Micro Fabrication of Aluminum Oxide Patterns using Local Anodization

Abstract

In this study, the fabrication process of aluminum oxide pattern using local anodization was investigated. This process is known as local anodic oxidation (LAO) or scanning probe microscope (SPM) lithography for nano scale surface texturing [1]. However, an aluminum oxide formed by SPM anodization process has the ultimate thickness (the order of several tens of nm). Electrochemical machining (ECM), based on the electrochemical reactions between two electrodes, is a method for the machining of conductive materials. Micro ECM that uses ultra- short pulses allows localization of the electrochemical reaction to only a few micrometers of the surface due to the selective charging of a double layer. Therefore, using a principle of micro ECM, the aluminum oxide with micro scale depth can be localized. In the present study, mixtures of sulfuric/oxalic acid electrolyte was tested as feasible electrolytes for aluminum. Behavior of localized oxide growth was analyzed using by field emission scanning electron microscopy (FE-SEM) including energy dispersive spectroscopy (EDS) and it was confirmed that the number of micro-depth localized aluminum oxide was fabricated at specific location on aluminum surface. Depth and width of the anodized oxide line were investigated in different ratios of sulfuric and oxalic acid mixtures at various microsecond pulse duration and applied voltage condition. The insulation characteristics of fabricated aluminum oxide line were investigated and verified its possibility as an electric circuit. Subsequently, a coplanar waveguide (CPW) micro patch antenna was fabricated and characterized by a PNA network analyzer. The local anodization can be used for fabricating micro-electric circuits without masks and substrate

which will promise the next generation of micro electronic devices.