Electrical characterization of stressed and broken down SiO2 films at a nanometer scale using a conductive atomic force microscope

A conductive atomic force microscope (C-AFM) has been used to investigate the degradation and breakdown of ultrathin (<6 nm) films of SiO2 at a nanometric scale. Working on bare gate oxides, the conductive tip of the C-AFM allows the electrical characterization of nanometric areas. Due to the extremely small size of the analyzed areas, several features, which are not registered during macroscopic tests, are observed. In particular, before the oxide breakdown, switchings between different conduction states and sudden changes of conductivity have been measured, which have been related to the prebreakdown noise observed in conventional metal–oxide–semiconductor structures. Moreover, similar switchings have been also measured after the oxide breakdown, which have been related to the opening or closure of conduction channels between the electrodes. The C-AFM has also allowed the determination of the areas in which the degradation and breakdown take place. The results have shown that, although degradation takes...

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