Ferroelectric AlScN thin films with enhanced polarization and low leakage enabled by high-power impulse magnetron sputtering

TL;DR

This paper presents a novel high-power impulse magnetron sputtering method to produce high-quality ferroelectric AlScN thin films with enhanced polarization, low leakage, and stability, suitable for memory devices.

Contribution

It introduces a scalable, CMOS-compatible synthesis approach using HiPIMS that improves ferroelectric properties of AlScN films compared to traditional methods.

Findings

Films exhibit high texture and crystallinity at low temperatures.

Remanent polarization is significantly enhanced and stable across scandium concentrations.

Films show low leakage currents and good cycling stability.

Abstract

The demand for efficient data processing motivates a shift toward in-memory computing architectures. Ferroelectric materials, particularly AlScN, show great promise for next-generation memory devices. However, their widespread application is limited due challenges such as high coercive fields, leakage currents and limited stability. Our work introduces a novel synthesis approach for ferroelectric AlScN thin films using high-power impulse magnetron sputtering (HiPIMS). Through a combinatorial study, we investigate the effect of scandium content and substrate bias on the ferroelectric properties of AlScN films deposited using metal-ion synchronized (MIS) HiPIMS. Leveraging the high ionization rates of HiPIMS and optimally timed substrate bias potentials, we enhance the adatom mobility at low temperatures. Our films exhibit a high degree of texture and crystallinity as well as low roughness at temperatures as low as 250{\deg}C. Most importantly, the films exhibit coercive fields comparable to state-of-the-art values (5 MV/cm) with significantly enhanced remanent polarization (158-172.0 {\mu}C/cm2). Notably, the remanent polarization remains stable across varying scandium concentrations. We further evaluate cycling stability and leakage current to assess suitability for memory applications. This study demonstrates HiPIMS as a scalable and CMOS compatible technique for synthesizing high-quality ferroelectric AlScN films, paving the way for their application in non-volatile memory applications.