Selective etching of SiN against SiO2 and poly-Si films in hydrofluoroethane chemistry with a mixture of CH2FCHF2, O2, and Ar

Gas chemistry has a significant impact on etch selectivity in semiconductor device fabrication, which is important for realization of atomic-scale removal and formation of high-aspect ratio features. To widen the controllable changes in the etchant composition in etching processes, our previous calculation showed the possibility of the controllable generation of CH2F and CHF2 related ions and radicals from a 1,1,2-trifluoroethane (CH2FCHF2) parent gas. The etch selectivity among silicon nitride (SiN), silicon dioxide (SiO2) and poly-Si films using CH2FCHF2 plasma mixed with O2 and Ar was investigated. The effects of the CH2FCHF2 and O2 partial pressures on the composition of CHF2+ and CH2F+ ions, which were measured with a quadrupole mass spectrometer, and on the possible reactions with respect to the CH2FCHF2 and O2 mixed gas phase were investigated using quantum chemical calculations. The etch selectivity was investigated through surface etching reactions for SiN, SiO2, and poly-Si films.