Metal-organic chemical vapor deposition of tantalum nitride barrier layers for ULSI applications

Low-resistivity tantalum nitride (TaN) films were deposited by low-pressure metal-organic chemical vapor deposition (MOCVD) using a new precursor tertbutylimidotrisdiethyl amidotantalum. The surface morphology and the step coverage of TaN films were characterized by scanning electron microscopy. The film deposited at 450 degrees C had nearly 100% step coverage and the step coverage decreased to 25% for the films deposited at 650 degrees C, The carbon and oxygen concentrations are about 10 at.% in the CVD TaN films, as determined by Auger electron spectroscopy. From Rutherford backscattering spectroscopy and secondary ion mass spectroscopy analysis, TaN films were found to be effective diffusion barriers between aluminum and silicon up to 550 degrees C. The electrical measurements of diode-leakage current indicate that the Al/TaN/Si structure remained stable up to 500 degrees C, after which Al started to diffuse through the TaN layer and resulted in a higher leakage current.