Evaluation of acoustic properties of thin films using piezoelectric overtone thickness-mode resonators

摘要

Measurement of acoustic properties of a thin film whose thickness is less than several μm is not easy. In this paper, a new simple evaluation method for acoustic properties, such as density and stiffness, of thin films is presented. In this method, the acoustic properties are evaluated from the measured resonance frequency change of high overtones of a piezoelectric thickness-mode resonator due to deposition of a test film on the resonator surface. This method is applied to evaluation of acoustic properties SiO{sub}2, Al{sub}2O{sub}3, TiO{sub}2, and ZnO film. The resonance frequencies calculated using the evaluated density and stiffness agree well with the measured values. This suggests that the properties of thin films are well evaluated.