CVD and ALD Co(W) Films Using Amidinato Precursors as a Single-Layered Barrier/Liner for Next-Generation Cu-Interconnects

Abstract

Cobalt film with tungsten addition [Co(W)] has the potential to be an effective single-layered barrier/liner in Cu-interconnects owing to its good adhesion with Cu, a lower resistivity than TaN, and an improved barrier property with respect to cobalt films. Our previous study on chemical-vapor-deposited (CVD) Co(W) using carbonyl precursors clarified, however, that WO3 included in the films increased the resistivity. In this current study, to reduce the resistivity of Co(W), oxygen-free process for Co(W) films were designed using two oxygen-free amidinato precursors, bis(N-tert-butyl-N′-ethylpropionamidinato) cobalt and bis(tert-butylimino)bis(dimethylamino)tungsten, by chemical vapor deposition (CVD) and atomic layer deposition (ALD) at 350–400°C. Deposition process were designed by employing quantum chemical calculation, in which NH3 were chosen as a reducing reagent for the sake of the low activation energy of deposition. NH3 actually acted effective reducing reagent for Co or Co(W) deposition using amidinato precursors in our research. Co(W) films using amidinato precursors and NH3 contained no oxygen and a few amounts of nitrogen. Nitrogen, however, were easily eliminated by annealing at 400°C. Therefore, Co(W) films using amidinato precursors were so high quality to have lower resistivity than Co(W) films using carbonyl precursors or conventional PVD-TaN.