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

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 (Pr) of HZO thin films increases by altering TEs with lower thermal expansions coefficient (α). The largest 2P r value of 38.72 μC/cm 2 is observed for W TE with α = 4.5 × 10 -6 /K, while the 2P r value is only 22.83 μC/cm 2 for Au TE with α = 14.2 × 10 -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.