Study On Charge-modulated Junction Termination Extension Of 4H-SiC Thyristor

4H-SiC thyristor has great attraction for high power switching application, especially in HVDC (High Voltage Direct Current Transmission) due to its superior advantages, such as high voltage, low on-state voltage drop and low power consumption. One of the greatest challenges to realize ultrahigh voltage thyristor is designing effective junction termination structure. In this paper, a triple-zone charge modulation junction termination extension (CM-JTE) structure,which can be formed utilizing two-step implantation without increasing the complexity of process, is presented for ultrahigh-voltage thyristor in 4H-SiC. The termination structure was designed and optimized using two-dimensional commercial simulator. The simulation results showed that the proposed termination structure obtains not only a high and stable breakdown voltage, but also a wide tolerance for deviation of dose in the JTE regions, which increases process robustness.First, this paper simulationed three termination structures for the 4H-SiC thyristor, included the mesa termination, the mesa-SZ JTE(single-zone JTE) termination and the mesa-TZ JTE(triple-zone JTE) termination. The optimal relationship between the main parameters and the breakdown voltage of the device is obtained, which established a certain foundation for the new junction termination structure.Second, a new triple-zone CM-JTE (charge modulation JTE) is proposed. and the withstand voltage mechanism of new structure was analysed. To achieve the optimal breakdown characteristics, the modulation ring parameters of new termination, such as the ring spacing and the number of rings in JTE, are optimized by numerical simulation. The highest breakdown voltage of triple-zone CM-JTE is obtained 26.24kV, and the breakdown voltage is stable in the whole effective dose range. The simulation results showed it had little effect on the breakdown voltage of the device when lithography deviation within 2 ?m. Which illustrated that the feasibility of the two step ion implantation process for the fabrication of charge modulated JTE.Finally, To evaluate the performance of new termination structure, comparing the terminal efficiency, the electric field distribution, the process tolerance and the interface charge of the new termination and other termination structures. The results showed termination efficiency of CM-JTE up to 99% and electric field distribution is uniform. CM-JTE creates a wider optimal JTE dose range of 11.9×101 cm-2 for achieving 90% of ideal breakdown voltage. When theinterface charge density is -2 × 1012 cm-2 , the breakdown voltage only decreased 0.9%.The research results of this study provide a useful reference for the research and development of new junction termination structures, and the improvement of the breakdown voltage and reliability of the devices.