Multi-spacer technique for low-voltage, high-aspect-ratio lateral electrostatic actuators

This paper presents low-voltage, high-aspect-ratio scaled lateral electrostatic actuators based on a four-mask multi-spacer process. The set of TEOS spacers, polysilicon hardmask, and buffer LTO layer is chosen as masking materials, resulting in a multi-spacer of LTO-TEOS and a stack of LTO-polysilicon hardmask. These mask sets with a photoresist mask are then transferred to an underlying polysilicon layer, creating high-aspect-ratio (>;5:1) polysilicon structures with sublithographic beam width and gap size. Two types of scaled actuators have been successfully designed and actuated with more than an order of magnitude reduction in actuation voltage compared to the regular process: coupled and decoupled designs of springs and movable electrodes.