Size reduction of electrolessly deposited copper features: Microcontact printing of catalysts on oriented polymers followed by thermal shrinkage

This paper describes a new method of reducing the size of the metal features made by electroless deposition, and a new method to fabricate complex shaped, patterned surfaces. Microcontact printing ({mu}CP) was used to pattern oriented glassy polymers with tetraoctadecylammonium bromide stabilized palladium colloids that serve as catalysts for the selective electroless deposition of copper. Annealing of the activated polymer at a temperature slightly above its glass transition temperature led to a shrinkage of the substrate. Immersion of the shrunken substrate in the plating bath yielded the metal features. The maximum shrinkage of the feature size achieved was in the order of a factor of {approximately}4 in one direction of the oriented polymer and of {approximately}7 in the perpendicular direction. Control of the extent and direction of shrinkage allowed the fabrication of metal features with sizes and shapes different from those on the PDMS stamp used for the patterning of the substrate and from the draw ratios. Free standing metal structures were produced by dissolving the substrate after the metal film had reached the desired thickness. Complex shaped, patterned surfaces could be fabricated by wrapping the activated polymer film around a scaffolding; during the annealing, the polymer adapted the shapemore » of the underlying scaffolding. Metallization of the activated, shaped substrate resulted in patterned three dimensional structures.« less