Systems and methods for wafer handling in semiconductor process equipment

In a wafer handling system for carrying a batch of semiconductor wafers to a wafer transfer station associated with wafer processing equipment for batch processing a standard complement of wafers, a wafer handling tray for carrying a standard plastic wafer cassette having a plurality of wafer carrying slots with bottom access apertures communicating with each of said slots;

• transport means for conveying said wafer handling tray to a wafer transfer station and for indexing said wafer handling tray to a plurality of accurate wafer transfer positions with corresponding bottom access apertures in said plastic wafer cassette located at a predefined wafer transfer position at said wafer transfer station;
• and wafer transfer means at said wafer transfer station for transferring a wafer from each of said wafer slots to a wafer receiving surface associated with said wafer processing equipment, said wafer handling tray comprising frame means adapted to removably receive a standard plastic wafer cassette adapted to carry up to a standard batch number of semiconductor wafers of a prearranged diameter, and a dummy wafer cassette mounted to one end of said frame and adapted to carry a plurality of semiconductor wafers of the same diameter as wafers carried in said standard cassette in a plurality of wafer tray slots having bottom access apertures, whereby one or more of said wafers carried in said dummy wafer cassette may be withdrawn at said wafer transfer station to substitute for any wafers missing in slots in said standard plastic wafer cassette;
• said water handling system being adapted for carrying a plurality of batches of semiconductor wafers to said wafer transfer station associated with equipment for processing said wafers in a vacuum chamber environment, and further comprising a load lock enclosure having a front door adapted to open to permit insertion of wafer cassette trays and to close and seal for evacuation of said enclosure;
• said wafer transfer station being located in said load lock enclosure;
• wall means defining a wafer transfer port between said load lock enclosure and said wafer processing equipment, said wafer transfer port being positioned at a wafer transfer location defined at said wafer transfer station;
• valve means selectably positionable over said port to isolate said vacuum chamber from said load lock enclosure;
• a plurality of said wafer handling trays for carrying a plurality of standard plastic wafer cassettes;
• said transport means comprising a rotating carousel including a plurality of radially arrayed paddles for carrying said plurality of wafer handling trays and transporting said trays from a loading position adjacent said front door to a tray transfer position defined at a remote location within said load lock enclosure;
• and tray transfer means at said tray transfer position defined at a remote location within said load lock enclosure for removing said tray from one of said paddles, for transporting said tray to said wafer transfer station and for indexing said tray and wafer cassette thereon to sequentially position said wafer carrying slots in said plastic wafer cassette at said wafer transfer position.