Effect of pulsing parameters on laser ablative cleaning of copper oxides

The characteristics of copper oxides removal are comparably investigated under different pulsing strategies. A two-dimensional model is utilized to numerically simulate the laser ablative cleaning process. In the model, property discontinuity and Stephan and kinetic boundary condition are taken into account, and the moving phase-interface in the material is evaluated with the enthalpy method. Experiments are carried out on copper samples having different oxide layer thickness. The copper oxide layer thickness determined by ellipsometer, and the chemical constituents of the copper oxide layer determined via X-ray photoelectron spectroscopy (XPS), are incorporated into this numerical model. Under the single-pulse irradiation strategy, a higher laser intensity threshold is determined by the model based on the criterion of removing the oxide film as much as possible without damaging the substrate. Under the multi-pulse irradiation strategy, a lower threshold is employed to remove the oxide layer while the appropriate pulse number under different laser intensity and different laser pulse repetition rate are the key issues investigated. Reasonable agreement is obtained between the experimental and simulated results.