AVS 66th International Symposium & Exhibition
    Thin Films Division Tuesday Sessions
       Session TF-TuA

Paper TF-TuA11
Ferroelectricity in Hafnia-Zirconia based Thin Films: Characterization and Applications

Tuesday, October 22, 2019, 5:40 pm, Room A122-123

Session: Emerging Applications for Thin Films
Presenter: Vineetha Mukundan, SUNY Polytechnic Institute
Authors: V. Mukundan, SUNY Polytechnic Institute
S. Consiglio, TEL Technology Center, America, LLC
D.H. Triyoso, TEL Technology Center, America, LLC
K. Tapily, TEL Technology Center, America, LLC
R.D. Clark, TEL Technology Center, America, LLC
G.J. Leusink, TEL Technology Center, America, LLC
J.H. Hazra, SUNY Polytechnic Institute, Albany
K. Beckmann, SUNY Polytechnic Institute, Albany
N.C. Cady, SUNY Polytechnic Institute, Albany
A.C. Diebold, SUNY Polytechnic Institute, Albany
Correspondent: Click to Email
Hafnia-based materials have tremendous potential to replace perovskites in FeRAM applications due to their unique ferroelectric properties and potential for scalability [1]. Implementation of hafnia-based thin films in FeRAM has recently been demonstrated by Mikalojick et al [1]. With hafnia’s high coercive field, enhanced endurance and memory window achieved by encapsulation with different electrodes, it is advantageous to also integrate it into a FET device [2]. For use in neuromorphic computing, Jerry et al.have employed electric-field controlled partial polarization switching in atomic layer deposited ferroelectric hafnia-zirconia films to demonstrate a FeFET based analog synapse [3]. Ferroelectricity in hafnia doped with Si was recently discovered by Böscke et al [4] and it has been well established that the orthorhombic Pca21 is responsible for its ferroelectric properties. The factors leading to the formation and stabilization of this metastable phase are unclear. Structural modification and stabilization of different metastable states are being investigated by alloying hafnia with ZrO2, doping with Si and Al, various annealing schemes and different processing schemes including different semiconductor substrates. We study the long range structure of hafnia-zirconia films by grazing incidence in-plane x-ray diffraction (GI-I-XRD) and local structure by extended x-ray absorption fine structure spectroscopy (EXAFS) along with polarization measurements to study their electrical properties. An important part for advancing these ultra-thin films for application as both FeRAM and NCFET devices necessitates studying capacitive stacks in the form of metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) [5]. Further, we estimate the percentage content of the different phases including the non-centrosymmetric orthorhombic phases in these stacks varying in composition and thickness. With increasing zirconia content in these stacks, the monoclinic phase decreases and it exhibits anti-ferroelectric property. With increasing thicknesses, it is found that the monoclinic phase increases in content, which should give rise to a decrease in the polarization of these stacks. We observed no change in the structure with annealing after it has been encapsulated by the TiN electrode, even up to 1000°C suggesting the confinement plays an active role in its structural evolution. Additional studies are underway to understand the influence of processing conditions, electrical cycling, annealing temperature, types of electrodes, and substrates on the structure and electrical properties of Hafnia-zirconia based thin films [6].