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Lithography aware physical design and layout optimization for manufacturabilityGao, Jhih-Rong 25 June 2014 (has links)
As technology continues to scale down, semiconductor manufacturing with 193nm lithography is greatly challenging because the required half pitch size is beyond the resolution limit. In order to bridge the gap between design requirements and manufacturing limitations, various resolution enhancement techniques have been proposed to avoid potentially problematic patterns and to improve product yield. In addition, co-optimization between design performance and manufacturability can further provide flexible and significant yield improvement, and it has become necessary for advanced technology nodes. This dissertation presents the methodologies to consider the lithography impact in different design stages to improve layout manufacturability. Double Patterning Lithography (DPL) has been a promising solution for sub-22nm node volume production. Among DPL techniques, self-aligned double patterning (SADP) provides good overlay controllability when two masks are not aligned perfectly. However, SADP process places several limitations on design flexibility and still exists many challenges in physical design stages. Starting from the early design stage, we analyze the standard cell designs and construct a set of SADP-aware cell placement candidates, and show that placement legalization based on this SADP awareness information can effectively resolve DPL conflicts. In the detailed routing stage, we propose a new routing cost formulation based on SADP-compliant routing guidelines, and achieve routing and layout decomposition simultaneously. In the case that limited routing perturbation is allowed, we propose a post-routing flow based on lithography simulation and lithography-aware design rules. Both routing methods, one in detailed routing stage and one in post routing stage, reduce DPL conflicts/violations significantly with negligible wire length impact. In the layout decomposition stage, layout modification is restricted and thus the manufacturability is even harder to guaranteed. By taking the advantage of complementary lithography, we present a new layout decomposition approach with e-beam cutting, which optimizes SADP overlay error and e-beam lithography throughput simultaneously. After the mask layout is defined, optical proximity correction (OPC) is one of the resolution enhancement techniques that is commonly required to compensate the image distortion from the lithography process. We propose an inverse lithography technique to solve the OPC problem considering design target and process window co-optimization. Our mask optimization is pixel based and thus can enable better contour fidelity. In the final physical verification stage, a complex and time-consuming lithography simulation needs to be performed to identify faulty patterns. We provide a classification method based on support vector machine and principle component analysis that detects lithographic hotspots efficiently and accurately. / text
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Lithography variability driven cell characterization and layout optimization for manufacturabilityBan, Yong Chan 31 May 2011 (has links)
Standard cells are fundamental circuit building blocks designed at very early design stages. Nanometer standard cells are prone to lithography proximity and process variations. How to design robust cells under variations plays a crucial role in the overall circuit performance and yield. This dissertation studies five related research topics in design and manufacturing co-optimization in nanometer standard cells. First, a comprehensive sensitivity metric, which seamlessly incorporates effects from device criticality, lithographic proximity, and process variations, is proposed. The dissertation develops first-order models to compute these sensitivities, and perform robust poly and active layout optimization by minimizing the total delay sensitivity to reduce the delay under the nominal process condition and by minimizing the performance gap between the fastest and the slowest delay corners. Second, a new equivalent source/drain (S/D) contact resistance model, which accurately calculates contact resistances from contact area, contact position, and contact shape, is proposed. Based on the impact of contact resistance on the saturation current, robust S/D contact layout optimization by minimizing the lithography variation as well as by maximizing the saturation current without any leakage penalty is performed. Third, this dissertation describes the first layout decomposition methods of spacer-type self-aligned double pattering (SADP) lithography for complex 2D layouts. The favored type of SADP for complex logic interconnects is a two-mask approach using a core mask and a trim mask. This dissertation describes methods for automatically choosing and optimizing the manufacturability of base core mask patterns, generating assist core patterns, and optimizing trim mask patterns to accomplish high quality layout decomposition in SADP process. Fourth, a new cell characterization methodology, which considers a random (line-edge roughness) LER variation to estimate the device performance of a sub-45nm design, is presented. The thesis systematically analyzes the random LER by taking the impact on circuit performance due to LER variation into consideration and suggests the maximum tolerance of LER to minimize the performance degradation. Finally, this dissertation proposes a design aware LER model which claims that LER is highly related to the lithographic aerial image fidelity and the neighboring geometric proximity. With a new LER model, robust LER aware poly layout optimization to minimize the leakage power is performed. / text
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