Contrary to what one might think, the lithographic process does not start with coating a wafer with photoresist. Instead, it starts with getting a photoresist bottle to and into a cleanroom. The logistics of this operation demand that a photoresit have a shelf life of at least 6 months; actually, most commercial photoresists are specified for more than that period. What can happen to a photoresist during the time between bottling and end use?
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