MRS Meetings and Events

 

EL20.11.03 2023 MRS Fall Meeting

Cryogenic Characterization of Polarization Switching in Ultra-Thin Ferroelectric Hf0.5 Zr0.5O2 Capacitors

When and Where

Nov 30, 2023
4:30pm - 4:45pm

Hynes, Level 3, Room 301

Presenter

Co-Author(s)

Balreen Saini1,Chanyoung Yoo2,Fei Huang1,John Baniecki2,Wilman Tsai1,Paul McIntyre1,2

Stanford University1,SLAC National Accelerator Laboratory2

Abstract

Balreen Saini1,Chanyoung Yoo2,Fei Huang1,John Baniecki2,Wilman Tsai1,Paul McIntyre1,2

Stanford University1,SLAC National Accelerator Laboratory2
The demand for smaller, faster, and more energy-efficient logic and memory devices is continuously increasing, leading to a heightened requirement for new materials that can be scaled down dimensionally and that are compatible with CMOS fabrication processes. A material system that shows promise for nonvolatile memory applications is HfO<sub>2</sub>-based ferroelectrics. Since the discovery of ferroelectricity in HfO<sub>2</sub> thin films, research in this area has surged due to their potential as nonvolatile memory elements in 1 transistor-1 capacitor ferroelectric random-access memory (FeRAM) and in ferroelectric field-effect transistors (FeFET). Many of these research efforts have focused on reducing the programming voltage, improving reliability at lower operating voltages, and, in some cases, achieving compatibility with back-end-of-line (BEOL) process temperatures. However, compared to traditional perovskite-based ferroelectrics, there is a less comprehensive understanding of the domain-switching mechanisms involved in programming the polarization of these fluorite-type ferroelectric materials.<br/>The metastable assembly of phases typically present in as-fabricated HfO<sub>2</sub>-based thin films exhibit a field-induced phase evolution at room temperature that can result in the increase (wake-up) or decrease (fatigue) of the remnant polarization with switching cycles. Other mechanisms such as domain depinning and charged defect redistribution with field cycling are also reported to cause the observed polarization evolution with field cycling (endurance). The extent to which various proposed mechanisms for polarization evolution can contribute to experimental observations will depend on their activation energies. In the present work, we explore the effect of measurement temperature on the functional properties of ferroelectric Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> (HZO) capacitors to further our understanding of the atomistic mechanisms responsible for the observed endurance characteristics. To carry out this investigation, we utilize a cryogenic probe station, which has the capability for measurements over a range of temperatures, as low as 10 K.<br/>We examine HZO capacitors with different thicknesses (ranging from 4 nm to 10 nm) with Mo and TiN electrodes. A decrease in remnant polarization is observed for all samples as the measurement temperature is decreased to 10 K. This polarization reduction is recovered by increasing the temperature back to room temperature, suggesting reduction in the thermally activated domain wall motion at low temperatures. Polarization hysteresis (P-V) measurements for capacitors with pristine state pinched loops at room temperature show a negligible pinching effect at cryogenic temperatures. A positive-up-negative-down (PUND) pulse scheme is utilized to separate the polarization switching current from the displacement current. Frequency-dependent and electric field-dependent endurance measurements are performed to further elucidate the possible contributions of different switching mechanisms to the observed temperature dependence of polarization switching.

Keywords

ferroelectricity

Symposium Organizers

Gina Adam, George Washington University
Sayani Majumdar, Tampere University
Radu Sporea, University of Surrey
Yiyang Li, University of Michigan

Symposium Support

Bronze
APL Machine Learning | AIP Publishing

Publishing Alliance

MRS publishes with Springer Nature