Disclosed arc methods, systems, and computer software for generating a mask design. A method can include obtaining an initial OPC pattern contour resulting from an OPC process and determining a set of selected points on the initial OPC pattern contour. Metrics can be calculated that describe arcs between the selected points along the initial OPC pattern contour and a recovery location can be determined based on the calculation of the metrics. A recovered OPC pattern can be generated based on the recovery location In some variations, the method can include modifying a portion of the initial OPC pattern contour at a recovery location based on an arc length between selected points on the initial OPC pattern contour. The method can also include joining or separating a portion of the initial OPC pattern contour at a recovery location where a distance between opposing points on the initial OPC pattern contour is a minimum.In other variations, the method can include changing intensities of pixels at the recovery location in a mask image corresponding to the initial OPC pattern contour, where the recovered OPC pattern can be generated based on the mask image with the changed pixels. For example, the intensities of the pixels can be changed to be closer to internal intensities of pixels inside the initial OPC pattern contour and/or changed to be closer to external intensities of pixels outside the initial OPC pattern contour. The intensities of the pixels can be changed in a region surrounding the recovery location.In yet other variations, the method can include determining sample points on a Manhattan target pattern and generating the selected points along the initial OPC pattern contour by projecting the sample points on the Manhattan target pattern up to a threshold distance. This can include performing corner rounding on the Manhattan target pattern, where the sample points can be on the Manhattan target pattern after the corner rounding.
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