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Electron beam irradiation effects in thick-oxide MOS capacitors

MOS capacitors were fabricated on n-type 〈111〉 silicon wafers with aluminum contacts. The oxide thickness ranged from 1000Å to 12,000Å. These capacitors were irradiated with an electron beam at doses of 10 11 to 10 17 electrons/cm 2 and energies of 5 kV and 15 kV. C-V measurements were made to chara...

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Bibliographic Details
Published in:IEEE transactions on nuclear science 1974-08, Vol.21 (4), p.14-19
Main Authors: Thomas, A. G., Butler, S. R., Goldstein, J. I., Parry, P. D.
Format: Article
Language:English
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Summary:MOS capacitors were fabricated on n-type 〈111〉 silicon wafers with aluminum contacts. The oxide thickness ranged from 1000Å to 12,000Å. These capacitors were irradiated with an electron beam at doses of 10 11 to 10 17 electrons/cm 2 and energies of 5 kV and 15 kV. C-V measurements were made to characterize the effects of irradiation. In the thin oxide samples and in the thick oxide samples at 15 kV, the C-V curves revealed a positive fixed charge accumulation in the oxide at dose levels above 1013 electrons/cm 2 . In the thicker oxide samples at 5 kV there was evidence of negative charge trapping at the lower dose levels changing to positive at the highest dose. In all cases, there was a reversal in the sense of the hysteresis effects in the C-V curves above 10 15 electrons/cm 2 , implying slow surface states which could follow the dc bias voltage but not the ac test signal. There was also a marked increase in the magnitude of the turn-on voltage for strong inversion implying an increase in fast surface states or lateral ionic charge nonuniformities.
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.1974.6499261