Electromigration is a major source of wire and via failure. Refueling undoes EM for bidirectional wires and power/ground grids-some of a chip's most vulnerable wires. Refueling exploits EM's self-healing effect by balancing the amount of current flowing in both directions of a wire. It can significantly extend a wire's lifetime while reducing the chip area devoted to wires.
Abella, J., Vera, F.J., Unsal, O., Ergin, O., Gonzalez, A., Tschanz, J. W. Refueling: Preventing wire degradation due to electromigration. "IEEE micro", Desembre 2008, vol. 28, núm. 6, p. 37-46.