|
(Ti, Al)N thin films are deposited on Si (100) substrates by reactive sputtering for potential application of the diffusion barrier layers in Ultra-large-scale integration (ULSI). A convenient and economic fabrication of the Ti-Al compound targets is applied by inserting molten aluminum into drilled titanium bulk. The composition of the (Ti, Al)N films are well controlled by varying the surface ratios of aluminum to titanium in the magnetron effective area of the targets and the compositions of the (Ti, Al)N film is thus modified.
The phase and structure of the films are identified to be a cubic Bl structure for AlN contents ranged from 11 mol.% to 50 mol.%. In the solid solution of (Ti, Al)N, Ti in the TiN cell is substituted by the smaller Al. As a result, the lattice parameter of the (Ti, Al)N films decreases as the Al content is increased. The (Ti, Al)N lattice exhibits state of distortion and leads to anisotropic scattering of free electrons, and thus the resistivity is raised in proportion to AlN mol%. The plan view of grain sizes in the (Ti, Al)N films are evaluated with the aid of field emission scanning electron microscopy (FESME). It is observed that the resistivity is reduced for (Ti,Al)N films with larger grain size.
The diffusion zone of the (Ti, Al)N films are evaluated as the penetration depth of constituent elements with the aid of SIMS. The estimated diffusion zones both toward Al contact and Si substrate are decreased for Ti0.89Al0.11N as compared to the pure TiN. The diffusion barrier effect of other Ti1－xAlxN(0.11＜x＜0.50) films is also evidenced as compared to the pure TiN. Nevertheless, the measured resistivity may be too high to be applied in the pratical IC industry for Ti1－xAlxN films with x greater than 0.1.
In addition, AES depth profiles also exhibit a smaller amount of Cu atomes diffusing into the TiN related film in the Cu/Ti0.89Al0.11N/Si system than that in the TiN film for the Cu/TiN/Si system, indicating a evident diffusion barrier effect of Ti0.89Al0.11N film
|