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 ...
A procedure for formation of catalytic SiO substrate adhesive layer patterns and selective electrochemical metal deposition on the catalyst images was investigated. A photoreactive solution containing a diazonaphthoquinone sulfonate ester and Ti and Cu complexes was developed to deposit Cu catalyst-TiO adhesive layer latent images on glass. Sub-micrometer/micrometer scale positive tone photoactive TiCu complex film patterns were formed using a conventional photolithography technique. The Cu ions in 40-50 nm thick Ti and Cu oxide layers formed by pyrolysis of the TiCu complex films were reduced, residual Cu displaced with Pd then the porous Ti oxide structure filled and plated with Cu by selective electroless then electrolytic plating. Annealing the Cu plating filled TiO layers on glass resulted in formation of a smooth Ti/Cu oxide interface that enabled formation of 20 μm thick Cu deposits on glass substrate with up to 1 kN/m adhesion strength. The adhesion strength was attributed to chemical bonding of Ti and Cu oxides to the glass and Ti oxide to the Cu plating that was formed upon annealing the Cu filled TiO interlayer. Furthermore, a dip coating procedure was adapted that allowed copper film deposition on the entire surface of a 300 μm thick glass substrate with 50 μm in diameter holes enabling formation of electrically conductive through glass substrate interconnects.
A fully-additive fine pattern plating process is described for transparent conductive mesh formation on selectively UV-modified films by electroless copper plating. The reactions of surface modification were considered based on chemical and elemental analysis using X-ray photoelectron spectroscopy (XPS) and surface energy analysis. UVmodified surfaces were created with a polar protic moiety enriched surface that was roughened on the nanometer scale. Furthermore, amplified palladium adsorption selectivity at the modified regions and suppressed deposition on non-modified substrate regions enhanced the resolution. Copper mesh pattern formed on the palladium catalyst pattern achieved lower sheet resistance than indium tin-doped oxide (ITO) film of the same total light transmittance. After annealing the electrolytic plated film, the vertical peel strength between the PEN film and copper deposit was enhanced.
Cyclic olefin polymer (COP) has been applied as a high performance resin material in diverse fields. Ultraviolet (UV) modification treatment and an electroless plating method are effective for metallization on the COP surface. As described in this paper, vacuum UV (VUV, wavelength < 200 nm) exposure through a photomask was used for selective modification on the COP surface. Surface properties of the surface modification were evaluated using surface energy analysis and Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). VUV exposure was expected to cause polymer chain cleavage and to increase oxidized moieties. Some of the oxidatively cleaved material of lower molecular weight might then be extracted from the modified layer by alkaline treatment. Palladium (II)-amino acid complex as a catalyst for electroless plating was adsorbed selectively onto a VUV-modified layer of the COP surface. Consequently, the electroless plating reaction progressed on the modified area. Finally, the deposited metal patterns with line width of a few micrometers on the COP surface were formed through photomasking.
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