The copper diffusion barrier properties of amorphous boron carbo-nitride (BCxNy) films were studied. The BCxNy films were deposited by chemical vapor deposition at 360 degrees C and 1 Torr using dimethylamine borane with no reaction gas (BC0.37N0.15), with NH3(BC0.19N0.44), or with C2H4(BC0.90N0.08); their dielectric constants were 4.1, 4.4, and 3.9, respectively. A SiC0.76N0.44 film was used to benchmark the study. Barrier films were deposited on 7 nm thermal oxide/n-type Si substrates. The leakage current for BC0.90N0.08, 1.1 X 10(-8) A /cm(2) at 0.5 MV/cm, is the lowest of the three but it is larger than that of the benchmark SiC0.76N0.44 film, 5.5 X 10(-9) A/ cm(2). Time dependent dielectric breakdown is used to test barrier time-to-failure of Cu-gate capacitors at 150 degrees C and +2 to 5 MV/cm. BC0.90N0.80 displayed barrier performance comparable to SiC0.76N0.44 and was noticeably better than BC0.37N0.15 and BC0.19N0.44. Overall, BCxNy barriers are promising and are improved with lower boron content, fewer B-B bonds, and increased B-C bonds. (c) 2005 American Vacuum Society.