Demonstration of MHz piezoelectric micromachined ultrasonic transducers array and its potential application for biomedical treatment

In this paper, we successfully developed the 24 × 31 piezoelectric micromachined ultrasound transducers (PMUTs) array with 8 inch complementary metal oxide semiconductor (CMOS) compatible processes. Scandium aluminum nitride (Sc x Al1− x N) thin film ( x = 20%) was used as the piezoelectric material. The PMUTs array was fabricated on 8 inch cavity silicon-on-insulator wafers with the device silicon layer thickness of only 3 μ m and a cavity pitch of 59 μ m. The wafer-level electrical test was conducted using inline auto-prober and the yield rate >90% was achieved across the 8 inch wafer. The following acoustic test on our PMUTs array (1.5 mm × 2.0 mm) indicated the transmit sensitivity of 18.4 kPa V −1 @ 10 mm @ 11.6 MHz in oil with −3 dB bandwidth of 2.3 MHz. In order to validate the potential of using PMUTs array for biomedical treatments, subsequent ultrasonic heating experiments were carried out on a silicone block. A temperature rise of 4 °C was achievable in about 50 s. These results demonstrate that the potential of using PMUTs array as a disposable biomedical device in many therapeutic applications, for example, a treatment for dry eye disease.