Physical model for enhanced interface-trap formation at low dose rates

• Published in: IEEE transactions on nuclear science Vol. 49; no. 6; pp. 2650 - 2655
• Main Authors: Rashkeev, S.N., Cirba, C.R., Fleetwood, D.M., Schrimpf, R.D., Witczak, S.C., Michez, A., Pantelides, S.T.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2002; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical models; Construction; Contracts; Degradation; Density; Dosage; Interface phenomena; Laboratories; Mathematical analysis; Mathematical models; Oxides; Poisson equations; Protons; Radiation effects; Space technology; Transport; Trapping
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2002.805387

We describe a model for enhanced interface-trap formation at low dose rates due to space-charge effects in the base oxides of bipolar devices. The use of analytical models allows one to reduce significantly the number of free parameters of the theory and to elucidate the main physical mechanisms that are responsible for interface-trap and oxide-trap formation processes. We found that the hole trapping in the oxide cannot be responsible for all the enhanced low-dose-rate sensitivity (ELDRS) effects in SiO/sub 2/, and the contribution of protons is also essential. The dynamics of interface-trap formation are defined by the relation between the proton mobility (transport time of the protons across the oxide) and the time required for positive-charge buildup near the interface due to trapped holes. The analytically estimated and numerically calculated interface-trap densities were found to be in very good agreement with available experimental data.