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An improved separation technique is presented for metal-oxide-silicon (MOS) capacitors, which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. The technique is demonstrated on a p-type MOS capacitor irradiated with (sup 60)C gamma rays at 100 degree C and zero bias with significant dopant deactivation.

Dielectric breakdown in thin gate oxides is studied with a bias-temperature ramp technique. Research grade 6.5 nm oxides with Al gates show variable current-temperature (I-T) response with increasing electric field, consistent with a wide breakdown distribution at room temperature. Industrial grade 7.0 nm thermal and [N.sub.2]O-nitrided oxides show well-behaved I-T plots, consistent with narrower breakdown distributions at room temperature. In all cases, temperature-to-breakdown decreases with increasing electric field. Charge-to-breakdown [Q.sub.BD] levels at elevated temperatures exceed values observed in previous work, especially for the 7 nm nitrided oxides. No. significant effect of radiation exposure on high-field oxide conduction or breakdown is observed under positive, zero, or negative radiation bias for the thermal and nitrided oxides, up to 20 Mrad(Si[O.sub.2]). Detectable radiation induced leakage current is observed only for heavy-ion equivalent doses greater than 10 Mrad(Si[O.sub.2]). These results suggest that the long-term reliability of high quality gate oxides may not be significantly degraded by radiation exposure at levels typical of system operation.

Metal-oxide-silicon capacitors fabricated in a bipolar process were examined for densities of oxide trapped charge, interface traps and deactivated substrate accepters following high-dose-rate irradiation at 100 [degrees] C. Accepter neutralization near the Si surface occurs most efficiently for small irradiation biases in depletion. The bias dependence is consistent with compensation and passivation mechanisms involving the drift of [H.sup.+] ions in the oxide and Si layers and the availability of holes in the Si depletion region. The capacitor data were used to simulate the impact of accepter neutralization on the current gain of an irradiated npn bipolar transistor. Neutralized accepters near the base surface enhance current gain degradation associated with radiation-induced oxide trapped charge and interface traps by increasing base recombination. The additional recombination results from the convergence of carrier concentrations in the base and increased sensitivity of the base to oxide trapped charge. The enhanced gain degradation is moderated by increased electron injection from the emitter. These results suggest that accepter neutralization may complicate hardness assurance test methods for linear circuits, which are based on elevated temperature irradiations.