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

HfO2/AlOx/GeOx 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 HfO2, the permittivity of HfO2 increases after the ozone postoxidation. As a result, the formed HfO2/AlOx/GeOx gate-stack exhibits an equivalent oxide thickness as thin as 0.6 nm and a D-it down to the level of 10(11) 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.