MoS₂-assisted chemical etching of silicon in an HF/H₂O vapor

Assisted chemical etching using non-noble metal catalysts is attracting new attention for the fabrication of semiconductor micro/nanostructures. Here, we perform silicon etching in a vapor phase using molybdenum disulfide (MoS2) flakes exfoliated from a natural bulk crystal. The edge plane of MoS2 works as a catalytic active site, while its basal plane is inert. This unique feature distinguishes MoS2 from other catalysts used in assisted chemical etching. Therefore, MoS2 can be a promising candidate for elucidating the mechanism behind assisted chemical etching using non-noble metal catalysts. When the MoS2-loaded silicon substrate is exposed to an HF/H2O vapor, the whole silicon substrate under the MoS2 flakes is selectively etched, forming etched hollows despite the presence of the catalytic active sites located only at the edge. This vapor-phase etching using MoS2 flakes is expected to stimulate new fundamental research on chemical etching assisted by other non-noble metal materials.