Patent ID: 7807550
Filing Date: 2010-10-05
Classification: B81B,B81C,H01L

Abstract:
1. A method of making a wafer level package for a MEMS device including a silicon MEMS wafer and a silicon lid wafer bonded together to form a hermetically sealed cavity, comprising: performing a deep reactive ion etch on a front side of said lid wafer to form vias extending part way into said lid wafer; forming a layer of thermal silicon oxide on said front side so that said thermal silicon oxide extends into said vias to line walls thereof; subsequently depositing a layer of phosphorus-doped amorphous silicon on said layer of thermal silicon oxide by low pressure chemical vapor deposition so that said layer of phosphorus-doped amorphous silicon extends into said vias to fill said vias and thereby form rods of phosphorus-doped amorphous silicon surrounded by said thermal oxide; etching away said layer of phosphorus-doped amorphous silicon layer on said front side except over said rods to form phosphorus-doped amorphous silicon contact pads at the ends of said rods and to form seal rings in discrete regions on said front side; providing said silicon MEMS wafer with phosphorus-doped amorphous silicon seal rings and contact pads at locations corresponding to the seal rings and contact pads on the lid wafer, said phosphorus-doped amorphous silicon contact pads on said MEMS wafer having cantilevered extensions; bringing said lid wafer and said MEMS wafer together with said phosphorus-doped amorphous silicon seal rings and said contact pads of said respective wafers in alignment; forming a pressure bond between said seal rings and said contact pads of said respective lid and MEMS wafers to define a hermetically sealed cavity containing said cantilevered extensions; etching away a backside of said lid wafer to expose said phosphorus-doped amorphous silicon rods; and forming contacts pads on said exposed phosphorus-doped amorphous silicon rods to provide an electrical connection through said phosphorus-doped amorphous silicon rods to said cantilevered extensions in said hermetically sealed cavity.