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Enhanced growth and Cu diffusion barrier properties of thermal ALD TaNC films in Cu/low-k interconnects

Wojcik, H.; Hossbach, C.; Kubasch, C.; Verdonck, P.; Barbarin, Y.; Merkel, U.; Bartha, J. W.; Hübner, R.; Engelmann, H.-J.; Friedemann, M.


For thermal ALD TaxNyCz films improved growth behaviour and Cu diffusion barrier performance are demonstrated by applying a plasma treatment prior to film deposition, in particular on low-k dielectrics. Two different kinds of ALD processes for depositing thermal ALD TaxNyCz films are applied in this study, involving either TBTDET or PDMAT as a precursor. Ammonia is used as a reactant and Ar as a purging gas in both processes. Within the experiment, two types of pre-treatments prior to ALD are investigated: a wet-chemical pre-treatment using diluted (0.5%) HF, and plasma pre-treatments using Ar/H2 or N2 plasmas. It is examined by transmission electron microscopy (TEM) from a microstuctural perspective whether improved growth behaviour of thermal ALD TaxNyCz films can be achieved by applying a plasma treatment prior to film deposition. The Cu diffusion barrier properties of 10-15 nm ALD TaNC films are then evaluated by bias temperature stress (BTS) and triangular voltage sweep (TVS) measurements on metal-insulator-semiconductor (MIS) test structures, after annealing at up to 600 °C under H2/N2 atmosphere. The results imply that, from a process side, thermal ALD TaNC films can intrinsically achieve a Cu diffusion barrier performance similar to PVD TaN. However, if no treatment was applied, Cu drift occurred.

Keywords: ALD TaN; Cu diffusion barrier; Triangular voltage sweep; Plasma treatment; Low-k


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