Wafer-level 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, silicon cap, and vertical feedthroughs through the glass. The integrated Pirani gauge has 0.6mTorr resolution at 0.1Torr and 0.2Torr resolution at 100Torr. Using the Pirani gauge, we have achieved ∼11Torr base pressure inside the vacuum package without a getter. Another package sealed at ∼80Torr has maintained its pressure for more than 2 months.