Study on the Data Trend of Pitch Line with Pupilgram

For the moment, OPC is mainly model-based, which means an accurate, stable, predictive model is vital for chip manufacture. To achieve an applicable model, it is necessary to understand the data used for model calibration. Pitch line is one of key test patterns. Going against intuition, its ADI cd usually decreases first and then increases with the increase of pitch, finally approaching a nearly constant value. Also, the slope of CD v.s. pitch curve shows non-monotonous behavior during the process of CD decreasing. Here, we present a thorough explanation on the data trend with pupilgram. The results show that the change of data slope originates from the distribution alteration of light diffraction orders inside pupil. In addition, the effect of source shape, NA value and mask tone on data trend is presented. Our results here provide meaningful knowledge of data trend and help to obtain a more accurate OPC model.