Versatile bifunctional building block for in situ synthesis of sub-20 nm silver nanoparticle and selective copper deposition

In this work, a new bifunctional building block is presented for the development of versatile photosensitive resists, which enable in situ synthesis of sub-20 nm silver nanoparticles (AgNPs). In addition, practical adaptation to a palladium (Pd)-free electroless plating process verifies the facile fabrication of a metallic grid-based transparent conductive film. The building block is an aromatic small molecule with alpha,beta-unsaturated acryloyl group and para-hydroxyl group protected by an acid-labile group (i.e., Di-tert-dicarbonate (referred to as Boc anhydride)). Spectroscopy analysis verifies the ease of photopolymerization as well as deprotection of Boc from the para-hydroxyl group where plays a key role in Ag+ reduction. The studies on plasmon absorption, morphology and elemental analysis confirm that the in situ synthesized AgNPs are sub-20 nm with a uniform distribution in the polymer matrix, which is important for efficient catalytic performance in electroless copper (Cu) deposition. In addition, the photosensitive resist exhibited excellent process reliability with respect to photolithographic patterning process and electroless plating under strong alkaline solutions (pH 10-12). Finally, the present work demonstrates the successful fabrication of sub-3 mu m Cu metal grids on a polyethylene naphthalate (PEN) film.