INVESTIGATION OF CHEMICAL EFFECTS IN LITHOGRAPHY

It is well known that patterning materials are sensitive to many factors that determine lithography performance. For example, when the same resist is used with various underlayers optimized to the same optical distribution, the different underlayers can produce totally different outcomes. In addition to possible chemical effects (diffusion, acid/quencher interaction, etc.), molecular forces could help explain the entire phenomenon if a pattern profile is built up incorporating fluid dynamics simulation. Because current simulation tools do not take into account the molecular forces, comparing experimental data to simulation results can help isolate the effects of such forces. In this work, a full physics model of the PROLITH simulation tool was used to run simulations and to fit experimental lithography data. Experimental data were obtained from KrF contact holes patterned using two different underlayer materials. From this comparison, we can postulate that controlling molecular forces, such as surface tension, can help improve lithography performance beyond what simulation predicts. This approach allows for a potentially wider critical dimension (CD) process window by deviating from traditional lithography modeling. As patterning processes are developed to produce increasingly smaller feature sizes, molecular forces will have a greater effect on optical imaging and should be given more attention.