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 (t(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 t(bd) testing period for thinner oxides, which is considered as a result from the temperature dependence of the electron trapping process during the stressing.