Irradiation projection method for mask exposure in e.g. DRAM chip prodn.

摘要

The method involves using a Cr-free phase-shifting grating mask (12) and a conventional Cr mask (16). The phase-shifting mask suppresses vertically-incident components (13) of light by means of interference while oblique components (14) are strengthened for projection on to the semiconductor wafer through the conventional mask. When a resist exposure is performed by this method a resol. of 3 microns or less can be achieved with an exposure time considerably shorter than that of a standard method of oblique exposure using a filter.