Authors: D.T. Read, R.H. Geiss
Affilation: National Institute of Standards and Technology, United States
Pages: 218 - 221
Keywords: alternating current, cycling, lifetime, temperature
We report tests of 300 nm wide damascene copper interconnect lines in silicon oxide dielectric to failure under high amplitude, low frequency alternating current. The cyclic minimum and maximum resistances were obtained from the measured voltage and current waveforms, by fitting each using a discrete fourier transform and then applying a Weiner filter. L’Hopital’s rule was applied to obtain the minimum resistance, at zero current. The minimum and maximum resistances remained nearly constant over the lifetime tests. In the lines tested under voltage control at the highest current levels, copper deposits were found near the center of the length of the lines. These deposits were wider than the original damascene lines and showed features that seemed to indicate repeated melting over multiple cycles of current. The lifetimes, plotted against temperature, formed a nearly straight line on a semi-log plot, even though the failures, particularly those run under voltage control, became considerably less catastrophic for the long lifetimes. The challenge is to understand the individual and combined effects of the temperature, current, and thermomechanical stresses. Understanding these effects will open up the possibilities for utilizing these electrical tests as in systematic assessments of interconnect reliability and quality control.