190 nm excimer laser drilling of glass slices: Dependence of drilling rate and via hole shape on the diameter of the via hole

The authors have investigated the effect of the via hole diameter on the laser drilling rate of glass as well as the shape of the drilled via holes. An Ar-F-2 based 193 nm UV excimer laser was used in this study. The via holes with a diameter of 120 mu m showed a 7.5 degrees-9 degrees angled, tapered side wall, and the drilling rate was relatively constant at around 17 mu m/s. For the smaller via holes with diameters ranging from 30-80 mu m, significantly different results were obtained due to laser reflection from the tapered side wall of the via hole leading to the drilling rate being slightly increased and via hole becoming conical in shape. For the smallest via holes with an entrance diameter of 10 mu m, the resulting hole showed a very high aspect ratio, with a funnel shaped via hole and a significantly reduced drilling rate.