FinFET or FD-SOI? Designers have a real choice, say experts

Is FD-SOI a better choice than FinFETs for my chip? In some high-profile forums, designers are now asking that question. And the result is coming back: almost certainly.

Is there a place for FinFETs? Of course there is. If it’s a really big digital chip –  no significant analog integration, where leakage not your biggest concern because what you’re really after is the ultimate in performance, when you’ve got a mega-budget and you’re going to run in extremely high volume, absolutely, you can make a strong business case for bulk FinFETs.

But is that really where most designs are?

Cannery Row at twilight
(Photo credit: Monterey County Convention and Visitors Bureau)

If you need high-performance but you have to consider leakage (think battery life), if you’ve got to integrate the real world (aka analog – think IoT), if your chip is not a monster in size and will run in high volume but you don’t have an unlimited budget, you should be looking hard at FD-SOI. That’s what the experts at the recent EDPS conference in Monterey, CA said, that’s what they’re starting to tell the press, and that’s what they’re saying here on ASN.

Combined with the pretty dazzling results of the first 28nm FD-SOI silicon from cryptocurrency chipmaker SFARDS (read about it here) and the promise of very-high volume FD-SOI chips hitting the shelves in 2016, it’s a whole new ballgame.

EDA experts weigh in at EDPS

Richard Goering over at the Cadence and Herb Reiter writing for 3DInCites wrote excellent blogs covering the EDPS conference in Monterey, CA a few weeks ago. EDPS – for Electronic Design Process Symposium – is a small but influential conference for the EDA community. Session 1 was entitled “FinFET vs. FD-SOI – which is the Right One for Your Design?”, and it lasted the entire morning.

EDPSlogoThe session kicked off with a presentation by Tom Dillinger, CAD Technology Manager at Oracle. Richard covered this in-depth in Part 1 of his two-part write-up (read the whole thing here). Tom gave an overview of the two technologies, putting a big emphasis on the importance or working closely with your foundry whichever way you go.

And then came the panel discussion with questions from the audience, which Herb in his write-up (read it here) described as “heated”. Acknowledging that FinFET has the stronger eco-system, Herb noted that, “…when using FinFETs, designers complain about the modeling- and design complexities of fins, the need for double pattering (coloring), the higher mask cost and added variability the extra masking step introduces. If 10nm FinFETs will demand triple or even quadruple patterning, they may face a significant disadvantage, compared to the 14nm FD-SOI technology, currently in development.”

EDPS_FF_FDSOI_panel
EDPS 2015 panelists debate FinFET vs. FD-SOI. (Left to right: Marco Brambilla (Synapse Design); Kelvin Low (Samsung); Boris Murmann (Stanford); Jamie Schaeffer (GlobalFoundries). (Image courtesy: Richard Goering and Cadence)

In Part 2 of his coverage (read it here), Richard highlighted some of the big questions put to the panelists:

  • Kelvin Low, Sr. Director Foundry Marketing for Samsung
  • Boris Murmann, Stanford professor and analog/mixed-signal expert
  • Marco Brambilla, Director of Engineering at Synapse Design
  • Jamie Schaeffer, Product Line Manager at GlobalFoundries

The two foundry guys were very much of the opinion that FinFET and FD-SOI can and will co-exist. Jamie Schaeffer’s comment, as noted by Richard, really sums it up nicely: “For some applications that have a large die with a large amount of digital integration, and require the ultimate in performance, FinFET is absolutely the right solution. For other applications that are in more cost-sensitive markets, and that have a smaller die and more analog integration, FD-SOI is the right solution.”

There you have it!

Shaeffer was also very bullish on next-gen FD-SOI, noting that performance will climb by 40% with half as many immersion lithography layers as FinFETs. He also said that next-gen FD-SOI is 30% faster than 20nm HK/MG.

Marco Brambilla noted that for Synapse, the FD-SOI choice was all about leakage, especially in IoT products where you need a burst of activity and then absolute quiet in sleep mode. (They’re working on a 28nm FD-SOI chip that will go into very high-volume production in early 2016, Synapse Design recently told ASN – read about that here).

Boris Murmann said that extrinsic capacitance in FinFETS is “a mess”, which is “a nightmare” for the analog guys. “ It’s a beautiful transistor [FinFET] but I can’t use it.” Yes, Richard reported, that’s what the man said.

So indeed, there is a choice. And with FD-SOI, the experts are seeing that it’s a real one.

 

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