Thermal and electrical properties of 5-nm-thick TaN film prepared by atomic layer deposition using a pentakis(ethylmethylamino)tantalum precursor for copper metallization

We first report on the thermal stability and electrical properties of 5 rim-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 similar to 0.067 nm per cycle in a temperature range between 200 and 250 degrees 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 200nm thickness on a TaN layer and subsequently performing annealing for 30 min by varying the temperature from 300 to 800 degrees C in N-2 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 degrees C, which is considerably lower than the inhibition temperature estimated by four-point probe or X-ray diffraction (XRD) measurement.