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

Abstract

In this letter, effects of top electrodes (TEs) on ferroelectric properties of Hf0.5 Zr0.5 O2 (HZO) thin films are examined systematically. The remnant polarization (Pr) of HZO thin films increases by altering TEs with lower thermal expansions coefficient ( $\alpha $ ). The largest 2Pr value of 38.72 $\mu \text{C}$ /cm2 is observed for W TE with $\alpha = 4.5\times 10^{\mathsf {-6}}$ /K, while the 2Pr value is only $22.83~\mu \text{C}$ /cm2 for Au TE with $\alpha = 14.2\times 10^{\mathsf {-6}}$ /K. Meanwhile, coercive field (Ec) 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). Ec 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 HfO2-based device performance for different requirements in actual application.