Excimer laser etching of Al metal films in chlorine environments

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Abstract
The etching of Al metal films on Si substrates in up to 1 Torr of Cl2 gas using the 308‐nm XeCl laser pulses is reported. Etch rates of up to ∼1 μm per pulse were obtained which were laser fluence independent in the range 3≳φ≳0.25 J/cm2. The etch rates decreased, however, at high Cl2 pressures and high laser repetition rate. Processes such as redeposition of the ablated material and slowing down of the ablation at increased Cl2 pressures are considered as possible explanations of the observed results. By subsequently exposing the film to Cl2 and then irradiating it under vacuum, we found that the main etching mechanism is reaction in the absence of light to form an aluminum chloride layer followed by the ablation of this layer with the subsequent laser pulse.