Effect of defocus distance on morphology of Gaussian distributed laser induced forward transfer Cu film and mechanism analysis

As a method of micro fabrication, laser induced forward transfer (LIFT) can be used to make microstructures. Presently, it has become a popular issue on microfabrication process. In this study, a Cu thin film is transferred from one quartz substrate to another quartz substrate by regulating the defocus distance of Gaussian distributed laser beam. The transferred Cu thin film is processed by optical microscope, scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analyzing. Relationship between defocus distance of the laser beam and size, morphology and uniformity of transferred Cu film is discussed. Moreover, mechanism of the morphology transition is analyzed based on the results. The results indicate that with the increase of defocus distance, the size of transferred Cu patterns increase firstly, then decrease, and disappear at last. Morphology of the transferred Cu patterns transforms from crater-shape to plane with many tiny Cu particles at the edge of the patterns. In addition, the transfer form of the thin film changes from liquid transfer to solid transfer.