A Critical Gate Voltage Triggering Irreversible Gate Dielectric Degradation

Using a multiple-stage constant-voltage stress (M-CVS) methodology, a critical gate voltage (V_crit) is found to demarcate the post-breakdown (BD) gate leakage current (I_g) evolution. For a gate voltage (V_g) < V_crit, I_g digitally fluctuates with no apparent net increase. For V_g > V_crit, I_g rapidly evolves into a stable high leakage state. V_crit is found to decrease with decreasing oxide thickness (T_ox), implying that it has a significant impact on I_g degradation rate (dl_g/dt) (Lombardo, 2003) at nominal operating voltages.