Compensating for image placement errors induced during the fabrication and chucking of EUVL masks

With the stringent requirements on image placement (IP) errors in the sub-65-nm regime, all sources of mask distortion during fabrication and usage must be minimized or corrected. For extreme ultraviolet lithography, the nonflatness of the mask is critical as well, due to the nontelecentric illumination during exposure. This paper outlines a procedure to predict the IP errors induced on the mask during the fabrication processing, e-beam tool chucking, and exposure tool chucking. Finite element (FE) models are used to simulate the out-of-plane and in-plane distortions at each load step. The FE results are compiled to produce a set of Correction Tables that can be implemented during e-beam writing to compensate for these distortions and significantly increase IP accuracy. A previous version of this paper appeared in the Proceedings of the European Mask and Lithography Conference (EMLC), SPIE, 6533, 653314 (2007). The paper has been updated, retitled, and published here as a result of winning the Best Paper Award at the EMLC.