Microdynamic behaviors of Au/Ni-assisted chemical etching in fabricating silicon nanostructures

In recent advancements, metal-assisted chemical etching has been recognized as a novel approach for fabricating semiconductor micro- and nano- structures. In this study, by using the ab initio molecular dynamics, the microdynamic behaviors of etchant molecules, silicon atoms, and metal nanoparticles during the etching process were disclosed and the simulation results were experimentally verified by etching silicon vias in different sizes with the assistance of gold and nickel nanoparticles. It is found that in the metal-assisted etching process, due to the strong electronegativity of the gold nanoparticles, the electrons of silicon atoms in contact with gold nanoparticles are attracted and transferred, thus these silicon atoms are easier to be oxidized and etched, therefore the size of the nano- structures fabricated by the gold-assisted chemical etching is comparable to that of the gold pattern; in addition to hole transfer, nickel atoms can diffuse into the silicon substrate to form a silicon- nickel compound, which destroys the superficial Si-Si bonds, thus making the etched region much larger than the nickel pattern. This study provides insights for revealing the micro-mechanism of etching semiconductor micro- and nano- structures.