Performance and reliability comparison between asymmetric and symmetric LDD devices and logic gates

The performance and reliability of NMOSFET asymmetric lightly doped drain ( LDD) devices (with no LDD on the source side) are compared with those of co nventional LDD devices. At a fixed V-dd, asymmetric LDD devices exhibit hig her I-dsat and shorter hot-carrier lifetime. To maintain the same hot-carri er lifetime, asymmetric LDD devices must operate at lower V-dd while higher I-dsat is retained. For the same hot-carrier lifetime, ring oscillators wi th NMOSFET asymmetric LDD devices can achieve 5% (10% if PMOSFET also had a symmetric LDD) higher speed and 10% lower power, The hot-carrier reliabilit y of inverter, NAND, and NOR structures with asymmetric and conventional LD D devices is also simulated and compared.