Method of inhibiting contaminants using dilute acid rinse

摘要

A method for forming chrome photomasks and phase-shift masks without producing chrome opaque defects. The method involves rinsing the mask blank with dilute acid, preferably nitric or perchloric acid, during processing to form the photomask. When a dry etch is used to form the photomask, the mask blank is rinsed after wet development of the photoresist. When a wet etch is used to form the photomask, the mask blank is rinsed after the wet etch. This method decreases the number of defects per photomask as well as the mask-to-mask variation in the number of defects.