Hot-carrier reliability study of second and first impact ionization degradation in 0.15-mu m channel-length N-MOSFETS

The hot-carrier degradation induced by first- and second-impact ionization events is compared in advanced N-MOSFETs used for digital applications with a 3.2-nm gate-oxide thickness. Results show that the substrate enhanced el ectron injection (SEEI) mechanism is still increased in 0.15-mum channel le ngth devices with p-pockets and shallow drain junctions with a measured muc h higher injection efficiency than that in older technologies. The enhancem ent of the gate current originates from tunneling contributions and from th e secondary-primary-hot electron currents at low energy. The induced damage is explained solely by the interface trap generation and mobility reductio n in 3.2-nm thick gate-oxide devices. The difference between first and seco nd hot-carder damage is related to the extension of the degraded region tow ard the source. This is in contrast to thicker gate-oxide N-devices where t he SEEI effect is weak and where the electron trapping extends from the gat e-drain overlap region toward the source in addition to the generated inter face traps. (C) 2001 Elsevier Science B.V. All rights reserved.