PREPARATION OF ALUMINUM NITRIDE THIN-FILMS BY REACTIVE SPUTTERING AND THEIR APPLICATIONS TO GHZ-BAND SURFACE-ACOUSTIC-WAVE DEVICES

Single crystal aluminum nitride (ALN) thin films were prepared by a low-temperature reactive sputtering on basal plane sapphire [(001)Al2O3] at a substrate temperature of less than 315 degrees C. Surface acoustic wave (SAW) characteristics with an interdigital transducer /(001)AlN/(001)Al2O3 structure were investigated. The phase velocity and temperature coefficient of delay time are 5750-5765 m/s and 55-63 ppm/degrees C at KH=1.2-1.6, respectively. Resonator-type 1-GHz-band SAW filters with its structure were fabricated. The insertion loss and suppression were 23 dB and more than 20 dB, respectively.