PURPOSE: To provide a photomask blank and a production method for a photomask for obtaining a photomask having high productivity, stability and high quality by applying a dry etching method using a positive electron beam resist which has high sensitive performance is spite of an insufficient dry etching resistance.
CONSTITUTION: The photomask blank is composed of a light shielding film 2 mainly consisting of both chromium (Cr) and silicon (Si) and a low reflecting film 3 consisting of a chromium oxide or a chromium nitrogen oxide. After selectively applying the dry etching method to the low reflecting film 3 by using a gaseous mixture composed of the blank and carbon tetrachloride and oxygen or a gaseous mixture composed of the blank and dichloromethane and oxygen, a dry etching method is selectively applied to the light shielding film 2 by using gaseous oxygen with a formed low reflecting film pattern 8 as a mask.
NISHIYAMA YASUSHI
FUKUHARA NOBUHIKO
TAIHICHI TAKEHIRO
