Influence of N2/H2 plasma treatment on chemical vapor deposited TiN multilayer structures for advanced CMOS technologies

Titanium nitride (TiN) multilayer (7.5–12 nm) structures with excellent conformity were produced by chemical vapor deposition from Ti[N(CH3)2]4 (the so-called TDMAT) on a heated substrate with an additional N2/H2 plasma treatment (PT) after deposition. They are well suited for deep submicron vias with aspect ratios of more than three. We apply time-of-flight secondary ion mass-spectroscopy, transmission electron microscopy, and Auger electron spectroscopy for a detailed characterization of morphology, structure and composition of the multilayers and analyze the barrier efficiency against Al diffusion. We demonstrate that low-energy primary beams and sample rotation applied during ion sputtering analysis significantly improves the depth resolution in elemental depth profiles and allows to characterize the effect of PTs more efficiently. The N2/H2 PT introduces a strongly anisotropic layer modification including etching, densification, crystallization and compositional changes. The plasma is effective in removing process induced contamination of the TiN layers (O, C) up to a depth of up to 5–8 nm, where the concentration is reduced by more than one order of magnitude. A minor influence is detected up to a depth of 10 nm, obviously mainly due to outdiffusion effects. The analysis of Al diffusion in TiN reveals a good diffusion resistance of the barrier up to 570 °C.