Not all lithography is Deep/Xtreme UV even in the newest fabs, because the equipment is so expensive and relatively slow. A lot of lithography is done the old w

Not all lithography is Deep/Xtreme UV even in the newest fabs, because the equipment is so expensive and relatively slow. A lot of lithography is done the old way and is sensitive to UV from any lights. Box to box processing is almost complete, but there are times when a box may need to be opened or exposed to ambient light. So there are some pretty good reasons to not to increase uncontrolled UV light exposure.