Studies on Halo Implants in Controlling Short-Channel Effects of Nanoscale Ge Channel pMOSFETs

We report the impact of halo implants on short-channel effects of nanoscale Ge channel pMOSFETs in terms of different electrical device parameters such as threshold voltage ( $V_{\rm TH}$ ), subthreshold slope (SS), and drain-induced barrier lowering. The analysis is based on 2-D surface potential approach taking into account the interface-trapped-charge density, the fixed-oxide-charge density, and halo implants. The higher value of halo concentration as well as halo length shifts the $V_{\rm TH}$ toward the more negative value making pMOS devices suitable for circuit applications and also reduces SS. A design space defined by halo concentration and halo length for $V_{\rm TH}$ almost independent of channel length has been predicted for Ge pMOS devices with gate lengths down to 20 nm. Results obtained from our model show excellent agreement with numerical simulation data obtained using ATLAS and with reported experimental data.