High-Field Transport Investigation for 25-nm MOSFETs With 0.64-nm EOT: Intrinsic Performance and Parasitic Effects

Low- and high-field transports are investigated for HfO₂-based MOSFETs with ultrathin equivalent oxide thickness (UTEOT) achieved by a remote interface layer (IL) scavenging method. A detailed comparison with a SiON reference demonstrates none of the detrimental effects from HfO₂-related Coulomb nor phonon additional scattering on the high-field velocity. Increased surface roughness may reduce the high-field velocity by 20% for the device with the thinnest IL. This is explained by an increase of the backscattering which reduces the ballistic efficiency for the shortest devices . However, the on-state current for UTEOT devices has the best performance at a given high-lateral-field velocity. Therefore, EOT scaling remains a valid tool for I_ON-performance improvement for CMOS scaling also with new architectures and substrates.