Normalize to drawn or effective width?

By: David Kanter (, February 6, 2015 1:44 pm
Room: Moderated Discussions
carop ( on February 5, 2015 3:40 pm wrote:
> David Kanter ( on February 5, 2015 12:45 pm wrote:
> >
> > Yes, I am. I've heard a number of people make the argument that it's better to normalize to Weff,
> > but the reasoning doesn't make sense to me (why not calculate leakage normalized to Weff?).
> > Moreover, most other companies are not disclosing effective width, so it makes things even harder.
> >
> With the gate wrapping around the fin, you effectively get higher device width per footprint of the device and
> for a given device footprint (which is typically set by number of metal tracks you allocate to a given standard
> cell and how much space is wasted to isolate devices and plug gate contacts) you get higher drive current.

Yes, we are totally agreed here.

> catch is that the higher Ion comes at the price of higher capacitance which Intel is not quoting.

Well yes, that's how you get better control over the transistor.

> > I don't find this argument particularly compelling, in part because I heard it mostly from
> > companies that aren't disclosing much about their own FinFET process (e.g., TSMC).
> >
> I believe it was IBM that suggested active current (Ieff) as a metric of speed in an IEDM paper.

Ieffective is something else. Ieffective is a metric that Intel had quoted numerous times. I cannot quite recall the definition, but I think its

Ieffective = Average of Ion @ Vgs=Vdd and Ion @ Vgs = 1/2 Vdd

It's essentially a measure of how well the transitor performs when not fully on, but in the upper end of the linear region.

> The figure is from the STM FD-SOI N10 paper which was presented at IEDM 2014.
> - [13] is Intel@VLSI2012
> - [14] is Intel@IEDM2012
> - [15] is TSMC@IEDM2013
> I included the figure for a quick Intel N22 and TSMC N16 device comparison. No, IBM did not normalize
> drive current to footprint in their IEDM 2014 SOI FinFET paper either. Intel seems to be the
> only manufacturer normalizing the drive current of their FinFET devices to footprint. I do not
> want to argue with that, but this is something to bear in mind when benchmarking.

I know that normalizing to effective width is a valid metric, but my point is that I don't understand exactly what it is saying. I know what normalizing to drawn width means.

> At N22, Intel used a fin height of about 35nm and fin pitch of 60nm. At N14, they increased fin height to
> 42nm and dropped fin pitch to 42nm. So the shrink from N22 to N14 increased channel width by 70% but drive
> current by less than 30% (15% nMOS, 41% pMOS). How do you explain this performance difference then?

Well it could be due to stress or other factors that determine performance.

< Previous Post in Thread 
TopicPosted ByDate
ARM announces A72Maynard Handley2015/02/03 12:36 PM
  ARM announces A72anon2015/02/03 01:53 PM
    ARM announces A72Hugo Décharnes2015/02/03 02:20 PM
      ARM announces A72juanrga2015/02/03 05:15 PM
        ARM announces A72Wilco2015/02/04 01:58 AM
          ARM announces A72Eric Bron2015/02/04 02:48 AM
            ARM announces A72none2015/02/04 03:24 AM
              ARM announces A72Eric Bron2015/02/04 03:42 AM
                ARM announces A72Exophase2015/02/04 08:01 AM
                  ARM announces A72Anon2015/02/04 08:35 AM
                    ARM announces A72Exophase2015/02/04 08:58 AM
                      ARM announces A72Groo2015/02/04 10:24 AM
                ARM Marketing, BS up to my earsDavid Kanter2015/02/04 11:51 AM
                  ARM Marketing, BS up to my earsMaynard Handley2015/02/04 02:59 PM
                    ARM Marketing, BS up to my earsDavid Kanter2015/02/04 03:21 PM
                  ARM Marketing, BS up to my earsGroo2015/02/04 03:30 PM
          ARM announces A72juanrga2015/02/04 05:23 AM
            ARM announces A72Wilco2015/02/04 04:01 PM
              ARM announces A72juanrga2015/02/04 05:06 PM
        ARM announces A72Anon2015/02/04 02:28 AM
          ARM announces A72juanrga2015/02/04 05:31 AM
            ARM announces A72Aaron Spink2015/02/04 07:49 AM
      ARM announces A72Ronald Maas2015/02/03 08:23 PM
        ARM announces A72Seni2015/02/04 01:19 AM
          ARM announces A72Maynard Handley2015/02/04 11:42 AM
            ARM announces A72Seni2015/02/04 01:33 PM
              ARM announces A72dmcq2015/02/04 01:57 PM
            ARM announces A72Ronald Maas2015/02/04 07:42 PM
        ARM announces A72anon2015/02/04 06:19 AM
          ARM announces A72Exophase2015/02/04 08:31 AM
            ARM announces A72David Kanter2015/02/04 11:25 AM
              ARM announces A72Exophase2015/02/04 02:33 PM
                ARM announces A72anon2015/02/04 11:27 PM
                  ARM announces A72 (fixed format)anon2015/02/04 11:29 PM
                  ARM announces A72Exophase2015/02/05 12:11 AM
                    ARM announces A72anon2015/02/05 01:02 AM
            ARM announces A72anon2015/02/04 06:57 PM
  ARM announces A72Wilco2015/02/03 02:39 PM
    ARM announces A72Maynard Handley2015/02/03 03:13 PM
      ARM announces A72anon2015/02/03 03:29 PM
      ARM announces A72Wilco2015/02/03 03:44 PM
    ARM announces A72David Kanter2015/02/04 10:56 AM
      ARM announces A72Peter Greenhalgh2015/02/04 11:56 AM
        ARM announces A72Aaron Spink2015/02/04 12:59 PM
          ARM announces A72Alberto2015/02/07 11:22 AM
            ARM announces A72Exophase2015/02/07 11:47 AM
              ARM announces A72Alberto2015/02/07 01:44 PM
                ARM announces A72Exophase2015/02/07 03:35 PM
                  ARM announces A72Alberto2015/02/08 02:09 AM
                    ARM announces A72Exophase2015/02/08 12:05 PM
              ARM announces A72David Kanter2015/02/08 01:39 AM
                ARM announces A72dmcq2015/02/08 05:14 AM
                  ARM announces A72Michael S2015/02/08 05:38 AM
                    ARM announces A72Gabriele Svelto2015/02/10 06:11 AM
                      ARM announces A72Jouni Osmala2015/02/10 12:24 PM
                        slit vs unifiedMichael S2015/02/10 02:57 PM
                          slit vs unifieddmcq2015/02/11 06:44 AM
                  ARM announces A72Doug S2015/02/08 10:00 AM
                ARM announces A72Exophase2015/02/08 11:57 AM
        ARM announces A72dmcq2015/02/04 02:10 PM
        ARM announces A72David Kanter2015/02/04 03:28 PM
      ARM announces A72Wilco2015/02/04 02:59 PM
        ARM announces A72Aaron Spink2015/02/04 10:31 PM
        Intel 32nm vs 14 nmMichael S2015/02/05 02:03 AM
          Intel 32nm vs 14 nmWilco2015/02/05 03:27 AM
            Intel 32nm vs 14 nmDavid Kanter2015/02/05 10:05 AM
              Intel 32nm vs 14 nmcarop2015/02/05 12:12 PM
                Normalize to drawn or effective width?David Kanter2015/02/05 12:45 PM
                  Normalize to drawn or effective width?carop2015/02/05 03:40 PM
                    Normalize to drawn or effective width?David Kanter2015/02/06 01:44 PM
Reply to this Topic
Body: No Text
How do you spell green?