Performance analysis of 4H-SiC super-junction devices: impact of trench angle and improvement with multi-epi structure

This paper studies the impact of the trench angle on SiC super-junction device performance through the numerical simulation. Devices with different structure parameter sets (mesa width, epi doping) targeting different voltage ratings have been considered. It is found that with the optimum epi doping, the highest Baliga's figure of merit (BFOM) is always achieved at the trench angle of 90 degrees. The advantage of 90 degrees trench angle can be further increased by reducing the mesa width (MW). However, the 90 degrees trench is hard to be achieved through the current fabrication technology. Once the trench angle is reduced slightly, the device BFOM will decrease evidently especially for high voltage devices. At this condition, the reduction of mesa width does not necessarily produce higher BFOM. For example, at the trench angle of 89 degrees and trench depth of 25 mu m, the BFOM of the device with MW = 3 mu m is substantially higher than that of the device with MW = 1 mu m. Such a phenomenon is contrary to conventional theory, which is crucial for device design. Finally, in order to improve the performance of devices with non-90 degrees trenches, the multi-epi structure is proposed. With such a novel structure, significant improvements have been observed in the simulation. The BFOM increments for 2 kV, 3.5 kV and 5 kV voltage rating devices are 27.4%, 60.8% and 102.6% respectively, demonstrating the superiority of the proposed multi-epi structure for SiC super-junction devices.

Automated summary

This paper investigates the impact of trench angle on SiC super-junction device performance, finding that the highest figure of merit is achieved at a 90-degree trench angle with optimal epi doping. However, achieving a 90-degree trench angle is challenging with current fabrication technology. The proposed multi-epi structure demonstrates significant performance improvements for devices with non-90-degree trenches, showing superiority in BFOM compared to conventional designs.