Analysis of Co/Cu multilayers by SNMS reverse depth profiling

Abstract

The overall quality of multilayer thin films prepared by electrodeposition could strongly be influenced by the surface and interface roughness. The roughness, however, may increase with the number of layers. For that very reason the reliable analysis of the first few layers is essential. However, in depth profiling methods based on sputtering techniques the first layer is always found at the bottom of the sputter crater. Since the depth resolution might decrease during sputtering, the analysis of the first few layers is often very difficult. In order to circumvent this problem, we performed SNMS depth profiling in the direction from the substrate. We prepared thin film samples in two ways. First, Co/Cu multilayer stacks were electrodeposited on Si/Cr/Cu substrates and SNMS depth profiling was carried out from the direction of the topmost layer. Secondly, electrodeposited Co/Cu multilayer stacks were coated with a few microns thick Ni layer and detached from the Si substrate in order to study the film structure from the side of the substrate. Using this latter method, which we denote as “reverse depth profiling”, we were able to analyze the first and, probably, the most even layers of the thin film structure with high resolution.