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Since process development kits (PDKs) are necessary for all IC design, a major change in the way foundry PDKs are provided is significant news. Such change may be forthcoming from the Silicon Integration Initiative (Si2) OpenPDK Coalition, which announced 10 founding members, including Cadence, May 11.
The coalition will address a nagging problem - the need for each foundry (whether IDM or pure play) to write a PDK not only for each process, but for each EDA vendor. This results in redundant work and extra expense, as well as potential delays for those who want to design at new process nodes. PDKs not only enable analog/custom design, but also make digital standard cell design possible. Thus, anything that impacts PDK delivery potentially impacts the entire semiconductor development chain.
The idea of the OpenPDK Coalition is simple - to define an open standard that will allow the PDK structure to be as portable as possible, and as agnostic to EDA tools as possible. The coalition was approved by the Si2 board in February and has just announced its founding members. They include AnaGlobe Technology, Cadence, IBM, Intel, Mentor Graphics, NXP, Pulsic, SpringSoft, STMicroelectronics, and Synopsys.
"The goal of OpenPDK is to enable broad market interoperability for process design kits that are exchanged," said Steve Schulz, Si2 president. "The cost of redundantly creating that information is going up, especially as you get to finer process nodes." A standard, he said, will help "anyone who touches a PDK" to become more efficient, including fabless semiconductor companies who often modify PDKs.
"The need for a single source for EDA enablement is real," said John Stabenow, group director of custom analog product marketing at Cadence. "The idea is that the foundry can publish one file, producing one set of information that any EDA vendor can use to develop the PDK for their tools."
A distinctive approach to standards
The OpenPDK initiative is not trying to impose a single PDK format on EDA vendors. Rather, it seeks to create an open description format or database that foundries can populate. Translators or "format generators" would then bring this data into existing data input formats, including the Cadence SKILL language. As shown below, it works on (but does not require) the OpenAccess (OA) database.
The OpenPDK Coalition will provide an open format that can be translated into existing input data formats. Source: Si2
"OpenPDK is the only proposed ‘single source' solution that will allow each vendor to maintain proprietary PDK formats that enable them to differentiate from one another and highlight the features of their individual product offerings," Stabenow said. "But the beauty of this initiative is that burden falls on the EDA vendor, not the foundry. So the designer gets the best of both worlds -- faster availability of PDKs from the foundry, and differentiated and competitive product offerings from the EDA vendors."
"There is a need for addressing something that doesn't force an immediate and radical shift from current practice," Schulz said. The coalition's goal, he said, is to figure out what elements can be common, develop an "input once, use many" paradigm, and "make it as efficient as it can be without forcing a change to the inputs that existing tools work with."
The OpenPDK Coalition will seek to establish a common syntax and semantics for foundry data. What distinguishes one foundry from another is the way they populate that structure. For example, the standard would set up a common way to express parameters, but would not dictate what the parameters are.
The OpenPDK Coalition has identified several specific requirements, including interoperable OA symbols, a component description format (CDF) specification, callback specifications, PCell evaluation, SPICE socket, OA technology enhancements, and OpenDFM verification rules. I will describe some of these in a future blog.
OpenPDK and IPL
The Interoperable PDK Libraries (IPL) alliance is an industry group with a stated goal of promoting interoperable PDKs. So what's the difference? "The relationship of OpenPDK and IPL is 100 percent complimentary," Schulz said. "IPL is focused on specifying the format of the file sets that are actually delivered. OpenPDK focuses on a broader interoperability that includes other formats. We are not mandating a format."
So, if you go back to the illustration shown above, an IPL format would simply become one of the boxes under the "existing input data formats" bar.
DAC workshop explains more
Want to know more about OpenPDK? Then attend the free Advances in Process Design Kits Workshop at the Design Automation Conference June 14 in Anaheim, California from 1:00 to 4:00 pm. Steve Schulz and John Stabenow will join other speakers from Intel, TSMC, Cadence, Mentor Graphics and SpringSoft to discuss PDK standards. If you're coming to DAC, bring your questions and perspectives!