Ablation threshold measurements and surface modifications of 193 nm laser irradiated 4H-SiC

We report laser ablation experiments on polished 4H-SiC wafers using an 193 nm ArF laser over a fluence range of mJ cm⁻²–5000 mJ cm⁻². An onset of material modification was measured at a laser fluence of 925 ± 80 mJ cm⁻², and a concomitant etch rate of ∼200 pm per pulse. Laser ablation sites have been analysed using optical microscopy, scanning electron microscopy, Raman microscopy and white light interferometry. Finite element simulations using COMSOL™ Metaphysics, 5.3 have been used to calculate laser induced temperature rise of 4H-SiC as a function of laser fluence. The laser fluence required to reach the melting points of silicon, silicon carbide and carbon have been calculated and correspond to ∼970, 1950, 2600 mJ cm⁻² respectively. Two different surface modifications are observed. At a laser fluence in the region of 1.0 J cm⁻² the irradiated site removed material forming a uniform crater. At a higher laser fluence, in the region of 2700 mJ cm⁻², nodule-like structures form on the base of the ablation crater. The dissociation of laser irradiated 4H-SiC is briefly discussed.