A Study of Epitaxial Growth on 4H-SiC Substrates Treated by Plasma Polish Dry Etch (PPDE) Process

We studied the impact of plasma polish dry etch (PPDE) on SiC substrates and its effect on epilayers grown on PPDE treated substrates. PPDE treatment on chemo mechanical polished (CMP) surface shows no significant degradation in surface roughness even with 3µm removal. On the other hand, when a mechanical polished (MP) surface was treated by PPDE, surface roughness was improved, demonstrating that PPDE can smooth a rough surface post MP process. Selective etching of threading screw dislocations (TSD) was evident from pit formation on the substrate surface. These pits may generate extended structural defects (e.g. triangular defects) during the epilayer growth depending on the sizes of the pits. No evidence was found that PPDE selectively etched BPD in the substrate and, hence, no improvement in BPD conversion was seen after epilayer growth. Ideally, PPDE treated surface pits needed to be minimized at TSD sites and mild etching at BPD sites is preferable and subject to future optimization.