Because of environmental pollution prevention laws, PFC (perfluorocarbon)
and HFC (hydrofluorocarbon), both etching gases for silicon oxide and silicon nitride
films, are expected to be subjected to limited use or become difficult to obtain
in the future. An etching gas containing fluorine atoms is introduced into a plasma
chamber. In a region where plasma etching takes place, the fluorine-containing
gas plasma is made to react with solid-state carbon in order to produce molecular
chemical species such as CF4, CF2, CF3 and C2F4
for etching. This method assures a high etch rate and high selectivity while
keeping a process window wide.
