Hot Carrier Effect Of Dual Material Gate MOS FET

With scaling down of the device, the electric field and the current density of MOSFET increase sharply.And it would increase the probability of the hot carriers'formation. If the electrical field in the channel reach the critical value, the velocity of hot carriers would get to saturation.It can't improve the speed of the device,on the other hand,it would cause device failure.The reliability problems are analyzed for MOSFET in VLSI, especially for hot carrier effects due to scaling down in MOSFET. By two-dimentional device simulator MEDICI, the hot-carrier classification,the hot-carriers generation mechanism,the formation of substrate current of conventional NMOSFET are analyzed.A dual-material-gate MOSFET was proposed to suppress the hot carrier effect.The gate consists of two different materials contacting laterally and with different functions. Some parameters for the hot carrier effect of the novel device was studied systemically.First, using the multi-region potential distribution and universal boundary conditions, the two dimensional analytical models of surface potential and electrical field for the novel device were derived by solving the two dimensional Poisson's equation. According to the theory for the formation of the gate current and the substrate current, using "probability election model" to study the failure mechanism of hot carrier effect. The gate current model and the substrate current for ultra-deep submicron DMG MOSFET are proposed. By computer simulation MEDICI,it is given that the variety of the surface potential,the electrical field,the substrate current and the gate current. The simulation results tally well with the existing experimental data and theoretical models, which proves that the theories are reasonable.The characteristics of the novel device were studied as compared with the conventional MOSFET. we simulate some parameters which can surveillance the hot carrier effect efficiently, such as electric field,substrate current and gate current et al. It is clear that DMG MOSFET has better performance. It was also shown that the novel device could suppress the short channel effect, drain-induced barrier lowering effect. The gate current and substrate current are sensitive with temperature.So with the scaling down, the self-heating effect would have great influence.The lattice temperature would influence impact ionization. The occurring of impact ionization was because of lattice temperature.By simulation,we got the best structure parameter with which the device have wonderful performance.