No abstract

Ta/Cu is a strategic material combination for ultra-large-scale integrated wafer technology. Here we report an unconventional method for the synthesis of a [110]-oriented nanocrystalline R-Ta thin film on freshly prepared Cu(111) templates at <50 °C without any redundant underlayers and post-growth treatments. The crystallite size of the R-Ta-containing thin film is in the range of only 6-8 nm, and the Ta film resistivity is reduced significantly from 186 µΩ cm down to 104 µΩ cm with this novel method.

Electromigration in 0.07 m wide Cu interconnections has been investigated for sample temperatures from 213 to 300°C. The effect of atomic-layer-or physical-vapor-deposited TaN x and physical-vapor-deposited Ta liner layers in Cu damascene lines on electromigration was also studied. A lower lifetime and activation energy for electromigration was observed in tested lines with sidewall voids. Similar electromigration lifetime and activation energy observed from samples with either atomic-layer-or physical-vapor-deposited TaN x suggested that the dominant diffusion paths in the Cu lines were not sensitive to the TaN x layer and were along the Cu/dielectric interface and/or grain boundaries.

No abstract

Different processes, including ''cool'' physical vapor deposition ͑PVD͒, of Ta barrier and Cu seed deposition were compared in Cu interconnect development. In the cool Ta process, the substrate temperature was Ͻ50°C, compared to a temperature of about Ͼ100°C in the standard process. With the cool process, via resistance ͑0.19 m in via size͒ was reduced by about 25%, although 40% thicker Ta was measured at the via bottom. This was not in agreement with the common understanding that the thicker the Ta film is, the higher the via resistance. Blank film studies suggested that a mixed texture of ␣and ␤-Ta was formed at via bottom in the new Ta/Cu process. X-ray diffraction spectra clearly exhibited the existence of ␣-Ta in addition to the ␤-Ta, where the latter is usually observed in the standard process. Electron diffraction spectra further supported the claim of mixed ␣-/␤-Ta formation at via bottom. Moreover, Rutherford backscattering data suggested that the mixed ␣-/␤-Ta had even higher thermal stability.