Patent ID: 7754397

Claim:
A method of manufacturing a phase-shift mask, comprising: forming a light-shielding film on a transparent substrate: and forming first apertures and second apertures in the light-shielding film in such a manner that the first apertures and the second apertures are alternately arranged and that a recessed portion having a predetermined depth is formed in the transparent substrate in coincide with the second apertures, thereby enabling light transmitted through the first apertures and light transmitted through the second apertures to alternately invert in phase thereof; wherein forming of the recessed portion is performed by the etching of the transparent substrate through the second aperture under dry etching conditions which, are set up by a process comprising: (a) determining an optimum phase shift at each pitch based on optical conditions and on an extent of undercut extending from the recessed portion of the transparent substrate to below the light-shielding film and/or a bias from a set value of the width of the second aperture and of the width of the recessed portion, the optimum phase shift being converted into an etching depth to thereby calculate an optimum etching depth; {b) when the undercut is to be formed, subtracting the extent of the undercut from the etching depth which Is derived from the conversion of the optimum phase shift to thereby calculate an optimum depth of dry etching; and (c) comparing the optimum depth of etching with data on the etching depth that can be obtained under a plurality of dry etching conditions to obtain a difference to thereby select dry etching conditions which enable the difference to become minimal, and a phase shift of transmitted light is set in accordance of a pitch between an edge of the first aperture and an edge of the second aperture of the light shielding film.