Green laser sintering of copper oxide (CuO) nano particle (NP) film to form Cu conductive lines

Copper oxide (CuO) nanoparticle (NP) ink is a potential candidate for low-cost alternatives to other metal-based nano-particle inks (e.g., Au, Ag.) in printed electronics. To obtain Cu patterns from CuO NP ink, CuO NP inks should be converted to Cu particles, and be fused to form a connected conductive line. For this purpose, photonic sintering methods have been widely used, which generate the heat required for sintering via the absorption of light. In this study, we used continuous wave (CW) green laser with 532 nm wavelength, since the laser has the advantage of selective sintering by irradiation of light only on the target place. We investigated the optimal sintering parameters, such as laser power and scanning speed, using the green laser, in order to obtain low resistivity. We also investigated the pre-treatment conditions, such as pre-baking, which is required to evaporate solvents in the ink. We found that over-baking of deposited film will adversely affect the sintering, because film can be easily damaged from laser irradiation. As a result of laser sintering, we obtained the resistivity of (9.5 and 71.6) μΩ·cm when the pre-baked thicknesses of CuO films were (546 and 889) nm, respectively. In such cases, the thicknesses were significantly reduced to (141 and 270) nm, respectively.