Extracting mechanical Q factor of the pure AlN, ScAlN, and ZnO films without etching substrate

Abstract

The demand for the sharp RF filters is increasing to prevent interference in crowded frequency bands of the mobile communication. When other electrical loss and lateral acoustic wave leakage are adequately suppressed, the sharpness of BAW filters is determined by mechanical Q factors (Qm) of piezoelectric thin films. However, the Qm of various piezoelectric are not well known probably because a self-standing film structure (FBAR structure) are necessary to extract Qpiezo (Qm of the piezoelectric films). In this study, we grew pure AlN, ScAlN (40%), and ZnO thin films and ScAlN thin films with different Sc concentrations. In addition, we extracted the Qm of pure AlN, ScAlN, ZnO thin films, and ScAlN thin films with different Sc concentrations by using the method which can estimate Qm without removing substrates [1]. As a result, Qm of pure AlN thin film is higher than that of ScAlN and ZnO thin films and Qm of ScAlN and ZnO thin films are not different much. In addition, it was confirmed that the Qpiezo decreased with increasing Sc concentration.