Understanding the Impact of Rigorous Mask Effects in the Presence of Empirical Process Models Used in Optical Proximity Correction (OPC)
This paper discusses some practical aspects of integrating a mask modeling solution into the Optical Proximity Correction (OPC) framework. Specifically, investigations were performed to understand to what degree empirical process models used in OPC can compensate for mask effects when a Kirchhoff mask model is used. It is shown that both Constant Threshold Resist (CTR) models, as well as more complex variable threshold process models, can compensate for mask effects at a single plane of focus. However, when looking through process window, neither process model can predict the focal behavior of Electro-Magnetic Field (EMF) simulators. The impact of mask effects will therefore need to be modeled in OPC, since process models cannot fully compensate for their effects. Heuristic approaches to modeling mask effects and the impact of optical diameter (periodic boundary conditions) are also investigated. Finally, a Kirchhoff mask model and a DDM mask model are compared to see which mask model more accurately explains experimental CD measurement data from a 65nm process.
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