| CPC G01B 21/042 (2013.01) | 19 Claims |

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1. A method comprising:
inserting a calibration disc into a processing chamber using a robot arm;
determining a first position of a center of the calibration disc using one or more sensors positioned at a port of the processing chamber as the calibration disc is inserted into the processing chamber;
placing the calibration disc onto a substrate support within the processing chamber, wherein one or more features of the calibration disc cause the calibration disc to become centered on the substrate support;
removing the calibration disc from the substrate support and from the processing chamber using the robot arm;
determining a second position of the center of the calibration disc using the one or more sensors as the calibration disc is removed from the processing chamber;
determining a difference between the first position of the center of the calibration disc and the second position of the center of the calibration disc; and
determining an offset to apply to the robot arm when placing wafers onto the substrate support based on the determined difference.
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