Simulations for the optimization of immersion photolithography processes

Simulations for the optimization of immersion photolithography processes: This report provides the description of the work carried on in the laboratory of the Computational Lithography Group at CEA - Leti in Grenoble. The work consisted in the exploration of the possibilities of a new simulation software for the photolithography process called Dr.Litho and developed at Fraunhofer IISB. This software introduce a new way to implement photlithography simulations. In fact it has not any interface for the user, but he can build a specific script concatenating the Python functions provided by Fraunhofer in order to consider exactly all the aspects of the process he wants to take in to account. In particular this new simulator had been used to get information on the reflectivity of the photolithographic stack and, concerning the reflectivity, to address the optimization problem of the immersion photolithography. The results obtained had been validated by the outputs of simpler open-source software. In particular the new simulator uses as resolution method the Transfer Matrix Method, while for instance one of the open-source software used Rigorous Coupled Wave Analyse. Also Dr.Litho had been exploited to show the phenomenon of the standing waves in the bulk image inside the photoresist and the role that the layers can have to limit this phenomenon, a problem for the critical dimension of the photlithography scanner. The final result of this work is the composition of a series of scripts in Python that have as output the results mentioned and that can make easier the simulation flow for future progression in the immersion technique field. All the details and the aspects of the immersion photolithography process that are fundamental to understand the practical work done are firstly presented by a deep bibliographic study.