Low-voltage hot-electron currents and degradation in deep-submicrometer MOSFETs

Hot-electron degradation in deep-submicrometer MOSFETs at 3.3 V and below is studied. Using a device with L_eff = 0.1 μm and T_ox = 75 angstrom, substrate current is measured at a drain bias as low as 0.7 V; gate current is measured at a drain bias as low as 1.75 V. Using the charge-pumping technique, hot-electron degradation is also observed at drain biases as low as 1.8 V. These voltages are believed to be the lowest reported values for which hot-electron currents and degradation have been directly observed. These low-voltage hot-electron phenomena exhibit similar behavior to hot-electron effects present at higher biases and longer channel lengths. No critical voltage for hot-electron effects (such as the Si-SiO₂ barrier height) is apparent. Established hot-electron degradation concepts and models are shown to be applicable in the low-voltage deep submicrometer regime. Using these established models, the maximum allowable power-supply voltage to insure a 10-yr device lifetime without using LDD (lightly doped drains) is determined as a function of channel length (down to 0.1 μm) and oxide thickness.