4.5-kV 20-mΩ.cm~2 Implantation-Free 4H-SiC BJT with Trench Structures on the Junction Termination Extension

摘要

A single-mask junction termination extension with trench structures is formed to realize a 4.5 kV implantation-free 4H-SiC bipolar junction transistor (BJT). The trench structures are formed on the base layer with dry etching using a single mask. The electric field distribution along the structure is controlled by the number and dimensions of the trenches. The electric field is distributed by the trench structures and thus the electric field crowding at the base and mesa edges is diminished. The design is optimized in terms of the depth, width, spacing, and number of the trenches to achieve a breakdown voltage (V_b) of 4.5 kV, which is 85% of the theoretical value. Higher efficiency is obtainable with finer lithographic resolution leading to smaller pitch, and higher number and narrower trenches. The specific on-resistance (R_(on)) of 20 mΩ.cm~2 is measured for the small-area BJT with active area of 0.04 mm2. The BV-R_(on) of the fabricated device is very close to the SiC limit and by far exceeds the best SiC MOSFETs.