Shape Control and Roughness Reduction of SiC Trenches by High-Temperature Annealing

The high-temperature annealing of SiC trenches has been investigated for improving the shape of trenches and the smoothness of trench sidewalls In a SiH4-added Ar (SiH4/Ar) atmosphere, the transformation of SIC trenches required a pressure of 80 Torr and a temperature of 1700 degrees C: The inner surface of the trenches became smoother without significant etching, while the sample surface became rougher From the time dependence of the curvature at the trench upper corner, the authors consider that both surface diffusion and evaporation-condensation contribute to the transformation, as opposed to the annealing in H-2 reported by another group where transformation is driven mainly by evaporation-condensation. The present authors did not observe a significant change in trench shape in a H-2 atmosphere at annealing temperatures up to 1400 degrees C, except for a smoothening of sample surfaces. The proposed two-step annealing process, consisting of annealing at 1700 degrees C in SiH4/Ar followed by annealing at 1400 degrees C in H-2, realized rounded trench corners and smooth surfaces simultaneously without significant etching. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/JJAP.48.116508