Phase shift mask blank and phase shift mask

摘要

The present invention provides a photomask blank used for producing a photomask to which an ArF excimer laser light is applied, wherein: a light-shielding film is provided on a light transmissive substrate; the light-shielding film has a laminated structure in which a lower layer, an interlayer and an upper layer are laminated in this order from the side close to the light transmissive substrate; the thickness of the entire light-shielding film is 60 nm or less; the lower layer is made of a film containing a metal and has a first etching rate; the upper layer is made of a film containing a metal and has a third etching rate; the interlayer is made of a film containing the same metal as that contained in the lower layer or the upper layer and has a second etching rate that is lower than the first etching rate and the third etching rate; and the thickness of the interlayer is 30% or less of the thickness of the entire light-shielding film.