Image Rotator for Automatic Wafer-Alignment Systems
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-07
At present, mask wafer alignment tools require chevron mask-alignment marks. These chevrons are presently formed by using small increments or shapes arranged on the XY axis, thus creating a staircase effect. Because of this staircase effect, the chevrons cause image accuracy problems resulting in wafer-alignment errors. By changing to L-shaped mask-alignment marks that are aligned on the XY axis of the mask, the mask-alignment images can be reproduced more accurately with respect to the remainder of the mask. Such L-shaped alignment marks laid down on the XY axis of the mask can be readily read in the present chevron reading mask wafer aligners without substantial modification by providing an image rotating dove prism in the optical path of the mask wafer aligner.