Dependence of sensitivity loss on organic film thickness and influence of cantilever warpage in a piezoelectric wideband acoustic sensor coated with an organic film

A wideband acoustic sensor is reported, comprising a piezoelectric MEMS acoustic transducer with organic film-coated cantilevers. Considering the sensitivity reduction associated with the application of an organic film, it is necessary to optimize the material selection and thickness of the organic film. Therefore, the relationship between the thickness of the polyurethane film and the consequent loss in sensitivity is elucidated. Our findings demonstrate that the polyurethane film thickness should be approximately 0.5 mu m (or less) to limit sensitivity loss to 6 dB. Additionally, both simulations and experimental results reveal that the resonant frequency of the system is significantly influenced by the warpage of the cantilever. This study provides essential insights into optimizing the performance of MEMS acoustic transducers with organic film-coated cantilevers.