On the scribing and subsequent fracturing of silicon semiconductor wafers

The integrated circuits deposited on silicon wafers are often separated by scribing with a diamond tool followed by bending to produce fracture. Using a commercial scribing tool we find permanent deformation and three types of crack. The median crack which propagates downwards is the objective of the scribing process. Lateral cracks which form, apparently following plastic deformation, may lead to chipping on either side of the scribing tool. These cracks and also the chevron cracks which form on the surface are very similar to cracks observed in scratching glass. However, in silicon, because of its anisotropy, the chevron cracks may be a serious problem since they can guide the median crack out of the scribing direction onto a preferred cleavage plane. This aspect leads to a brief discussion of the crystallography of silicon and recommendations for scribing configurations which should minimize undesired fracture. Finally, it is shown that the established methods of linear elastic fracture mechanics may be used to predict the maximum radius of curvature required to fracture a wafer containing a prescribed series of median cracks.