Rapid and High Throughput Formation of Through Glass Vias

Interest in glass for integrated circuit (IC) packaging and interposer applications has accelerated in recent years, due to its favorable mechanical and electrical properties compared to current advanced materials. This report describes our recent results on through glass via (TGV) drilling, utilizing a novel process employing a single laser source with an engineered pulse duration, pulse repetition frequency, and average power to rapidly form TGVs in 50 and 100 mu m thick glass. The process forms TGVs with a similar to 10 mu m diameter with zero taper, smooth sidewalls and minimal splash; the dimensions of these TGVs meet the requirements for next-generation interposers to replace through silicon vias. Unlike Bessel beam based processes, this process is compatible with high bandwidth beam steering technologies (galvanometers and acousto-optic deflectors (AODs)), enabling an industrially viable throughput in high-density drill patterns of more than 10000 vias per second. The formation dynamics of the TGVs are elucidated using multiphase simulations and in-situ spectroscopic methods. Stress mitigation in the fully-formed TGVs is explored through annealing studies; an alternate approach utilizes heating of the glass substrate during the laser processing to minimize stress formation during the drilling process. Both methods are shown to mitigate embedded stress and avoid cracking.