METHOD FOR MANUFACTURING PHOTOMASK, AND PHOTOMASK BLANK

摘要

PROBLEM TO BE SOLVED: To enable high-accuracy etching of a light-shielding film without giving damages to a phase shift film even when no etching stopper film is used or even when a layered structure is used, the layered structure comprising a light-shielding film of a silicon-based material which is the same type of the material for the phase shift film, on the phase shift film of a silicon-based material.

SOLUTION: A method for manufacturing a photomask includes a following step carried out on a photomask blank. The photomask blank has a phase shift film formed on a transparent substrate and has a light-shielding film further formed on the phase shift film, wherein: each of the phase shift film and the light-shielding film has a silicon-based material layer; the silicon-based material layer of the phase shift film is adjacent to the silicon-based material layer of the light-shielding film; and the total content of nitrogen and oxygen in the silicon-based material layer of the phase shift film is different from the total content of nitrogen and oxygen in the silicon-based material layer of the light-shielding film. The method includes a step of selectively etching away the silicon-based material layer of the light-shielding film by chlorine-based dry etching with a predetermined ratio of chlorine gas to oxygen gas set.

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