Defect improvement for an EUV process

For generations lithographers have worked to overcome the difficulties associated with defect mitigation, and since EUV lithography has become mature enough for HVM this concern is warranting ever increasing attention to make such processes profitable. Even though much of the EUV defect effort is focused on stochastic defects, in this work we attempt to assess and understand process defects associated with the interaction between different films in an EUV stack. By understanding the behavior of specific underlayer materials and their chemistry within a given environment we have attempted to tune the surface energies to match the photoresist in the stack. With the correct process changes being applied, we have then worked to correlate the proper matching of surface energies with process defects. The current focus of our work is specifically line collapse, and we believe that developing a fuller understanding of the film interactions will ultimately lead to a more robust EUV process for HVM. We hereby present our work utilizing the SCREEN DUO coat develop track system with an ASML NXE:3300 in the imec Leuven cleanroom facility.