High-Speed Maskless Laser Patterning of Thin Films for Giant Microelectronics

Abstract

Maskless patterning of indium tin oxide (ITO) thin films was studied using a diode pumped Q-switched Nd:YLF laser. The wavelength was systematically varied from infrared to ultraviolet to investigate the effect of different conditions for light absorption by the ITO film and the glass substrate. Electrically isolating lines could be etched at all wavelengths used. However, residue-free removal of the ITO film could be achieved only when the glass substrate was strongly absorbing the incoming laser light. In all other cases, i.e., strong light absorption by the film only, weak absorption by the film and transmission by the substrate, or strong absorption by the film but weak absorption by the substrate, a ripple-like morphology in the etched groove was produced due to incomplete material removal. In case of ITO films on fused quartz substrates, therefore, the ripple-like morphology in the etched groove was observed at all wavelengths used. The results are consistent with thermal vaporization as the mechanism for the material removal which was confirmed by the predictions of numerical computations for the laser-induced temperature rise.