IntenCD technology for fast and accurate scanner performance determination

Scanner performance is influenced by the quality of its illumination, mechanical and optical elements and the impact of these factors on the printed wafer. Isolation of the aggregated scanner errors from other sources of error on the printed wafer is a challenging task since the total error budget of the lithography process consists of many dynamic sources, such as wafer planarity and film stack properties. The mask is conceptually part of the scanner optics and integral to the imaging process. Therefore the mask error contribution to the overall error becomes relevant for any advanced lithography process. Discrete mask measurement techniques are currently used to create across mask CDU maps. By subtracting these maps from their final wafer measurement CDU map counterparts, it is possible to assess within certain limitations the real scanner induced printed errors. The current discrete measurement methods are time consuming and some overlook errors other than linewidth variations, such as transmission and phase variations, all of which influence the final printed CD variability. In this paper we present a methodology, which leverages Applied Materials Aera2™ mask inspection tool, based on a so-called IntenCD" technology. IntenCD aerial imaging produces maps by scanning the mask at high speed, offer full mask coverage and accurate assessment of all mask induced errors simultaneously, making it ideal for mask CDU characterization and scanner qualification.