Electrochemical micromachining of titanium using laser oxide film lithography: excimer laser irradiation of anodic oxide

Abstract

In electrochemical micromachining using oxide film laser lithography (OFLL), the pattern is formed by laser irradiation of an anodic oxide film. On the irradiated areas of the film the underlying metal is then selectively dissolved in an appropriate electrolyte, the non-irradiated oxide acting as a mask. The physical interactions of 308 nm XeCl excimer laser radiation with anodically formed oxide films on titanium were studied using single pulse irradiation at varying fluence and two different pulse durations. The irradiated surfaces were characterized by secondary electron microscopy (SEM), Auger electron spectroscopy (AES) profiling and X-ray-induced photoelectron spectroscopy (XPS), additionally, their electrochemical dissolution behaviour in an electropolishing electrolyte was evaluated. Numerical simulation was applied to the estimation of the temperature profiles at the surface of the irradiated samples. Results suggest that depending on irradiation conditions different mechanisms may be responsible for the loss of the protective properties of the oxide film. The creation of a Ti(O) solid solution resulting from diffusion of oxygen from the film into the underlying molten metal was shown to be effective at high fluences. The loss of protective properties observed at lower fluences was tentatively attributed to the creation of ionic defects in the oxide by a photolytic process.