Electrochemical Micromachining of Patterned Aluminum Films by Porous-type Anodization

Abstract

Porous-type anodization of patterned Al films and subsequent chemical etching of porous Al2O3 is a sub-category of electrochemical micromachining. This method results in metallic pillars separated by micro-grooves, whose dimensions are defined by the design of anodization masks and a degree of anisotropy of porous-type anodization. The pillars have a trapezoidal shape with concave slopes due to undercutting, which results from the lateral pore growth under the anodization mask. Regardless of undercutting, porous-type anodization shows a higher degree of anisotropy than mostly isotropic wet chemical etching and allows for more accurate shape control of 3-D metallic microstructures. Being technologically advantageous to mostly isotropic wet chemical etching and offering a lower cost of ownership than plasma etching, porous-type anodization of patterned Al represents a compromise between these two methods. Thus, porous-type anodization may constitute an inexpensive and scalable to large geometric areas platform for micro-structuring of Al substrates.