Topographical modification of silicon oxide using a conducting atomic-force microscope

Local modifications of silicon gate oxide surfaces are exploited to fabricate structures on the nanometer scale. A conducting Atomic Force Microscope (C-AFM) in contact mode is used to apply voltages to silicon samples with a thermal oxide grown on top. Protrusions are formed by electrically induced oxidation for positive or negative voltages between sample an tip. The influence of the polarity of the applied voltage on the oxidation mechanism is investigated in detail. Further the electrical properties of the formed oxide protrusions at positive sample bias are studied in comparison to the thermally grown oxides, using a Fowler-Nordheim tunneling analysis of the I-V curves. It was found that the oxidation at opposite voltage polarities applied to the sample is driven by different mechanisms. The electrical characteristics of protrusions formed due to oxidation show significant differences to the initial characteristics of the thermal gate oxide.