Laser-direct parallel patterning of metal thin films

Thin film patterning by the conventional lithographic technique requires a number of steps including the deposition, development, and removal of the photoresist layer. We report that metal thin films can be directly photoetched by a pulsed neodymium doped yttrium aluminum garnet laser beam irradiating the film surface. This process utilizes a laser-induced thermoelastic force, which plays a role to detach the film from the underlying layer. High-fidelity patterns at the micrometer scales have been fabricated using a spatially modulated laser beam. A zinc-tin-oxide thin film transistor with photoetched Al source and drain electrodes exhibited an on/off ratio higher than 10 ⁵ and a very low off-current level. This indicates that the channel area between electrodes was completely etched out, making any additional cleaning or etching steps unnecessary. We also demonstrate that transparent thin films such as ITO can be patterned using a metal thin film as a dynamic release layer.