As feature sizes shrink cobalt start to look like a better choice for implementing wires than copper for reasons of electromigration and mean free path. Intel wanted to get a jump on this for their 10nm process and so decided to switch over to cobalt before TSMC, Global, etc. But they've been having huge problems getting it to work and 10nm has slipped from 2017 to at least 2019 and their process lead is now essentially gone.

They've actually released one chip on 10nm but it's performing much worse than the equivalent 14nm chip so it needs a lot more work.