High re-activation and precise diffusion control of epitaxial Si:P layers using flash lamp annealing

Abstract Highly phosphorus-doped silicon epitaxial layers have attracted attention as a promising source-drain material for nFETs. However, one of the present challenges is to re-activate impurities which become de-activated by subsequent thermal processing. In this work, we demonstrate high re-activation while constraining dopant diffusion by using FLA, thanks to low-thermal-budget treatment with annealing times in the millisecond range. The results show the sheet resistance could be reduced by 16% with a minimal diffusion length of 0.1 nm using FLA, in contrast to over ~ 3.1 nm using RTA. Additionally, we also demonstrate precise diffusion control in the sub-nm range, which is important for advanced devices. Using the flexible annealing times of FLA, which is capable of adjustment in the sub-millisecond range, we achieved controllability down to 0.8 nm/ms in Si:P epitaxial layers without degradation of the activation level. These results indicate FLA can effectively reduce parasitic resistance, leading to high performance devices. Graphical abstract