“…Furthermore, chemical reaction probabilities are also scarcely reported. Reaction probabilities for F 2 on clean Si(100) are predicted by Carter and Carter, while consecutive impacts of SiF 3 , SiF 2 , and SiF ions on Si(100) are investigated by Gou and co-workers. − Marcos et al investigated the evolution of an etched Si surface under SF 6 /O 2 plasma treatment with Monte Carlo simulations. They compared calculated etched trench profiles obtained with different predefined sticking coefficients for the F atoms and different SF 6 /O 2 gas ratios to determine the role of the passivation layer and how it protects the sidewalls from undercutting effects …”
Cyrogenic etching of silicon is envisaged to enable better control over plasma processing in the microelectronics industry, albeit little is known about the fundamental differences compared to room temperature. We here present molecular dynamics simulations carried out to obtain sticking probabilities, thermal desorption rates, surface diffusion speeds and sputter yields of F, F 2 , Si, SiF, SiF 2 , SiF 3 , SiF 4 and the corresponding ions on Si(100) and on SiF 1-3 surfaces, both at cryogenic and near-room temperature. The different surface behavior during conventional etching and cryoetching is discussed. F 2 is found to be relatively reactive compared to other species like SiF 0-3 . Thermal desorption occurs at a significantly lower rate at cryogenic conditions, which results in an accumulation of physisorbed species. Moreover, ion incorporation is often observed for ions with energies of 30-400 eV, which results in a relatively low net sputter yield. The obtained results suggest that the actual etching of Si, under both cryogenic and near-room temperature conditions, is based on the complete conversion of the Si surface to physisorbed SiF 4 , followed by subsequent sputtering of these molecules, instead of direct sputtering of the SiF 0-3 surface.
“…Furthermore, chemical reaction probabilities are also scarcely reported. Reaction probabilities for F 2 on clean Si(100) are predicted by Carter and Carter, while consecutive impacts of SiF 3 , SiF 2 , and SiF ions on Si(100) are investigated by Gou and co-workers. − Marcos et al investigated the evolution of an etched Si surface under SF 6 /O 2 plasma treatment with Monte Carlo simulations. They compared calculated etched trench profiles obtained with different predefined sticking coefficients for the F atoms and different SF 6 /O 2 gas ratios to determine the role of the passivation layer and how it protects the sidewalls from undercutting effects …”
Cyrogenic etching of silicon is envisaged to enable better control over plasma processing in the microelectronics industry, albeit little is known about the fundamental differences compared to room temperature. We here present molecular dynamics simulations carried out to obtain sticking probabilities, thermal desorption rates, surface diffusion speeds and sputter yields of F, F 2 , Si, SiF, SiF 2 , SiF 3 , SiF 4 and the corresponding ions on Si(100) and on SiF 1-3 surfaces, both at cryogenic and near-room temperature. The different surface behavior during conventional etching and cryoetching is discussed. F 2 is found to be relatively reactive compared to other species like SiF 0-3 . Thermal desorption occurs at a significantly lower rate at cryogenic conditions, which results in an accumulation of physisorbed species. Moreover, ion incorporation is often observed for ions with energies of 30-400 eV, which results in a relatively low net sputter yield. The obtained results suggest that the actual etching of Si, under both cryogenic and near-room temperature conditions, is based on the complete conversion of the Si surface to physisorbed SiF 4 , followed by subsequent sputtering of these molecules, instead of direct sputtering of the SiF 0-3 surface.
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