Three-dimensional integration of suspended single-crystalline silicon MEMS arrays with CMOS

We present a generic three-dimensional (3-D) integration method to fabricate suspended single crystalline silicon (SCS) MEMS arrays on CMOS. The method is based on transferring the SCS device layer of SOI on the top of CMOS. For general purpose, thin MEMS arrays with long supporting arms are demonstrated. The fabrication process is clarified in details. Mechanical reliability of the suspended structure is addressed with drop tests and is improved by optimizing the Cu plating parameters. The residue stress is compensated by tailoring the thickness of the oxide layer and flat free-standing structures are achieved. This method is applicable to a large variety of SCS MEMS including accelerometers, gyroscopes, micro-mirrors, RF MEMS switches, and resonators.