Fabrication of arrays of tapered silicon micro-/nano-pillars by metal-assisted chemical etching and anisotropic wet etching

• Published in: Nanotechnology 2018-07, Vol.29 (28), p.28LT01-28LT01
• Main Authors: Yamada, K, Yamada, M, Maki, H, Itoh, K M
• Format: Article
• Language: English
• Subjects: anisotropic wet etching; metal-assisted chemical etching; nanoimprint; silicon nanowire
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/aac04b

Fabrication of a 2D square lattice array of intentionally tapered micro-/nano-silicon pillars by metal-assisted chemical etching (MACE) of silicon wafers is reported. The pillars are square rod shaped with the cross-sections in the range 0.2 × 0.2-0.9 × 0.9 m2 and heights 3-7 m. The spacing between pillars in the 2D square lattice was controlled between 0.5 and 3.0 m. While the pillars after MACE had the high aspect ratio ∼1:5, subsequent anisotropic wet etching in potassium hydroxide solution led to 80°-89.5° tapers with smooth sidewalls. The resulting taper angle showed the relation with geometry of pillar structures; the spacing 0.5-3.0 m led to the tapering angle 89.5°-80° for 3 and 5 m tall pillars but 7 m tall pillars showed no dependency between the tapering angle and the inter-pillar spacing. Such an array of silicon tapered-rods with smooth sidewalls is expected to be applicable as a mold in nanoimprinting applications.