Reliability And Optimization Of Diodes In Super-junction MOSFET

With the development of power semiconductor technology,Super Junction has been widely used in the field of medi?mm and high voltage power semiconductor devices.However,there are two main problems in superjunction devices.One is that the process is difficult to realize.The other is that the parasitic diodes with large junction area in the body are determined by the superjunction structure,which will cause the reverse recovery of the parasitic diodes.In the process,the peak current IRM?Reverse Recovery Current?is larger and the softness factor is smaller than the traditional MOSFET,which ultimately reduces the reliability of the device.To solve these problems,it is necessary to optimize the bulk diode of the superjunction MOSFET to improve its reliability.Firstly,the development of power VDMOS is introduced in theory.The basic theories of superjunction MOSFET and bulk diode are introduced emphatically,including the working principle of superjunction MOSFET,the static and dynamic electrical characteristics and the reverse recovery principle of superjunction diode.The reverse recovery characteristics of bulk diode are explained in detail from three parameters:peak current IRM,softness factor S and reverse recovery time Trr?Reverse Recovery Time?.Secondly,the relationship between the reliability of superjunction VDMOS?SJ-MOSFET?and the characteristics of bulk diode is explored based on the test phenomena in superjunction MOSFET bulk diode.Two causes of device failure are s?mmmarized:I_RM overshoot and voltage overshoot,and their mechanisms are analyzed in depth.Furthermore,the simulation software MEDICI,taking PN col?mmn doping and bulk diode carrier lifetime as independent variables,explores the change of reverse recovery parameters of each pair of bulk diodes,and concludes that the optim?mm conditions for the reliability of the optimized bulk diodes are:the PN col?mmn is at the optim?mm doping dose point Q1,and the carrier lifetime is reduced by electron IRMadiation.Then the actual device measurement is carried out to verify the conclusion by comparing the simulation data with the actual measurement data.Finally,according to the previous conclusions,the innovative structure of the leaky contact region with P-type conduction region is proposed,and the reverse recovery of the bulk diode is simulated by simulation software MEDICI.The parameters obtained are compared with the conventional SJ-MOSFET.Finally,the conclusion that the reverse recovery optimization can be achieved is drawn.