Thermal confinement of advanced semiconductor substrates during laser annealing

Advanced semiconductor substrate, such as silicon-on-insulator (SOI), comprises a thermally insulating layer or less conductive layer, which deprives a good thermal dissipation pathway. This gives rise to a highly non-equilibrium laser annealing and can significantly vary as compared to that in normal bulk silicon substrate. We compare the formation of ultra-shallow p⁺/n junctions in bulk silicon and SOI substrates using laser annealing in shallow-melt and non-melt regimes. Our results show that the boron distribution in the SOI substrate is always deeper and more abrupt than that in the bulk silicon substrate. The results signify a substantial thermal confinement of a greater melt extent and melting duration, induced by the thermally insulating buried oxide layer. In the non-melt regime, laser annealing produces dopant profiles of negligible diffusion and improved activation in the SOI substrate. Dopant activation can be further improved with increasing number laser pulses. The study demonstrates non-melt laser annealing in thermally insulated semiconductor substrates is a viable process in enhancing dopant activation at low laser fluence.