Illumination optimization has become crucial at smaller design nodes in order to achieve viable process margins. Although illumination optimization is classically performed to maximize the common process window for features in a design, there have been other advantages observed as a result of using an optimal illumination condition. Some of these benefits include overall reduction in cost of ownership averted due to OPC complexity and run-time [2,3]. With the current trend of double exposure or double patterning which has been determined to be cost effective along with other issues [4], more efforts are made on RET for design specific solutions.

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