Etching method

Abstract

A dual damascene structure with a lesser degree of shoulder loss is achieved. In a method for forming a dual damascene structure having a shoulder in an organic low k film layer by dry-etching the organic low k film layer 208 and a mask layer 210 formed over the organic low k film 208 using at least two different mixed gases, a first step in which the mask layer is etched using a first process gas and then the organic low k film layer is etched into a predetermined depth by continuously using the first process gas and a second step following the first step, in which the organic low k film layer is etched using a second process gas are executed. Since a protective wall is formed at a side wall of a via during the first step, the extent of the shoulder loss occurring in the junction region where a trench and a via form a junction can be reduced.

Dependencies are inferred from the claim text.