Via Hole Formation in Silicon Carbide by Laser Micromachining

A 248 nm (KrF) excimer laser with a repetition rate of 10 Hz, pulse duration of 30 ns and beam energy up to 450 mJ was employed to form vias in 4H-SiC substrates and Lely platelets. SEM micrographs have been used to evaluate etched material quality as well as etch rate. The area surrounding the via-holes is covered by nanoparticles, which are debris from the laser ablation and are removed by chemical cleaning and agitation. The etch-rate exhibits a perfect linear behaviour versus the number of laser pulses showing the possibility of an all-laser via-hole formation. A slight tapering along the via-holes, useful for the subsequent metallization process is also observed. Finally, a defective,15 μm wide, zone is formed nearby the sidewalls.