Diffraction based transmit-receive delay element with zero temperature coefficient

Abstract

In this paper we present a pulse-echo transmit-receive ultrasonic delay element that is stable over time and has a novel diffraction based zero temperature coefficient of delay at two temperatures. The delay element is based on a CMOS compatible aluminum nitride (AlN) piezoelectric transducer requiring no release step, further improving reliability and reducing cost of production. The silicon bulk wave propagation leads to stable operation owing to low loss within silicon and large mode volume. The delay element achieves <6ppm stability and demonstrates zero temperature coefficient at 430C and 720C.