Method of designing phase grating pattern for use in modifying illumination in an exposure process, and method of manufacturing a photo mask system having the phase grating pattern

Abstract

A method of designing a phase grating pattern and a method of manufacturing a photo mask using the design method are aimed at enhancing the resolution of a photolithographic process. A modified form of illumination, which will irradiate a main mask pattern to be transcribed onto a wafer using the photolithographic process and thereby enhance the transcription process, is selected. An area over which patterns for providing the modified form of illumination is divided into a plurality of subcells. Phase values are arbitrarily assigned and a phase values to the subcells. One of the subcells is randomly selected, and a phase value is assigned to the randomly selected subcell. These steps are repeated producing new arrangements of the phase values assigned to the subcells. The arrangements of the phase values are evaluated to determine whether any of them correspond to the selected modified illumination. When such a correspondence is realized, a phase grating pattern made according to the arrangement of phase values is produced as part of an auxiliary mask or as part of the main mask.