Origin of Ferroelectric Phase Stabilization via the Clamping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films
Origin of Ferroelectric Phase Stabilization via the Clamping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films
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DOI：
10.1002/aelm.202200601
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发表时间：
2022-08-03
影响因子：
6.2
通讯作者：
Ihlefeld, Jon F.
中科院分区：
文献类型：
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作者：
Fields, Shelby S.;Cai, Truong;Ihlefeld, Jon F.
在处理期间氧化铪基薄膜上的顶部电极的存在已被示出驱动亚稳铁电正交相的量和极化性能的增加。这种“箝位效应”，也被称为封盖效应或限制效应，归因于来自顶部电极层的机械应力和限制。然而，其他贡献的正交相稳定已被实验报道，这也可能受到影响的存在下的顶部电极。在这项研究中，它表明，在热处理过程中的顶部电极的存在下，在较大的拉伸双轴应力的大小和伴随的铁电相分数和极化响应的增加，而膜的化学，微观结构和结晶温度不受影响。通过蚀刻实验和测量的应力演化为每个处理步骤，它表明，顶部电极局部抑制在HZO的面外膨胀在结晶过程中，这防止了平衡单斜相的形成和稳定的正交相。这项研究提供了一个机械的理解铁电氧化铪基薄膜中的钳位效应和正交相的形成，这通知这些材料的未来设计，以最大限度地提高铁电相纯度和相应的极化行为。
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.