Formation of Uniform Crystal and Reduction of Electrical Variation in HfZrO$_2$ Ferroelectric Memory by Thermal Engineering

TL;DR

This study demonstrates that extended thermal annealing improves the uniformity and reduces electrical variation in HfZrO$_2$ ferroelectric memory devices by promoting large, uniform ferroelectric domains, enhancing device reliability.

Contribution

It introduces a thermal engineering approach with extended annealing to control crystal formation and electrical variation in HfZrO$_2$ ferroelectric films, enabling more reliable memory devices.

Findings

Device variation in coercive voltage reduced from 0.4V to 0.01V.

Capacitance variation decreased from 2×10^{-5} to 4×10^{-6} nF/cm^2.

Large, uniform ferroelectric domains observed with extended annealing.

Abstract

In this paper we proclaim excellent variation control in Hf$_{0.5}$Zr$_{0.5}$O$_2$ based ferroelectric films obtained by germination of large ferroelectric domain via extended duration of thermal annealing. 10nm thick Hf$_{0.5}$Zr$_{0.5}$O$_2$ based ferroelectric capacitors with TiN as bottom and top electrodes are fabricated and characterized. The duration of rapid thermal annealing (RTA) is varied to observe its effect on crystal formation and device electrical properties at 700C. The device to device variation in terms of coercive voltage and peak capacitance are reduced from 0.4V to 0.01V and from 2*$10^{-5}$nF/cm$^2$ to 4*$10^{-6}$nF/cm$^2$, respectively, by increasing the RTA duration. High resolution transmission electron micrograph clearly shows large and uniform ferroelectric domains with RTA of 180 seconds. Extended duration of RTA likely allows uniform crystal to form, which mitigates the stochasticity of the distribution of ferroelectric and paraelectric domains, and deterministic switching has been infused. This improvement paves the way for implementing Hf$_{0.5}$Zr$_{0.5}$O$_2$ based deeply scaled devices for memory and steep slope device applications.