A NOVEL THIN GATE-OXIDE-THICKNESS MEASUREMENT METHOD BY LDD (LIGHTLY-DOPED-DRAIN)-NMOS (N-CHANNEL METAL-OXIDE-SEMICONDUCTOR) TRANSISTORS

In this paper, we propose a novel thin gate-oxide-thickness measuremen t method by using Lightly-Doped-Drain (LDD) N-Channel Metal-Oxide-Semi conductor (NMOS) snapback characteristics. For device with thin oxide 150 Angstrom similar to 60 Angstrom and optimized LDD doping profile, the drain breakdown voltage will be oxide-thickness limited, and there fore the oxide breakdown's critical-field is about 10 MV/cm. By this c haracteristic, as high-voltage sine waveform generator provides the ne cessary voltage to lead to the grounded-gate LDD-NMOS happening gate-a ssisted drain breakdown and drives its parasitic n-p-n bipolar turn-on . The voltage-waveform collapses immediately as the applied-voltage ex ceeds the critical oxide-field MV/cm. Therefore, the oxide thickness c an be determined.