Method of controlling coupling coefficient of Aluminum Scandium Nitride deposition in high volume production

In this paper, we present our studies of the influence of the stress on Aluminum Nitride containing various concentrations Scandium (Sc). Coupling coefficient (kt2) was measured across the wafer and wafer to wafer as a function of stress and Sc content of the film. Previous studies demonstrate a considerable increase in kt2 as a function of Sc content of the film [1], [2], [4], [5]. Unfortunately, when deposited on 200 mm wafers we observed that coupling coefficient varies significantly more than that of a standard Aluminum Nitride (AlN). Both stress and concentration of Sc must be controlled across the wafer to achieve uniform coupling coefficient acceptable for production of Bulk Acoustic Resonator (BAW) devices [3], [6], [7]. We were able to control coupling coefficient across the wafer and wafer-to-wafer by adjusting magnetic fields in dual magnetron configuration as well as adjusting concentration of Sc in our two sputtering targets.