Wavelength and pulse duration effects in laser scribing of thin films

We have studied the performance of six different types of laser systems for scribing of the polycrystalline thin-film PV materials: ZnO, SnO/sub 2/, CdTe, CIGS, Mo, and Si. The laser systems were KrF and XeCl excimer, copper vapor, quasi-cw Nd:YAG (both Q-switched and mode-locked), and flashlamp-pumped Nd:YAG. The wavelengths were 248, 308, 511 and 578, 532, and 1064 nm. Pulses included a 250 ns long train of 0.1 ns pulses (mode-locked) and single pulses from 8 ns and 250 ns. The excimer lasers (KrF and XeCl) were found to give high quality scribes for all materials, including the transparent oxides, ZnO:Al and SnO/sub 2/:F; however, vaporization rates were relatively low. Longer pulse durations (e.g., 90 ns) yielded higher rates of removal (up to 4 /spl mu/m per J/cm/sup 2/) for some materials. The high pulse energy available from the KrF laser allowed evaluation of beam delivery to a long narrow line which could eliminate the need for beam scanning and provide other advantages for scribing. We find that glass-side scribing, as opposed to film-side scribing, works well for Mo and CdTe films.