Gate imaging for 0.09μm logic technology:: comparison of single exposure with assist bars and the CODE approach

In order to address some specific issues related to gate level printing of the 0.09mum logic process, the following mask and illumination solutions have been evaluated. Annular and Quasar illumination using binary mask with assist feature and the CODE (Complementary Double Exposure) technique. Two different linewidths have been targeted after lithography: 100nm and 80nm respectively for low-power and high-speed applications. The different solutions have been compared for their printing performance through pitch for EL (Energy Latitude), DOF (Depth of Focus) and MEEF (Mask Error Enhancement Factor). The assist bar printability and line-end control was also determined. For printing the 100nm target, all tested options can be used, with a preference for Quasar illumination for the gain in Depth of Focus and MEEF. For the 80nm target however, only the CODE technique with Quasar give sufficient good results for the critical litho parameters.