Applied Materials, Inc.

Ian R Joyce

James Victor Edwards

James Biddle

Robert J Mitchell

Robert John Clifford Mitchell

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.

Method of detecting the position of a wafer

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. The hole in the gripper flag may be somewhat smaller than the hole in the e-chuck flag so that proper alignment is assured when the illuminated spot on the 2-D sensor is at the target position for the e-check but has the dimension or total brightness corresponding to the smaller hole of the gripper.

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West Sussex, United Kingdom

Ian R Joyce