CMOS-MEMS 3-bit Digital Capacitors With Tuning Ratios Greater Than 60:1

3-bit microelectromechanical systems digital capacitors with greater than 60:1 tuning ratios are monolithically integrated with CMOS using a post-CMOS fabrication process. The digital capacitors are composed of many switched capacitors in parallel, which use a combination of vertical (out-of-plane) electrothermal actuation and lateral (in-plane) electrostatic actuation to toggle their capacitance value. Measured results demonstrate quality factors greater than 150 at 1 GHz and electrical self-resonant frequencies beyond 10 GHz. The capacitors can be switched in less than 1 ms with 4 V for electrothermal actuation and 20 V for electrostatic actuation. The effects of repeated actuation are presented to assess the reliability of the digital capacitors.