Analysis of Hot Carrier Degradation in AC Stressed N-Channel MOS Transistors using the Charge Pumping Technique

Hot carrier degradation induced during AC-stressing of NMOS transistors is evaluated using the charge pumping technique and the results are compared with those from DC-stress. Besides a degradation component that is only dependent on stress time, an additional component is observed that is proportional to the number of applied pulses (frequency * time). A strong dependency of the degradation on the shape of the gate pulse is demonstrated. The falling edge of the gate pulse is shown to be much more important than the rising edge and the width of the gate pulse determines the amount of compensation of the trapped positive charge by injected electrons.