Atomic Layer Deposition of Molybdenum Nitride Thin Films for Cu Metallizations

Molybdenum nitride thin films were deposited by the atomic layer deposition technique within a temperature range of 350-500°C from molybdenum pentachloride and ammonia. The films were characterized by time-of-flight elastic recoil detection analysis, X-ray diffraction (XRD), and standard four-point probe method. films deposited at 400°C and above had a resistivity below 500 μΩ cm and the chlorine content was below 0.3 atom %. The diffusion barrier properties were studied from approximately 10 nm thick films deposited at 350, 400, and 500°C. Additionally, the barrier tests were performed with Mo(Ta)N and Mo(Ti)N films deposited at 400°C. The stability of the barrier layer was studied from the annealed Cu/barrier/Si structures by measuring the sheet resistance values, XRD data, and by performing etch-pit tests. Molybdenum nitride showed to be a promising diffusion barrier material. The barriers deposited at 400 and 500°C were observed to fail only after the annealing at 650°C.