Current gain degradation in bipolar junction transistors due to radiation, electrical and mechanical stresses

Persistent Link:
http://hdl.handle.net/10150/282140
Title:
Current gain degradation in bipolar junction transistors due to radiation, electrical and mechanical stresses
Author:
Witczak, Steven Christopher, 1962-
Issue Date:
1996
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The current gain of bipolar junction transistors is reduced due to ionizing radiation exposure or hot-carrier stressing. Radiation-induced degradation is particularly severe at the low dose rates encountered in space. In this work, the dose rate effect in lateral and substrate pnp bipolar transistors is rigorously quantified over the range of 0.001 to 294 rad(Si)/s. Gain degradation shows little dependence on dose rate below 0.005 rad(Si)/s, suggesting that degradation enhancement comparable to that expected from space-like dose rates was achieved. In addition, the effect of ambient temperature on radiation-induced gain degradation at 294 rad(Si)/s is thoroughly investigated over the range of 25 to 240°C. Degradation is enhanced with increasing temperature while simultaneously being moderated by in situ annealing such that, for a given total dose, an optimum irradiation temperature for maximum degradation results. Optimum irradiation temperature decreases logarithmically with total dose and is larger and more sensitive to dose in the substrate device than in the lateral device. Maximum high dose rate degradation at elevated temperature closely approaches low dose rate degradation in both of the devices. A flexible hardness assurance methodology based on accelerated irradiations at elevated temperatures is described. The influence of mechanical stress on the radiation hardness of single-crystalline emitter transistors is investigated using x-ray diffraction. Correlation of device radiation sensitivity and mechanical stress in the base supports previously reported observations that Si-SiO₂ interfaces exhibit increased susceptibility to radiation damage under tensile Si stress. Relaxation of processing-induced stress in the base oxide due to ionizing radiation is smaller than the stress induced by emitter contact metallization followed by a post-metallization anneal. Possible mechanisms for radiation-induced stress relaxation and their effect on the radiation sensitivity of bipolar transistors are discussed. The combined effects of ionizing radiation and hot-carrier stress on the current gain of npn transistors are investigated. The hot-carrier response of the transistors is improved by radiation damage, whereas hot-carrier damage has little effect on subsequent radiation stress. Characterization of the temporal progression of hot-carrier effects reveals that hot-carrier stress acts initially to reduce excess base current and improve current gain in irradiated transistors. Numerical simulations show that the magnitude of the peak electric-field within the emitter-base depletion region is reduced significantly by net positive oxide charges induced by radiation. The interaction of the two stress types is explained in a physical model based on the probability of hot-carrier injection and the neutralization and compensation of radiation damage in the base oxide. The results of this work further the understanding of stress-induced gain degradation in bipolar transistors and provide important insight for the use of bipolar transistors in stress environments.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Electronics and Electrical.; Physics, Astronomy and Astrophysics.; Physics, Electricity and Magnetism.; Physics, Radiation.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Electrical and Computer Engineering
Degree Grantor:
University of Arizona
Advisor:
Galloway, Kenneth F.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleCurrent gain degradation in bipolar junction transistors due to radiation, electrical and mechanical stressesen_US
dc.creatorWitczak, Steven Christopher, 1962-en_US
dc.contributor.authorWitczak, Steven Christopher, 1962-en_US
dc.date.issued1996en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe current gain of bipolar junction transistors is reduced due to ionizing radiation exposure or hot-carrier stressing. Radiation-induced degradation is particularly severe at the low dose rates encountered in space. In this work, the dose rate effect in lateral and substrate pnp bipolar transistors is rigorously quantified over the range of 0.001 to 294 rad(Si)/s. Gain degradation shows little dependence on dose rate below 0.005 rad(Si)/s, suggesting that degradation enhancement comparable to that expected from space-like dose rates was achieved. In addition, the effect of ambient temperature on radiation-induced gain degradation at 294 rad(Si)/s is thoroughly investigated over the range of 25 to 240°C. Degradation is enhanced with increasing temperature while simultaneously being moderated by in situ annealing such that, for a given total dose, an optimum irradiation temperature for maximum degradation results. Optimum irradiation temperature decreases logarithmically with total dose and is larger and more sensitive to dose in the substrate device than in the lateral device. Maximum high dose rate degradation at elevated temperature closely approaches low dose rate degradation in both of the devices. A flexible hardness assurance methodology based on accelerated irradiations at elevated temperatures is described. The influence of mechanical stress on the radiation hardness of single-crystalline emitter transistors is investigated using x-ray diffraction. Correlation of device radiation sensitivity and mechanical stress in the base supports previously reported observations that Si-SiO₂ interfaces exhibit increased susceptibility to radiation damage under tensile Si stress. Relaxation of processing-induced stress in the base oxide due to ionizing radiation is smaller than the stress induced by emitter contact metallization followed by a post-metallization anneal. Possible mechanisms for radiation-induced stress relaxation and their effect on the radiation sensitivity of bipolar transistors are discussed. The combined effects of ionizing radiation and hot-carrier stress on the current gain of npn transistors are investigated. The hot-carrier response of the transistors is improved by radiation damage, whereas hot-carrier damage has little effect on subsequent radiation stress. Characterization of the temporal progression of hot-carrier effects reveals that hot-carrier stress acts initially to reduce excess base current and improve current gain in irradiated transistors. Numerical simulations show that the magnitude of the peak electric-field within the emitter-base depletion region is reduced significantly by net positive oxide charges induced by radiation. The interaction of the two stress types is explained in a physical model based on the probability of hot-carrier injection and the neutralization and compensation of radiation damage in the base oxide. The results of this work further the understanding of stress-induced gain degradation in bipolar transistors and provide important insight for the use of bipolar transistors in stress environments.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Electronics and Electrical.en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
dc.subjectPhysics, Electricity and Magnetism.en_US
dc.subjectPhysics, Radiation.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineElectrical and Computer Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorGalloway, Kenneth F.en_US
dc.identifier.proquest9713349en_US
dc.identifier.bibrecord.b34328634en_US
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