Deep etching of silicon with XeF2 gas

This paper presents results of [100] silicon etching using XeF₂ gas. Two phenomena, trenching and loading, were observed in the shape of etch profiles. Trenching refers to deeper etching at the side of an etch feature with respect to the middle of the feature. Loading is the reduction in etch depth that adjacent etched regions have on their respective etch profiles. These two phenomena could especially be recognized at locations where the substrate was etched through large mask openings (>200 μm). A theory explaining these phenomena is developed, and the etching process is simulated in software. The results are compared to several etched samples with varying mask aperture size and etch depth. Good agreement was found between the simulated profiles and the actual measured etch profiles at the mean free path of XeF₂ etching pressures.