Effect of a titanium interlayer on the performance of the titanium nitride diffusion barrier

We have studied the effect of a Ti interlayer on the behavior of a TiN diffusion barrier for Al and Cu metallizations. Thermal stability of Al/Ti/TiN/[Si] and Al/TiN/[Si] samples annealed at 400-600 degrees C for 30 min was investigated using Auger electron spectroscopy (AES), glancing angle X-ray diffraction and scanning electron microscopy (SEM). Sheet resistance was measured for electrical characterization. After annealing at 400 degrees C and 500 degrees C, the Al/TiN/[Si] samples exhibited the same sheet resistance as the as-deposited one, while the sheet resistances of the Al/Ti/TiN/[Si] samples increased upon annealing. After annealing at 600 degrees C, pyramidal pits developed on the surface of the Al/TiN/[Si] sample, but not on the Al/Ti/TiN/[Si] sample. Sheet resistance measurements for the 600 degrees C-annealed Al/TiN/[Si] sample resulted in a more scattered distribution and a higher average value than for the Al/Ti/TiN/[Si] sample. The results clearly indicate that the performance of the TiN barrier layer is significantly improved by including a thin Ti film between the TIN and the Al. The Ti interlayer also improves the TiN barrier performance for the Cu metallization system.