Transmission electron microscopy of CVD copper for metallisation in microelectronics

Patterned aluminium thin films, deposited by either sputtering or PVD have been the most widely used interconnect structures in the fabrication of silicon devices. However, as device dimensions approach deep sub-micron sizes, the reliability of the interconnect in terms of electromigration and also the interconnect resistance become increasingly important. Therefore, lower resistance metals are being investigated to replace the present aluminium based system. Copper thin films are attractive as ULSI conductor material as the higher melting point of copper removes the maximum temperature limit imposed for low melting point aluminium thus facilitating further processing of the multilevel microelectronic devices. CVD copper deposition from an organo-metallic precursor offers the highly conformal films required to fill vias and trenches in multilevel metal interconnect architectures. These films have been examined by TEM, AFM and AES and their microstructure related to the electrical properties.