Towards an ideal high-κ HfO2–ZrO2-based dielectric

Nanoscale Pub Date: 2021-06-25 DOI: 10.1039/D1NR02272E

Abstract

The existence of a morphotropic phase boundary (MPB) inside HfO2–ZrO2 solid solution thin films has been predicted; if it exists, it provides a new path toward an ideal silicon-compatible dielectric. Herein, we investigate the structural evolution along with the dielectric and ferroelectric behaviors of differently designed HfO2–ZrO2 thin films to engineer the density of the MPB inside the film structure and consequently, enhance the dielectric properties. Polarization vs. electric field (P–E) measurements of Hf0.25Zr0.75O2 thin films reveal ferroelectric (FE)–antiferroelectric (AFE) characteristics. For this composition, the dielectric constant εr is higher than those of FE Hf0.5Zr0.5O2 and AFE ZrO2 thin films; the difference is attributed to the formation of the MPB. To increase the density of the MPB and subsequently the dielectric properties, 10 nm Hf0.5Zr0.5O2 (FE)/ZrO2 (AFE) nanolaminates were prepared with different lamina thicknesses tL. The coexistence of FE and AFE properties was confirmed by structural characterization studies and P–E measurements. The thinnest layered nanolaminate (tL = 6 ?) showed the strongest dielectric constant εr ～ 60 under a small signal ac electric field of ～50 kV cm?1; this is the highest εr so far observed in HfO2–ZrO2 thin films. This behavior was attributed to the formation of an MPB near FE/AFE interfaces. The new design provides a promising approach to achieve an ideal high-κ CMOS-compatible device for the current electronic industry.

Graphical abstract: Towards an ideal high-κ HfO2–ZrO2-based dielectric
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