Mechanics of microelectronics structures as revealed by X-ray diffraction

Abstract

The presence of strain distributions within semiconductor features influences many aspects of their behavior. For example, microelectronic technology that incorporates strained silicon improves device performance by increasing carrier mobility in the Si channels. Because current semiconductor fabrication contains multiple levels of metallic and dielectric structures, an understanding of the mechanical response of the constituent elements is critical to the prediction of the overall device performance. In addition, the interaction of strain fields between adjacent structures becomes greater as feature sizes decrease and the corresponding feature density increases. The use of synchrotron-based X-ray methods allows one to determine the interaction between strained features and their environment at a submicron resolution. Real-space mapping of strain distributions in pseudomorphically strained, raised SiGe structures revealed that elastic relaxation extends approximately 20 times the feature thickness from their edges. X-ray topographic methods were also applied to map the substrate deformation induced by overlying SiGe features. A formulation based on the classical Ewald-von Laue theory of dynamical diffraction was derived to match the measured diffraction profiles.