Parallelized laser-direct patterning of nanocrystalline metal thin films by use of a pulsedlaser-induced thermo-elastic force

Abstract

Thin film patterning by the conventional lithographic technique requires a numberof steps including the deposition, development, and removal of the photoresistlayer. Here we demonstrate that metal thin films evaporated on glass can bedirectly patterned by a spatially modulated pulsed Nd-YAG laser beam (wavelength = 1064 nm,pulse width = 6 ns) incident from the backside of the substrate. This method utilizes a pulsed laser-inducedthermo-elastic force exerted on the film which plays a role in detaching it from thesubstrate. High-fidelity patterns at the micrometer scale have been fabricated over a fewsquare centimeters by a single pulse with pulse energy of 850 mJ. This is attributed to thefact that deposited metal films are polycrystalline with nano-sized grains, and thuslocalized etching of the material is possible with shearing along the weakly bonded grainboundary regions. We have also developed a nano-block model to simulate the laser-directpatterning of nanocrystalline thin films. Experimental results could be well describedwith this simulation model. The patterning process presented here provides asimple photoresist-free route to fabricate metal thin film patterns on transparentsubstrates.