Method of manufacturing a photomask

摘要

A photomask is manufactured from a photomask blank comprising a transparent substrate and a light-shielding film consisting of upper and lower layers of transition metal-containing silicon base materials, the content of O+N in the upper layer being higher than that of the lower layer. The light-shielding film is processed in two steps by fluorine dry etching through a resist pattern such that a lower portion of the film is left behind, and oxygen-containing chlorine dry etching for removing the remainder of the film.