Device Simulation And Experimental Study Of 1200V SiC BJT

Silicon Carbide?SiC?material,as a typical representative of the third generation of semiconductors,is the base material for future high-voltage,low-loss power electronic applications due to its superior physical and electrical properties.Bipolar Junction Transistors?BJTs?have become promising power devices due to its lower switching losses and faster switching speeds.However,the low forward current gain???and reverse breakdown voltage(BV_CEO)limit the commercial application of Si C BJTs.Researching the mechanism of forward current gain and breakdown voltage degradation,developing and optimizing the key process experiments that affect the device characteristics,and presenting a novel structure of SiC BJT from the perspective of device design are of great significance.First of all,based on the Silvaco TCAD simulation design platform of the power integration laboratory of the University of Electronic Science and Technology of China,the external base interface recombination effect of the high-voltage 4H-Si C power BJT is studied from the simulation point of view.By studying the influence mechanism of the interface states of the external base region on the forward current gain of the device,combined with the current SiC BJT passivation technology,two novel high-current gain passivation structures are proposed from the perspective of device design:heterojunction passivation structure and P+epitaxial passivation structure.The new structures can suppress the surface recombination effect in the external base region,and modulate the electron concentration on the outer base region surface,thus reduce the recombination rate of the carrier surface and increase the current gain of the device.Secondly,the influence mechanism of passivation technology on the breakdown characteristics of high voltage 4H-SiC BJT is studied by two-dimensional simulator Silvaco.From the two perspectives of the passivation layer's fixed charges and passivation-layer/SiC interface traps,the failure mechanism of high-voltage Si C device junctions is further studied.Two types of junction termination structures with high efficiency are proposed:the implantation-etched JTE structure and the field-plate assisted JTE structure.The new structures have the advantages of simple process and large process selection window,effectively reducing the sensitivity of the termination structure to the doping dose and the interface charge of the passivation layer,thus improve the termination efficiency.Finally,based on the joint technological platform established by the Institute of Microelectronics of Chinese Academy of Sciences and CRRC Times Electric,the key process conditions such as 4H-Si C ICP etching,P+ion implantation,ohmic contact,surface passivation and Pad metal were developed and optimized.The static electrical parameters of the novel emitter metal extension structure and conventional devices were tested.The results showed that the breakdown voltage of the novel emitter metal extension structure exceeded 1500V and the maximum DC current gain(?_max)reached43@J_C=716 A/cm²,which is a 43%increase compared to the conventional structure.The specific on-resistance(R_SPON)is 5.4 m?·cm².With the device simulation,the physical mechanism of the forward current gain improvement of the new structure is also analyzed.