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 c urrent-temperature (I-T) response with increasing electric field, consisten t,vith a wide breakdown distribution at room temperature. Industrial grade 7.0 nm thermal and N2O-nitrided oxides show well-behaved I-T plots, consist ent 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 e ffect of radiation exposure on high-field oxide conduction or breakdown is observed under positive, zero, or negative radiation bias for the thermal a nd nitrided oxides, up to 20 Mrad(SiO2), Detectable radiation induced leaka ge current is observed only for heavy-ion equivalent doses greater than 10 Mrad(SiO2), These results suggest that the long-term reliability of high qu ality gate oxides may not be significantly degraded by radiation exposure a t levels typical of system operation.