Selective activation and electroless plating of Cu on a polyimide substrate by using a pre-patterned inhibitor layer and plasma treatments

Micro-scale patterns of Cu were selectively electroless-deposited on a flexible polyimide (PI) substrate by using selective adsorption of Pd catalyst particles on a plasma-treated PI surface with a pre-patterned spin-on-glass (SOG) mask as an inhibitor layer. After patterning of the SOG inhibitor layer, we conducted O₂ plasma treatments to improve the adhesion between the electrolessly-plated Cu and PI surface, which was followed by a N ₂/H₂ plasma treatment to generate the amine (-NH ₂) functional groups that facilitated the adsorption of the Pd catalyst. While the pattern of the SOG inhibitor layer was effective in the formation of amine (-NH₂) functional groups, which inhibited the adsorption of Pd, the formation of amine functional groups on the PI surface allowed the Pd catalyst particles to form on the open area of the PI surface. The line and the space patterns of selective electroless plating of Cu, with a thickness of approximately 50 nm, could be formed.