Processing multilayer systems using femtosecond, picosecond, and nanosecond laser pulses at different wavelengths

Abstract

We performed ablation studies on multi-layer systems at different wavelength -pulse duration combinations. The multi-layer systems of interest, 150 nm thin indium tin oxide (ITO), 200 nm thin polyaniline (PANI) on 1 µm thick photo resist, and 280 nm PPV/pedot layer-combination on 150 nm thin ITO are optically transparent and used for a variety of industrial applications. One important goal of the study was to determine the possible process window for a complete removal of only the top layer, leaving the remaining layer basically unharmed. The investigations were conducted with the following wavelength -pulse duration combinations: 800 nm and 180 fs, 800 nm and 5 ps, 266 nm and 150 fs, 266 nm and 5 ns, 532 nm and 5 ns. We generated micro dots, lines and areas to determine the damage threshold, the processing quality and the processing speed for the specified application of selective layer removal. The structures were analyzed by means of optical and atomic force microscopy. In some cases, we observed a strong pulse duration dependence in the ablation threshold, an indication for the observed difficulties using laser pulses in the ns range. Comparative studies at different wavelengths demonstrate that laser pulses in the UV are not necessarily always a first choice to achieve a precise removal of the optically transparent top layer.

Fundamentals and advantages in ultrafast microstructuring of transparent materials

“…The successful selective laser-induced removal of thin transparent layers was reported recently. 24 Fig. 5 depicts an example of indium tin oxide (ITO) removed from the glass substrate using 3 ps laser pulses at a wavelength of 800 nm.…”

Heat accumulation effects in femtosecond laser ablation of ITO thin films for DEP trapping devices

“…Laser direct-write patterning of ITO thin films provides for a highly customizable and dynamic fabrication method that has been explored with various infrared, visible, and ultraviolet lasers by driving linear or nonlinear absorption processes [1,2,3]. Amongst these various laser types, femtosecond lasers are attractive for a large processing window, fast direct-writing time, strong nonlinear absorption in the ITO film, and low collateral or substrate damage [4,5]. Recently, heat accumulation effects have been demonstrated to lower the material damage threshold and reduce microcracking during high repetition rate femtosecond laser machining of transparent glasses [6,7].…”

”Dry-Etching System” with Q-switched DPSS Laser for Flat Panel Displays

“…Thus, there are many problems in the current etching process that relates to cost and environment issues. Laser-dry-etching method may replace the wet etching method because it has fewer processes, a low running cost, and creates low environmental pollution [1][2][3][4][5][6][7][8].…”

“…Recently, with the development of ultrafast laser oscillators, the selective removal of thin films became easier. The laser beam is suitable for removing thin films selectively from multi-layered film because thermal affections occur rarely around laser irradiation areas [4][5][6][7][8]. With this, the goal in researching laser-dry-etching method is to further improves it ability to remove film from multilayer film substrate.…”