Understanding the influence of thermal annealing of the metal catalyst on the metal assisted chemical etching of silicon

Abstract

The metal-assisted chemical etching (MACE) is emerging as one of the cost-effective technique for anisotropic etching of silicon (Si) where the metal catalyst plays a key role in the etching process. Although intensive research has been carried out in this field, the effect of thermal annealing of the metal catalyst on MACE is not well understood. Therefore, a systematic study of the thermal annealing effect of the metal catalyst on the MACE of silicon (Si) in conjunction with gold (Au) micro stripes as a catalyst has been carried out in this work. We have demonstrated that the post-deposition thermal annealing of Au micro stripes has a direct relationship to the thickness of the metal catalyst for Si etching. The experimental results indicate that Si etching occurs when an annealed thick (140 nm) and wider (> 3 µm) Au micro stripe is applied as the metal catalyst. However, Si etching does not occur for an annealed thin (50 nm) and wider (> 3 µm) Au micro stripe is used as a metal catalyst. Furthermore, the direct effect of the oxidizing agent on the MACE Si etching by using annealed thick Au micro stripes has also been investigated. We show that a higher concentration of the oxidizing agent only polishes the Si surface with formation of craters in different locations of the Si. Here in this paper, the probable reasons for these results are also discussed.