On the origin of the mobility reduction in bulk-Si, UTBOX-FDSOI and SiGe devices with ultrathin-EOT dielectrics

摘要

The effects of ultrathin EOT on the carrier mobility in bulk-Si, UTBOX-FDSOI and SiGe-QW pFET devices were compared. The mobility is found to decrease dramatically with the EOT (Tinv) as a result of stronger charge and surface roughness scattering at thinner SiOx interface layers irrespective of the device technology. UTBOX-FDSOI and bulk-Si nFETs have identical mobility values (190 cm²/Vs) at Tinv=12.5Å. In the UTBOX-FDSOI device architecture, a positive back gate bias provides a strong enhancement in electron mobility. In SiGe-QW pFET devices, a 150% improvement in hole-mobility is observed with low thermal budget laser-anneal (LA).