Achieving CDU requirement for 90-nm technology node and beyond with advanced mask making process technology

For 90nm node and beyond technology generations, one of the most critical challenges is how to meet the local CD uniformity (proximity) and global CD uniformity (GCDU) requirements within the exposure field. Both of them must be well controlled in the mask making process: (1) proximity effect and, (2) exposure pattern loading effect, or the so-called e-beam "fogging effect". In this paper, we report a method to improve our global CDU by means of a long range fogging compensation together with the Leica SB350 MW. This exposure tool is operated at 50keV and 1nm design grid. The proximity correction is done by the software - package "PROXECCO" from PDF Solutions. We have developed a unique correction method to reduce the fogging effect in dependency of the pattern density of the mask. This allows us to meet our customers’ CDU specifications for the 90nm node and beyond.