Laser ablation of silicon dioxide on silicon using femtosecond near infrared laser pulses

Applying ultrashort laser pulses at wavelengths of 0.8 μm and 1.03 μm, the selective ablation of thin (∼100 nm) SiO2 layers from silicon wafers has been investigated. In particular, the effects of different pulse durations down to a minimum value of 50 fs, and single– as well as multi-pulse irradiation have been studied. Selective removal of the dielectric layer without any visible damage of the opened Si wafer was only possible with single pulse ablation. The threshold fluence for such complete ablation of the dielectric layer increases with increasing pulse duration. Irradiating two or more pulses on the same spot, significantly corrupted ablation craters are produced. The physical ablation mechanisms will be discussed with respect to the observed dependences on the laser pulse duration as well as on the number of laser pulses per spot.