Image Number 2 for United States Patent #6348405.
A TiN film and an ARL-SiON film (plasma SiO.sub.2 film+plasma SiON film) are deposited on a metal interconnection layer. The film thickness and the film quality of the ARL-SiON film is optmized to minimize the reflectance factor of the metal interconnection layer, and the composition of the ARL-SiON film is so adjusted that the ARL-SiON film can be easily dissolved by a hydrofluoric acid in a later process. The multi-layer antireflection layer composed of the TiN film and the ARL-SiON film, and the underlying metal interconnection layer are continuously dry-etched in the same processing chamber. At this time, the basis of the etching gas is composed of a combination of chlorine based gases (Cl containing gas such as Cl.sub.2, BCl.sub.3, HCl) which is the same as that used for etching the metal film. Furthermore, when the etching gas composed of a combination of Cl.sub.2 and BCl.sub.3 is used, the mixing ratio of the etching gas is changed. Thus, the inorganic antireflection layer is hard of changing its film nature even if it is subjected to a wet removing treatment and a plasma ashing for the resist when the rework of the lithography becomes necessary.