Nucleation and growth of Cu by chemical vapor deposition (CVD) using hexafluoracetylacetonato-Cu(I)-trimethylvinylsilane [hfac(Cu)tmvs] on different physical vapor deposition (PVD) diffusion barriers, namely, tantalum (Ta) and tantalum nitride (TaN x with x < 0.5), were studied by means of scanning and transmission electron microscopy to understand the dependence of morphology and microstructure on deposition parameters. X-ray diffraction measurements were carried out to study the orientation of the polycrystalline films. Atomic force microscopy was used to investigate the surface roughness. The results were compared to sheet resistance and reflectivity measurements. Nucleation on bare Ta and TaN x surfaces is significantly more difficult than on Ta with a 200 Å PVD Cu "flash" layer. The films directly deposited on Ta or TaN x show a random orientation and an amorphous interlayer between the CVD Cu film and the barrier. CVD Cu films grown on a PVD Cu "flash" layer expose a highly preferred <111> orientation of the grains and no amorphous interlayer.

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Articles you may be interested inComparative study of the role of the nucleation stage on the final crystalline quality of (111) and (100) silicon carbide films deposited on silicon substrates.Correlation between the early stage of copper metal organic chemical vapor deposition and the material properties of thin filmThe heterogeneous nucleation and subsequent growth of chemical vapor deposited copper using hexafluoroacetylacetonate-Cu͑I͒-trimethylvinylsilane on physical vapor deposited tantalum and chemical vapor deposited titanium nitride was studied by means of electron microscopy and atomic force microscopy. It was found that the nucleation densities are about two orders of magnitude higher on TiN than on Ta. This leads to an increased roughness of films deposited on Ta compared to those produced on TiN. Moreover, the Cu films on the Ta substrate show a large number of voids, whereas no such voids were observable in the Cu films deposited on top of TiN. A simplified model for the influence of gas-surface reaction and surface self-diffusion on the shape of the Cu grains was developed. This model, which is supported by the experimental data, shows that if the grain shape changes from spherical to nonspherical before coalescence with neighboring grains, voids occur. A critical grain size and nucleation density of about 150 nm and 5ϫ10 13 m Ϫ2 , respectively, were calculated for the deposition conditions used in this work.

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