Electrochemical Copper Metallization of Glass Substrates Mediated by Solution-Phase Deposition of Adhesion-Promoting Layers

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...

Formation of Micrometer Scale Metal Structures on Glass by Selective Electroless Plating on Photopatterned Titanium and Copper Containing Films

“…Two examples have been the development of glass substrates for economic electronic device packaging (e.g., logic, memory, MEMS, sensor and RF devices) , and development of economical fine mesh structured metal films as a transparent electrode material with improved conductivity compared to the commonly used tin doped indium oxide. , In both examples, development of fabrication techniques has led to progress in the realization of their respective applications. Metal oxide layers have also served as adhesion layers for electrochemical metal deposition on glass and ceramic substrates − and glass/ceramic-metal hermetic seals. − …”

“…For the ZnO adhesive layer, photoefficiency would be low due to micrometer scale thickness and 1–2 μm dimension feature formation would be difficult due to the rough surface. The TiO 2 –Pd layer had been formed by a single coat and therefore could be adopted to photopatterning, however, the maximum adhesion strength reported has only reached 0.18 kN/m . In a similar concept, titanium oxide/copper films have been formed on glass by pyrolysis of a solution deposited 1-hydroxyphenylketone-titanium/copper complex (HPK-TiCu) film.…”

“…Unfortunately, evaluation of the thin plated film fails to yield a true determination of adhesion strength because adhesion has been shown to dramatically decrease upon film thickening by plating. 18 Adhesion of plating to glass has been demonstrated when SnO 2 , 5 ZnO, 6 and TiO 2 7 metal oxide adhesive layers were employed. Since the SnO 2 −Pd layer had been formed by repetition of the SnCl 2 sensitization and PdCl 2 activation steps, alignment complicates adoption to photopatterning.…”

“…The TiO 2 −Pd layer had been formed by a single coat and therefore could be adopted to photopatterning, however, the maximum adhesion strength reported has only reached 0.18 kN/m. 7 In a similar concept, titanium oxide/ copper films have been formed on glass by pyrolysis of a solution deposited 1-hydroxyphenylketone-titanium/copper complex (HPK-TiCu) film. Reduction of the copper in the film resulted in formation of a catalytic TiO 2 −Cu adhesion layer that had the capability to initiate the autocatalytic reaction for copper film deposition by electroless plating without Pd catalyst.…”

In Situ BSA (Bovine Serum Albumin) Assisted Electroless Plating Method with Superior Adhesion Property

“…[21] Therefore, for the purpose of increasing adhesion between metal layer and substrate, research on technologies/materials capable of embedding catalysts on the surface of substrates and activating them has been recently conducted. [22,23] Materials such as self-assembled monolayer (SAM), [24,25] polydopamine (PDM), [26] and bovine serum albumin (BSA) [27] are representative materials studied for this purpose. Chen et al immobilized Ni particles on the dielectric layer using aliphatic NH2-SAMs.…”