Conducting atomic force microscopy studies for reliability evaluation of ultrathin SiO2 films

Topography and tunnelling current mapping of 13, 24 and 53 Å thick SiO₂ oxides on silicon substrates have been performed by combined AFM (atomic force microscopy) techniques. The topography measurements revealed an increased density of pits on the SiO₂ surface of the 13 and 24 Å oxide. This gave rise to concerns over technology reliability, and suggested further analysis. Various AFM techniques including Conducting AFM (C-AFM) and Intermittent Contact AFM (IC-AFM) have been used singly and in combination. Commercially available C-AFM tips have been observed to limit the available spatial resolution. Therefore, additional high resolution IC-AFM measurements with sharp silicon probe tips have been made by the incorporation of nanometric orientation marks grown purposely on the surface by anodic oxidation. Good correlation between the topography image of the IC-AFM and the tunneling current mapping of C-AFM in respect to the location of surface features has been observed.