Toward Defect-Free Doping by Self-Assembled Molecular Monolayers: The Evolution of Interstitial Carbon-Related Defects in Phosphorus-Doped Silicon.

Self-assembled molecular monolayer (SAMM) doping on semiconductors has been widely appraised for its advantages of doping nanoelectronic devices for applications in the complementary metal-oxide-semiconductor transistor (CMOS) industry. However, defects introduced by SAMM-doping will limit the performance of the devices. Previously, we have found that SAMM-doping can bring carbon impurities into the silicon substrate and these unwanted carbon impurities can deactivate phosphorus dopants by forming an interstitial carbon (C)-substitutional phosphorus (C-P) complex. Herein, to develop a defect-free SAMM-doping process, the generation and annihilation of C-related defects are investigated by extending the thermal annealing time from 2 to 10 min using secondary ion mass spectrometry and deep-level transient spectroscopy. The results show that the concentration of C-related carbon defects is lower after a longer time of thermal annealing, although a longer annealing time actually introduces a higher concentration of carbon impurities into Si. This observation indicates that interstitial carbon evolves into substitutional carbon (C) that is electrically inactive during the thermal annealing process. A defect-free SAMM-doping process may be developed by an appropriate post-annealing process.