The speaker says gate-all-around transistors and backside power open a different design regime that makes alternating layers of transistors and interconnects conceivable.

“But for the larger lines, it-- I think copper is about where it's at. I think that once you start to do gate-all-around transistors and you do backside power, now you start to enter a very different regime of-- 'cause now you see it's not, "Hey, there's just some substrate," and you stack everything on top.”

“Now you've got a transistor which is floating an interconnect and you're like, "Okay, well, why don't I have transistors, interconnect, and then more transistors, more interconnect?"”