NbxTa(1-x)NyOmCn diffusion barriers deposited by chemical vapor deposition (CVD) for copper metallization have been investigated. The barriers were deposited at 375 degreesC with tetrakis-diethylamido-niobium and pentakis-diethylamido-tantalum as precursors. Amorphous thin films can be obtained by thermal deposition at temperatures from 500 to 600 degreesC. The activation energy of the metal-organic CVD (MOCVD) process was determined to be 79.1+/-4.8 kJ/mol. By the incorporation of NH3 gas into reactants, both MOCVD deposition temperature and carbon concentration in the NbxTa(1-x)NyOmCn films were reduced. In addition, NH3-plasma post-treatment was implemented to prevent oxygen from being introduced into the barrier films.