Patent ID: 8304146
Filing Date: 2012-11-06
Classification: G03F

Abstract:
1. A method for manufacturing a photomask comprising the steps of: providing a photomask blank comprising selectively etching away the silicon base material layer of the light-shielding film disposed on the silicon base material layer of said phase shift film in said photomask blank while retaining the silicon base material layer of said phase shift film, wherein the silicon base material layer of said phase shift film has a total content C1 (mol %) of nitrogen and oxygen, and the silicon base material layer of said light-shielding film has a total content C2 (mol %) of nitrogen and oxygen, the difference between these total contents (C1−C2) is at least 5, and the etching step comprises the step of etching said silicon base material layer of said light-shielding film by chlorine dry etching using oxygen-containing chlorine gas in a molar ratio of oxygen to chlorine between 0.0001 and 1.