Rigorous model for registration error due to EUV reticle non-flatness and a proposed disposition and compensation technique - art. no. 65171N

The non-telecentricity of EUV lithography exposure systems translates into a very severe specification for EUV mask flatness that is typically 10 times tighter than the typical current specification for masks used in 193 run wavelength exposure systems. The mask contribution to the error budget for pattern placement dictates these specifications. EUV mask blank suppliers must meet this specification while simultaneously meeting the even more challenging specification for defects density. This paper suggests a process flow and correction methodology that could conceivably relax the flatness specification. The proposal does require that the proposed method of clamping the mask using an electrostatic chuck be accurate and reproducible. However, this is also a requirement of the current approach. In addition, this proposal requires the incorporation of an electrostatic chuck into a mask-shop metrology tool that precisely replicates the behavior of the chuck found in the EUV exposure tool.