Patent ID: 11914290
Assignee: KLA CORPORATION
Field: Optics (Instruments)
Classification: CPC G  H | IPC G  H

Claim 10:
11. A method comprising:
providing a device that includes:
a mat in a device area having four sides, wherein the mat includes at least a first layer of photoresist and a second layer of photoresist disposed on the first layer;
a plurality of extensions in the first layer that extend beyond the sides of the mat, wherein each of the extensions in the first layer includes a first layer metrology target, and wherein the first layer metrology targets have a relaxed pitch less than a device pitch in the second layer of the mat; and
wherein the second layer defines a pattern of apertures and the second layer covers at least part of each of the first layer metrology targets;

obtaining an image of at least one of the first layer overlay targets with an electron beam metrology tool, wherein the obtaining includes simultaneously obtaining a secondary electron image of the second layer and obtaining a back-scattered electron image of the first layer with the relaxed pitch; and
performing, using a processor, metrology with the image.