Several techniques for fabrication of through-wafer vias in silicon have been compared in terms of achievable via diameter, shape and geometry and their influence on mechanical strength of silicon dies/wafers. Assessed techniques are: powder blasting, laser melt cutting, laser ablation, and deep reactive ion etching. The resolution of each method and influence on geometry was evaluated by fabrication through-wafer holes and slots in 240µm-thick silicon wafers. The mechanical strength is measured using ring-on-ring (RoR) and four-point bending methods. Additional stress-relief post-processing was applied to improve mechanical strength. Comparing performance of bipolar transistors before and after fabrication of laser ablated vias.
