Abstract
Low-frequency measurements were performed on W-plug via structures connecting two TiN/Al-0.5%Cu/TiN levels in order to evaluate the potential application of noise measurements as a characterization tool for electromigration reliability. Noise measurements were performed with ambient temperature ranging from 87°C to 180°C and applied current from 5.9 to 23.8 mA through 1.0 μm and 0.8 μm vias, corresponding to sample temperatures up to 195.2°C. The noise spectral density was found to be in the form of 1 ƒ . The noise magnitude was consistently higher for both vias when the electron flow was from upper level to lower level compared to the opposite direction. The noise activation energy E a obtained from the temperature dependence of voltage noise power spectral density at 10 Hz showed different behavior for the 1.0 μm via compared to the 0.8 μm via. For the smaller via, E a = 0.36–0.37 eV regardless of the electron flow direction, whereas for the larger via, E a = 0.47 eV for electron flow from upper level to lower level and E a = 0.37 eV for electron flow from lower level to upper level.
Published Version
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