Analysis of Joule heating in multilevel interconnects

Abstract

Metal Joule heating in interconnects is studied numerically. Representative models featuring multilevel interconnect structures (from single level to eight level) are used for the finite element analysis. Particular attention is devoted to the effects of current density, the number of conductor levels, and the materials used as the metallization and interlevel dielectrics. Transient heat conduction analyses are carried out to quantify the temperature rise. It is found that increasing the total number of metal levels and/or switching the dielectric from silicon oxide to polymer-based low-dielectric-constant materials can cause substantial temperature increases, which points out that interconnect Joule heating can become a reliability problem in future applications. The maximum temperature increases with the current density and the metal wiring density in an exponential manner. Incorporating low-k dielectrics based on an embedded insertion scheme can greatly relieve the heating problem. An example of reducing the temperature rise by adapting a cooling mechanism at the packaging level is also illustrated numerically. The effects of constant versus pulsed dc currents are discussed.