Characterization of Metal Effect on Solidly Mounted AlScN on CMOS

In this paper, the pulse-echo voltage response of CMOS integrated Al
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N piezoelectric transducer are measured and compared to that with AlN transducer. The AlScN transducers are fabricated on a 180nm CMOS wafer, with six levels of metallization. A 60ns wide RF pulse packet drives the transducers with carrier frequency ranging from 700 MHz to 3 GHz. The voltage insertion loss of the reflected signal compared to the transmit signal is measured for AlScN and AlN transducers, above different combinations of metal stacks. The AlScN transducers exhibit a lower insertion loss and broader bandwidth compared to the AlN transducers. A UHF-120 PolyTec vibrometer is used to measure the piezoelectric displacement of the transducer versus frequency. The piezoelectric displacement of the AlScN transducer is ~10 times greater than the AlN transducers. The experimental measurements indicate that monolithically integrated AlScN on CMOS might provide higher performance SNR compared to AlN films in BAW applications.