Model-based DFM is the way to go, panelists agree By Ann Steffora Mutschler -- Electronic News, 1/31/2007 8:00:00 AM SANTA CLARA, CALIF. -- A panel of industry executives at this week's DesignCon tradeshow being held here agree that a model-based approach to design-for-manufacturing (DFM) results in better-yielding designs, compared to rule-based approaches. Cadence's Mike McAweeny, VP for DFM marketing, reminded that lithographic effects are compounded by variability in design, and that variability is dependent on the timing and power requirements. “With current, recommended rule-based approaches those rules are approaching thousands in number,” he said. “Common thinking says: The stricter the rules, the better the yield. What's better is to take a model-based approach and provide designers with insight into the effects of lithography and chemical mechanical planarization [CMP] into the design, along with impact of timing on litho and CMP, and then they can make tradeoffs.” Carlo Guardiani, senior director of DFM for PDF Solutions, agreed. “ Variability drives the proliferation of recommended design rules [RDR], however, at this level of technology, RET alone does not provide a process window that is large enough.” Therefore, he also suggests a model based approach for higher yields and faster design closure. At the same time, he believes “Designers don't love DFM for sure. Yield issues rarely come from design problems. Most of the time, designs are OK from the DFM point of view because we have made designers use a lot of margins; IP design is so robust; and there is so much guard-banding. “The problem now is that by adding too much guard-banding and too much margin, a lot of power and area is being wasted,” he explained. Craig West, director of applications for Toppan Photomasks, said, “What we've seen in the design community and with processor development is that designers choose to optimize simultaneously – design technologies have to be optimized for the mask technologies.” Next, Peter Rabkin, DFM program director at Xilinx, stressed the importance of iterative co-optimization of design, the process, along with OPC/RET and the masks, based on integrated and inter-dependent DFM tools. “We need to account for the impact of physical features on design in an electrical fashion. ... You cannot get yield without DFM,” he said. Once the panelists agreed that model-based DFM is the way to go, an audience member said, “Unless and until silicon manufacturers say their customers must run DFM, they won't do it.” TSMC North America's David Lan, senior manager for design methodology, responded, “In order to make designers accept the DFM concept, automation is key. People automatically accept things that are done automatically. Certain functions need to be integrated to get designs to accept DFM implementation.” As to whether foundries like TSMC will require customers to run DFM, Lan added carefully, “We think a lot about how to communicate to customers. Foundry managers try to understand how to get a good yield and how to tape-out correctly. But do we enforce them to do anything today? We haven't taken a firm position yet. ... We just say that we highly recommend it.” http://www.edn.com/article/CA6412194.html?partner=enews --

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