Patent ID: 11921052
Assignee: KLA CORPORATION
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G  H

Claim 34:
35. An inspection system comprising:
an imaging sub-system including an illumination source and a detector configured to image a sample; and
a controller communicatively coupled to the imaging sub-system, the controller including one or more processors configured to execute program instructions causing the one or more processors to implement an inspection recipe by:
receiving first-step images of a plurality of sample regions after a first process step from the imaging sub-system;
receiving second-step images of the plurality of sample regions after a second process step, wherein the second process step modifies the sample in at least one of the plurality of sample regions from the imaging sub-system;
identifying one of the plurality of sample regions as a test region and at least some of the remaining sample regions as comparison regions, wherein the second-step image of the test region is a test image and the second-step images of the comparison regions are comparison images;
generating a multi-step difference image by a weighted subtraction of a combination of at least one of the second-step comparison images and at least two of the first-step images from the test image; and
identifying defects in the test region associated with the second process step based on the multi-step difference image.