Behavior of Transition Metals Penetrating Silicon Substrate through SiO2 and Si3N4 Films by Arsenic Ion Implantation and Annealing

The behavior of metals penetrating the silicon substrate through a screen SiO2 or Si3N4 film by the collision of arsenic ion and surface metals are quantitatively demonstrated. We have found using silicon step etching followed by ICP-MS and SIMS that 0.1∼8% of surface metals (Fe, Cr, Ni, Cu, and W) penetrate silicon even when implanted through screen SiO2 film, depending on metal species and the film thickness. The surface metals on a CVD Si3N4 film can also penetrate into the silicon during ion implantation and/or subsequent annealing. W is most difficult to penetrate the thermally-grown SiO2 film, while W and Cr can easily penetrate a CVD Si3N4 films. We have also found using microwave photoconductive decay measurements that recombination centers are generated in silicon by low level metal penetration even when implanted through screen SiO2.