Thickness Dependence of Furnace N_2O-Oxynitridation Effects on Breakdown of Thermal Oxides

概要

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Thickness dependence of breakdown properties in control and N_2O-oxynitrided oxides was investigated. Nitrogen atoms piled up at the Si/SiO_2 interface increase charge-to-breakdown (Q_ltBDgt) under substrate injection conditions for oxide thickness below 10 nm, while no meaningful improvement is observed above 10 nm. This thickness dependence is explained by the fact that N_2O-oxynitridation reduces oxide defects near the Si/SiO_2 interface. N_2O-oxynitridation of the oxides reduces the number of neutral electron traps due to the chemical reaction of oxide defect with nitrogen atoms. Electron trapping of N_2O-oxynitrided oxides is significantly suppressed ; the reduction of electron trapping events into neutral electron traps increases Q_ltBDgt under substrate injection. On the other hand, under gate injection, N_2O-oxynitrided oxides show low rate of hole trapping during the initial stress period. However, in heavily injected condition, electron trapping is not suppressed, resulting in little improvement of Q_ltBDgt. In addition, the control and N_2O-oxynitrided oxides show quite similar dependence of Q_ltBDgt on stress current density, which is related primarily to the carrier transport phenomena (tunneling, traveling, impact ionization and hole injection).
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1995-03-25