Experimental Investigation of Remote Coulomb Scattering on Mobility Degradation of Ge pMOSFET by Various PDA Ambiences

The impact of various postdeposition annealing (PDA) ambiences (N
₂
, O
₂
, and NH
₃
) on the hole mobility of germanium (Ge) pMOSFET with GeO
₂
/Al
₂
O
₃
gate-stack is investigated. It is found that the mobility is about 10% higher after N
₂
PDA, while it is about 10% smaller after O
₂
and NH
₃
PDA than that without PDA. The physical origin is attributed to the remote Coulomb scattering. The Ge/GeO
₂
interface charge Q
₁
decreases, but the GeO
₂
/Al
₂
O
₃
interface dipole Q
_dipole
increases after PDA in N
₂
, O
₂
, and NH
₃
. The higher mobility after N
₂
PDA is due to a smaller Q
₁
and Q
_dipole
, while the lower mobility after O
₂
and NH
₃
PDA is due to a larger Q
_dipole
. All these three PDA ambiences are beneficial to reduce the gate leakage current. Therefore, PDA in N
₂
is a balance approach for both the hole mobility improvement and gate leakage current reduction.