Image processing for on-cell overlay measurement

An on-cell overlay measurement system comprising:

• a scanning electron microscope configured to capture a plurality of SEM images of a semiconductor wafer on which a first pattern and a second pattern are disposed, wherein a relative positioning between the first pattern and the second pattern is based on overlay settings;
• a parameter optimizer configured to receive the plurality of SEM images from the scanning electron microscope and to transmit a parameter set and the plurality of SEM images to an overlay measurement device;
• and
• the overlay measurement device, wherein the overlay measurement device is configured to generate overlay information of the plurality of SEM images based on the parameter set and the plurality of SEM images,
• wherein the parameter optimizer is configured to:
• determine a primary optimization parameter set based on the overlay settings and based on the overlay information of the plurality of SEM images, the primary optimization parameter set comprising one or more image processing parameters;
• cluster the plurality of SEM images in a plurality of clusters based on image attributes of the plurality of SEM images;
• and
• determine a secondary optimization parameter set corresponding to each of the plurality of clusters based on the primary optimization parameter set, based on the overlay settings, and based on overlay information of SEM images included in the cluster.

An on-cell overlay measurement method comprising:

• forming a first pattern and a second pattern in a semiconductor wafer based on overlay settings;
• capturing a plurality of SEM images associated with a plurality of positions of the semiconductor wafer;
• determining a primary optimization parameter set based on the plurality of SEM images, the primary optimization parameter set comprising one or more image processing parameters;
• clustering the plurality of SEM images into a plurality of clusters based on image attributes of the plurality of SEM images;
• determining a secondary optimization parameter set corresponding to each of the plurality of clusters based on SEM images included in each of the plurality of clusters and based on the primary optimization parameter set;
• and
• measuring an overlay of each of the plurality of SEM images using the secondary optimization parameter set corresponding to each of the plurality of clusters.