4H-sic electrostatic cantilever actuator released by photoelectrochemical etching and application for frequency mixing

This paper reports an electrostatically actuated single crystal 4H-SiC cantilever performing frequency mixing. In order to achieve electrostatic actuation, and solve the challenge of releasing MEMS structures due to the extreme chemical hardness of 4H-SiC, an n-p-n homoepitaxial structure was chosen, with cantilever actuators released by photoelectrochemical (PEC) etching. The middle p-SiC layer acts as a sacrificial layer in PEC etching to release actuators, and also isolates the top n-SiC cantilever from the bottom n-SiC substrate to realize electrostatic actuation. This study shows that electrostatically actuated RF MEMS capable of operating in harsh environments are attainable by single crystal 4H-SiC owing to its superior material properties including chemical and thermal stability, high ratio of Young's Modulus to density, etc.