Thinner Films Conduct Better Than Copper

Because copper is no longer a good enough conductor when it it is used in very thin layers, the latest and densest CMOS fabrication processes have begun to replace copper with other metals for the first 2 metal layers, which are the thinnest.

It is not known with certainty what metals are currently used by Intel or TSMC, though cobalt and ruthenium have been considered as the most promising choices.

There has been a lot of speculation about whether the choice of cobalt for the thinnest metal layers has been an important cause of Intel's woes with their "10 nm" CMOS fabrication process.

While there were chances for this hypothesis to be true, the actual reasons for Intel's failure to achieve the predicted clock frequencies and fabrication yields with their "10 nm" processes remain unknown, because Intel has never published any information about this.

Whichever was the reason, eventually Intel has succeeded to fix this fabrication process, even if only around 5 years later than in their initial plan, after rebranding it in "Intel 7", at least from the point of view of the achievable performances, which have culminated in Raptor Lake Refresh, though perhaps Intel's incapacity of predicting accurately the reliability behavior as a function of the supply voltage, as demonstrated in many failures of Raptor Lake/Alder Lake CPUs, may indicate that they have never succeeded to understand the exact characteristics of this fabrication process.

Correct title is "New Films Conduct Better the Thinner They Get"

The research described was done at Stanford by Profs Eric Pop and Krishna Saraswat. Paper in Science: https://www.science.org/doi/10.1126/science.adq7096

I wonder if that's only about direct current. The higher frequency is AC, the more it conducts on sides of the wire (hence insulated strands). So I wouldn't be surprised by their discovery if we talked about very high frequency AC.

But since it all reversed here it might by opposite for AC in their case.

UPDATE: paper says something about RF (radio frequency), but I'm not sure I understand what it means, looks more like manufacturing process.

The research looks detailed and interesting. However, I don't follow this summary article.

Digital circuits dissipate most of the energy charging and discharging capacitance. It must necessarily dissipate that as heat (except for a minor amount of electro-magnetic radiation). The interconnect resistance hardly matters. Of course RC relay can be a factor for some circuits. We can hope this reasearch leads to improvement there.

Power supply bus resistance can lead to voltage drops, but this research apparently studies layers much too thin for that application.

Did I missing something?

The linked article does not go into many details about what they are measuring. So I have to wonder: could this property be used to make thinner wires for conducting electricity in bulk (e.g.: hosing wires, or transmission lines) by stacking lots of very thin layers into a cable. I imagine there would be a good amount of development work to make manufacturing such a layered cable, so it would not be right around the corner. But is there any physical barrier to such a development?

Cool! Or lukewarm. Or both since they tested from 5K to 300K. And found that the thin films (5-18nm) 'behaved like' metals wrt temperature dependence of resistivity, where thicker films of the same material (80nm) 'behaved like' insulators.

I wonder how traditional superconductor materials would fare in a super thin film regime like this.

The title here is sort of confusing-thinner films? Thinner than what? And what are these thin films made of?

Maybe something like “thin film semi metals conduct better than copper” would be better?