| 摘要 |
In order to suppress a base loss although the shape of the lower end of a recessed portion is enlarged when a multilayer film is subjected to plasma etching, a main etching step in which by performing plasma etching by introducing treatment gas containing CF-based gas and oxygen gas into a treatment chamber, a recessed portion is formed to a predetermined depth in a multilayer film formed on a base silicon film and having a laminated film formed by alternately laminating first films and second films with different relative dielectric constants, and thereafter an over etching step in which the recessed portion is formed until the base silicon film is exposed are performed, and in the over etching step, first over etching which is performed with the flow rate ratio of the oxygen gas to the CF-base gas being increased compared to main etching, and second over etching which is performed with the flow rate ratio of the oxygen gas to the CF-based gas being reduced compared to the first over etching are repeated more than once. |
