Influence of Silicon on Quality Factor, Motional Impedance and Tuning Range of PZT-Transduced Resonators

Abstract

This paper provides a quantitative comparison and explores the design space of PZT-only (Lead Zirconium Titanate) and PZT-on-Silicon length-extensional mode resonators for incorporation into RF MEMS filters and oscillators. We experimentally measured the correlation of motional impedance (R X ) and quality factor (Q) with the resonators' silicon layer thickness (t Si ). For identical lateral dimensions and PZT-layer thickness (t PZT ), the PZT-on-Silicon resonator has higher resonant frequency (dominated by silicon), higher Q (5,100 vs. 140) and lower motional impedance (51 Ω vs. 205 Ω). However, PZT-only resonator demonstrated much wider frequency tuning range (5.1% vs. 0.2%).

An analytical study on interfacial dissipation in piezoelectric rectangular block resonators with in-plane longitudinal-mode vibrations

“…Since a piezoelectric block resonator operates in one of its bulk-modes, thermoelastic damping and surface loss are typically negligible [8,9]. At the same time, one or two support beams that are used to fix a block structure of the resonator to the substrate are located at one of the resonant nodes of the block structure, so its anchor loss becomes slight [1,10]. The electrostatic counterparts of these piezoelectric resonators have demonstrated a much higher Q.…”

“…Among various piezoelectric block resonators developed so far, some utilize silicon as a structural layer and piezoelectric material as a transduction layer [1][2][3], while others directly employ piezoelectric material as both the structural layer and the transduction layer [1,[4][5][6]. Meanwhile, different piezoelectric materials, including PZT [1], Zinc oxide (ZnO) [2,3], Al 0.3 Ga 0.7 As [4], and aluminum nitride (AIN) [5,6], have been used in fabricating these block resonators. Despite their high electromechanical coupling coefficient, low mechanical quality factors (Q) demonstrated by these piezoelectric block resonators have prevented them from lowering their motional resistance for integration into 50 RF circuits [4].…”

“…Piezoelectric rectangular block resonators operating in one of their in-plane longitudinal-modes have been developed for their potential applications in wireless communications and sensor networks [1][2][3][4][5][6], due to their attractive features of high power handling capability, high electromechanical coupling coefficients, as well as low operation voltage. Among various piezoelectric block resonators developed so far, some utilize silicon as a structural layer and piezoelectric material as a transduction layer [1][2][3], while others directly employ piezoelectric material as both the structural layer and the transduction layer [1,[4][5][6].…”

Experimental Investigation of Strain Rate Dependence of Nanocrystalline Pt Films

“…However, there are no experimental results available in the literature for Pt thin films as a function of strain rate. This investigation aims at filling this gap, especially because the active PZT material used in RF-MEMS [18] has short response times and, therefore, can expose the attached Pt electrodes to a wide range of strain rates. The experiments presented here were conducted with 400 nm thick Pt films but they can be readily applied to films with other thickness.…”

Gallium nitride-on-silicon micromechanical overtone resonators and filters

“…1). TPoS resonators [4] have been demonstrated in prior work using more conventional piezoelectric materials such as AlN [5], ZnO [6] and PZT [7]. In most of these implementations, the silicon layer dominates the stack structure and thus the resonance frequency and mode shape.…”