Patent ID: 6866468

Claim:
Loading and unloading station for a device for the processing of circular flat workpieces, particularly semiconductor wafers, comprising: a carrier ( 34 ) for carrying a workpiece ( 42 ), the carrier can be moved along a vertical and a horizontal axis by a first drive means, the carrier has an approximately planar lower contact surface ( 36 ) and vacuum engagement means whereby the workpiece ( 42 ) is adapted to be held against the contact surface ( 36 ) by the vacuum engagement means, a retaining ring ( 40 ) integral to the carrier ( 34 ) encircling the lower contact surface ( 36 ) and projecting downwards beyond the contact surface ( 36 ), the retaining ring ( 40 ) has an inner diameter which is slightly larger than the outer diameter of the workpiece ( 42 ) and an outer circumferential surface, at least three centering cams ( 16 ) arranged in a circumferentially spaced relationship on a circle and which can be moved synchronously and radially inwards and outwards by second drive means ( 24 ), the centering cams ( 16 ) each having a upper adapted to support the workpiece ( 42 ) placed onto the cam ( 16 ) from above, each supporting surface ( 28 ) having an approximately vertical stop surface ( 30 ), as well as a stop ( 32 ), the stop ( 32 ) being arranged radially outwardly with respect to the vertical stop surface ( 30 ), the stop ( 32 ) being adapted to engaged the outer circumferential surface of the retaining ring ( 40 ) when the centering cams ( 16 ) are moved radially inwardly and the carrier ( 34 ) is lowered close to or onto the centering cams ( 16 ), a robot ( 46 ) by means of which a workpiece ( 42 ) is deposited on the supporting surfaces of the centering cams ( 16 ), the dimension of the retaining ring ( 40 ) and the location of the stop surface ( 30 ) and the stop ( 32 ) being such that the workpiece ( 42 ) is approximately centered relative to the vertical axis of the carrier ( 34 ) above the centering cams when the stops ( 32 ) of the centering cams ( 16 ) are in engagement with the outer circumferential surface of the retaining ring ( 40 ) whereby the carrier ( 34 ) can pick up and hold the workpiece ( 42 ) at the lower contact surface by the vacuum engagement means in centered orientation and control means for controlling the first and second drive means.