Abstract
Through-holes were formed by selective partial electropolishing in a 2.5 wt% HF electrolytic solution, using an N-type, (100)-oriented Si wafer as an anode, and a Pt plate as a cathode. The obtained holes were square through-holes of 5–35 µm side length, with an aspect ratio of 109. It was possible to form such through-holes with a density of 3,500 holes/mm2in specified areas. It was also confirmed that the pit of the square-based inverted pyramid structure could form deep capillaries. This suggests the possibility of forming microstructures such as pillars and tubes.