Patent ID: 8309277
Filing Date: 2012-11-13
Classification: G03F

Abstract:
1. A method for manufacturing a photomask from a photomask blank comprising a transparent substrate and a light-shielding film disposed thereon, the light-shielding film consisting of upper and lower layers made of transition metal-containing silicon base materials, at least the upper layer containing oxygen and/or nitrogen, the total content of oxygen and nitrogen in the upper layer being higher than that of the lower layer, the method comprising a first stage etching step of dry etching the light-shielding film with fluorine base etchant gas using a resist pattern formed on the light-shielding film as an etch mask, for removing only the entirety of the upper layer or the entirety of the upper layer and a portion of the lower layer disposed remote from the transparent substrate such that at least a portion of the lower layer disposed adjacent to the transparent substrate is left behind, and a second stage etching step of dry etching the light-shielding film with oxygen-containing chlorine base etchant gas for removing the remainder of the light-shielding film which has not been removed by the first stage etching step, thereby processing the light-shielding film into the desired pattern, said photomask blank meets that provided that the material of the upper layer has a total content C