Phase mask for projection lithography and method for the manufacture thereof comprising a selectively etchable phase shift layer directly on substrate

Claim 1

A projection lithography phase mask used with light having a wavelength λ and an exposure means having an imaging scale m and a numerical aperture NA, comprising: a composite carrier comprised of a substrate formed of a light-transmissive first material and a carrier structure directly on the substrate of a light-transmissive second material having a refractive index n 2 , and wherein the second material is selectively etchable with respect to the surface of the substrate in an anisotropic etching process; the carrier structure having a mask pattern directly thereon with openings at selected first regions where a surface of the carrier structure is exposed, and the carrier structure having openings therein so as to expose the substrate at selected second regions; and given exposure in a medium having a refractive index n 1 , the substrate at said second region having an optical thickness which is lower by d=λ(1 +/-1/3)/(2 (n 2 -n 1 )) than an optical thickness of said composite carrier formed of said carrier structure and substrate at said first regions.