Hyperthinning of Silicon and Sio₂ for Low Power Electronic Applications

Abstract

Silicon-On-Insulator (SOI) and advanced device technologies require the ability to fabricate uniform thin films of silicon (< 50 nm) and silicon dioxide (< 5 nm). A technique for hyper-thinning silicon and silicon dioxide films to these dimensions is described. The method is based upon etching by a high flux beam of hyperthermal (2 to 14 eV translational energy) fluorine atoms generated using Physical Sciences’ FAST technology. The fluorine atom beam contains greater than 95% atoms and less than 0.1% ions. The low ion content of the beam allows damage-free processing of these films. At the available translational energies, the fluorine atom reaction probability with silicon is near unity. Hence, high rate etching can be achieved. Silicon films have been thinned at ambient temperature (20 C) to thicknesses less than 50 nm by this technique with etching rates up to 120 nm/min demonstrated. The hyperthinning is uniform and does not affect the surface finish. Analysis of the processed surface shows no evidence of contamination from the treatment. High rate etching of silicon dioxide films has also been shown. The reaction probability of hyperthermal fluorine atoms with SiO₂ films is 0.25.