Nanoscopic techniques for studying dielectric breakdown and switching induced morphological changes and defects

Nanoscopic physical analysis of breakdown in high-k gate/metal stacks shows that the microstructural defects and damages induced by dielectric breakdown in high-k gate dielectric are very different from that of conventional SiOxNy/poly-Si gate stacks. Chemical analysis using transmission electron microscopy (TEM) and electrical analysis using scanning tunnelling microscopy provide useful information about the nature and evolution of the breakdown induced defects and the roles of material microstructure responsible for dielectric breakdown in metal-oxide-semiconductor field effect transistors. Together with electrical characterization, various microstructural and morphological changes at nanometer scale to the gate systems have been established. This tutorial will also report the latest TEM study on real-time high-k breakdown induced by an in-situ STM probe in TEM. The effect and role of breakdown induced microstructural changes on dielectric breakdown and recovery (or more commonly called switching) are identified. The impacts of the new breakdown and recovery mechanisms on the performance and reliability of high-k/metal gate stacks are discussed.