Patterning Material Challenges for Improving EUV Stochastics

As the industry looks to extend single-expose extreme ultraviolet (EUV) lithography, stochastic effects become a significant concern to enable yield. Multiple previously-published reports have shown a strong tradeoff between resist sensitivity and observed stochastic defectivity. However, the limits of this trade-off between improving stochastics-related defects with a higher dose resist remains to be understood. How strongly does the resist formulation itself contribute to stochastics, or is it a purely dose-driven effect? Due to the thickness decrease in the patterning stack, the interfacial effects of the resist and hardmask films play a dominant factor in the material stochastics. This offers an opportunity to think differently about underlayer design for sub-32nm pitch patterning. The choice of hardmask can be used to modulate post-litho defectivity to mitigate the stochastics effects and enable more efficient pattern transfer. This paper will address multiple approaches to improving the materials stochastics through resist component optimization and hardmask film development. The defectivity at post-exposure and post-etch are correlated to electrical yield to validate the evaluation. The relative merits of patterning a chemically amplified organic resist directly on an inorganic hardmask or having different types of organic adhesion promoters as an intermediate layer will be also be presented.