The formation of a nanometer-size oxide pattern on silicon using a scanning probe microscope (SPM) has been widely reported in the literature. No analytical model has been proposed, however, to explain the variation of the oxide height with both polarization and speed of the SPM tip. In this letter, we explain quantitatively the variation of the oxide height with the polarization and the speed of the tip with a model based on field induced oxidation. Data analysis also allows us to estimate the thermal activation energy of the oxidation process, (∼0.15 eV). This low value is compared with activation energies measured for thermal and plasma oxidation of silicon.

This article proposes an enhanced oxidation model for scanning probe microscope (SPM) nanolithography that reproduces the power-of-time law reported for tip-induced anodic oxidation. It is shown that the space charge resulting from nonstoichiometric states strongly limits the oxidation rate. The direct relationship between the oxide thickness and time is provided by integration of the oxide rate equation. Measurements on SPM-induced oxides generated on a titanium surface are compared to theory. The predominant role of the space charge is corroborated by electrical measurements on oxide barriers that exhibit current fluctuations due to Coulombic effects.