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

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.