Aligning Silicon Nanopillar Formed in Electroless HF/H2O2 Etching through Pre-Forming Porous Layer

For fabricating a controllable nanopillar array structure by utilizing the metal-assisted etching technique, we created a fine porous cladding layer on the surface of bulk silicon to settle down silver nanoparticles.

Prior to metal-assisted etching process, a 10nm thick porous silicon layer was produced on the surface of a p-type, 1-10 Ohm-cm, (100) bulk silicon by HF based electrochemically etching and then rinsed by D.I. water. After spin-drying, the specimen and a same silicon specimen but without the porous layer were dipped in a solution (HF / AgNO₃ / H₂O) for 30 seconds for the nucleation of silver nanoparticles. The dipped specimens were then etched by HF/ H₂O₂/ H₂O solution for forming nanopillar.

Through the observation of Field Emission Scanning Electronic Microscopy (FE-SEM), we found the pores on the surface of the porous layer could provide priority nucleation sites for silver nanoparticles. Hence, we could achieve a designed silicon nanopillar array by controlling the formation of the porous layer. After etching, the silicon specimen with the pre-forming porous layer exhibits different characteristic from the one without the layer as shown in figure.