Research And Modeling On Physical Structure And Characteristics Of Power Vdmos Transistor

Power VDMOS is a widely used power semiconductor device in switched-model power converters, automotive electronics, motor control, lamp ballasts, and so forth, because it offers better performance in input impedance, switching speed, safety operating area and thermal stability than bipolar power transistor. Nowadays More than 90 percents of VDMOS products in china need to be imported. Therefore, it is very important to study and model the physical and electrical characteristic of VDMOS. Two key models for VDMOS for design and application are developed by the author.One is a new on-resistance model for VDMOS devices. The on-resistance is one of the most important characteristics of power VDMOS transistors. A new method of model is proposed based on physical structure and poisson equation. This model with a clear physical concept and analytical closed form expressions is in good agreement with simulation and experimental results. It accounts for the on-resistance variations with different parameter. In this paper, optimal design principles and physical parameters of VDMOS are obtained based on the on-resistance model.The other is an accurate SPICE model for power VDMOS. The various parasitic devices inside VDMOS are analysed and discussed. An equivalent circuit model for VDMOS is derived based on the parasitic devices. The approach and systematic procedure for parameter extraction are given. Simulated results of this model are in excellent agreement with the results obtained by MEDICI. This SPICE model is suitable for modeling the static and dynamic switching characteristics within the entire voltage range. It can unify the device linear, saturation and quasi-saturation region. The proposed SPICE model is useful as a computer-aided design tool for analysis and design of circuits of power MOSFET's. It is also available for optimum design of VDMOS because it is based on physical structure.Apart from the above two model, the other important parameters and characteristics are analysed.