Chip level packaging for MEMS using silicon cap

A new hermetic seal package using silicon cap has been developed for MEMS devices. This package method was combined with fabrication of MEMS device, which utilized bulk silicon micromachining and bonding technology. The anodic bonding between the silicon cap and the glass substrate on which the MEMS devices stand was performed to package the devices. Before the bonding package, a thermal oxide silicon layer was grown to acquire insulation between the silicon cap and the metal lines on glass substrate. A Z-axis accelerometer using this package method has been successfully demonstrated in a 4-inch Fab. The influence on the accelerometer performance of the package method was examined. The testing results showed the hermeticity was satisfied with the requirements of resonant or inertial sensors, and the sensitivity of the accelerometer was about 16 fFg(-1).