Mask variability with extraction of SEM image contour and area measurements

Abstract

This paper presents contour-based methods to assess mask variability. Mask certification depends on the measurement reliability and on criteria relevance. By now, ST and its maskshop partners rely mostly on CDSEM measurements for mask certification. However, this kind of metrology has limitations and, looking at the future, we think it would be timely to search for metrology which bypass those limitations. That is why we are looking at 2D metrology [1], especially to area and contour measurements [2] on SEM images using extracted contours. Thanks to the added value of 2D metrology, we expect to assess mask variability, mask uniformity and pattern fidelity. We also take the opportunity to compare the results on two FOVs (field of view) from the images provided by mask shops. Finally, we also intend to automate the whole measurement process to make it easier to use.