Improved characteristics for MOHOS memory with oxygen-rich GdO as charge storage layer annealed by NH3

Characteristics of metal–oxide–high-k–oxide–silicon (MOHOS) memories with oxygen-rich or oxygen-deficient GdO as charge storage layer annealed by NH₃ or N₂ are investigated. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to analyze the cross-sectional quality, composition and crystallinity, respectively, of the stacked gate dielectric with a structure of Al/Al₂O₃/GdO/SiO₂/Si. The MOHOS capacitor with oxygen-rich GdO annealed in NH₃ exhibits a good trade-off among its memory properties: large memory window (4.8 V at ±12 V, 1 s), high programming speed (2.6 V at ±12 V/100 μs), good endurance and retention properties (window degradation of 5 % after 10⁵ program/erase cycles and charge loss of 18.6 % at 85 °C after 10 years, respectively) due to passivation of oxygen vacancies, generation of deep-level traps in the grain boundaries of the GdO layer and suppression of the interlayer between GdO and SiO₂ by the NH₃ annealing.