Failure mechanisms of silver and aluminum on titanium nitride under high current stress

The effects of high-current stress (3-10 A) on single-line structures of aluminum (Al) and silver (Ag) of different widths (2.5-10 μm) and on titanium nitride (TiN) as barrier are reported in this paper. As the applied current-densities were increased, the lines experienced catastrophic failure. In the cases of Al/TiN/SiO2 and Ag/TiN/Si, failure occurred at individual sites that were distributed over the length of the line. Failure times, for all line widths and for both metallizations, showed a non-linear dependence on current density. The current-density exponent (m) was calculated for the different structures. For Al/TiN/SiO2 and Ag/TiN/Si lines, the value of m was found to be ∼1.4-1.6 and ∼1.2-1.4, respectively, lower than the value of 2 reported in the literature for Al/SiO2 structures. The current-density exponents were found to be independent of line widths. Failed structures were characterized using analytical tools. The mode/mechanism of failure was found to be Joule-heating induced vaporization of the metallization followed by mechanical failure of the barrier TiN (for Al/TiN/SiO2), or melting and vaporization of the barrier TiN (for Ag/TiN/Si).