Stress-Induced Electromigration Backflow Effect in Copper Interconnects

Abstract

The electromigration threshold in copper interconnect is reported in this paper. The critical product (jL) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> is first determined for copper oxide interconnects with temperature ranging from 250degC to 350degC from package-level experiments. It is shown that the product does not significantly change in this temperature range. Then, (jL) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> was extracted for copper low-k dielectric (k=2.8) interconnects at 350degC. A larger value than that for oxide dielectric was found. Finally, a correlation between the n values from Black's model and with jL conditions was established for both dielectrics