Investigation of Cs+ bombardment effects in ultra-thin oxynitride gate dielectrics characterization by DSIMS

A surface layer formation by Cs+ bombardment was observed during ultra-thin oxynitride gate dielectrics depth profiling. A significant thickness change relative to ultra-thin layer of oxynitride was noticed when testing a bombarded sample after a period of time. Cs, O and N depth profiles were examined by Dynamic Secondary Ion Mass Spectrometry (DSIMS). The bombarded sample and new sample were investigated for surface layer formation. Profile depth scale was calibrated by machine sputter rate according to a brand new standard sample with known nitride oxide layer thickness. The relationships of formed layer thickness versus bombardment time and distance were studied. This study aims to understand the effects of Cs layer formation in ultra-shallow oxynitride sample analysis to ensure accuracy of sample thickness quantification.