Organosiloxane Monolayers Terminated with Amine Groups as Adhesives for Si Metallization

Silicon (Si) on-chip metallization was carried out through surface functionalization and electroless deposition of copper (Cu). Surface functionalization of Si was performed by grafting an amine (NH2)-terminated organosilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (ETAS), as a nanoscaled bridge linker to adsorb catalytic polyvinylpyrrolidone-capped palladium nanoclusters (PVP-nPd) through complex reaction. The ETAS molecules bear three methoxy groups that can transform into the hydroxyl groups through hydrolysis and attach to the SiO2/Si substrate by hydrogen bonding. Through rapid thermal annealing (RTA) treatment, the dehydration reaction occurred and led to the formation of the covalent bonding of siloxane (Si-O-Si) between ETAS and SiO2/Si. The increase of the RTA temperature to 673 and 773 K caused the increase of the Si-O-Si bonding which improved the grafting orientation of ETAS as suggested by the molecular simulation. The adhesion strength of electrolessly deposited Cu film on SiO2/Si is boosted to 4 MPa (673 K) and 5.6 MPa (773 K) which is 60-124% enhancement compared to the sample without the RTA treatment (2.5 MPa). This shows its high feasibility induced by the organosilane nanolayer as molecular adhesive for next-generation Si metallization.