Effects of interface traps and bulk traps in SiO2 on hot-carrier-induced degradation

The effects of various traps in SiO₂ or at the Si/SiO₂ interface, such as preexisting hole traps, generated electron traps, and generated interface traps, on hot-carrier-induced degradation in n-MOSFETs are discussed. Strong correlation between device degradation and the density of generated interface traps is obtained, indicating that it is mostly the generation of interface traps that causes device degradation. To clarify the reason why device degradation is related to the generation of interface traps and not other traps, the trap densities and the capture cross sections for trapping and neutralization are measured using MOSFETs fabricated with the same procedure and device dimensions as degradation-tested samples. It is found that for short injection times, carrier trapping at bulk traps dominates. For an injection time longer than 100 s, interface trap generation prevails. Therefore, device degradation is related to generated interface traps in general stress tests.