Effects of a low-pressure water jet assisting the laser etching of polycrystalline silicon

Laser micromachining has proven to be a useful tool for the precision processing of semiconductors. In the hybrid laser-water jet micromachining process investigated in this research, a laser is used for heating and softening the work material (polycrystalline silicon, in this case), while a water jet is employed for shearing the softened material and subsequently removing it due to the high-velocity of the liquid jet impingement, as well as for cooling the material. Specifically, the use of a low-pressure water jet to assist with the laser etching of polycrystalline silicon was investigated in this study. The energy efficiency of the processing as well as the width, depth, and surface microstructure of the groove etched in the polycrystalline silicon using the composite process were considered. With increasing jet velocity, the integrated energy initially decreased before increasing and the overall groove depth decreased, then increased, and finally decreased again. When the incidence angle was 30A degrees, the groove width in the polypolycrystalline silicon increased as the jet velocity increased from 8 and 28 m s(-1), and the use of a low-pressure jet to assist with the laser etching resulted in etched surfaces smoother than those obtained in air and hydrostatic conditions. The experimental results prove that the low-pressure water-jet-assisted laser etching technique can overcome the problems of micro-crack, slag, and recast layer formation that affect traditional laser etching and consequently improve the quality of machined parts.