Abstract
Previous literature regarding laser process inducing the decomposition of thin palladium acetate layer utilized toxic chloroform as the solvent. In this study, we chose acetone instead of toxic chloroform due to its high compatibility with palladium acetate and low boiling point. Therefore, an improved technique of second harmonic Q-switched Nd:YAG laser direct writing from solid film of palladium acetate/acetone on PI substrates was developed in this study. The results of UV-vis spectra and non-thermal light sources indicate that the decomposition mechanism of palladium acetate is dominated by pyrolytic process. Therefore, a critical criterion of this process is the dimension control by pyrolytic decomposition of the palladium acetate layer. Indeed, the poor lateral resolution can be improved by introducing an appropriate telescopic system into the optical design. Eventually, palladium pattern of 25μm in width has been fabricated. In addition, the result of x-ray photoelectron spectroscopy (XPS) revealthat pure Pd metal together with partial reduction of palladium acetate (Pdx) was both generated on the irradiated region after laser direct-writing. Copper lines of constant 280nm in thickness are achievable under different laser energies after electroless copper deposition for 10 minutes. The constant thickness implies that partial reduction of palladium acetate (Pdx) can be reduced to catalytic Pd metal in subsequent electroless copper bath. As for examining the quality of the deposited copper wires, energy dispersive x-ray spectroscopy (EDX) and two-point probe were employed to analyze the elemental composition and the resistivity of the deposited copper wires, respectively. The result of EDX demonstrates that the copper content could up to 95wt%. Moreover, the resistivity of copper wires can be as low as 2-5μΩ-cm.