Design Of GCT VLD-FLR Composite Edge Terminal Structure

High-power deep junction devices usually use mesa angle grinding technology and lateral variable doping(VLD)technology to improve their terminal breakdown voltage,but because the VLD doping profile is difficult to accurately control and sensitive to surface charge,it can not effectively guarantee the terminal.Withstand voltage characteristics and reliability.In order to solve the above problems,a 4.5kV GCT is taken as an example to propose a lateral variable doping-field limiting ring(VLD-FLR)composite terminal structure.The two-dimensional numerical simulation and research are carried out by Sentaurus-TCAD software.The main contents are as follows:First,in order to alleviate the electric field concentration problem at the end of the VLD terminal and improve its reliability,a two-stage VLD-FLR composite terminal structure is proposed.The terminal structure uses a deep and shallow junction two-stage VLD to increase the radius of curvature of the depletion layer,and a higher concentration field limit ring is added at the end to reduce the sensitivity of the terminal breakdown voltage to the surface charge.Two kinds of process realization schemes of the two-stage VLD-FLR composite terminal are analyzed.The electrical characteristics of the composite terminal are analyzed according to the doping profile,and the terminal structural parameters are determined,and the electric field intensity distribution,current density distribution and breakdown of the device are combined.The characteristic curve studies the pressure resistance mechanism of the composite terminal.Finally,the influence of terminal structure parameters on terminal breakdown voltage is analyzed.The process tolerance of deep and shallow VLD-FLR terminals is discussed.Secondly,in order to solve the problem of large area of the deep and shallow VLD-FLR composite terminal chip,a shallow junction VLD-FLR composite terminal structure is proposed.The terminal structure uses only the shallow junction VLD and the higher concentration field limit ring.The three process realization schemes of the shallow junction VLD-FLR composite terminal are analyzed.The electrical characteristics of the composite terminal are analyzed according to the doping profile,and the terminal structural parameters are determined.The electric field intensity distribution,current density distribution and breakdown characteristics of the device are combined.The curve is used to study the withstand voltage mechanism of the composite terminal,and the process tolerance of the shallow junction VLD-FLR terminal is discussed.Finally,the breakdown voltage,breakdown point position,terminal size and process tolerance of the deep and shallow VLD-FLR and shallow junction VLD-FLR composite termination structures are compared and analyzed.Thirdly,the effects of fixed charge density in high,low temperature and passivation films on the breakdown characteristics of deep and shallow VLD-FLR and shallow junction VLD-FLR composite terminals were compared and analyzed to find the optimal process scheme.