Phase-shift photomask production with accurate pattern

摘要

A phase-shift photomask production process comprises (a) forming a surface recess in a transparent substrate and covering the substrate and the recess with a light screening layer; (b) forming a protective layer with apertures and etching the light screening layer through the apertures; (c) producing sidewall spacers on the side walls of the light screening layer and the protective layer and etching the substrate to a predetermined depth using the spacers as mask; and (d) removing the sidewall spacers and the protective layer. Also claimed is a similar process in which two photoresist films are used instead of the protective layer.