Plasma-enhanced Atomic Layer Deposition of TaN Film and Its Resistance to Copper Diffusion

TaN films were deposited on monocrystalline silicon wafer via plasma enhanced atomic layer deposition with Ta[N(CH3)2]5 as precursor and NH3 plasma as coreactant. The as deposited films were characterized by means of atomic force microscopy, X-ray photoelectron spectroscopy, four-point probe and X-ray reflection. The results show that the as-deposited film consists mainly of TaN with small quantities of C and O. As the deposition temperature increases from 250℃ to 325℃, the ratio of Ta/N increases from 46: 41 to 55: 35, and the C-content (atomic fraction) decreases from 6% to 2%. Meanwhile, the resistivity of the film gradually decreases from 0.18 Ω∙cm to 0.044 Ω∙cm, and the film density increases from 10.9 g/cm3 to 11.6 g/cm3. After annealing at 400℃ for 30 min, the film density shows an increment of ~0.28 g/cm3 on average, and the film resistivity decreases to 0.12-0.029 Ω∙cm. Further, the barrier performance test results indicate that the TaN film of 3 nm in thickness deposited at 250℃ demonstrates a perfect barrier function after annealing at 500℃ for 30 min. © All right reserved.