Interfacial reaction pathways and kinetics during annealing of epitaxial Al/TiN(001) model diffusion barrier systems

Single-crystal TiN(001) layers, 60 nm thick, were grown on MgO(001) by ultr a-high vacuum (UHV) reactive magnetron sputter deposition at T-s = 700 degr eesC in pure N-2. Epitaxial Al(001) overlayers, 160 nm thick, were then dep osited at T-s = 100 degreesC without breaking vacuum. Changes in bilayer sh eet resistance R-s were monitored continuously as a function of time t(a) a nd temperature T-a during annealing while changes in bilayer microstructure and interfacial reaction pathways were characterized using transmission el ectron microscopy (TEM) and X-ray diffraction following selected annealing times and temperatures. The combined results indicate that bilayer reaction is initiated at the Al/TiN interface with the formation of a thin continuo us epitaxial AlN(001) interfacial layer in a metastable zincblende structur e. Ti atoms, released upon formation of AIN, diffuse to the Al overlayer le ading to the nucleation and growth of an epitaxial tetragonal Al3Ti layer. Reaction kinetics obtained from R-s(T-a,t(a)) curves together with TEM obse rvations of reaction pathways indicate that growth of both the AIN and Al3T i layers is limited by diffusion of reactants, with an activation energy of 2.3 +/- 0.1 eV, through the AIN blocking layer. (C) 2001 Elsevier Science B.V. All rights reserved.