Direct copper metallization on TGV (Thru-Glass-Via) for high performance glass substrate

Abstract

Glass is widely used as a material for various devices such as various reflection mirrors, photomasks, magnetic disks, ITO glass substrates and the like. Recently, the advantages of high quality glass substrate material for high performance, next-generation electronic devices have been widely reported. Especially, the glass substrate provides a low dielectric loss at higher signal frequencies, high heat resistance and almost the same dimension stability as that for Si chip[1]-[7]. Conventionally, dry method such as sputtering is the mainstream method for forming a metal film on a glass surface. This study reports our novel metallization technology to obtain good adhesion without degrading glass properties and Cu conductivity. Metal circuit patterns were created without roughening the surface of glass substrate by wet plating process with subtractive process. The TGV glass surface was cleaned by irradiation of ultra-violet (UV) light and alkaline degreasing with complex agent. UV light and alkaline degreasing make the surface of the glass clean and the copper adhesion to glass improves with minimal stress to the glass itself. Conventional catalyzing treatment was performed after the surface cleaning, and electroless copper was deposited, followed by copper electroplating as a seed layer for the entire surface of the glass including front, back, and TGV sidewalls. We have successfully demonstrated direct copper plating on TGV with conformal plating for the substrate with better performance, including copper-glass adhesion of 0.42kN/m. Conformal copper seed layer was observed by X-ray computed tomography. This technology is further optimized for glass interposer with the capability of thick copper metallization directly on TGV glass for the first time in 300mm × 400mm × 0.1mm (thick) panel, aiming to reduce cost and achieve high throughput TGV metallization (Table 1). It suggests to us that glass will be a very promising material for next generation high-speed network.