Mask corner chopping effect in OPC modeling

Mask corner chop (MCC) is a key indicator of mask quality, which impacts photoresist critical dimension (ADI CD) significantly. The effect of MCC on ADI CD has a strong correlation with pattern CD and lithographic process condition. This study employed an optimized OPC model to simulate the effect of MCC on ADI CD for a variety of patterns and lithographic process conditions. Our simulation results showed that the effect of MCC on ADI CD could be fit in a second-order equation. The second-order coefficient (`A´-coefficient) described the strength of the MCC effect. `A´-coefficient was correlated with the slope of the aerial image intensity at threshold (I_th), which could be expressed from negative to positive value with increasing I_th. In this paper, we also provided a method for the selection of illumination conditions based the MCC effect under various lithography processes.