Thermal stability of interconnect TiN/Cu/TiN multilayered structure

The etching process for a Cu interconnect with self-aligned deposition of a thick sidewall film has been developed. This sidewall film acts as a barrier layer to prevent Cu from corrosion and oxidation during the subsequent process, such as formation of a passivation film. Using this etching process, the Cu interconnect of a TiN/Cu/TiN multilayered structure in a submicron feature is formed. Resistivity for the Cu interconnects is about 2 μΩ&middotcm, and it does not change on annealing up to 700 °C. Diffusion of impurities into Cu is not observed up to 800 °C annealing. Therefore, the structure of the Cu interconnect, that is, Cu covered with TiN and the thick sidewall film, is suitable for the ULSI process.