Effect of Mesa Sidewall Angle on 4H-Silicon Carbide Trench Filling Epitaxy Using Trichlorosilane and Hydrogen Chloride

In this report, the advanced manufacturing advantages of using supersaturated chlorinated chemistry are demonstrated at 1550 °C in 4H-silicon carbide (4H-SiC) epitaxy on trenches with different geometric profiles. Sloped mesa sidewalls (8°) show improved filling behavior compared with vertical sidewalls (2°) and lower the optimum chlorine/silicon ratio (Si:Cl) required to complete filling. Both the optimum Cl:Si ratio (10) and sidewall angle are lower for wider trench openings, allowing complete fill of 3 µm wide trenches (8 µm pitch, 5 µm depth) at a filling rate of 19 µm h⁻¹. Excessive hydrogen chloride (HCl) diminishes filling by reducing sidewall growth and can also produce an end surface with very rough topography. This work demonstrates the importance of trench geometry on both the filling behavior and process optimization in chlorinated trench filling epitaxy for the manufacture of 4H-SiC superjunction power electronics.