Fluorine in thermal oxides from HF preoxidation surface treatments

The effect of fluorine added into thermal oxides via preoxidation HF/water and anhydrous HF/methanol surface treatments was investigated. Under typica l conditions the resulting fluorine dose is in the range of 8 x 10(12) to 5 x 10(13) cm(-2), respectively. In ultrathin oxides fluorine appears to be, within the limits of secondary ion mass spectroscopy depth resolution, uni formly distributed in a very limited volume of the oxide. In the course of an extended oxidation fluorine remains preferentially at the SiO2/Si interf ace which leads to nonuniform distribution of fluorine in the oxide. The hi gher concentration of fluorine at the SiO2/Si interface causes slight retar dation of oxidation kinetics in the thick oxidation regime. No electrical c haracterization was carried out in this experiment, but it is postulated th at because of this pronounced difference in distribution fluorine may have a somewhat different effect on the electrical characteristics of ultrathin and thick oxides. (C) 1999 The Electrochemical Society. S1099-0062(99)01-07 1-8. All rights reserved.