Fabrication of Two-Dimensional Photonic Crystals on N-Type Silicon Substrate Using Holographic and Wet Etching Techniques

Technique of fabricating two-dimensional (2D) photonic crystals (PCs) in silicon wafers using the combination of holographic lithography and wet etching is described in the paper. The fabricated silicon material is suitable to be used as porous silicon for Ge/Si quantum dots growth or other applications. Single exposure holographic method was adopted to fabricate the photoresist mask with the pattern of 2D hexagonal lattice structure. HF:HNO₃:CH₃COOH = 4:4:3 solution was used to etch circular pores with bowl-shaped bottom into silicon substrate at room temperature with 30 s etching time. Periodic structure in silicon with 1 μm lattice constant and 200 nm pore depth was obtained in the experiment. The fabrication process is fast and cost-effective thus having the potential for industrial mass production of porous silicon.