The Effect of the Crystallographic Direction on Crack Generation in Ductile Mode Machining of Single-Crystal Silicon

The crack-free removal of material, known as ductile mode machining, has been achieved by a very small depth of cut. In this study, the nano-scale layers of single-crystal silicon surface are machined by micro-Vickers hardness indenter witch is assumed to be a single abrasive grain. The subsurface crack as well as the surface crack are observed by a scanning prove microscope and a scanning laser microscope. When surface cracks are not observed by decreasing the depth of cut, the machining has been commonly considered to be in ductile mode. Although crack-free machining seems to be accomplished, the subsurface crack progress under the groove. The transition point determined by the subsurface crack is found to be a more shallow depth of groove than the point by the surface crack. Therefore the evaluation of the subsurface crack is significant especially in finish machining. The dependency of the depth of the subsurface crack on crystallographic direction is revealed. This dependency is due to the fact that mechanical properties of single-crystal silicon are affected by the crystallographic direction.