We first report on the thermal stability and electrical properties of 5 nm-thick TaN films prepared by atomic layer deposition (ALD) using pentakis(ethylmethylamino)tantalum (PEMAT) and ammonia. The deposition rate of the ALD-TaN process was about ∼0.067 nm per cycle in a temperature range between 200 and 250 °C, which is a typical feature of ALD process. In cross sectional transmission electron microscopy (TEM) images, the deposited TaN films exhibited a very smooth and uniform interface. The thermal stabilities of these films were tested by depositing a Cu film of 200 nm thickness on a TaN layer and subsequently performing annealing for 30 min by varying the temperature from 300 to 800 °C in N2 ambient. The high and low-frequency capacitance–voltage (C–V) and breakdown characteristics of a Cu/TaN/SiO2/Si capacitor showed that the barrier properties of thin TaN films against Cu diffusion are inhibited above 500 °C, which is considerably lower than the inhibition temperature estimated by four-point probe or X-ray diffraction (XRD) measurement.

The improved contact resistance was obtained by the new barrier metal scheme such as CVD-Co/Ti/TiN process in the level of about half of that from CVD-Ti/TiN process. And the mechanism of contact silicidation of CVD-Co/Ti/TiN was investigated. Because Co silicide may prohibit the Si diffusion into Ti silicide and Si recess during TiCl4-based CVD-Ti process, and the inertness of Co silicide to the dopants, the improved contact resistance with uniform silicide morphology was obtained. Therefore, CVD-Co/Ti/TiN contact silicide process can be regarded as the next generation contact silicidation process.

For a diffusion barrier against Cu, tantalum nitride (TaN) films have been successfully deposited by both conventional thermal atomic layer deposition (ALD) and plasma assisted atomic layer deposition (PAALD), using pentakis (ethylmethlyamino) tantalum (PEMAT) and ammonia (NH3) as precursors. The growth rate of PAALD TaN at substrate temperature 250° was slightly higher than that of ALD TaN (0.80 Å/cycle for PAALD and 0.75 Å/cycle for ALD). Density of TaN films deposited by PAALD was as high as 11.0 g/cm3, considerably higher compared to the value of 8.3 g/cm3 obtained by ALD. The N: Ta ratio for ALD TaN was 44: 37 in composition and the film contained approximately 8∼10 atomic % carbon and 11 atomic % oxygen impurities. On the other hand, the ratio for PAALD TaN layers was 47: 44 and the respective carbon and oxygen contents of TaN layers decreased to 3 atomic % and 4 atomic %. The stability of 10 nm-thick TaN films as a Cu diffusion barrier was tested through thermal annealing for 30 minutes in N2 ambient and characterized by XRD, which proves the PAALD deposited TaN film to maintain better barrier properties against Cu below 800°.

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