Large-Signal Behavior of Ferroelectric Micro-Electromechanical Transducers

Abstract

CMOS-MEMS resonators seamlessly integrated in advanced integrated circuit (IC) technology have the unique capability to enable unprecedented integration of stable frequency references, acoustic spectral processors, and physical sensors. Demonstrations of transducers leveraging piezoelectric properties of emerging ferroelectric materials such as Hafnium Zirconium Oxide (HZO) and Aluminum Scandium Nitride (AlScN) enable high figure of merit (FOM=k2Q) resonators over a wide range of frequencies. CMOS-integrated ferroelectric transducers using a thickness-scaled variant of these films for low voltage operation are feasible by leveraging advancements in ferroelectric random access memory (FRAM) and ferroelectric field effect transistors (FeFETs). However, until now, there has not been a full treatment of the effects of nonlinear large-signal behaviour on the performance of electromechanical systems built using ferroelectric transducers in the low coercive voltage regime. In this work, CMOS-MEMS resonators in a 130 nm process operating at ~700 MHz have been used as a vehicle for understanding the performance impact of nonlinear piezoelectric transduction on frequency references and acoustic filters. The first nonlinear large signal model for such resonators has been developed and employed to extract the nonlinear characteristics over different biasing and applied power. Operating conditions and design guidelines have also been developed for these applications, which can be extended to all resonators of this class. The crystallized understanding of large-signal operation of ferroelectric transducers presented in this work provides opportunities to design and demonstrate new capabilities of electromechanical devices in monolithic CMOS-MEMS platforms.