INFLUENCE OF DAMAGE ON THE FORMATION OF COSI2 BY CO IMPLANTATION

(111) Si samples were implanted first with 250 keV Co+ ions and afterw ards with 30 keV Co+ ions. In one case, the low-energy implantation is performed at an subcritical dose (provides no continuous CoSi2, layer after annealing) and the high-energy implantation is performed at abo ut the critical dose. In the other case the situation is vice versa. A dditionally, a single implantation of 30 keV Co+ ions at an subcritica l dose was carried out. The evolution of the CoSi2 crystallites in the non-continuous CoSi2 layers has been investigated by RES and TEM. It is shown to be different in Si predamaged by the previous Co implantat ion and in virgin Si. The damage accelerates the dissolution of the Co Si2 crystallites and the growth of the continuous CoSi2 layer. This ri pening process is faster than Ostwald ripening because the damage enha nces the contribution from the Co diffusion and, obviously, it makes t he Si diffusion to contribute also to the ripening. The strain (one pa rt of the damage) influences the shape and orientation of the CoSi2 cr ystallites. This causes the CoSi2 crystallites in predamaged Si to be always predominantly of A-type which explains the influence of the seq uence of the implantations and annealing(s) on the orientation of the resulting CoSi2 layer found in recent publications.