- a vertical processing chamber,
- a boat constructed to hold a number of wafers to be processed in the chamber and shaped to be inserted into and withdrawn from the vertical processing chamber through a lower end of the chamber,
- elevator means for raising a boat loaded with wafers into the chamber from a chamber loading/unloading station and for lowering a boat loaded with wafers out of the chamber back to the chamber loading/unloading station,
- said elevator means and boat structure being separate and independent of each other so that a boat with its load of wafers can, as a unit, be placed onto and taken off of the elevator means at the chamber loading/unloading station, and
- boat exchange means for transferring a boat loaded with wafers between the chamber loading/unloading station and a wafer loading/unloading station,
- said boat exchange means comprising a rotatable turntable contructed to support one boat at one location and to support another boat at a different location on the turntable so that one boat can be undergoing a loading/unloading operation of wafers in the boat at the wafer loading/unloading operation while the other boat loaded with wafers can be undergoing a related loading/unloading operation of the boat and wafers into or out of the chamber at the chamber loading/unloading station,
- said boat exchange means including rotating means for rotating the turntable to transfer boats loaded with wafers between the chamber loading/unloading station and the wafer loading/unloading station.
2. A wafer transfer mechanism for transferring a wafer from a source to a destination while compensating for any lateral offset of the actual location of the wafer center from the expected location of the wafer center in the source so that the wafer can be placed in the destination with the actual location of the wafer center very near a predetermined, desired, lateral location of the wafer center in the destination, said mechanism comprising,
- a wafer transfer module which includes a paddle which is movable vertically, radially and in a circular arc in the course of picking up a wafer from the source and transferring the wafer to the destination, and
- sensor means for finding and measuring the amount of any lateral offset of the paddle center with respect to the wafer center after the wafer has been picked up and withdrawn from the source by the paddle, and
- control means for repositioning the paddle laterally by the amount of the measured offset before delivering the wafer to the destination by the paddle.
3. The invention claimed in claim 2 wherein the source is a slot in a cassette and the destination is a slot in a boat which is to be loaded in a heating and/or processing chamber of a furnace.
4. The invention claimed in claim 2 wherein the source is a slot in a boat of the kind which is loaded in a heating and/or processing chamber of a furnace and wherein the destination is a slot in a cassette.
5. The invention defined in claim 2 including calibration means for finding said expected source location and said desired destination location by a calibration performed prior to said removing step.
6. The invention defined in claim 2 wherein the sensor means find said amount of offset by looking at two opposite edges of the wafer.
