Abstract: A design method of a photomask structure including the following steps is provided. A first layout pattern is provided. An assist pattern is added aside the first layout pattern. An optical proximity correction (OPC) is performed to convert the first layout pattern into a second layout pattern, wherein the assist pattern has an adjacent portion adjacent to the second layout pattern, a first distance between the adjacent portion and the second layout pattern is less than a safety distance, and the safety distance is a distance to prevent the assist pattern from being transferred to a photoresist layer during a lithography process. After the OPC is performed, the adjacent portion is shifted to increase the first distance to a second distance, wherein the second distance is greater than or equal to the safety distance.

Abstract: A method for detecting photolithographic hotspots is disclosed. After receiving layout data, an aerial image simulation is conducted to extract aerial image intensity indices. Based on the combination of one or more aerial image intensity indices, various aerial image detectors are generated. The value of aerial image detectors is verified to determine the position and type of the photolithographic hotspots.

Abstract: A method for detecting photolithographic hotspots is disclosed. After receiving layout data, an aerial image simulation is conducted to extract aerial image intensity indices. Based on the combination of one or more aerial image intensity indices, various aerial image detectors are generated. The value of aerial image detectors is verified to determine the position and type of the photolithographic hotspots.