Patent ID: 11874102
Assignee: KLA CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 8:
9. A system comprising:
a controller communicatively couplable to one or more metrology sub-systems, wherein the controller including one or more processors, wherein the one or more processors are configured to execute a set of program instructions maintained in memory when implementing a metrology recipe, wherein the set of program instructions is configured to cause the one or more processors to:
receive, from the one or more metrology sub-systems, one or more images indicative of illumination emanating from one or more metrology targets of a sample when implementing the metrology recipe, wherein the one or more metrology targets of the sample comprise:
a first target structure configured in accordance with the metrology recipe, wherein the first target structure is formed within at least one of a first area and a third area of a first layer of a sample, the first target structure comprising two or more first cells containing two or more first cell pattern elements arranged periodically; and
a second target structure configured in accordance with the metrology recipe, wherein the second target structure is formed within at least one of a second area and a fourth area of a second layer of the sample, the second target structure comprising two or more second cells containing two or more second cell pattern elements arranged periodically, wherein the second target structure is formed from a photoresist material with sufficient thickness to induce asymmetry in at least some of the second cell pattern elements when fabricated.

determine a center of gravity for each of the two or more first cells based on averaging individual center of gravity positions of each of the associated first cell pattern elements from the one or more images;
determine a center of gravity of the first layer based on averaging the centers of gravity for the two or more first cells;
determine a center of gravity for each of the two or more second cells based on averaging individual center of gravity positions of each of the associated second cell pattern elements from the one or more images;
determine a center of gravity of the second layer based on averaging the centers of gravity for the two or more second cells;
determine an overlay value of the sample by computing a difference between the center of gravity of the first layer and the center of gravity of the second layer.