Fabrication and characterization of single-crystal 4H-SiC microactuators for MHz frequency operation and determination of Young's modulus

Abstract

Silicon carbide (SiC), a wide bandgap semiconductor, is more desirable over conventional silicon (Si) to satisfy the increasing demands for microelectromechanical system (MEMS) to operate in harsh environments due to the excellent physical, mechanical and chemical inertness. Research in MEMS devices based on single or polycrystalline SiC on Si or SOI substrate, such as 3C-SiC polytype, have been widely carried out. Another promising candidate is "all"-SiC, i.e., homoepitaxial single crystal SiC layer on single-crystal SiC substrate, such as 4H and 6H-SiC polytypes. They truly exploit the superior material properties of SiC and provide advantages for MEMS devices to operate in hostile conditions. In this work, 4H-SiC MEMS actuators in cantilever and bridge configurations were fabricated by a surface micromachining process, and their dynamic responses were characterized to determine Young's modulus of 4H-SiC and frequency performance. Resonant frequencies of 1.208 MHz from cantilever and 1.338 MHz from bridge actuators were achieved. These high frequency operation capabilities are particular interesting for ultrafast and high resolution sensors and actuators.