ACID-FREE CLEANING PROCESS FOR SUBSTRATES, IN PARTICULAR MASKS AND MASK BLANKS

摘要

This invention includes processes that employ alkaline-based compositions with varying pH values and conductivities for use in surface preparation steps of substrate surfaces, such as quartz, particularly those used for photomask applications. Controlling pH values is an aspect of the invention in quartz surface cleaning, i.e., maintaining a higher pH value of the first chemical mixture than of the second chemical mixture yields higher particle removal efficiency compared to going from lower pH to higher pH. Preferably, the inventive process is an acid-free process.