Re:Here's a question... (Score 1)

It is yellow. The reason for this are indeed the frequencies of light. Although the photoresist used on wafers under process during the litho steps is most sensitive to a certain wavelenght (193 nm for 90 nm feature size, see wikipedia on litho), unindented exposure most be avoided at all costs.

Working under normal light would ruin any wafer with photoresist. Working in total dark would be ideal, but yellow is supposed to be some good compromise between working conditions and process issues.

Allthough the litho part of chip manufactering happens under the yellow light, other parts of a cleanroom normally have normal lightning.