Fabrication of microstructures using aluminum anodization techniques

A promising technique for the fabrication of high-aspect-ratio microstructures, presented by Tan el. al. at MEMS-95, takes advantage of the highly ordered pore structure of anodic metal oxides. In this work, we have extended and simplified this method. This process is capable of producing high-aspect-ratio microstructures oriented normal to a nonplanar substrate. Unlike the original process in which the aluminum substrate was anodized to the desired depth, masked and subsequently etched, the modified process involves performing the masking lithography prior to anodization. Patterned areas of an aluminum substrate are masked with a 0.6 μm layer of sputtered silicon dioxide. The SiO₂ layer prevents anodization in masked areas while the oxide grows in unmasked areas. In this paper, we present preliminary results using this local anodization process on aluminum substrates and discuss the use of the process for fabricating structures on nonplanar substrates.