Comparative study of Ta and TaN(N) in the barrier/ultra low k structures for deep submicron integrated circuits

Abstract

Two kinds of barrier layers, Ta and TaN, deposited on an ultra low k dielectric porous polymer film with k = 2.3 were evaluated using various techniques after thermal treatments at 400°C for different periods of time. It was found that the sheet resistance of the Ta barrier increased significantly after being annealed for 60 min while that of TaN increased after 120 min due to Ta-O compound formation as revealed by X-ray diffraction and secondary ion mass spectrometry. The better integrity of the TaN compared Ta is due to N incorporation, which limits the diffusion of Ta and O. The diffusion coefficient of Ta in the porous polymer is 0.023 ± 0.001 nm 2/s, while the diffusion coefficient of TaN is only 0.0033 ± 0.0001 nm 2/s.