A processor for processing integrated circuit wafers, semiconductor substrates, data disks and similar units requiring very low contamination levels. The processor has an interface section which receives wafers in standard wafer carriers. The interface section transfers the wafers from carriers onto trays for processing. The interface unit can hold multiple groups of multiple trays. A conveyor having an automated arm assembly moves wafers supported on a tray. The conveyor moves the trays from the interface along a track to several processing stations. The processing stations are accessed from an enclosed area adjoining the interface section.