Piezoelectric properties of ScAlN thin films for piezo-MEMS devices

• Published in: 2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS) pp. 733 - 736
• Main Authors: Umeda, K., Kawai, H., Honda, A., Akiyama, M., Kato, T., Fukura, T.
• Format: Conference Proceeding Journal Article
• Language: English
• Published: IEEE 01.01.2013
• Subjects: Coupling coefficients; Devices; Electrodes; Frequency measurement; Mechanical systems; Piezoelectricity; Radio frequencies; Resonant frequency; Resonators; Sound velocity; Sputtering; Substrates; Temperature measurement; Thin films
• ISBN: 9781467356541; 1467356549
• ISSN: 1084-6999
• DOI: 10.1109/MEMSYS.2013.6474347

This paper reports the piezoelectric properties of ScAlN thin films. We evaluated the piezoelectric coefficients d 33 and d 31 of Sc x Al 1-x N thin films directly deposited onto silicon wafers, as well the radio frequency (RF) electrical characteristics of Sc 0.35 Al 0.65 N bulk acoustic wave (BAW) resonators at around 2 GHz, and found a maximum value for d 33 of 28 pC/N and a maximum -d 31 of 13 pm/V at 40% scandium concentration. In BAW resonators that use Sc 0.35 Al 0.65 N as a piezoelectric film, the electromechanical coupling coefficient k 2 (=15.5%) was found to be 2.6 times that of resonators with AlN films. These experimental results are in very close agreement with first-principles calculations. The large electromechanical coupling coefficient and high sound velocity of these films should make them suitable for high frequency applications.