Cross-sectional quasi- Lamé modes in thin-film piezoelectric-on-silicon resonators

Abstract

In this work, it is demonstrated for the first time that cross-sectional quasi-Lamé modes (CQLM) could be efficiently excited in silicon with reasonably high quality factor (Q). Third-harmonic Lamé modes of a silicon block are piezoelectrically exited in thin-film-piezoelectric on silicon (TPoS) resonators in which the thickness is chosen to be in proximity of half acoustic wavelength. Finite element analysis is used to show that the support loss in these resonators could be reduced by an order of magnitude through usage of acoustic isolation techniques. A quality factor of 14,500 is measured in partial vacuum for a third-harmonic 67 MHz CQLM-TPoS resonator designed within a circular acoustic isolation frame and fabricated on a 40μm thick silicon-on-insulator (SOI) substrate.