New Excimer Laser-Based Dual Damascene Processes for High I/O Applications with Ultra-Fine Line Routing
In this paper a novel excimer laser dual damascene process is presented to generate a fine line multi-metal layer routing. A laser stepper technology together with a quartz mask allows a high throughput in combination of ultra-fine RDL and via openings below 5 µm. The depth of ablation into the polymer is controlled by the number of laser pulses and fluence. The patterning of RDL and Via is done in one excimer laser ablation step, with an aspect ratio of 1:1. A landing pad is not needed in the lines to allow via full contact because of the sub-micro meter overlay accuracy of the laser ablation system, which allows to realize a fine routing layer density. The vias and lines are metallized by a galvanic process. Test structures have been designed and fabricated by using low cure temperature PI, BCB, and ABF as dielectric material to demonstrate the material flexibility.