Copper Plating on Glass Using a Solution Processed Copper-Titanium Oxide Catalytic Adhesion Layer

Abstract

A method for copper deposition on glass and ceramics was investigated by direct plating on 20-30 nm thick copper inclusive titanium oxide films formed on the substrate surface. The copper inclusive titanium oxide film functioned as an adhesion layer and as a catalyst for autocatalytic copper deposition. Copper inclusive titanium oxide films were formed by pyrolysis of solution deposited 1-hydroxy phenyl ketone titanium-copper complex films. After deposition of electroless copper seed layers, 15-20 μm thick electrolytic copper films were formed, where upon thermal treatment up to 0.5 kN/m adhesion strength was attained on borosilicate glass. This process enabled electroless copper plating without the use of palladium as a catalyst on non-roughened smooth glass or ceramic substrate surfaces. The copper-titanium oxide adhesion layers were characterized and cross-sectional transmission electron microscopy illustrated the adhesion mechanism and catalyst structure. Despite poor thermal conductivity, due to properties such as transparency, smooth surface, chemical and thermal stability, coefficient of thermal resistance, dielectric constant, electrical insulation and physical strength, glass has gained attention an electronic substrate material.1-3 Two examples are in 2.5 D/3 D electronic device and RF module packaging. [4][5][6][7] In addition to these properties, abundance and availability in a wide range of shape and size make glass an attractive economic substitute for silicon in interposers. [4][5][6][7] Development of through substrate interconnect via hole formation technology for glass has progressed however, metallization technology relies on vacuum deposition, the silver mirror reaction or surface roughening followed by electroless plating for conductive seed layer formation. [8][9][10][11] Using sputtered Cu, Ti/Cu or Cr base layers, relatively high adhesion strength has been attained.12-14 However, dry processes have productivity limiting disadvantages such as size restriction, need for expensive equipment and high running cost. Therefore, economic wet methods have been studied as an alternative. In direct electroless plating methods, adhesion between the glass and the plated films has been accomplished by etching the glass surface with hydrofluoric acid, but with the sacrifice of its original transparency and smoothness. [15][16] Furthermore, employment of expensive palladium catalyst also introduces the need for a palladium removal procedure in order to prevent migration and short circuits that lead to poor device reliability. [17][18][19] Solution processed adhesion layers for direct electroless plating on glass have been demonstrated where a few tens of nanometer thick Pd-NiO, 20 Pd grafted TiO 2 , 21 or Pd-SnO 2 22 films served as catalytic anchor layers. Based on those results, the method outlined in Figure 1 for direct electroless copper plating on the substrate was investigated, where the catalytic anchor layer consisting of copper and titanium oxides was formed by pyrolysis of a metal complex film ...

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

“…Similar to the previously reported plating procedure, the TiCu-red layers from NBOC-TiCu (and DNQ-TiCu when the silane was not added) could be plated in the EDTA bath without the Pd displacement treatment. When silane was included in the film, either the PdCl 2 treatment or raising the bath temperature to 70 °C was necessary to initiate deposition.…”

“…Similar to the HPK-TiCu system, a layer composed of Ti and Cu oxides formed after pyrolysis of the TiCu complex film. After reduction of the oxide layer in the NaBH 4 solution, fine copper particles riddled the porous TiO 2 matrix structure in the oxide layer with larger agglomerated copper particles attached onto the layer surface.…”

“…In addition to development of a technique for direct sub-micrometer scale metal pattern deposition, an unprecedented level of copper plating adhesion to glass was realized, where smooth interfaces were maintained, and plated metal was not diffused into the glass surface. Since the prior reports, the mechanisms involved in the manifestation of the adhesion and functions of each thermal treatment in the process were clarified. , The same level of copper film adhesion was attained on quartz glass and SiO 2 surfaces as to borosilicate and aluminoborosilicate glass substrates, possibly because the adhesion did not rely on thermal diffusion of the plated metal into the glass surface.…”

“…Had dip-coating been applied, this technique should also prove effective for plating on substrates with complex surfaces like through glass via holes (TGV) for formation of through substrate interconnects. Metallization of TGV substrates is one of the fundamental processes in development of glass substrate electronic device packaging. , Furthermore, this plating method could be considered economic, as electroless copper plating could be accomplished without palladium . Therefore, photoreactive titanium and copper complex solutions were investigated for deposition of metallic patterns with high adhesion to glass surfaces.…”

“…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. − …”