High-acoustic-impedance tantalum oxide layers for insulating acoustic reflectors

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2012-03, Vol.59 (3), p.366-372
• Main Authors: Capilla, J., Olivares, J., Clement, M., Sangrador, J., Iborra, E., Devos, A.
• Format: Article
• Language: English
• Subjects: Acoustic impedance; Acoustic measurement; Acoustic measurements; Acoustic wave devices, piezoelectric and piezoresistive devices; Acoustical measurements and instrumentation; Acoustics; Applied sciences; Cross-disciplinary physics: materials science; rheology; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Impedance; Materials science; Materials testing; Physics; Reflectors; Resonators; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Spectroscopy; Substrates; Tantalum oxides; Transduction; acoustical devices for the generation and reproduction of sound; Velocity measurement; X-rays
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2012.2205

This work describes the assessment of the acoustic properties of sputtered tantalum oxide films intended for use as high-impedance films of acoustic reflectors for solidly mounted resonators operating in the gigahertz frequency range. The films are grown by sputtering a metallic tantalum target under different oxygen and argon gas mixtures, total pressures, pulsed dc powers, and substrate biases. The structural properties of the films are assessed through infrared absorption spectroscopy and X-ray diffraction measurements. Their acoustic impedance is assessed by deriving the mass density from X-ray reflectometry measurements and the acoustic velocity from picosecond acoustic spectroscopy and the analysis of the frequency response of the test resonators.