Metal Ions’ Dynamic Effect on Metal-Assisted Catalyzed Etching of Silicon in Acid Solution

Metal-assisted catalyzed etching (MACE) technology is convenient and efficient for fabricating large-area silicon nanowires at room temperature. However, the mechanism requires further exploration, particularly the dynamic effect of various ions in the acid-etching solution. This paper investigated the MACE of silicon wafers predeposited with metal nanofilms in an HF-M(NO3)x-H2O etching solution (where M(NO3)x is the nitrate of the fourth-period elements of the periodic table). The oxidizing ability of Fe3+ and NO3− was demonstrated, and the dynamic influence of metal ions on the etching process was discussed. The results show that the MACE of silicon can be realized in various HF-M(NO3)x-H2O etching solutions, such as KNO3, Al(NO3)3, Cr(NO3)3, Mn(NO3)2, Ni(NO3)2, Co(NO3)2, HNO3, and Ca(NO3)2. It is confirmed that the concentration and type of cations in the etching solution affect the etching rate and morphology of silicon. Fe3+ and NO3− act as oxidants in catalytic etching. The fastest etching rate is about 5~6 μm/h in Ni(NO3)2, Co(NO3)2, and Ca(NO3)2 etching solutions. However, a high concentration of K+ hinders silicon etching. This study expands the application of MACE etching solution systems.