Laser-direct photoetching of metal thin film for the electrode of transistor

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 105 and a very low off-current level. This indicates that the metallic layer is completely etched out by this process, making an additional cleaning or etching step unnecessary.