X-ray diffraction and reflectometry investigation of interdiffusion in sputtered niobium-tungsten bilayers

Interdiffusion in sputtered niobium(45nm)-tungsten(45nm) bilayers upon annealing at low temperatures (T<1000K) has been investigated using X-ray reflectometry and diffraction. The accompanying changes in macrostress and microstructure have been characterized by applying the X-ray diffraction sin(2)Psi method and by qualitative evaluation of the diffraction line broadening, respectively. Annealing causes, besides interdiffusion, changes of macrostress and decrease of microstructural imperfection. Concentration profiles corresponding to diffusion lengths of only a few nanometer; were determined by simulation of the measured reflectivity patterns. The values obtained for the diffusion coefficients are compared with corresponding values obtained by extrapolation from published data for bulk materials at much higher temperatures.