CROSS-SECTIONS FOR ELECTRON-IMPACT DISSOCIATION OF ALTERNATIVE ETCHING GAS, C3HF7O

The search for alternative for perfluorocarbon gases from the environm ental point of view has resulted in a new etching gas, C3HF7O (1,2,2,2 -tetrafluoroethyl-trifluoromethyl ether, abbreviated as HFE-227). In t his paper, the first measurement of the absolute cross sections for th e dissociation of HFE-227, is reported. The neutral dissociation is me asured from the threshold to 250 eV by appearance mass spectrometry in a dual electron beam device. The threshold energies for the neutral d issociation into CE CF2 and CF3 are 14.7. 12.5 and 11.2 eV, respective ly The cross sections for the dissociation from HFE-227 into CF3 and C F are larger than those from c-C4F8 (octafluorocyclobutane), but not f or the dissociation into CF2. Besides the neutral dissociation, the cr oss sections for the dissociative ionization of HFE-227 ar extensively measured for the formation of twelve ionic species: i.e., CO+, CHO+, CF+, CHF+, CFO+, CF2+, CHF2+, CF3+, CHF3+, C2HF2O+, C2HF4+ and C2HF4O.