Optimization of equipment for 193-nm immersion processing

For immersion lithography at 193 nm, there is concern that the immersion of resist in water during exposure might cause water to penetrate the resist or resist components to dissolve into water, or that water remaining after exposure might affect subsequent processes. It is also thought that the same concerns are likely to be felt even if using a protective top coat. In this paper, we report on three key findings. First, after immersing resist in water using virtual immersion methods and evaluating the effect of water on critical dimension (CD) and defects, it was found that CD changes and defects increase. Second, as a result of performing the same evaluation when using a top coat, it was found that CD changes and defects increase despite top-coat application. Finally, a significant amount of knowledge can be obtained for the development of optimal 193-nm immersion lithography equipment as a result of wafer processing using real inline tools for immersion exposure and coating/developing.