Laser-focused atom beam promises smaller semiconductor features
A novel microlithographic technique has been described by a grou¥of researchers from the Department of Physics at Harvard University (Cambridge, MA). Using a beam of neutral inert gas (argon) atoms in metastable excited states, the researchers formed patterns on self-assembled monolayers (SAMs) of alkanethiolates on gold and silicon substrates; they also showed that the beams of metastable gas atoms can be spatially patterned by optical quenching with 746-nm laser light. Subsequent chemical etching transforms the patterns in the SAMs into structures of gold.
According to the researchers, this process is conceptually similar to the use of photons to expose a photographic emulsion in that "both processes use chemical development to achieve amplification of a sensitizing event." The theoretical resolution limit of this method of patterning a silicon substrate is, however, about 10 nm, whereas conventional photolithography, using an optical lens to focus a beam of light, is limited by the lens to about 100 nm. The experiments suggest a new "maskless" lithographic technique that could lead to a significant increase in the number of circuits that can be etched onto a semiconductor integrated circuit with commensurate increase in their speed and capacity.