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 350-500DGC 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. MoNx films deposited at 400DGC and above had a resistivity below 500 mOmega cm and the chlorine content was below 0.3 atom %. The diffusion barrier properties were studied from approximately 10 nm thick MoNx films deposited at 350, 400, and 500DGC. Additionally, the barrier tests were performed with Mo(Ta)N and Mo(Ti)N films deposited at 400DGC. 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 MoNx barriers deposited at 400 and 500DGC were observed to fail only after the annealing at 650DGC.