Metal-assisted electroless etching of silicon in aqueous NH4HF2 solution

• Published in: Applied surface science 2012-05, Vol.258 (15), p.5628-5637
• Main Authors: Brahiti, Naima, Bouanik, Sihem-Aissiou, Hadjersi, Toufik
• Format: Article
• Language: English
• Subjects: Catalyst; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Metal-assisted electroless etching; Physics; Silicon nanostructures; Silicon nanowires
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.02.043

► A non-HF based solution was developed to elaborate different shapes of Si nanostructures by the metal-assisted chemical etching process. ► Metal-assisted electroless etching of silicon was investigated in new chemical solution containing NH4HF2. ► It was shown that silicon nanowires are fabricated either by one-step or two-step metal-assisted chemical etchings. ► It was shown that the increase of NH4HF2 in the etching solution leads to the increase of etching rate. One-step and two-step metal-assisted electroless chemical etchings of p-type silicon substrate in new solutions were investigated. In the one-step etching process, the etching is performed in NH4HF2/AgNO3 solution. On the other hand, the two-step etching process involves chemical deposition of noble metal onto silicon substrate surface followed by electroless etching in NH4HF2/H2O2 solution. The effect of several parameters on the morphology of etched layer was studied namely: pH of etching solution for the two cases and the etching temperature, the concentration of NH4HF2 and the type of metal deposited on silicon surface for second case. It is shown that the morphology depends strongly on etching parameters where different nanostructure shapes can be formed. An important result is that silicon nanowires are formed at pH=4 and pH≤2 for the first and second case, respectively.