Enhancing thin dielectric remaining detection under polysilico plug of advanced DRAM by electron beam inspection

We´ve studied using negative mode e-beam inspection (EBI) to detect a thin layer of dielectric remain at the bottom of storage node contact (SNC) hole. A thin layer (~15 nm) of nitride at the bottom of some SNC holes was intentionally created, EBI were performed at two stages: post etch clean and after silicon nitride cap of SNC plug. Negative mode EBI after SNC nitride cap deposition successfully captured these contact open defects as bright voltage contrast (BVC) defects. The cross-section scanning electron microscope (SEM) confirmed the results. The inspection mechanism is also discussed in the paper. We found that negative mode EBI is very useful for in-line defect monitoring.