Patent ID: 7706908

Claim:
Method for positioning a wafer ( 3 ) with a reference marker ( 6 ) in a vacuum process installation with a transport chamber comprising a transport device ( 2 , 20 , 21 ) for moving the wafer ( 3 ) in a plane to a process chamber disposed at the transport chamber and with a single sensor ( 1 ), which is disposed in front of the process chamber within the transport chamber for acquiring the position of the wafer ( 3 ) through the acquisition on its edge at a first detection point ( 4 ) and a second detection point ( 5 ), such that with electronic evaluation of the two measured detection points ( 4 , 5 ) the true position of the wafer ( 12 ), with the diameter of the wafer known, is determined and the transport device ( 2 , 20 , 21 ) actively guides the wafer ( 3 ) to a desired nominal position, characterized in that the wafer ( 3 ) with respect to its reference marker ( 6 ) is deposited on the transport device ( 2 , 20 , 21 ) with respect to its reference marker ( 6 ) aligned in predetermined position and the projection of the reference marker ( 6 ) along a motion direction determines on the wafer ( 3 ) a disallowable zone ( 22 ) and thereby the remaining circular region of the wafer ( 3 ) defines a free zone, the sensor ( 1 ) being disposed in the transport chamber such that the disallowable zone ( 22 ) is reliably not swept over and the sensor ( 1 ) thereby can only acquire the circular region of the wafer edge and no portion of the reference marker ( 6 ).