Influence of etching current density on the morphology of macroporous silicon arrays by photo-electrochemical etching

Macroporous silicon arrays (MSA) have attracted much attention for their potential applications in photonic crystals, silicon microchannel plates, MEMS devices and so on. In order to fabricate perfect MSA structure, photo-electrochemical (PEC) etching of MSA and the influence of etching current on the pore morphology were studied in detail. The current-voltage curve of a polished n-type silicon wafer was presented in aqueous HF using back-side illumination. The critical current density JPS was discussed and the basic condition of etching current density for steady MSA growth was proposed. An indirect method was presented to measure the relation of JPS at the pore tip and etching time. MSA growth was realized with the pore diameter constant by changing the etching current density according to the measuring result of JPS. MSA with 295 μm of depth and 98 of aspect ratio was obtained.