Ferroelectric Aluminum-Scandium Nitride by Plasma-Enhanced Atomic Layer Deposition under Ultrahigh Purity Conditions

We demonstrate a plasma-enhanced atomic layer deposition (PEALD) process for Aluminum-scandium nitride [Al _(1-x) Sc _x N] thin films using a super-cycle dose sequence consisting of AlN and ScN constituent nitride processes. The process utilized trimethylaluminum (TMA), bis(ethylcyclopentadienyl) scandium chloride (ClSc(EtCp) ₂ ) and N ₂ H ₂ plasma as co-precursors, with substrate temperatures ranging from 215 °C–300 °C. A 60.3 nm-thick PEALD Al _0.88 Sc _0.12 N thin film grown on {111}-oriented platinum bottom electrodes on Si (100) exhibited definitive ferroelectric switching. The Al _0.88 Sc _0.12 N film grown on a {111}-oriented platinum bottom electrode was entirely c-axis (0002) oriented out-of-plane and had a rocking curve full-width-half-max (FWHM) of 3.42°. PEALD Al _0.88 Sc _0.12 N grown on a lattice-matched GaN on c-plane sapphire substrate was epitaxial-like with both in-plane and out-of-plane orientations. Cross-sectional images of the Al _(1-x) Sc _x N thin films across via and trench structures with a 273 nm-wide openings demonstrate the 3D conformal coating capability of the PEALD process.