| 摘要 |
In an optical alignment and exposure machine, particularly suited for aligning semiconductive wafers with and exposing them to microelectronic circuit patterns, two stages of mechanical prealignment of the wafers are performed. In the first stage of mechanical prealignment a wafer is received at a prealignment station where the periphery of the wafer engages at least one of three belt-driven rollers in such a manner as to turn the wafer so as to align a flat side edge or alignment flat of the wafer with two of the three rollers. A transfer arm picks up the first-stage prealigned wafer and transfers it to a rotatable alignment and exposure chuck carried by an X-Y addressable work stage. In the second stage of mechanical prealignment two alignment members coupled to the rotatable chuck for rotation therewith index with the alignment flat of the wafer, and additional alignment members also coupled to the rotatable chuck for rotation therewith index either the center of the wafer or a rounded side edge of the wafer to a predetermined position. An optical alignment system permits rotation of the chuck to more precisely align images of alignment marks on the wafer with alignment marks on the mask. Following such precision alignment of the first wafer, the second stage of mechanical prealignment of each succeeding wafer is performed at the final angular position of the chuck during the preceding precision alignment performed with the optical alignment system. Apparatus is coupled to the chuck for selectively moving a wafer supported on the chuck into engagement with a stop to accurately position the plane of an emulsion on the wafer with respect to a focal plane of the optical alignment system. |
