Mask pattern quality assurance based on lithography simulation with fine pixel SEM image

We evaluated the accuracy of the simulation based on mask edge extraction for mask pattern quality assurance. Edge extraction data were obtained from SEM images by use of TOPCON UR-6080 in which high resolution (pixel size of 2nm) and fine pixel SEM image (8000 x 8000 pixels) acquisition is possible. The repeatability of the edge extraction and its impact on wafer image simulation were studied for a normal 1D CD prediction and an edge placement error prediction. The reliability of the simulation was studied by comparing with actual experimental exposure results with an ArF scanner. In the normal 1D CD prediction, we successfully obtained good repeatability and reliability. In 65nm node, we can predict a wafer CD with the accuracy of less than 1 nm using the simulation based on mask edge extraction. In the edge placement error prediction mode, the simulation accuracy is ~5 nm including edge extraction repeatability and the uncertainty of lithography simulation model. The simulation with edge extraction more accurately predicts the resist pattern at line-end in which the actual mask pattern may be varied from the mask target (CAD) than a conventional simulation in which CAD is used as a mask pattern. This result supports the view that the wafer simulation with edge extraction is useful for mask pattern quality assurance because it can consider actual mask pattern shape.