RF solid-state vibrating transistors

This paper reviews our work on CMOS-integrated active MEMS resonators. Design, analysis and results are presented on CMOS-MEMS resonators fabricated at the Front-End-of-Line (FEOL) of a standard CMOS technology, realized without the need for any post-processing or packaging. Unreleased Resonant Body Transistors (RBTs) are driven capacitively to form longitudinal resonance confined by Acoustic Bragg Reflectors (ABRs), and sensed piezoresistively using an n-channel Field Effect Transistor (nFET). This first generation hybrid CMOS-MEMS RBTs consume footprints of 5μm×3μm, and operate above 11 GHz with quality factors (Q) of 24-30 and temperature stability <;3 ppm/K, matching well with theory. In addition, acoustic mode localization using features of standard CMOS technology is discussed. The active transduction mechanisms developed for CMOS-MEMS resonators can be extended to piezoelectric III-V semiconductors available in mm-wave ICs (MMICs). Our recent work on switchable MEMS-HEMT resonators in AlGaN/GaN is presented using a standard GaN MMIC platform, providing a means of realizing configurable high-Q MEMS resonators in MMICs for high frequency, high power applications.