Reducing ultra-shallow boron diffusion using carbon and fluorine co-implantation

A method to reduce the diffusion of boron in ultra-shallow junctions (USJ) has been found using the co-implantation of fluorine and carbon. In this 24 designed experiment a 40% reduction of B diffusion in the presence of a shallow F and C implant was found over the use of F alone. In addition another 10% reduction of B diffusion can be obtained if a medium dose arsenic implant is preformed before F and B implantation. It has been found that implanting in this order significantly alters the defect structure of the USJ and suggests that F trapped in the lattice after anneal may be tied up in vacancy fluorine clusters which increase B activation.