Permanent Ionizing Radiation Effects in Dielectrically Bounded Field Effect Transistors

The permanent ionizing radiation effects resulting from the use of dielectrics to bound FET structures have been experimentally determined for a total ionizing dose up to 108 rads (Si) and for various dielectric isolation techniques. The experimental vehicles used for making these determinations were dielectrically isolated JFET´s operated in such a manner that they behaved as a combination junction-MOS field-effect transistor. The experimental results observed by measuring the saturation current, turn-off voltage, maximum transconductance, and channel conductance of the junction FET show a non-monotonic relationship in the effects of a positive charge build-up in the silicon dioxide isolation dielectric with increasing dose. A theoretical model is derived for calculating the interface charge density as a function of the measurable JFET device parameters.