Effective Mobility Enhancement Through Asymmetric Strain Channels on Extremely Thin Body (100) GOI pMOSFETs

The impact of asymmetric compressive strain on electrical properties of (100) Ge-on-insulator (GOI) pMOSFFETs with body thickness (
${T}_{\text {body}}$
) ranging from 10.6 to 3.0 nm thick is experimentally investigated. The asymmetric compressive strain channels are realized by using a Ge condensation technique and patterning channels with narrow channel width (
${W}_{\text {ch}}$
), resulting in over 85% relaxation of transverse stress at
${W}_{\text {ch}}$
less than 75 nm, which is reaching quasi-uniaxial strain Ge channels. It is found that the electrical properties of the
${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$
ratio and the subthreshold swing (SS) are much improved as the GOI channel strain approaches uniaxial one. Moreover, the maximum effective hole mobility (
$\mu _{\text {eff}}$
) up to 1120 and 181 cm
²
/Vs is achieved on 10.6- and 3.0-nm-thick GOI pMOSFETs, respectively, with quasi-uniaxial strain along
$\langle 110\rangle $
direction, leading to
$3.1\times $
and
$2.4\times $
mobility enhancement against biaxial strain channels at
${N}_{s}$
of
${1}\times {10}^{{13}}\,\,{\text {cm}}^{-{2}}$
, attributable to strong valence band warping and effective mass reduction.