A little background, why this is interesting. Many years ago, when I studied semiconductor engineering we learnt that copper is poison for the CMOS process and that the fab had to be kept free from copper contamination.
The reason for this is that copper, contrary to aluminium, diffuses very quickly in silicon and silicon dioxide.
Of course there are reasons why you might prefer copper over aluminium as an interconnect. So a process has been developed to make this possible and safe. The process is called Damascene and the article is about significant improvements there.
And "Damascene" is a reference to pattern welding (often called "Damascus" even though it's not the same thing as historical Damascus steel), where different metals are forge welded together to make laminated patterns:
https://en.wikipedia.org/wiki/Pattern_welding
Here the copper is coated with a very thin barrier layer of rhodium, so there's also a laminated pattern of different metals.
Awesome context, thank you!
According to this interview, TSMC was the first to deploy copper interconnects in a production process.
"...So, when we went to .13u, .13u the people began to change from aluminum to copper. And IBM was the leader for the copper metal. They had the longest history of developing copper technology. They worked for more than ten years on copper. TSMC didn't have any experience in copper at all. So, when we decided we need to adopt copper, okay. So, the copper is one story and low-k material is another one. IBM decided kind of low-k material is a spin-on material called SILK. IBM had a Research Consortium that IBM-- Samsung joined them, I think, ST Micro joined them. Several companies joined the Consortium.
"And UMC joined them. But we didn't join them. They all used that spin-on low-K material. But we decided to use CVD - instead of flourine-doped it's a carbon-doped made by Applied Materials. They're called Black Diamond. So, we choose Black Diamond. The reason we chose Black Diamond was very simple, because I suffer at .18 with a spin-on. I wouldn't touch spin-on again. <laughter> But they didn't go through that. So, we were very, very lucky. TSMC became the first company in the world which was able to ship a manufacturing wafers with the copper and low-k, because IBM failed..."
".13u was actually the very important node for TSMC. Because we became the first one in the world to deliver manufacturing wafer of copper and low-K."
--Moris Chiang
https://www.computerhistory.org/collections/catalog/10265812...