A device for processing wafer-shaped articles comprises a closed process chamber. The closed process chamber comprises a housing providing a gas-tight enclosure, a rotary chuck located within the closed process chamber and adapted to hold a wafer shaped article thereon, and an interior cover disposed within said closed process chamber. The interior cover is movable between a first position in which the rotary chuck communicates with an outer wall of the closed process chamber, and a second position in which the interior cover seals against an inner surface of the closed process chamber adjacent the rotary chuck to define a gas-tight inner process chamber.
