Cool video from Lexar here, about the manufacture of those memory devices we rely on.

This looks like a Class 10 cleanroom.

I've worked in class 100 which is hairnets and overalls, booties, mouth masks. Smoking breaks allowed in a separate room.

Class 10 is the full 'Bunny Suit' (as shown here).
(Cigarettes taken-off you at reception)

I guess Class 1 is 'NO HUMANS' these days, where the wafers are fabricated. That would come before the stages shown here.

Class 1 is pretty much a totally automated and closed-system, maintained only occasionally by the guys and gals in Bunny Suits.

http://en.wikipedia.org/wiki/Cleanroom_suit