Modification and characterization of thin silicon gate oxides using conducting atomic force microscopy

Conducting atomic force microscopy (C-AFM) is used for the anodic oxidation on thermally grown gate oxide samples. The electric field distribution during the oxidation process is studied by computer simulations as function of tip radius, thermal oxide thickness and water film coverage. The results are compared with the experimental oxidation experiments. It is shown that the tip radius and its nano-roughness play an important role for the shape of the protrusions obtained by oxidation. For smooth tips, which do not exhibit high nano-roughness, formation of ring structures can be observed. For tips with higher nano-roughness, the ring structure formation is suppressed. From a comparison of the electric field distributions within the oxide with the experimental data, we concluded that the electric field near the oxide/tip interface is the driving force during the anodic oxidation process.