A general strategy for polishing SiC wafers to atomic smoothness with arbitrary facets. (15th June 2022) - Ji, Peixuan
Abstract: SiC is essential for epitaxial growth of graphene and promises to be an ideal material for next generation high-power electronics. The electronic properties of graphene are highly dependent on the facet on which it is grown. Therefore, the selection of facet provides an extra tuning parameter to obtain its desired characteristics. As one of the key factors of growing pristine graphene on SiC wafers, their roughness requires to be atomically smooth. In this work, we present a data-driven study of the grinding, mechanical polishing and chemical mechanical polishing (CMP) procedures applied to a SiC wafer with arbitrary facets. The phenomena and principles in the polishing steps are discussed. As specific facets of SiC have unique atomic arrangements, different recipes are required for the C and Si faces and their performances are investigated. The interesting, but rarely studied (1 1 ‾ 05) facet is taken as an example of a non-polar case to apply the procedures. It is found that the material removal rate (MRR) in mechanical polishing is directly related to the facet hardness. Hence, the MRR of the (1 1 ‾ 05) facet is the slowest in that process, however, during CMP its MRR is 18 times faster than the Si-face, hints the different chemical and physical polishing mechanism. Accordingly, polishing recipes are proposed that can be adjusted to create atomically smooth wafers of arbitrary facets of SiC.