Nanometer scale characterization of silicon dioxide thin films with conducting atomic force microscopy (C-AFM) in ultra high vacuum

S. Kremmer, C. Teichert, E. Pischler, H. Gold, F. Kuchar and M. Schatzmayr*

Institute of Physics, University of Leoben, Austria
* Austria Mikro Systeme AG, Unterpremstaeten, Austria

Conducting atomic force microscopy (C-AFM) is applied to investigate thickness homogeneity and dielectric breakdown of very thin (4-8 nm) silicon gate oxides. To realize such measurements we use the ability of the OMICRON ultra high vacuum (UHV) AFM/STM (scanning tunneling microscope) to separately scan the surface in AFM mode and apply a voltage between the conductive tip and the silicon substrate at the same time. With this setup it is either possible to detect Fowler-Nordheim tunneling currents through dielectric films or to study dielectric breakdown effects.
Here, we use the C-AFM setup to cause dielectric breakdowns on silicon gate oxides in the form of grids. From our experiments we obtain information about the distance dependence of consecutive measurements which is useful to draw conclusions about the charge distribution during electrical stressing. In addition, the effect of this breakdown measurements on the topography and the isolating behavior of the film is studied.