ABSTRACT
The cleanrooms of today’s semiconductor manufacturing facilities have unique air environments. The air is highly filtered for particles over both the coarse and fine-size ranges. The number of air exchanges per hour (~10/min) is much larger than in ordinary office and home environments. Air is forced downwards unidirectionally, entering the cleanroom from the ceiling at a relatively high velocity (^50 cm/s) compared to air movement in a typical indoor environment. This flow rapidly removes particles generated in the cleanroom by moving the air down and out of the room and through another series of particle filters prior to reintroduction into the “clean” airstream that reenters the cleanroom. What have traditionally not been controlled or even monitored are the molecular contaminants that readily penetrate these high-quality particle filters, although some advanced cleanroom designs in the United States do now include hardware to remove specific families of gaseous species in the air-handling systems. This chapter reviews the types and properties of airborne molecular contaminants found in a cleanroom and their deposition on wafer surfaces.
