Substrate bias effect on Ge pMOSFETs with and without halo

The impact of the substrate bias (V_BS) on the short-channel effect (SCE) in Ge-channel pMOSFETs with and without halo implantation has been studied. It is shown that the threshold voltage roll-off worsens for reverse (positive) V_BS in the case of the no halo transistors, while no marked degradation of the SCE is found for the halo devices up to V_BS = +1.5 V. At the same time, a reduction of the extracted peak mobility in linear operation with V_BS has been found. The well doping density derived from the substrate sensitivity appears to be a factor of two higher than found from TSUPREM simulations. This questions the validity of the use of this parameter in case of two-dimensional doping profiles. From a comparison with simulated data, it becomes clear that process simulations require further optimization with respect to germanium implantation profiles.