Synchrotron x-ray diffraction and transmission electron microscopy studiesof interfacial reaction paths and kinetics during annealing of fully-002-textured Al/TiN bilayers

Dense fully-002-textured polycrystalline TiN layers, 110 nm thick with a N/ TI ratio of 1.02+/-0.03, were grown on SiO2 by ultrahigh vacuum magneticall y unbalanced magnetron sputter deposition at T-s = 450 degreesC in pure N-2 utilizing high N-2(+)/Ti Aux ratios and low energy (E-N2(+) = 20 eV) ion i rradiation of the growing film. Al overlayers, 160 nm thick and possessing a strong 002 texture inherited from the underlying TiN, were then deposited at T-s = 100 degreesC without breaking vacuum. Synchrotron x-ray diffracti on was used to follow interfacial reaction paths and kinetics during postde position annealing as a function of time (t(a) = 200 - 1200 s) and temperat ure (T-a = 500 - 580 degreesC). Changes in bilayer microstructure and micro chemistry were investigated using transmission electron microscopy (TEM) an d scanning TEM to obtain compositional maps of cross-sectional and plan-vie w specimens by energy dispersive x-ray analysis. The initial bilayer reacti on step during annealing involves the formation of a continuous AIN interfa cial layer which, due to local epitaxy with the TIN underlayer, grows with the metastable zinc-blende structure up to a thickness x similar or equal t o3-5 nm, and with the wurtzite structure thereafter. Ti atoms released duri ng AIN formation diffuse into the Al layer leading to supersaturation follo wed by the nucleation of dispersed regions of tetragonal Al3Ti with inherit ed 002 preferred orientation. The aluminide domains grow rapidly until they reach the free surface; thereafter growth is two dimensional as Al3Ti grai ns spread radially. The overall activation energy for Al3Ti formation and g rowth is 1.8+/-0.1 eV. In situ synchrotron x-ray diffraction analyses durin g thermal ramping show that the onset temperature for interfacial reactions was increased by more than 100 degreesC for fully dense completely 002-tex tured bilayers compared to Ill-textured bilayers deposited by conventional reactive sputter deposition. (C) 2001 American Vacuum Society.