Assessment of critical Co electromigration parameters

Abstract

We perform a detailed assessment of the electromigration performance of Co interconnects. Package level EM measurements were performed during >11 months. Our estimate of the EM activation energy is similar to 1.4 eV which is, within error bar, consistent with earlier reported numbers. Our current exponent estimate suggests that void growth is the dominant contributor to Co EM. Through failure analysis, we associate void growth occurring through grain boundaries and at the barrier/metal interfaces. An activation energy assessment using low frequency noise measurements suggest a stronger contribution from this latter interface. Finally, we make a first estimation of an effective D0Z* for Co of similar to 1.72x10(-10) which is two orders of magnitude lower than for Cu.