Fields Shelby S, Smith Sean W, Ryan Philip J, Jaszewski Samantha T, Brummel Ian A, Salanova Alejandro, Esteves Giovanni, Wolfley Steve L, Henry Michael D, Davids Paul S, Ihlefeld Jon F
Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904, United States.
Sandia National Laboratories, Albuquerque, New Mexico 87185, United States.
ACS Appl Mater Interfaces. 2020 Jun 10;12(23):26577-26585. doi: 10.1021/acsami.0c03570. Epub 2020 May 29.
Ferroelectric hafnium zirconium oxide holds great promise for a broad spectrum of complementary metal-oxide-semiconductor (CMOS) compatible and scaled microelectronic applications, including memory, low-voltage transistors, and infrared sensors, among others. An outstanding challenge hindering the implementation of this material is polarization instability during field cycling. In this study, the nanoscale phenomena contributing to both polarization fatigue and wake-up are reported. Using synchrotron X-ray diffraction, the conversion of non-polar tetragonal and polar orthorhombic phases to a non-polar monoclinic phase while field cycling devices comprising noble metal contacts is observed. This phase exchange accompanies a diminishing ferroelectric remanent polarization and provides device-scale crystallographic evidence of phase exchange leading to ferroelectric fatigue in these structures. A reduction in the full width at half-maximum of the superimposed tetragonal (101) and orthorhombic (111) diffraction reflections is observed to accompany wake-up in structures comprising tantalum nitride and tungsten electrodes. Combined with polarization and relative permittivity measurements, the observed peak narrowing and a shift in position to lower angles is attributed, in part, to a phase exchange of the non-polar tetragonal to the polar orthorhombic phase during wake-up. These results provide insight into the role of electrodes in the performance of hafnium oxide-based ferroelectrics and mechanisms driving wake-up and fatigue, and demonstrate a non-destructive means to characterize the phase changes accompanying polarization instabilities.
铁电铪锆氧化物在包括存储器、低压晶体管和红外传感器等在内的广泛的与互补金属氧化物半导体（CMOS）兼容且可缩放的微电子应用中具有巨大潜力。阻碍这种材料应用的一个突出挑战是场循环期间的极化不稳定性。在本研究中，报告了导致极化疲劳和唤醒的纳米级现象。使用同步加速器X射线衍射，观察到在包含贵金属接触的场循环器件中，非极性四方相和极性正交相转变为非极性单斜相。这种相交换伴随着铁电剩余极化的减小，并为导致这些结构中铁电疲劳的相交换提供了器件尺度的晶体学证据。在包含氮化钽和钨电极的结构中，观察到在唤醒过程中叠加的四方相（101）和正交相（111）衍射反射的半高宽减小。结合极化和相对介电常数测量，观察到的峰变窄和位置向低角度的移动部分归因于唤醒过程中非极性四方相到极性正交相的相交换。这些结果深入了解了电极在基于铪氧化物的铁电体性能中的作用以及驱动唤醒和疲劳的机制，并展示了一种表征伴随极化不稳定性的相变的无损方法。
