The CMOS-MEMS process flow is illustrated in the following figure. It is a maskless post-CMOS process and uses only dry-etch steps: deep silicon etch, anisotropic oxide etch and RIE aluminum etch. Aluminum is the etching mask for oxide etch, and oxide is the etching stop for aluminum etch and the etching mask for deep silicon etch. All the materials and patterns are from CMOS fabrication. No masks or lithography steps are needed. By sacrificing one metal layer, electrical isolation of silicon is obtained without affecting the deep silicon etch for high-aspect-ratio microstructures.

This new CMOS-MEMS process is completely CMOS-compatible and provides robust single-crystal silicon (SCS) microstructures and electrical isolation of SCS. It is very suitable for making integrated inertial sensors, high-Q resonators and micromirrors.