Patent ID: 7632612

Claim:
A halftone phase shift mask blank for use in manufacturing a halftone phase shift mask comprising a transparent substrate, a light transmitting portion formed on the substrate for transmitting an exposure light beam, a phase shifter portion formed on the substrate for transmitting a part of the exposure light beam as a transmitted light beam and for shifting a phase of the transmitted light beam by a predetermined amount, the halftone phase shift mask being designed so that light beams passing through the light transmitting portion and through the phase shifter portion cancel each other in the vicinity of a boundary portion therebetween, thereby keeping a predetermined contrast at a boundary portion of an exposure pattern to be transferred onto the surface of an object to be exposed, wherein: the halftone phase shift mask blank comprises a phase shifter film for forming the phase shifter portion on the transparent substrate; the phase shifter film comprises an upper layer made of a material substantially consisting of silicon, oxygen, and nitrogen and a lower layer made of a material substantially consisting of tantalum and hafnium.