WAFER SCALE PACKAGING OF MEMS BY USING PLASMA ACTIVATED WAFER BONDING

摘要

Plasma assisted direct bonding has been investigated for wafer scale encapsulation of micro-electromechanical systems (MEMS). Direct bonding requires smooth and flat wafer surfaces, which is seldom the case after fabrication of MEMS device. Therefore, we have used polished CVD oxide as an intermediate bonding layer. The oxide is deposited over the MEMS device and planarized. Then the device wafer is bonded to a silicon cap wafer by using plasma activation based low temperature bonding method. We have also studied methods for surface protection for cases where the device to be encapsulated requires further processing steps after polishing Two different methods to form electrical contacts into the encapsulated device are presented. To test the viability of the developed methods for MEMS encapsulation, we have sealed polysilicon resonator structures at a wafer level.