The Korean Society of Surface Science and Engineering

Al-Ag thin films with varying compositions were fabricated using a combinatorial sputtering system to develop highly sensitive SAW devices. The Al-Ag sample library exhibited a wide range of electrical resistivity and chemical compositions, providing valuable data for selecting optimal materials. Recognizing the significant influence of both resistivity and density of IDT electrodes on the generation of acoustic waves from piezoelectric materials, three types of Al-Ag thin films with different Al contents were fabricated, maintaining a consistent thickness of 150 nm. As the Al content decreased from 84.6 at% to 21.7 at%, the resistivity increased from 5.1 to 0.8 x 10-5 Ω-cm, while the calculated density increased from 3.9 to 8.8 g/cm3. The SAW devices fabricated with these Al-Ag IDT electrodes resonated at 71 MHz without frequency shifts, but the resonant frequency selectivity and insertion loss deteriorated with decreasing Al content, highlighting the predominant influence of electrode density over electrical conductivity on SAW device performance.

Keywords Combinatorial RF sputtering; Surface acoustic wave; Interdigital transducer; Aluminum-silver thin film