A High Efficiency Composite Junction Termination for SiC Power Devices

Breakdown voltage of termination region for power devices usually determines the really breakdown of a power device. When designing a high-voltage termination, interface charges always play an importance role, especially for Junction Termination Extension (JTE), since it directly affects the total effective charge for the termination. For Silicon Carbide (SiC) devices, another issue is that accurate control of effective acceptor dose in the JTE region is difficult since p-type dopants in SiC is not easy to be fully activated. To enlarge the design window for JTE and investigate the influence of interface charges on breakdown voltage, in this paper, we fabricated a junction termination with combined JTE and floating P+ rings for high efficiency design. The total length of the terminal is ∼55 μm, with 6 Floating P+ Rings (FPRs) in the JTE region. The measured breakdown voltage for the JTE with FPRs is over 1.3 kV, which is improve by about 26%, compared with fabricated pure JTE having a length of 60 μm. However, the measured breakdown voltage is lower than our simulated ones with negative interface charge assumed before experiment, which may be caused by positive charge at the interface of oxide/SiC. After calibration by TCAD tools, the interface charge at the SiO2/SiC interface in the terminal region is estimated to be ∼3.5×10
¹²
cm
^-2
. Based on the calibration, the terminal region was re-designed to sustain a breakdown voltage over 1.5 kV with wide design window for the space between floating P+ rings.