Mechanics prediction of the fracture pattern on scratching wafers of single crystal silicon

The effect of anisotropy on the response and fracture pattern on scratching {1 0 0} and {1 1 1} single crystal silicon wafers in two characteristic directions, i.e. < 1 0 0 > and < 1 1 0 > in a {1 0 0} wafer, and < 1 1 0 > and < 1 1 2 > in a {1 1 1} wafer, respectively, was studied. Predictions of the locations of the onset of fracture, as well as the fracture patterns on the wafer surfaces, were obtained applying a "minimum crack length" criterion assisted by numerical determination of the stress states using the finite element method. It was found that the first crack appears on the {1 1 1} or {1 1 0} cleavage plane. The < 1 1 2 > scratching direction on the {1 1 1} wafer is the weakest among the four directions studied, since it provides the highest resolved tensile stress and the shortest initial defect for crack propagation. The < 1 0 0 > scratching direction in the {1 0 0} wafer appears to be strongest. Experiments validated the approach and also showed a higher reliability in the {1 0 0} < 1 0 0 > and {1 1 1} < 1 1 0 > directions. The methodology used in this manuscript can be applied to the determination of fracture patterns in other single crystal materials, under scratching or other mechanical loading conditions. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.