Method for designing levenson photomask

Abstract

In a Levenson photomask design method of partially forming a plurality of opening patterns for passing incident light in a light-shielding film for shielding the incident light, and arranging, on some patterns, phase shifters, line segment pairs of different patterns which are adjacent to each other within a predetermined distance R are extracted in units of line segments obtained by dividing the patterns. A pattern within a predetermined distance S from the central point of the opposite region of a line segment pair of interest in a direction perpendicular to the line segments is obtained. The obtained pattern is subjected to a process simulation to obtain resolution easiness representing the easiness in resolving the adjacent patterns. On the basis of the resolution easiness obtained for the adjacent pattern pair within the distance R, a phase shifter is arranged in ascending order of resolution easiness to give a phase difference. Resolution suitable for the exposure condition used can be obtained by a simple method. When the shifter arrangement is determined in consideration of the resolution easiness, a high-resolution shifter arrangement can be realized for a Levenson phase shift mask.