Technique for analyzing a reflective photo-mask

A non-transitory computer-program product for use in conjunction with a computer system, the computer-program product comprising a computer-readable storage medium and a computer-program mechanism embedded therein to calculate reflected light from a multilayer stack in a reflective photo-mask, the computer-program mechanism including:

• instructions for determining 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;
• instructions for 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;
• instructions for combining the contributions to the reflected light from multiple discrete cells to determine the reflected light from the multilayer stack;
• and
• instructions for 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.

A computer system, comprising:

• at least one processor;
• at least one memory;
• and
• at least one program module, the program module stored in the memory and configured to be executed by the processor to calculate reflected light from a multilayer stack in a reflective photo-mask, the program module including:
• instructions for determining 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;
• instructions for 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;
• instructions for combining the contributions to the reflected light from multiple discrete cells to determine the reflected light from the multilayer stack;
• and
• instructions for 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.