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An empirical growth window concerning the input ratio of HCl/SiH4 gases in filling 4H-SiC trench by CVD

Two kinds of defective growth in 4H-SiC trench filling were found to be associated with the compositional ratio of supplied gases. An input HCl/SiH4 ratio below 35 leads to overgrowth around the mesa, forming voids. Overetching on the mesa induces an etched mesa when HCl is supplied in excess, e.g., HCl/SiH4 > 65 (SiH4 = 30 sccm). Thus, an empirical window for nondefective growth is discerned. It also contains a high-filling-rate area around HCl/SiH4 ∼50, which proves well-proportioned etching and deposition reactions, and 25-µm-deep trenches (aspect ratio of ∼11) are successfully filled at a rate as high as 4.3 µm/h.