A periodic array of silicon pillars fabricated by photoelectrochemical etching

A periodic array of silicon pillars was photoelectrochemically fabricated using the two-step etching process with a n-type Si (1 0 0) substrate. Two key factors, backside illumination and anodic bias, were required to obtain a high-aspect ratio macropore array of silicon. It was found that the initial pore could be separated into two different pores when the applied anodic bias was greater than a certain critical value. The pore size of the macroporous silicon with a high porosity was increased by anisotropic etching in an alkaline solution. Due to destruction of the pore sidewalls, KOH etching allowed for the fabrication of silicon pillars on a large-scale wafer with an improved uniformity. The anisotropic etching behavior of KOH solution led to necking of the silicon pillars when the etching time exceeded 60 s.