Impact of slot plane antenna annealing on carrier transport mechanism and reliability on ZrO₂/Al₂O₃/Ge Gate Stack

This paper investigates the p-Ge/Al₂O₃/ZrO₂/TiN gate stacks that were subjected to different slot plane antenna oxidation (SPAO) conditions: 1) prior to any high-k atomic layer deposition (ALD); 2) in between Al₂O₃ and ZrO₂ALD layers; and 3) after the ALD of high-k layers. The carrier transport mechanisms as a function of temperature on these samples were observed to be different. The SPAO treatment effectively removes the trap centers in ZrO₂ and Al₂O₃ layers depending on the SPAO treatments. Fowler-Nordheim tunneling seems to be the dominant transport mechanism at high field range when SPAO was performed after the high-k layers were deposited. On the other hand, Poole-Frenkel emission and hopping conduction mechanism are dominant for other two samples in both gate electron injection and substrate electron injection (SEI) modes. The trap center (φ_t1 = 0.13 eV) remains in the ZrO₂ when ZrO₂ is not subjected to the SPAO. Trap energy level φ_t1 (0.13 eV) was removed and φ_t2 (0.27 eV) still exists when only Al₂O₃ oxide layer was exposed to SPAO. Hopping distance, a (about 0.3 nm) is extracted by hopping conduction model. After time dependent dielectric breakdown measurement, it was found that if GeO2 exists at the interface then it can be degraded easily by SEI stress. On the other hand, if SPAO was processed in between the high-k layers the formation of a GeOx layer enhances the interface quality and provides better immunity to degradation under stress.