New method to determine process window considering pattern failure

In this paper, new metric, acid concentration distribution image log slope (AILS) is suggested to predict pattern failure in photo lithography. By introducing AILS, pattern fidelity can be determined as numbers. With evaluating at the top 10% and bottom 10% of photo resist, various kinds of pattern failures are categorized and they can be predicted to be failed or not. The simulation results are compared with wafer experiment results and shows great prediction accuracy. In order to evaluate hot spot regarding pattern failure in all possible pitch and duty ratio, in-house image quality analysis tool is used and compared with wafer experimental results. Minimum normalized AILS (NAILS) to cause pattern bridge is larger than that to cause lift off. Both pattern failures are dependent of AILS and CD but the effect of CD on pattern failure is stronger than AILS's