In the usual process of patterning the metal lines in microelectronics, copper is deposited into trenches etched into the native insulating layer. In order to minimize environmental damage to the delicate wiring, the wires are then encapsulated using a dielectric layer. Despite the care taken to protect the circuitry, a significant mechanism in the failure of such wiring remains electromigration, whereby the copper atoms react with and diffuse into the dielectric layer.
Now Hu et al. show that coating the copper surface with a 20-nanometer layer of CoWP, CoSnP, or Pd before depositing the encapsulating dielectric layer can significantly improve the lifetime of the wiring circuitry. As the demand for smaller and smaller sized circuits continues to rise, such an effective coating should prove useful in putting the brakes on electromigration. — ISO
Appl. Phys. Lett. 81, 1782 (2002).