AES depth profiling and interface analysis of C/Ta bilayers

To study the AES sputter depth profiling of a layered structure with different layer densities and sputtering yields, a bilayer structure of C-graphite (60 nm)/Ta (50 nm) was sputter deposited onto smooth silicon substrates. The sputtering rates of C and Ta and the depth resolution, Dz, at the C/Ta interfaces were investigated using 1 and 3 keV Ar+ ions, respectively, varying the angle of incidence in the range between 228 and 828. It was found that the sputtering rates of Ta and C as well as their ratio are strongly angle dependent. The sputtering induced surface topography deteriorated the depth resolution and was studied by atomic force microscopy (AFM). The ripple structures formed on the surfaces of carbon layers during sputter depth profiling of stationary samples could be avoided by sample rotation. The measured carbon concentration profile revealed a strong electron incidence angle dependent backscattering effect on the C (272 eV) Auger signal. The measured AES depth profile obtained with 1 keVAr+ ions at an angle of incidence of 498 was compared to the theoretical depth profile calculated by the mixing, roughness, information depth (MRI) model taking into account backscattering effect of primary electrons. The measured AES concentration profile agrees well with the simulated one obtained with the MRI model.