Maximization of Transmitted Acoustic Intensity from Silicon Integrated Piezoelectric Ultrasound Transducers

Abstract

2D phased array ultrasonic transducers realized through the combination of bulk piezoelectric ceramics and complementary metal-oxide-semiconductor (CMOS) integrated circuits (IC) are enabling a new range of wearable ultrasound therapeutic applications. Traditional therapeutic ultrasound transducers have an air backing layer to maximize transmitted acoustic intensity. Yet, the pairing of piezoelectric transducers and silicon substrates commonly used in CMOS is still poorly understood. We integrated lead zirconate titanate (PZT) film on silicon membranes of various thicknesses to understand the im-pact of the silicon backing on the performance of bulk piezoe-lectric ultrasound transducers. The transducers with thinner sil-icon membranes exhibited higher acoustic intensity (up to 1.95 times while taking into account frequency shift), which is con-sistent with the simulation in finite element modeling. Transduc-ers with silicon substrate also demonstrated a consistent shift to a higher resonance frequency.