Ablation and cutting of silicon wafer and micro-mold fabrication using femtosecond laser pulses

Femtosecond laser micromachining of silicon wafer at a relatively higher energy fluence level (>50 J/cm2) is investigated. Laser ablating spots and cutting kerfs are examined by means of charge coupled device camera and scanning electron microscopy. The area of ablated spots increases linearly with increasing the shot number from 1 to 16 and shows saturation with the shot number exceeding 16. Results also show that the area of ablated spots increases with increasing the pulse energy. The widths of cutting kerfs are nearly proportional to pulse energies, and are independent of feed speeds in our experiment. Based on the ablation and cutting, a micro-mold for microelectromechanical system application is fabricated with an accuracy of ∼1 μm at a pulse energy of 240 μJ and a feed speed of 300 μm/s in 6 min.