Circular and rectangular via holes formed in SiC via using ArF based UV excimer laser

Circular via holes with diameters of 10, 25, 50 and 70μm and rectangular via holes with dimensions of 10μm×100μm, 20μm×100μm and 30μm×100μm and drilled depths between 105 and 110μm were formed in 300μm thick bulk 4H-SiC substrates by Ar/F2 based UV laser drilling (λ=193nm) with a pulse width of ∼30ns and a pulse frequency of 100Hz. The drilling rate was linearly proportional to the fluence of the laser, however, the rate decreased for the larger via holes. The laser drilling produces much higher etch rates (229–870μm/min) than conventional dry etching (0.2–1.3μm/min) and the via entry can be tapered to facilitate subsequent metallization.