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4 March 2008 Electrically driven optical proximity correction
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Existing optical proximity correction tools aim at minimizing edge placement errors (EPE) due to the optical and resist process by moving mask edges. However, in low-k1 lithography, especially at 45nm and beyond, printing perfect polygons is practically impossible to achieve in addition to incurring prohibitively high mask complexity and cost. Given the impossibility of perfect printing, we argue that aiming to reduce the error of electrical discrepancy between the ideal and the printed contours is a more reasonable strategy. In fact, we show that contours with non-minimal EPE may result in closer match to the desired electrical performance. Towards achieving this objective, we developed a new electrically driven OPC (ED-OPC) algorithm. The tool combines lithography simulation with an accurate contour-based model of shape electrical behavior to predict the on/off current through a transistor gate. The algorithm then guides edge movements to minimize the error in current, rather than in edge placement, between current values for printed and target shapes. The results on industrial 45nm SOI layouts using high-NA immersion lithography models show up to a 5% improvement in accuracy of timing over conventional OPC, while at the same time showing up to 50% reduction in mask complexity for gate regions. The results confirm that better timing accuracy can be achieved despite larger edge placement error.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shayak Banerjee, Praveen Elakkumanan, Lars W. Liebmann, James A. Culp, and Michael Orshansky "Electrically driven optical proximity correction", Proc. SPIE 6925, Design for Manufacturability through Design-Process Integration II, 69251W (4 March 2008);

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