Method and apparatus for positioning substrates

A method and apparatus for positioning substrates is provided. The substrates are typically semiconductor wafers that require centering on a mounting location within a process module and orientation of a notch, flat or perimeter interruption to a known rotational position. A robot arm transfers wafers from a source to the process module. A camera is provided adjacent a path of travel of the robot arm to scan the wafers as they pass thereover. A grayscale analysis determines the centroid, or other reference point, of the wafer and the location of the notch or flat. The path of travel of the arm is altered to account for misalignment of the centroid/reference point from a known location. Data related to the rotational offset of the notch or flat relative to a known standard location is also obtained. The wafer can be rotated to position the notch or flat at a desired standard position using a rotator mounted on the robot arm or at a remote site.