Optimized chemical mechanical polishing of Parylene C for high-density wiring in flexible electronics

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With the rapid development of flexible electronics, an increasing number of microfabrication strategies originating from the Si-based integrated circuits field have been explored on organic materials. Parylene C, a polymer, has been widely used in the microelectromechanical systems field because of its outstanding fabrication merits, such as room-temperature processability, conformal coating, and precise thin film deposition capability with the thickness tunable from 1 nm to 100 μm. As a good dielectric material, the Parylene C is also suitable for interlayer dielectrics in flexible electronics. This study develops an optimized chemical mechanical polishing (CMP) technique of Parylene C for high-density redistribution wiring in high-performance flexible electronics. The roughness of the Parylene C surface after CMP was as low as 14.3 ± 1.5 Å. The problems of slurry pollution and mechanical failure of the Parylene film that degrade the dielectric performance of the Parylene C could be avoided by taking the optimized CMP method. The multi-material structure constructed by Parylene C, Silicon and electroplated Copper was prepared and polished using the optimized CMP process. Additionally, a flexible wiring sample has been successfully patterned by the Damascene process through the optimized CMP process. In this sample, both the distance between each wire and the wire width were as small as 5 μm. The optimized Parylene C CMP process is easy-to-realize, highly efficient, low cost, and with minor defects; it provides a promising way to achieve high-density interconnection in high-performance flexible electronic devices.