The Space Environment

The inner and outer van Allen belts

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Ionizing radiation and semiconductor damage

Silicon dioxide develops a positive charge when irradiated. An ionizing particle passes through, and generates hole-electron pairs. The electrons are highly mobile, and diffuse or drift out, while the holes get trapped, and leave a positive charge. Hafnium oxide develops a negative charge, trapping electrons. A stack of both shows promise as a rad-hard gate oxide, withstanding 10Mrad from a Cobalt 60 source with minimal shifts. I wonder if that is tuned for !Co60? Perhaps a wider spectrum of radiation energies, as would be found in the Van Allen belt, would preferentially charge either the !HfO or the SiO2, leaving a residual imbalance? In any case, it does demonstrate how modern gate oxides may be much more rad hard than older technologies.

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Ionizing radiation, charge upsets and latchup

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Drag

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References

http://www.isde.vanderbilt.edu/content/muri_2008/dixit_muri2008.pdf Sriram Dixit et. al. at Vanderbilt University. Recent work on HfO/SiO2 stacked gates and radiation resistance.