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Investigation of temperature characteristics and substrate influence on AlScN-based SAW resonators

: Ding, Anli; Reusch, Markus; Lu, Yuan; Kurz, Nicolas; Lozar, Roger; Christoph, Tim; Driad, Rachid; Ambacher, Oliver; Zukauskaite, Agne


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE International Ultrasonics Symposium, IUS 2018 : 22-25 October 2018, Kobe, Japan
Piscataway, NJ: IEEE, 2018
ISBN: 978-1-5386-3425-7
ISBN: 978-1-5386-3426-4
6 S.
International Ultrasonics Symposium (IUS) <2018, Kobe>
Fraunhofer IAF ()
AlN; AlScN; SAW; TCF; sputtering

It has been found that introducing Sc into AIN to form Al 1-x Sc x N can lead to a significant increase in piezoelectric response, making Al 1-x Sc x N a promising material for electroacoustic devices, such as frequency filters for mobile communications. 1 J.1m thick highly c-axis oriented Al 1-x Sc x N thin films were deposited on 100 mm Si(001)(x = 0, 0.14, 0.23, and 0.32)and on Al203(0001)(x = 0.14 and 0.23)substrates using reactive pulsed-DC magnetron sputtering and SAW resonators with wavelengths λ = 2–24 μm were fabricated. The effective electromechanical coupling k2eff of the resonators improved with increasing Sc concentration, for instance, the λ = 2 μm AIN (fs = 2.08 GHz)and Alo.68Sco.32N (fs = 1.83 GHz)resonators exhibited coupling of 0.6 % and 2.6 %, respectively. Furthermore, 3 % increase in resonant frequency and 9.6 % increase in coupling were observed when comparing λ = 2 μm resonators based on Al203 to those based on Si substrates. The temperature coefficient of frequency (TCF)was found to reach up to −27.4 ppm/K at x = 0.23 using Si substrates, while the equivalent resonators based on Al203 substrates exhibited lower TCF of −26.1 ppm/K. Thermal hysteresis errors were calculated to be ~1%. Employing Al203 substrates for λ = 2 μm Al 0.77 Sc 0.23 N-based resonators showed reduced TCF, higher resonant frequency, and higher coupling coefficient when compared to the same design resonators on Si substrates.