Electromigration in thin aluminum films on titanium nitride

TLDR

Aluminum electromigration drift velocity was measured from 250–400 °C, and the observed threshold is attributed to opposing chemical gradients caused by atom pile‑up and depletion at stripe ends. The threshold current density decreases with increasing stripe length, has an activation energy of 0.65 eV, rises when temperature is lowered or the aluminum is enclosed in silicon nitride, and very short stripes exhibit virtually no electromigration even at current densities above 10⁶ A/cm².

Abstract

The aluminum electromigration drift velocity was measured at the temperature range 250–400 °C. A threshold current density was found inversely proportional to the stripe length. An activation energy of 0.65 eV was found for the drift velocity. The occurrence of the threshold is explained by opposing chemical gradients created by the atom pile-up and depletion at the stripe ends. The threshold may explain several observations reported previously. The threshold is increased by decreasing the temperature or by enclosing the aluminum in silicon nitride. Virtually no electromigration is seen for very short aluminum stripes even at current densities above 106 A/cm2.