Towards the development of backing layer for piezoelectric micromachined ultrasound transducers

In this work, we demonstrate the use of parylene C to reduce the ring down time and enhance the fractional bandwidth of a piezoelectric micromachined ultrasound transducer (PMUT). We further study the effect of increase in thickness of parylene C on the vibration response of a PMUT such as the fundamental resonant frequency and the maximum static deflection. It is found that the increase in the thickness of the deposited parylene C film, decreases the quality factor of a PMUT, following a linear trend, with negligible effect on its fundamental resonant frequency. This can be considered to be an important finding as far as the field of ultrasound imaging is concerned, since this technique paves the way to control the axial resolution of the B-mode ultrasound scan by simply tuning a PMUT's quality factor.