Influence of pulsed Nd~(3+): YAG laser beam profile and wavelength on micro-scribing of copper and aluminum thin films

摘要

Evenly spaced conductive grids of copper and aluminum thin films on polyamide substrate are used for parabolic reflector-antennas, aboard telecommunications satellite. In the present paper, laser micro scribing of thin films using a flat-top and Gaussian laser beam profile are analyzed with 95% overlapping of the diameter of the laser spot. Laser scribing is performed using the Q-switched Nd~(3+): YAG (355, 532 nm) laser. The influence of laser irradiation and beam shape are experimentally analyzed using non-contact optical profilometer and scanning electron microscope (SEM). Laser scribing using flat-top profile produced near rectangular micro channels in copper thin films. Using Gaussian profile the probability of melting is greater than vaporization as observed using SEM images; this melt pool plays a prominent role in re-solidification at the edges. Depth of the scribe channel is observed to be 20% high for 532 nm wavelength compared to 355 nm wavelength. Effect of different environments such as air, water and vacuum on the channel depth and quality is reported. The response of aluminum and copper for high fluences is also studied. Theoretical modeling of the laser-material interaction using Comsol mulitphysics 4.4 is discussed.