Electroless silver plating on through-glass via (TGV) as an adhesive and conducting layer

The proposed method presents a scheme to modify the surface of the glass substrate using the piranha solution and to fabricate the conducting layer of the Through-glass Via (TGV) by the glucose-Ag electroless plating to achieve TGV metallization. The arithmetic mean deviation of the surface contours (Ra) for the substrates increases from 0.001 to 0.135. The contact angle of the substrates (unmodified and modified) is reduced to 6.4° and 12.2°, respectively. The sensitization process with SnCl₂ and the activation process with silver ammonia solution are conducted using the glucose as the reducing agent to prepare the silver seed layer covered in the TGV through-vias with a high aspect ratio (9:1). The adhesion between the metal coating and the surface is measured by the 3M tape and chemical mechanical polishing (CMP). The metal coating adheres well to the surface-modified substrate without peeling off, which can satisfy the demands for the electroplating and CMP processes.