Even-order thickness-shear mode resonators using X-cut LiTaO3 plates realized by a direct bonding technique

Even-order thickness-shear mode resonators with good temperature characteristics have been achieved by applying direct-bonding techniques to X-cut LiTaO₃ single crystals. The variations in the resonance frequency of their main fast thickness shear mode was less than 500 ppm over the temperature range of -10 to 60°C. Moreover, the results of studies on strip type chip resonators using direct-bonded x-cut LiTaO₃ wafers suggest that fabrication of small sized resonators with no spurious response is feasible. Their typical Q-value was between 3000 and 5000, and the resonant resistance was 10-20 Ω at 13 MHz. These values an ideal for a range of applications. We confirmed that the direct bonding technique was particularly suitable for realizing high frequency resonators because the thickness of the resonator could be double that of a conventional fundamental resonator