Patent ID: 7824824

Claim:
A method of forming a phase shifting lithography mask, comprising: providing a substrate which is substantially transparent to light of given wavelength used to effect lithographic pattern transfers; the substrate including a layer of etch stop material over a first layer of light transmissive material comprising at least one of quartz or glass; and a second layer of light transmissive material comprising at least one of quartz or glass over the layer of etch stop material; the layer of etch stop material and the second layer of light transmissive material having different etch selectivity; providing a patterned layer of opaque material over the second layer of light transmissive material; and selectively etching the second layer of light transmissive material through the patterned layer down to the layer of etch stop material; wherein the first layer of light transmissive material, the layer of etch stop material and the second layer of light transmissive material have thicknesses such that light of the given wavelength directed from a light source through etched portions of the substrate to pattern a photosensitive surface will be shifted in phase by a given amount relative to light of the given wavelength transmitted through unetched portions of the substrate.