Patent ID: 9587936
Date: 2017-03-07
CPC Classifications: G01B,G01N,G03F

Claim:
1. A method comprising: rotating a wafer attached to a rotary stage about an axis of rotation of the rotary stage; translating the axis of rotation of the rotary stage along a trajectory by a translation stage, 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; generating a signal indicative of an angular position of the rotary stage; generating a signal indicative of a position of the axis of rotation along the trajectory; and determining 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.