Abstract: An apparatus for processing wafers one at a time. The apparatus has a vacuum chamber into which wafers are loaded through a pair of loadlocks which are spaced one above the other. A robot within the vacuum chamber has a pair of gripper arms which are moveable along and rotatable about a vertical axis so as to be moveable between the loadlocks and a wafer processing position. Each of the loadlocks has a vertically moveable portion which is moveable away from the remainder of the loadlock to provide access in a horizontal plane for one of the gripper arms. Signals from encoders and optical sensors are used to determine that a handoff position has been reached.

Abstract: The correct handover position between the gripper and the e-chuck is located using a light source and a 2-D photosensor. As the e-chuck is in the loading position it can be driven forwards or backwards in the beam direction by rotating the main whisper scan rotor. The line drawn across the 2-D array by a spot of light from the light source passing through a hole in a flag attached to the e-chuck is recorded. Similarly, the line drawn by a spot of light from the same source passing through a hole in the flag attached to the gripper is also recorded. The point of intersection is the ideal transfer point. For transfer the e-chuck is then driven to this point which can be checked from the 2-D sensor. The gripper is then also driven to the same point and alignment can be checked using the light source and sensor.