News and New Products

Clear Shape introduces model-based DFM platform

By Michael Santarini, Senior Editor -- EDN, 11/27/2006 12:35:00 PM

EDA startup Clear Shape Technologies, the worst-kept secret in the DFM (design for manufacturability) space, is finally formally announcing itself and its two DFM tools this week.

The company was founded in 2003 by industry veterans Atul Sharan (Clear Shape's CEO), Yao-Ting Wang (chairman and CTO), and Fang-Cheng Chang (vice president of engineering) with the idea that advanced process technologies at 65 nm and below will require model-based physical verification, not just rule-based DRC (design rule checking).

"We've been around for three years now and haven't announced ourselves until now because DFM requires complex engagements," Sharan says. "You have to get validated in the fabs and create a tool that is production-ready."

Indeed, the company's tools have already been endorsed by the three largest fabless companies offering 65-nm technologies: TSMC, UMC, and the common process alliance of Chartered Semiconductor, IBM, and Samsung. Qualcomm, NEC, and an unnamed big "fabless company" are currently using the tools. The unnamed entity is likely ATI, which is quoted in the company's press materials.

Sharan says that while most vendors offering DFM tools claim that IC designers are actually using their tools, most tools actually find use with mask-data-prep engineers, mask makers, or the foundries themselves. Sharan notes that many of the "DFM companies" that Synopsys, Cadence, and Mentor acquired last year actually fix OPC (optical proximity correction) and PSM (phase-shift mask) tools used in the mask-making process.

Clear Shape's tools, according to Sharan, are true DFM tools, as they bring process models of lithography, RET (resolution enhancement technology), OPC, CMP (chemical mechanical polishing), mask, etch, interconnect parasitics, and transistor modeling to physical design and verification to help IC designers ensure what they have designed can really be manufactured by the fab they are targeting.

Clear Shape's tools center around a patent-pending, model-based, nonlinear optical-transformation algorithm. "What we do is give the designer the ability to go from ideal GDSII to actual predictive silicon based design," Sharan says. "We've created a platform to essentially manage all aspects of variability as they effect design. The primary causes of variability arise from the technology or process issues from the process side. Those have to be comprehended and then you have to account for variability on every axis: timing, leakage power, signal integrity, and of course catastrophic failures."

The Clear Shape platform currently includes two tools: Outperform and InShape.

Cell, IP, custom-analog, and cell-based digital designers can use OutPerform during physical design. Cell-based chip designers input their DEF, SPEF, library information, and fab DFM technology files into OutPerform. The tool then identifies timing and leakage parametric hotspots for violations due to systematic variations. The tool also calculates the change in delay and timing skew based on the in-context shape variations and provides delay variations back to static-timing-analysis tools in the form of an incremental SDF.

For custom and analog flows, users will feed the tool a Spice netlist and Spice models. The tool then predicts current density across channels, extracting transistor parameters for transistors from the embedded InShape model-based silicon contour prediction engine. The tool then produces a back-annotated transistor Spice netlist and applies the changes in RC data to the designer’s existing DSPF or SPEF file to represent the true effects of in-context silicon shape variations, without creating new nodes or parasitic elements. Designers can then simulate the back-annotated transistor Spice netlist with their Spice simulator to check the effect of variations on their design and detect potential failures before going to silicon.

InShape is, in effect, a full-chip DRC/LVS double checker, which catches the problems that rules-based tools can't, according to Clear Shape. Where DRC and LVS tools confirm that a design conforms to an ever-growing set of foundry rules for a given process, InShape actually checks each layer of a design (checks the GDSII) to ensure elements conform to actual fab process models.

The idea is that rule-based engines simply apply an ever-growing list of rules across an entire design and do not account for "in-context" or situational issues that may or may not impact every design, says the company's vice president of marketing, Nitin Deo. "Today, in the absence of knowing what the design is going to look like, you can have a design that is DRC-clean, but what you get is silicon that encounters catastrophic failures and parametric failures," Sharan says. "And, no matter what you do, your design is going to be centered over-pessimistically and your spread will be extremely wide."

During physical verification, designers will use InShape to scan their entire design—both device and interconnect—to identify structures that will cause problems in RET, OPC, mask, etch, and lithography downstream. The tool then automatically generates a set of "fixing guidelines" that designers can use to implement changes in third-party place-and-route tools. The tool can also produce a critical dimension report that designers can feed into OutPerform.

Sharan stresses that the tool doesn’t create rigid guidelines, rather it produces a DFM hotspot list and ranks issues—opens and shorts, contact coverage, gate variability, and line-end pull-back in the designers’ original layout—by type and criticality.

Designers can also use the tool's contour-prediction features proactively to do "what-if" analysis.

Cadence has integrated the Clear Shape tools into its flow and Cadence's (and U.C. Berkeley's) Alberto Sangiovanni-Vincentelli sits on Clear Shape's advisory board. So don't be surprised if Cadence acquires the company, which has thus far raised more than $10 million in venture funding, some of which came from Cadence via its now defunct Telos Ventures VC arm. Clear Shape currently has 35 employees.

Pricing for OutPerform and InShape starts at $300,000 each, per master license, per year.