Analysis And Optimization Of Breakdown Characteristics For 1200V Bulk-silicon LDMOS

To realize level shift function,Lateral Diffused Metal Oxide Semiconductor(LDMOS)has been widely used in high voltage gate driver ICs,for its high breakdown voltage,high switching speed and easy integration.As the core device,the breakdown characteristics of LDMOS device directly determine the performance and reliability of the high voltage gate driver ICs.At present,there is no mature manufacture platform for 1200V gate driver ICs in China,therefore,it is of great significance to carry out the optimization research on the breakdown characteristics of 1200V LDMOS for the manufacture of 1200V gate driver ICs.Based on the 1200V bulk-silicon LDMOS proposed by our research group,the breakdown characteristics of the device under the off-state,on-state and off-state dynamic avalanche are deeply studied.It is found that the breakdown spots at the off-state and on-state are located inside the device and on the silicon surface respectively,which is attributed to the vertical withstanding voltage at the drain side and the base widening effect.The off-state and on-state breakdown characteristics of the device can be improved due to the increased substrate resistivity,however,the doping non-uniformity and instability of the substrate material with high resistivity can bring adverse effects on the device.With the modification of the electric field distribution due to the excessive carriers,the hole current generated by the dynamic avalanche at the drain side activates the parasitic NPN transistor and eventually causes the thermal runaway of the device.The trigger of the parasitic NPN transistor can be delayed by increasing the doping concentration of the p-body region,however,the threshold voltage of the device increases with the higher doping concentration of the p-body region.Based on the above research and analysis,an improved device featuring charge compensation structure in the substrate is proposed.Without increasing the substrate resistivity,the off-state and on-state breakdown voltage of the device can be improved due to the optimized electric field distribution at the drain side.By providing hole current bypass flow path,the trigger threshold of the parasitic NPN transistor is increased,which can improve the off-state dynamic avalanche maximum withstanding current of the device.The simulation results show that the off-state breakdown voltage of the device is 1463V,the off-state leakage current is 3.5μA/cm~2(at the drain voltage of 1200V),the on-state breakdown voltage is1380V(at the gate voltage of 13.6V),and the off-state dynamic avalanche withstanding current of the device is 1.29A/cm~2.All the above electrical characteristics meet the design specifications,which can meet the requirements of practical application.