Production of ultra-pure water in semiconductor plants comprises varying final degree of purity to suit various processes

摘要

Water is fed from the make-up stage to separate polishing stages so that water of varying degrees of purity can be produced, depending on the actual requirement of the particular process in which it is used. The parameters of purity cover the presence of oxygen, silicon dioxide, metals, anions, organic carbon and particles above a given size. Water for these plants is produced in three stages: (1) Pretreatment of raw water, (2) a secondary make-up and (3) the final, polishing, stage. Conventionally only water from the polishing stage is used for all processes. It is now proposed to feed water from the make-up stage to separate polishing stages so that water of varying degrees of purity can be produced, depending on the actual requirement of the particular process in which it is used. The parameters of purity cover the presence of oxygen, silicon dioxide, metals, anions, organic carbon and particles above a given size. The wafer polishing section, for instance, could use make-up rather than polished water. The subdivision of polished water quality also permits the used of cheaper piping materials in all but the purest water delivery systems.