Fundamental electrical properties of fluorinated and N2O plasma-annealed ultrathin silicon oxides grown by microwave plasma afterglow oxidation at low temperatures

Abstract

A technique for growing ultrathin silicon oxides of superior quality at low temperatures is indispensable for future submicron device applications. Fundamental characteristics such as the oxide breakdown fields, oxide charges, and interface-state densities of various ultrathin silicon oxides (≤8 nm) grown by microwave plasma afterglow oxidation at low temperatures (400 and 600 °C) were investigated. Fluorination (HF soaking) and low-temperature N2O plasma annealing were employed to improve the properties of the oxides. The breakdown fields of the as-grown silicon oxides were enhanced and the interface-state densities were reduced. The effect of N2O annealing time on the interface-state density was also investigated. A longer annealing time (≳1 h) was required to reduce the interface-state density. The effective oxide charge density of 600 °C as-grown oxide was as low as 6×1010 cm−2. Additionally, the breakdown field of the thin silicon oxide grown at 600 °C with 15 min N2O plasma annealing was 12 MV/cm.