Startup seeks litho-friendly 'route' to success Richard Goering EE Times (06/26/2007 1:04 H EDT) Three IC routing developers have taken on a big challenge — replacing today's IC routers with a "correct by construction" approach that claims to eliminate lithography hot spots. In so doing, the founders of startup Lizotech Inc. are charting an approach to design for manufacturability (DFM) based on prevention rather than repair. Lizotech (Sunnyvale, Calif.) is currently going into beta sites with LithoRoute, a "litho friendly" router developed over the past two years by the company's founders. The router, which combines global, track, and detailed routing, claims to not only eliminate lithography hot spots but to reduce via counts by 30 percent compared to existing offerings. "We think there is a break in the router market," said Frank Lien, Lizotech co-founder, president and CEO. "Existing routers are too old. At 45 nm, there will be so many lithography hot spots that a fixing model won't work. It will have to be correct by construction." Lien was previously a fellow at Actel Corp., where he also served as vice-president of engineering for Actel's SRAM products. He founded Lizotech in 2005 with Min-Chen Zhao, vice president of engineering, who was formerly an engineer at Cadence Design Systems, Mentor Graphics and Actel. Lien and Zhao developed LithoRoute along with Ching-Liang Tseng, who formerly worked at Avanti Corp. and Mentor Graphics. Today, Lizotech consists of three full-time and three-part time employees, and the company has raised less than a million dollars in angel funding. Despite its small size, the company is actively seeking beta customers and expects to have production-ready software in a month or two, Lien said. The vision is large. Many of today's DFM tools focus on identifying and repairing lithography hot spots, where layout structures may cause problems for optical proximity correction (OPC) and manufacturing tools. Lizotech's goal, said Lien, is that LithoRoute will produce layouts with no hot spots that require this type of repair. LithoRoute includes a calculating engine that takes information extracted from a lithography model as arguments. It then guides the router towards routing patterns that are free of lithography hotspots. The same lithography model helps reduce the number of critical routing features such as turns, line ends, and vias, thus improving variability and yield in the design. "We have something built into our router code which is unique that allows us to do a very quick calculation," Lien said. "This puts us ahead of everyone else." With the quick calculation, Lien said, the run-time impact of the correct-by-construction approach is minimal — "I would say less than one percent." He said there's no observable impact on area or performance. According to Lien, benchmark results show that LithoRoute can consistently produce layouts with a 2 percent wirelength reduction and, more significantly, a 30 percent via count reduction compared to existing routers. The via count reduction, Lien said, translates into lower resistance and improved timing closure. LithoRoute does require some proprietary information from foundries, but it's encoded into the router and does not need to be provided by the user, Lien said. As of now, he acknowledged, the company doesn't have any formal partnerships with foundries. Lizotech supports 65 nm and 45 nm design rule checks including variable spacing, variable width, same net spacing, and influence rules. LithoRoute plugs into OpenAccess databases and accepts inputs in LEF/DEF design formats. As such, it claims to integrate easily with existing design flows. Lien said Lizotech has tried LithoRoute in Cadence Design Systems and Synopsys flows, although not yet with Magma Design Automation's flow. LithoRoute is a grid-based Manhattan router. The data structure employs a hybrid of grid models, where different grid models are used at different phases of the routing. Its global routing uses a multi-level data representation scheme. Its track routing divides the problem into routing layers and lanes. Its detailed routing further divides the design into small partitions. To support parallel processing over a network, LithoRoute uses the public-domain Open MPI package. The router also provides an incremental capability for engineering change orders. As a small company, Lien said, "we are going to take one customer at a time." Lizotech is looking to expand its field applications engineering and EDA development staff. The company's immediate goal, Lien said, is simply to get a "really good router" out into the market. http://www.eetimes.com/news/design/showArticle.jhtml?articleID=200000767 --

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