Abstract

Laser-micromachining of steel and glass with laser pulses below 100 fs, and even as short as 5 fs, exhibit unreached ultimate processing precision. Recent experimental studies of dielectrics in the pulse duration domain τ ≥ 140 fs [1,2,3] and even down to 20 fs [4,5] and 5 fs [6] showed that impact (avalanche) and multiphoton ionization contribute to the ablation process. Heat affected zones reached in the pulse duration domaine between 5 and 100 fs are of the same order as have been observed with longer sub-picosecond pulses (e.g. 300 fs). However, multiphoton absorption at lowest pulse durations and maximum intensities, respectively, yield a maximum energy containment in the irradiated material. It is shown that this reduces the ablation depths below values achieved by conventional sub-picosecond pulse laser systems. This and a substantial decrease of the ablation threshold fluence in respect of pulse laser processing with pulses in the picosecond and nanosecond range opens a new field of ultraprecision dry etching in micro- and nanotechnology.

© 1998 IEEE