Stoichiometry- and lattice-tunable MoN_x as a novel electrode platform for ferroelectric Hf_0.5Zr_0.5O₂ capacitors

Abstract

Ferroelectricity in (Hf,Zr)O₂ thin films is highly sensitive to bottom-electrode chemistry, as interfacial redox reactions during atomic layer deposition (ALD) and subsequent annealing can generate defective interlayers and alter oxygen-vacancy distributions. Here, we propose a stoichiometry- and lattice-tunable molybdenum nitride (MoN_x) electrode platform that enables single-layer interfacial engineering through control of the Mo:N ratio. MoN_x films with x = 0.00, 0.05, 0.52, and 0.79 (denoted as Mo, 05MoN, 52MoN, and 79MoN) were sputter-deposited and integrated into symmetric MoN_x/Hf_0.5Zr_0.5O₂/MoN_x capacitors containing 8 nm-thick ALD Hf_0.5Zr_0.5O₂. Structural analysis confirms a transition from Mo (110)-textured films to rock-salt-type MoN_x with a (111) texture at higher N contents, while electrode-grade resistivity is maintained (≤ 200 μΩ∙cm for 52MoN). Chemical analyses reveal that increasing the N content substantially suppresses ALD-induced electrode oxidation and reduce the thickness of the oxidized interfacial-layer by 47.7% for 52MoN relative to Mo; N incorporation into the Hf_0.5Zr_0.5O₂ (HZO) near the bottom interface is also detected. Consistently, the monoclinic phase fraction decreases from ~ 21% for Mo to < 5% for 52MoN and 79MoN. All capacitors exhibit minimal wake-up, with a ≤ 3.0% change in double remanent polarization after 10⁴ cycles at 3 MV∙cm^-1. Benchmarking against other stoichiometry-controlled electrode systems (e.g., TaN_x, RuO_x, and TiN_x) shows that the MoN_x platform maintains high pristine polarization (> 47.5 μC∙cm^-2) while suppressing wake-up across a wide compositional range. Endurance improves markedly with N content, reaching ~ 10⁸-10⁹ cycles for high-N MoN_x electrodes, depending on the cycling voltage. These results establish MoN_x as a scalable, composition-engineerable electrode system that couples interfacial microstructure control with enhanced ferroelectric reliability in HZO thin films.

Keywords

Ferroelectric Hf_0.5Zr_0.5O₂ / molybdenum nitride / interface engineering / wake-up effect / cycling endurance / oxidation resistance

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