Microfeature Edge Quality Optimization in Excimer Laser Ablation of Metallic Film

Excimer laser ablation of thin films finds an advanced application in the manufacture of integrated circuits and it is desirable in the process that the size of the ablated region is close to the design and clean ablation takes place at the edges. In practice, the boundaries of the ablated region are irregular, the features are oversized and spattering is observed inside the ablated region. This work studies the edge roughness, channel width and boundary integrity as indicators of quality of ablation. Experiments are conducted with varying fluence, shot overlap and pitch (inter-channel distance) to generate different features. The edge roughness and channel width are found to have little dependence on spot overlap but are greatly influenced by the fluence. The overcut (channel width) is more at higher fluence but repetitive pulses do not affect the overcut. The range of parameters of ablation are identified from these experiments that lead to optimum edge roughness, channel width and boundary integrity.