High-order composite bulk acoustic resonators

In this article, we present lateral and thickness mode low-impedance UHF resonators to obtain dispersed- frequency devices simultaneously on a single substrate. The low-impedance is enabled by using high-order modes of resonators consisting of a piezoelectric transduction film on an underlying silicon layer. The impedance of these devices reduces as mode number increases. This is attributed to the increase in transduction area. The lowest measured impedance is 55Omega at 373MHz. Resonators with 373MHz and 640MHz lateral modes and 2.5GHz thickness modes from the same substrate are presented.