Structural Design And Research On Mechanism Of Low-loss Insulated Gate-controlled Power Devices

The insulated gate-controlled power devices hold a large part of power semiconductor market and one of the most typical devices is power MOSFET.Owing to the advantages of high breakdown voltage(BV),low on-state loss,high switching speed,high input impedance,and compatibility with integrated circuit,the lateral double diffused MOSFET(LDMOS)becomes popular in power IC.The core purpose of designing LDMOS is to realize high BV and high power density,namely low specific on-resistance(R_ON,SP).However,BV and R_ON,SP are limited by the“Silicon Limit”relationship.Aiming at this problem,the author proposed and fabricated two novel devices with low power loss based on accumulation-mode LDMOS.1.An accumulation-mode LDMOS with a convex-shaped field plate structure is proposed and fabricated.The structure features a field plate with convex shape at both source and drain sides above the drift.The field plate consists of two back-to-back diodes.Regions which make no contribution to BV or accumulation effect are removed from N-drift region,which utilizes the N-drift effectively.Ensuring a lower R_ON,SP and high BV with a shortened N-drift length,the device achieves continuous accumulation layer in the whole drift surface.Hence,the proposed structure achieves improved on-state performance and significantly reduced R_ON,SP.The fabricated novel LDMOS realizes a BV of 489V and R_ON,SP of 22.2m?·cm~2 when L_D=33?m.The R_ON,SP of proposed LDMOS device 48.4%lower than that of LDMOS with regular field plate.2.A novel accumulation-mode LDMOS with two separated integrated diodes is proposed and fabricated.The main feature of new structure is that D1 and D2 on the field plate are separated and located on two sides of the drain N+region.On one hand,the drift length is shortened without sacrificing BV.On the other hand,the leakage current resulted from parasitic PNP transistor is suppressed.Based the novel LDMOS device,an improved structure with convex-shaped source-side field plate is proposed.The improved structure further shortens the drift length and achieves continuous electron accumulation layer,which further decreases R_ON,SP.The fabricated LDMOS with separated integrated diodes realized a BV of 483V and R_ON,SP of 29.3m?·cm~2 and a BV of 518V and R_ON,SP of23.5m?·cm~2 for the improved structure.The R_ON,SP of improved structure is 53.8%lower than that of theoretical Triple RESURF LDMOS under the same BV.