Hermetic packaging of resonators with vertical feedthroughs using a glass-in-silicon reflow process

A low-cost, hermetic wafer-level packaging solution with negligible parasitics suitable for MEMS resonators is presented. A glass cap with embedded 50μm diameter vertical single-crystal silicon feedthroughs is anodically bonded in vacuum to an SOI wafer prefabricated with mechanical resonators. This hermetic packaging process provides virtually zero-parasitic-capacitance vertical interconnects. A silicon-gold eutectic is used to ensure electrical contacts between the feedthroughs and the device wafer. An embedded wet-etched cavity in the glass cap allows mechanical motion of the resonator as well as the inclusion of a thin-film getter to further enhance and maintain vacuum. Temperature sweeps and quality factor measurements demonstrate the successful packaging of resonators using this technique.