Oxidation State Modification in Gate Dielectric for Ge nMOSFET With Mixed Hydrogen and Ozone Plasma Pretreatments

An ozone-based plasma pretreatment was proposed to reduce the oxygen vacancy and unstable germanium (Ge) suboxide (GeO
$_{\textit{x}}\text{)}$
at lower interface of interfacial layer (IL). With higher oxidizing ability of ozone and lower plasma damage in process, the formation of unstable GeO
$_{\textit{x}}$
at lower interface of IL can be effectively suppressed. The devices with a mixed hydrogen and ozone plasma (MHOP) pretreatment exhibit an ultrathin equivalent oxide thickness (EOT) of 0.57 nm, a fairly acceptable gate leakage current density of 3
$\times$
10
$^{-\text{3}}$
A/cm
$^{\text{2}}$
, lower interface trap density of 10
$^{\text{11}}$
cm
$^{-\text{2}}\cdot$
eV
$^{-\text{1}}$
, and fewer border traps in Ge MOS capacitor. Also, a higher driver current of 1.4 mA, a lower subthreshold swing (SS) of 113 mV/dec, and higher ON/OFF current ratio of 3.2
$\times$
10
$^{\text{3}}$
for Ge MOSFET can be achieved with an MHOP treatment.