Instabilities of metal-oxide-semiconductor transistor with high-temperature annealing of its gate oxide in ammonia

This paper deals with the instabilities of the metal-oxide-semiconductor (MOS) transistors with nitrided oxides as gate insulators. In order to relate, and to trade off among, the instabilities, the noise behaviors, and other electrical characteristics in these devices, extensive investigations on the electrical properties - including the flatband-voltage shift, fixed-oxide charge, interface-state density, surface mobility, transconductance, and the electronic conduction in the insulating layer - were conducted with various amounts of hot-electron injections. From the noise-temperature and the interface-state density measurements, we found that the electronic trap density at the nitrided-oxide/silicon interface is significantly enhanced at around an energy level of 0.43 eV below the conduction-band edge of silicon. On the other hand, results also suggest that the nitridation of the gate insulator in a MOS transistor can improve the stabilities again by hot-electron bombardment, but suppresses the electron conduction in the inversion layer and enlarges the noise level remarkably under normal operation conditions. In addition, the degradation of the electrical characteristics of MOS transistors subjected to hot-electron stressing seems to be due to the interface-state generation rather than electron trapping.