Diffusion barrier performance of thin Cr films in the Cu/Cr/Si structure

The Cu/Cr/Si structure was studied for thermal stability using thin Cr layers as a barrier in the range of 10 to 40 nm, between 250 and 500°C for 30 min. Investigations using sheet resistance method, deep level transient spectroscopy (DLTS), X-ray diffraction (XRD) analysis, Rutherford backscattering spectroscopy (RBS), and adhesion tests were carried out, to reveal the behavior of Cu and Cr in the Cu/Cr/Si structures. It is shown that even a 10-nm thin Cr layer preserves the multilayer structure up to 400°C and that Cu silicide formation is observed only after annealing at 450°C. However, as found by DLTS, compared with the conventional characterization techniques, Cu migration into the structure reduces the effectiveness of the Cr layers as a diffusion barrier at 50°C.