Nanosecond time-resolved visualization of short pulse laser ablation processes for various laser beam profiles

Abstract

Thermal and fluid behavior are governing factors for the via processing of semiconducting substrates. In order to investigate the fundamentals, nanosecond (ns) time-resolved visualization of ns-pulse Nd:YAG laser ablation of SiC substrate has been performed for various conditions. Timeresolved visualizations have been conducted by using a ultra high speed camera with the frame rate of 200 million frames/second for the first time to reveal the ablation process in a single event with the temporal resolution of 5 ns. Both self-emitting light from the ablation plume and the shadow image due to the refractive index profile are visualized. The results show unique features for each spatial beam profiles (Gaussian, quasi-flat top, annular) with different beam energy. Combined with the previous experimental observations, the results help modeling the thermo-fluid numerical modeling of the ablation process. KEY WORDS: laser ablation, short pulse laser, time-resolved visualization, ultra high speed camera, laser beam profile, thermo-fluid modeling NOMENCLATURE E Pulse energy, J t Time, s 978-1-4799-5267-0/14/$31.00 ©2014 IEEE