Optimal Design Of Mesa With Charge-modulated JTE Structure

4H-SiC material is suitable for fabricating high voltage thyristors due to the advantages of wide bandgap,high critical breakdown electric field,high thermal conductivity,etc.Since the material defects will limit the chip size,the SiC thyristor can only form a square die structure rather than the wafer structure,It is difficult to directly adopt the Si thyristor bevel termination in the SiC thyristor.The field limit ring need a large termination area and the etching JTE requires high etching precision,so the curved mesa with ion implantation type JTE is often used to achieve termination protection in the SiC high voltage device.But the conventional ion implantation JTE structures breakdown voltage is sensitive to the JTE dose and do not consider the influence of the curvature of the m esa on the breakdown voltage of the device.For the two purposes,the commercial simulation software is used to study and improve the mesa combined charge-modulated JTE termination on high-voltage 4H-SiC thyristors that the ideal breakdown voltage is 10190V,so the JTE dose range for getting high breakdown voltage can be improved in this paper,and study the influence of the curvature of the mesa on the breakdown characteristics of the device.The main research contents and results are as follows:1.Research and optimize the curved mesa combined JTE terminaion.The simulation results show that the breakdown voltage of the single-zone JTE termination structure is sensitive to the JTE dose.By increasing the number of JTE regions can reduce the breakdown voltage sensitivity to JTE dose effectively.For optimized curved mesa combined three-zone JTE terminaions,the JTE dose window width that the breakdown voltage above 9500V(about 93.2%of ideal breakdown voltage)can reach 11.2×1012cm-2.2.Analysis and optimize the curved mesa combined charge-modulated JTE termination.Because the JTE dose window of the above mentioned curved mesa combined three-zone JTE termination is still not wide enough,the method of adding the modulation rings in the JTE3 region and converting the JTE3 terminal portion region into the modulation rings is used to alleviate the electric field concentration phenomenon,Compared with the curved mesa combined three-zone JTE termination,the improved termination structures'JTE dose window width that the breakdown voltage above 9500V can change from 11.2×1012cm-2 to 19.2× 1012cm-2,an increase of 71.4%.3.The effect of SiC/SiO2 interface charge and y-irradiation on the termination voltage characteristics was studied.The simulation results show that the SiC/SiO2 negative interface charge has a great influence on the breakdown voltage and the interface positive charge has little effect on the breakdown voltage of the device.For the improved curved mesa combined charge-modulated JTE,the breakdown voltage is degraded from 9669V to 8702V when the interface negative charge density is 8×1012cm-2.Gamma irradiation has a great influence on the single-zone JTE termination,the breakdown voltage of single-zone JTE rises from 9069V to 9563V,which is 5.4%higher,when the irradiation dose is 600krad.But the irradiation has little influence on the improved termination,the breakdown voltage change from 9669V to 9595V when the irradiation dose is 600krad,only reduced by 0.7%.