Thermal annealing of AlN films for piezoelectric applications

Aluminum nitride is an excellent electrical insulator and important piezoelectric material making it suitable for a wide range of applications in electronics and optoelectronics. However, to exhibit and preserve those piezoelectric properties, care has to be taken during manufacturing process. Indeed, the c-axis crystalline orientation of AlN is a necessary condition for piezoelectricity. Therefore, the goal of this paper is to compare AlN films grown on (100) silicon substrate by pulsed reactive DC sputtering at 400 degrees C on top of three different metallic underlayer electrodes (Ti/Pt, Cr/Pt, and AlN/Cr/Pt) by preserving the crystalline properties not only at room temperature but also at high temperatures. Among all deposited AlN films on top of the metallic underlayer electrode, only AlN/Cr/Pt has kept its crystallinity up to 950 degrees C.