cqvip:As the process comes into 28nm node and below,lithography struggles stronger between high resolution (high NA) and enough process window especially for hole layers (Contacts and Vias).Taking more care of process window may result in lower image quality of structures and bigger uncertainty in OPC model accuracy.Besides,it is difficult to cover all kinds of test structures within acceptable accuracy in one OPC model because of distinct difference of image quality of different patterns.To solve these problems,this paper introduces an innovative method of applying multi-models in one layer OPC.According to different characteristic features,multiple models are applied respectively and the fitting on these features with poor resolution can be improved by re-optimizing based on related model.A practice for 28 nm Via layer modeling calibration is given,and it shows an evident improvement of model accuracy through the implementing of multiple models scheme.
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