Development of wafer scale encapsulation process for large displacement piezoresistive MEMS devices

The goal of the presented work is to develop and demonstrate a fabrication process for thin film encapsulation of MEMS devices with large gaps by modifying an existing technique. The process is being developed for encapsulation of silicon micro machined gyroscope which will be fabricated on SOI (silicon-on-insulator) wafers using Bosch DRIE etching technique. The encapsulation of the device is carried out using epitaxial polysilicon in order to provide a high vacuum inside the device chamber. This technique helps in reducing the die area and the vacuum inside the encapsulation increases the quality factor Q and sensitivity of the device. In this paper we describe a unique method of wafer scale encapsulation of large gaps using sacrificial silicon structures that are completely oxidized.