Abstract
First-principles quantum chemical techniques are used to unravel the mechanism leading to hydrogen-terminated silicon surfaces upon etching. Our calculations on model compounds indicate that kinetic rather than thermodynamic considerations are responsible for the H-passivation. In the etching reactions of HF, the initial oxide removal leads to F-termination of the surface dangling bonds. Subsequent HF attack of the Si–Si back-bonds then leads to the final H-terminated surface. The principal driving force is the ionic nature of the Si–F bond which polarizes the Si–Si back-bonds. This polarization facilitates reactions with HF resulting in efficient removal of fluorine-bonded surface silicon as SiF4 leaving behind hydrogen. Analogous etching reactions of water involve larger barriers and can only be seen at elevated temperatures.
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Raghavachari, K., Higashi, G.S., Chabal, Y.J. et al. First-Principles Study of the Etching Reactions of HF and H2O with Si/SiO2 Surfaces. MRS Online Proceedings Library 315, 437–446 (1993). https://doi.org/10.1557/PROC-315-437
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DOI: https://doi.org/10.1557/PROC-315-437