The Effect of Defects on Time Dependent Dielectric Breakdown Acceleration in TiN/ZrO2/Al2O3/p-Ge Gate Stacks

Abstract

This work investigates the p-Ge/Al2O3/ZrO2/TiN gate stacks with thin GeO2 or GeOx layer, formed when the gate stack was exposed to pre- or post-deposition slot plane antenna plasma oxidation (SPAO). The post Al2O3/ZrO2 deposition SPAO forms relatively thicker GeO2 and post Al2O3 deposition SPAO forms thinner GeO2 whereas pre-deposition SPAO forms thin fragmented GeOx layer at the interface. By employing carrier transport mechanisms as a function of temperature in both gate and substrate injection mode we were able to identify the traps that contributes to the TDDB degradation. The SPAO treatment effectively removes the trap centers in ZrO2 and Al2O3 layers when SPAO was performed after the gate stack deposition. The trap center (Φt1 = 0.13 eV) observed in the ZrO2 when ZrO2 is not subjected to the SPAO, i.e. pre-deposition SPAO. This trap Φt1 (0.13 eV) was eliminated for post Al2O3/ZrO2 deposition SPAO. While defects in the ZrO2 layer determines the TDDB characteristics in gate injection mode the GeO2 or GeOx interfacial layer thickness determines the TDDB degradation in substrate injection mode. The TDDB characteristics in gate injection mode suggests that the SPAO can significantly affect the TDDB characteristics.