Electrical characterization of reactively sputtered TiN diffusion barrier layers for copper metallization

TiN films were characterized by sheet resistance measurements, Auger electron spectroscopy and cross-sectional transmission electron microscopy. The properties as diffusion barrier between copper and silicon were investigated by diode leakage current measurements on n+p diodes after annealing at 350°C for 30 min and at 450, 500 and 550°C for 60 min. Both Ti-rich and N-rich TiN films were deposited at a DC magnetron power of 8 kW. Furthermore, additional N-rich films were deposited at a DC magnetron power of 2 kW. The copper was then deposited by metalorganic low pressure chemical vapour deposition and by sputtering. Samples with and without a diffusion barrier were prepared. N-rich films deposited at DC magnetron powers of 2 and 8 kW are found to be an effective barrier up to an annealing at 500°C for 60 min in case of metallization with sputtered copper. On the other hand the Ti-rich barriers still fail after annealing at 450°C for 60 min. The barrier structures metallized with copper deposited by metalorganic low pressure chemical vapour deposition are almost broken even at lower temperatures.