Plan-view TEM combined with nano-probe instead of traditional methodologies to clarify GOX defect

The GOX is the most fragile element of a MOS transistor. With the scaling of device, the GOX thickness has been reduced to a few atomic layers, therefore any tiny defects in gate oxide can lead to high leakage current and even gate oxide breakdown. FIB/TEM analysis and chemical wet etching pinhole technology are usually adopted to characterize GOX leakage defect. However, TEM by FIB-cross section lift-out method suffers two challenges: one is that the shrinking devices require very thin TEM-lamella to be extracted to avoid overlapping structures, and to be prepared at the defect position; the other is that the image contrasts of Gate oxide and AA silicon are similar in FIB photograph and GOX breakdown spot cannot been observed directly, therefore it is difficult to prepare a TEM-lamella at the extract position. For wet etching technique, the original profile of gate oxide defect may be destroyed after wet etching and the initial information of the defect cannot be inspected. This paper presented a plan-view TEM by FIB lift-out method combined with nano-probe test to characterize GOX leakage defect. This method can extremely optimize traditional TEM by cross-section FIB lift-out method or chemical wet etching technology for GOX defect inspection.