Evaluation of Particle Protection Capability of Extreme Ultraviolet Lithography Mask Carrier in Vacuum Transfer by Experiment and Calculation

概要

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In extreme ultraviolet lithography (EUVL), particle-free mask handling is a critical issue. We have studied particle protection capability of a dual pod, which consists of an outer pod and an inner pod that holds the mask. Our experiment and calculation demonstrated that a dual pod prevents particle addition in a quality area of $142\times 142$ mm2 at the center of the mask, because particles entering the inner pod stopped near the edges. Our experiments showed 8 particle adders (${\geq}46$-nm polystyrene latex particle equivalent) for 1850-cycle transfer tests, and the dual pod satisfied the pre-production tool specification. Our measurement repeatability was $0.0015(\sigma)$/cycle with a binominal distribution; however, we found that the accuracy was insufficient for an estimated specification of a high-volume machine. We discussed the necessary handling cycles and a method to improve repeatability by inspecting the area outside the quality area.
2011-09-25