The effect of defects on time dependent dielectric breakdown acceleration in TiN/ZrO₂/Al₂O₃/p-Ge gate stacks

This work investigates the p-Ge/Al₂O₃/ZrO₂/TiN gate stacks with thin GeO₂ or GeO_x 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 GeO_x 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 (φ_t1 = 0.13 eV) observed in the ZrO₂ when ZrO₂ is not subjected to the SPAO, i.e. pre-deposition SPAO. This trap φ_t1 (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 GeO_x 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.