IWLPC (Wafer-Level Packaging) Conference Proceedings

Fabrication of Redistribution Structure Using Highly Reliable Photosensitive Polyimide for Fan Out Panel Level Packages

Authors: Hitoshi Araki, Yu Shoji, Yuki Masuda, Keika Hashimoto, Kazuyuki Matsumura, Yutaro Koyama, and Masao Tomikawa
Company: Electronic & Imaging Materials Research Laboratories, Toray Industries, Inc.
Date Published: 10/23/2018   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Positive tone photosensitive polyimide (posi-PSPI) having low temperature curability and extremely good Cu migration was developed. In order to develop, we investigated the effect of polyimide structure for reliability. We observed the polyimide structure affected the Cu migration resistance mainly. Polyimide having soft segment shows better Cu migration resistance. Soft segment unit in polyimide back-bone may add better flowability to cover Cu without any damage to show better Cu migration resistance. Posi-PSPI using the high reliable polyimide offers fine pattern (3 µm trench and 5 µm line and space) with good sensitivity (300 mJ/cm2 (i-line)) by photolithographic system, and shows high chemical resistance toward resist strippers.

We also successfully developed redistribution structure by using the above posi-PSPI and all wet Cu plating processes. To obtain the structure, patterned Cu was obtained by non-electrical plating on photosensitive polyimide layer with a mask of photo-resist. We coated the posi-PSPI by a slit coater and found a suitable wet surface treatment to obtain good adhesion to plated Cu. The all wet Cu processes are composed of wet activation process and electro-Cu plating process. By combining all these processes, 40µm line and space Cu pattern was obtained by using a 500-600mm glass panel. In addition 2µm line and space Cu pattern was obtained on a 8 inch glass wafer.

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