Oxygen vacancy distribution and phase composition in scaled, Hf0.5Zr0.5O2-based ferroelectric capacitors

Abstract

In this paper, we address correlations between film thickness, phase composition, and oxygen vacancy (VO) distribution in scaled, hafnia-based ferroelectric capacitors (FeCAPs), necessary to achieve low operating voltages, higher endurance, and advanced node integration. Using x-ray photoelectron spectroscopy, hard x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, and electrical characterization, we investigate the evolution of phase composition and VO profiles in Hf0.5Zr0.5O2 (HZO) films of 6 and 10 nm thickness. We demonstrate that thinner films exhibit a greater fraction of the non-polar tetragonal phase (t-phase), with increased VO concentration at the interface, affecting the device performance. Electrical measurements reveal contrasting wake-up and fatigue behavior between the two thicknesses, with thinner films showing decreased remanent polarization (2PR) due to t-phase dominance and VO redistribution during field cycling. These findings highlight the critical interplay of strain, phase stability, and VO dynamics, providing key insights for the optimization of HZO-based FeCAPs for advanced, low-power memory applications.