Role of the Si/SiO2 interface during dopant diffusion in thin silicon on insulator layers

We found that As and B diffusion in 90 nm thick Si on SiO2, silicon on insulator, samples is reduced, by similar to 20%, with respect to that of bulk Si for thermal processing in a lamp-based system. In contrast, when annealing is performed in a hot-wall furnace system and sample heating is determined by conduction diffusion length in Si-SiO2-Si samples is very similar to that occurring in bulk-Si reference samples. We demonstrate that diffusion in Si-SiO2-Si multilayer structures is primarily determined by an increased sample reflectivity, generated by the presence of the buried Si/SiO2 interface that reduces the amount of heat absorbed by the sample, rather than by the enhanced recombination of point defects at this interface. The latter phenomenon is not ruled out but plays a less relevant role in determining the measured reduction of diffusion. (c) 2006 American Institute of Physics.