Stress polarity dependence of the activation energy in time-dependent dielectric breakdown of thin gate oxides

Stress polarity dependence of the activation energies in the two time dependent dielectric breakdown measurements, the constant-current injection (Q_bd testing) and the constant-voltage stressing (f_bd testing) are investigated for gate oxides with the thickness ranging from 10 to 4 nm. A remarkable polarity dependence of the activation energies appears in the t_bd testing when the oxide thickness decreases. This phenomenon is found to be due to a characteristic temperature dependence of the gate current density during the whole f_bd testing period for thinner oxides, which is considered as a result from the temperature dependence of the electron trapping process during the stressing.