Vertical Si nanowire with ultra-high-aspect-ratio by combined top-down processing technique

Vertical Si nanowires with ultra-high-aspect-ratio were fabricated using a combined process of deep reactive ion etching and sacrificial oxidation. The combined process starts with etching the Si substrates by the Bosch process to form micrometer-scale structures. The etched micrometer-scale structures are shrunk to nanometer-scale by sacrificial oxidation. The fabricated Si nanowires that were aligned vertically to the substrate had a diameter of less than 200 nm and a length greater than 10 μm. One of the fabricated Si nanowires had a diameter of 110 nm and a length of 11 μm. The resulting aspect-ratio reached 100, which is a value that is significantly high for vertical Si nanowires fabricated by using a top-down approach.