Dopant Engineered Y-Doped Hafnia-Zirconia Nanolaminates with 0.26 nm Equivalent Oxide Thickness for Dynamic Random Access Memory Capacitors

Abstract

Y-doped Hf0.5Zr0.5O2 demonstrated feasible field-induced ferroelectric properties for capacitor dielectrics in dynamic random access memory (DRAM) by stepwise cycling, which enabled low-voltage charge boosting. However, practical implementation remains limited by high cycling stress and leakage current density (J) degradation. This study reported a Y-doped ZrO2/HfO2/ZrO2 nanolaminate with middle-inserted and top-inserted Y2O3 layers, enabling low-voltage charge boosting with substantially decreased stepwise cycling stress. This effect arose from a more uniform distribution of oxygen-vacancy-dopant complexes, thereby decreasing the energy barrier for the tetragonal-to-polar orthorhombic phase transition. The middle-inserted Y2O3 layer underwent substitutional diffusion, stabilized the tetragonal phase and suppressed J by acceptor doping. In contrast, the top-inserted Y2O3 layer displayed limited bulk diffusion, resulting in minimal lattice strain and phase change, but further suppressed J. Consequently, a 5.2 nm-thick film achieved an ultralow equivalent oxide thickness of ∼0.26 nm while satisfying the DRAM J criterion (J < 10–7 A cm–2 at ±0.8 V), outperforming all previously reported DRAM dielectrics.