Incrementally etched electrical feedthroughs for wafer-level transfer of glass lid packages

This paper reports on a simple fabrication technique to create full wafer-level transferred glass-lid encapsulations for near-hermetic packaging of MEMS devices using adhesive wafer bonding with Benzocyclobutene. Furthermore, a new technique to create low-density feedthroughs through the glass wafer for electrical interconnections from the back to the front side of the glass-lids is introduced. The through-wafer vias are fabricated by combining a mechanical etch-step by powder-blasting from the back side and a subsequent short hydrofluoric acid wet etch step. The advantage of this via technique is that the major part of the via is etched without going completely through the wafer, allowing standard surface micromachining processes on the front side of the glass wafer before the final opening of the via.