Aging Effects and Latent Interface-Trap Buildup in MOS Transistors

Effects of similar to 35 years of aging during storage are investigated on the radiation response and 1/f noise of Oki nMOS and pMOS transistors with high oxygen vacancy densities in SiO2. Short-term interface-trap buildup during irradiation is enhanced significantly, relative to that observed in 1989, 1997, and 2008. In contrast, a similar latent interface-trap buildup is observed for aged pMOS devices irradiated and annealed at room and elevated temperatures at positive bias in this and earlier studies. The significant latent interface-trap buildup is observed for nMOS devices irradiated at 0 V and annealed at room and elevated temperatures under positive bias, a condition not evaluated in prior work. Results strongly suggest that latent interface-trap buildup is due to H-2 diffusion and dissociation at charged or dipolar O vacancies in SiO2, followed by proton transport to the Si/SiO2 interface and reactions with Si-H complexes. Models that attribute latent interface-trap buildup to long-term proton trapping at O vacancies in SiO2 appear to be ruled out by these results. Additional insight is provided into mechanisms of postirradiation interface- and border-trap buildup after long-term MOS device storage.