A Segmented‐Target Sputtering Process for Growth of Sub‐50 nm Ferroelectric Scandium–Aluminum–Nitride Films with Composition and Stress Tuning

Abstract

Harnessing the recently discovered ferroelectricity in scandium aluminum nitride (ScxAl1−xN) for the realization of integrated electronic and electromechanical devices requires a low‐temperature growth process that enables versatile control over film thickness, stoichiometric composition, and stress. Herein, a reactive magnetron sputtering process that enables extreme scaling of film thickness and tuning of composition and residual stress is reported on. Highly crystalline ScxAl1−xN films with thicknesses of over 25–250 nm with scandium concentrations of over 22–30 at% are sputtered using a segmented target created from scandium and aluminum tiles. The residual stress in the films is widely tuned from highly compressive to tensile using a pressure‐ and gas‐flow‐independent approach based on adjusting the electrical termination of the targets. The crystallinity, texture, and ferroelectric characteristics are measured for ScxAl1−xN films with different thicknesses, compositions, and residual stresses. The results highlight the consistent crystallinity and ferroelectric properties despite extreme thickness miniaturization to sub‐50 nm, and the large dependence of the coercive field on the residual stress and Sc concentration.