Pit Formation, Patterning and Flattening of Ge Surfaces in O₂-Containing Water by Metal-Assisted Chemical Etching

Abstract

Metal-assisted chemical etching is a novel method of etching a Ge surface in contact with a noble metal in water. Its basic mechanism involves the catalytic activity of metals to reduce dissolved O2 molecules in water, which accompanies the formation of a soluble oxide (GeO2) on the Ge surface around the metal. Here, we apply this electroless etching to the pit formation, nanoscale patterning and surface flattening of Ge. The fundamental etching properties for these three processes are also presented.

Formation of Etch Pits on Germanium Surfaces Loaded with Reduced Graphene Oxide in Water

“…2 and 3 demonstrate that a Ge surface in contact with reduced GO is selectively etched in water. This indicates the possibility that a film composed of reduced GO sheets can serve as a catalyst to flatten a Ge surface in water, as we previously demonstrated with a Pt thin film (6,7).…”

“…We have applied this etching mode to the machining of a Ge surface in O 2containing water. So far, we revealed fundamental etching properties such as pore formation and patterning in this system with noble metals (Pt and Ag) (12,13), and recently, we demonstrated Pt-assisted chemical flattening (6,7). In this scheme, a catalyst plate comprising a soft elastomer coated with a sputtered Pt film, and a Ge wafer were brought into contact and rotated independently in the same plane in water.…”

“…However, CMP utilizing an alkaline solution may not be an ideal method of flattening a Ge surface. From this viewpoint, there have been several previous studies on improving the surface microroughness of Ge (4)(5)(6)(7), some of which used thermal treatments.…”

“…Previous reports on metal-assisted chemical etching of Ge surfaces in O 2containing water and its applications from our group. See references (6,7,12,13) for details.…”

Metal-assisted chemical etching beyond Si: applications to III–V compounds and wide-bandgap semiconductors

“…Kawase et al 200,202 developed a surface flattening process for Ge wafers by utilizing a Pt-coated elastomer pad. Following treatment with the elastomer pad, surface micro-roughness was improved to an average roughness 50% of the pre-treatment value.…”