Major point defects, inherent and process induced, near the Si/SiO2 interface of metal–oxide–silicon structures have now been identified by electron spin resonance. The most pervasive defect is the Pb center, a trivalent silicon atom bonded to the Si at the interface, with dangling orbital aimed into the SiO2 (e.g., .Si≡Si3). The Pb orbital is the source of about one-half of the electrical interface traps (density Dit) in as-oxidized or radiation- or injection-damaged Si. Concentration of Pb is dependent on oxidation and other thermal treatments, and is a sensitive gauge of interface physicochemical disposition. Radiationlike processing methods—ion implantation, rapid thermal annealing, plasma etching, and electron-beam lithography—generate additional point defects, including charged E′ centers (O3≡Si. . . . +Si≡O3), nonbridging oxygen hole centers (O3≡Si–O. . . . H–O–Si≡O3), peroxy radicals (O3≡Si–O–O. . . . Si≡O3) in the oxide, and D centers (.Si≡Si3)n in the silicon. Subsequent thermochemical treatments yield results similar to those observed for bulk fused SiO2 defects, but with some unresolved differences. The stability or hardness of Si/SiO2 devices appears to be related to initial defects, despite apparent anneal by thermal processing stages. A number of studies to define the detailed physicochemical behavior of these potentially troublesome defects are now in progress.
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Poindexter et al. (1988) studied this question.