PHOTOMASK AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To improve the yield which depends on the phase difference in a phase shift photomask by etching a quartz substrate of a phase shift photomask or a phase shifter part of SiO2 film by using the vapor of a soln. essentially comprising hydrogen fluoride. SOLUTION: A phase shift layer also as a halftone layer 8 on a quartz substrate 1 is an i-line halftone phase shift photomask having a two-layer structure of chromium oxide nitride/chromium nitride and is etched with a vapor of hydrofluoric acid to control the phase difference. A photomask blank is patterned by a laser drawing device and developed with an inorg. alkali developer. The chromium oxide nitride and chromium nitride in the openings are subjected to dry etching with a mixture gas of dichloromethane and oxygen. Then a resist is peeled and the substrate is washed to obtain a halftone phase shift photomask. The obtd. mask is treated with a mixture gas of hydrofluoric acid vapor and water vapor so that the quartz substrate 1 is etched to form an undercut part. Thus, the phase difference is recovered.