Chemical Reaction Dynamics of SiO₂ Etching by CF₂ Radicals: Tight-Binding Quantum Chemical Molecular Dynamics Simulations

Abstract

The plasma etching of SiO2 by CF2 radicals was investigated using a newly developed etching process simulator based on tight-binding quantum chemical molecular dynamics (TB-QCMD). CF2 radicals were continuously irradiated on the SiO2(001) surface and then the dissociations of the C–F and Si–O bonds were observed. We also observed the generation of CO and CO2 molecules and Si–F bonds, which is in good agreement with previous experiments. The formation of etching holes was realized after the continuous irradiation of CF2 radicals. Furthermore, the effect of radical velocity on etching efficiency was also examined. The ratio of penetration depth to the width of irradiated atoms was examined for the evaluation of etching efficiency. The ratio increases as the irradiation velocity of CF2 radicals increases. Our TB-QCMD etching process simulator is capable of predicting etching rate and aspect ratio depending on the velocity of irradiated radicals.

c-C4F8Plasmas for the Deposition of Fluorinated Carbon Films

“…With CF 4 no film formation was found for CF X and the growing rate was significantly lower for F‐DLC (i.e., growing rate 10 nm min −1 ). Although formation of fluorinated DLC by using CF 4 has been reported in literature, the lower ( F‐DLC ) or zero ( CF X ) deposition rates determined here agree with the common use of this gas for etching applications . Although a thorough analysis of the differences in CF 4 and c ‐C 4 F 8 plasmas is outside the scope of the present work, it is interesting to compare the mass spectra recorded with these two precursors under typical deposition conditions of F‐DLC and CF X (c.f., Figure ).…”

“…After a careful analysis of the species detected in the plasma and their energy distribution functions these authors established interesting correlations between the plasma characteristics and bias potential at the substrate and critical features of the obtained films such as hardness, sp 3 /sp 2 ratio, deposition rate, etc. Fluorine containing plasmas, mainly using CF 4 as fluorine precursor, have been widely studied in relation with the controlled etching of SiO 2 and silicon . Although less common, the use of c ‐C 4 F 8 (i.e., octafluorocyclobutane) plasmas has been also reported for etching applications, either mixed with Ar or with Ar/O 2 .…”

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

“…In doing so, positive charge is deposited on the surfaces. 19 Electrons also deposit charge, though due to their nearly isotropic trajectories incident onto the surface compared with ions, electron charging dominantly occurs on the top and upper portion of the features. Positive ions striking sidewalls at grazing angles neutralize and specularly reflect and then proceed as hot neutrals, retaining a large fraction of their initial energy.…”

“…A molecular dynamics simulation was used to investigate the consequences of hot CF 2 and CF 3 radicals in SiO 2 etching. 19,30 At low energies (10 eV), CF 2 was the main etchant to break the Si-O bond due to its higher chemical reactivity. At high energies (150 eV), CF 3 became the main etchant due to the production of more reactive F atoms, resulting in the formation of more Si-F bonds.…”

Micro-machining: An overview (Part II)

“…149 • Chemical energy-based processes The plasma etching of SiO 2 by CF 2 radicals was simulated by employing QC-MDS. They found that C-F and Si-O bonds get dissociated during etching, and it further leads to the formation of CO and CO 2 gas followed by a new chemical bonding of Si-F. 150 Moreover, a set of experiments was also carried out, and a good agreement between MDS and experimental results was obtained. Anisotropic etching of silicon was investigated using molecular dynamics through extended Tersoff potential, in which the transition of electric charge was studied during chemical etching as a function of atomic distance.…”