Microfabrication

Influence of pulsed Nd3+ : YAG laser beam profile and wavelength on microscribing of copper and aluminum thin films

[+] Author Affiliations
Srinagalakshmi Nammi, Nilesh J. Vasa

Indian Institute of Technology Madras, Department of Engineering Design, Chennai 600036, India

G. Balaganesan

Indian Institute of Technology Madras, Department of Mechanical Engineering, Chennai 600036, India

Sanjay Gupta, Anil C. Mathur

Indian Space Research Organization, Antenna Mechanical Design Division, Ahmedabad 380015, India

J. Micro/Nanolith. MEMS MOEMS. 14(4), 044503 (Oct 23, 2015). doi:10.1117/1.JMM.14.4.044503
History: Received June 9, 2015; Accepted September 25, 2015
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Abstract.  Evenly spaced conductive grids of copper and aluminum thin films on polyimide substrate are used for parabolic reflector antennas aboard telecommunications satellites. Laser microscribing of thin films using a flat-top and Gaussian laser beam profile is analyzed with 95% overlapping of the diameter of the laser spot. Laser scribing is performed using the Q-switched Nd3+:YAG (355, 532 nm) laser. The influence of laser irradiation and beam shape on the scribed microchannel width, depth, and surface characteristics is experimentally analyzed using a noncontact optical profilometer and scanning electron microscope (SEM). Laser scribing using a flat-top profile produced near rectangular microchannels in copper thin films. Using the Gaussian profile, the probability of melting is greater than vaporization as observed using SEM images; this melt pool plays a prominent role in resolidification at the edges. The depth of the scribe channel is observed to be 20% higher for the 532-nm wavelength compared to the 355-nm wavelength. The effect of different environments such as air, water, and vacuum on the channel depth and quality is reported. The response of aluminum and copper thin films for high fluences is also studied. Thermal modeling of the laser-material interaction has been attempted by assuming the plasma electron temperature as the laser ablation temperature for modeling the recession rate and depth for a single laser pulse. Model results agree with experimental data showing greater depth for 532 nm compared to 355 nm.

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© 2015 Society of Photo-Optical Instrumentation Engineers

Citation

Srinagalakshmi Nammi ; Nilesh J. Vasa ; G. Balaganesan ; Sanjay Gupta and Anil C. Mathur
"Influence of pulsed Nd3+ : YAG laser beam profile and wavelength on microscribing of copper and aluminum thin films", J. Micro/Nanolith. MEMS MOEMS. 14(4), 044503 (Oct 23, 2015). ; http://dx.doi.org/10.1117/1.JMM.14.4.044503


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