Thermal characterization of thin film Cu interconnects for the next generation of microelectronic devices

With the dramatic scaling of the transistors, the important issues like RC delay, electromigration failure and heat dissipation emerge, which need to be addressed urgently. Substitution of copper for aluminum has been suggested to reduce the RC delay of interconnects. While the electrical and mechanical properties of thin copper films have been extensively investigated; their thermal characterizations have received less attention. The lateral thermal conductivity of a 144 nm thick copper film is measured using the electrical resistance Joule heating and thermometry in a suspended bridge. The thermal conductivities at 300 K and 450 K are 240 and 280 W/m-K, respectively, which is smaller than the corresponding bulk values. The impact of the interconnect dimension and thermal conductivity on the self-heating is investigated as a function of interconnect via density. It is concluded that for via separation distances less than 5 μm, the combination of Cu interconnect and vias can significantly reduce the average temperature rise in multilayer interconnects.