| Summary: | Power MOSFET is the most commonly used power device due to its low gate drive power and fast switching speed compared to the existing power biplar transistor.It features a vertical structure with source and drain on opposite sides of the wafer to support higher current and voltage.The performance of power MOSFET is restricted by the internal resistance. A careful optimisation of the gate width (W G ) is required to minimise the internal resistance.Moreover, the doping concentration of N-epitaxial drift region and its thickness are chosen to obtain the desired breakdown voltage. In the device designed to support low voltage (<50 V), the doping concentration of the P-base region is comparable with the doping concentration of the N-drift region to support part of the applied voltage. The maximum doping concentration of the P-base region must be chosen to attain a threshold voltage for low voltage power MOSFET in the range of 1 - 2 V. In this study, the vital parameters in manufacturing the power VD-MOSFET,such as P-base and N-drift doping concentrations, thickness of N-drift region, and gate width are investigated. The impact of those parameters on the threshold voltage,breakdown voltage and internal on-resistance is recorded and analysed. The VD-MOSFET model used in this study is capable to withstand the breakdown voltage less than 30V. The model is simulated using 2D device and process simulation software from SILVACO; ATLAS and ATHENA. In the simulation, one parameter is varied, while the rest are kept constant.It is shown that, P-base doping concentration is significant in determining the threshold voltage.The threshold voltage is proportional to
the P-base doping concentration.On the other hand, the breakdown voltage is inversely proportional to the N-drift doping concentration.Thicker N-drift region may support higher breakdown voltage, but will increase the internal on-resistance.
|
|---|