Hydrofluoroethane plasma etching of SiN, SiO2, and poly-Si films with CHF2CF3, CF3CH3, and CHF2CH3

• Selective removal of SiN, SiO 2 , and poly-Si films in hydrofluorocarbon chemistry (CHF 2 CF 3 , CF 3 CH 3 , and CHF 2 CH 3 ). • CHF 2 CF 3 dissociates into CHF 2 + and C 2 HF 4 + ions and secondary CF 3 + and CF 2 + ions are formed. • CF 3 CH 3 dissociates into C 2 H 2 F + and C 2 H 2 F 2 + ions and dominant CF 3 + ions remains. • CHF 2 CH 3 yields CHF 2 + and CF 2 CH 3 + ions, promoting polymer film deposition. Plasmas containing hydrofluorocarbon gases (CHF 2 CF 3 , CF 3 CH 3 , and CHF 2 CH 3 ) are used for the selective removal of SiN, SiO 2 , and poly-Si films when manufacturing large-scale integrated circuits. Understanding the plasma chemistry of hydrofluorocarbons is important for gaining insight into the mechanisms of these selective-etching processes. The fragmental reactants produced by the reactive plasma are essential for evaluating and controlling highly accurate selective etching. This study examined such fragments using a primary dissociation ionization threshold quadrupole mass spectrometer at an electron energy of 20 eV. Their primary dissociative ionization thresholds were identified using photoelectron-photoion coincidence spectroscopy, with photon energies ranging from 10 to 28 eV. The results showed the following: (i) the CHF 2 CF 3 molecule dissociated into ions such as CHF 2 + and C 2 HF 4 + , which formed secondary ions, such as CF 3 + and CF 2 + . The F-rich reactants effectively enhanced the etching of both SiO 2 and SiN; (ii) the CF 3 CH 3 molecule dissociated into ions such as C 2 H 2 F + and C 2 H 2 F 2 + , while the dominant CF 3 + remained as a crucial fragment for the primary etching of SiO 2 ; (iii) the CHF 2 CH 3 molecule predominantly yielded ions such as CHF 2 + , CF 2 CH 3 + and C x H y + , promoting polymer film deposition on the surfaces of SiO 2 and poly-Si.