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High-accuracy OPC-modeling by using advanced CD-SEM based contours in the next-generation lithography

OPC-modeling is traditionally based on CD-measurements. As design rules shrink, and process window become smaller, there is an unavoidable increase in the complexity of OPC/RET schemes required to enable design printability. The number of measurement points for OPC-modeling has increased to several hundred points per layer, and metrology requirements are no longer limited to simple one-dimensional measurements. Contour-based OPC-modeling has recently arisen as an alternative to the conventional CD-based method. In this paper, the technology of contour alignment and averaging was extended to arbitrary 2D structures. Furthermore the quality of SEM-contours was significantly improved in cases where the image has both horizontal and vertical edges (as is the case for most 2D structures), by a new SEM image method, which we call 'Fine SEM Edge'. OPC model calibration was done using SEM-contours from 2D structures. Then, the effectiveness of Contour-based calibration was examined by doing OPC model verification. The experimental results of the model quality with innovative SEM-contours with Fine SEM Edge (FSE) and Advanced alignment and averaging that was developed by Hitachi High-Technologies are reported. This combination of advanced alignment and averaging and FSE technologies makes the best use of the advantage of the contour-based OPC-modeling, and should be of use for the next generation lithography.