Oxygen-Atom Incorporated Ferroelectric AlScN Capacitors for Multi-Level Operation

• Published in: IEEE electron device letters 2024-11, Vol.45 (11), p.2090-2093
• Main Authors: Chen, Si-Meng, Nishida, Hirofumi, Tsai, Sung-Lin, Hoshii, Takuya, Tsutsui, Kazuo, Wakabayashi, Hitoshi, Yi Chang, Edward, Kakushima, Kuniyuki
• Format: Article
• Language: English
• Subjects: Capacitors; Coercivity; Electric fields; Electrodes; endurance cycle; Ferroelectric AlScN; Ferroelectric materials; Ferroelectricity; Lattices; Leakage current; multi-level operation; Oxygen; Oxygen content; Polarization; Sputtering; Switches; Thick films; X-ray scattering
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2024.3453111

The effect of oxygen-atom incorporation in 50-nm-thick ferroelectric Al0.89Sc0.11N films was investigated. The fabricated films exhibited a high remanent polarization ( {P}_{\text {r}}) exceeding 100~\mu C/cm2, irrespective of the oxygen content studied. An increase in oxygen content led to a decrease in coercive field ( {E}_{\text {c}}) from 5.2 to 4.4 MV/cm and an increase in the static dielectric constant ( \varepsilon _{\text {i}}) from 15 to 19. This was likely due to the formation of substitute O and Al vacancy complex defects to ease N-atom displacement. Additionally, higher oxygen content resulted in imprint effect elimination, leakage current reduction, and breakdown field ( {E}_{\text {BD}}) enhancement, which are beneficial for ferroelectric memory applications. The gentle and linear relationship between {P}_{\text {r}} and the electric field ( {E}) enabled precise control of partial polarization switching, supporting multi-level operation. Although issues related to fatigue and endurance cycles remain to be addressed, the high {P}_{\text {r}} and potential for multi-level operation are suitable for crossbar-based analog in-memory computing.