Combined effects of the deposition temperature and metal electrodes on ferroelectric properties of atomic-layer-deposited Hf_0.5Zr_0.5O₂ films

Abstract

The combined effects of the atomic-layer-deposition (ALD) temperature (220-280 °C) and metal electrodes (TiN and Mo) on the ferroelectric properties of Hf0.5Zr0.5O2 (HZO) films were studied. Regardless of the metal electrode, a tetragonal-orthorhombic-monoclinic phase evolution sequence was observed with increasing ALD temperature after post-metallization annealing. However, the phase transition temperature slightly changed depending on the metal electrode, which was predetermined based on the as-deposited states. Additionally, the out-of-plane orientation of the final orthorhombic grains was highly dependent on the crystallographic alignment of the metal electrode grains, resulting in different values of the maximum remanent polarization. In terms of long-term reliability, the fatigue characteristics were highly dependent on the electrode characteristics, and the wake-up characteristics were mainly affected by the initial phase distribution determined by both the ALD temperature and metal electrode.

Dimensional Scaling of Ferroelectric Properties of Hafnia-Zirconia Thin Films: Electrode Interface Effects

“…Typically, such ultrahigh polarization only appears in epitaxial films . It is reported that Mo electrodes can promote the formation of out-of-plane oriented FE-phase grains in HZO films . Therefore, it is possible that at the nanometer scale, we are measuring local highly textured domains that give ultrahigh polarization.…”

“…41 It is reported that Mo electrodes can promote the formation of out-of-plane oriented FE-phase grains in HZO films. 42 Therefore, it is possible that at the nanometer scale, we are measuring local highly textured domains that give ultrahigh polarization. To test this hypothesis, DPC measurements were performed on Mo capacitors with 4 nm thick HZO films having a CeO 2 interlayer (Figure 7 and Figure S12).…”