Photomask and exposure method using a photomask

Abstract

Disclosed is a photomask in which contrast of light intensity of a pattern to be transferred (main pattern) is enhanced on an image plane while transfer of auxiliary pattern themselves is suppressed. The photomask, which is used in exposure to which is applied four-point illumination method for inverting phase of light that passes through mutually adjacent patterns, has first auxiliary patterns, disposed above and below and to the left and right of a main pattern to be transferred, to thereby provide a transparent substrate with a surface flush with the main pattern or with a difference in level corresponding to a phase difference with respect to the main pattern that is K times 360° (where K is an integer that does not include zero), and second auxiliary patterns disposed at angles of 45° with respect to the main pattern, the second auxiliary patterns providing a difference in level corresponding to a phase difference, with respect to the first auxiliary patterns, that is (2L+1) times 180° (where L is an integer inclusive of zero). The contrast of the first auxiliary patterns is reduced by the second auxiliary patterns, thereby enlarging the depth of focus.