By: Michael S (already5chosen.delete@this.yahoo.com), June 13, 2022 11:20 am
Room: Moderated Discussions
--- (---.delete@this.redheron.com) on June 13, 2022 10:47 am wrote:
> anonymou5 (no.delete@this.spam.com) on June 13, 2022 6:21 am wrote:
> > > There has been much speculation about whether the choice of cobalt had something to do
> > > with the shortcomings of the 10 nm Intel CMOS process. The fact that Intel 4 has reverted
> > > to copper, even if with improved linings, seems to confirm that supposition.
> > >
> > > The high resistance of the cobalt interconnections is likely to have been one of
> > > the reasons for the much too low clock frequencies of Cannon Lake and Ice Lake.
> >
> > Define "much too low".
> >
> > Sure, e.g. 3.2 for CNL wasn't king of the hill... but for a U part? Not too bad.
> >
> > The GPU side... was abysmal though...
> >
> > Also, if Co was a speed limiter, then Intel should have seen that coming.
> > Or are you suggesting their engineers are complete idiots? :)
> >
> > > The other serious problem of the 10 nm process, the very
> > > low yields, might have been determined mainly by their
> > > choices for photolithography, where they have attempted to get very small pitches without using EUV.
> >
> > This.
>
> Yeah, the cobalt story has always seemed like it omitted something.
> TSMC use cobalt for 7nm (and presumably 5nm, though I haven't seen
> direct evidence of that), and did not appear to have problems.
> https://twitter.com/lasserith/status/1121905450172211200?lang=ar
>
The tweet is bragging about cobalt *contacts*.
Intel tried to use cobalt *conductors* instead of copper conductors in two inner layers of the stack.
> Of course there are always details, and it's possible the precise way Intel insisted on using
> cobalt (in terms of liners, seeds, temperature processing, etc) got something wrong.
>
> So if cobalt works, why the reversion (or sideways move) to "enhanced copper" (which as I've
> pointed out before appears to be based on a TSMC paper from, I think it was, 2010)?
> This isn't the paper I had in mind (which I can't find right now) but shows
> similar sort of work: https://ieeexplore.ieee.org/abstract/document/5510762
>
> Perhaps "enhanced copper" was always the optimal solution, it just took time for Intel (and TSMC?
> or LAM for both of them?) to figure out the metallurgy in enough detail for manufacturing?
Optimal solution at this scale.
But for finer scales we will need a metal with shorter mean free path of electrons anyway.
If not cobalt then what?
> anonymou5 (no.delete@this.spam.com) on June 13, 2022 6:21 am wrote:
> > > There has been much speculation about whether the choice of cobalt had something to do
> > > with the shortcomings of the 10 nm Intel CMOS process. The fact that Intel 4 has reverted
> > > to copper, even if with improved linings, seems to confirm that supposition.
> > >
> > > The high resistance of the cobalt interconnections is likely to have been one of
> > > the reasons for the much too low clock frequencies of Cannon Lake and Ice Lake.
> >
> > Define "much too low".
> >
> > Sure, e.g. 3.2 for CNL wasn't king of the hill... but for a U part? Not too bad.
> >
> > The GPU side... was abysmal though...
> >
> > Also, if Co was a speed limiter, then Intel should have seen that coming.
> > Or are you suggesting their engineers are complete idiots? :)
> >
> > > The other serious problem of the 10 nm process, the very
> > > low yields, might have been determined mainly by their
> > > choices for photolithography, where they have attempted to get very small pitches without using EUV.
> >
> > This.
>
> Yeah, the cobalt story has always seemed like it omitted something.
> TSMC use cobalt for 7nm (and presumably 5nm, though I haven't seen
> direct evidence of that), and did not appear to have problems.
> https://twitter.com/lasserith/status/1121905450172211200?lang=ar
>
The tweet is bragging about cobalt *contacts*.
Intel tried to use cobalt *conductors* instead of copper conductors in two inner layers of the stack.
> Of course there are always details, and it's possible the precise way Intel insisted on using
> cobalt (in terms of liners, seeds, temperature processing, etc) got something wrong.
>
> So if cobalt works, why the reversion (or sideways move) to "enhanced copper" (which as I've
> pointed out before appears to be based on a TSMC paper from, I think it was, 2010)?
> This isn't the paper I had in mind (which I can't find right now) but shows
> similar sort of work: https://ieeexplore.ieee.org/abstract/document/5510762
>
> Perhaps "enhanced copper" was always the optimal solution, it just took time for Intel (and TSMC?
> or LAM for both of them?) to figure out the metallurgy in enough detail for manufacturing?
Optimal solution at this scale.
But for finer scales we will need a metal with shorter mean free path of electrons anyway.
If not cobalt then what?