Design And Key Technologies Of LDMOS Optimizing Lateral And Vertical Electric Field

As the core components of Smart Power Integrated Circuits(SPIC)and High Voltage Integrated Circuits(HVIC),power semiconductor devices are widely used in the fields of new energy vehicles,intelligent home appliances,and military products because of their ability of frequency conversion,rectification,voltage transformation,power amplification and power management.The key problem of power semiconductor devices is to improve the trade-off relationship between breakdown voltage(BV)and specific on resistance(R_on,sp).Power semiconductor researchers improve the performance of power semiconductor devices from the perspective of new structures,new theories and new materials.A variety of technologies have been proposed to improve the performance of power semiconductor devices,mainly divided into two categories:surface terminal technology and body terminal technology.However,these technologies mainly modulate the lateral or vertical electric field of power semiconductor devices separately,which increases the complexity of design and process,and affects the further improvement of its performance.This thesis focuses on the electric field modulation technology,aiming at optimizing lateral and vertical electric fields and improving the performance of power semiconductor devices by the same type of technology.Two kinds of the new Lateral Double Diffusion Metal-Oxide-Semiconductor Field-Effect Transistor(LDMOS)are proposed based on the electric field modulation technology.One is Substrate Charge Compensation Layer(SCCL)LDMOS and SCCL Super Junction LDMOS(SJ LDMOS)with the substrate charge compensation technology;the other is Multi Ring(M-R)LDMOS and M-R SJ LDMOS devices with multi ring technology.The analytical models of SCCL LDMOS and M-R LDMOS are established to explain the electric field modulation mechanism of the substrate charge compensation technology and multi ring technology.In addition,the LDMOS with assisted substrate depletion layer(ADSL)technology are further optimized and its analytical model is established,and the modulation effect of ADSL on electric field is discussed.The analytical model of the step High Dielectric Material(Hk)MOSFET is also established,and the modulation mechanism of two-dimensional electric field similar to LDMOS is described.At last,the necessity of optimizing the lateral and vertical electric field distributions simultaneously for LDMOS applied to flexible electrons is discussed.The electrical properties of LDMOS for flexible electrons are analyzed by simulation and experiment.The main innovations are as follows:(1)The research of ADSL LDMOS is completed,and aiming at the problem that the ADSL LDMOS has a nonuniform surface electric field,a P-Buried layer ADSL LDMOS(P-B ADSL LDMOS)is proposed.The new LDMOS with ADSL to modulate the vertical electric field and with P Buried layer to improve the surface electric field.According to the principle of charge conservation,the doping concentration in drift region of P-B ADSL LDMOS is increased and the R_on,sp is optimized.Therefore,the performance of P-B ADSL LDMOS is improved due to the simultaneous effect of P-B layer and ADSL.P-B ADSL LDMOS has a better performance,and the performance of P-B ADSL LDMOS is so superior that the silicon limit has been broken.In addition,the analytical model of ADSL LDMOS is established to explain the effect of electric field modulation of ADSL on the lateral and vertical electric field distributions of LDMOS.(2)The SCCL LDMOS is proposed.The SCCL can optimize the lateral and vertical electric field distributions of LDMOS at the same time.By the modulation effect of the SCCL,the vertical electric field of the SCCL LDMOS is expanded and new electric field peaks produce on the lateral and vertical electric field distributions,which makes the lateral and vertical electric fields more uniform and improves the BV.The BV saturation effect of LDMOS has been broken due to the effect of the SCCL.Then,the SCCL technology is applied to SJ LDMOS,because of the electric field modulation of the SCCL,not only the lateral and vertical electric fields are optimized at the same time,but also the substrate assisted depletion effect of the conventional SJ LDMOS is eliminated,which makes the BV of SCCL LDMOS improve.The performance of SCCL SJ LDMOS is excellent that the silicon limit of LDMOS has been broken.In addition,the analytical model of SCCL LDMOS is established to explain the modulation effect of SCCL on the lateral and vertical electric field distributions of LDMOS.(3)The M-R LDMOS is proposed.The multi-ring technology has a great modulation effect on the lateral and vertical electric fields of LDMOS at the same time.Due to the modulation effect of multi ring technology,the vertical electric field of M-R LDMOS is expanded,the lateral and vertical electric fields become more uniform and the BV is improved.In addition,the M-R widens the conductivity path and reduces the R_on,sp.Then,the M-R SJ LDMOS is proposed.The lateral and vertical electric field distributions are optimized and the substrate assisted depletion effect is eliminated because of the effect of the multi ring technology.The BV of M-R SJ LDMOS is improved.The performance of the device is improved by the multi ring technology,and the contradiction between BV and R_on,spbreaks through the silicon limit.In addition,the analytical model of M-R LDMOS is established to explain electric field modulation effect of multi ring technology on the lateral,vertical and radial electric fields of M-R LDMOS.(4)The drift region of Step Hk MOSFET is similar to that of LDMOS,which is depleted by P-type well and Hk layer at the same time.Its electric field distribution is modulated by electric field in two directions.Combined with the characteristics of step HK MOSFET,the analytical model of Step Hk MOSFET is established.By solving the Poisson equation in drift region of semiconductor material and the Laplace equation in Hk layer,the two-dimensional electric field distribution model of the device is obtained,and the electric field modulation effect of two-dimensional electric field distribution on the device is described.Secondly,the BV model is established to accurately predict the breakdown characteristics of the device.Finally,the R_on,sp of the new device is solved.(5)The necessity of optimizing the lateral and vertical electric field distributions simultaneously for LDMOS applied to flexible electrons is discussed.The lateral and vertical electric field distributions,breakdown characteristic,output characteristic and transfer characteristic of Bulk Silicon and SOI LDMOS for flexible electrons without substrate electrode and substrate thinning are analyzed.And the method of optimizing the lateral and vertical electric field to improve the performance of LDMOS for flexible electron is proposed.The electrical properties of SOI LDMOS for flexible electron is analyzed by experiment.In this thesis,five new LDMOS are proposed,including P-B ADSL LDMOS,SCCL LDMOS,SCCL SJ-LDMOS,M-R LDMOS and M-R SJ-LDMOS.Compared with conventional LDMOS,the trade-off relationship of BV and R_on,sp of these devices is effectively improved.The analytical models of ASDL technology,SCCL technology,M-R technology and Step Hk layer technology have been established respectively to explain the electric field modulation effect of each technology.The performance of LDMOS applied to flexible electrons has been studied and the performance of LDMOS without substrate electrode is analyzed by the experiment.