Study Of Physical Characteristics And Modeling Of High-voltage VDMOS

In1979, the power VDMOS device was invented, it is one of the most widely used power device in the field of power semiconductor devices. VDMOS itself has many advantages, not other power MOS device, such as high input impedance, fast switching speed, good temperature stability, high voltage resisitance and large current capacity and so on, make the VDMOS device widely used in industrial manufacturing, computer, household appliances, digital products, and even military fields.VDMOS device has three electrodes(source electrode, gate electrode, drain electrode). Compared with the conventional MOS devices, the biggest difference is the drain electrode is located in the bottom of the device. The formation of vertical conduction channel not only improves the utilization ratio of the surface, but also raises the level of voltage resistance and current resistance.It is the importance that the study of the physical characteristics of the high-voltage VDMOS device in this paper, including the temperature characteristic, the quasi-saturation characteristic and the dynamic characteristic, and their equivalent circuit models also are set up.(1) Temperature characteristic:First, The influence of temperature on the various physical mechanism is studied, including the influence of temperature on mobility, threshold voltage and turn-on resistance. Then, RC thermal network model of the whole device is set up to simulate temperature effect. Simulating temperature characteristic and extracting data from simulation result. The equivalent circuit model of temperature characteristic is established, then. The simulation circuit is set up. The last, the accuracy of the simulation and analysis of the equivalent circuit model.(2) Quasi-saturation characteristic:First, the generation mechanism and influencing factors of quasi-saturation characteristic are studied, including the influence of the gate voltage, the distance of p-bolds and doping concentration on quasi-saturation characteristic. Then, the quasi-saturation mathematical model is established and the computational method of the gate voltage at the critical quasi-saturation region is presented. Simulating the quasi-saturation characteristic and extracting data from simulation result. The equivalent circuit model of the quasi-saturation characteristic is established, then, the simulation circuit is set up. The last, the accuracy of the simulation and analysis of the equivalent circuit model.(3) Dynamic characteristic:First, The composition of the internal parasitic capacitance and the relationship between the parasitic capacitance and the structure are studied. The influence of terminal voltage on parasitic capacitance is also studied. Simulating the dynamic characteristic and extracting data from simulation result. The equivalent circuit model of the dynamic characteristic is established, then, the simulation circuit is set up.