Blocking of thermally induced interface degradation in (111) Si/SiO2 by He

The interface degradation induced in (lll) Si/SiO2 by postoxidation annealing in vacuum, previously identified by electron spin resonance as intense creation of interfacial Si dangling bond defects (p(b)s: (Si3 Si)-Si-= . ) from approximate to 640 degrees C on, is found to be remarkably suppressed when annealing in He ambient. On the time scale of approximate to 1 h, He firmly blocks the degradation up to approximate to 800 degrees C, from which temperature on Pr, creation gradually rises, though much suppressed as compared to the vacuum case. At approximate to 1140 degrees C, the Ph density drops abruptly to a value (approximate to 1.7 x 10(12 )cm(-2)) about one-third that of the as-oxidized state density, indicating an electrically much improved interface. The transition results from the known thermal cooperative restructuring of the SiO2 layer, completed at approximate to 1140 degrees C. The data support the degradation model based on interfacial SiO(g) release, where He is seen as rapidly occupying the SiO accessible sites in the oxide thus inhibiting the degradation mechanism through impeding SiO removal-a prerequisite for the degradation to occur.