Low-temperature growth of piezoelectric AlN film by rf reactive planar magnetron sputtering

Abstract

A single-crystalline aluminum nitride film is grown on a basal-plane sapphire substrate and the c-axis-oriented films are grown on glass and gold-film substrates at substrate temperatures as low as from 50 to 500 °C by using reactive rf planar magnetron sputtering. Surface acoustic waves are generated in both structures where interdigital transducers are located on the top of an aluminum nitride film and at the interface between the film and the substrate sapphire. The effective surface acoustic wave coupling factor k2 is 0.09 and 0.12%, respectively, for these interdigital transducer configurations. The aluminum nitride films sputtered on a gold film on a glass rod and on a glass sheet itself are also piezoelectric and used as bulk and surface acoustic wave transducers, respectively. These piezoelectric aluminum nitride films on glass and metal-film substrates have become available for the first time because film growth at low temperature has become possible in the present study.