Precipitate Formation and Effects on Electrical and Mechanical Properties of Fluorinated Silicon Oxide

Abstract

Precipitates appear on fluorine-doped silicon oxide (SiOF) film when the film surface is exposed to atmospheric air. They are flake-type and hexagonal-shaped and show up rapidly after initiation, and then densely clustered. Energy-dispersive X-ray (EDX) analysis results of the precipitates show that mainly Si & O are detected. From the analysis of Raman spectra, the decreased intensities at about 600 cm-1 and 500 cm-1 post precipitation indicates the reduction of strained low-order ring structure in SiOF film. It is found that the dielectric constant of SiOF films initially increases at exposure to air and is attributable to the absorption of water, and then on the contrary a declining trend of the dielectric constant was observed after precipitation. From the Current-Voltage (I-V) characteristics, there is an apparent shift of the breakdown distribution to lower values of electric field for the SiOF films post-precipitation. Slight but appreciable reduction in hardness could be observed along exposure to air and precipitation. Precipitation on SiOF film at exposure to humid air is accompanied by reconstruction in structure, leading to further increase in film porosity and reduction in film rigidity.