TANTALUM-MICROCRYSTALLINE CEO2 DIFFUSION BARRIER FOR COPPER METALLIZATION

A tantalum diffusion barrier incorporating microcrystalline CeO2 is pr oposed for Cu metallization and investigated using Auger electron spec troscopy, x-ray diffraction, optical microscopy, transmission electron microscopy, and sheet resistance measurements. The Cu/Ta+CeO2/Si cont act system retained its structure up to 800 degrees C without an incre ase in resistivity. The cerium dioxide (CeO2) was stuffed along the gr ain boundaries during the deposition of Ta layer. Because of its heavi er atomic weight than O-2- or N-2-stuffed elements, it inhibited an in terdiffusion of Cu and Si through grain boundaries which can act as fa st diffusion paths. It also resulted in preventing the outdiffusion of Ta into the overlayer Cu as well as suppressing the formation of Ta s ilicide up to 800 degrees C. It appears that the barrier properties of the tantalum incorporating microcrystalline CeO2 are superior to poly crystalline transition metal barriers, polycrystalline nitride barrier s, ternary amorphous compound barriers, and N-2- and O-2-stuffed barri ers. (C) 1998 American Institute of Physics. [S0021-8979(98)05403-6].