A study of the mechanical behavior of thin polycrystalline platinum and platinum-ruthenium thin films

In this study, the mechanical behaviors of Pt and Pt-Ru alloy thin films have been studied using the nanoindentation and wafer curvature techniques. These films are potential candidates as electrode materials for DRAM applications. However, several reliability issues related to stress problems have arisen due to the harsh processing conditions that exist during the formation of thin film capacitors. We investigated deformation mechanisms of Pt and Pt-Ru alloy thin films for the application. The films were prepared by DC magnetron sputtering, and the composition of Ru was varied from 0 to 20 wt% by codeposition.; The local deformation behavior of pure Pt films was investigated using the nanoindentation method. The deformation behavior was studied in terms of both grain size and proximity of the indenter tip to a grain boundary. Small-scale deformation behavior was strongly related to the microstructural length scale (grain size). Dislocation emission from grain boundaries was proposed as a mechanism for the unique nanoindentation loading behaviors.; The effectiveness of solid solution strengthening was systematically explored in the Pt-Ru alloy films. Wafer curvature and nanoindentation techniques were used to investigate the stress mechanism of the films, and the influence of solid solution alloying was observed as a function of Ru content. The experimental results were compared to flow stress calculations that are based on dislocation motion in thin films. The detailed analyses of strengthening mechanisms show that the solid solution strengthening mechanism is mostly responsible for the film hardening.; The stress evolution of Pt films at elevated temperatures was also explored as a function of grain size. The stress-temperature behavior of Pt shows a dependence on the grain size. Two models, deformation mechanisms map and diffusional wedge model, were used to understand the stress-temperature behavior of Pt films. Diffusional wedge model does agree with the stress-temperature behavior of Pt films. A combination of the two models is found to be most accurate in the case of a non-columnar film.