Tool advises designers on soft-error risk

French EDA startup iRoC Technologies this week will release TFIT, a tool that allows custom chip and cell designers to analyze the impact of soft-error strikes on their designs.

Soft errors—transient faults caused by external radiation, mainly cosmic rays but also alpha particles from silicon and package materials—affect the function of memories and complex ICs. Soft errors occur when such radiation causes a large enough charge disturbance to reverse data states in registers, latches, and flip flops. The FIT in TFIT stands for the hard reliability measure of failure in time. A single FIT is equal to one failure in 10⁹ device hours.

Traditionally, only military and aerospace designers had to beware of soft errors. However, Michael Buehler-Garcia, iRoC's vice president of worldwide marketing and business development, said the simultaneous push to finer process geometries, higher speeds, and lower power in commercial applications has made soft errors a growing concern for mainstream designers.

Earlier in the year, IRoC released its first technology for standard-cell designers, called SoCFIT (System on Chip FIT). The new TFIT product targets developers of custom ICs and silicon libraries.

TFIT is advisory software that comes bundled with hundreds of soft-error models. The tool will allow users to discover what radiation events their design will likely encounter and what the result will be. Up until now, full-custom chip and cell designers traditionally used TCAD (Technology CAD) tools and Spice simulation to perform soft-error analysis, Buehler-Garcia said.

"The TCAD software said, 'Give me the data you want, and I'll run a simulation against your Spice netlist and tell you the results,'" Buehler-Garcia said. "But TCAD tools aren't inherently soft-error-aware."

The TCAD method alone can be effective for soft-error analysis, but users had to test every single event condition—each type of radiation at every possible angle of radiation bombardment—to ensure that their designs were resistant to soft errors. Testing a single radiation event from all angles could take a day's worth of simulation; testing all types from all angles in Spice would take weeks or months, Buehler-Garcia claimed.

Designers working under military contracts had it slightly easier in that many military contractors would provide custom models that narrowed the simulation field to the type of radiation events and angles of bombardment likely to occur in a specific application.

Now with TFIT, iRoC is essentially offering these types of models for commercial applications. The first models, Buehler-Garcia said, address the networking and communications space.

To use the tool, users feed an IP block or part of their design to TFIT. The tool then outputs a statistical "bucketized" profile of soft-error probabilities, which alerts the designer to which types of strikes pose a threat to the specified design.

Users can then select where on their design they would like a radiation event to occur. The tool, in conjunction with commercial Spice simulation, then performs analysis using the designer's test bench and iRoC's proprietary soft-error models. TFIT provides the results in tabular form or as a current curve displayed on the designer's SPICE simulator. Using these data, users can then determine whether a certain type of strike at a particular place in the design will cause a state change.

The tool currently supports Cadence but will soon support Synopsys and Silvaco as well, Buehler-Garcia said. TFIT starts at $50,000 for a single time-based license.