Laser direct writing of thin-film copper structures as a modification of lithographic processes

This paper presents a flexible, mask-free and efficient technique for UV-laser micro patterning of photosensitive resist by laser direct writing (LDW). Photo resist spun on gold sputtered silicon wafers has been laser structured by a scanner guided 266nm DPSSL and electroplated. Ablation behaviour and optimum seed layer preparation in relation to parameters like pulse energy, scanning speed and number of scanned cycles and the electroplating results are discussed. The resulting adhesive strength was measured by a P-sear device and the gold seed layer-plated copper interface investigated by SEM and EDX to explain correlation to identified bonding behaviour. Improved adhesive strength was observed with higher laser pulse energy and reduced number of cycle.