Modeling and experiments of non-telecentric thick mask effects for EUV lithography

Abstract

Various issues related to non-telecentric mask effects for EUV lithography will be discussed in this paper. First, a raytracing approach will provide a conceptual description as to the nature of non-telecentric thick mask effects, highlighting the behavior of various edge types and corners. Rigorous modeling of these effects are discussed along with a few consequences of improper modeling. A series of simulation and experimental studies are presented to probe both the one- and two-dimensional impact of thick mask effects. It will be shown that a simple constant edge bias appears sufficient for ID features, but begins to break down when space-widths are less than about 45 nm. Investigation into the impact of comers and small 2D features indicates that a simple edge-based bias also breaks down for edge lengths less than about 60nm. A sample set of rules-based post-OPC HV corrections for 22nm node dimensions are proposed, although based on experimental results, it is concluded that more accurate resist modeling and scanner stability are required before being able to precisely predict and control HV effects. Finally, with some simplifying assumptions, simulation is used to predict the extent of potential HV effects of future EUV imaging systems. © 2009 SPIE.