No abstract

Metal-to-glass interfaces commonly encountered in electronics and surface finishing applications are prone to failure due to intrinsically weak interfacial adhesion. In the present work, an 'all-wet' process (utilizing solution-phase process steps) is developed for depositing nucleation-and adhesion-promoting layers that enhance the interfacial adhesion between glass substrates and electrochemically-deposited copper (Cu) films. Adhesion between thick (>10 μm) Cu films and the underlying glass substrates is facilitated by an interfacial Pd-TiO 2 layer deposited using solution-phase processes. Additionally, the proposed interfacial engineering utilizes self-assembled monolayers to functionalize the glass substrate, thereby improving surface wettability during Pd-TiO 2 deposition. Resulting Pd-TiO 2 deposits catalyze direct electroless plating of thin Cu seed layers, which enable subsequent electrodeposition of thick (>10 μm) Cu coatings. The present work provides a viable route for high-throughput, cost-effective metallization of glass and ceramic surfaces for electronics and surface finishing applications. The interfacial adhesion between metallic films and insulating substrates, e.g., glass, is intrinsically poor. This is a major roadblock in numerous electronics applications, particularly the manufacturing of printed circuit boards (PCBs) 1 and integrated circuits (ICs). 2,3Interfacial adhesion between metallic thin films deposited on glass substrates can be improved using functionalized polymers 4 or selfassembled monolayers (SAMs).2,5 SAMs provide interfacial 'anchoring' by chemically bonding to the substrate (SiO 2 ) as well as the deposited metal film. While SAMs have been shown to enable deposition of sub-micron scale, adherent Cu films on SiO 2 , 5 they do not provide adequate interfacial strength to enable thick (>10 μm) Cu coatings on glass. The Cu-to-SiO 2 interfacial adhesion may also be improved by utilizing metallic adhesion layers 6 or mixed-metal oxides. 7 Metallic adhesion promoters, e.g., titanium or titanium-nitride, are deposited using 'dry' methods such as physical vapor deposition (PVD). 'Dry' techniques are not desirable for high-volume manufacturing given their low throughput and high cost of ownership. On the other hand, mixed-metal oxides maybe deposited using sol-gel methods in which a metal alkoxide is co-deposited with a catalytic metal salt in a polarorganic solvent, resulting in a mixed-metal oxide adhesion layer with catalytic activity for electroless plating. 7 The methods by which the sol-gel catalyst may be deposited include dip-coating, printing, spincoating, or brushing.In the present work, we demonstrate an 'all-wet' process for depositing adhesion-promoting layers that enhance the interfacial adhesion between glass substrates and electroless-deposited copper (Cu) films. Adhesion between electrochemically-deposited thick (>10 μm) Cu coatings and the underlying glass substrates is facilitated by an interfacial Pd-TiO 2 layer fabricated using solution-phase processing. Our inte...