Tailoring ferroelectricity in Al:HfO2 capacitors: A comprehensive approach to annealing, electrode selection, and Al dopant distribution
Year: 2025
Type: article
Abstract: We systematically investigate the effects of annealing conditions, Al2O3 atomic layer deposition (ALD) cycle number and distribution, and top electrode (TE) material on the ferroelectric switching behavior of 10 nm-thick Al-doped HfO2 (Al:HfO2) films. We perform 150 ALD cycles, comprising HfO2 and Al2O3 sub-cycles, with precise control over the number and distribution of Al2O3 cycles. Post-metallization annealing (PMA) at 600 °C for 3 min induced spontaneous 2 remnant polarization (2Pr) through the combined Al-induced lattice stress and TE-induced mechanical stress, promoting orthorhombic phase formation. Optimization to three Al2O3 cycles within the HfO2 bulk balances polarization enhancement and suppression of oxygen-vacancy-induced leakage, yielding a 2Pr = 3 μC/cm2 and endurance up to 106 cycles. The W electrodes, with a low thermal expansion coefficient and smooth surfaces, enable uniform stress transfer and improved dipole alignment compared to Mo and Ru electrodes. Notably, asymmetric localization of Al2O3 sub-cycles near the lower HfO2 region, combined with TE-induced stress, maximizes uniform stress distribution across the film. As confirmed by positive-up-negative-down measurements, this mechanism activates a higher dipole density and achieves the highest 2Pr = ∼9 μC/cm2 without additional leakage. These findings demonstrate that jointly optimizing thermal treatment, dopant engineering, and electrode selection enhances phase stability and dipole activity in HfO2-based ferroelectrics.
Source: APL Energy
DOI: 10.1063/5.0296777
Authors: Hyoungjin Park, Jiae Jeong, Eunjin Kim, Jiyong Woo
Institution: Kyungpook National University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: diamond
Awards: G1294760279, G1846293536, G667371499
OpenAlex ID: W4415994731