Origin of Ferroelectric Phase Stabilization via the Clamping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films

Shelby S. Fields; Truong Cai; Samantha T. Jaszewski; Alejandro Salanova; Takanori Mimura; Helge H. Heinrich; Michael David Henry; Kyle P. Kelley; Brian W. Sheldon; Jon F. Ihlefeld

doi:10.1002/aelm.202200601

Origin of Ferroelectric Phase Stabilization via the Clamping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films

Shelby S. Fields, Truong Cai, Samantha T. Jaszewski, Alejandro Salanova, Takanori Mimura, Helge H. Heinrich, Michael David Henry, Kyle P. Kelley, Brian W. Sheldon, Jon F. Ihlefeld

Functional Atomic Force Microscopy Group

Research output: Contribution to journal › Article › peer-review

40 Scopus citations

Abstract

The presence of the top electrode on hafnium oxide-based thin films during processing has been shown to drive an increase in the amount of metastable ferroelectric orthorhombic phase and polarization performance. This “Clamping Effect,” also referred to as the Capping or Confinement Effect, is attributed to the mechanical stress and confinement from the top electrode layer. However, other contributions to orthorhombic phase stabilization have been experimentally reported, which may also be affected by the presence of a top electrode. In this study, it is shown that the presence of the top electrode during thermal processing results in larger tensile biaxial stress magnitudes and concomitant increases in ferroelectric phase fraction and polarization response, whereas film chemistry, microstructure, and crystallization temperature are not affected. Through etching experiments and measurement of stress evolution for each processing step, it is shown that the top electrode locally inhibits out-of-plane expansion in the HZO during crystallization, which prevents equilibrium monoclinic phase formation and stabilizes the orthorhombic phase. This study provides a mechanistic understanding of the clamping effect and orthorhombic phase formation in ferroelectric hafnium oxide-based thin films, which informs the future design of these materials to maximize ferroelectric phase purity and corresponding polarization behavior.

Original language	English
Article number	2200601
Journal	Advanced Electronic Materials
Volume	8
Issue number	12
DOIs	https://doi.org/10.1002/aelm.202200601
State	Published - Dec 2022

Funding

Initial HZO and TaN thin film synthesis, HTXRD, and ex situ wafer flexure measurements were supported by the Semiconductor Research Corporation's (SRC) Global Research Collaboration Program under task 2875.001. HZO film preparation, reactive ion etching, and atomic force microscopy measurements were supported by the Center for 3D Ferroelectric Microelectronics (3DFeM), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE‐SC0021118. HT‐MOSS measurements were supported by the National Science Foundation, under Award DMR‐1832829. This research utilized a PHI VersaProbe III XPS system, which was supported by National Science Foundation Major Research Instrumentation Award #162601. This research utilized a Bruker D8 Diffractometer, which was supported by the National Science Foundation Award CHE‐2018870. S.T.J. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under award DGE‐1842490. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE‐NA0003525. AFM experiments were conducted as part of a user project at the Center for Nanophase Materials Sciences, which is a US Department of Energy User Facility at Oak Ridge National Laboratory. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Initial HZO and TaN thin film synthesis, HTXRD, and ex situ wafer flexure measurements were supported by the Semiconductor Research Corporation's (SRC) Global Research Collaboration Program under task 2875.001. HZO film preparation, reactive ion etching, and atomic force microscopy measurements were supported by the Center for 3D Ferroelectric Microelectronics (3DFeM), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0021118. HT-MOSS measurements were supported by the National Science Foundation, under Award DMR-1832829. This research utilized a PHI VersaProbe III XPS system, which was supported by National Science Foundation Major Research Instrumentation Award #162601. This research utilized a Bruker D8 Diffractometer, which was supported by the National Science Foundation Award CHE-2018870. S.T.J. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under award DGE-1842490. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. AFM experiments were conducted as part of a user project at the Center for Nanophase Materials Sciences, which is a US Department of Energy User Facility at Oak Ridge National Laboratory. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Funders	Funder number
center for 3D Ferroelectric Microelectronics
National Science Foundation	DMR‐1832829, 162601, DGE‐1842490, CHE‐2018870
U.S. Department of Energy
Semiconductor Research Corporation
Office of Science
Basic Energy Sciences	DE‐SC0021118
National Nuclear Security Administration	DE‐NA0003525
Oak Ridge National Laboratory

Keywords

biaxial stress
clamping effect
diffraction
ferroelectrics
hafnium zirconium oxide

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10.1002/aelm.202200601

Cite this

Fields, S. S., Cai, T., Jaszewski, S. T., Salanova, A., Mimura, T., Heinrich, H. H., Henry, M. D., Kelley, K. P., Sheldon, B. W., & Ihlefeld, J. F. (2022). Origin of Ferroelectric Phase Stabilization via the Clamping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films. Advanced Electronic Materials, 8(12), Article 2200601. https://doi.org/10.1002/aelm.202200601

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abstract = "The presence of the top electrode on hafnium oxide-based thin films during processing has been shown to drive an increase in the amount of metastable ferroelectric orthorhombic phase and polarization performance. This “Clamping Effect,” also referred to as the Capping or Confinement Effect, is attributed to the mechanical stress and confinement from the top electrode layer. However, other contributions to orthorhombic phase stabilization have been experimentally reported, which may also be affected by the presence of a top electrode. In this study, it is shown that the presence of the top electrode during thermal processing results in larger tensile biaxial stress magnitudes and concomitant increases in ferroelectric phase fraction and polarization response, whereas film chemistry, microstructure, and crystallization temperature are not affected. Through etching experiments and measurement of stress evolution for each processing step, it is shown that the top electrode locally inhibits out-of-plane expansion in the HZO during crystallization, which prevents equilibrium monoclinic phase formation and stabilizes the orthorhombic phase. This study provides a mechanistic understanding of the clamping effect and orthorhombic phase formation in ferroelectric hafnium oxide-based thin films, which informs the future design of these materials to maximize ferroelectric phase purity and corresponding polarization behavior.",

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AB - The presence of the top electrode on hafnium oxide-based thin films during processing has been shown to drive an increase in the amount of metastable ferroelectric orthorhombic phase and polarization performance. This “Clamping Effect,” also referred to as the Capping or Confinement Effect, is attributed to the mechanical stress and confinement from the top electrode layer. However, other contributions to orthorhombic phase stabilization have been experimentally reported, which may also be affected by the presence of a top electrode. In this study, it is shown that the presence of the top electrode during thermal processing results in larger tensile biaxial stress magnitudes and concomitant increases in ferroelectric phase fraction and polarization response, whereas film chemistry, microstructure, and crystallization temperature are not affected. Through etching experiments and measurement of stress evolution for each processing step, it is shown that the top electrode locally inhibits out-of-plane expansion in the HZO during crystallization, which prevents equilibrium monoclinic phase formation and stabilizes the orthorhombic phase. This study provides a mechanistic understanding of the clamping effect and orthorhombic phase formation in ferroelectric hafnium oxide-based thin films, which informs the future design of these materials to maximize ferroelectric phase purity and corresponding polarization behavior.

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Origin of Ferroelectric Phase Stabilization via the Clamping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films

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Keywords

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