THE EFFECT OF FLUORINE ADDITIONS TO THE OXIDATION OF SILICON

Experiments were carried out to study the effects of fluorine additions to a dry oxidation ambient. Two distinct classes of fluorine sources, liquid dichlorofluoroethane (C2H3Cl2F), and gaseous nitrogen trifluoride (NF3), were investigated. We experimentally found that small fluorine additions (up to 0.11% by volume) caused large enhancements in oxidation kinetics. The oxidation kinetics data were analyzed by both the power of time and linear-parabolic models as a function of fluorine addition, temperature, and the type of fluorine additive. Thermodynamic calculations for these classes of fluorine sources were extensively carried out to determine the active oxidizing species that cause the significant enhancement of the oxidation. According to these calculations, the enhancement of oxidation could be explained by the presence of hydrogen fluoride (HF) and atomic fluorine (F). Secondary ion mass spectrometry (SIMS) was performed to study the incorporation behavior of fluorine into the oxide layer. C2H3Cl2F oxides displayed peaks at the silicon-oxide interface, while NF3 oxides exhibited flat fluorine profiles. © 1990, The Electrochemical Society, Inc. All rights reserved.