Research On Structure And Characteristics Of The Novel High-Voltage MOS-Controlled Power Devices

Due to the increasing energy demand of modern society and the development direction of energy conservation,power electronics technology,which can improve the efficiency of electric energy transmission and utilization,has become an important supporting technology to improve the living standard of citizens and ensure national security.As the foundation of power electronics technology,power semiconductor devices also have new challenges and development opportunities.The Insulating Gate Bipolar Transistor?IGBT?is one of the most important power semiconductor devices.It combines the advantages of the fast switching speed of the Metal-Oxide-Semiconductor Field Effect Transistor?MOSFET?and the low conduction loss of the Bipolar Junction Transistor?BJT?.As a result,IGBTs are widely used in many applications.In the high voltage application,IGBT with its good switching characteristics is gradually occupying the application range of thyristors,but it also brings new requirements to the electrical performance of IGBT.Focusing on the research hotspot of high-voltage MOS-controlled power devices,under the devoted guidance of Professor Chen Xingbi and Professor Lin Yuan of The University of Electronic Science and Technology of China,the author has carried out a series of researches on optimizing the turn-on characteristics of IGBTs and the trade-off relationship between conduction characteristics and turn-off loss through researching and reading a large number of references.The main innovation work of this dissertation are as follows:1.A novel IGBT with clamped P-well layer is proposed.By the theoretical analysis of the turn-on process of the IGBT with floating P-well layer,it is found that the turn-on characteristics can be dramatically optimized by reducing the potential of the P-well layer.Based on the analysis,a novel IGBT with integrated polysilicon diodes on the surface of the device is proposed.As the P-well layer is connected with the emitter,the potential of the P-well layer is clamped at a low value,which greatly reduces the displacement charging current brought by the high potential in the floating P-well layer during the turn-on process.Then,the controllability of the gate resistance on|d V_CE/dt|and d I_CE/dt of the proposed IGBT is improved,and the trade-off between the electro-magnetic interference noise and the turn-on loss(E_ON)is optimized.Compared with the conventional IGBT,|d V_CE/dt|and d I_CE/dt of the proposed IGBT decrease by 37.5%and 89.1%,respectively,at the same E_ON.Besides,due to the additional hole extraction path during the turn-off process,the turn-off loss(E_OFF)of the proposed IGBT is also reduced by about 57.2%.2.A novel IGBT with the self-biased PMOS and the negative charge in the emitter trench is proposed,which also can be called as a Trench Shielded Planar Gate IGBT?TSPG-IGBT?with the self-biased PMOS.By the theoretical analysis of the effect of carrier stored layer?N-CS layer?on device characteristics,it is found that better V_ON-E_OFFtrade-off can be obtained by increasing the doping concentration of carrier stored layer.Based on this analysis,a novel TSPG-IGBT is proposed,which utilizes the self-biased PMOS and the negative charge in the emitter trench to clamp the intrinsic drain potential of the NMOS in the proposed device.The carrier stored layer?N-CS layer?of the proposed structure will not be completely depleted in the blocking state.Therefore,N-CS layer can be doped at a higher concentration to obtain better V_ON-E_OFF trade-off without damaging the blocking state characteristics.As the potential of the N-CS layer is clamped at a low value,not only the saturation current density is reduced,but also the potential on the trench gate oxide in the blocking state is reduced.Then,the proposed TSPG-IGBT can reduce the thickness of the gate oxide to improve the effectiveness of the emitter trench charge.Moreover,the negative charge in the emitter trench can significantly reduce the saturation current density of the device while hardly increase the on-state voltage.Compared with the conventional TSPG-IGBT with the same breakdown voltage,at the same E_OFF,the on-state voltage(V_ON)of the proposed TSPG-IGBT decreases by0.3 V.Besides,the saturation current density of the proposed TSPG-IGBT also decreases by 24%,which improves the Short Circuit Safe Operating Area?SCSOA?of the proposed device to 1.75 times of that of the conventional TSPG-IGBT.3.A novel Integrated Emitter Turn-Off thyristor?IETO?with single-gate controlling is proposed.The proposed IETO is also a kind of MOS-controlled thyristor.However,Unlike the conventional ETO using external MOSFETs,the IETO integrates the MOSFETs monolithically and can be controlled by a single gate.Then,the controllability of the IETO is improved dramatically to be comparable with that of the IGBTs.By the clamping effect of the integrated control gate,the doping concentration of the carrier stored layer of the proposed IETO can be significantly increased,and a better V_ON-E_OFFtrade-off relationship is obtained.Compared with the Carrier Stored Trench-gate Bipolar Transistor?CSTBT?,at the same E_OFF,V_ON of the proposed device is reduced by about0.12 V and E_OFF decreases by about 51.1%at the same V_ON.Moreover,the saturation current density of the proposed IETO is also reduced by 12.2%4.A Shielded IGBT?SIGBT?with an embedded gate is proposed.The carrier stored layer?N-CS layer?of the proposed SIGBT is entirely shielded by the P-layer layer and its voltage is clamped at a low value more solidly,which solves the problem that the P-layer layer of the Diode-Clamped CSTBT?DC-CSTBT?is unable to clamp the potential of the N-CS layer at high voltage,due to the lateral depletion of the P-layer layer.The potential of the N-CS layer can be solidly clamped at a low value even with high collector voltage,so the doping concentration of the N-CS layer can be significantly increased.Then,a better V_ON-E_OFF trade-off relationship is obtained.The latch-up of the parasitic thyristor is triggered by the embedded gate during the turn-on process.As the parasitic thyristor latches up,the proposed SIGBT turns on.Compared with the conventional CSTBT and the DC-CSTBT,the E_OFF of the SIGBT is reduced by 85.6%and 81.7%at the same V_ON,respectively.Additionally,the saturation current density of the SIGBT is also 31.2%lower than that of the conventional CSTBT.