Patent ID: 8043771

Claim:
A phase shift mask blank comprising a substrate transparent to exposure light, a phase shift film containing silicon, a light-shielding film made of a material containing a metal and being resistant to etching of said phase shift film, and an etching mask film made of an inorganic material resistant to etching of said light-shielding film, said phase shift film, said light-shielding film, and said etching mask film being formed in this order on said substrate, wherein ( t 1 /v 1 )≦( t 2 /v 2 ) where t 1 is a thickness of said phase shift film, v 1 is an etching rate of said phase shift film by dry etching with an etchant using said etching mask film and said light-shielding film as a mask, t 2 is a thickness of said etching mask film, and v 2 is an etching rate of said etching mask film by dry etching with said etchant.