Design And Study Of FS-IGBT Device

Rising in the 1960s and 1970s,power electronic technology is an electronic technology which uses power electronic devices(also known as power semiconductor devices)to transform and control electric energy.It has the advantages of high efficiency and energy saving.With the development of science and technology,power semiconductor devices have been continuously improved and developed.Now,they are widely used in rail transit,urban power grid,automotive electronics,industrial motors and many other fields.Nowadays,more and more people have been advocating energy conservation and emission reduction.The requirements for power devices in various application fields have become higher and higher,therefore,it has a bright development prospect.Insulated gate bipolar transistor(IGBT)combines the characteristics of thyristors and power MOS devices.As one of the fastest developing new power semiconductor devices,IGBT combines the advantages of low loss,high withstand voltage and high current.This paper took the medium voltage(1200V)field stop(FS)IGBT as the study object.By reading the literature,the development history of IGBT devices has been learned.Some optimization technologies,which proposed by predecessors,have been learned to improve the performance of devices,such as"Injection Enhancement"and"carrier storage".Based on the physical principle of semiconductor devices,this paper optimized the conduction voltage drop and breakdown voltage of FS-IGBT through simulation.It puts forward a composite cell structure of"narrow mesa structure,charge carrier storage layer(CS-layer)and floating p-base cell".The main work of this subject is as follows:1?The two-dimensional FS-IGBT device structure was built by using the Medici simulation software,and the electrical characteristics of the on state and the blocking state were simulated.By studying the effects of CS-layer and mesa width on the on-voltage drop and breakdown voltage,it can be concluded that the narrow mesa(0.5?m)structure can reduce the on-voltage drop of the cell from 1.3V to 1.1V(about 15%),which is compared with the wide mesa(2.5?m)structure.In terms of withstand voltage capability,the narrow mesa structure can increase the breakdown voltage from 1235V to 1323V(about 7%).On this basis,the introduction of a shallow CS-layer with a higher concentration(N_CS=1e17cm^-3)can further reduce the on-voltage drop to 1.02V,while the breakdown voltage only drops by 2V(about 0.15%),which has little impact on the withstand voltage performance.It is comprehensively concluded that the composite structure of narrow mesa cells and shallow CS layer with higher concentration has better conduction loss and withstand voltage capability.The on-state voltage drop is reduced by about 22%,and the withstand voltage capability is increased by about 7%.2?On the basis of the compound cell with narrow mesa,a combined structure with the floating cell in parallel is proposed,and the model is built by the Medici to simulate the conduction state.The simulation results show that when the proportion of floating cells in the combined structure is 1:4(floating cells:compound cells=1:3),the conduction voltage drop is the smallest(reduced by about 5%).Besides,different working currents can be achieved by adjusting the ratio of the combined structure to adapt to various working scenarios.3?According to the FS-IGBT manufacturing process and simulation results,the mask layout of 1200V FS-IGBT is drawn.The overall layout is a 2500?m×2500?m square with rounded corners,of which the 2000?m×2000?m square area is the active area of the device.The active area mainly includes the strip-shaped cell array(cell array)and the gate pad(Gate Pad)structure.Areas that are prone to breakdown such as zone edges and corners are innovatively designed.The area of the terminal is about 2.25×10~6?m~2,accounting for 36%of the total area.The terminal adopts a floating field ring structure,which uses multiple field limiting rings with unequal distances to enhance the overall voltage resistance of the product.