Structuring of polyimide-metal carbide layer systems by excimer laser ablation

Laser microlithography has been one of the most rapidly developing lithographic methods in the last years. The possibility of using thin metal carbide layers deposited on polyimide coated substrates has been investigated. The deposition conditions of thin polyimide (⩽1 μm) and carbide (40 nm) films for lithographic applications were determined. UV laser ablation of the metal carbide layers was performed at different wavelengths. Ablation threshold fluences are around 20–90 mJ/cm2. Clean ablation with high edge definition by one single laser pulse is achieved at about 40–200 mJ/cm2 leaving a smooth polyimide surface. At 248 nm ablation using two different pulse durations (32, 81 ns) was performed, but no significant differences could be found. Microstructures can be produced by ablation using mask imaging techniques. These results demonstrate the applicability of polyimide-metal carbide layer combinations as lithographic systems for a full dry process: laser-ablation-structuring of the carbide image layer and subsequent image transfer by reactive ion etching of the polyimide.