NANOMETER LITHOGRAPHY ON SILICON AND HYDROGENATED AMORPHOUS-SILICON WITH LOW-ENERGY ELECTRONS

We report the local oxidation of hydrogen terminated silicon (Si) surf aces induced with the scanning-tunneling microscope (STM) operating in air and by a beam of free low-energy electrons. With STM, oxide lines were written in Si(100) and Si(110) and transferred into the substrat e by wet etching. In case of Si(110) trenches with a width as small as 35 nm and a depth of 300 nm were made. The same process has also succ essfully been applied to the patterning of hydrogenated amorphous sili con (a-Si:H) thin films. We demonstrate the fabrication of metallic 'n anowires' using a-Si:H as resist layer. With regard to the process of oxidation, it is found that the oxide written with STM is apparently n ot proportional to the electron current, in contrast to results obtain ed with a beam of free electrons in an oxygen gas-environment. The dos e needed to remove the hydrogen was determined as a function of electr on energy. This dose is minimal for 100 eV electrons amounting to 4 mC /cm2.