Patent ID: 9476701
Filing Date: 2016-10-25
CPC Classification: G01B,H01L

Claim Text:
1. An apparatus for detecting a pre-aligning element at a wafer, the wafer having the pre-aligning element at a wafer edge, the apparatus comprising: a sensor arrangement configured to illuminate subsequent edge portions of the wafer edge, to receive transmitted fractions and reflected fractions of an illumination from the illuminated edge portions, and to output a first and a second sensor signal, wherein the first sensor signal is based on the transmitted fractions of the illumination and the second sensor signal is based on the reflected fractions of the illumination, wherein the first sensor signal indicates a degree of measured intensity or brightness of the transmitted fraction of the illumination, and wherein the second sensor signal comprises a video frame or a picture; and an evaluation unit comprising a programmable logic device and configured to evaluate the first sensor signal and to determine a first position information indicating a coarse position of the pre-aligning element within the currently evaluated edge portion, when the first sensor signal indicates that the transmitted fractions of the illumination have reached a predetermined threshold value, wherein the first position information indicates that the pre-aligning element is located within the currently evaluated edge portion, and, after having determined the first position information, to determine a second position information based on the second sensor signal and the first position information, wherein the second position information indicates a fine position of the pre-aligning element, and wherein the second position information gives a more accurate information about the exact position of the pre-aligning element when compared to the first position information.