Ultrasonic-assisted underwater laser micromachining of silicon

Underwater laser machining process can offer a clean cut with less thermal damage and material deposition on and nearby the cut region. However, the performance of this process is limited by the cut debris and bubble which can significantly disturb the laser beam during the ablation in water. In this study, the ultrasonic-assisted underwater laser ablation has been comprehensively examined to overcome the limitations of the existing process. The presented technique uses ultrasound to vibrate water while a workpiece is being ablated by a laser beam in water. This can atomize the bubble and energize the cut debris to be flushed away from the laser-ablated region. Silicon was selected as a work material in this study, where it was grooved by a nanosecond-pulse laser in water. The effects of ultrasonic parameters and water flow rate on the groove geometry and cut surface morphology were experimentally investigated and analyzed to understand the process performance. By using this technique, a clean and deep groove can be made on silicon wafer. The reactions between silicon-oxygen and silicon-carbon on the cut surface were also characterized and comparatively discussed with the other underwater laser ablation methods. According to the findings of this study, the ultrasonic-assisted underwater laser micromachining technique could be an alternative micromachining process to gain a higher material removal rate and a better cut surface quality than the other methods. (C) 2015 Elsevier B.V. All rights reserved.