Aluminum scandium nitride thin-film bulk acoustic resonators for wide band applications

Piezoelectric c-textured Al(1−x)ScxN thin films, where the Sc relative concentration, x, varies in the range 0–0.15 have been studied in view of radio frequency (RF) electro-acoustic applications. Thin film bulk acoustic wave resonators (FBARs) employing these films were fabricated and characterized as a function of the Sc concentration for the first time. The measured electromechanical coupling is found to increase by as much as 100% in the above concentration range. The results from this work underline the potential of the c-textured Al(1−x)ScxN based FBARs for wide band RF applications.

► Thin film bulk acoustic resonators (FBAR) employing highly c-textured Al(1−x)ScxN thin films are found promising for radio frequency (RF) band applications.
► Electromechanical coupling increases by factor of two for relative Sc concentration up to 20%.
► Resonator figure of merit exhibit a maximum at relative Sc concentration of 9%.
► Accordingly wide bandwidth RF filters with low losses and steep skirts can be build using this technology.