Catalytic Activity of Ru for Metal-Assisted Etching of Si

Abstract

Metal-assisted etching of Si is an electroless method that can produce porous Si by immersing metal-modified Si in a HF solution without electric bias. We reported that the etching rate of noble metal-modified Si in a simple HF solution including oxygen under dark conditions depended on the catalytic activity of metal for oxygen reduction. Only palladium exhibits high activity for the etching under dissolved oxygen-free and dark conditions. In this study, the catalytic activity of Ru for the etching of Si has been investigated. Ru nanoparticles are electrodeposited on Si substrates. Electroless displacement deposition using RuCl3 solution including HF can form Ru nanoparticles not on mirror-polished n-Si substrate but on roughed one. The etching rate of Ru-particle-deposited Si is similar to that of Rh case which is changed with dissolved oxygen concentration. On the roughed Si substrates, the Ru nanoparticles assist the etching even under oxygen-free and dark conditions.