A MEMS Tunable Capacitor Based on Plastically Deformed Vertical Comb Sets

ABSTRACT We report microfabricated tunable capacitors based on plastically deformed vertical comb sets using a batch process. The arrangement of cascaded comb finger sets and the uniqueness of the angular vertical comb actuators enable large tuning ratio with a small angular displacement. The capacitors are made of 50µm-thick single-crystal silicon on SOI wafer and actuated by self-aligned vertical comb-sets giving a tuning ratio of 4.93 from 0.194 to 0.96pF with a tuning voltage of 100 Volts. As such, this tunable capacitor could find applications in RF communication such as parametric amplifiers, harmonic frequency generators and voltage-controlled oscillators. INTRODUCTION MEMS tunable capacitors could be key components in the development of radio-frequency (RF) MEMS since they have the potential of achieving high quality factor for operations in parametric amplifiers, harmonic frequency generators and voltage-controlled oscillators. Previously, tunable MEMS capacitors have been demonstrated using parallel-plate approach by using the surface micromachining process with limited tuning performance due to the inherit pull-in phenomeno