Structure of SiO2 Films Grown at Low Temperature by Inductively Coupled Plasma Oxidation with Oxygen Gas

Abstract

The structure of silicon oxide films grown in inductively coupled plasma (ICP) with oxygen gas at temperatures ranging from 350 to 450 degrees C was studied. The thickness of the oxide ranged from 10 to 40 nm. A FTIR spectroscopy showed that the Si-O-Si bond angle was smaller than that in the high-temperature thermal oxide. The bond angle decreased as the oxide thickness decreased. An X-ray reflectivity analysis showed that the density of the ICP oxide (2.23 g/cm(3)) was larger than that of thermal oxide (2.20 g/cm(3)) grown at 900 degrees C. The accumulation of compressive stress could be the cause of small bond angles and the high density in the ICP oxide. A very thin surface layer with a lower density was also detected on the as-grown ICP oxide. The ICP oxide showed a high etch rate and low refractive index as the oxide thickness decreased, indicating that these chemical and physical properties were strongly affected by the magnitude of the Si-O-Si bond angle.