed effects in terms of the combined role of phase transformation and slip generation. Single-point diamond scribing tests are performed on (111), (001) and (110) crystallographic planes in the <111>, <110>, <100> and <112> directions. In all cases, the material removal mechanism transitions from ductile to brittle fracture as the depth of scribing increases. The critical depth of ductile-to-brittle transition is found to vary considerably. Scribing on the (001) Si surface exhibits significant brittle fracture, while ductile removal is achieved on the (111) plane at scribing depths greater than 1μm. In addition, on a given crystallographic plane, brittle fracture is found to always dominate in the <100> direction compared to the <111> direction. These results are explained by the roles of phase transformation and slip generation in the material. For a given scribing depth, orientations for which slip systems are easily activated require higher loading pressures and therefore produce higher tensile stress in the material, which leads to increased brittle fracture. This explanation is found to be consistent with the experimental data presented in this paper and those available in literature.