A high-Q tunable micromechanical capacitor with movable dielectric for RF applications

A high-Q, tunable, micromechanical capacitor has been realized using an IC-compatible, electroplated-metal surface micromachining technology and demonstrated with quality (Q-) factors in excess of 290-the highest reported to date for on-chip tunable capacitors at frequencies near 1 GHz. The key feature in this design that makes possible such high on-chip Q is the method for capacitive tuning, which in this design is based on moving the dielectric between the capacitor plates, rather than moving the plates themselves, as done in previous designs. One version of this design achieves a measured Q of 291 at 1 GHz (C=1.21 pF) with a tuning range of 7.7% over 10 V of control voltage, and an expected self-resonant frequency (SRF) of 19 GHz. In another design, with a wider tuning range of 40% over 10 V, a Q of 218 is achieved at 1 GHz (C=1.14 pF).