Patterned electroless deposition of copper by microcontact printing palladium(II) complexes on titanium-covered surfaces

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The capability of microcontact printing (μCP) to transfer chemical reagents from an elastomeric stamp to a substrate is used here to direct electroless deposition of Cu. The stamp is inked with a Pd(II) catalytic precursor, which it prints onto a Ti-coated substrate. This application of μCP is challenged by several interdependent parameters such as the appropriate surface chemistry of the stamp, the choice of the ink, the control over the transfer of the catalyst during printing, the activation of the catalyst, and the electroless plating of Cu in general. We address these issues and suggest a reliable, but not general, method to combine microcontact printing and electroless deposition of Cu. This method uses hydrophilization of poly(dimethyl)-siloxane stamps and inking with the ethanol-soluble [(CH3-(CH2)16-CN)2PdCl2] catalytic precursor. Printing this complex onto a thin Ti layer evaporated onto Si/SiO2 provides a high-level transfer of the Pd(II) complex from the stamp to the surface with simultaneous activation and fixation of the catalyst by reduction of Pd(II) to Pd(0) before the electroless deposition of Cu. Fabrication of high-resolution and high-contrast patterns of Cu electroless deposited with this method is possible.