CHARGE STORAGE DEPLETION REGION DISCHARGE PROTECTION

A means and method for shielding semiconductor charge storage devices (12-14) from the effects of particles or ionizing radiation (15a-b) absorbed within the bulk (31b) of the semiconductor substrate (31), by providing a free carrier shield consisting of a buried layer (31c) of very low lifetime in...

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Bibliographische Detailangaben
Hauptverfasser: VARKER, CHARLES, J, WILSON, SYD, R
Format: Patent
Sprache:eng ; fre ; ger
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Zusammenfassung:A means and method for shielding semiconductor charge storage devices (12-14) from the effects of particles or ionizing radiation (15a-b) absorbed within the bulk (31b) of the semiconductor substrate (31), by providing a free carrier shield consisting of a buried layer (31c) of very low lifetime in the undisturbed material below the depletion regions (12a, 14d) associated with the charge storage devices (12-14). The very low lifetime layer (31c) is obtained by ion implantation of a super-saturated zone of impurities such as oxygen which provide deep recombination centers and which react chemically with the substrate material (31) so as to provide thermally stable complexes which do not anneal away during post implant heating cycles. Concentrations of lifetime killing impurities significantly exceeding the solid solubility limit are achieved so that the lifetime reduction in the carrier shield region (31c) greatly exceeds that obtainable by prior art methods. Partial shielding is also provided against carriers injected by nearby junctions (13) or introduced by charge pumping during circuit operation.