Sacrificial grid release technology: A versatile release concept for MEMS structures

Micro-electro-mechanical-systems (MEMS) structures with different in-plane dimensions often need to be released simultaneously from the bulk of the wafer and a single dry etching or wet etching technique cannot fulfill all release requirements. In this paper we present a universally applicable solution to release MEMS structures with different surface areas in a controlled and uniform way, which combines isotropic etching of a sacrificial silicon support structure by xenon difluoride with a predefined etch surface made by deep reactive ion etching. Two applications of this Sacrificial Grid Release Technology are presented, in which MEMS devices are released in silicon-on-insulator wafers. The demonstrated applications involve the release of microstructures with in-plane dimensions ranging from tens of micrometers to a few millimeters. The sacrificial silicon structure provides mechanical support which allows freedom in process flow design for fragile MEMS structures. The release technique can also be used to separate the chips from the wafer.