Patterning of Nanoporous Anodic Aluminum Oxide Arrays by Using Sol−Gel Processing, Photolithography, and Plasma Etching

Abstract

Patterned anodic aluminum oxide (AAO) arrays were fabricated by using sol−gel processing, photolithography, plasma etching, and two-step anodization. The fabrication process included the following general steps. First, a layer of aluminum was evaporated onto silicon wafers. Second, a silica layer was deposited by spin-coating a sol. Next, a patterned layer of a photoresist was deposited by standard photolithographic procedures. Subsequently, the pattern of photoresist was transferred to the underlying layer of silica by fluorocarbon plasma etching. Finally, AAO arrays were formed by the two-step anodization of exposed aluminum (e.g., not covered by silica). Deposition and etching of the silica layer were monitored by spectroscopic ellipsometry. Electrical measurements were performed to investigate the ability of the silica layer to act as a barrier that prevents anodization of aluminum. The structure of patterned AAO arrays was studied by scanning electron microscopy. A clear boundary was observed between...