Focused electron beam induced etching of silicon using chlorine

Abstract

A new beam-assisted process for removing silicon from a surface in the nanometer scalein a conventional scanning electron microscope is presented. This approach isbased on focused electron beam induced etching with pure chlorine gas being usedas the precursor. In contrast to the established etching process using a focusedion beam (with or without the addition of a precursor), no amorphizationand gallium implanting of the substrate takes place. The observed low etchrates facilitate removal with sub-nanometer precision. No spontaneous etchingof silicon as in the case of xenon difluoride was observed. Etch rates of up to4 nm min − 1 could be achieved as well as a minimum feature size of below 80 nm. The effect of etchingparameters like electron beam energy, electron beam accelerating voltage or pixelspacing were systematically examined. Finally, the underlying etching mechanism interms of secondary electron interactions and precursor replenishment is discussed.