Low Temperature Growth of Piezoelectric AlN Film for Surface and Bulk Wave Transducers by RF Reactive Planar Magnetron Sputtering

Abstract

A singlecrystallin e aluminum nitride (UN) film has been grown epitaxial onto a basal plane sapphire substrate and also a c-axis oriented AlN film has been grown on a glass or metal-film substrate at substrate temperatures as low as from 5OoC to 500°C by using reactive rf planar magnetron sputtering. Because of this low substrate temperature, it has become possible to put IDT’s at the interface between an AlN film and its sapphire substrate. by these IDT’s at the i nterface as well as by IDT’s on the top of AlN films. sputtered on gold film-electrodes on Kovar glass rod and sheet are also piezoelectric and used as bulk or surface acoustic wave transducer respectively. Several electromechanical constants for AlN have been measured by using thin AW plates of several t en microns in thickness removed from glass or gold-film substrates, shoving AlN is a promising piezoelectric material at high frequency. Surface acoustic waves are generated and