Effects of Post-Deposition Vacuum Annealing on the Piezoelectric Properties of AlScN Thin Films Sputtered on 200 Mm Production Wafers

Sc-doped AIN polycrystalline films are attractive active layers for high frequency (GHz range)acoustic resonators owing to the significant rise in the material piezoelectric activity with the increasing Sc content. AlScN films are sputtered on 200 mm Si wafers using configurable cathode containing a variable number of embedded Sc pellets which allows controlling both the Sc content in the films and the composition homogeneity across the wafer. The method is implemented in an Endeavor-AT™ cluster tool from OEM Group adapted for sputtering on 200 mm wafers. The piezoelectric activity of the as-deposited AlScN films appears to improve after a 15-minute post-deposition annealing at 600°C, leading to a 20% increase in the electromechanical coupling factor.