Submicron CoSi₂-structures fabricated by focused ion beam implantation and local flash lamp melting

A new way to fabricate submicron CoSi2 structures on Si wafers is presented. The method consists of a combination of focused ion beam (FIB) implantation of Co+ ions and subsequent flash lamp irradiation. With our FIB equipment IMSA-100 one- and two dimensional structures were implanted by writing with a 35 keV Co+ beam which was focused to a spot diameter of 200nm. However, for the porposed method the spot size is not the crucial dimension because the final structure size is controlled by a local melting and recrystallization process in the implanted regions. Here the structure size is determined by the amount of implanted atoms which can be concentrated by the local melting process into the submicron CoSi2 structures. The local melting is caused by heteronucleation at the Si wafer surface during the short period of superheating, which is obtained by intense flash lamp irradiation of 3 or 20 ms duration. Disintegration of implanted CoSi2 wires by precipitate formation during thermal annealing, which was reported by Liddle et al. (Mater. Res. Soc. Symp. Proc. 279 (1993) 881), can be avoided by this method. The CoSi2 structures were analysed by scanning electron microscopy (SEM) and energy dispersiv X-ray analysis (EDX). Dots and wires of about 200 nm diameter and width, respectively, have been fabricated during these first experiments, whilst smaller dimensions seem to be possible in future.