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

This paper investigates the p-Ge/Al
₂
O
₃
/ZrO
₂
/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 Al
₂
O
₃
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 ZrO
₂
and Al
₂
O
₃
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 ZrO
₂
when ZrO
₂
is not subjected to the SPAO. Trap energy level φ
_t1
(0.13 eV) was removed and φt2 (0.27 eV) still exists when only Al
₂
O
₃
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 GeO
₂
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 GeO
_x
layer enhances the interface quality and provides better immunity to degradation under stress.