Analysis of the adhesion structure between the cycloolefin polymer and the copper seed layer formed using medium-vacuum sputtering
Akihiro Shimizu 1, 2, Kazuhiro Fukada 3, Shinichi Endo 1
1 Ushio Inc. (Japan)
2 Gifu University (Japan)
3 Shibaura Machine Co., Ltd. (Japan)
We focused on how two surface modification techniques—vacuum ultraviolet (VUV) irradiation and oxygen plasma treatment—affect the interfacial structure between a cycloolefin polymer (COP) film and a copper plating layer via a directly sputtered copper seed layer. Through scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and selected area electron diffraction, we confirmed that both surface modification treatments promote the formation of polycrystalline Cu2O at the interface. VUV irradiation smooths the COP surface and induces a uniform distribution of hydrophilic functional groups, resulting in the formation of a continuous Cu2O layer during annealing due to uniform copper oxidation. In contrast, oxygen plasma etches oxygen-affinitive regions, generating fine surface morphologies and concentrating functional groups within recessed areas. This leads to localized copper oxidation and the formation of Cu2O aggregates. Our findings reveal that surface morphology and functional group distribution—both governed by the surface treatment method—play a critical role in determining the microstructure of the interfacial Cu2O layer.
