Aggressive EOT Scaling of Ge pMOSFETs With HfO2/AlO<italic>x</italic>/GeO<italic>x</italic>Gate-Stacks Fabricated by Ozone Postoxidation

Abstract

HfO2/AlO x /GeO x gate-stacks have been fabricated on Ge surfaces by in situ ozone postoxidation method. It is found that the ultrathin GeO x 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/AlO x /GeO x gate-stack exhibits an equivalent oxide thickness as thin as 0.6 nm and a $D_{\mathrm{ it}}$ down to the level of $10^{11}$ cm $^{-2}$ eV $^{-1}$ . Ge pMOSFETs with the record high hole mobility of 417 cm2/Vs have also been realized by this gate-stack fabrication technique.