20 March 2010 A study of reticle non-flatness induced image placement error contributions in EUV lithography
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Image placement (IP) and overlay error specifications are serious concerns for lithography at each successive technology node. Some of the primary contributors to image placement error (IPE) in EUV lithography are reticle and chuck surface non-flatness and chucking flatness non- uniformity. Flatness compensation has been proposed as a method to relax flatness specification for EUV substrates. However, in order for flatness compensation to work effectively, the various components of IPE i.e., reticle flattening and as-chucked z-height variation needs to be estimated accurately. Flatness compensation models assume a completely flat, rigid chuck and conformal clamping of the reticle backside. In this paper we will describe experiments designed to verify the different assumptions that the flatness compensation models are based on. The experiments involve printing wafers using a set of reticles of different flatness specifications on the ASML EUV Alpha Demo Tool (ADT) in Albany, NY. We will discuss results from these experiments and use Finite Element Modeling to simulate reticle chucking to correlate these results to physical properties electrostatic chuck on the ADT.
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Sudhar Raghunathan, Sudhar Raghunathan, Obert Wood, Obert Wood, Pradeep Vukkadala, Pradeep Vukkadala, Roxann Engelstad, Roxann Engelstad, Brian Lee, Brian Lee, Sander Bouten, Sander Bouten, Thomas Laursen, Thomas Laursen, John Zimmerman, John Zimmerman, Jaewoong Sohn, Jaewoong Sohn, John Hartley, John Hartley, "A study of reticle non-flatness induced image placement error contributions in EUV lithography", Proc. SPIE 7636, Extreme Ultraviolet (EUV) Lithography, 76360W (20 March 2010); doi: 10.1117/12.847107; https://doi.org/10.1117/12.847107

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