Screening beneficial dopants to Cu interconnects by modeling

We present the results of first-principles simulations of dopant segregation to grain boundaries (GBs), dopant bulk diffusion, dopant and Cu self-diffusion at the GB, and the effect of the presence of a dopant on Cu diffusion at the GB for advanced Cu alloy interconnects. Several dopants that inhibit Cu GB diffusion were identified. Two primary mechanisms were found, namely, dopant blocking and dopant dragging. Early experimental results have confirmed model predictions for one of the several dopants (carbon) identified so far. The mean time to failure has increased more than 60% with a carbon concentration in Cu as low as 0.01 at. % and the resulting resistivity increase can be controlled below 15% compared to undoped Cu.