Title: Electrode Effects on Ferroelectric Properties of Hf1-xZrxO2 Thin Films
Abstract: Following the first reports of ferroelectric properties in 2011, HfO2-based thin films have undergone significant research and development for negative differential capacitance field effect transistor (NC-FET), ferroelectric FET (FE-FET), and ferroelectric random-access memory (Fe‑RAM) applications. Hafnia-based ferroelectrics are particularly attractive for integration into complementary metal oxide semiconductor (CMOS) technology owing to their scalability, silicon compatibility, and straightforward processing with mature atomic layer deposition (ALD) processes. The ferroelectric properties have been associated with a metastable Pca21 orthorhombic phase, which persists in small crystallite size over the bulk, room temperature, linear dielectric monoclinic phase. Stability of this phase has been observed to be enhanced through doping with ZrO2 (Hf1-xZrxO2, HZO) through a broad composition window (0.2 ≤ x ≤ 0.8). Hindering implementation of this novel ferroelectric material into contemporary CMOS device platforms is the change in measured polarization with field cycling through processes labeled wake-up and fatigue. These processes reportedly occur due to the rearrangement of oxygen vacancies, which have been suggested to both stabilize the orthorhombic phase and produce/relieve internal biases within the ferroelectric layer. Different polarization behaviors have been observed with the incorporation of different electrode materials, which have been suggested to be due to the differing resulting effects on oxygen vacancy concentrations and biaxial stresses imparted to the hafnia-based films. In this proposed work, the chemical and physical characteristics of different noble metal, binary nitride, and conductive oxide electrode materials are investigated with respect to their impact on wake-up and fatigue processes in hafnium zirconium oxide thin films. Through understanding the role of electrodes on material performance, advanced devices may be produced that are free from polarization instabilities.
https://virginia.zoom.us/j/99240321105; Meeting ID: 992 4032 1105
Stephen McDonnell, MSE. Chair
Jon Ihlefeld, MSE, Advisor
Patrick Hopkins, MAE
Nikhil Shukla, ECE
Sean Smith, Sandia National Labs