Self-limiting behavior of scanning-electron-beam-induced local oxidation of hydrogen-passivated silicon surfaces

The mechanism and the kinetics of electron-beam-induced local oxidation of an H-passivated Si surface in the electron energy range from 10 to 40 keV was investigated using scanning-electron-beam lithography. The volume expansion of Si upon oxidation produces a negative image surface pattern that can be imaged by atomic force microscopy. This latent pattern was used to study the dependence of the height and width of dot and line patterns as a function of the electron-beam exposure parameters. Patterns with minimum linewidth below 50 nm have been obtained. Similarly to atomic-force-microscope-induced local oxidation of Si, the height and linewidth saturate with electron dose for a given accelerating voltage. The saturation height roughly scales with the accelerating voltage, and depends more strongly on the accelerating voltage than the linewidth. The experimental results are interpreted by a mechanism that is based on charge generation and transport through the evolving insulating SiO₂ layer.