Polymer-Compatible Low-Temperature Plasma-Enhanced Chemical Vapor Deposition of Graphene on Electroplated Cu for Flexible Hybrid Electronics

Creators: Lu, Chen-Hsuan; Leu, Chyi-Ming; Yeh, Nai-Chang

Abstract

Flexible hybrid electronics and fan-out redistribution layers rely on electroplating Cu on polymers. In this work, direct low-temperature plasma-enhanced chemical vapor deposition (PECVD) of graphene on electroplated Cu over polyimide substrates is demonstrated, and the deposition of graphene is found to passivate and strengthen the electroplated Cu circuit. The effect of the H2/CH4 ratio on the PECVD graphene growth is also investigated, which is shown to affect not only the quality of graphene but also the durability of Cu. 100,000 cycles of folding with a bending radius of 2.5 mm and the corresponding resistance tests are carried out, revealing that Cu circuits covered by graphene grown with a higher H₂/CH₄ ratio can sustain many more bending cycles. Additionally, graphene coverage is shown to suppress the formation of copper oxides in ambient environment for at least 8 weeks after the PECVD process.

Additional Information

© 2021 The Authors. Published by American Chemical Society. Received: June 20, 2021; Accepted: August 4, 2021; Published: August 17, 2021. C.-H.L. acknowledges MMRC at Caltech for providing access to the AFM and XPS facilities and Professor George Rossman for providing access to the Raman spectrometer, and also thanks Dr. Wei-Hsiang Lin for useful discussion on the XPS measurements. The authors acknowledge Shi-Ri Lee at the Material and Chemical Research Laboratories (MCL) in ITRI for the STEM image acquisition and Chih-Chen Lin and Eric Tseng at ITRI for the folding test and resistance measurements. The authors also acknowledge the Electronic and Optoelectronic System Research Laboratories (EOSL) in ITRI for the electroplating Cu substrate preparation. The project was funded by the Industrial Technology Research Institute (ITRI) with award number NCY.PECVD2-ITRI.SRA2021. Author Contributions: The project was conceived jointly by C.-H.L., C.-M.L., and N.-C.Y. C.-H.L. carried out the PECVD graphene growth, Raman spectroscopic studies, XPS and AFM measurements, and analysis. C.-M.L. coordinated the research activities at ITRI and the collaboration with Caltech. N.-C.Y. coordinated and supervised the research activities at Caltech. All the authors contributed to the writing of the manuscript and have given approval to the final version of the manuscript. The authors declare no competing financial interest.

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