Oxide, interface, and border traps in thermal, N2O, and N2O-nitrided oxides

We have combined thermally stimulated-current (TSC) and capacitance-voltage (C-V) measurements to estimate oxide, interface, and effective border trap densities in 6-23 nm thermal, N2O, and N2O-nitrided oxides exposed to ionizing radiation or high-field electron injection. Defect densities depend strongly on oxide processing, but radiation exposure and moderate high-field stress lead to similar trapped hole peak thermal energy distributions (between similar to 1.7 and similar to 2.0 eV) for all processes. This suggests that similar defects dominate the oxide charge trapping properties in these devices. Radiation-induced hole and interface trap generation efficiencies (0.1%-1%) in the best N2O and N2O-nitrided oxides are comparable to the best radiation hardened oxides in the literature. After similar to 10 Mrad(SiO2) x-ray irradiation or similar to 10 mC/cm(2) constant current Fowler-Nordheim injection, effective border trap densities as high as similar to 5X10(11) cm(-2) cm are inferred from C-V hysteresis. These measurements suggest irradiation and high-field stress cause similar border trap energy distributions. In each case, even higher densities of compensating trapped electrons in the oxides (up to 2X10(12) cm(-2)) are inferred from combined TSC and C-V measurements. These trapped electrons prevent conventional C-V methods from providing accurate estimates of the total oxide trap charge density in many irradiation or high-field stress studies. Fewer compensating electrons per trapped hole (similar to 26%+/-5%) are found for irradiation of N2O and N2O-nitrided oxides than for thermal oxides (similar to 46%+/-7%). More compensating electrons are also found for high-field electron injection than radiation exposure, emphasizing the significance of border traps to metal-oxide-semiconductor long term reliability. The primary effect of nitrogen on charge trapping in these oxides appears to be improvement of the near interfacial oxide in which border traps are found.