Relationship Between Hole Mobility and Current Drive Enhancement in Uniaxially Strained Thin-Body SiGe-on-Insulator pMOSFETs

Hole mobility of uniaxially strained thin-body SiGe-on-insulator (SGOI) pMOSFETs was directly measured and was compared with that of biaxially strained ones for the first time. The uniaxial stress was induced by lateral strain relaxation in narrow SGOI active areas, which were biaxially strained before isolation. A unique feature of the combination of this global & uniaxial strain in the present technique enabled us to directly measure the mobility. It was found that the hole mobility in the uniaxially strained channels exhibited weaker dependence on effective field than in Si- and biaxially strained channels, resulting in higher mobility in a wide range of effective field over 1 MV/cm. It was demonstrated from the relation between the mobility enhancement and the short-channel I_d enhancement (61% for L=40 nm) that uniaxial compressive strain can provide the significant enhancement in high field or short channel carrier transport as well as the low-field mobility