High-precision contouring from SEM image in 32-nm lithography and beyond

We developed a new contouring technology that executes contour re-alignment based on a matching of the measured contour with the design data. By this 'secondary' pattern matching (the 'primary' being the pattern recognitions that is done by the SEM during the measurement itself), rotation errors and XY shifts are eliminated, placing the measured contour at the correct position in the design coordinates system. In the next phase, the developed method can generate an averaged contour from multiple SEM images of identical structures, or from plural contours that are aligned accurately by the algorithm we developed. When the developed contouring technology is compared with the conventional one, it minimizes contouring errors and pattern roughness effects to the minimum and enables contouring that represents the contour across the wafer. The Contour that represents the contour across the wafer we call "Measurement Based Averaged Contour" or MBAC. We will show that an OPC model that is built from these MBACs is more robust than an OPC model built from contours that did not get this additional re-alignment.