When is a DRC error not an error?

By John Ferguson – Mentor, A Siemens Business

Error waivers are the dark matter of IC verification—they cancel out DRC errors in IC layouts. But ensuring waiver data is accurately recorded and stored for future use is essential to realizing their full value.

So – when is a DRC error not an error?

That’s a trick question…sort of. DRC errors are always errors, but sometimes they just don’t matter much. Maybe the error has such a minimal effect on yield or functionality that fixing it costs more than ignoring it. Maybe it’s the result of a complicated rule that can’t be run without generating a few false results. Whatever the reason, there’s a solution that’s been around for quite a while now…error waivers.

Error waivers are a way to let designers know they can safely ignore certain DRC error results. Of course, you can’t just waive any old error—both the foundry and design company have to agree that the error is insignificant in the scheme of things. While that used to happen on a one-by-one basis, that approach just isn’t practical any longer, especially for waivers associated with hard IP that is reused time and time again in multiple designs, or soft IP like SRAM.

Although we’ve found solutions for each new challenge in waiver management, the capture and storage of waiver data has become as complicated as the designs themselves. Who knows what’s outside our known universe? Want to know more about current waiver processing, and the ongoing efforts to predict and anticipate future challenges? Check out our white paper Dark matter, dark energy… What about dark errors? for a glimpse into the mysteries of the cosmos of IC design waivers.