The Research And Design Of 30V Power UMOSFET

As the core component of power electronics,power semiconductor devices are not only used for power conversion and circuit control of power equipment,but also a communication bridge between weak current control and strong current operation.The main function is power management and amplification,voltage transformation,also current and frequency conversion,which play a key role in the normal operation of the equipment.With the coming of the age of Internet,energy saving and emission reduction require power devices having a lower on-resistance while ensuring high withstand voltage.This article will complete the optimized design of the 30 V trench power field effect transistor(UMOSFET),and reduce the on-resistance under the premise of ensuring the withstand voltage,thereby reducing the conduction loss,then achieving energy saving and emission reduction.This article first summarizes the research background,development process and direction of power MOSFETs.Next,it describes in detail about the working principle of UMOSFET,also the internal physical phenomena under different gate voltages,as well as its withstand voltage and conduction principles.Then,the important electrical parameters of power UMOSFETs is introduced,with the influence factors of each parameter and the corresponding adjustment direction from the perspective of semiconductor physics.Secondly,this article provides details on the process used by the UMOSFET and the corresponding role of each step.Afterwards,to simulate and optimize the cell part of the UMOSFET,it select the preliminary epitaxial structure parameters through theoretical calculations,with the simulation results of which to optimize the thickness of the depletion layer,which successfully achieved reducing on-resistance without changing its breakdown voltage.What's more,it studied the depth of the trench which change within a certain range.It was found that a too narrow trench would cause the change of UMOSFET breakdown position,also the breakdown type became a simple PN junction breakdown with the reducing voltage.Then with the threshold voltage precisely controlling,the influence of different square resistance polysilicon gate electrodes on the threshold voltage was studied.Finally,the electrical parameters of the cell were measured,and they all met the design targets.The fourth chapter studies the terminal part.It uses a trench termination structure,one of the advantage of which is no need of field oxides that can save a mask;another is a small length of the trench termination can effectively reduce the chip area,which would also help to improve the yield.The location of the trench termination is the focus of this structure.Studies have found that both the location of the trench and the thickness of the oxide layer affect the breakdown location of the termination structure,and thus its breakdown voltage.This paper analyzes the simulation results to find out the reason for the change of the breakdown position and optimizes it.Finally,it draws the layout according to the design parameters mentioned above,and analyzes the tape-out results that are basically consistent with the simulation values,and reached the design targets.