The effects of aging on MOS irradiation and annealing response

• Published in: IEEE transactions on nuclear science 2005-12, Vol.52 (6), p.2642-2648
• Main Authors: Rodgers, M.P., Fleetwood, D.M., Schrimpf, R.D., Batyrev, I.G., Wang, S., Pantelides, S.T.
• Format: Article
• Language: English
• Subjects: Activation energy; Aging; Aging effects; Amorphous materials; Annealing; Construction; Degradation; Density functional theory; Devices; hardness assurance; interface traps; Interstitials; Irradiation; Metal oxide semiconductors; MOS devices; MOSFETs; Oxides; Packaging; Quantum mechanics; semiconductor device radiation effects; Studies; Testing; Water
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2005.861079

We find that, after approximately 17 years of room-temperature storage, the irradiation and annealing responses of poly-Si-gate nMOS transistors can change significantly. For devices with 32 nm gate oxides that were stored in a nonhermetic environment, the magnitude of the threshold-voltage rebound during postirradiation annealing is much larger now than in previous tests on devices from the same wafer and packaging lot in 1988. These changes in threshold-voltage shifts during storage are primarily due to a more than 50% increase in interface-trap generation during irradiation and annealing. When these parts are baked before irradiation, the aging-related increase in threshold-voltage shift is reduced significantly. Water molecules absorbed in the device are likely candidates for causing aging-related degradation in a nonhermetic environment, so we investigated the properties of H/sub 2/O in amorphous SiO/sub 2/ using first-principles quantum-mechanical calculations based on density functional theory. We find a complex with energy that is 0.3 eV smaller than interstitial H/sub 2/O, with an activation energy of formation of