Analytical stress characterization after different chip separation methods

Synchrotron white beam X-ray topography (SXRT) and photoelastic stress measurements were used to characterize resulting strain fields after mechanical dicing and laser grooving of bare silicon wafers. The distribution and propagation of the strain fields can be characterized by both methods. In contrast to mechanical dicing, the laser grooving process creates an inhomogeneous strain field. The influenced area is three times larger compared to mechanical dicing. The effect of the dicing procedure on the resulting mechanical fracture strength of the silicon chips was investigated by 3-point bending tests. The fracture strength of samples with an additional laser grooving process was significantly reduced under tensile load. The fracture pattern of the samples indicated that the strain field generated by the separation process causes initial points for μ-cracks propagation under mechanical load. This analysis can help to optimize dicing processes in order to attain a better reliability of chips with regard to process yields.