Method for washing substrates

摘要

A method for washing a photomask substrate or a semiconductor wafer. The mixing heat generated on mixing H2SO4 and H2O2 is effectively utilized for promoting the reaction. H2SO4 and H2O2 are discharged from separate nozzles and mixed at a mixing point directly below and proximate to the nozzles to give a H2SO4-H2O2 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 H2SO4-H2O2 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.