Control of 4H-SiC mesa profiles by a lower temperature hydrogen annealing process

• 4H-Silicon carbide mesas are controllably faceted by hydrogen etching at 1550 °C, allowing small-scale mesa design. • The rate of hydrogen etching on 4H-silicon carbide depends on the crystal facet exposed by the mesa orientation. • Gas annealing can remove microtrenches, which are harmful for electronic applications. The shape of 4H-silicon carbide mesas after annealing at 1550 °C under high-purity argon, hydrogen and hydrogen chloride gas has been examined. While rounding of mesa corners occurs under argon and hydrogen chloride, etching by molecular hydrogen produces a faceted corner shape, with well-defined angles and facet lengths that can be predictably derived from the etching duration. Hydrogen etches mesa sidewalls anisotropically depending on the mesa orientation relative to the substrate crystal, which is prominent after long annealing times. Microtrenches, which occur at the mesa base during plasma etching, were removed inside narrow trenches by all gases examined. The processes presented herein offer a convenient method for tuneable mesa shaping at the sub-micron level, otherwise unattainable by standard lithographic and plasma etching processes, and which are applicable to electronic device fabrication.