Fluorine in Thermal Oxides from HF Preoxidation Surface Treatments

摘要

The effect of fluorine added into thermal oxidesvia preoxidation HF/water and anhydrous HF/methanol surfacetreatments was investigated. Under typical conditions theresulting fluorine does is in the range of 8×1012 to 5×1013cm-2,respectively. In ultra-thin oxides fluorine appears to be, withinthe limits of secondary ion mass spectroscopy depth resolution,uniformly distributed in a very limited volume of the oxide. Inthe course of an extended oxidation fluorine remainspreferentially at the SiO2/Si interface which leads to nonuniformdistribution of fluorine in the oxide. The higher concentration offluorine at the SiO2/Si interface causes slight retardation ofoxidation kinetics in the thick oxidation regime. No electricalcharacterization was carried out in this experiment, but it ispostulated that because of this pronounced difference indistribution fluorine may have a somewhat different effect on theelectrical characteristics of ultrathin and thick oxides.