Microcontact printing of palladium colloids: Micron-scale patterning by electroless deposition of copper

This paper describes a new method for forming micron- and submicron-scale patterns of copper on surfaces. This method uses microcontact printing (mu CP) to deposit colloids that serve as catalysts for the selective electroless deposition of copper. A patterned elastomeric stamp fabricated from poly-(dimethylsiloxane) was used to deliver the catalyst-palladium colloids stabilized with tetraalkylammonium bromides-to the substrate surface. The electroless deposition of the copper on the sample occurred only where palladium colloid was transferred to the substrate. Electroless deposition catalyzed by the colloids resulted in the formation of metal structures with features having submicron dimensions, with an edge resolution in the range of 100 nm. This technique of activating substrates for electroless metalization was successfully used to pattern glass, (Si/SiO2), and polymers; both flat and curved substrates were used. Microcontact printing of colloids was also used to fabricate metal structures whose thicknesses were varied in different regions of the sample (multilevel metal structures). Free-standing metal structures were produced by dissolving the substrate after the metal film had reached the desired thickness.