SCANNING DIFFRACTION-BASED OVERLAY SCATTEROMETRY

원문 (중국어)

An overlay metrology system includes a controller communicatively coupled to a first photodetector and a second photodetector. The controller may be configured to receive one or more signals from the first and second photodetector as an overlay target is scanned. The overlay target may include a plurality of measurement cells, where each measurement cell includes a grating-over-grating structure including a first-layer grating feature on a first layer of a sample and a second-layer grating feature on a second layer of the sample in an overlapping region. The first-layer grating feature and the second-layer grating feature may have a common pitch. The controller may be further configured to determine one or more differential signals between the first photodetector and the second photodetector for each measurement cell of the plurality of measurement cells and determine an overlay measurement based on the determined one or more differential signals.