Sure, so Intel is using cobalt at low dimension interconnects (e.g. M0-3) because cobalt has lower resistance than copper at low dimensions due to electron mean

Sure, so Intel is using cobalt at low dimension interconnects (e.g. M0-3) because cobalt has lower resistance than copper at low dimensions due to electron mean free path issues. The rumor is that integration of the cobalt material is what's causing yield issues at Intel for 10nm.