Towards Realizing the Low-Coercive Field Operation of Sputtered Ferroelectric ScxAl1-xN

Abstract

In this paper, we map the ferroelectric properties of 22% and 30% scandium-doped aluminum nitride (ScAlN) thin films with the goal to engineer low coercive fields for low-voltage post-CMOS compatible RF frontends. ScAlN films, 200 nm and 300 nm thick, were deposited on platinum and molybdenum electrodes. Lateral and vertical capacitors were tested across various electric field strengths, frequencies, and electrode sizes. Measured coercive field and remnant polarization values were between 3.9-6.2 MV/cm and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$58-170\ \mu \mathrm{C}/\text{cm}^{2}$</tex> . Frequency and device area-dependence were studied to identify trends towards low coercive fields. A comparison of lateral and vertical capacitors on the same ScAlN films shows the impact of charge-traps due to current-crowding in lateral devices. Finally, an anomalous observation relating doping concentration and film stress with coercive field and remnant polarization is reported to present the potential for decoupled tuning knobs for ferroelectric engineering properties ScAlN.