The proliferation of complex multi-component gate stack/electrode structures and introduction of new dielectric and semiconductor materials may lead to new degradation mechanisms that complicate characterization and reliability evaluations of advanced CMOS devices. Aggressive scaling of device dimensions, which tends to increase device-to-device variability, further diminishes effectiveness of well-established test methods requiring ever increasing numbers of samples. Charge transfer across nanometer scale layers of different materials is strongly affected by the interface regions, where structure and composition are determined by inter-material interactions, which are influenced by fabrication conditions.

This trend points to a growing need for physics-based degradation models explicitly taking into consideration atomic-level material properties while being relevant to the application conditions and complementary to the widely used phenomenological approaches. The critical task is to link structural and electrical characteristics of multicomponent material stacks in order to identify and eventually control defects affecting charge transfer. Understanding of the degradation mechanism and its structural drivers enables the selection of adequate test conditions, which ensure degradation and lifetime assessments consistent with the use-conditions are obtained. We discuss limitations of the traditional methodology and provide examples of implementations of the microscopic evaluation approach.