Sputtered Cu films containing various insoluble substances, such as Cu(W2.3), Cu(Mo2.0),
Cu(Nb0.4), Cu(C2.1) and Cu(W0.4C0.7), are examined in this study. These films are prepared by
magnetron sputtering, followed by thermal annealing. The crystal structure, microstructure, SIMS
depth-profiles, leakage current, and resistivity of the films are investigated. Good thermal stability
of these Cu films is confirmed with focused ion beam, X-ray diffractometry, SIMS, and electrical
property measurements. After annealing at 400°C, obvious drops in resistivity, to ~3.8 μ-cm, are
seen for Cu(W) film, which is lower than the other films. An evaluation of the leakage current
characteristic from the SiO2/Si metal-oxide-semiconductor (MOS) structure also demonstrates that
Cu with dilute tungsten is more stable than the other films studied. These results further indicate
that the Cu(W) film has more thermal stability than the Cu(Mo), Cu(Nb), Cu(C), Cu(WC) and pure
Cu films. Therefore, the film is suitable for the future barrierless metallization.