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.