Etching method and photomask blank processing method

Abstract

Disclosed herein is a dry etching method for a work layer formed over a substrate, including the steps of forming a hard mask layer over the work layer formed over the substrate, forming a resist pattern over the hard mask layer, transferring the resist pattern to the hard mask layer by first dry etching conducted using the resist pattern, and patterning the work layer by second dry etching conducted using a hard mask pattern obtained upon the transfer to the hard mask layer, wherein after the hard mask layer is patterned by the first dry etching, the patterning of the work layer by the second dry etching is conducted through changing the concentration of an auxiliary ingredient of a dry etching gas, without changing a main ingredient of the dry etching gas, in an etching apparatus in which the first dry etching has been conducted.