Plasma etching method using gas molecule containing sulfur atom

Abstract

Provided is a plasma etching method that enables, in a semiconductor fabrication process, selective processing of a film consisting of a single material, such as SiOor SiN, or a composite material of SiOand SiN over a mask material as well as processing into satisfactorily vertical processed shapes. It is possible, for example, to enhance selectivity over a mask material or other materials excluding an etching target, to reduce damage on sidewalls, and to suppress etching in the lateral direction by generating a plasma of a gas compound having a thioether skeleton represented by general formula (1) or a mixed gas thereof and etching a film consisting of a composite material or a single material, such as SiOor SiN, thereby depositing a protective film that contains sulfur atoms and has a lower content of fluorine atoms than the cases of using common hydrofluorocarbon gases:general formula (1): Rf—S—Rf  (1)where Rfis a monovalent organic group represented by CHFand Rfis a monovalent organic group represented by CHF.