The use of surface oxide and MBE-grown multi-layers as an inorganic resist for nano-patterning

Various kinds of semiconductor microstructures have been fabricated based on the conventional lithography where a mask pattern is projected on a photoresist using light, electron beam, or X-ray. However, this lithographic process has a potential difficulty in the control on nano-scale due to the resolution limits of the mask and photoresist to be patterned on the substrate. In order to overcome theses resolution limits for nano-scale patterning, we propose here a novel method using surface oxide and MBE-grown multi-layers as an inorganic resist. One particular advantage of employing these resist materials is a superior controllability in thickness and uniformity compared with the case of organic resist due to the different methodology of epitaxial growth. Functionality as a resist is developed by the direct irradiation of 30 keV focused Ga ion beam (FIB). The area irradiated performs as either negative or positive resist against the subsequent in-situ layer-by-layer etching, depending on the amount of Ga/sup +/ dose. The negative resist (etch-stop region) is produced by the FIB-induced oxidization of the surface, while the positive resist (etch-enhanced region) by the FIB-induced amorphization or sputtering of the bulk. We call this integrated multi-process as in situ maskless-nanolithography.