Dual-function remote plasma etching/cleaning system applied to selective etching of SiO2 and removal of polymeric residues

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A dual-function chamber integrating (i) remote rf plasma-enhanced etching with low energy, <100 eV, ion bombardment and (ii) in situ Si surface cleaning and passivation is described. This plasma-assisted processing system is applied to the etching of SiO2 layers on Si(100) wafers, followed by the removal of the polymeric residues and the passivation of the exposed Si surface. A SiO2 etch rate of ∼5 nm/min was obtained at a CF4 partial pressure as low as 0.25 mTorr. An etching yield with respect to a single ion bombardment was estimated to be 0.38 (SiO2 unit/ion) at a substrate bias of −100 V. Combining in situ mass spectroscopy for end-point detection via the SiF+3 signal, and on-line Auger electron spectroscopy, we have followed the changes in the sample surface as the SiO2 layer was first removed, and the exposed Si surface was eventually contaminated with polymeric residues comprised of C and F. We discuss the effectiveness of in situ exposures to plasma-generated atomic H and/or reactive O in removing these polymeric residues.