Electrochemical Investigation of the Effect of Hydrogen Peroxide Concentration on Platinum-Particle-Assisted Etching of p-Type Silicon in a Hydrofluoric Acid Solution

Abstract

Metal-assisted etching (metal-assisted chemical etching) has attracted increasing attention as a low-cost and versatile microfabrication technique of semiconductors. In platinum (Pt)-particle-assisted etching of silicon (Si), a composite structure of straight macropores and a mesoporous layer can be produced, but the mechanism of the structure formation is still open to discussion. We employed an electrochemical approach to investigate the composite structure formation by the Pt-assisted etching. Polarization curves of Pt-deposited Si and bare Si were measured in hydrofluoric acid (HF) solutions containing different concentrations of hydrogen peroxide (H2O2). The open circuit potential during the Pt-assisted etching was more positive than that of the bare Si and it shifted in the positive direction with increasing the H2O2 concentration as a consequence of the enhancement of the H2O2 reduction reaction. For the structure observation, both the macropore depth and the mesoporous layer thickness increased with increasing the H2O2 concentration, while the ratio between them changed. We discussed the structure change on the basis of the polarization characteristics. The mesoporous layer formation can be explained by the hole consumption at the Si surface under the positive potential which is determined by mixed potential theory.