Impact of Stoichiometric Optimization on Performance and Reliability of Zirconium Doped Hafnium-Based Ferroelectric Capacitors

Fluorite ferroelectrics such as Zirconium doped Hafnium Oxide (HZO) is a promising candidate for next generation high density embedded memory technology due to its high dielectric constant, excellent ferroelectric properties, scalability and compatibility with CMOS technology [1]. Understanding how to optimize the stoichiometric composition in such multi-cation system is extremely crucial for co-optimizing the performance and reliability of the memory device. Prior works on composition optimization primarily focused on stabilizing the morphotropic phase boundary (MPB) for obtaining high dielectric constant and remnant polarization [2–5]. However, understanding the impact of such composition optimization on the reliability of the device remains large unexplored. Moreover, the key performance and reliability metrics must be studied at elevated temperatures between $85^{\circ} \mathrm{C}$ and $105^{\circ} \mathrm{C}$ and post hydrogen treatments to ensure suitability for back-end-of-line (BEOL) compatible embedded memory. In this work, we present a comprehensive investigation of the impact of stochiometric composition (by varying the ratio of Hafnium Hf to Zirconium Zr) in metal-ferroelectric-metal (MFM) capacitors. We evaluate the performance and reliability metrices at various elevated temperatures up to $105^{\circ} \mathrm{C}$ and post forming gas annealing (FGA) to study hydrogen resiliency. Our experimental results indicate that Hf<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</inf>Zr<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> MFM capacitors with a composition of $\mathrm{Hf}(60): \mathrm{Zr}(40)$ offer the optimal balance between performance and reliability, making it a promising candidate for BEOL embedded memory.