Structuring of polyimide by ArF excimer laser ablation
Contact and proximity ablation experiments on 1.1 mu m thick layers of Hitachi PIQ-13 polymide using chrome-on-quartz masks and ArF excimer laser radiation of 193 nm wavelength and fluence of 0.2 J cm-2 were performed in vacuum and air respectively. To examine the deposition behaviour of ablation residues, a constant nitrogen or oxygen gas stream at pressure of 3.5 bar corresponding to a flow rate of 0.5 l s-1 was directed through a proximity gap of about 5 mu m. In both cases an orientation of the ablation residues in the direction of the gas flow was observed. Thus ablation residues were minimised in exposed areas. Complete removal of ablation debris was achieved within 1.5 min in an ultrasonic bath. A structure resolution of approximately 0.3 mu m could be obtained.