Tuning of sol–gel derived PZT MEMS resonators

Abstract

This paper demonstrates the tunability of resonant frequencies for MEMS piezoelectric resonators acting in the d 33 mode by experiment and theoretical analysis. Thin-film MEMS beams made by sol-gel PZT processing are first fabricated and tested to investigate the tuning capability. The three-layered interdigitated-electrode trapezoidal beams are then modeled by finite element analysis for validation. Beam curl and undercutting are also examined to present an alternative way of finding the stress gradient in comparison to Stoney's formula. The experimental and analytical results indicate that piezoelectric MEMS resonators have the ability to passively tune their resonant frequencies between open-circuit and short-circuit frequencies. Tuning of 0.2-0.6% is demonstrated experimentally, which compares with finite element predictions of 1.02-1.08%. Consideration is given to the reason for the differences in experimental percentages versus those predicted numerically, including the use of bulk PZT values in the ANSYS simulations, the undercut and curling effects of fabrication, and the low percentage of piezoelectric poling in the length direction.

Electrostatically coupled vibration modes in unimorph complementary microcantilevers

“…Active resonator tuning based on electrical or mechanical spring softening or hardening of the resonator flexure resulting in the frequency shift ranging from 0.1% to 6.5% has been demonstrated. [4][5][6][7] A larger tuning range, however, is required for resonators that can operate in multiple frequencies to avoid the device complexity and signal dissipation caused by the duplication of the resonators and by the use of switches.…”