Surface acoustic wave characterization of PECVD films on galliumarsenide

摘要

Surface-acoustic-wave (SAW) measurement techniques can beneffectively used to determine the acoustic properties of dielectric andnpiezoelectric films. Such films can be used for the development ofnsemiconductor-integrated microwave-frequency surface and bulk acousticnwave devices. The acoustic properties of silicon nitride, siliconnoxynitride, silicon carbide, and TEOS glass, deposited bynplasma-enhanced chemical-vapor-deposition (PECVD) on GaAs, have beenncharacterized using linear arrays of SAW interdigital electrodesnoperating in the harmonic mode over the frequency region from 30 MHz tonabove 1.0 GHz. The elastic constants of these amorphous films have beenndetermined by fitting theoretical dispersion curves to the measured SAWnvelocity characteristics. Frequency-dependent SAW propagation-lossnvalues have been determined from the observed linear change in loss as anfunction of transducer separation. Preliminary measurements of thentemperature coefficient of frequency (TCF) for SAW propagation of thenfilms on GaAs are also given