Diffusion barrier properties of metallorganic chemical vapor deposited tantalum nitride films against Cu metallization

TaNx films were deposited by chemical vapor deposition using a pentakis(die thylamido)tantalum (PDEAT) source with and without NH3 at temperatures rang ing from 300 to 375 degrees C. It was observed that both the resistivity an d carbon content of the film drastically decreased upon the addition of NH3 . For trample, the resistivity decreased from 60,000 to 12,000 mu Omega cm, and the apparent carbon content obtained by Auger electron spectroscopy de creased from 30 to 1 atom % by the addition of 25 seem NH3. The grain size initially increased with the addition of 5 seem NH3 in the source gas, but then decreased as the NH3 flow rate was increased to more than 10 seem. As- deposited TaNx film has a face-centered cubic structure irrespective of the amount of NH3. The density of the film increased from about 5.1 to 7.2 g c m(-3) (bulk density of TaN: 16.3 g cm(-3)). Barrier failure results identif ied by the etch-pit test showed that a 50 nm thickness of the TaN, barrier deposited by a single source of PDEAT survived up to 500 degrees C after 1 h annealing. The TaNx film deposited with 25 seem NH3 survived up to 550 de grees C after 1 h annealing. However, the step coverage of the films deposi ted with NH3 is drastically decreased, from more than 80% (NH3 = 0 sccm) to less than 10% (NH3 = 25 seem). Thus. while the addition of NH3 significant ly improves both the resistivity and carbon content in the film, it deterio rates the step coverage of the film. (C) 1999 The Electrochemical Society. S0013-4651(99)01-027-7. All rights reserved.