Development of Aluminum Scandium Nitride Thin Films by Magnetron Sputter Epitaxy for SAW Applications

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Surface acoustic wave (SAW) technology offers a variety of applications from RF filters for mobile communication to biosensing. New fields, such as quantum acoustics are emerging as well. The key component in a SAW device is, of course, the medium through which the acoustic wave will travel. The mechanical, piezoelectric, and structural properties of the chosen material will affect the frequency, bandwidth, and quality factor of a SAW device. The wave is confined close to the surface, so due to lower production costs and easier manufacturing, thin piezoelectric films are widely used here. The emergence of aluminum scandium nitride (AlScN) in 2009 – a material with enhanced electromechanical coupling and piezoelectric properties – had a huge impact on recent thin-film based SAW research. AlScN is also CMOS compatible, high-temperature stable, and shares many other advantages of well-established parent material system AlN, making the transition to a new technology easier as well. In this presentation our recent AlScN material development efforts for going from textured to epitaxial to non-polar epitaxial thin films using magnetron sputtering epitaxy and the integration of AlScN into SAW resonators for RF applications will be discussed. The challenges as well as advantages of higher scandium concentrations in AlScN films will be addressed as well.