Trench Termination With SiO₂-Encapsulated Dielectric for Near-Ideal Breakdown Voltage in 4H-SiC Devices

Trench termination with SiO2-encapsulated dielectric for 4H-SiC devices is proposed and experimentally demonstrated. The trench is mainly refilled with spin-on dielectric which is encapsulated with SiO2 to protect it from the high electric field in the trench. Such a trench termination is fabricated along with a high-voltage p-i-n diode. The fabricated device shows a repeatable breakdown voltage over 1750 V (96% of the ideal planar junction breakdown) with a termination length of 14 μm while the conventional trench termination has unrepeatable breakdown and requires over 30 μm termination length. Also, this termination length is less than ~1/4 of the dimension of a field limiting rings termination. Moreover, the fabrication process is robust with a large process window (Trench width ≥ 14 μm).