Predicting negative ion resputtering in thin films

Abstract

Negative-ion bombardment of a growing thin film can lead to changes in growth rate, surface morphology, and composition of the film through resputtering of the deposited material. A model was examined which predicts the probability of negative-ion formation based on ion potential and electron affinity values (I–EA) of the elements in the material being sputtered. It was found that I–EA values are but one of many factors influencing the amount and distribution of resputtering effects occurring. The model was found to be most useful in comparing isostructural materials resputtered under identical conditions. Since the resputtering is not uniform, and in some cases can lead to conical etch pits extending part way, or even completely, through the film to the substrate, their elimination will be a prime requirement for devices with bulk properties.