On the Roughness Analysis of High-Index Silicon Wafers Using KOH-IPA Solutions

Abstract

Bulk Micromachining on some stable high-index silicon substrates are ever more interesting because they are opening new possibilities for the development of novel 3D microstructures and surface nanostructures useful for diverse quantum applications. Considering crystallography-oriented etching, several mechanisms are poorly understood and hence, some experimental work leading to 3D device fabrication are being developed and reported without analyzing the morphology evolution. For bulk micromachining, when 3D etching is developed using some anisotropic solution, the structure evolution takes place under a competition of fast-etching planes and unstable facets against slow-etching planes. According to the etchant composition, the resulting surface roughness can be considered as one of the main issues to be addressed. Wet chemical etching on (1 1 4), (1 1 3), and (5 5 12) silicon substrates at 60 °C, using aqueous KOH and KOH+IPA solutions, is carried on this work. The absolute etching rate trends and surface roughness are compared to reported data obtained from (0 0 1) silicon substrates. The overall etching mechanism is analyzed following some crystallographic rules and compared with high-index surfaces obtained from (0 0 1) silicon substrates. According to the best etching conditions achieved on this study, some novel 3D microstructures are presented.