Investigation of carrot reduction effect on 4H-silicon carbide epitaxial wafers with optimized buffer layer

We investigated the carrot-defect reduction effect by optimizing the buffer layers of 4H-Silion Carbide(SiC) epitaxial wafers. The SiC epitaxial wafer with the 0.5 μm-thick optimized buffer layer show the carrot-defect density of 0.13 cm
^-2
, since that with the conventional buffer layer were 0.68 cm
^-2
. Although the average bunching length with the optimized buffer layer was 7-times longer than those with the conventional buffer layer, we could reduce the bunching length by applying the optimized condition only to the initial 0.05 μm-thick buffer layer. Finally, with the initial 0.05 μm-thick optimized buffer layers, we could achieve the SiC epitaxial wafers with only half the carrot-defect densities of those with the conventional buffer layers, while the average bunching lengths were less than 100 μm. With this condition, we could achieve the estimated yield of 90.1% with 4 x 4 mm chips, while that with the conventional buffer layer was 81.9%.