Impact of Slot Plane Antenna Annealing on Carrier Transport Mechanism and Reliability on ZrO2/Al2O3/Ge Gate Stack

Abstract

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 ( $ {\phi }_{\text{t1}} = {0.13}$ eV) remains in the ZrO2 when ZrO2 is not subjected to the SPAO. Trap energy level $ {\phi }_{\text{t1}}$ (0.13 eV) was removed and $ {\phi }_{\text{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.