Copper Plating on Through Glass Via（TGV）Using Both High-speed Sputtering Process and Wet Process

Abstract

Glass substrates with through-glass vias （TGVs） are being developed to improve large-volume and high-speed data communications technologies. To use the substrate as a circuit board, it is necessary to apply highly conductive Cu film on the glass substrate and to form uniform Cu film, even inside through holes. However, forming a uniform metal film on high-aspect-ratio through holes is difficult using conventional high-vacuum sputtering. Therefore, we specifically examined the throwing power of low-vacuum sputtering and formed a Cu film inside through holes of the TGV substrate using a wet plating process combined with sputtering. By selecting an appropriate Cu-plating solution and by optimizing Cu-plating conditions and plated film properties, annealing conditions, and an oxide film form method, we achieved 1.0 kN/m adhesion strength for a Cu film formed directly on a glass substrate. Results of our study also suggest the possibility of performing conformal plating on through holes having a 3.75 aspect ratio（0.3 mm glass thickness, φ80 μm opening diameter）.