Excimer laser etching of polyimide

Abstract

It is reported that thin films of polyimide are efficiently etched in air at pulsed excimer laser wavelengths of 248, 308, and 351 nm. Etch rate versus incident fluence data are found to obey a Beer–Lambert etching relation. Sharp laser fluence thresholds for significant etching are found to correlate with the wavelength-dependent absorption coefficient. The absorbed energy density required to initiate significant etching is found, within experimental error, to be independent of the wavelengths examined. It is felt that this information demonstrates the predominantly thermal nature of the laser etching mechanism. Additionally, infrared spectroscopy and coupled gas chromatography/mass spectroscopy were used to identify several gases evolved during pulsed laser etching of polyimide in both air and vacuum.

Laser ablation of polyimide at 308 nm: Characterization of ablation products.

“…These results are consistent with the works reported previously [26,27]. On the other hand, smaller species including CO, C02, and HCN were observed by means of infrared spectroscopy [20]. For the formation of the deposit observed here, some complicated processes such as transport of fragments and recombination products, adsorption, migration, and desorption would be involved.…”

“…The ionization fluence was '-100 mJ/cm2. [19,20] of the influence of ambient gas for the each depth of PI have been reported. The difference in the etch depths at the same fluence in the present study, which is comparable to that obtained for the ArF laser irradiation in He gas ambient [18], is greater than experimental errors.…”

“…This larger modification in air is due to the influence of ambient atmosphere. The contribution of the reaction similar to combustion followed by leaving incompletely combusted hydrocarbons [20] is suggested in air. Also; the contributions of redeposition and surface oxidation [9] are suggested.…”

ArF Excimer Laser Annealing of Polycrystalline Silicon Thin Film

“…Clean, precise ablation usually requires linear absorption coefficients of at least 10 4 cm -1 . Secondly, ablation occurs only after the material has absorbed a minimum energy per unit volume, i.e., the laser intensity must exceed a threshold value (Brannon et al, 1985).…”

Cu/Polyimide Multilayer Interconnections Fabricated by Nanoimprint at Every Lithography Process

“…Fine multilayer process Cu wiring is needed in top and bottom side layer of TSVs or TGVs. Cu/PI interconnections are generally fabricated by polyimide patterning, electroplating, and chemical mechanical polishing (CMP) [8][9][10][11]. Polyimide patterning is commonly carried out by laser process, photolithography using photo-sensitive polyimide, or pattern transfer by photolithography using standard photoresist and dry etching.…”