MORPHOLOGICAL-STUDIES OF LASER ETCHING PROCESSES IN SELF-SUSTAINED CVD DIAMOND WAFERS

This study reports the first results obtained by cutting/etching high quality synthesized diamond wafers of thicknesses up to 525 mum using a Nd:YAG laser. Energy pulses of 1-5 mJ, repetition rates of 100-50 000 Hz and pulse width of 250 ns have been used. The diamond wafers/films were synthesized by CVD of carbon from a diluted methane/freon gas mixture in hydrogen using a hot-filament reactor. It was found that the laser-material cutting/etching mechanisms involve first the graphitization of the grains and then oxidation in air. SEM microscopy was used to observe the surface morphology of the laser cuts revealing a columnar CVD grain growth which is very useful for heat dissipation elements in electro-optical devices. It was found that for deep grooves the cutting width is limited by the grain size of the polycrystalline wafers/films. High profile cutting aspect ratios of the order of 7-12 were obtained. Specific cutting energies employed were of the order of 200 kJ/g.