Optimization Of Double Patterning Split By Analyzing Diffractive Orders In The Pupil Plane

In double patterning technology (DPT), two adjacent features must be assigned opposite colors, corresponding to different exposures if their pitch is less than a predefined minimum coloring pitch. However, certain design orientations for which pattern features separated by more than the minimum coloring pitch cannot be imaged with either of the two exposures. In such cases, there are no aerial images formed because in these directions there are no constructive interferences between diffractive orders in the pupil plane. The 22nm and 16nm nodes require the use of pixelized sources that will be generated using SMO (source mask co-optimization). Such pixelized sources while helpful in improving the contrast for selected configurations can lead to degraded contrast for configurations which have not been set during the SMO process. Therefore, we analyze the diffractive orders interactions in the pupil plane in order to detect limited orientations in the design and thus propose a decomposition to overcome the problem.