A study on co-axial water-jet assisted fiber laser grooving of silicon

• Co-axial water-jet assisted fiber laser grooving of silicon has been demonstrated.
• Maximum ∼520 μm depths were produced by controlling processing parameters.
• Grooves are free from spatter, recast and micro-cracks, and are of good uniformity.
• Groove quality was better than that produced by argon-assisted laser grooving.

Potential of fiber laser grooving in silicon has been investigated with continuous wave beam and modulated beam of micro-second durations. Though silicon shows considerably high transparency for the utilized laser wavelength (1.07 μm), due to the increase of absorption coefficient with temperature its micro-machining is feasible with good precision by laser. A co-axial water-jet has been employed for ejecting out the molten silicon effectively and simultaneously for rapid cooling. This in turn, overcomes the limitation of micro-machining of silicon with laser pulses of relatively longer durations and alleviates the oxidation problem also. It has been observed that with increasing water-jet speed at constant laser parameters, spatter and recast are reduced. Grooves of controlled depth in 14–520 μm range, free from micro-cracks and thermal damage could be obtained by controlling the laser and process parameters. Compared to argon-jet assisted laser grooving this technique produced grooves of relatively better quality in terms of lesser micro-cracks, spatter and thermal damage.