Patent ID: 8555214

Claim:
A computer-implemented method for calculating reflected light from a multilayer stack in a reflective photo-mask, comprising: determining, using a computer, contributions from multiple discrete cells in a model of the multilayer stack in the reflective photo-mask to the reflected light based on angles of incidence of light in a light pattern to the multilayer stack, a polarization of the light in the light pattern, and a varying intensity of the light in the light pattern through the multilayer stack, wherein the multiple discrete cells are at horizontal and vertical positions in the multilayer stack, and wherein the multilayer stack includes at least one defect; adjusting phase values of the contributions to the reflected light from the multiple discrete cells, thereby specifying optical path differences between the multiple discrete cells in the multilayer stack that are associated with the defect; combining the contributions to the reflected light from multiple discrete cells to determine the reflected light from the multilayer stack; and selectively shifting k-space representations of the contributions to the reflected light from the multiple discrete cells based on the angles of incidence, thereby accounting for phase variations associated with deviations from normal incidence.