STUDY ON SURFACE-ACOUSTIC-WAVE CHARACTERISTICS OF SIO2 INTERDIGITAL-TRANSDUCER/ZNO/DIAMOND STRUCTURE AND FABRICATION OF 2.5 GHZ NARROW-BAND-FILTER/

Surface acoustic wave (SAW) characteristics of the SiO2/interdigital-t ransducer(IDT)/ZnO/diamond structure were studied theoretically and ex perimentally. It was found that the 2nd mode in this structure can pro vide a zero temperature coefficient of frequency (TCF) as well as high velocity of 10,000 m/s and a large electromechanical coupling coeffic ient of 1.4%. Utilizing this wave, a 2.5 GHz narrow-band SAW filter wa s successfully fabricated with IDTs of 0.9 mu m finger width, which re sulted in superior characteristics for a retiming filter with a small insertion loss of 6.7 dB, Q value of 660 and small frequency deviation of 100 ppm in the temperature range from -40 to 85 degrees C. The ins ertion loss is smaller than any other retiming filters which have ever been reported with quartz, a conventional SAW material, and also the frequency deviation with temperature is smaller than that in the case of ST-cut quartz.