Patent ID: 7433039

Claim:
A method of determining overlay or misalignment error on a target, the method comprising: (a) moving a target to each of a plurality of field of view (FOV) positions within a particular field of view (FOV) of a metrology tool, wherein the FOV positions are different xy positions within a plane that is perpendicular to a focus z axis of the metrology tool; (b) at each FOV position, obtaining an overlay measurement at each of a plurality of orientations of the target located at such each FOV position, and (c) at each FOV position, determining a tool-induced shift (TIS) value based on the overlay measurements that were obtained at the plurality of target orientations of the target located at such each FOV position; (d) determining which of the FOV positions has a minimum determined TIS value; and (e) for the FOV position which has been determined to have the minimum TIS value, determining and storing an actual overlay of the target located at such FOV position by subtracting such minimum TIS value from at least one of the measured overlay measurements obtained at the FOV position which has been determined to have the minimum TIS value, wherein the actual overlay value is specified to correspond to a most accurate overlay measurement from the overlay measurements obtained for the plurality of the FOV positions.