Study Of Novel Junction Termination Technology Of High-voltage4H-SiC JBS Diode

With the continuous change of application environment and the continuousincreasing demand of high quality application, the performance of conventionalSi-based devices is difficult to have a huge improvement since it has nearly reached it’stheoretical limitation. Therefore, the study and application of next generationsemiconductor material is critical for the development of semiconductor industry. Withthe wide band gap, high critical breakdown electric field, high electron saturationvelocity and high thermal conductivity, Silicon Carbide (SiC) is very suitable to beapplied in the power electronics. Power diode is one of the most important devices inpower electronics, and JBS(junction barrier controlled Schottkey) is the mainstreamstructure in SiC diode due to it’s perfect performance, so the development of SiC JBS isthe foundation of the industrialization of SiC power devices.The junction termination techniques (JTT) are always necessary to improve thereverse characteristics of power semiconductor devices because of the curvature effect.There are some differences in material and process characteristics between SiC and Si.Therefore, some JTT developed from Si-based devices are difficult to be applied in SiCdevices. So it is crucial to study the junction termination technique for SiC powerdevices. The basic characteristics and JTT of SiC JBS were studied based on thenumerical simulation tool, Atlas, from Silvaco. The working mechanism of Field Plant(FP), Field Limiting Ring (FLR) and single-zone Junction termination Extension (JTE)were analysed theoretically. Based on the simulation tool, the relationship between thedevice performance and the structure parameters within each device was studiednumerically and then explained theoretically. The special multiple-zone JTE form inSiC, etched JTE, was also studied numerically and theoretically.A novel structure called VLE-JTE(variation of lateral etching JTE) is proposedbased on the idea of charge modulation in JTE through etching and the experimentalexperience of industrial fabrication. This structure breaks the limitation of theconventional etched JTE that each etching process can only form one JTE zone. Thestructure modulates the charge distribution in JTE through altering the size of etching windows, which results in multiple-zone JTE through only one etching process. Thetheoretical analysis shows that this structure can form any charge distributionexpediently. As a result, the difficulty in forming multiple-zone JTE within SiC powerdevices is solved. The simulation results show that the breakdown voltage of VLE-JTEcan reach up to6500V, increased by900V compared with the conventional etched JTE.Moreover, the process tolerance characteristics of VLE-JTE is better than that ofconventional etched JTE, which can provide a useful reference to solve thelong-standing problem in JTE that the device performance is sensitive to it’s dose.Finally, the optimizing method of the VLE-JTE is proposed in detail through the deepstudy of its principles, offering its practical applying conditions.