Body current model of 0.25 μm MOSFETs for hybrid-mode operation

The body current I-B Of deep submicron Lightly-Doped-Drain (LDD) pMOSFETs operating in a Bi-MOS hybrid-mode environment has been examined experimentally. An analytical I-B model, taking into considerations the impact ionization effect, the body current induced body effect and the transition from low- to high-level current injection conditions, have been developed. The proposed model is able to characterize the measured I-B results effectively over a wide range of independently applied biases (gate, drain and body) and channel lengths L (from 1 mu m down to 0.25 mu m). The proposed model is useful for circuit simulation in hybrid-mode design. On the other hand, it can be shown that as L reduces to the sub-quarter-micron regime, the impact ionization induced body current increases tremendously. A possible approach to minimize or even eliminate the inherent impact ionization induced body current in deep submicron devices has been presented. The technique also vastly improves the hybrid-mode current gain.