An Analysis And Design For The VDMOSFET Computer Simulation

The power VDMOSFET is drawing more and more attention in all kinds of power switches due to its unique advantages such as high input impedance, fast speed shifting and heat stability. In order to reduce the power cost of device itself, the smaller the on-resistance and device size, the better the device will be. Thus, how to reduce the on-resistance and terminal structure in unit area of the device has become to a subject of great importance. Meanwhile, the dissipation power of VDMOSFET is restricted by its own heat resistance and accurate detection to the heat resistance has also plays an important role in optimal designing of the device.The paper designs an optimization to the epitaxial Layer thickness and doping concentration of the device through establishing the on-resistance R_on model, then detailed analyzes four parameters affecting on-resistance. According to the model, it analyzed a relation between how the resistance is change with the four parameters and summarizes the design theory of on-resistance. Taking advantage of MEDICI software to test the designed parameters, the results show that it can satisfy the requirements under the given voltage bearing conditions.The paper respectively builds a mathematical model to the filed limiting ring and filed plate structure of the device terminal. By analyzing the amplitude of breakdown electric field of main conjunction and ring conjunction, it optimizes the ring distance. Also, it optimizes the filed plate length and oxide layer thickness according to field plate structure model, by analyzing the amplitude of breakdown electric field of main conjunction and field plate edge. To make a summary of what has been analyzed above, it tests the device terminal by MEDICI, and it satisfies the design requirements. The paper proposes a method to detect the heat impedance of power VDMOS by taking advantage of the parasitic pn junction diode Dsd as the temperature sensing element, presents the measuring results of the temperature coefficients of temperature sensing parameters and transient heat impedance of several kinds of power VDMOS and discusses the four factors that affect much of the heat impedance detection accuracy. The conclusion is that the transient detection under some certain condition can be used to watch the chip bonding quality of VDMOS and perform fast heat choosing of the power VDMOS.