Dielectric breakdown of thin oxides during ramped current-temperature stress

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 N₂O-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_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 (SiO₂). Detectable radiation induced leakage current is observed only for heavy-ion equivalent doses greater than 10 Mrad(SiO₂). 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