| CPC G01B 11/0625 (2013.01) | 19 Claims |

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1. A method of calibrating support rotation, comprising:
rotating a substrate support disposed in a processing chamber;
directing light into a process volume of the processing chamber through an upper window;
collecting reflected light while a first substrate is supported on the substrate support;
determining spectrum data from the reflected light;
associating the spectrum data with one or more angular positions of the substrate support;
determining a corrective factor of the substrate support for at least one of the one or more angular positions based on the spectrum data;
replacing the first substrate with a second substrate;
performing a processing operation on the second substrate while measuring a parameter of the second substrate to form one or more measurements corresponding to the one or more angular positions; and
applying the corrective factor to the one or more measurements.
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