UPW recycling in the semiconductor industry Ultrapure water

outline typical water system in semiconductor plant

the semiconductor industry uses large amount of ultrapure water rinse contaminants surface of silicon wafers later turned computer chips used in devices use every day. ultrapure water definition extremely low in contamination, once makes contact wafer surface carries residual chemicals or particles surface end in industrial waste treatment system of manufacturing facility. contamination level of rinse water can vary great deal depending on particular process step being rinsed @ time. “first rinse” step may carry large amount of residual contaminants , particles compared last rinse may carry relatively low amounts of contamination. typical semiconductor plants have 2 drain systems of these rinses combined acid waste , therefore rinse water not reused due risk of contamination causing manufacturing process defects.

definitions:

the following definitions used itrs:

upw recycle – water reuse in same application after treatment
water reuse – use in secondary application
water reclaim – extracting water wastewater

water reclaim , recycle:

some semiconductor manufacturing plants have been using reclaimed water non-process applications such chemical aspirators discharge water sent industrial waste. water reclamation typical application spent rinse water manufacturing facility may used in cooling tower supply, exhaust scrubber supply, or point of use abatement systems. upw recycling not typical , involves collecting spent manufacturing rinse water, treating , re-using in wafer rinse process. additional water treatment may required of these cases depending on quality of spent rinse water , application of reclaimed water. these common practices in many semiconductor facilities worldwide, there limitation how water can reclaimed , recycled if not considering reuse in manufacturing process.

upw recycling:

recycling rinse water semiconductor manufacturing process has been discouraged many manufacturing engineers decades because of risk contamination chemical residue , particles may end in upw feed water , result in product defects. modern ultrapure water systems effective @ removing ionic contamination down parts per trillion levels (ppt) whereas organic contamination of ultrapure water systems still in parts per billion levels (ppb). in case recycling process water rinses upw makeup has been great concern , until not common practice. increasing water , wastewater costs in parts of , asia have pushed semiconductor companies investigate recycling of manufacturing process rinse water in upw makeup system. companies have incorporated approach uses complex large scale treatment designed worst case conditions of combined waste water discharge. more new approaches have been developed incorporate detailed water management plan try minimize treatment system cost , complexity.

water management plan:

the key maximizing water reclaim, recycle, , reuse having thought out water management plan. successful water management plan includes full understanding of how rinse waters used in manufacturing process including chemicals used , products. development of critical component, drain collection system can designed segregate concentrated chemicals moderately contaminated rinse waters, , lightly contaminated rinse waters. once segregated separate collection systems once considered chemical process waste streams can repurposed or sold product stream, , rinse waters can reclaimed.

a water management plan require significant amount of sample data , analysis determine proper drain segregation, application of online analytical measurement, diversions control, , final treatment technology. collecting these samples , performing laboratory analysis can characterize various waste streams , determine potential of respective re-use. in case of upw process rinse water lab analysis data can used profile typical , non-typical levels of contamination can used design rinse water treatment system. in general cost effective design system treat typical level of contamination may occur 80-90% of time, incorporate on-line sensors , controls divert rinse water industrial waste or non-critical use such cooling towers when contamination level exceeds capability of treatment system. incorporating these aspects of water management plan in semiconductor manufacturing site level of water use can reduced as 90%.