Reduction of surface roughness and defect density by cryogenic implantation of arsenic

A defect-free diffusion layer is found to be formed by the cryogenic ion implantation technique for arsenic dopants. The following thermal annealing completely recrystallizes amorphous layers through solid-phase growth, eliminating dislocation growth. Furthermore, substrate cooling drastically suppresses the melting of the substrate surface. It is considered that, owing to the ability to absorb thermal energy brought about by cooling the substrate, the number of local microvoids formed by vacancy clusters is reduced and interstitial clusters are not easily enlarged, leading to surface roughness reduction. The substrate-cooling technique is very effective for suppressing recrystallization bought about by the self-annealing effect, and it is a very effective technology not only for reducing the defect density but also for improving the Si/SiO2 interface state density.