Effects of Capping Electrode on Ferroelectric Properties of Hf0.5Zr0.5O2 Thin Films

• Published in: IEEE electron device letters 2018-08, Vol.39 (8), p.1207-1210
• Main Authors: Cao, Rongrong, Wang, Yan, Zhao, Shengjie, Yang, Yang, Zhao, Xiaolong, Wang, Wei, Zhang, Xumeng, Lv, Hangbing, Liu, Qi, Liu, Ming
• Format: Article
• Language: English
• Subjects: Annealing; Capacitors; capping electrode; Coercivity; Electric fields; Electrode polarization; Electrodes; Ferroelectric materials; ferroelectric properties; Ferroelectricity; Gold; Hafnium compounds; Hafnium oxide; Hf₀.₅Zr₀.₅O; Palladium; Platinum; Tantalum; Thermal expansion; Thin films; Tin
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2018.2846570

In this letter, effects of top electrodes (TEs) on ferroelectric properties of Hf 0.5 Zr 0.5 O 2 (HZO) thin films are examined systematically. The remnant polarization (P r ) of HZO thin films increases by altering TEs with lower thermal expansions coefficient ( \alpha ). The largest 2P r value of 38.72 \mu \text{C} /cm 2 is observed for W TE with \alpha = 4.5\times 10^{\mathsf {-6}} /K, while the 2P r value is only 22.83~\mu \text{C} /cm 2 for Au TE with \alpha = 14.2\times 10^{\mathsf {-6}} /K. Meanwhile, coercive field (E c ) shifts along the electric field axis and the offset is found to be dependent on the difference of workfunctions (WFs) between TE and TiN bottom electrode (BE). E c shifts toward negative/positive direction, when the WF of TE is larger/smaller (Pt, Pd, Au/W, Al, Ta) than TiN BE. This letter provides an effective way to modulate HfO 2 -based device performance for different requirements in actual application.