In Situ IR Observation of Electromigration Induced Damage in Heavily Doped Polycryst-Alline Silicon Resistors

Heavily doped (~ 1%) polycrystalline silicon resistor stripes were observed by infra-red microscopy during high direct current density (> 1X106 A/cm2) stressing. Hot spots at flux divergences were seen to develop and then disappeared upon reversing the direction of the current flow. AC stressing produced no hot spots. These results were interpreted to support a model where failure is caused by an electromigration-induced depletion of dopant in the grain boundaries giving rise to a local increase in film resistivity. Joule heating at these locations of high resistivity result in the hot spots, which then lead to circuit failure. A cine film is presented showing this process in action.