SEM-contour based mask modeling

With the push toward the 32nm node, OPC modeling must respond in kind with additional accuracy enhancements. One area of lithographic modeling that has basically gone unchecked is mask fidelity. Mask linearity is typically built into the OPC model since the calibration data contain this information, but mask pattern fidelity is almost impossible to quantify for OPC modeling. Mask fidelity is the rounding and smoothing of the mask features relative to the post-OPC layout intent, and there is no robust metric available to quantify these effects. With the introduction of contour-based model calibration, mask fidelity modeling is possible. This work evaluates techniques to quantify mask modeling and methods to gauge the accuracy improvement that mask fidelity modeling would project into the lithographic process using contour-based mask model calibration.