Structural Improvement of Seeds for Bulk Crystal Growth by Using Hot-Wall CVD of 4H-SiC
Growth of 4H-SiC epitaxial layers has been performed in a horizontal hot-wall CVD (chemical vapor deposition) reactor using the silane-propane-hydrogen system. Two inch 4H-SiC, C-face wafers with an off-cut angle of about 7° towards <11 2 0> direction have been used as substrates. Micropipe dissociation has been investigated by varying the carbon-silicon (C/Si) ratio in the source gas atmosphere. Depending on the C/Si ratio the micropipes propagate into the layer without changing their image (C/Si > 1) or they dissociate in separate dislocations leaving a scar like formed surface region (C/Si £ 1). The substrates including epitaxial layers of reduced micropipe density were used as seeds for bulk crystal growth. If a micropipe is once closed in an epilayer grown at a low C/Si ratio, it is not opened in the subsequent growth process at high temperature.
Roberta Nipoti, Antonella Poggi and Andrea Scorzoni
G. Wagner et al., "Structural Improvement of Seeds for Bulk Crystal Growth by Using Hot-Wall CVD of 4H-SiC ", Materials Science Forum, Vols. 483-485, pp. 109-112, 2005