The reaction probability of XeF2 with silicon

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Abstract
The plasma etching of silicon has been simulated with experiments using atomic fluorine sources or with the dissociative adsorption of XeF2. Atomic fluorine is known to be the species responsible for etching silicon in a plasma, and it is reasonable to question whether XeF2 and atomic fluorine are equivalent reactants with silicon. One means to compare these two reactants is through their reaction probabilities to form SiF4 from a silicon surface. The reaction probability of XeF2 with silicon was measured in the same molecular beam apparatus used to measure the reaction probability of atomic fluorine with silicon. The value for XeF2 is between 1 and 3×10−3 under the conditions employed, and it is a factor of 10 lower than the value obtained for atomic fluorine. Examination of the products obtained from the reaction of XeF2 with silicon shows that there is a range in experimental conditions where the reaction probability is not a unique parameter. The values measured in this experiment represent a lower limit for the reaction probability of XeF2 with silicon. Reactions of XeF2 with silicon are effectively inhibited by a thin surface oxide which must be removed by ion bombardment. No significant differences in reactivity of XeF2 with either single crystal silicon or electron beam evaporated silicon were found.