Chemical vapor deposition of copper thin films for multi-level interconnections

Copper thin films were prepared by a metal organic chemical vapor deposition technology on top of TiN/Si substrates, and the films were examined by varying the experimental substrate temperature and copper source vapor pressure. Emerging semiconductor sub-quarter-micron technologies require a multi-level interconnection design that reduces the interconnection lengths and enhances device speeds. The microstructures of the Cu film were analyzed by transmission electron microscopy and transmission electron diffraction (TEM/TED) and the electrical resistance was measured by a four-point probe. The crystallinity of the Cu films increased as the substrate reaction temperature increased. The optimum reaction temperature was 180 °C. The effect of annealing on the electrical conductivity of the Cu films was also determined. The results indicate that the grain size and crystallinity of the films were observed to increase post-annealing, and thus the electrical conductivity was increased. The optimum electrical property of the copper film was obtained by in-situ annealing treatment at > 350 °C for a sample prepared at 180 °C substrate temperature. This technology is suitable for multi-level interconnections in ultra-large-scale integration, since intermetal dielectric materials require low-temperature processes.