A high-repetition-rate femtosecond laser for thin silicon wafer dicing

Abstract

In this study, a high-power–high-repetition-rate femtosecond laser was investigated for singulation of silicon wafers. The femtosecond laser used for this investigation, unlike the previously used amplified system, is a compact unit that emits infrared ultrashort pulses at high repetition rates in the MHz range and an average output power of 11 W. A systematic study of the influence of the laser parameters on the kerf width, depth and quality of machining was carried out. A number of different experiments were performed using a silicon wafer of diameter 50 mm, P-type boron doped and back grinded to a 250 µm thickness wafer with orientation of ⟨1 0 0⟩. The experimental results show that the high-power–high-repetition-rate femtosecond laser can be a promising and competitive tool for thin wafer dicing. It is also the first time that the high-repetition-rate femtosecond laser has been demonstrated for real-world industrial applications for micromachining. A cutting speed of 40 mm s−1 with acceptable quality of sidewalls, depth of cut and kerf width was demonstrated during the experiment which can be considered when applying for industrial usage.