Aggressive EOT Scaling of Ge pMOSFETs With HfO2/AlOx/GeOx Gate-Stacks Fabricated by Ozone Postoxidation

HfO
₂
/AlO
_x
/GeO
_x
gate-stacks have been fabricated on Ge surfaces by in situ ozone postoxidation method. It is found that the ultrathin GeOx interfacial layer beneath the high-k capping is formed by the ozone postoxidation, yielding the sufficiently low density of interface traps. In addition, due to the crystallization of HfO
₂
, the permittivity of HfO
₂
increases after the ozone postoxidation. As a result, the formed HfO
₂
/AlO
_x
/GeO
_x
gate-stack exhibits an equivalent oxide thickness as thin as 0.6 nm and a D
_it
down to the level of 1011 cm
^-2
eV
^-1
. Ge pMOSFETs with the record high hole mobility of 417 cm
²
/Vs have also been realized by this gate-stack fabrication technique.