Pulsed Excimer Laser Photoablation by Backside Irradiation of Thin Metal Coated Polymer Films

Backside laser irradiation of metal coated quartz wafers can be used for transferring material imagewise to a target cleanly in absence of chemical vapors. However, the transfer of metal from a quartz surface requires a high energy, resulting in poor quality images in some cases. Use of a fluorinated polymer layer between the polycarbonate substrate and a Te-Se metal alloy is known for clean fabrication of metal holes in write-once-read-only memory media. Polymer thin films can be used similarly in backside laser irradiation for metal ejection from substrate surfaces. With an ArF excimer laser at 193 nm, gold and aluminum were ejected imagewise from Teflon AF, poly(methacrylonitrile) and quartz surfaces. The threshold fluences of 230 A thick gold films from polymer surfaces were 7.9 to 9.7 mJ/cm2, whereas the threshold fluence from a quartz surface was determined to be 17.8 mJ/cm2. For aluminum on top of quartz and aluminum coated polymers, higher threshold fluences were found compared to gold ranging from 12.96 to 22.7 mJ/cm2. Also, interfacial reactions between the polymer films and the metal layer occured and have been studied by SEM and XPS.