Ablation of CVD diamond with nanosecond laser pulses of UV-IR range

Etch rates of CVD diamond upon irradiation by nanosecond (5-9 ns) pulses at three different wavelengths 1078, 539 and 270 nm at laser fluences in the range 1-1000 J/cm(2) were measured. A Nd:YAP laser system operated at first, second and fourth harmonics was used in the ablation experiments. Both shallow (<15 microns) and through holes were etched in a 95-mu m thick free-standing diamond film grown by microwave plasma CVD. The ablation rate was found to be wavelength-independent, this result being ascribed to surface blackening caused by amorphization/graphitization as confirmed by Raman analysis. The maximum etch rate approached 600 nm/pulse. The etch rate depended on the crater depth, which was ascribed to the effect of laser-plasma interaction inside the deep channel. The possibility of cutting trenches of high aspect ratio has been demonstrated. In a separate experiment, a batch of thin diamond films differing in thermal conductivity (k=2-5 W/cmK) was ablated with a KrF excimer laser (lambda=248 nm). No dependence of ablation rate on film quality was observed, which could be explained assuming grain boundaries to be the main source of thermal resistance. (C) 1998 Elsevier Science S.A. All rights reserved.