>Experiment on alleviating the bending of CVD-grown heavily Al-doped 4H-SiC epiwafer by codoping of N
In order to alleviate the convex wafer bow that commonly occurs on a heavily Al-doped 4H-SiC epilayer grown on an n+ substrate, nitrogen gas was intentionally introduced, together with an Al dopant gas during CVD growth, that is Al–N codoping. It was found that, by introducing N2 at various flow rates, the concentration of incorporated N impurity increases along with the supplied flow rate, while the Al impurity remains at a similar concentration. With the codoping of N and Al in 4H-SiC, a marked reduction of wafer bow has been achieved. The crystal structural measurement suggests that the introduction of N impurity alleviates the large wafer bow owing to the reduced lattice constant differences between the p+ epilayer and the n+ substrate.
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