Method of positioning disk-shaped workpieces, preferably semiconductor wafers
AssigneeCensor Patent- und Versuchs-Anstalt
InventorHerbert E. Mayer
Life of this patent
Estimating the term…
Abstract
In the photoexposure of semiconductor wafers for the production of circuit elements, the wafers are placed in a prealignment position before being transferred to the exposure stage. A chuck acting as a prepositioning stage is rotatable by one servomotor to set the wafer in its appropriate angular position (.phi. adjustment) and is shiftable by respective servomotors in the X and Y directions. Servomotor control is effected by optical means detecting a noncircular edge portion of the wafer as well as alignment marks on the wafer inwardly of the edge thereof.
Claims5
A method for preparing a semiconductor wafer for the formation of a pattern of circuit elements at predetermined locations on a surface thereof by selective illumination of a photosensitive layer on such surface through a mask in an exposure station after orthogonal and angular prealignment of the wafer in a prepositioning station,
- comprising the steps of:
- (a) providing the wafer with a peripheral edge having a distinctive portion and with optical surface markings inwardly from said edge;
- (b) coarsely prealigning the wafer in the prepositioning station by optical detection of said distinctive edge portion and of certain of said surface markings;
- (c) transferring the wafer to the exposure station with the orientation imparted thereto in the prepositioning station;
- and
- (d) more precisely adjusting the wafer in said exposure station by optically detecting other of said surface markings.
Dependencies are inferred from the claim text.