Patent ID: 11861824
Assignee: KLA CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 20:
21. An overlay metrology system, comprising:
an optical sub-system comprising:
one or more optical elements configured to illuminate a sample with light from an illumination source in accordance with a metrology recipe; and
one or more optical elements configured to direct at least a portion of light from the sample to a detector located at a pupil plane;

a controller communicatively coupled to the optical sub-system, wherein the controller includes one or more processors configured to execute program instructions causing the one or more processors to implement the metrology recipe by:
receiving metrology data associated with a plurality of overlay targets on one or more samples from the optical sub-system;
generating a reference metric for at least some of the plurality of overlay targets based on the metrology data, wherein the reference metric is associated with one or more properties of the respective overlay targets that contributes to overlay error;
classifying the plurality of overlay targets into one or more groups based on the reference metrics calculated for the plurality of overlay targets;
generating a reference image for at least some of the one or more groups;
generating corrected metrology data using the associated reference image for at least some of the one or more groups; and
generating overlay measurements for the plurality of overlay targets based on the corrected metrology data.