Nicholas Marquez

Excimer laser ablation of Cr-contaminated polyimide

Excimer laser radiation at 193 and 248 nm has been used for the maskless and selective removal of chromium (Cr) contaminants present on polyimide surfaces with fine-line gold (Au) metallization features patterned on them. Excimer laser cleaning has been successful in restoring the dielectric performance of these polyimide surfaces. The differences in ablation thresholds and rates and the respective process windows, established at 193 and 248 nm, for the removal of Cr are discussed.

Excimer Laser Removal of Cr Contaminants from Polyimide Surfaces for Packaging Applications

Excimer laser radiation at 248 nm has been used for the maskless and selective removal of chromium (Cr) contamination from polyimide surfaces containing gold (Au) metallizations. Ablation thresholds and rates have been determined in air, vacuum, and oxygen. These results have been used to establish the optimum ablation medium and a corresponding process window that allows for selective removal of Cr from polyimide. The substantial differences between the ablated and unexposed regions of the polyimide surface have been established by electrical measurements, while the variations in their respective surface morphologies have been examined using optical and scanning electron microscopy. Quantitative determinations of Cr on the ablated and unablated regions of polyimide have been performed, using secondary ion mass spectrometry, to establish the threshold for the complete removal of Cr.