Applicability of ALE TiN films as Cu/Si diffusion barriers

Amorphous TiN films were deposited on a p-(100) Si substrate using an atomic layer epitaxy technique that employed TEMAT and NH3 as precursors at a temperature range between 150 and 220 degrees C. The average deposition rate was approximately 4.5 Angstrom/cycle and was in good agreement with the result expected from the layer-by-layer growth mode. The deposited TiN films showed excellent step coverage and uniformity for the trench with a high aspect ratio of h/w - 2.6:0.43 mu m. The diffusion-barrier behavior of both as-deposited and post-annealed 45-nm thick TiN films at temperatures between 550 and 700 degrees C were investigated against vacuum-evaporated Cu films using sheet resistance measurements, X-ray reflected diffraction, Auger electron spectroscopy, and scanning electron microscopy. The post-annealing of the ALE TiN films in a vacuum chamber of 2 x 10(-6) Torr was not found to be a very sensitive parameter for improving the diffusion-barrier function against Cu and Si; TiN films annealed up to 600 degrees C for 1 h maintained the initial composition of both Cu/TiN and TiN/Si interfaces, thereby indicating a negligible interdiffusion of the Cu and/or Si species through the TiN film. However, a further increase of temperature above 650 degrees C triggered Si and/or Cu interdiffusion resulting in a probable composition of Cu3Si. (C) 2000 Elsevier Science S.A. All rights reserved.