Fabrication and Characterization of a Wafer-Level MEMS Vacuum Package With Vertical Feedthroughs

This paper reports a MEMS vacuum package with vertical feedthroughs formed in a glass substrate all at the wafer level. This approach satisfies requirements for MEMS vacuum packages, including small size, vacuum/hermetic capability, sealed and low parasitic feedthroughs, wafer-level processing, compatibility with most MEMS processes, and low cost. It also enables flip-chip solder attachment to a PC board. The package has an integrated micro-Pirani gauge on a glass substrate for in situ monitoring, a silicon cap, and vertical feedthroughs through the glass. The integrated Pirani gauge has 0.6 milli-torr resolution at 0.1 torr and 0.2 torr resolution at 100 torr. Using the Pirani gauge, the fabricated vacuum package is characterized. The package has maintained ~33 torr base pressure with plusmn1.5 torr uncertainty for more than four months without a getter. The long-term measured pressure uncertainty is from the measurement setup and environment, and can be improved using a getter inside the package. 2007-0160]