Copper-catalyzed etching of silicon by F2: Kinetics and feature morphology

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Abstract
The copper‐catalyzed fluorination of silicon is first order in [F2] and in [Cu]s until the coverage reaches ∼4 monolayers. Above ∼4 monolayers the reaction rate is zero order in copper, suggesting a limited number of catalytically active Cu/Si sites. Copper islands form at high coverages, above saturation, and provide a reservoir of catalyst. The limited rate of surface diffusion of copper leads to anisotropic etching and feature size‐dependent etch depths. The copper compounds, CuF2 and CuO, and copper silicides, Cu5Si and Cu3Si, all catalyzed the F2‐Si reaction which suggests that they are all converted to the same active species. The results can be explained by mechanisms involving copper fluorides or copper silicides as active intermediates.