Impact Ionization and Interface Trap Generation in 28-nm MOSFETs at Cryogenic Temperatures

The characterization of impact-ionization (II) and stress-induced damage in 28-nm bulk n-channel MOSFETs is used to identify the mechanisms for carrier-induced interface trap generation (ITG) from 300 K to 77 K. The energy-driven paradigm of hot carrier effects is used to study carrier-induced ITG and its temperature dependence, and to analyze the influence of electron-electron scattering (EES) on carrier-induced degradation of ultra-short channel devices. The analysis clearly illustrates the significant role of EES in the hot (i.e., high-energy) carriers single particle mechanism of ITG, as well as its contribution to the cold (i.e., low-energy) carriers multiple particle mechanism of ITG. This is evidenced through extractions of ITG lifetime as a function of temperature and stress current from measurements of 28 nm n-channel devices. We apply a simple model to discuss the impact of EES on the experimentally observed trends for II and ITG rates.