A unified microscopic mechanism for donor deactivation in Si

Dopant atoms segregate to SiO(2)/Si(001) interfaces. This causes problems during manufacture of submicron microelectronic devices. On the basis of ab initio calculations, we identify the mechanisms by which P atoms are bonded and deactivated under the interface. We argue that P segregation occurs by (1) trapping at interfacial dangling bonds, (2) trapping at vacancies and vacancy-oxygen complexes bound under the interface, and (3) formation of pairs of threefold-coordinated P atoms. The first mechanism is important at low dopant concentrations and when no vacancies are available, the second one dominates at medium dopant concentrations after P implantation, the third one controls the segregation at dopant concentrations around 10(19) cm(-3) or higher. (C) 1999 Elsevier Science B.V. All rights reserved.