Patent ID: 8992788
Filing Date: 2015-03-31
Classification: G03F,G16Z

Abstract:
1. A method of determining an etching condition for a pattern-forming film of a photomask blank comprising a transparent substrate, said pattern-forming film on the substrate for forming a photomask pattern, and an etch mask film on the pattern-forming film for serving as a mask during etching of the pattern-forming film, the method comprising the steps of: i) forming a pattern-forming film on a transparent substrate; ii) forming an etch mask film on the pattern-forming film; iii) etching the etch mask film by fluorine base dry etching under an etching condition to be applied to the pattern-forming film, taken when a photomask pattern is formed from the pattern-forming film; iv) measuring a first etching clear time (C v) etching the pattern-forming film by fluorine base dry etching under said etching condition; vi) measuring a second etching clear time (C vii) computing a ratio (C viii) selecting an etching condition having the ratio (Cl/C the pattern-forming film is formed of a material comprising silicon or silicon and another metal, and the etch mask film is formed of a silicon-free material comprising chromium or a silicon-free material comprising tantalum.