Is there a need for a new standards effort that would let chip makers use IC test data for yield improvement? Michael Campbell, vice president of engineering at Qualcomm, would be a likely supporter.

"By having a better link from the design to the fab to test, we can improve our ability to optimize yields faster," Campbell said. Today, he noted, there's no way to take output from a tester and correlate a scan failure with a hot spot on the IC layout using design-for-manufacturability (DFM) tools.

Standards would provide the "big- gest bang for the buck" for solving the problem, Campbell said. But it's not a simple issue.

There are many testers, and failure data from them would need to be made usable by EDA, DFM and yield management tools from multiple vendors. Those tools have their own interfaces and ways of interpreting test data.

Lessons from PS3

The Accellera standards organization has tackled part of the problem through the recent approval of the Open Compression Interface (OCI), which will allow users of one vendor's test compression tools to use automatic test pattern generation (ATPG) or yield diagnostic tools from another vendor. This effort was launched by the Accellera consortium after Nvidia designed a graphics processing unit for the Sony Playstation 3. Nvidia used Synopsys tools for test compression that turned out to be incompatible with the Cadence Design Systems tool that Sony used for yield diagnostics.

OCI helps, but it doesn't provide a standard semantics or syntax for leveraging test failure data for yield optimization. Several vendors, meanwhile, have come up with proprietary solutions. LogicVision's recent Yield Insight, for example, supports users of LogicVision's memory built-in self test (BIST). Synopsys now has a link between its TetraMax ATPG program and its Odyssey yield management system.

Can these kinds of links be extended into a standard so that anybody's scan or BIST data will work with anybody's yield improvement tools? The OCI experience is promising. With this effort, the four largest EDA vendors--Cadence, Synopsys, Mentor Graphics and Magma Design Automation--were able to set politics aside and work together to come up with a solution. Maybe the time has come to take a further step.