Evaluation of protection schemes for extreme ultraviolet lithography (EUVL) masks against top–down aerosol flow

Extreme ultraviolet lithography (EUVL) is considered as the next generation lithography for 32-nm-node or smaller in semiconductor manufacturing. One of the challenges is to protect the EUVL masks against particle contamination, due to the unavailability of conventional pellicles. In this study, the EUVL mask protection schemes of Asbach et al. (2006. Technical note: Concepts for protection of EUVL masks from particle contamination. Journal of Nanoparticle Research, 8, 705–708), who proposed to mount the mask upside-down, have a cover plate with particle trap and apply phoretic forces, were evaluated against top–down aerosol at atmospheric pressure. Experimental evaluation was performed using 150 mm wafers as witness plates, and PSL particles ranging from 125 to 700 nm. For the numerical assessment of the protection schemes against particles between 10 and 3000 nm, a statistical method using a Lagrangian particle tracking simulation tool was employed to calculate the deposition velocity. It was shown that the critical surface could effectively be protected against top–down aerosol.