Method for washing substrates

Abstract

A method for washing a photomask substrate or a semiconductor wafer. The mixing heat generated on mixing H.sub.2 SO.sub.4 and H.sub.2 O.sub.2 is effectively utilized for promoting the reaction. H.sub.2 SO.sub.4 and H.sub.2 O.sub.2 are discharged from separate nozzles and mixed at a mixing point directly below and proximate to the nozzles to give a H.sub.2 SO.sub.4 --H.sub.2 O.sub.2 liquid mixture. The liquid mixture is caused to descend onto near the center of the photomask kept in rotation so that the liquid mixture is spread over the substrate surface under a centrifugal force. The H.sub.2 SO.sub.4 --H.sub.2 O.sub.2 flow ratios, the height of the mixing point and the number of revolutions of the substrate are controlled for providing the uniform temperature distribution of the liquid mixture on the substrate surface and for achieving uniform washing. In this manner, the chloromethylstyrene resist materials, which are employed in electron lithography, and which are only hardly soluble, may be exfoliated by a wet exfoliation technique.

Dependencies are inferred from the claim text.