Oxygen Annealing Effects on Transport and Charging Characteristics of ${\rm Al\hbox {-}Ta}_{2}{\rm O}_{5}/{\rm SiO}_{x}{\rm N}_{y}\hbox {-}{\rm Si}$ Structure

Considering the influences of silicon (Si) surface potential and postannealing in oxygen ambient, a steady-state current model of Al-SiO_xN_y double structure was proposed. For Ta₂O₅ layer with different technological history, the dominated conduction mechanism for the as-deposited layer is Poole-Frenkel emission and Schottky emission for the annealed layer. The oxygen annealing treatment enhances the Schottky barrier height (φ_SB) of Al/Ta₂O₅ interface, i.e., the higher annealing temperature, the lower φ_SB, and leakage current. When the annealing temperature is, however, , the trap density starts to increase slightly because of the crystallization effect, which results in the decrease of φ_SB. Using the stationary J-V model and the stretched exponential law of transient current, the charging process in Ta₂O₅ layer can be described. Oxygen annealing lowers the density of trap charges (δ₀) and increases the decay time constant (τ). Because of the crystallization effect in the Ta₂O₅ layer annealed at temperature , τ decreases and δ₀ increases.