Scanning Inspection System With Angular Correction

A rotary inspection system comprising:

• a rotary stage configured to rotate a wafer attached to the rotary stage about an axis of rotation of the rotary stage;
• a translation stage configured to translate the axis of rotation of the rotary stage along a trajectory, wherein the rotary stage and the translation stage are configured to scan a surface of a specimen under a first fixed inspection location in a spiral motion pattern, wherein the first fixed inspection location is offset from the trajectory of the axis of rotation by a first misalignment distance;
• a rotary encoder configured to generate a signal indicative of an angular position of the rotary stage;
• a translation encoder configured to generate a signal indicative of a position of the axis of rotation along the trajectory;
• and
• an angular corrector configured to determine a first angular correction value based at least in part on the first misalignment distance, a first radial distance between the axis of rotation and the first fixed inspection location at a first instance of an angular position, and a second radial distance between the axis of rotation and the first fixed inspection location at a second instance of the angular position.

An apparatus comprising:

• a processor;
• and
• a non-transitory, computer-readable medium storing instructions that, when executed by the processor, cause the apparatus to:
• receive an indication of an angular position of a rotary stage of a rotary inspection system, the rotary inspection system including the rotary stage and a translation stage configured to scan a surface of a specimen under a first fixed inspection location in a spiral motion pattern, wherein the first fixed inspection location is offset from a trajectory of the axis of rotation of the rotary stage by a first misalignment distance;
• and
• determine a first angular correction value based at least in part on the first misalignment distance, a first radial distance between the axis of rotation of the rotary stage and the first fixed inspection location at a first instance of the angular position, and a second radial distance between the axis of rotation of the rotary stage and the first fixed inspection location at a second instance of the angular position.