Lithographic manufacturing robustness analysis for as drawn patterns

A new pattern analysis concept, referred to as a focus sensitivity model, has one output IΔ that identifies pattern components that are difficult to manufacture during photolithography. IΔ uses the change in modelled intensity with respect to defocus to rapidly determining if a pattern can be robustly manufactured. This paper will demonstrate that the IΔ model output can also be used on patterns without OPC to identify the same manufacturing characteristics found on a pattern that incorporates OPC. This is demonstrated by showing that OPC makes minor changes to the high spatial frequency components of a pattern.Current results show the IΔ analysis of a pattern that has OPC and the same pattern with no OPC is nearly qualitatively identical. The quantitative differences between the two outputs can be removed by changing the IΔ threshold value that is used to quantify pattern quality. However, the spatial frequency changes generated by other RET such as SRAFs is too large and non-linear to be compensated for with a simple change in the IΔ trigger threshold. The ability to remove the OPC correction set from pattern robustness analysis provides a significant advantage; even with the need to use other RET during robustness analysis.