Study Of A Deep Trench Super-junction SiC VDMOS

Silicon Carbide Vertical Double-Diffusion Metal-Oxide-Semiconductor Field-Effect Transistor?SiC VDMOSFET,known as SiC VDMOS?is one of the most potential power component for the new generation,made of the new semiconductor material,silicon carbide.It has extremely promising prospects in high pressure,temperature and frequency fields application with its high breakdown voltage,wide band gap and high temperature resistance and high electron mobility characteristics.Therefore,as one of the most advanced power devices,SiC VDMOS needs to be studied and is very significant.For the study of power devices,the general concern is the relationship between the breakdown voltage BV and the on-resistance R_ON,which usually requires a higher BV and a lower R_ON.For silicon devicese,there exists a"silicon limit":R_ON?BV^2.43.It is the same for silicon carbide that has a similar restriction,but the multiple relationship is more moderate.In addition,except the conventional problem solving,this paper pays special attention to the the high electric field at the gate oxide layer for SiC VDMOS.At the corner of the trench gate,due to the Gaussian relationship at interface of the gate oxide layer and the semiconductor and the curvature effect at the corner of gate,an extremely high electric field will appear,which exceeds the critical breakdown electric field of the gate oxide layer and breaks down before the whole device is broken down.It reduces the operational reliability of the device.In response to this problem,a deep trench structure is proposed to improve the gate oxide layer under the gate to the substrate of the drain.Then,On the basis of the above,this paper proposes to add a super-junction structure in SiC VDMOS,to improve the breakdown voltage of the device through the super-junction.It adjusts the vertical electric field in drift region and release the limit on the doping concentration of the drift region,which greatly reduced the on-resistance.In summary,a deep trench super-junction SiC VDMOS?DT-SJ SiC VDMOS?is proposed in this paper.In the research of DT-SJ SiC VDMOS,the parameter performance of the device was optimized by using two-dimensional simulation software,and it is compared with the conventional super-junction SiC VDMOS?C-SJ SiC VDMOS?and C SiC VDMOS devices.The electrical characteristics of withstand voltage characteristics,the conduction characteristics,the maximum gate oxygen field,the gate charge and the switching characteristics are all horizontally compared.The new device structure achieves superior performance.The DT-SJ SiC VDMOS device proposed in this paper achieves a breakdown voltage of 2885 V,an on-resistance of 1.625 MW·cm^-2,a Figure of Merit?FOM?of 5122 MW·cm^-2,a maximum gate oxygen field(E_ox,max)of 4.79 MV/cm and a gate charge(Q_GD)of 8.75 nC.After the design,the critical longitudinal electric field of the longitudinal device is analyzed.The boundary condition is used to solve the Possion equation.The analytical model of the electric field distribution of the device is obtained.And The accuracy of the model is verified under different parameters such as the drift region length,doping concentration and the drain bias voltage.Then,based on the electric field model,the breakdown voltage model is derived.Through the simulation fitting,the relevant parameters of the breakdown voltage model are corrected and optimized,then an analytical model with less error is obtained.Finally,the DT-SJ SiC VDMOS designed and proposed in this paper realizes the overall improvement of electrical properties of all aspects of the power device.Meanwhile,it also establishes a more accurate electric field model.The research in this paper provides a feasible improvement scheme for power device design.