Fabrication of Anodic Aluminum Oxide on Si and Sapphire Substrate

Abstract

We carried out anodic aluminum oxide (AAO) on a Si and a sapphire substrate. For anodic oxidation of Al two types of specimens prepared were Al(0.5 <TEX>$\mu\textrm{m}$</TEX>)!Si and Al(0.5 <TEX>$\mu\textrm{m}$</TEX>)/Ti(0.1 <TEX>$\mu\textrm{m}$</TEX>)<TEX>$SiO_2$</TEX>(0.1 <TEX>$\mu\textrm{m}$</TEX>)/GaN(2 <TEX>$\mu\textrm{m}$</TEX>)/Sapphire. Surface morphology of Al film was analyzed depending on the deposition methods such as sputtering, thermal evaporation, and electron beam evaporation. Without conventional electron lithography, we obtained ordered nano-pattern of porous alumina by in- situ process. Electropolishing of Al layer was carried out to improve the surface morphology and evaluated. Two step anodizing was adopted for ordered regular array of AAO formation. The applied electric voltage was 40 V and oxalic acid was used as an electrolyte. The reference electrode was graphite. Through the optimization of process parameters such as electrolyte concentration, temperature, and process time, a regular array of AAO was formed on Si and sapphire substrate. In case of Si substrate the diameter of pore and distance between pores was 50 and 100 nm, respectively. In case of sapphire substrate, the diameter of pore and distance between pores was 40 and 80 nm, respectively