The nature of charge trapping responsible for thin-oxide breakdown under a dynamic field stress

The trapping of positive and negative charges in silicon dioxide was studied as a function of injection current density and pulse width during dynamic high-field/high-current stress. Trapping of negative charges in oxide under dynamic stress conditions was found to give an accumulated charge to breakdown (Q
bd
) that was independent of stressing current density if the total injected charge per pulse was kept constant. However, the trapping of positive charges increased significantly as current density was increased. Under dynamic stress with fixed current density, the trapping of negative charge in the oxide increased with increasing pulse width while the trapping of positive charge was independent of pulse width. The experimental data for dynamically stressed devices suggest a strong correlation between the breakdown of thin oxides and the amount of negative charge trapped in them.