Use of fluorine-doped silicon oxide for temperature compensation of radio frequency surface acoustic wave devices

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 59; no. 1; pp. 135 - 138
• Main Authors: Matsuda, S., Hara, M., Miura, M., Matsuda, T., Ueda, U. M., Satoh, Y., Hashimoto, K.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic wave devices, piezoelectric and piezoresistive devices; Acoustics; Applied sciences; Atomic measurements; Atomic structure; Coefficients; Devices; Educational institutions; Electronics; Exact sciences and technology; Fluorine; Fourier transforms; Fundamental areas of phenomenology (including applications); Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon dioxide; Silicon oxides; Studies; Surface acoustic wave devices; Surface acoustic waves; Temperature; Temperature compensation; Temperature measurement; Transduction; acoustical devices for the generation and reproduction of sound; Elastic constant; Acoustic wave device; Radio wave; Oxide layer; Doping; Acoustic surface waves; Experimental study; Radiofrequency; Layer thickness; Electromechanical coupling; Wavelength; Infrared spectrometry; Temperature coefficient; Acoustic properties; Thermal compensation; Silicon oxides; Lithium niobates; Coupling factor
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2012.2164

This paper investigates acoustic properties, including the temperature coefficient of elasticity (TCE), of fluorine-doped silicon oxide (SiOF) films and proposes the application of the films to the temperature compensation of RF SAW devices. From Fourier transform infrared spectroscopy (FT-IR), SiOF films were expected to possess good TCE properties. We fabricated a series of SAW devices using the SiOF-overlay/Cu-grating/LiNbO 3 -substrate structure, and evaluated their performance. The experiments showed that the temperature coefficient of frequency (TCF) increases with the fluorine content r, as we expected from the FT-IR measurement. This means that the Si-O-Si atomic structure measurable by the FT-IR governs the TCE behavior of SiO 2 -based films even when the dopant is added. In comparison with pure SiO 2 with the film thickness h of 0.3 wavelengths (λ), TCF was improved by 7.7 ppm/°C without deterioration of the effective electromechanical coupling factor K2 when r = 3.8 atomic % and h = 0.28λ. Fluorine inclusion did not obviously influence the resonators' Q factors when r <; 8.8 atomic %.