A sealed cavity TFR process for RF bandpass filters

Abstract

Thin film bulk acoustic wave resonators (TFRs) show considerable promise as a silicon compatible integrated solution for RF bandpass filters with center frequencies in the 1-2 GHz range. This paper presents a VLSI compatible sealed cavity TFR process using reactively sputtered AlN as the piezoelectric film. The devices are free-standing and have a fundamental longitudinal resonance at 1.36 GHz with an insertion loss of 3.5 dB, a K/sub eff//sup 2/ of .4 %, and a Q/sub series/ of 210.