A study of the initial growth kinetics of the copper-aluminum thin-film interface reaction by i n s i t u x-ray diffraction and Rutherford backscattering analysis

Abstract

X-ray diffraction and Rutherford backscattering (RBS) analysis were used independently to investigate the interface reaction of Cu-Al thin-film bilayers during in situ annealing in the temperature range 157–220 °C. The growth kinetics of the θ-CuAl2 phase were measured and were found to follow a diffusion limited process. Using Arrhenius plots, activation energies of 1.21 and 1.24 eV and preexponential factors of 4×10−1 and 9×10−1 cm2 s−1 were obtained from x-ray diffraction and RBS, respectively. X-ray and RBS data are presented and advantages of each method are discussed. It was observed in the in situ x-ray scans that the phase γ2-Cu9Al4 grows simultaneously with θ-CuAl2 from the beginning of the interface reaction. The growth of γ2-Cu9Al4 is also diffusion limited with an activation energy of 1.59 eV and a preexponential factor of 6×102 cm2 s−1 as obtained from x-ray data. The growth of both phases is believed to be largely controlled by volume diffusion. A comparison with previous studies indicated that depending on the annealing treatment, either γ2-Cu9Al4 or β1-Cu3Al grows together with θ-CuAl2 in the initial stage of the interface reaction.