Variable Capacitors and Tunable LC-Tanks Formed by CMOS-Compatible Metal MEMS for RF ICs

Variable capacitors are fabricated in standard silicon substrate by using a CMOS-compatible metal MEMS process. A low temperature process is implemented with two layers of mask. The suspended structure of the variable capacitor effectively depresses substrate loss, thereby, achieving both high Q-factor and high self-resonance frequency. The tunable-capacitor can be flexibly connected into an RFIC, and a rotationally driven structure is proposed and formed with anti-vibration capacity for mobile applications. By integrating the variable capacitor with a solenoid inductor, a parallel tunable LC-tank is fabricated and tested, resulting in a broad tuning-range of resonant frequency. With the low temperature post-CMOS process, the high-performance variable capacitors and LC-tanks are promising in RF ICs.