Using OPC to optimize for image slope and improve process window

We use the gradient of the image slope and gradient of the edge placement error (EPE) in order to improve both slope and EPE during OPC. The EPE gradient taken with respect to edge position is normally called MEEF or the MEEF matrix. Use of the gradient of image slope with respect to change in edge position was introduced by Granik as the “contrast matrix.” Whereas traditional OPC techniques focus on EPE alone (pattern fidelity), we broaden the scope of OPC to maximize slope for improved image robustness and to maximize process window.

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