The SAW properties of sputtered SiO/sub 2/ on X-112/spl deg/Y LiTaO/sub 3/

Abstract

The surface acoustic wave (SAW) propagation properties on the X-cut plate, 112/spl deg/Y rotated, lithium tantalate (LiTaO/sub 3/) substrate with and without sputtered SiO/sub 2/ film layers have been investigated using interdigital transducer electrode structures. Thicknesses of SiO/sub 2/ of 500 nm and 1000 nm were sputter deposited on the X-112/spl deg/Y LiTaO/sub 3/ substrates. A series array of aluminum electrode patterns deposited on the film facilitated the excitation of a wide frequency band of harmonic waves up to 2.0 GHz, and permitted delineation of SAW velocity and propagation loss characteristics for several values of film-thickness to acoustic-wavelength (t//spl lambda/) ratio. A resonator pattern at the substrate/film interface, permitted the capacitance ratio (C/sub m//C/sub o/), related to coupling factor, and the temperature coefficient of frequency (TCF) to be measured. A high velocity pseudo-SAW (HVPSAW) mode was observed with a velocity near 6300 m/s.