The Behavior of Gold Metallized AlN/Si- and AlN/Glass-Based SAW Structures as Temperature Sensors

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 68; no. 5; pp. 1938 - 1948
• Main Authors: Nicoloiu, Alexandra, Stan, George E., Nastase, Claudia, Boldeiu, George, Besleaga, Cristina, Dinescu, Adrian, Muller, Alexandru
• Format: Journal Article
• Language: English
• Published: United States IEEE 01-05-2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum nitride; Coupling of modes (COM); Crystal structure; Crystallography; finite element method (FEM) simulation; Frequency shift; GHz operation; Glass substrates; III-V semiconductor materials; Magnetron sputtering; Metallizing; Morphology; Piezoelectricity; Rayleigh mode; Resonance; resonance frequency; Resonant frequency; Sensitivity; Silicon substrates; Surface acoustic waves; surface acoustic waves (SAWs); Temperature; Temperature measurement; temperature sensor; Temperature sensors; Thin films; Transducers
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2020.3037789

Thin AlN piezoelectric layers have been deposited on high resistivity Si and glass substrates by reactive RF magnetron sputtering, in order to manufacture one-port gigahertz operating surface acoustic wave (SAW)-type resonators to be used as temperature sensors. The growth morphology surface topography, crystallographic structure, and crystalline quality of the AlN layers have been analyzed. Advanced nanolithographic techniques have been used to manufacture structures having interdigitated transducers with fingers and finger interdigit spacing width in the range of 250-170 nm. High resonance frequency ensures the increase of the sensitivity, but also of its normalized value, the temperature coefficient of frequency (TCF). The resonance frequency shift versus temperature has been measured in the −267°C−+150°C temperature range, using a cryostat setup adapted for on wafer microwave measurements up to 50 GHz. The sensitivity and the TCF were determined in the 25 °C-150 °C temperature range.