A COMPARISON OF SI-SIO2 INTERFACE-TRAP PROPERTIES IN THIN-FILM TRANSISTORS WITH THERMAL AND PLASMA-NITRIDED OXIDES

In this work, electrical properties of the Si-SiO2 interface have been investigated in terms of interface-trap parameters (emission time, ca pture cross-section, state density) by standard and three-level charge pumping techniques in n-channel thin-film (8 nm) metal-oxide-semicond uctor field-effect transistors. Some of the devices have been nitrided in an ammonia plasma reactor and reoxidized in oxygen. For nitrided d evices, a significant decrease of interface state density, D-it, has b een observed as compared with pure oxide devices. This reduction clear ly corresponds to both an uniform decrease of D-it over the silicon ba nd gap and a decrease of a D-it peak in the upper part of the band gap . The evolution of capture cross-sections has been also monitored and found to significantly vary for electron traps. This substantial chang e in electron interface-trap properties could be at the origin of the augmentation of the high field transconductance: observed for these n- channel devices after such a nitridation process.