Nanooxidation of silicon with an atomic force microscope: A pulsed voltagetechnique

The use of an atomic force microscope (AFM) as an active tool to realize si licon nanolithography is now well known, using a continuous voltage applied between the AFM tip and the surface. The main drawback of this technique i s the poor reliability of the tip due to the strong tip-surface interaction . An original way which both increases the reliability and improves the nan olithography resolution is the use of pulsed voltages instead of continuous polarization. In such a case, the interaction time of the tip with the sur face under electric field decreases. The frequency oscillation (in nonconta ct mode) of the cantilever is taken as a reference, and pulsed voltages wit h variable phase and duty cycle are used. We show that the variation of the phase allows a 100% modulation of the oxide width. Finally, combining this lithography technique with wet etching, a 17.5 nm wide and 5.5 nm height n anowire has been obtained starting from a silicon-on-insulator substrate. ( C) 1999 American Institute of Physics. [S0003-6951(99)01326-1].