Local Joule heating and overall resistance increase in void-containing aluminum interconnects

Local Joule heating and the overall resistance change due to void formation in aluminum interconnects were studied numerically. In the model the TiN/A l/TiN metallization stack is embedded within the SiO2 dielectric. Three-dim ensional finite element analyses, taking into account the current shunting into the barrier layer and the coupling between heat conduction and electri cal conduction, were carried out. The temperature field and overall resista nce increase were obtained for various combinations of void geometry and ap plied current densities. It was found that the joule heat produced at the v oid site is largely conducted away by the Al line, leading to only small te mperature gradients along the interconnect. The voiding-induced temperature rise is significant only under very high current densities and when the vo id is very large. The overall resistance increase is dominated by the void geometry, not by the Joule heat and the inherent high resistivity of the ba rrier layer material.