Nonlinearity Driven Higher Order Harmonics in CMOS-MEMS Resonators

In this work, we explore the generation of higher order harmonics in an electrostatically actuated wide-width beam resonator fabricated by a CMOS-MEMS Titanium Nitride Composite (TiN-C) platform. The explored TiN-C platform can achieve a gap of 400 nm with high transduction efficiency, low motional resistance ($R_{m}$) and enhanced frequency stability. A record-high Radius of Curvature (R.O.C of 11.9 cm) of the fabricated wide-width pseudo free-free beam is achieved among CMOS-MEMS counterparts. The fundamental mode is measured at a resonance frequency of 9.8 MHz. The second and the third higher order harmonics are observed when the resonator is excited at its fundamental flexural mode in the non-linear region. A varying AC voltage drives the resonator from the linear regime into non-linear regime for an applied DC bias of 80 V. The presence of harmonics is confirmed electrically and optically through measurement using the Spectrum Analyzer and the Laser Doppler Vibrometer (LDV) respectively.