Halo implant in pseudomorphic SiGe channel p-MOSFET devices to reduce short channel effect

Halo ion implantation was adopted to reduce the short channel effect (SCE) of a buried channel p-MOSFET device on pseudomorphic Si 0.70 Ge 0.30 layers. The strained pseudomorphic Si 0.70 Ge 0.30 layer of 10 nm thickness, with a Si cap layer on top, was grown using molecular beam epitaxy. The results show an overall reduction in threshold voltage ( V th ) roll-off in both Si and pseudomorphic SiGe devices. Halo implantation of As + , 120 keV and dose 2 × 10 13 cm −2 , was successfully used to reduce roll-off for the 2 nm Si cap SiGe device by 0.3 V. However, it was found that halo implantation causes the reverse short channel effect (RSCE) on the devices, which can result in V th roll-up with reducing channel length. The effect of the RSCE becomes greater with increasing Si cap thicknesses of the SiGe devices. Also, non-halo implanted devices were found to demonstrate the RSCE. This is due to excess interstitials from the source/drain implant and their subsequent diffusion, which causes virtual halo dopant to form in non-halo implanted devices.