The Design Of A TRENCH DMOS With High Surge Capability

Power MOSFETs play an extremely important role in the electronic power system.With the introduction of various new structures,the performance of power MOSFETs is increasing.TRENCH DMOS,due to its low on-resistance and moderate process difficulty,has become a hot research object in the field of medium-low voltage power MOSFET.In the application of power MOSFET devices,it's unavoidable to consider the surge problem.The traditional surge protection circuits have the problems of high cost and not conducive to miniaturization.Therefore,it is also necessary to improve power MOSFETs'own surge robustness.Based on this,this article will design and implement a TRENCH DMOS with a breakdown voltage rating of 40V,high surge immunity,and low on-resistance.The specific research contents are as follows:?1?Reviews the development history of power MOSFET,analyzes the structures adopted by domestic and foreign power semiconductor manufacturers in the field of medium low voltage,and determines the design of a high surge capability power MOSFET based on TRENCH DMOS.?2?Understands the basic operating principles and key parameters of TRENCH DMOS,and the relationship between these parameters and the device structure.Analyzes the surge scenes that DMOS devices may suffer during application,the mechanism of failure under surge,and measures to improve the device's surge robustness.?3?Designs the device with simulation software.After optimization,a TRENCH DMOS structure with a breakdown voltage of 50V,a specific on-resistance of14.4m?·mm²,a threshold voltage of 3.0V,a forward pulse surge current capability of1000A or more,an inverted pulse surge current capability of 120A,an avalanche energy E_ASS of more than 10J is obtained.?4?Designs the layout of device and actualizes it,then packages and tests the chips.The basic electrical parameters of the samples are all met,with a breakdown voltage of49V,an on-resistance of 0.67m?,a threshold voltage of 3.2V,and an input capacitance of 18.2nF.In terms of surge capability,the forward pulse surge capability is more than1000A,but there is a gap between the reverse surge capability and the simulation results.The tested avalanche energy E_ASS value is only 6J,and the reverse pulse current capability of the TO247 packaging samples can only withstand to 75A.After analysis,the unsatisfactory reverse surge capability is mainly related to the design of the chip's transition area and the heat dissipation ability of the package.This paper begins with the understanding of the principles of TRENCH DMOS,and simulates the design of process and device structure.Then,the device is actualized and measured.Finally,it analyzes the inadequacies and next optimization direction.The whole process of power device from design to realization has been completed,which is of reference to the development of power VDMOS devices.