Low-Field Ferroelectricity in 10 nm AlBScN Thin Films

TL;DR

This study demonstrates robust ferroelectric switching in 10 nm AlBScN thin films with low coercive fields and leakage currents, highlighting its potential for CMOS-compatible ferroelectric applications.

Contribution

It reveals ferroelectricity in ultrathin AlBScN films, a previously unexplored regime, with significantly reduced leakage and coercive fields compared to AlScN.

Findings

Ferroelectric switching observed at 2.2 MV/cm in 10 nm AlBScN capacitors.

Leakage current is approximately two orders of magnitude lower than in AlScN.

Weibull analysis shows a breakdown-to-coercive-field ratio of ~2.2.

Abstract

Ferroelectric aluminum scandium nitride (Al1-xScxN, AlScN) offers CMOS-compatible integration but suffers from high coercive fields and leakage currents that hinder thickness scaling. Further reduction in thickness is essential for low-voltage embedded nonvolatile memory applications. Boron incorporation into AlScN (AlBScN) suppresses leakage current in films down to 40 nm, yet its ferroelectric characteristics in ultrathin films remains unexplored. This letter demonstrates robust ferroelectric switching in 10 nm sputtered AlBScN capacitors with a low coercive field and approximately two orders of magnitude lower leakage than AlScN. Notably, ferroelectric switching was observed at 2.2 MV/cm in capacitance-voltage measurements, and symmetric polarization reversal occurred near 4.6 MV/cm in positive-up-negative-down (PUND) measurements using 2 {\mu}s pulses. Moreover, Weibull analysis revealed a breakdown-to-coercive-field ratio (EBD/Ec) of ~2.2. These findings demonstrated AlBScN as a promising candidate for CMOS back-end-of-line (BEOL) compatible ferroelectric applications with improved energy consumption and reduced leakage current.